Method of treating emissions of a hybrid vehicle with a hydrocarbon absorber and a catalyst bypass system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roos, Bryan Nathaniel; Gonze, Eugene V; Santoso, Halim G

A method of treating emissions from an internal combustion engine of a hybrid vehicle includes directing a flow of air created by the internal combustion engine when the internal combustion engine is spinning but not being fueled through a hydrocarbon absorber to collect hydrocarbons within the flow of air. When the hydrocarbon absorber is full and unable to collect additional hydrocarbons, the flow of air is directed through an electrically heated catalyst to treat the flow of air and remove the hydrocarbons. When the hydrocarbon absorber is not full and able to collect additional hydrocarbons, the flow of air ismore » directed through a bypass path that bypasses the electrically heated catalyst to conserve the thermal energy stored within the electrically heated catalyst.« less

Heat Exchange, Additive Manufacturing, and Neutron Imaging

ScienceCinema

Geoghegan, Patrick

2018-01-16

Researchers at the Oak Ridge National Laboratory have captured undistorted snapshots of refrigerants flowing through small heat exchangers, helping them to better understand heat transfer in heating, cooling and ventilation systems.

Characteristics of turbulence transport for momentum and heat in particle-laden turbulent vertical channel flows

NASA Astrophysics Data System (ADS)

Liu, Caixi; Tang, Shuai; Shen, Lian; Dong, Yuhong

2017-10-01

The dynamic and thermal performance of particle-laden turbulent flow is investigated via direction numerical simulation combined with the Lagrangian point-particle tracking under the condition of two-way coupling, with a focus on the contributions of particle feedback effect to momentum and heat transfer of turbulence. We take into account the effects of particles on flow drag and Nusselt number and explore the possibility of drag reduction in conjunction with heat transfer enhancement in particle-laden turbulent flows. The effects of particles on momentum and heat transfer are analyzed, and the possibility of drag reduction in conjunction with heat transfer enhancement for the prototypical case of particle-laden turbulent channel flows is addressed. We present results of turbulence modification and heat transfer in turbulent particle-laden channel flow, which shows the heat transfer reduction when large inertial particles with low specific heat capacity are added to the flow. However, we also found an enhancement of the heat transfer and a small reduction of the flow drag when particles with high specific heat capacity are involved. The present results show that particles, which are active agents, interact not only with the velocity field, but also the temperature field and can cause a dissimilarity in momentum and heat transport. This demonstrates that the possibility to increase heat transfer and suppress friction drag can be achieved with addition of particles with different thermal properties.

Evolution of solidification texture during additive manufacturing.

PubMed

Wei, H L; Mazumder, J; DebRoy, T

2015-11-10

Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.

Analytical skin friction and heat transfer formula for compressible internal flows

NASA Technical Reports Server (NTRS)

Dechant, Lawrence J.; Tattar, Marc J.

1994-01-01

An analytic, closed-form friction formula for turbulent, internal, compressible, fully developed flow was derived by extending the incompressible law-of-the-wall relation to compressible cases. The model is capable of analyzing heat transfer as a function of constant surface temperatures and surface roughness as well as analyzing adiabatic conditions. The formula reduces to Prandtl's law of friction for adiabatic, smooth, axisymmetric flow. In addition, the formula reduces to the Colebrook equation for incompressible, adiabatic, axisymmetric flow with various roughnesses. Comparisons with available experiments show that the model averages roughly 12.5 percent error for adiabatic flow and 18.5 percent error for flow involving heat transfer.

Fundamental mechanisms that influence the estimate of heat transfer to gas turbine blades

NASA Technical Reports Server (NTRS)

Graham, R. W.

1979-01-01

Estimates of the heat transfer from the gas to stationary (vanes) or rotating blades poses a major uncertainty due to the complexity of the heat transfer processes. The gas flow through these blade rows is three dimensional with complex secondary viscous flow patterns that interact with the endwalls and blade surfaces. In addition, upstream disturbances, stagnation flow, curvature effects, and flow acceleration complicate the thermal transport mechanisms in the boundary layers. Some of these fundamental heat transfer effects are discussed. The chief purpose of the discussion is to acquaint those in the heat transfer community, not directly involved in gas turbines, of the seriousness of the problem and to recommend some basic research that would improve the capability for predicting gas-side heat transfer on turbine blades and vanes.

Lunar ash flow with heat transfer.

NASA Technical Reports Server (NTRS)

Pai, S. I.; Hsieh, T.; O'Keefe, J. A.

1972-01-01

The most important heat-transfer process in the ash flow under consideration is heat convection. Besides the four important nondimensional parameters of isothermal ash flow (Pai et al., 1972), we have three additional important nondimensional parameters: the ratio of the specific heat of the gas, the ratio of the specific heat of the solid particles to that of gas, and the Prandtl number. We reexamine the one dimensional steady ash flow discussed by Pai et al. (1972) by including the effects of heat transfer. Numerical results for the pressure, temperature, density of the gas, velocities of gas and solid particles, and volume fraction of solid particles as function of altitude for various values of the Jeffreys number, initial velocity ratio, and two different gas species (steam and hydrogen) are presented.

Characterization of Single Phase and Two Phase Heat and Momentum Transport in a Spiraling Radial Inow Microchannel Heat Sink

NASA Astrophysics Data System (ADS)

Ruiz, Maritza

Thermal management of systems under high heat fluxes on the order of hundreds of W/cm2 is important for the safety, performance and lifetime of devices, with innovative cooling technologies leading to improved performance of electronics or concentrating solar photovoltaics. A novel, spiraling radial inflow microchannel heat sink for high flux cooling applications, using a single phase or vaporizing coolant, has demonstrated enhanced heat transfer capabilities. The design of the heat sink provides an inward swirl flow between parallel, coaxial disks that form a microchannel of 1 cm radius and 300 micron channel height with a single inlet and a single outlet. The channel is heated on one side through a conducting copper surface, and is essentially adiabatic on the opposite side to simulate a heat sink scenario for electronics or concentrated photovoltaics cooling. Experimental results on the heat transfer and pressure drop characteristics in the heat sink, using single phase water as a working fluid, revealed heat transfer enhancements due to flow acceleration and induced secondary flows when compared to unidirectional laminar fully developed flow between parallel plates. Additionally, thermal gradients on the surface are small relative to the bulk fluid temperature gain, a beneficial feature for high heat flux cooling applications. Heat flux levels of 113 W/cm2 at a surface temperature of 77 deg C were reached with a ratio of pumping power to heat rate of 0.03%. Analytical models on single phase flow are used to explore the parametric trends of the flow rate and passage geometry on the streamlines and pressure drop through the device. Flow boiling heat transfer and pressure drop characteristics were obtained for this heat sink using water at near atmospheric pressure as the working fluid for inlet subcooling levels ranging from 20 to 80 deg C and mean mass flux levels ranging from 184-716 kg/m. 2s. Flow enhancements similar to singlephase flow were expected, as well as enhancements due to increased buoyant forces on vapor bubbles resulting from centripetal acceleration in the flow which will tend to draw the vapor towards the outlet. This can also aid in the reduction of vapor obstruction of the flow. The flow was identified as transitioning through three regimes as the heat rate was increased: partial subcooled flow boiling, oscillating boiling and fully developed flow boiling. During partial subcooled flow boiling, both forced convective and nucleate boiling effects are important. During oscillating boiling, the system fluctuated between partial subcooled flow boiling and fully developed nucleate boiling. Temperature and pressure oscillations were significant in this regime and are likely due to bubble constriction of flow in the microchannel. This regime of boiling is generally undesirable due to the large oscillations in temperatures and pressure and design constraints should be established to avoid large oscillations from occurring. During fully developed flow boiling, water vapor rapidly leaves the surface and the flow does not sustain large oscillations. Reducing inlet subcooling levels was found to reduce the magnitude of oscillations in the oscillating boiling regime. Additionally, reduced inlet subcooling levels reduced the average surface temperature at the highest heat flux levels tested when heat transfer was dominated by nucleate boiling, yet increased the average surface temperatures at low heat flux levels when heat transfer was dominated by forced convection. Experiments demonstrated heat fluxes up to 301 W/cm. 2at an average surface temperature of 134 deg C under partial subcooled flow boiling conditions. At this peak heat flux, the system required a pumping power to heat rate ratio of 0.01%. This heat flux is 2.4 times the typical values for critical heat flux in pool boiling under similar conditions.

Evolution of solidification texture during additive manufacturing

PubMed Central

Wei, H. L.; Mazumder, J.; DebRoy, T.

2015-01-01

Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components. PMID:26553246

Evolution of solidification texture during additive manufacturing

DOE PAGES

Wei, H. L.; Mazumder, J.; DebRoy, T.

2015-11-10

Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Furthermore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numericalmore » modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.« less

An extended supersonic combustion model for the dynamic analysis of hypersonic vehicles

NASA Technical Reports Server (NTRS)

Bossard, J. A.; Peck, R. E.; Schmidt, D. K.

1993-01-01

The development of an advanced dynamic model for aeroelastic hypersonic vehicles powered by air breathing engines requires an adequate engine model. This report provides a discussion of some of the more important features of supersonic combustion and their relevance to the analysis and design of supersonic ramjet engines. Of particular interest are those aspects of combustion that impact the control of the process. Furthermore, the report summarizes efforts to enhance the aeropropulsive/aeroelastic dynamic model developed at the Aerospace Research Center of Arizona State University by focusing on combustion and improved modeling of this flow. The expanded supersonic combustor model described here has the capability to model the effects of friction, area change, and mass addition, in addition to the heat addition process. A comparison is made of the results from four cases: (1) heat addition only; (2) heat addition plus friction; (3) heat addition, friction, and area reduction, and (4) heat addition, friction, area reduction, and mass addition. The relative impact of these effects on the Mach number, static temperature, and static pressure distributions within the combustor are then shown. Finally, the effects of frozen versus equilibrium flow conditions within the exhaust plume is discussed.

Corrosion and Heat Transfer Characteristics of Water Dispersed with Carboxylate Additives and Multi Walled Carbon Nano Tubes

NASA Astrophysics Data System (ADS)

Moorthy, Chellapilla V. K. N. S. N.; Srinivas, Vadapalli

2016-10-01

This paper summarizes a recent work on anti-corrosive properties and enhanced heat transfer properties of carboxylated water based nanofluids. Water mixed with sebacic acid as carboxylate additive found to be resistant to corrosion and suitable for automotive environment. The carboxylated water is dispersed with very low mass concentration of carbon nano tubes at 0.025, 0.05 and 0.1 %. The stability of nanofluids in terms of zeta potential is found to be good with carboxylated water compared to normal water. The heat transfer performance of nanofluids is carried out on an air cooled heat exchanger similar to an automotive radiator with incoming air velocities across radiator at 5, 10 and 15 m/s. The flow Reynolds number of water is in the range of 2500-6000 indicating developing flow regime. The corrosion resistance of nanofluids is found to be good indicating its suitability to automotive environment. There is a slight increase in viscosity and marginal decrease in the specific heat of nanofluids with addition of carboxylate as well as CNTs. Significant improvement is observed in the thermal conductivity of nanofluids dispersed with CNTs. During heat transfer experimentation, the inside heat transfer coefficient and overall heat transfer coefficient has also improved markedly. It is also found that the velocity of air and flow rate of coolant plays an important role in enhancement of the heat transfer coefficient and overall heat transfer coefficient.

Segmented heat exchanger

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron

2010-12-14

A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least amore » portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.« less

Computer code for predicting coolant flow and heat transfer in turbomachinery

NASA Technical Reports Server (NTRS)

Meitner, Peter L.

1990-01-01

A computer code was developed to analyze any turbomachinery coolant flow path geometry that consist of a single flow passage with a unique inlet and exit. Flow can be bled off for tip-cap impingement cooling, and a flow bypass can be specified in which coolant flow is taken off at one point in the flow channel and reintroduced at a point farther downstream in the same channel. The user may either choose the coolant flow rate or let the program determine the flow rate from specified inlet and exit conditions. The computer code integrates the 1-D momentum and energy equations along a defined flow path and calculates the coolant's flow rate, temperature, pressure, and velocity and the heat transfer coefficients along the passage. The equations account for area change, mass addition or subtraction, pumping, friction, and heat transfer.

An experimental study of heat transfer and film cooling on low aspect ratio turbine nozzles

NASA Astrophysics Data System (ADS)

Takeishi, K.; Matsuura, M.; Aoki, S.; Sato, T.

1989-06-01

The effects of the three-dimensional flow field on the heat transfer and the film cooling on the endwall, suction and pressure surface of an airfoil were studied using a low speed, fully annular, low aspect h/c = 0.5 vane cascade. The predominant effects that the horseshoe vortex, secondary flow, and nozzle wake increases in the heat transfer and decreases in the film cooling on the suction vane surface and the endwall were clearly demonstrated. In addition, it was demonstrated that secondary flow has little effect on the pressure surface. Pertinent flow visualization of the flow passage was also carried out for better understanding of these complex phenomena. Heat transfer and film cooling on the fully annular vane passage surface is discussed.

Physiological Responses to Acute Exercise-Heat Stress

DTIC Science & Technology

1988-01-01

muscle contraction and to dissipate the associated heat release. In hot environments, the core to skin temperature gradient is reduced to skin blood flow needs to be relatively high (compared to cooler environments) to achieve heat transfer sufficient for thermal balance. In addition, sweat secretion can result in a reduced plasma (by dehydration) and thus blood volume. Both high skin blood flow and reduced plasma volume can reduce

Advective and Conductive Heat Flow Budget Across the Wagner Basin, Northern Gulf of California

NASA Astrophysics Data System (ADS)

Neumann, F.; Negrete-Aranda, R.; Contreras, J.; Müller, C.; Hutnak, M.; Gonzalez-Fernandez, A.; Harris, R. N.; Sclater, J. G.

2015-12-01

In May 2015, we conducted a cruise across the northern Gulf of California, an area of continental rift basin formation and rapid deposition of sediments. The cruise was undertaken aboard the R/V Alpha Helix; our goal was to study variation in superficial conductive heat flow, lateral changes in the shallow thermal conductivity structure, and advective transport of heat across the Wagner basin. We used a Fielax heat flow probe with 22 thermistors that can penetrate up to 6 m into the sediment cover. The resulting data set includes 53 new heat flow measurements collected along three profiles. The longest profile (42 km) contains 30 measurements spaced 1-2 km apart. The western part of the Wagner basin (hanging wall block) exhibit low to normal conductive heat flow whereas the eastern part of the basin (foot wall block) heat flow is high to very high (up to 2500 mWm-2). Two other short profiles (12 km long each) focused on resolving an extremely high heat flow anomaly up to 15 Wm-2 located near the intersection between the Wagner bounding fault system and the Cerro Prieto fault. We hypothesize that the contrasting heat flow values observed across the Wagner basin are due to horizontal water circulation through sand layers and fault pathways of high permeability. Circulation appears to be from west (recharge zone) to east (discharge zone). Additionally, our results reveal strong vertical advection of heat due to dehydration reactions and compaction of fine grained sediments.

In-situ shear stress indicator using heated strain gages at the flow boundary

NASA Astrophysics Data System (ADS)

Yeh, Chi-An; Yang, Fuling

2011-11-01

This work borrows the concept of hot-wire anemometry and sketch a technique that uses local heat transfer to infer the flow field and the corresponding stress. Conventional strain gages were mounted at the flow solid boundary as the heat source and acrylic boundary was chosen for its low thermal conductivity ensuring heat accumulation when a gage is energized. The gage would now work in slightly overheated state and its self-heating leads to an additional thermal strain. When exposed to a flow field, heat is brought away by local forced convection, resulting in deviations in gage signal from that developed in quiescent liquid. We have developed a facility to achieve synchronous gage measurements at different locations on a solid boundary. Three steady flow motions were considered: circular Couette flow, rectilinear uniform flow, and rectilinear oscillating flow. Preliminary tests show the gage reading does respond to the imposed flow through thermal effects and greater deviation was measured in flows of higher shear strain rates. The correlation between the gage signals and the imposed flow field is further examined by theoretical analysis. We also introduced a second solid boundary to the vicinity of the gage in the two rectilinear flows. The gage readings demonstrate rises in its magnitudes indicating wall amplification effect on the local shear strain, agreeing to the drag augmentation by a second solid boundary reported in many multiphase flow literatures.

Investigation of Hot Streak Migration and Film Cooling Effects on the Heat Transfer in Rotor/Stator Interacting Flows.

DTIC Science & Technology

1991-07-15

Study of Endwall and Airfoil Surface Heat Transfer in a Large Scale Turbine Blade Cascade," Journal of Engineering for Power, Vol. 102, No. 2, April...the turbine passage and along the surface of where d6 is the distance from the blade surface to a given node, the airfoil . In addition, a specified...effects on the passage flow and blade surface heat transfer for an axial flow turbine stage. These objectives are part of an overall plan to extend the

Laminar Heating Validation of the OVERFLOW Code

NASA Technical Reports Server (NTRS)

Lillard, Randolph P.; Dries, Kevin M.

2005-01-01

OVERFLOW, a structured finite difference code, was applied to the solution of hypersonic laminar flow over several configurations assuming perfect gas chemistry. By testing OVERFLOW's capabilities over several configurations encompassing a variety of flow physics a validated laminar heating was produced. Configurations tested were a flat plate at 0 degrees incidence, a sphere, a compression ramp, and the X-38 re-entry vehicle. This variety of test cases shows the ability of the code to predict boundary layer flow, stagnation heating, laminar separation with re-attachment heating, and complex flow over a three-dimensional body. In addition, grid resolutions studies were done to give recommendations for the correct number of off-body points to be applied to generic problems and for wall-spacing values to capture heat transfer and skin friction. Numerical results show good comparison to the test data for all the configurations.

Pneumatic Proboscis Heat-Flow Probe

NASA Technical Reports Server (NTRS)

Zacny, Kris; Hedlund, Magnus; Mumm, Eric; Shasho, Jeffrey; Chu, Philip; Kumar, Nishant

2013-01-01

Heat flow is a fundamental property of a planet, and provides significant constraints on the abundance of radiogenic isotopes, the thermal evolution and differentiation history, and the mechanical properties of the lithosphere. Heat-flow measurements are also essential in achieving at least four of the goals set out by the National Research Council for future lunar exploration. The heat-flow probe therefore directly addresses the goal of the Lunar Geophysical Network, which is to understand the interior structure and composition of the Moon. A key challenge for heat flow measurement is to install thermal sensors to the depths approximately equal to 3 m that are not influenced by the diurnal, annual, and longer-term fluctuations of the surface thermal environment. In addition, once deployed, the heat flow probe should cause little disturbance to the thermal regime of the surrounding regolith. A heat-flow probe system was developed that has two novel features: (1) it utilizes a pneumatic (gas) approach, excavates a hole by lofting the lunar soil out of the hole, and (2) deploys the heat flow probe, which utilizes a coiled up tape as a thermal probe to reach greater than 3-meter depth. The system is a game-changer for small lunar landers as it exhibits extremely low mass, volume, and simple deployment. The pneumatic system takes advantage of the helium gas used for pressurizing liquid propellant of the lander. Normally, helium is vented once the lander is on the surface, but it can be utilized for powering pneumatic systems. Should sufficient helium not be available, a simple gas delivery system may be taken specifically for the heat flow probe. Either way, the pneumatic heat flow probe system would be much lighter than other systems that entirely rely on the electrical power of the lander.

Numerical simulation of heat transfer and fluid flow of Water-CuO Nanofluid in a sinusoidal channel with a porous medium

NASA Astrophysics Data System (ADS)

Nazari, Saman; Toghraie, Davood

2017-03-01

This study has compared the convection heat transfer of Water-based fluid flow with that of Water-Copper oxide (CuO) nanofluid in a sinusoidal channel with a porous medium. The heat flux in the lower and upper walls has been assumed constant, and the flow has been assumed to be two-dimensional, steady, laminar, and incompressible. The governing equations include equations of continuity, momentum, and energy. The assumption of thermal equilibrium has been considered between the porous medium and the fluid. The effects of the parameters, Reynolds number and Darcy number on the thermal performance of the channel, have been investigated. The results of this study show that the presence of a porous medium in a channel, as well as adding nanoparticles to the base fluid, increases the Nusselt number and the convection heat transfer coefficient. Also the results show that As the Reynolds number increases, the temperature gradient increases. In addition, changes in this parameter are greater in the throat of the flow than in convex regions due to changes in the channel geometry. In addition, porous regions reduce the temperature difference, which in turn increases the convective heat transfer coefficient.

Three-dimensional Models of Hydrothermal Circulation through a Seamount Network in Fast-spreading Crust

NASA Astrophysics Data System (ADS)

Fisher, A. T.; Lauer, R. M.; Winslow, D. M.

2015-12-01

There is a region of 20-24 M.y. old seafloor on the eastern flank of the East Pacific Rise, offshore of Costa Rica, where the advective heat loss from the crust is 60-85% of lithospheric. Much of this advective flux occurs through basement outcrops that penetrate regionally thick sediments, but rates and patterns of hydrothermal circulation in this area are poorly understood. We have run a series of numerical simulations of coupled fluid-heat transport to assess how crustal aquifer and outcrop properties and the distance(s) between outcrops control ridge-flank hydrothermal flows in this setting. Extracting a large fraction of lithospheric heat through this process requires crustal aquifer permeability on the order of 10-10 to 10-9 m2, values considerably higher than seen on other ridge flanks (where advective heat extraction is less efficient). In simulations using two crustal outcrops having a different size, vigorous discharge of outcrop-to-outcrop flow is favored through the smaller and/or less permeable outcrop. In addition, simulations with a larger grid (40 km square versus 20 km square) result in higher fluid flow rates, apparently because there is more heat to be mined by flow between the outcrops. For simulations matching regional heat extraction observations, the outcrop-to-outcrop flow rates from the smaller outcrops are 1,000-3,000 kg/s (for the smaller grids) and 2,000-10,000 kg/s (for larger grids), values consistent with predictions made on the basis of a regional heat flux budget. In many simulations, local convection in and out of individual, large outcrops also removes a significant fraction of lithospheric heat. Additional simulations were conducted with three or four outcrops per simulation grid, to further explore relationships between the geometry, properties, and advective heat extraction.

Development of the Automated AFAPL Engine Simulator Test for Lubricant Evaluation.

DTIC Science & Technology

1981-05-01

including foreign nations. This technical report has been reviewed and is approved for publication. LEON 4JDEBROtUN R.D. DAYTO,*tighief Project Engineer...flow is jetted into the front and rear of the simulator gearbox to provide additional cooling to the gearbox. A heat exchanger is used to cool the oil...flow to the gearbox. Additional heat exchangers are used in the simulator and gearbox oil return lines to the external sump. The simulator test

Ice Generation and the Heat and Mass Transfer Phenomena of Introducing Water to a Cold Bath of Brine.

PubMed

Yun, Xiao; Quarini, Giuseppe L

2017-03-13

We demonstrate a method for the study of the heat and mass transfer and of the freezing phenomena in a subcooled brine environment. Our experiment showed that, under the proper conditions, ice can be produced when water is introduced to a bath of cold brine. To make ice form, in addition to having the brine and water mix, the rate of heat transfer must bypass that of mass transfer. When water is introduced in the form of tiny droplets to the brine surface, the mode of heat and mass transfer is by diffusion. The buoyancy stops water from mixing with the brine underneath, but as the ice grows thicker, it slows down the rate of heat transfer, making ice more difficult to grow as a result. When water is introduced inside the brine in the form of a flow, a number of factors are found to influence how much ice can form. Brine temperature and concentration, which are the driving forces of heat and mass transfer, respectively, can affect the water-to-ice conversion ratio; lower bath temperatures and brine concentrations encourage more ice to form. The flow rheology, which can directly affect both the heat and mass transfer coefficients, is also a key factor. In addition, the flow rheology changes the area of contact of the flow with the bulk fluid.

Anomalous heat transport and condensation in convection of cryogenic helium

PubMed Central

Urban, Pavel; Schmoranzer, David; Hanzelka, Pavel; Sreenivasan, Katepalli R.; Skrbek, Ladislav

2013-01-01

When a hot body A is thermally connected to a cold body B, the textbook knowledge is that heat flows from A to B. Here, we describe the opposite case in which heat flows from a colder but constantly heated body B to a hotter but constantly cooled body A through a two-phase liquid–vapor system. Specifically, we provide experimental evidence that heat flows through liquid and vapor phases of cryogenic helium from the constantly heated, but cooler, bottom plate of a Rayleigh–Bénard convection cell to its hotter, but constantly cooled, top plate. The bottom plate is heated uniformly, and the top plate is cooled by heat exchange with liquid helium maintained at 4.2 K. Additionally, for certain experimental conditions, a rain of helium droplets is detected by small sensors placed in the cell at about one-half of its height. PMID:23576759

Three-dimensional numerical study of heat transfer enhancement in separated flows

NASA Astrophysics Data System (ADS)

Kumar, Saurav; Vengadesan, S.

2017-11-01

The flow separation appears in a wide range of heat transfer applications and causes poor heat transfer performance. It motivates the study of heat transfer enhancement in laminar as well as turbulent flows over a backward facing step by means of an adiabatic fin mounted on the top wall. Recently, we have studied steady, 2-D numerical simulations in laminar flow and investigated the effect of fin length, location, and orientation. It revealed that the addition of fin causes enhancement of heat transfer and it is very effective to control the flow and thermal behavior. The fin is most effective and sensitive when it is placed exactly above the step. A slight displacement of the fin in upstream of the step causes the complete change of flow and thermal behavior. Based on the obtained 2-D results it is interesting to investigate the side wall effect in three-dimensional simulations. The comparison of two-dimensional and three-dimensional numerical simulations with the available experimental results will be presented. Special attention has to be given to capture unsteadiness in the flow and thermal field.

Interfacing the Generalized Fluid System Simulation Program with the SINDA/G Thermal Program

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Palmiter, Christopher; Farmer, Jeffery; Lycans, Randall; Tiller, Bruce

2000-01-01

A general purpose, one dimensional fluid flow code has been interfaced with the thermal analysis program SINDA/G. The flow code, GFSSP, is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development was conducted in two phases. This paper describes the first (which allows for steady and quasi-steady - unsteady solid, steady fluid - conjugate heat transfer modeling). The second (full transient conjugate heat transfer modeling) phase of the interface development will be addressed in a later paper. Phase 1 development has been benchmarked to an analytical solution with excellent agreement. Additional test cases for each development phase demonstrate desired features of the interface. The results of the benchmark case, three additional test cases and a practical application are presented herein.

Steady State Pyrolysis and Ablation Investigation

DTIC Science & Technology

2008-03-31

the heat flux rises with increased transpiration mass flow. For mass 0.050 0.075 Mass flow [g/s] Figure 1.5: Heat flux with and without chocking ...initial species are N2 and 02- As the flow passes through the shock wave surrounding the body, additional species are produced by dis- sociation and...which images the plasma flow after a second reflect on a flat mirror on the entrance of an optical fiber. The captured light is then sent to an Ocean

Experimental Testing and Numerical Modeling of Spray Cooling Under Terrestrial Gravity Conditions

DTIC Science & Technology

2005-01-01

running safely. Mudawar (2000) identifies two heat flux ranges relative to the amount of heat dissipation. The high-flux range includes heat fluxes on...inferior to those of water ( Mudawar , 2000). Phase change cooling can exist in several forms, or cooling schemes. Pool boiling may be used in...addition to reducing the significant effects of flow orientation ( Mudawar , 2000). It is not fully known how low gravity affects flow boiling, as

Comparison of experimental with theoretical total-pressure loss in parallel-walled turbojet combustors

NASA Technical Reports Server (NTRS)

Dittrich, Ralph T

1957-01-01

An experimental investigation of combustor total-pressure loss was undertaken to confirm previous theoretical analyses of effects of geometric and flow variables and of heat addition. The results indicate that a reasonable estimate of cold-flow total-pressure-loss coefficient may be obtained from the theoretical analyses. Calculated total-pressure loss due to heat addition agreed with experimental data only when there was no flame ejection from the liner at the upstream air-entry holes.

Mixed convection flow of nanofluid in a square enclosure with an intruded rectangular fin

NASA Astrophysics Data System (ADS)

Cong, Ran; Zhou, Xuanyu; De Souza Machado, Bruno; Das, Prodip K.

2016-07-01

Mixed convection flow in enclosures has been a subject of interest for many years due to their ever increasing applications in solar collectors, electronic cooling, lubrication technologies, food processing, and nuclear reactors. In comparison, little effort has been given to the problem of mixed convection in enclosures filled with nanofluids, while the addition of nanoparticles in a fluid base to alter specific material properties is considered a feasible solution for many heat transfer problems. Mixed convection of nanofluids is a challenging problem as the addition of nanoparticles changes the fluid's thermo-physical properties as well as due to the complex interactions among inertia, viscous, and buoyancy forces. In this study, a two-dimensional steady-state numerical model has been developed to investigate mixed convection flow of nanofluids in a square enclosure with an intruded rectangular fin and to optimize the fin geometry for maximizing the heat transfer using the Constructal design. The model has been developed using ANSYS-FLUENT for various fin geometries. Flow fields, temperature fields, and heat transfer rates are examined for different values of Rayleigh and Reynolds numbers for several geometries of the fin with the aim of maximizing the heat transfer from the fin to the surrounding flow. Outcome of this study provides important insight into the heat transfer behavior of nanofluids, which will help in developing novel geometries with enhanced and controlled heat transfer for solar collectors and electronic devices.

Mixed convection flow of nanofluid in a square enclosure with an intruded rectangular fin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cong, Ran; Zhou, Xuanyu; De Souza Machado, Bruno

Mixed convection flow in enclosures has been a subject of interest for many years due to their ever increasing applications in solar collectors, electronic cooling, lubrication technologies, food processing, and nuclear reactors. In comparison, little effort has been given to the problem of mixed convection in enclosures filled with nanofluids, while the addition of nanoparticles in a fluid base to alter specific material properties is considered a feasible solution for many heat transfer problems. Mixed convection of nanofluids is a challenging problem as the addition of nanoparticles changes the fluid’s thermo-physical properties as well as due to the complex interactionsmore » among inertia, viscous, and buoyancy forces. In this study, a two-dimensional steady-state numerical model has been developed to investigate mixed convection flow of nanofluids in a square enclosure with an intruded rectangular fin and to optimize the fin geometry for maximizing the heat transfer using the Constructal design. The model has been developed using ANSYS-FLUENT for various fin geometries. Flow fields, temperature fields, and heat transfer rates are examined for different values of Rayleigh and Reynolds numbers for several geometries of the fin with the aim of maximizing the heat transfer from the fin to the surrounding flow. Outcome of this study provides important insight into the heat transfer behavior of nanofluids, which will help in developing novel geometries with enhanced and controlled heat transfer for solar collectors and electronic devices.« less

Oscillating side-branch enhancements of thermoacoustic heat exchangers

DOEpatents

Swift, Gregory W.

2003-05-13

A regenerator-based engine or refrigerator has a regenerator with two ends at two different temperatures, through which a gas oscillates at a first oscillating volumetric flow rate in the direction between the two ends and in which the pressure of the gas oscillates, and first and second heat exchangers, each of which is at one of the two different temperatures. A dead-end side branch into which the gas oscillates has compliance and is connected adjacent to one of the ends of the regenerator to form a second oscillating gas flow rate additive with the first oscillating volumetric flow rate, the compliance having a volume effective to provide a selected total oscillating gas volumetric flow rate through the first heat exchanger. This configuration enables the first heat exchanger to be configured and located to better enhance the performance of the heat exchanger rather than being confined to the location and configuration of the regenerator.

Heat Flux Sensor

NASA Technical Reports Server (NTRS)

1994-01-01

A heat flux microsensor developed under a NASP Small Business Innovation Research (SBIR) has a wide range of potential commercial applications. Vatell Corporation originally designed microsensors for use in very high temperatures. The company then used the technology to develop heat flux sensors to measure the rate of heat energy flowing in and out of a surface as well as readings on the surface temperature. Additional major advantages include response to heat flux in less than 10 microseconds and the ability to withstand temperatures up to 1,200 degrees centigrade. Commercial applications are used in high speed aerodynamics, supersonic combustion, blade cooling, and mass flow measurements, etc.

Development of Flow Boiling and Condensation Experiment on the International Space Station- Normal and Low Gravity Flow Boiling Experiment Development and Test Results

NASA Technical Reports Server (NTRS)

Nahra, Henry K.; Hall, Nancy R.; Hasan, Mohammad M.; Wagner, James D.; May, Rochelle L.; Mackey, Jeffrey R.; Kolacz, John S.; Butcher, Robert L.; Frankenfield, Bruce J.; Mudawar, Issam;

Wake Flow About the Mars Pathfinder Entry Vehicle

NASA Technical Reports Server (NTRS)

Mitcheltree, R. A.; Gnoffo, P. A.

1995-01-01

A computational approach is used to describe the aerothermodynamics of the Mars Pathfinder vehicle entering the Mars atmosphere at the maximum heating and maximum deceleration points in its trajectory. Ablating and nonablating boundary conditions are developed which produce maximum recombination of CO2 on the surface. For the maximum heating trajectory point, an axisymmetric, nonablating calculation predicts a stagnation-point value for the convective heating of 115 W/cm(exp 2). Radiative heating estimates predict an additional 5-12 W/cm(exp 2) at the stagnation point. Peak convective heating on the afterbody occurs on the vehicle's flat stern with a value of 5.9% of the stagnation value. The forebody flow exhibits chemical nonequilibrium behavior, and the flow is frozen in the near wake. Including ablation injection on the forebody lowers the stagnation-point convective heating 18%.

Heat Transfer to Anode of Arc as Function of Transverse Magnetic Field and Lateral Gas Flow Velocity

NASA Astrophysics Data System (ADS)

Zama, Yoshiyuki; Shiino, Toru; Ishii, Yoko; Maeda, Yoshifumi; Yamamoto, Shinji; Iwao, Toru

2016-10-01

Gas tungsten arc welding has useful joining technology because of high-energy and high-current characteristics. It can be flexible from the transverse magnetic field and lateral gas flow velocity. In this case, the weld defect occurs. In this research, the heat transfer to the anode of the arc as a function of the transverse magnetic field and lateral gas flow velocity is elucidated. That magnetic flux density and lateral gas velocity were varied from 0 to 3 mT and 0 to 50?m?s -1, respectively. The axial plasma gas argon flow rates were 3?slm. A transverse magnetic field is applied to the arc using Helmholtz coil. The anode is used by a water-cooled copper plate, and the heat transfer is measured by temperature of cooled water. As a result, the arc is deflected by the Lorentz force and lateral gas convection. Thus, the heat transfer to the anode of the arc decreases with increasing the transverse magnetic field and lateral gas flow velocity. In addition, the heat transfer to the anode changes with different attachments modes. The lateral gas flow causes a convective heat loss from the arc to the chamber walls.

Hot springs, geochemistry, and regional heat flow of northcentral Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanberg, C.A.; Marvin, P.R.; Salazar S., L.

1981-10-01

To date we have found, sampled and performed chemical analyses on 21 hot springs (T > 30/sup 0/C), 4 hot wells (T > 30/sup 0/C) and 15 warm springs (T = 25 to 30/sup 0/C) from the states of Chihuahua, Coahuila and Sonora, Mexico. Also in order to establish background chemistry, an additional 250 cold wells and springs (T = 12 to 25/sup 0/C) were sampled and analyzed and several hundred water analyses from the several thousand provided by various Mexican agencies were included. The technique of silica geothermometry was used to estimate the regional heat flow of northcentral Mexico.more » Both the traditional heat flow and the silica heat flow values are generally high and show considerable scatter as is typical of areas having Tertiary and Quaternary volcanic and tectonic activity. Specific areas of high heat flow (> 2.5 HFU) include the Presidio and Los Muertos Bolsons, the Cuidad Chihuahua-Chuatemoc area, the Delicias area, and the area south of the San Bernardino Bolson of southeast Arizona. Areas of lower heat flow (2.0 to 2.5 HFU) include the Jimenez-Camargo region and the area between the Los Muertos and Presidio Bolsons.« less

Heat-exchanger concepts for neutral-beam calorimeters

NASA Astrophysics Data System (ADS)

Thompson, C. C.; Polk, D. H.; McFarlin, D. J.; Stone, R.

1981-10-01

Advanced cooling concepts that permit the design of water cooled heat exchangers for use as calorimeters and beam dumps for advanced neutral beam injection systems were evaluated. Water cooling techniques ranging from pool boiling to high pressure, high velocity swirl flow were considered. Preliminary performance tests were carried out with copper, inconel and molybdenum tubes ranging in size from 0.19 to 0.50 in. diameter. Coolant flow configurations included: (1) smooth tube/straight flow; (2) smooth tube with swirl flow created by tangential injection of the coolant; and (3) axial flow in internally finned tubes. Additionally, the effect of tube L/D was evaluated. A CO2 laser was employed to irradiate a sector of the tube exterior wall; the laser power was incrementally increased until burnout occurred. Absorbed heat fluxes were calculated by dividing the measured coolant heat load by the area of the burn spot on the tube surface. Two six element thermopiles were used to accurately determine the coolant temperature rise. A maximum burnout heat flux near 14 kW/sq cm was obtained for the molybdenum tube swirl flow configuration.

Heat Flow, Thermal Conductivity, and the Plausibility of the White Mars Hypothesis

NASA Technical Reports Server (NTRS)

Urquhart, M. L.; Gulick, V. C.

2002-01-01

Due to the low thermal conductivity of CO2 ice and clathrate vs. water ice, we find that liquid water reservoirs would not be confined to the deep subsurface as predicted by the controversial White Mars model, even assuming low global heat flow. Additional information is contained in the original extended abstract.

Analysis of counter flow of corona wind for heat transfer enhancement

NASA Astrophysics Data System (ADS)

Shin, Dong Ho; Baek, Soo Hong; Ko, Han Seo

2018-03-01

A heat sink for cooling devices using the counter flow of a corona wind was developed in this study. Detailed information about the numerical investigations of forced convection using the corona wind was presented. The fins of the heat sink using the counter flow of a corona wind were also investigated. The corona wind generator with a wire-to-plate electrode arrangement was used for generating the counter flow to the fin. The compact and simple geometric characteristics of the corona wind generator facilitate the application of the heat sink using the counter flow, demonstrating the heat sink is effective for cooling electronic devices. Parametric studies were performed to analyze the effect of the counter flow on the fins. Also, the velocity and temperature were measured experimentally for the test mock-up of the heat sink with the corona wind generator to verify the numerical results. From a numerical study, the type of fin and its optimal height, length, and pitch were suggested for various heat fluxes. In addition, the correlations to calculate the mass of the developed heat sink and its cooling performance in terms of the heat transfer coefficient were derived. Finally, the cooling efficiencies corresponding to the mass, applied power, total size, and noise of the devices were compared with the existing commercial central processing unit (CPU) cooling devices with rotor fans. As a result, it was confirmed that the heat sink using the counter flow of the corona wind showed appropriate efficiencies for cooling electronic devices, and is a suitable replacement for the existing cooling device for high power electronics.

The influence of flow modification on air and PCM temperatures in an accumulative heat exchanger

NASA Astrophysics Data System (ADS)

Borcuch, Marcin; Musiał, Michał; Sztekler, Karol; Kalawa, Wojciech; Gumuła, Stanisław; Stefański, Sebastian

2018-06-01

The paper presents the influence of flow modification on the operation of an accumulative heat exchanger. This device can be used as a regenerator in ventilation and air supply systems. A heat exchanger uses ceresine (a mixture of paraffins) as a phase change material (PCM). The aim of this research was to determine the effect of flow modification on temperature distribution and pressure drops in the device. The introduction contains a short description of the test stand used, including the accumulative heat exchanger, the guide vanes, and the locations of measurement and control equipment. We found that additional objects limited vortex structures, increased the inside temperature, and dropped the pressure along the heat exchanger. Guidelines for further research are proposed and briefly discussed.

Experimental study of the effect of drag reducing agent on pressure drop and thermal efficiency of an air cooler

NASA Astrophysics Data System (ADS)

Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Saffarian, H.; Shekari, F.

2016-01-01

Effect of polymeric drag reduction agents (DRAs) on pressure drop and heat transfer was studied. Aqueous solutions of carboxy methyl cellulose were used inside an air-finned heat exchanger. Despite the previous studies which indicated the importance of drag reduction just in turbulent flow, results of this study in laminar flow indicated that the addition of DRA increases drag reduction, and decreases the overall heat transfer coefficient.

Enhancing Convective Heat Transfer over a Surrogate Photovoltaic Panel

NASA Astrophysics Data System (ADS)

Fouladi, Fama

This research is particularly focused on studying heat transfer enhancement of a photovoltaic (PV) panel by putting an obstacle at the panel's windward edge. The heat transfer enhancement is performed by disturbing the airflow over the surface and increasing the heat and momentum transfer. Different objects such as triangular, square, rectangular, and discrete rectangular ribs and partial grids were applied at the leading edge of a surrogate PV panel and flow and the heat transfer of the panel are investigated experimentally. This approach was selected to expand understanding of effect of these different objects on the flow and turbulence structures over a flat surface by analyzing the flow comprehensively. It is observed that, a transverse object at the plate's leading edge would cause some flow blockage in the streamwise direction, but at the same time creates some velocity in the normal and cross stream directions. In addition to that, the obstacle generates some turbulence over the surface which persists for a long downstream distance. Also, among all studied objects, discrete rectangular ribs demonstrate the highest heat transfer rate enhancement (maximum Nu/Nu0 of 1.5). However, ribs with larger gap ratios are observed to be more effective at enhancing the heat transfer augmentation at closer distances to the rib, while at larger downstream distances from the rib, discrete ribs with smaller gap ratios are more effective. Furthermore, this work attempted to recognize the most influential flow parameters on the heat transfer enhancement of the surface. It is seen that the flow structure over a surface downstream of an object (flow separation-reattachment behaviour) has a significant effect on the heat transfer enhancement trend. Also, turbulence intensities are the most dominant parameters in enhancing the heat transfer rate from the surface; however, flow velocity (mostly normal velocity) is also an important factor.

The characteristics of heat flow in the Shenhu gas hydrate drilling area, northern South China Sea

NASA Astrophysics Data System (ADS)

Xu, Xing; Wan, Zhifeng; Wang, Xianqing; Sun, Yuefeng; Xia, Bin

2016-12-01

Marine heat flow is of great significance for the formation and occurrence of seabed oil, gas and gas hydrate resources. Geothermal gradient is an important parameter in determining the thickness of the hydrate stability zone. The northern slope of the South China Sea is rich in gas hydrate resources. Several borehole drilling attempts were successful in finding hydrates in the Shenhu area, while others were not. The failures demand further study on the distribution regularities of heat flow and its controlling effects on hydrate occurrence. In this study, forty-eight heat flow measurements are analyzed in the Shenhu gas hydrate drilling area, located in the northern South China Sea, together with their relationship to topography, sedimentary environment and tectonic setting. Canyons are well developed in the study area, caused mainly by the development of faults, faster sediment supply and slumping of the Pearl River Estuary since the late Miocene in the northern South China Sea. The heat flow values in grooves, occurring always in fault zones, are higher than those of ridges. Additionally, the heat flow values gradually increase from the inner fan, to the middle fan, to the external fan subfacies. The locations with low heat flow such as ridges, locations away from faults and the middle fan subfacies, are more conducive to gas hydrate occurrence.

Patterning of ultrathin polymethylmethacrylate films by in-situ photodirecting of the Marangoni flow

NASA Astrophysics Data System (ADS)

Elashnikov, Roman; Fitl, Premysl; Svorcik, Vaclav; Lyutakov, Oleksiy

2017-02-01

Laser heating and Marangoni flow result in the formation of surface structures with different geometries and shape on thin polymer films. By laser beam irradiation combined with a sample movement the solid polymethylmethacrylate (PMMA) films are heated and undergo phase transition which leads to a material flow. Since the laser beam has a non-linear distribution of energy, the PMMA film is heated inhomogeneously and a surface tension gradient in a lateral direction is introduced. During this procedure additional phenomena such as "reversible" or cyclic polymer flow also take place. The careful choice of experimental conditions enables the preparation of patterns with sophisticated geometries and with hierarchical pattern organization. Depending on initial PMMA film thickness and speed of the sample movement line arrays are created, which can subsequently be transformed into the crimped lines or system of circular holes. In addition, the introduction of a constant acceleration in the sample movement or a laser beam distortion enables the preparation of regularly crimped lines, ordered hexagonal holes or overlapped plates.

Long-lasting Science Returns from the Apollo Heat Flow Experiments

NASA Astrophysics Data System (ADS)

Nagihara, S.; Taylor, P. T.; Williams, D. R.; Zacny, K.; Hedlund, M.; Nakamura, Y.

2012-12-01

The Apollo astronauts deployed geothermal heat flow instruments at landing sites 15 and 17 as part of the Apollo Lunar Surface Experiments Packages (ALSEP) in July 1971 and December 1972, respectively. These instruments continuously transmitted data to the Earth until September 1977. Four decades later, the data from the two Apollo sites remain the only set of in-situ heat flow measurements obtained on an extra-terrestrial body. Researchers continue to extract additional knowledge from this dataset by utilizing new analytical techniques and by synthesizing it with data from more recent lunar orbital missions such as the Lunar Reconnaissance Orbiter. In addition, lessons learned from the Apollo experiments help contemporary researchers in designing heat flow instruments for future missions to the Moon and other planetary bodies. For example, the data from both Apollo sites showed gradual warming trends in the subsurface from 1971 to 1977. The cause of this warming has been debated in recent years. It may have resulted from fluctuation in insolation associated with the 18.6-year-cycle precession of the Moon, or sudden changes in surface thermal environment/properties resulting from the installation of the instruments and the astronauts' activities. These types of re-analyses of the Apollo data have lead a panel of scientists to recommend that a heat flow probe carried on a future lunar mission reach 3 m into the subsurface, ~0.6 m deeper than the depths reached by the Apollo 17 experiment. This presentation describes the authors' current efforts for (1) restoring a part of the Apollo heat flow data that were left unprocessed by the original investigators and (2) designing a compact heat flow instrument for future robotic missions to the Moon. First, at the conclusion of the ALSEP program in 1977, heat flow data obtained at the two Apollo sites after December 1974 were left unprocessed and not properly archived through NASA. In the following decades, heat flow data from January 1975 through February 1976, as well as the metadata necessary for processing the data (the data reduction algorithm, instrument calibration data, etc.), were somehow lost. In 2010, we located 450 original master archival tapes of unprocessed data from all the ALSEP instruments for a period of April through June 1975 at the Washington National Records Center. We are currently extracting the heat flow data packets from these tapes and processing them. Second, on future lunar missions, heat flow probes will likely be deployed by a network of small robotic landers, as recommended by the latest Decadal Survey of the National Academy of Science. In such a scenario, the heat flow probe must be a compact system, and that precludes use of heavy excavation equipment such as a rotary drill for reaching the 3-m target depth. The new heat flow system under development uses a pneumatically driven penetrator. It utilizes a stem that winds out of a reel and pushes its conical tip into the regolith. Simultaneously, gas jets, emitted from the cone tip, loosen and blow away the soil. Lab experiments have demonstrated its effectiveness in lunar vacuum.

Long-Lasting Science Returns from the Apollo Heat Flow Experiments

NASA Technical Reports Server (NTRS)

Nagihara, S.; Taylor, P. T.; Williams, D. R.; Zacny, K.; Hedlund, M.; Nakamura, Y.

2012-01-01

The Apollo astronauts deployed geothermal heat flow instruments at landing sites 15 and 17 as part of the Apollo Lunar Surface Experiments Packages (ALSEP) in July 1971 and December 1972, respectively. These instruments continuously transmitted data to the Earth until September 1977. Four decades later, the data from the two Apollo sites remain the only set of in-situ heat flow measurements obtained on an extra-terrestrial body. Researchers continue to extract additional knowledge from this dataset by utilizing new analytical techniques and by synthesizing it with data from more recent lunar orbital missions such as the Lunar Reconnaissance Orbiter. In addition, lessons learned from the Apollo experiments help contemporary researchers in designing heat flow instruments for future missions to the Moon and other planetary bodies. For example, the data from both Apollo sites showed gradual warming trends in the subsurface from 1971 to 1977. The cause of this warming has been debated in recent years. It may have resulted from fluctuation in insolation associated with the 18.6-year-cycle precession of the Moon, or sudden changes in surface thermal environment/properties resulting from the installation of the instruments and the astronauts' activities. These types of reanalyses of the Apollo data have lead a panel of scientists to recommend that a heat flow probe carried on a future lunar mission reach 3 m into the subsurface, approx 0.6 m deeper than the depths reached by the Apollo 17 experiment. This presentation describes the authors current efforts for (1) restoring a part of the Apollo heat flow data that were left unprocessed by the original investigators and (2) designing a compact heat flow instrument for future robotic missions to the Moon. First, at the conclusion of the ALSEP program in 1977, heat flow data obtained at the two Apollo sites after December 1974 were left unprocessed and not properly archived through NASA. In the following decades, heat flow data from January 1975 through February 1976, as well as the metadata necessary for processing the data (the data reduction algorithm, instrument calibration data, etc.), were somehow lost. In 2010, we located 450 original master archival tapes of unprocessed data from all the ALSEP instruments for a period of April through June 1975 at the Washington National Records Center. We are currently extracting the heat flow data packets from these tapes and processing them. Second, on future lunar missions, heat flow probes will likely be deployed by a network of small robotic landers, as recommended by the latest Decadal Survey of the National Academy of Science. In such a scenario, the heat flow probe must be a compact system, and that precludes use of heavy excavation equipment such as a rotary drill for reaching the 3-m target depth. The new heat flow system under development uses a pneumatically driven penetrator. It utilizes a stem that winds out of a reel and pushes its conical tip into the regolith. Simultaneously, gas jets, emitted from the cone tip, loosen and blow away the soil. Lab experiments have demonstrated its effectiveness in lunar vacuum.

Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

NASA Technical Reports Server (NTRS)

Cross, M. F.

2011-01-01

A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.

Laboratory simulations of cumulus cloud flows explain the entrainment anomaly

NASA Astrophysics Data System (ADS)

Narasimha, Roddam; Diwan, Sourabh S.; Subrahmanyam, Duvvuri; Sreenivas, K. R.; Bhat, G. S.

2010-11-01

In the present laboratory experiments, cumulus cloud flows are simulated by starting plumes and jets subjected to off-source heat addition in amounts that are dynamically similar to latent heat release due to condensation in real clouds. The setup permits incorporation of features like atmospheric inversion layers and the active control of off-source heat addition. Herein we report, for the first time, simulation of five different cumulus cloud types (and many shapes), including three genera and three species (WMO Atlas 1987), which show striking resemblance to real clouds. It is known that the rate of entrainment in cumulus cloud flows is much less than that in classical plumes - the main reason for the failure of early entrainment models. Some of the previous studies on steady-state jets and plumes (done in a similar setup) have attributed this anomaly to the disruption of the large-scale turbulent structures upon the addition of off-source heat. We present estimates of entrainment coefficients from these measurements which show a qualitatively consistent variation with height. We propose that this explains the observed entrainment anomaly in cumulus clouds; further experiments are planned to address this question in the context of starting jets and plumes.

Heat flow study of the Emeishan large igneous province region: Implications for the geodynamics of the Emeishan mantle plume

NASA Astrophysics Data System (ADS)

Jiang, Qiang; Qiu, Nansheng; Zhu, Chuanqing

2018-01-01

The Emeishan large igneous province (ELIP) is widely considered to be a consequence of a mantle plume. The supporting evidence includes rapid emplacement, voluminous flood basalt eruptions, and high mantle potential temperature estimates. Several studies have suggested that there was surface uplift prior to the eruption of the Emeishan flood basalts. Additionally, the plume's lateral extent is hard to constrain and has been variously estimated to be 800-1400 km in diameter. In this study, we analyzed present-day heat flow data and reconstructed the Permian paleo-heat flow using vitrinite reflectance and zircon (U-Th)/He thermochronology data in the ELIP region and discussed implications for the geodynamics of the Emeishan mantle plume. The present-day heat flow is higher in the inner and intermediate zones than in the outer zone, with a decrease of average heat flow from 76 mW/m2 to 51 mW/m2. Thermal history modeling results show that an abnormal high paleo-heat flow of 90-110 mW/m2 was caused by the Emeishan mantle plume activity. Based on the present-day heat flow data, we can calculate that there is lithospheric thinning in the central ELIP region, which may be due to the destruction of the lithosphere by mantle plume upwelling and magmatic underplating. The Permian paleo-heat flow anomaly implies that there was a temperature anomaly in the mantle. The ascending high-temperature mantle plume and the thinned lithosphere may have induced the large-scale uplift in the ELIP region. According to the range of the surface heat flow anomaly, it can be estimated that the diameter of the flattened head of the Emeishan mantle plume could have reached 1600-1800 km. Our research provides new insights into the geodynamics of the Emeishan mantle plume through study of heat flow.

Two-Dimensional, Supersonic, Linearized Flow with Heat Addition

NASA Technical Reports Server (NTRS)

Lomax, Harvard

1959-01-01

Calculations are presented for the forces on a thin supersonic wing underneath which the air is heated. The analysis is limited principally to linearized theory but nonlinear effects are considered. It is shown that significant advantages to external heating would exist if the heat were added well below and ahead of the wing.

A Study of Heat Transfer and Flow Characteristics of Rising Taylor Bubbles

NASA Technical Reports Server (NTRS)

Scammell, Alexander David

2016-01-01

Practical application of flow boiling to ground- and space-based thermal management systems hinges on the ability to predict the systems heat removal capabilities under expected operating conditions. Research in this field has shown that the heat transfer coefficient within two-phase heat exchangers can be largely dependent on the experienced flow regime. This finding has inspired an effort to develop mechanistic heat transfer models for each flow pattern which are likely to outperform traditional empirical correlations. As a contribution to the effort, this work aimed to identify the heat transfer mechanisms for the slug flow regime through analysis of individual Taylor bubbles.An experimental apparatus was developed to inject single vapor Taylor bubbles into co-currently flowing liquid HFE 7100. The heat transfer was measured as the bubble rose through a 6 mm inner diameter heated tube using an infrared thermography technique. High-speed flow visualization was obtained and the bubble film thickness measured in an adiabatic section. Experiments were conducted at various liquid mass fluxes (43-200 kgm2s) and gravity levels (0.01g-1.8g) to characterize the effect of bubble drift velocityon the heat transfer mechanisms. Variable gravity testing was conducted during a NASA parabolic flight campaign.Results from the experiments showed that the drift velocity strongly affects the hydrodynamics and heat transfer of single elongated bubbles. At low gravity levels, bubbles exhibited shapes characteristic of capillary flows and the heat transfer enhancement due to the bubble was dominated by conduction through the thin film. At moderate to high gravity, traditional Taylor bubbles provided small values of enhancement within the film, but large peaks in the wake heat transfer occurred due to turbulent vortices induced by the film plunging into the trailing liquid slug. Characteristics of the wake heat transfer profiles were analyzed and related to the predicted velocity field. Results were compared and shown to agree with numerical simulations of colleagues from EPFL, Switzerland.In addition, a preliminary study was completed on the effect of a Taylor bubble passing through nucleate flow boiling, showing that the thinning thermal boundary layer within the film suppressed nucleation, thereby decreasing the heat transfer coefficient.

Overview of the Icing and Flow Quality Improvements Program for the NASA Glenn Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Irvine, Thomas B.; Kevdzija, Susan L.; Sheldon, David W.; Spera, David A.

2001-01-01

Major upgrades were made in 1999 to the 6- by 9-Foot (1.8- by 2.7-m) Icing Research Tunnel (IRT) at the NASA Glenn Research Center. These included replacement of the electronic controls for the variable-speed drive motor, replacement of the heat exchanger, complete replacement and enlargement of the leg of the tunnel containing the new heat-exchanger, the addition of flow-expanding and flow-contracting turning vanes upstream and downstream of the heat exchanger, respectively, and the addition of fan outlet guide vanes (OGV's). This paper describes the rationale behind this latest program of IRT upgrades and the program's requirements and goals. An overview is given of the scope of work undertaken by the design and construction contractors, the scale-model IRT (SMIRT) design verification program, the comprehensive reactivation test program initiated upon completion of construction, and the overall management approach followed.

Computational Fluid Dynamic Modeling of Rocket Based Combined Cycle Engine Flowfields

NASA Technical Reports Server (NTRS)

Daines, Russell L.; Merkle, Charles L.

1994-01-01

Computational Fluid Dynamic techniques are used to study the flowfield of a fixed geometry Rocket Based Combined Cycle engine operating in rocket ejector mode. Heat addition resulting from the combustion of injected fuel causes the subsonic engine flow to choke and go supersonic in the slightly divergent combustor-mixer section. Reacting flow computations are undertaken to predict the characteristics of solutions where the heat addition is determined by the flowfield. Here, adaptive gridding is used to improve resolution in the shear layers. Results show that the sonic speed is reached in the unheated portions of the flow first, while the heated portions become supersonic later. Comparison with results from another code show reasonable agreement. The coupled solutions show that the character of the combustion-based thermal choking phenomenon can be controlled reasonably well such that there is opportunity to optimize the length and expansion ratio of the combustor-mixer.

Measurements of Heat-Transfer and Friction Coefficients for Helium Flowing in a Tube at Surface Temperatures up to 5900 Deg R

NASA Technical Reports Server (NTRS)

Taylor, Maynard F.; Kirchgessner, Thomas A.

1959-01-01

Measurements of average heat transfer and friction coefficients and local heat transfer coefficients were made with helium flowing through electrically heated smooth tubes with length-diameter ratios of 60 and 92 for the following range of conditions: Average surface temperature from 1457 to 4533 R, Reynolds numbe r from 3230 to 60,000, heat flux up to 583,200 Btu per hr per ft2 of heat transfer area, and exit Mach numbe r up to 1.0. The results indicate that, in the turbulent range of Reynolds number, good correlation of the local heat transfer coefficients is obtained when the physical properties and density of helium are evaluated at the surface temperature. The average heat transfer coefficients are best correlated on the basis that the coefficient varies with [1 + (L/D))(sup -0,7)] and that the physical properties and density are evaluated at the surface temperature. The average friction coefficients for the tests with no heat addition are in complete agreement with the Karman-Nikuradse line. The average friction coefficients for heat addition are in poor agreement with the accepted line.

Two-dimensional numerical simulation of a Stirling engine heat exchanger

NASA Technical Reports Server (NTRS)

Ibrahim, Mounir; Tew, Roy C.; Dudenhoefer, James E.

1989-01-01

The first phase of an effort to develop multidimensional models of Stirling engine components is described. The ultimate goal is to model an entire engine working space. Parallel plate and tubular heat exchanger models are described, with emphasis on the central part of the channel (i.e., ignoring hydrodynamic and thermal end effects). The model assumes laminar, incompressible flow with constant thermophysical properties. In addition, a constant axial temperature gradient is imposed. The governing equations describing the model have been solved using the Crack-Nicloson finite-difference scheme. Model predictions are compared with analytical solutions for oscillating/reversing flow and heat transfer in order to check numerical accuracy. Excellent agreement is obtained for flow both in circular tubes and between parallel plates. The computational heat transfer results are in good agreement with the analytical heat transfer results for parallel plates.

Shuttle APS propellant thermal conditioner study

NASA Technical Reports Server (NTRS)

Fulton, D. L.

1971-01-01

The conditioner design concept selected for evaluation consists of an integral reactor and baffle-type heat exchanger. Heat exchange is accomplished by flowing reactor hot gases past a series of slotted and formed plates, through which the conditioned propellant flows. Heat transfer analysis has resulted in the selection of a reactor hot gas nominal mixture ratio of 1.0, giving a combustion temperature of 1560 F with a hydrogen inlet temperature of 275 R. Worst case conditions result in a combustion gas temperature of 2060 F, satisfying the condition of no damage to the conditioner in case of failure to flow cold fluid. In addition, evaluation of hot gas flow requirements and conditioner weight has resulted in the selection of a reactor hot gas exhaust temperature of 750 R.

Particle dispersion and turbulence modification in a dilute mist non-isothermal turbulent flow downstream of a sudden pipe expansion

NASA Astrophysics Data System (ADS)

Terekhov, V. I.; Pakhomov, M. A.

2011-12-01

Flow, particles dispersion and heat transfer of dilute gas-droplet turbulent flow downstream of a pipe sudden expansion have been numerically investigated for the conditions of heated dry wall. An Euler two-fluid model with additional turbulence transport equations for gas and particulate phases was employed in the study. Gas phase turbulence was modelled using the elliptic blending Reynolds stress model of Fadai-Ghotbi et al. (2008). Two-way coupling is achieved between the dispersed and carrier phases. The partial equations of Reynolds stresses and temperature fluctuations, and the turbulent heat flux equations in dispersed phase by Zaichik (1999) were applied. Fine droplets get readily entrained with the detached flow, spread throughout the whole pipe cross-section. On the contrary, large particles, due to their inertia, do not appear in the recirculation zone and are presented only in the shear layer region. The presence of fine dispersed droplets in the flow attenuates the gas phase turbulence of up 25 %. Heat transfer in the mist flow increased (more than twice in comparison with the single-phase air flow). Intensification of heat transfer is observed both in the recirculation zone and flow development region in the case of fine particles. Large particles enhanced heat transfer only in the reattachment zone. Comparison between simulated results and experimental data of Hishida et al. (1995) for mist turbulent separated flow behind a backward-facing step shows quite good agreement.

Comparative evaluation of three heat transfer enhancement strategies in a grooved channel

NASA Astrophysics Data System (ADS)

Herman, C.; Kang, E.

Results of a comparative evaluation of three heat transfer enhancement strategies for forced convection cooling of a parallel plate channel populated with heated blocks, representing electronic components mounted on printed circuit boards, are reported. Heat transfer in the reference geometry, the asymmetrically heated parallel plate channel, is compared with that for the basic grooved channel, and the same geometry enhanced by cylinders and vanes placed above the downstream edge of each heated block. In addition to conventional heat transfer and pressure drop measurements, holographic interferometry combined with high-speed cinematography was used to visualize the unsteady temperature fields in the self-sustained oscillatory flow. The locations of increased heat transfer within one channel periodicity depend on the enhancement technique applied, and were identified by analyzing the unsteady temperature distributions visualized by holographic interferometry. This approach allowed gaining insight into the mechanisms responsible for heat transfer enhancement. Experiments were conducted at moderate flow velocities in the laminar, transitional and turbulent flow regimes. Reynolds numbers were varied in the range Re=200-6500, corresponding to flow velocities from 0.076 to 2.36m/s. Flow oscillations were first observed between Re=1050 and 1320 for the basic grooved channel, and around Re=350 and 450 for the grooved channels equipped with cylinders and vanes, respectively. At Reynolds numbers above the onset of oscillations and in the transitional flow regime, heat transfer rates in the investigated grooved channels exceeded the performance of the reference geometry, the asymmetrically heated parallel plate channel. Heat transfer in the grooved channels enhanced with cylinders and vanes showed an increase by a factor of 1.2-1.8 and 1.5-3.5, respectively, when compared to data obtained for the basic grooved channel; however, the accompanying pressure drop penalties also increased significantly.

40 CFR 96.76 - Additional requirements to provide heat input data for allocations purposes.

Code of Federal Regulations, 2010 CFR

2010-07-01

... TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Monitoring and Reporting § 96.76 Additional requirements... to monitor and report NOX Mass emissions using a NOX concentration system and a flow system shall... chapter for any source located in a state developing source allocations based upon heat input. (b) The...

The development of a performance-enhancing additive for vapor-compression heat pumps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grzyll, L.R.; Scaringe, R.P.; Gottschlich, J.M.

1997-12-31

This paper describes the testing results of a vapor-compression heat pump operating with HFC-134a refrigerant and a performance-enhancing additive. Preliminary bench-top testing of this additive, when added to polyolester (POE) lubricant and HFC-134a refrigerant, showed surprising enhancements to system COP. To further investigate this finding, the authors designed and fabricated a vapor-compression heat pump test stand for the 3--5 ton range. The authors investigated the effect of different concentrations of this additive on various system performance parameters such as cooling capacity, compressor power requirement, pressure ratio, compressor pressure difference, compressor isentropic efficiency, refrigerant flow rate, and heat exchanger performance. Themore » authors investigated various heat source and heat sink conditions to simulate air-conditioning and heat pump operating conditions. To investigate the effect of this additive on compressor lubrication and life, the authors performed compressor life tests (with scroll and reciprocating compressors), and had lubrication wear tests performed with various concentrations of the additive in the POE lubricant.« less

Comparison of DSMC and CFD Solutions of Fire II Including Radiative Heating

NASA Technical Reports Server (NTRS)

Liechty, Derek S.; Johnston, Christopher O.; Lewis, Mark J.

2011-01-01

The ability to compute rarefied, ionized hypersonic flows is becoming more important as missions such as Earth reentry, landing high mass payloads on Mars, and the exploration of the outer planets and their satellites are being considered. These flows may also contain significant radiative heating. To prepare for these missions, NASA is developing the capability to simulate rarefied, ionized flows and to then calculate the resulting radiative heating to the vehicle's surface. In this study, the DSMC codes DAC and DS2V are used to obtain charge-neutral ionization solutions. NASA s direct simulation Monte Carlo code DAC is currently being updated to include the ability to simulate charge-neutral ionized flows, take advantage of the recently introduced Quantum-Kinetic chemistry model, and to include electronic energy levels as an additional internal energy mode. The Fire II flight test is used in this study to assess these new capabilities. The 1634 second data point was chosen for comparisons to be made in order to include comparisons to computational fluid dynamics solutions. The Knudsen number at this point in time is such that the DSMC simulations are still tractable and the CFD computations are at the edge of what is considered valid. It is shown that there can be quite a bit of variability in the vibrational temperature inferred from DSMC solutions and that, from how radiative heating is computed, the electronic temperature is much better suited for radiative calculations. To include the radiative portion of heating, the flow-field solutions are post-processed by the non-equilibrium radiation code HARA. Acceptable agreement between CFD and DSMC flow field solutions is demonstrated and the progress of the updates to DAC, along with an appropriate radiative heating solution, are discussed. In addition, future plans to generate more high fidelity radiative heat transfer solutions are discussed.

Lunar heat flow experiments: Science objectives and a strategy for minimizing the effects of lander-induced perturbations

NASA Astrophysics Data System (ADS)

Kiefer, Walter S.

2012-01-01

Reliable measurements of the Moon's global heat flow would serve as an important diagnostic test for models of lunar thermal evolution and would also help to constrain the Moon's bulk abundance of radioactive elements and its differentiation history. The two existing measurements of lunar heat flow are unlikely to be representative of the global heat flow. For these reasons, obtaining additional heat flow measurements has been recognized as a high priority lunar science objective. In making such measurements, it is essential that the design and deployment of the heat flow probe and of the parent spacecraft do not inadvertently modify the near-surface thermal structure of the lunar regolith and thus perturb the measured heat flow. One type of spacecraft-related perturbation is the shadow cast by the spacecraft and by thermal blankets on some instruments. The thermal effects of these shadows propagate by conduction both downward and outward from the spacecraft into the lunar regolith. Shadows cast by the spacecraft superstructure move over the surface with time and only perturb the regolith temperature in the upper 0.8 m. Permanent shadows, such as from thermal blankets covering a seismometer or other instruments, can modify the temperature to greater depth. Finite element simulations using measured values of the thermal diffusivity of lunar regolith show that the limiting factor for temperature perturbations is the need to measure the annual thermal wave for 2 or more years to measure the thermal diffusivity. The error induced by permanent spacecraft thermal shadows can be kept below 8% of the annual wave amplitude at 1 m depth if the heat flow probe is deployed at least 2.5 m away from any permanent spacecraft shadow. Deploying the heat flow probe 2 m from permanent shadows permits measuring the annual thermal wave for only one year and should be considered the science floor for a heat flow experiment on the Moon. One way to meet this separation requirement would be to deploy the heat flow and seismology experiments on opposite sides of the spacecraft. This result should be incorporated in the design of future lunar geophysics spacecraft experiments. Differences in the thermal environments of the Moon and Mars result in less restrictive separation requirements for heat flow experiments on Mars.

Forced Convection Boiling and Critical Heat Flux of Ethanol in Electrically Heated Tube Tests

NASA Technical Reports Server (NTRS)

Meyer, Michael L.; Linne, Diane L.; Rousar, Donald C.

1998-01-01

Electrically heated tube tests were conducted to characterize the critical heat flux (transition from nucleate to film boiling) of subcritical ethanol flowing at conditions relevant to the design of a regeneratively cooled rocket engine thrust chamber. The coolant was SDA-3C alcohol (95% ethyl alcohol, 5% isopropyl alcohol by weight), and tests were conducted over the following ranges of conditions: pressure from 144 to 703 psia, flow velocities from 9.7 to 77 ft/s, coolant subcooling from 33 to 362 F, and critical heat fluxes up to 8.7 BTU/in(exp 2)/sec. For the data taken near 200 psia, critical heat flux was correlated as a function of the product of velocity and fluid subcooling to within +/- 20%. For data taken at higher pressures, an additional pressure term is needed to correlate the critical heat flux. It was also shown that at the higher test pressures and/or flow rates, exceeding the critical heat flux did not result in wall burnout. This result may significantly increase the engine heat flux design envelope for higher pressure conditions.

Lessons Learned from the Construction of Upgrades to the NASA Glenn Icing Research Tunnel and Re-activation Testing

NASA Technical Reports Server (NTRS)

Sheldon, David W.; Andracchio, Charles R.; Krivanek, Thomas M.; Spera, David A.; Austinson, Todd A.

2001-01-01

Major upgrades were made in 1999 to the 6- by 9-Foot (1.8- by 2.7-m) Icing Research Tunnel (IRT) at the NASA Glenn Research Center. These included replacement of the electronic controls for the variable-speed drive motor, replacement of the heat exchanger, complete replacement and enlargement of the leg of the tunnel containing the new heat-exchanger, the addition of flow-expanding and flow-contracting turning vanes upstream and downstream of the heat exchanger, respectively, and the addition of fan outlet guide vanes (OGV's). This paper presents an overview of the construction and reactivation testing phases of the project. Important lessons learned during the technical and contract management work are documented.

Data for Regional Heat flow Studies in and around Japan and its relationship to seismogenic layer

NASA Astrophysics Data System (ADS)

Tanaka, A.

2017-12-01

Heat flow is a fundamental parameter to constrain the thermal structure of the lithosphere. It also provides a constraint to lithospheric rheology, which is sensitive to temperature. General features of the heat flow distribution in and around Japan had been revealed by the early 1970's, and heat flow data have been continuously updated by further data compilation from mainly published data and investigations. These include additional data, which were not published individually, but were included in site-specific reports. Also, thermal conductivity measurements were conducted on cores from boreholes using a line-source device with a half-space type box probe and an optical scanning device, and previously unpublished thermal conductivities were compiled. It has been more than 10 years since the last published compilation and analysis of heat flow data of Tanaka et al. (2004), which published all of the heat flow data in the northwestern Pacific area (from 0 to 60oN and from 120 to 160oE) and geothermal gradient data in and around Japan. Because these added data and information are drawn from various sources, the updated database is compiled in each datasets: heat flow, geothermal gradient, and thermal conductivity. The updated and improved database represents considerable improvement to past updates and presents an opportunity to revisit the thermal state of the lithosphere along with other geophysical/geochemical constraints on heat flow extrapolation. The spatial distribution of the cut-off depth of shallow seismicity of Japan using relocated hypocentres during the last decade (Omuralieva et al., 2012) and this updated database are used to quantify the concept of temperature as a fundamental parameter for determining the seismogenic thickness.

Cordilleran Intermontane thermotectonic history and implications for neotectonic structure and petroleum systems, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Majorowicz, Jacek; Osadetz, Kirk

2008-04-01

Heat flow increases northward along Intermontane Belt in the western Canadian Cordillera, as shown by geothermal differences between Bowser and Nechako sedimentary basins, where geothermal gradients and heat flows are ˜30 mK/m and ˜90 mW/m2 compared to ˜32 mK/m and 70 -80 mW/m2, respectively. Sparse temperature profile data from these two sedimenatary basins are consistent with an isostatic model of elevation and crustal parameters, which indicate that Bowser basin heat flow should be ˜20 mW/m2 greater than Nechako basin heat flow. Paleothermometric indicators record a significant northward increasing Eocene or older erosional denudation, up to ˜7 km. None of the heat generation, tectonic reorganization at the plate margin, or erosional denudation produce thermal effects of the type or magnitude that explain the north-south heat flow differences between Nechako and Bowser basins. The more southerly Nechako basin, where heat flow is lower, has lower mean elevation, is less deeply eroded, and lies opposite the active plate margin. In contrast, Bowser basin, where heat flow is higher, has higher mean elevation, is more deeply eroded, and sits opposite a transform margin that succeeded the active margin ˜40 Ma. Differences between Bowser and Nechako basins contrast with the tectonic history and erosion impacts on thermal state. Tectonic history and eroded sedimentary thickness suggest that Bowser basin lithosphere is cooling and contracting relative to Nechako basin lithosphere. This effect has reduced Bowser basin heat flow by ˜10-20 mW/m2 since ˜40 Ma. Neither can heat generation differences explain the northerly increasing Intermontane Belt heat flow. A lack of extensional structures in the Bowser basin precludes basin and range-like extension. Therefore, another, yet an unspecified mechanism perhaps associated with the Northern Cordilleran Volcanic Province, contributes additional heat. Bowser basin’s paleogeothermal gradients were higher, ˜36 mK/m, before the Eocene and this might affect petroleum and metallogenic systems.

46 CFR 63.25-7 - Exhaust gas boilers.

Code of Federal Regulations, 2011 CFR

2011-10-01

... results in inadequate heat transfer, a high temperature alarm or low flow alarm must be activated. An... insufficient to ensure proper heat transfer. Additionally, an audible alarm must automatically sound, and a... water level, the control system must supply the feed water at a rate sufficient to ensure proper heat...

46 CFR 63.25-7 - Exhaust gas boilers.

Code of Federal Regulations, 2010 CFR

2010-10-01

... results in inadequate heat transfer, a high temperature alarm or low flow alarm must be activated. An... insufficient to ensure proper heat transfer. Additionally, an audible alarm must automatically sound, and a... water level, the control system must supply the feed water at a rate sufficient to ensure proper heat...

Modeling of Ti-W Solidification Microstructures Under Additive Manufacturing Conditions

NASA Astrophysics Data System (ADS)

Rolchigo, Matthew R.; Mendoza, Michael Y.; Samimi, Peyman; Brice, David A.; Martin, Brian; Collins, Peter C.; LeSar, Richard

2017-07-01

Additive manufacturing (AM) processes have many benefits for the fabrication of alloy parts, including the potential for greater microstructural control and targeted properties than traditional metallurgy processes. To accelerate utilization of this process to produce such parts, an effective computational modeling approach to identify the relationships between material and process parameters, microstructure, and part properties is essential. Development of such a model requires accounting for the many factors in play during this process, including laser absorption, material addition and melting, fluid flow, various modes of heat transport, and solidification. In this paper, we start with a more modest goal, to create a multiscale model for a specific AM process, Laser Engineered Net Shaping (LENS™), which couples a continuum-level description of a simplified beam melting problem (coupling heat absorption, heat transport, and fluid flow) with a Lattice Boltzmann-cellular automata (LB-CA) microscale model of combined fluid flow, solute transport, and solidification. We apply this model to a binary Ti-5.5 wt pct W alloy and compare calculated quantities, such as dendrite arm spacing, with experimental results reported in a companion paper.

Natural convection flows and associated heat transfer processes in room fires

NASA Astrophysics Data System (ADS)

Sargent, William Stapf

This report presents the results of experimental investigations of natural convection flows and associated heat transfer processes produced by small fires in rooms with a single door or window opening. Calculation procedures have been developed to model the major aspects of these flows.Two distinct sets of experiments were undertaken.First, in a roughly 1/4 scale facility, a slightly dense solution of brine was allowed to flow into a tank of fresh water. The resulting density difference produced a flow which simulated a very small fire in a room with adiabatic walls. Second, in an approximately 1/2 scale test room, a nearly stoichioinetric mixture of air and natural gas was burned at floor level to model moderate strength fires. In this latter facility, we directly measured the heat conducted through the walls, in addition to determining the gas temperature and composition throughout the room.These two facilities complemented each other. The former offered good flow visualization and allowed us to observe the basic flow phenomena in the absence of heat transfer effects. On the other hand, the latter, which involved relatively larger fires, was a more realistic simulation of an actual room fire, and allowed us to calculate the convective heat transfer to the ceiling and walls. In addition, the stronger sources present in these 1/2 scale tests produced significant secondary flows. These secondary flows along with heat transfer effects act to modify the gas temperature or density profiles within the room from those observed in the 1/4 scale experiments.Several calculation procedures have been developed, based on the far field properties of plumes when the density differences are small (the Boussinesq approximation). The simple point source plume solution is used along with hydraulic analysis of flow through an orifice to estimate the temperatures of the hot ceiling layer gas and of the cooler floor zone fluid, as well as the height of the interface between them. A finite source plume model is combined with conservation equations across the interface to compute the evolution of the plume above the interface. This calculation then provides the starting point for an integral analysis of the flow and heat transfer in the turbulent ceiling jet.The computed results both for the average floor and ceiling zone gas temperatures, and for the connective heat transfer in the ceiling jet agreed reasonably well with our experimental data. This agreement suggests that our computational procedures can be applied to answer practical questions, such as whether the connective heat flux from a given fire in a real room would be sufficient to trigger sprinklers or other detection systems in a given amount of time.

Thermal Investigation in the Cappadocia Region, Central Anatolia-Turkey, Analyzing Curie Point Depth, Geothermal Gradient, and Heat-Flow Maps from the Aeromagnetic Data

NASA Astrophysics Data System (ADS)

Bilim, Funda; Kosaroglu, Sinan; Aydemir, Attila; Buyuksarac, Aydin

2017-12-01

In this study, curie point depth (CPD), heat flow, geothermal gradient, and radiogenic heat production maps of the Cappadocian region in central Anatolia are presented to reveal the thermal structure from the aeromagnetic data. The large, circular pattern in these maps matches with previously determined shallow (2 km in average) depression. Estimated CPDs in this depression filled with loose volcano-clastics and ignimbrite sheets of continental Neogene units vary from 7 to 12 km, while the geothermal gradient increases from 50 to 68 °C/km. Heat flows were calculated using two different conductivity coefficients of 2.3 and 2.7 Wm-1 K-1. The radiogenic heat production was also obtained between 0.45 and 0.70 μW m-3 in this area. Heat-flow maps were compared with the previous, regional heat-flow map of Turkey and significant differences were observed. In contrast to linear heat-flow increment through the northeast in the previous map in the literature, produced maps in this study include a large, caldera-like circular depression between Nevsehir, Aksaray, Nigde, and Yesilhisar cities indicating high geothermal gradient and higher heat-flow values. In addition, active deformation is evident with young magmatism in the Neogene and Quaternary times and a large volcanic cover on the surface. Boundaries of volcanic eruption centers and buried large intrusions are surrounded with the maxspots of the horizontal gradients of magnetic anomalies. Analytic signal (AS) map pointing-out exact locations of causative bodies is also presented in this study. Circular region in the combined map of AS and maxspots apparently indicates a possible caldera.

CFD analyses of coolant channel flowfields

NASA Technical Reports Server (NTRS)

Yagley, Jennifer A.; Feng, Jinzhang; Merkle, Charles L.

1993-01-01

The flowfield characteristics in rocket engine coolant channels are analyzed by means of a numerical model. The channels are characterized by large length to diameter ratios, high Reynolds numbers, and asymmetrical heating. At representative flow conditions, the channel length is approximately twice the hydraulic entrance length so that fully developed conditions would be reached for a constant property fluid. For the supercritical hydrogen that is used as the coolant, the strong property variations create significant secondary flows in the cross-plane which have a major influence on the flow and the resulting heat transfer. Comparison of constant and variable property solutions show substantial differences. In addition, the property variations prevent fully developed flow. The density variation accelerates the fluid in the channels increasing the pressure drop without an accompanying increase in heat flux. Analyses of the inlet configuration suggest that side entry from a manifold can affect the development of the velocity profile because of vortices generated as the flow enters the channel. Current work is focused on studying the effects of channel bifurcation on the flow field and the heat transfer characteristics.

Two-dimensional numerical simulation of a Stirling engine heat exchanger

NASA Technical Reports Server (NTRS)

Ibrahim, Mounir B.; Tew, Roy C.; Dudenhoefer, James E.

1989-01-01

The first phase of an effort to develop multidimensional models of Stirling engine components is described; the ultimate goal is to model an entire engine working space. More specifically, parallel plate and tubular heat exchanger models with emphasis on the central part of the channel (i.e., ignoring hydrodynamic and thermal end effects) are described. The model assumes: laminar, incompressible flow with constant thermophysical properties. In addition, a constant axial temperature gradient is imposed. The governing equations, describing the model, were solved using Crank-Nicloson finite-difference scheme. Model predictions were compared with analytical solutions for oscillating/reversing flow and heat transfer in order to check numerical accuracy. Excellent agreement was obtained for the model predictions with analytical solutions available for both flow in circular tubes and between parallel plates. Also the heat transfer computational results are in good agreement with the heat transfer analytical results for parallel plates.

Increasing EDV Range through Intelligent Cabin Air Handling Strategies: Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leighton, Daniel; Rugh, John

Computational fluid dynamics (CFD) simulations of a Ford Focus Electric demonstrated that a split flow heating, ventilating and air conditioning (HVAC) system with rear recirculation ducts can reduce cabin heating loads by up to 57.4% relative to full fresh air usage under some conditions (steady state, four passengers, ambient temperature of -5 deg C). Simulations also showed that implementing a continuous recirculation fraction control system into the original equipment manufacturer (OEM) HVAC system can reduce cabin heating loads by up to 50.0% relative to full fresh air usage under some conditions (steady state, four passengers, ambient temperature of -5 degmore » C). Identified that continuous fractional recirculation control of the OEM system can provide significant energy savings for EVs at minimal additional cost, while a split flow HVAC system with rear recirculation ducts only provides minimal additional improvement at significant additional cost.« less

Liquid-Vapor Flow Regime Transitions for Spacecraft Heat Transfer Loops

DTIC Science & Technology

1988-12-01

effects of fluid properties on flow regime transitions. 5 A carnauba wax with no additives was used because it resists dissolution by oil. 19 4.2...importance of an annular flow entrance geometry and of waxing the tube wall to change its wetting properties (to prevent inverse annular flow) were

TOUGH Simulations of the Updegraff's Set of Fluid and Heat Flow Problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moridis, G.J.; Pruess

1992-11-01

The TOUGH code [Pruess, 1987] for two-phase flow of water, air, and heat in penneable media has been exercised on a suite of test problems originally selected and simulated by C. D. Updegraff [1989]. These include five 'verification' problems for which analytical or numerical solutions are available, and three 'validation' problems that model laboratory fluid and heat flow experiments. All problems could be run without any code modifications (*). Good and efficient numerical performance, as well as accurate results were obtained throughout. Additional code verification and validation problems from the literature are briefly summarized, and suggestions are given for propermore » applications of TOUGH and related codes.« less

The magnetic-nanofluid heat pipe with superior thermal properties through magnetic enhancement

PubMed Central

2012-01-01

This study developed a magnetic-nanofluid (MNF) heat pipe (MNFHP) with magnetically enhanced thermal properties. Its main characteristic was additional porous iron nozzle in the evaporator and the condenser to form a unique flowing pattern of MNF slug and vapor, and to magnetically shield the magnet attraction on MNF flowing. The results showed that an optimal thermal conductivity exists in the applied field of 200 Oe. Furthermore, the minor thermal performance of MNF at the condenser limited the thermal conductivity of the entire MNFHP, which was 1.6 times greater than that filled with water for the input power of 60 W. The feasibilities of an MNFHP with the magnetically enhanced heat transfer and the ability of vertical operation were proved for both a promising heat-dissipation device and the energy architecture integrated with an additional energy system. PMID:22716909

A comparative study on heat and mass transfer of the Blasius and Falkner-Skan flow of a bio-convective Casson fluid past a wedge

NASA Astrophysics Data System (ADS)

Raju, C. S. K.; Sandeep, N.

2016-11-01

Nowadays, many theoretical models are available for analyzing the heat and mass transfer of flows through different geometries. Nevertheless, it is challenging for researchers to choose among these models, the most suitable for a particular geometry. In addition to this, the extrinsic magnetic field is capable to set the thermal and physical properties of magnetic fluids and regulate the flow and heat transfer characteristics. The strength of the applied magnetic field affects the thermal conductivity of the fluids and makes it anisotropic. With this incentive, we attempt to study the thermophoresis and Brownian motion effects on the magnetohydrodynamic radiative Casson fluid flow over a wedge filled with gyrotactic microorganisms by considering the Blasius and Falkner-Skan models. Numerical solutions are offered graphically as well as in tabular form with the aid of Runge-Kutta and Newton's methods. Results for Blasius and Falkner-Skan flow cases are exhibited through plots for the parameters of concern. For real life applications, we also calculated the heat and mass transfer rates. It is observed that thermal and concentration boundary layers are not uniform for Falkner-Skan and Blasius flow cases. It is also observed that the heat and mass transfer rate is high in Falkner-Skan flow when compared with Blasius flow.

Chip calorimetry for evaluation of biofilm treatment with biocides, antibiotics, and biological agents.

PubMed

Morais, Frida Mariana; Buchholz, Friederike; Maskow, Thomas

2014-01-01

Any growth or bioconversion in biofilms is accompanied by the release of heat. The heat (in J) is tightly related to the stoichiometry of the respective process via law of Hess, and the heat production rate (in W or J/s) is additionally related to the process kinetics. This heat and the heat production rate can nowadays be measured by modern calorimetry with extremely high sensitivity. Flow-through calorimetry allows the measurement of bioprocesses in biofilms in real time, without the need of invasive sample preparation and disturbing of biofilm processes. Furthermore, it can be applied for long-term measurements and is even applicable to turbid media. Chip or miniaturized calorimeters have the additional advantages of extremely short thermal equilibration times and the requirement of very small amounts of media and chemicals. The precision of flow-through chip calorimeters (about 3 mW/L) allows the detection of early stages of biofilm development (about 10(5) bacteria cm(-2)).

Heat Production as a Tool in Geothermal Exploration

NASA Astrophysics Data System (ADS)

Rhodes, J. M.; Koteas, C.; Mabee, S. B.; Thomas, M.; Gagnon, T.

2012-12-01

Heat flow data (together with knowledge, or assumptions, of stratigraphy, thermal conductivity and heat production) provide the prime parameter for estimating the potential of geothermal resources. Unfortunately this information is expensive to obtain as it requires deep boreholes. Consequently it is sparse or lacking in areas not traditionally considered as having geothermal potential. New England (and most of the northeastern U.S.A.) is one such area. However, in the absence of volcano-derived hydrothermal activity with its attendant high heat flow, granitic plutons provide an alternative geothermal resource. Compared with other crustal rocks, granites contain higher concentrations of heat-producing elements (K, U, Th). Additionally, they are relatively homogeneous, compared to surrounding country rock, allowing for stimulation through hydro-fracking of large (>1 km3) geothermal reservoirs. Consequently we have adopted a different approach, obtaining heat production data rather then relying on the very sparse heat flow data. Birch and colleagues long since recognized the relationship between heat flow and heat production as an integral part of their concept of Heat Flow Provinces. Heat production is readily determined in the laboratory by measuring the density of a sample and the concentrations of its heat-producing elements potassium, uranium and thorium. We have determined the heat production for 570 samples from most of the major granitic and gneissic bodies in Massachusetts and Connecticut. We have also measured these parameters for 70 sedimentary rocks that cover granites and gneiss in the Connecticut and Narragansett Basins. This data is being used to calculate inferred heat flow data for these localities. Comparison of these inferred heat flow values with the sparse number of those measured directly in boreholes in the two States is encouraging, indicating that this approach has merit. We have also measured thermal conductivity on all of these samples. This, together with the measured heat production and the inferred heat flow allow the calculation of inferred temperature - depth profiles for these localities, from which we have produced maps showing the distribution of heat production, thermal conductivity, inferred heat flow and inferred temperatures at depths of 2, 4 and 6 km in the two States. We believe that this is a rapid and relatively cheap approach for evaluating the geothermal potential of a region lacking in heat flow data allowing identification of areas that warrant more detailed investigation which would include geophysical surveys and drilling. In Massachusetts and Connecticut such areas include the Fitchburg pluton, Permian granites and the Narragansett and Hartford Basins, where gneiss and granites are buried beneath Carboniferous and Triassic sediments respectively. This project is funded by the Department of Energy through an award to the Association of American State Geologists.

Desktop Systems for Manufacturing Carbon Nanotube Films by Chemical Vapor Deposition

DTIC Science & Technology

2007-06-01

existing low cost tube furnace designs limit the researcher’s ability to fully separate critical reaction parameters such as temperature and flow...Often heated using an external resistive heater coil, a typical configuration, shown in Figure 4, might place a tube made of a non- reactive ...researcher’s ability to fully separate critical parameters such as temperature and flow profiles. Additionally, the use of heating elements external to

A generalized one-dimensional computer code for turbomachinery cooling passage flow calculations

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Roelke, Richard J.; Meitner, Peter L.

1989-01-01

A generalized one-dimensional computer code for analyzing the flow and heat transfer in the turbomachinery cooling passages was developed. This code is capable of handling rotating cooling passages with turbulators, 180 degree turns, pin fins, finned passages, by-pass flows, tip cap impingement flows, and flow branching. The code is an extension of a one-dimensional code developed by P. Meitner. In the subject code, correlations for both heat transfer coefficient and pressure loss computations were developed to model each of the above mentioned type of coolant passages. The code has the capability of independently computing the friction factor and heat transfer coefficient on each side of a rectangular passage. Either the mass flow at the inlet to the channel or the exit plane pressure can be specified. For a specified inlet total temperature, inlet total pressure, and exit static pressure, the code computers the flow rates through the main branch and the subbranches, flow through tip cap for impingement cooling, in addition to computing the coolant pressure, temperature, and heat transfer coefficient distribution in each coolant flow branch. Predictions from the subject code for both nonrotating and rotating passages agree well with experimental data. The code was used to analyze the cooling passage of a research cooled radial rotor.

Design and simulation of heat exchangers using Aspen HYSYS, and Aspen exchanger design and rating for paddy drying application

NASA Astrophysics Data System (ADS)

Janaun, J.; Kamin, N. H.; Wong, K. H.; Tham, H. J.; Kong, V. V.; Farajpourlar, M.

2016-06-01

Air heating unit is one of the most important parts in paddy drying to ensure the efficiency of a drying process. In addition, an optimized air heating unit does not only promise a good paddy quality, but also save more for the operating cost. This study determined the suitable and best specifications heating unit to heat air for paddy drying in the LAMB dryer. In this study, Aspen HYSYS v7.3 was used to obtain the minimum flow rate of hot water needed. The resulting data obtained from Aspen HYSYS v7.3 were used in Aspen Exchanger Design and Rating (EDR) to generate heat exchanger design and costs. The designs include shell and tubes and plate heat exchanger. The heat exchanger was designed in order to produce various drying temperatures of 40, 50, 60 and 70°C of air with different flow rate, 300, 2500 and 5000 LPM. The optimum condition for the heat exchanger were found to be plate heat exchanger with 0.6 mm plate thickness, 198.75 mm plate width, 554.8 mm plate length and 11 numbers of plates operating at 5000 LPM air flow rate.

Heat transfer and pressure drop measurements in an air/molten salt direct-contact heat exchanger

NASA Astrophysics Data System (ADS)

Bohn, Mark S.

1988-11-01

This paper presents a comparison of experimental data with a recently published model of heat exchange in irrigated packed beds. Heat transfer and pressure drop were measured in a 150 mm (ID) column with a 610 mm bed of metal Pall rings. Molten nitrate salt and preheated air were the working fluids with a salt inlet temperature of approximately 440 C and air inlet temperatures of approximately 230 C. A comparison between the experimental data and the heat transfer model is made on the basis of heat transfer from the salt. For the range of air and salt flow rates tested, 0.3 to 1.2 kg/sq m/s air flow and 6 to 18 kg/sq m/s salt flow, the data agree with the model within 22 percent standard deviation. In addition, a model for the column pressure drop was validated, agreeing with the experimental data within 18 percent standard deviation over the range of column pressure drop from 40 to 1250 Pa/m.

An improved algorithm for the modeling of vapor flow in heat pipes

NASA Technical Reports Server (NTRS)

Tower, Leonard K.; Hainley, Donald C.

1989-01-01

A heat pipe vapor flow algorithm suitable for use in codes on microcomputers is presented. The incompressible heat pipe vapor flow studies of Busse are extended to incorporate compressibility effects. The Busse velocity profile factor is treated as a function of temperature and pressure. The assumption of a uniform saturated vapor temperature determined by the local pressure at each cross section of the pipe is not made. Instead, a mean vapor temperature, defined by an energy integral, is determined in the course of the solution in addition to the pressure, saturation temperature at the wall, and the Busse velocity profile factor. For alkali metal working fluids, local species equilibrium is assumed. Temperature and pressure profiles are presented for several cases involving sodium heat pipes. An example for a heat pipe with an adiabatic section and two evaporators in sequence illustrates the ability to handle axially varying heat input. A sonic limit plot for a short evaporator falls between curves for the Busse and Levy inviscid sonic limits.

An improved algorithm for the modeling of vapor flow in heat pipes

NASA Astrophysics Data System (ADS)

Tower, Leonard K.; Hainley, Donald C.

1989-12-01

A heat pipe vapor flow algorithm suitable for use in codes on microcomputers is presented. The incompressible heat pipe vapor flow studies of Busse are extended to incorporate compressibility effects. The Busse velocity profile factor is treated as a function of temperature and pressure. The assumption of a uniform saturated vapor temperature determined by the local pressure at each cross section of the pipe is not made. Instead, a mean vapor temperature, defined by an energy integral, is determined in the course of the solution in addition to the pressure, saturation temperature at the wall, and the Busse velocity profile factor. For alkali metal working fluids, local species equilibrium is assumed. Temperature and pressure profiles are presented for several cases involving sodium heat pipes. An example for a heat pipe with an adiabatic section and two evaporators in sequence illustrates the ability to handle axially varying heat input. A sonic limit plot for a short evaporator falls between curves for the Busse and Levy inviscid sonic limits.

Flamelet Formation In Hele-Shaw Flow

NASA Technical Reports Server (NTRS)

Wichman, I. S.; Olson, S. L.

2003-01-01

A Hele-Shaw flow apparatus constructed at Michigan State University (MSU) produces conditions that reduce influences of buoyancy-driven flows. In addition, in the MSU Hele-Shaw apparatus it is possible to adjust the heat losses from the fuel sample (0.001 in. thick cellulose) and the flow speed of the approaching oxidizer flow (air) so that the "flamelet regime of flame spread" is entered. In this regime various features of the flame-to-smolder (and vice versa) transition can be studied. For the relatively wide (approx. 17.5 cm) and long (approx. 20 cm) samples used, approximately ten flamelets existed at all times. The flamelet behavior was studied mechanistically and statistically. A heat transfer analysis of the dominant heat transfer mechanisms was conducted. Results indicate that radiation and conduction processes are important, and that a simple 1-D model using the Broido-Shafizadeh model for cellulose decomposition chemistry can describe aspects of the flamelet spread process. Introduction

Inverting multiple suites of thermal indicator data to constrain the heat flow history: A case study from east Kalimantan, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mudford, B.S.

1996-12-31

The determination of an appropriate thermal history in an exploration area is of fundamental importance when attempting to understand the evolution of the petroleum system. In this talk we present the results of a single-well modelling study in which bottom hole temperature data, vitrinite reflectance data and three different biomarker ratio datasets were available to constrain the modelling. Previous modelling studies using biomarker ratios have been hampered by the wide variety of published kinetic parameters for biomarker evolution. Generally, these parameters have been determined either from measurements in the laboratory and extrapolation to the geological setting, or from downhole measurementsmore » where the heat flow history is assumed to be known. In the first case serious errors can arise because the heating rate is being extrapolated over many orders of magnitude, while in the second case errors can arise if the assumed heat flow history is incorrect. To circumvent these problems we carried out a parameter optimization in which the heat flow history was treated as an unknown in addition to the biomarker ratio kinetic parameters. This method enabled the heat flow history for the area to be determined together with appropriate kinetic parameters for the three measured biomarker ratios. Within the resolution of the data, the heat flow since the early Miocene has been relatively constant at levels required to yield good agreement between predicted and measured subsurface temperatures.« less

Inverting multiple suites of thermal indicator data to constrain the heat flow history: A case study from east Kalimantan, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mudford, B.S.

1996-01-01

The determination of an appropriate thermal history in an exploration area is of fundamental importance when attempting to understand the evolution of the petroleum system. In this talk we present the results of a single-well modelling study in which bottom hole temperature data, vitrinite reflectance data and three different biomarker ratio datasets were available to constrain the modelling. Previous modelling studies using biomarker ratios have been hampered by the wide variety of published kinetic parameters for biomarker evolution. Generally, these parameters have been determined either from measurements in the laboratory and extrapolation to the geological setting, or from downhole measurementsmore » where the heat flow history is assumed to be known. In the first case serious errors can arise because the heating rate is being extrapolated over many orders of magnitude, while in the second case errors can arise if the assumed heat flow history is incorrect. To circumvent these problems we carried out a parameter optimization in which the heat flow history was treated as an unknown in addition to the biomarker ratio kinetic parameters. This method enabled the heat flow history for the area to be determined together with appropriate kinetic parameters for the three measured biomarker ratios. Within the resolution of the data, the heat flow since the early Miocene has been relatively constant at levels required to yield good agreement between predicted and measured subsurface temperatures.« less

Studies on heat transfer and pressure drop in turbulent flow of silver - water nanofluids through a circular tube at constant wall heat flux

NASA Astrophysics Data System (ADS)

Iyahraja, S.; Rajadurai, J. Selwin; Rajesh, S.; Pandian, R. Seeni Thangaraj; Kumaran, M. Selva; Selvakumar, G.

2018-07-01

In the present study, performance of convective heat transfer and friction factor of silver-water nanofluids in a horizontal circular pipe under turbulent flow were investigated experimentally under uniform heat flux condition. The volume concentration of silver nanoparticles is varied as 0.01, 0.05 and 0.1%. Heat transfer coefficient and friction factor of nanofluids were measured experimentally by varying the Reynolds number from 3000 to 21,000. It is observed that the addition of even low volume fraction of silver nanoparticles increases both Nusselt number and heat transfer coefficient of the nanofluid significantly. Nusselt number of silver-water nanofluid increases up to 32.6% for 0.1% volume fraction at Reynolds number of 21,000. However, the addition of nanoparticles in the base fluid increases the friction factor slightly. New empirical correlations are also proposed for the estimation of Nusselt number and friction factor of silver-water nanofluid based on the data of present experimental investigation. The proposed correlations of Nusselt number and friction factor show good agreement with their experimental data.

Studies on heat transfer and pressure drop in turbulent flow of silver - water nanofluids through a circular tube at constant wall heat flux

NASA Astrophysics Data System (ADS)

Iyahraja, S.; Rajadurai, J. Selwin; Rajesh, S.; Pandian, R. Seeni Thangaraj; Kumaran, M. Selva; Selvakumar, G.

2018-02-01

In the present study, performance of convective heat transfer and friction factor of silver-water nanofluids in a horizontal circular pipe under turbulent flow were investigated experimentally under uniform heat flux condition. The volume concentration of silver nanoparticles is varied as 0.01, 0.05 and 0.1%. Heat transfer coefficient and friction factor of nanofluids were measured experimentally by varying the Reynolds number from 3000 to 21,000. It is observed that the addition of even low volume fraction of silver nanoparticles increases both Nusselt number and heat transfer coefficient of the nanofluid significantly. Nusselt number of silver-water nanofluid increases up to 32.6% for 0.1% volume fraction at Reynolds number of 21,000. However, the addition of nanoparticles in the base fluid increases the friction factor slightly. New empirical correlations are also proposed for the estimation of Nusselt number and friction factor of silver-water nanofluid based on the data of present experimental investigation. The proposed correlations of Nusselt number and friction factor show good agreement with their experimental data.

Water/Ice Heat Sink With Quick-Connect Couplings

NASA Technical Reports Server (NTRS)

Lomax, Curtis; Webbon, Bruce

1996-01-01

Report presents additional detailed information on apparatus described in "Direct-Interface, Fusible Heat Sink" (ARC-11920). Describes entire apparatus, with special emphasis on features of quick-disconnect couplings governing flow of water under various operating conditions and plumbing configuration.

Fluid-flow pressure measurements and thermo-fluid characterization of a single loop two-phase passive heat transfer device

NASA Astrophysics Data System (ADS)

Ilinca, A.; Mangini, D.; Mameli, M.; Fioriti, D.; Filippeschi, S.; Araneo, L.; Roth, N.; Marengo, M.

2017-11-01

A Novel Single Loop Pulsating Heat Pipe (SLPHP), with an inner diameter of 2 mm, filled up with two working fluids (Ethanol and FC-72, Filling Ratio of 60%), is tested in Bottom Heated mode varying the heating power and the orientation. The static confinement diameter for Ethanol and FC-72, respectively 3.4 mm and 1.7mm, is above and slightly under the inner diameter of the tube. This is important for a better understanding of the working principle of the device very close to the limit between the Loop Thermosyphon and Pulsating Heat Pipe working modes. With respect to previous SLPHP experiments found in the literature, such device is designed with two transparent inserts mounted between the evaporator and the condenser allowing direct fluid flow visualization. Two highly accurate pressure transducers permit local pressure measurements just at the edges of one of the transparent inserts. Additionally, three heating elements are controlled independently, so as to vary the heating distribution at the evaporator. It is found that peculiar heating distributions promote the slug/plug flow motion in a preferential direction, increasing the device overall performance. Pressure measurements point out that the pressure drop between the evaporator and the condenser are related to the flow pattern. Furthermore, at high heat inputs, the flow regimes recorded for the two fluids are very similar, stressing that, when the dynamic effects start to play a major role in the system, the device classification between Loop Thermosyphon and Pulsating Heat Pipe is not that sharp anymore.

Numerical Modeling of Conjugate Heat Transfer in Fluid Network

NASA Technical Reports Server (NTRS)

Majumdar, Alok

2004-01-01

Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.

Relationships between heat flow, thermal and pressure fields in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Husson, L.; Henry, P.; Le Pichon, X.

2004-12-01

The thermal field of the Gulf of Mexico (GoM) is restored from a comprehensive temperature-depth database. A striking feature is the systematic sharp gradient increase between 2500 and 4000 m. The analysis of the pressure (fracturation tests and mud weights) indicates a systematic correlation between the pressure and temperature fields, as well as with the thickness of Plio-Pleistocene sedimentary layer, and is interpreted as the fact of cooling from fluid flow in the upper, almost hydrostatically pressured layer. The Nusselt number, that we characterize by the ratio between the near high-P gradient over low-P gradient varies spatially and is correlated to the structural pattern of the GoM; this observation outlines the complex relationships between heat and fluid flows, structure and sedimentation. The deep thermal signal is restored in terms of gradient and heat flow density from a statistical analysis of the thermal data combined to the thermal modelling of about 175 wells. At a regional scale, although the sedimentary cover is warmer in Texas than in Louisiana in terms of temperature, the steady state basal heat flow is higher in Louisiana. In addition, beneath the Corsair Fault, which lay offshore parallel to the Texan coast, the high heat flow suggests a zone of Tertiary lithospheric thinning.

Investigation of powder injection moulded oblique fin heat sinks

NASA Astrophysics Data System (ADS)

Sai, Vadri Siva

The present work attempts to study the fluid flow and heat transfer characteristics of PIM oblique finned microchannel heat sink both numerically and experimentally. Experimental results such as thermal resistance and pressure drop have been well validated with ANSYS FLUENT simulations. Hot spots are observed at the most downstream location of the channel is due to the effect of flow migration. Finally, a novel technique has been proposed to reduce the pressure drop on creating additional channels by removing some material at the middle portion of oblique fins. It is found that the creation of oblique cuts incurred a reduction in both pressure drop and Nuavg up to 31.36 % and 16.66 % respectively at a flow rate of 500 ml/min. Nevertheless, for all the flowrates considered in this analysis. % reduction in pressure drop is almost double as compared with % reduction in Nuavg. Therefore, this analysis is beneflcial in reducing the additional cost incurs due to pressure drop penalty.

Standing shocks in a two-fluid solar wind

NASA Technical Reports Server (NTRS)

Habbal, Shadia R.; Hu, You Qiu; Esser, Ruth

1994-01-01

We present a numerical study of the formation of standing shocks in the solar wind using a two-fluid time-dependent model in the presence of Alfven waves. Included in this model is the adiabatic cooling and thermal conduction of both electrons and protons. In this study, standing shocks develop in the flow when additional critical points form as a result of either localized momentum addition or rapid expansion of the flow tube below the existing sonic point. While the flow speed and density exhibit the same characteristics as found in earlier studies of the formation of standing shocks, the inclusion of electron and proton heat conduction produces different signatures in the electron and proton temperature profiles across the shock layer. Owing to the strong heat conduction, the electron temperature is nearly continuous across the shock, but its gradient has a negative jump across it, thus producing a net heat flux out of the shock layer. The proton temperature exhibits the same characteristics for shocks produced by momentum addition but behaves differently when the shock is formed by the rapid divergence of the flow tube. The adiabatic cooling in a rapidly diverging flow tube reduces the proton temperature so substantially that the proton heat conduction becomes negligible in the vicinity of the shock. As a result, protons experience a positive jump in temperature across the shock. While Alfven waves do not affect the formation of standing shocks, they contribute to the change of the mmomentum and energy balance across them. We also find that for this solar wind model the inclusion of thermal conduction and adiabatic cooling for the elctrons and protons increases significantly the range of parameters characterizing the formation of standing shocks over those previously found for isothermal and polytropic models.

Cold Heat Storage Characteristics of O/W-type Latent Heat Emulsion Including Continuum Phase of Water Treated with a Freezing Point Depression

NASA Astrophysics Data System (ADS)

Inaba, Hideo; Morita, Shin-Ichi

This paper deals with flow and cold heat storage characteristics of the oil (tetradecane, C14H30, freezing point 278.9 K, Latent heat 229 kJ/kg)/water emulsion as a latent heat storage material having a low melting point. The test emulsion includes a water-urea solution as a continuum phase. The freezing point depression of the continuum phase permits enhancement of the heat transfer rate of the emulison, due to the large temperature difference between the latent heat storage material and water-urea solution. The velocity of emulsion flow and the inlet temperature of coolant in a coiled double tube heat exchanger are chosen as the experimental parameters. The pressure drop, the heat transfer coefficient of the emulsion in the coiled tube are measured in the temperture region over solid and liquid phase of the latent heat storage material. The finishing time of the cold heat storage is defined experimentally in the range of sensible and latent heat storage. It is clarified that the flow behavior of the emulsion as a non-Newtonian fluid has an important role in cold heat storage. The useful nondimentional correlation equations for the additional pressure loss coefficient, the heat transfer coefficient and the finishing time of the cold heat storage are derived in terms of Dean number and heat capacity ratio.

Boiling local heat transfer enhancement in minichannels using nanofluids

PubMed Central

2013-01-01

This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445

EFFECT OF OXYGEN ADDITION ON POLYCYCLIC AROMATIC HYDROCARBON FORMATION IN 1,3 BUTADIENE COUNTER-FLOW DIFFUSION FLAMES. (R828193)

EPA Science Inventory

The effect of 3% O₂ addition to the fuel on detailed chemical structure of a 1,3 butadiene counter-flow diffusion flame has been investigated by using heated microprobe sampling and online gas chromatography mass spectrometry. Centerline gas temperature and species ...

Heat flow, seismic cut-off depth and thermal modeling of the Fennoscandian Shield

NASA Astrophysics Data System (ADS)

Veikkolainen, Toni; Kukkonen, Ilmo T.; Tiira, Timo

2017-12-01

Being far from plate boundaries but covered with seismograph networks, the Fennoscandian Shield features an ideal test laboratory for studies of intraplate seismicity. For this purpose, this study applies 4190 earthquake events from years 2000-2015 with magnitudes ranging from 0.10 to 5.22 in Finnish and Swedish national catalogues. In addition, 223 heat flow determinations from both countries and their immediate vicinity were used to analyse the potential correlation of earthquake focal depths and the spatially interpolated heat flow field. Separate subset analyses were performed for five areas of notable seismic activity: the southern Gulf of Bothnia coast of Sweden (area 1), the northern Gulf of Bothnia coast of Sweden (area 2), the Swedish Norrbotten and western Finnish Lapland (area 3), the Kuusamo region of Finland (area 4) and the southernmost Sweden (area 5). In total, our subsets incorporated 3619 earthquake events. No obvious relation of heat flow and focal depth exists, implying that variations of heat flow are primarily caused by shallow lying heat producing units instead of deeper sources. This allows for construction of generic geotherms for the range of representative palaeoclimatically corrected (steady-state) surface heat flow values (40-60 mW m-2). The 1-D geotherms constructed for a three-layer crust and lithospheric upper mantle are based on mantle heat flow constrained with the aid of mantle xenolith thermobarometry (9-15 mW m-2), upper crustal heat production values (3.3-1.1 μWm-3) and the brittle-ductile transition temperature (350 °C) assigned to the cut-off depth of seismicity (28 ± 4 km). For the middle and lower crust heat production values of 0.6 and 0.2 μWm-3 were assigned, respectively. The models suggest a Moho temperature range of 460-500 °C.

Study of Polyurethane Foaming Dynamics Using a Heat Flow Meter

NASA Astrophysics Data System (ADS)

Koniorczyk, P.; Trzyna, M.; Zmywaczyk, J.; Zygmunt, B.; Preiskorn, M.

2017-05-01

This work presents the results of the study concerning the effects of fillers addition on the heat flux density \\dot{q}( t ) of foaming of polyurethane-polystyrene porous composite (PSUR) and describes the dynamics of this process during the first 600 s. This foaming process resulted in obtaining porous materials that were based on HFC 365/225 blown rigid polyurethane foam (PUR) matrix, which contained thermoplastic expandable polystyrene (EPS) beads as the filler. In PSUR composites, the EPS beads were expanded after being heated to a temperature above the glass transition temperature of EPS and vaporing gas incorporated inside, by using the heat of exothermic reaction of polyol with isocyanate. From the start (t=0) to the end of the PSUR composite foaming process (t=tk), \\dot{q}( t ) was measured with the use of the heat flow meter. For the purpose of the study two PUR systems were selected: one with high and one with low heat density of foaming process q. EPS beads were selected from the same manufacturer with large and small diameter. The mass fraction of EPS in PSUR foam varied during the measurements. Additionally, a study of volume fractions of expanded EPS phase in PSUR foams as a function of mass fractions of EPS was conducted. In order to verify effects of the EPS addition on the heat flux density during PSUR foaming process, the thermal conductivity measurements were taken.

Flow and Thermal Performance of a Water-Cooled Periodic Transversal Elliptical Microchannel Heat Sink for Chip Cooling.

PubMed

Wei, Bo; Yang, Mo; Wang, Zhiyun; Xu, Hongtao; Zhang, Yuwen

2015-04-01

Flow and thermal performance of transversal elliptical microchannels were investigated as a passive scheme to enhance the heat transfer performance of laminar fluid flow. The periodic transversal elliptical micro-channel is designed and its pressure drop and heat transfer characteristics in laminar flow are numerically investigated. Based on the comparison with a conventional straight micro- channel having rectangular cross section, it is found that periodic transversal elliptical microchannel not only has great potential to reduce pressure drop but also dramatically enhances heat transfer performance. In addition, when the Reynolds number equals to 192, the pressure drop of the transversal elliptical channel is 36.5% lower than that of the straight channel, while the average Nusselt number is 72.8% higher; this indicates that the overall thermal performance of the periodic transversal elliptical microchannel is superior to the conventional straight microchannel. It is suggested that such transversal elliptical microchannel are attractive candidates for cooling future electronic chips effectively with much lower pressure drop.

Cooling Performance of Additively Manufactured Microchannels and Film Cooling Holes

NASA Astrophysics Data System (ADS)

Stimpson, Curtis K.

Additive manufacturing (AM) enables fabrication of components that cannot be made with any other manufacturing method. Significant advances in metal-based AM systems have made this technology feasible for building production parts to be used use in commercial products. In particular, the gas turbine industry benefits from AM as a manufacturing technique especially for development of components subjected to high heat flux. It has been shown that the use of microchannels in high heat flux components can lead to more efficient cooling designs than those that presently exist. The current manufacturing methods have prevented the use of microchannels in such parts, but AM now makes them manufacturable. However, before such designs can become a reality, much research must be done to characterize impacts on flow and heat transfer of AM parts. The current study considers the effect on flow and heat transfer through turbine cooling features made with AM. Specifically, the performance of microchannels and film cooling holes made with laser powder bed fusion (L-PBF) is assessed. A number of test coupons containing microchannels were built from high temperature alloy powders on a commercially available L-PBF machine. Pressure drop and heat transfer experiments characterized the flow losses and convective heat transfer of air passing through the channels at various Reynolds numbers and Mach numbers. The roughness of the channels' surfaces was characterized in terms of statistical roughness parameters; the morphology of the roughness was examined qualitatively. Magnitude and morphology of surface roughness found on AM parts is unlike any form of roughness seen in the literature. It was found that the high levels of roughness on AM surfaces result in markedly augmented pressure loss and heat transfer at all Reynolds numbers, and conventional flow and heat transfer correlations produce erroneous estimates. The physical roughness measurements made in this study were correlated to flow and heat transfer measurements to generate a predictive model for flow through AM microchannels. The flow compressibility was also found to play a significant role in flow loss through these channels. Overall effectiveness of film cooling combined with the internal microchannel flow was examined in a conjugate experimental setup. The validity of the experimental conditions was established by matching important dimensionless parameters of the experimental setup to common values found in turbine engines. These results showed that the roughness in the film cooling holes produced higher in-hole convection than those made with current manufacturing methods. The roughness in the holes also repressed the film performance. However, high relative roughness was shown to minimize the impact of coolant feed direction on the film effectiveness of the AM holes.

Numerical study of entropy generation due to coupled laminar and turbulent mixed convection and thermal radiation in an enclosure filled with a semitransparent medium.

PubMed

Goodarzi, M; Safaei, M R; Oztop, Hakan F; Karimipour, A; Sadeghinezhad, E; Dahari, M; Kazi, S N; Jomhari, N

2014-01-01

The effect of radiation on laminar and turbulent mixed convection heat transfer of a semitransparent medium in a square enclosure was studied numerically using the Finite Volume Method. A structured mesh and the SIMPLE algorithm were utilized to model the governing equations. Turbulence and radiation were modeled with the RNG k-ε model and Discrete Ordinates (DO) model, respectively. For Richardson numbers ranging from 0.1 to 10, simulations were performed for Rayleigh numbers in laminar flow (10⁴) and turbulent flow (10⁸). The model predictions were validated against previous numerical studies and good agreement was observed. The simulated results indicate that for laminar and turbulent motion states, computing the radiation heat transfer significantly enhanced the Nusselt number (Nu) as well as the heat transfer coefficient. Higher Richardson numbers did not noticeably affect the average Nusselt number and corresponding heat transfer rate. Besides, as expected, the heat transfer rate for the turbulent flow regime surpassed that in the laminar regime. The simulations additionally demonstrated that for a constant Richardson number, computing the radiation heat transfer majorly affected the heat transfer structure in the enclosure; however, its impact on the fluid flow structure was negligible.

Numerical Study of Entropy Generation due to Coupled Laminar and Turbulent Mixed Convection and Thermal Radiation in an Enclosure Filled with a Semitransparent Medium

PubMed Central

Goodarzi, M.; Safaei, M. R.; Oztop, Hakan F.; Karimipour, A.; Sadeghinezhad, E.; Dahari, M.; Kazi, S. N.; Jomhari, N.

2014-01-01

The effect of radiation on laminar and turbulent mixed convection heat transfer of a semitransparent medium in a square enclosure was studied numerically using the Finite Volume Method. A structured mesh and the SIMPLE algorithm were utilized to model the governing equations. Turbulence and radiation were modeled with the RNG k-ε model and Discrete Ordinates (DO) model, respectively. For Richardson numbers ranging from 0.1 to 10, simulations were performed for Rayleigh numbers in laminar flow (104) and turbulent flow (108). The model predictions were validated against previous numerical studies and good agreement was observed. The simulated results indicate that for laminar and turbulent motion states, computing the radiation heat transfer significantly enhanced the Nusselt number (Nu) as well as the heat transfer coefficient. Higher Richardson numbers did not noticeably affect the average Nusselt number and corresponding heat transfer rate. Besides, as expected, the heat transfer rate for the turbulent flow regime surpassed that in the laminar regime. The simulations additionally demonstrated that for a constant Richardson number, computing the radiation heat transfer majorly affected the heat transfer structure in the enclosure; however, its impact on the fluid flow structure was negligible. PMID:24778601

Impact of chemical reaction in fully developed radiated mixed convective flow between two rotating disk

NASA Astrophysics Data System (ADS)

Hayat, T.; Khan, M. Waleed Ahmed; Khan, M. Ijaz; Waqas, M.; Alsaedi, A.

2018-06-01

Flow of magnetohydrodynamic (MHD) viscous fluid between two rotating disks is modeled. Angular velocities of two disks are different. Flow is investigated for nonlinear mixed convection. Heat transfer is analyzed for nonlinear thermal radiation and heat generation/absorption. Chemical reaction is also implemented. Convective conditions of heat and mass transfer are studied. Transformations used lead to reduction of PDEs into the ODEs. The impacts of important physical variables like Prandtl number, Reynold number, Hartman number, mixed convection parameter, chemical reaction and Schmidt number on velocities, temperature and concentration are elaborated. In addition velocity and temperature gradients are physically interpreted. Our obtained results indicate that radial, axial and tangential velocities decrease for higher estimation of Hartman number.

Methodological assessment of skin and limb blood flows in the human forearm during thermal and baroreceptor provocations

PubMed Central

Brothers, R. Matthew; Wingo, Jonathan E.; Hubing, Kimberly A.

2010-01-01

Skin blood flow responses in the human forearm, assessed by three commonly used technologies—single-point laser-Doppler flowmetry, integrated laser-Doppler flowmetry, and laser-Doppler imaging—were compared in eight subjects during normothermic baseline, acute skin-surface cooling, and whole body heat stress (Δ internal temperature = 1.0 ± 0.2°C; P < 0.001). In addition, while normothermic and heat stressed, subjects were exposed to 30-mmHg lower-body negative pressure (LBNP). Skin blood flow was normalized to the maximum value obtained at each site during local heating to 42°C for at least 30 min. Furthermore, comparisons of forearm blood flow (FBF) measures obtained using venous occlusion plethysmography and Doppler ultrasound were made during the aforementioned perturbations. Relative to normothermic baseline, skin blood flow decreased during normothermia + LBNP (P < 0.05) and skin-surface cooling (P < 0.01) and increased during whole body heating (P < 0.001). Subsequent LBNP during whole body heating significantly decreased skin blood flow relative to control heat stress (P < 0.05). Importantly, for each of the aforementioned conditions, skin blood flow was similar between the three measurement devices (main effect of device: P > 0.05 for all conditions). Similarly, no differences were identified across all perturbations between FBF measures using plethysmography and Doppler ultrasound (P > 0.05 for all perturbations). These data indicate that when normalized to maximum, assessment of skin blood flow in response to vasoconstrictor and dilator perturbations are similar regardless of methodology. Likewise, FBF responses to these perturbations are similar between two commonly used methodologies of limb blood flow assessment. PMID:20634360

Methodological assessment of skin and limb blood flows in the human forearm during thermal and baroreceptor provocations.

PubMed

Brothers, R Matthew; Wingo, Jonathan E; Hubing, Kimberly A; Crandall, Craig G

2010-09-01

Skin blood flow responses in the human forearm, assessed by three commonly used technologies-single-point laser-Doppler flowmetry, integrated laser-Doppler flowmetry, and laser-Doppler imaging-were compared in eight subjects during normothermic baseline, acute skin-surface cooling, and whole body heat stress (Δ internal temperature=1.0±0.2 degrees C; P<0.001). In addition, while normothermic and heat stressed, subjects were exposed to 30-mmHg lower-body negative pressure (LBNP). Skin blood flow was normalized to the maximum value obtained at each site during local heating to 42 degrees C for at least 30 min. Furthermore, comparisons of forearm blood flow (FBF) measures obtained using venous occlusion plethysmography and Doppler ultrasound were made during the aforementioned perturbations. Relative to normothermic baseline, skin blood flow decreased during normothermia+LBNP (P<0.05) and skin-surface cooling (P<0.01) and increased during whole body heating (P<0.001). Subsequent LBNP during whole body heating significantly decreased skin blood flow relative to control heat stress (P<0.05). Importantly, for each of the aforementioned conditions, skin blood flow was similar between the three measurement devices (main effect of device: P>0.05 for all conditions). Similarly, no differences were identified across all perturbations between FBF measures using plethysmography and Doppler ultrasound (P>0.05 for all perturbations). These data indicate that when normalized to maximum, assessment of skin blood flow in response to vasoconstrictor and dilator perturbations are similar regardless of methodology. Likewise, FBF responses to these perturbations are similar between two commonly used methodologies of limb blood flow assessment.

Method of introducing additive into a reaction gas flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michelfelder, S.; Chughtai, M.Y.

1984-04-03

A method of continuously introducing additive, which is conveyed by gaseous and/or liquid carriers, into a turbulent reaction gas flow in the combustion chamber of a steam generator having dry ash withdrawal for selective removal, in a dry manner, of environmentally harmful gaseous noxious materials, such as sulfur, chlorine, and chlorine compounds, which are contained in a hot reaction gas flow which results after a complete or incomplete flame combustion of solid, liquid, or gaseous fuels. Depending upon the additive introduced, heat is stored and/or used for decomposition reactions. The additive, is first introduced at one or more input locations,more » due to locally different pressure conditions in the combustion chamber, into one or more recirculation flows which are within the system and are closed. The additive is subsequently withdrawn from these recirculation flows and is introduced into the reaction gas flow.« less

Thermal balance of the atmospheres of Jupiter and Uranus

NASA Technical Reports Server (NTRS)

Friedson, A. J.; Ingersoll, A. P.

1986-01-01

Two-dimensional, radiative-convective-dynamical models of the visible atmospheres of Jupiter and Uranus are presented. Zonally-averaged temperatures and heat fluxes are calculated numerically as functions of pressure and latitude. In addition to radiative heat fluxes, the dynamical heat flux due to large-scale baroclinic eddies is included and is parametrized using a mixing length theory which gives heat fluxes similar to those of Stone. The results for Jupiter indicate that the internal heat flow is non-uniform in latitude and nearly balances the net radiative flux leaving the atmosphere. The thermal emission is found to be uniform in latitude in agreement with Pioneer and Voyager observations. Baroclinic eddies are calculated to transport only a small amount of the meridional heat flow necessary to account for the uniformity of thermal emission with latitude. The bulk of the meridional heat transfer is found to occur very deep in the stable interior of Jupiter as originally proposed by Ingersoll and Porco. The relative importance of baroclinic eddies vs. internal heat flow in the thermal balance of Uranus depends on the ratio of emitted thermal power to absorbed solar power. The thermal balance of Uranus is compared to that of Jupiter for different values of this ratio.

Kinetic modeling of Nernst effect in magnetized hohlraums.

PubMed

Joglekar, A S; Ridgers, C P; Kingham, R J; Thomas, A G R

2016-04-01

We present nanosecond time-scale Vlasov-Fokker-Planck-Maxwell modeling of magnetized plasma transport and dynamics in a hohlraum with an applied external magnetic field, under conditions similar to recent experiments. Self-consistent modeling of the kinetic electron momentum equation allows for a complete treatment of the heat flow equation and Ohm's law, including Nernst advection of magnetic fields. In addition to showing the prevalence of nonlocal behavior, we demonstrate that effects such as anomalous heat flow are induced by inverse bremsstrahlung heating. We show magnetic field amplification up to a factor of 3 from Nernst compression into the hohlraum wall. The magnetic field is also expelled towards the hohlraum axis due to Nernst advection faster than frozen-in flux would suggest. Nonlocality contributes to the heat flow towards the hohlraum axis and results in an augmented Nernst advection mechanism that is included self-consistently through kinetic modeling.

Boiling of multicomponent working fluids used in refrigeration and cryogenic systems

NASA Astrophysics Data System (ADS)

Mogorychny, V. I.; Dolzhikov, A. S.

2017-11-01

Working fluids based on mixtures are widely used in cryogenic and refrigeration engineering. One of the main elements of low-temperature units is a recuperative heat exchanger where the return flow cools the direct (cold regeneration is carrying out) resulting in continuous boiling and condensation of the multicomponent working fluid in the channels. The temperature difference between the inlet and outlet of the heat exchanger can be more than 100K, which leads to a strong change in thermophysical properties along its length. In addition, the fraction of the liquid and vapor phases in the flow varies very much, which affects the observed flow regimes in the heat exchanger channels. At the moment there are not so many experimental data and analytical correlations that would allow to estimate the heat transfer coefficient during the flow of a two-phase mixture flow at low temperatures. The work is devoted to the study of the boiling process of multicomponent working fluids used in refrigeration and cryogenic engineering. The description of the method of determination of heat transfer coefficient during boiling of mixtures in horizontal heated channel is given as well as the design of the experimental stand allowing to make such measurements. This stand is designed on the basis of a refrigeration unit operating on the Joule-Thomson throttle cycle and makes it possible to measure the heat transfer coefficient with a good accuracy. Also, the calculated values of the heat transfer coefficient, obtained with the use of various correlations, are compared with the existing experimental data. Knowing of the heat transfer coefficient will be very useful in the design of heat exchangers for low-temperature units operating on a mixture refrigerant.

Numerical Analysis of Coolant Flow and Heat Transfer in ITER Diagnostic First Wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khodak, A.; Loesser, G.; Zhai, Y.

2015-07-24

We performed numerical simulations of the ITER Diagnostic First Wall (DFW) using ANSYS workbench. During operation DFW will include solid main body as well as liquid coolant. Thus thermal and hydraulic analysis of the DFW was performed using conjugated heat transfer approach, in which heat transfer was resolved in both solid and liquid parts, and simultaneously fluid dynamics analysis was performed only in the liquid part. This approach includes interface between solid and liquid part of the systemAnalysis was performed using ANSYS CFX software. CFX software allows solution of heat transfer equations in solid and liquid part, and solution ofmore » the flow equations in the liquid part. Coolant flow in the DFW was assumed turbulent and was resolved using Reynolds averaged Navier-Stokes equations with Shear Stress Transport turbulence model. Meshing was performed using CFX method available within ANSYS. The data cloud for thermal loading consisting of volumetric heating and surface heating was imported into CFX Volumetric heating source was generated using Attila software. Surface heating was obtained using radiation heat transfer analysis. Our results allowed us to identify areas of excessive heating. Proposals for cooling channel relocation were made. Additional suggestions were made to improve hydraulic performance of the cooling system.« less

Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow.

PubMed

Teng, Tun-Ping; Hung, Yi-Hsuan; Teng, Tun-Chien; Chen, Jyun-Hong

2011-08-09

This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration.

Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

PubMed Central

2011-01-01

This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration. PMID:21827644

Pressure drop reduction and heat transfer deterioration of slush nitrogen in triangular and circular pipe flows

NASA Astrophysics Data System (ADS)

Ohira, Katsuhide; Kurose, Kizuku; Okuyama, Jun; Saito, Yutaro; Takahashi, Koichi

2017-01-01

Slush fluids such as slush hydrogen and slush nitrogen are characterized by superior properties as functional thermal fluids due to their density and heat of fusion. In addition to allowing efficient hydrogen transport and storage, slush hydrogen can serve as a refrigerant for high-temperature superconducting (HTS) equipment using MgB2, with the potential for synergistic effects. In this study, pressure drop reduction and heat transfer deterioration experiments were performed on slush nitrogen flowing in a horizontal triangular pipe with sides of 20 mm under the conditions of three different cross-sectional orientations. Experimental conditions consisted of flow velocity (0.3-4.2 m/s), solid fraction (0-25 wt.%), and heat flux (0, 10, and 20 kW/m2). Pressure drop reduction became apparent at flow velocities exceeding about 1.3-1.8 m/s, representing a maximum amount of reduction of 16-19% in comparison with liquid nitrogen, regardless of heating. Heat transfer deterioration was seen at flow velocities of over 1.2-1.8 m/s, for a maximum amount of deterioration of 13-16%. The authors of the current study compared the results for pressure drop reduction and heat transfer deterioration in triangular pipe with those obtained previously for circular and square pipes, clarifying differences in flow and heat transfer properties. Also, a correlation equation was obtained between the slush Reynolds number and the pipe friction factor, which is important in the estimation of pressure drop in unheated triangular pipe. Furthermore, a second correlation equation was derived between the modified slush Reynolds number and the pipe friction factor, enabling the integrated prediction of pressure drop in both unheated triangular and circular pipes.

CFD Analysis of the Oscillating Flow within a Stirling Engine with an Additively Manufactured Foil Type Regenerator

NASA Astrophysics Data System (ADS)

Qiu, Songgang; Solomon, Laura

2017-11-01

The simplistic design, fuel independence, and robustness of Stirling convertors makes them the ideal choice for use in solar power and combined heat and power (CHP) applications. A lack of moving parts and the use of novel flexure bearings allows free-piston type Stirling engines to run in excess of ten years without degradation or maintenance. The key component to their overall efficiency is the regenerator. While a foil type regenerator outperforms a sintered random fiber regenerator, limitation in manufacturing and keeping uniform spacing between the foils has limited their overall use. However, with the advent of additive manufacturing, a robust foil type regenerator can be cheaply manufactured without traditional limitations. Currently, a CFD analysis of the oscillating internal flow within the novel design was conducted to evaluate the flow loses within the system. Particularly the pressure drop across the regenerator in comparison to a traditionally used random fiber regenerator. Additionally, the heat transfer and flow over the tubular heater hear was evaluated. The results of the investigation will be used to optimize the operation of the next generation of additively manufactured Stirling convertors. This research was supported by ARPA-E and West Virginia University.

Experimental study on convective heat transfer of TiO2 nanofluids

NASA Astrophysics Data System (ADS)

Vakili, M.; Mohebbi, A.; Hashemipour, H.

2013-08-01

In this study, nanofluids with different TiO2 nanoparticle concentrations were synthesized and measured in different constant heat fluxes for their heat transfer behavior upon flowing through a vertical pipe. Addition of nanoparticles into the base fluid enhances the forced convective heat transfer coefficient. The results show that the enhancement of the convective heat transfer coefficient in the mixture consisting of ethylene glycol and distilled water is more than distilled water as a base fluid.

Regional Heat Flow Map and the Continental Thermal Isostasy Understanding of México

NASA Astrophysics Data System (ADS)

Espinoza-Ojeda, O. M.; Harris, R. N.

2014-12-01

The first heat flow values made in Mexico were reported by Von Herzen [Science, 1963] for the marine environment and Smith [EPSL, 1974] for the continent. Since that time the number of measurements has increased greatly but are mostly from oil and gas exploration and in and around geothermal areas. We have compiled published values of conductive heat flow for Mexico and the Gulf of California to generate a new regional heat flow map consisting of 261 values. In addition to those original values, published heat flow sources include, Lee and Henyey [JGR, 1975], Lawver and Williams [JGR, 1979] Smith et al. [JGR, 1979], Lachenbruch et al. [JGR, 1985], and Ziagos et al. [JGR, 1985]. Although the geographic distribution is uneven, heat flow data are present in each of the eight main tectonic provinces. Our new compilation indicates relatively high regional heat flow averages in the Gulf Extensional Province (n=114, 92±22 mW/m2) and Mexican Basin and Range (n=21, 82±20 mW/m2) and are consistent with geologic estimates of extension. Lower regional averages are found in the Baja California Microplate (n=91, 75±19 mW/m2), the Sierra Madre Occidental (n=9, 75±12 mW/m2), the Sierra Madre Oriental (n=4, 68±15 mW/m2) and Mesa Central (n=X 77±23 mW/m2). In contrast low and variable heat flow value characterize the forearc region of the Middle America Trench (n=6, 35±16 mW/m2). A higher mean heat flow is associated with the Trans-Mexican Volcanic Belt (n=6, 78±26 mW/m2). Continental elevation results from a combination of buoyancy (i.e. compositional and thermal) and geodynamic forces. We combine these regional heat flow values with estimates of crustal thickness and density for each tectonic province and compute the thermal and compositional buoyancy following the approach of Hasterok and Chapman [JGR, 2007a,b]. We find that within uncertainties most provinces lie near the theoretical isostatic relationship with the exception of the Mesa Central and Sierra Madre del Sur that are anomalously below and above the theoretical relationship, respectively.

Chemical reaction and heat generation/absorption aspects in MHD nonlinear convective flow of third grade nanofluid over a nonlinear stretching sheet with variable thickness

NASA Astrophysics Data System (ADS)

Qayyum, Sajid; Hayat, Tasawar; Alsaedi, Ahmed

Nonlinear thermal radiation and chemical reaction in magnetohydrodynamic (MHD) flow of third grade nanofluid over a stretching sheet with variable thickness are addressed. Heat generation/absorption and nonlinear convection are considered. The sheet moves with nonlinear velocity. Sheet is convectively heated. In addition zero mass flux condition for nanoparticle concentration is imposed. Results for velocity, temperature, concentration, skin friction and local Nusselt number are presented and examined. It is found that velocity and boundary layer thickness are increasing for Reynolds number. Temperature is a increasing function of the heat generation/absorption parameter while it causes a decrease in the heat transfer rate. Moreover effect of Brownian motion and chemical reaction on the concentration are quite reverse.

Turbulence modeling of gas-solid suspension flows

NASA Technical Reports Server (NTRS)

Chen, C. P.

1988-01-01

The purpose here is to discuss and review advances in two-phase turbulent modeling techniques and their applications in various gas-solid suspension flow situations. In addition to the turbulence closures, heat transfer effect, particle dispersion and wall effects are partially covered.

Analysis of buoyancy effect on fully developed laminar heat transfer in a rotating tube

NASA Technical Reports Server (NTRS)

Siegel, R.

1985-01-01

Laminar heat transfer is analyzed in a tube rotating about an axis perpendicular to the tube axis. The solution applies for flow that is either radially outward from the axis of rotation, or radially inward toward the axis of rotation. The conditions are fully developed, and there is uniform heat addition at the tube wall. The analysis is performed by expanding velocities and temperature in power series using the Taylor number as a perturbation parameter. Coriolis and buoyancy forces caused by tube rotation are included, and the solution is calculated through second-order terms. The secondary flow induced by the Coriolis terms always tends to increase the heat transfer coefficient; this effect can dominate for small wall heating. For radial inflow, buoyancy also tends to improve heat transfer. For radial outflow, however, buoyancy tends to reduce heat transfer; for large wall heating this effect can dominate, and there is a net reduction in heat transfer coefficient.

Heat flow in the western abyssal plain of the Gulf of Mexico: Implications for thermal evolution of the old oceanic lithosphere

NASA Astrophysics Data System (ADS)

Nagihara, S.; Sclater, J. G.; Phillips, J. D.; Behrens, E. W.; Lewis, T.; Lawver, L. A.; Nakamura, Y.; Garcia-Abdeslem, J.; Maxwell, A. E.

1996-02-01

The seafloor depth of an oceanic basin reflects the average temperature of the lithosphere. Thus the western abyssal plain of the Gulf of Mexico, which has tectonically subsided much (>1 km) deeper than other basins of comparable ages (late Jurassic), should be underlain by an anomalously cold lithosphere. In order to examine this hypothesis, we made suites of high-accuracy heat flow measurements at 10 sites along a line connecting Deep Sea Drilling Project (DSDP) sites 90 and 91 in the Sigsbee abyssal plain. The new heat flow sites were initially surveyed by 3.5-kHz echo sounding, 4-channel seismic reflection, seismic refraction with eight ocean bottom seismometers, and nine piston cores. We occupied a total of 48 heat flow stations along the seismic survey line (3 to 6 at each site), including 28 where we measured in situ thermal conductivities over the practical depth interval (4 m) of the new multioutrigger bow heat flow probe. We determined the heat flow associated with the lithosphere by correcting the values measured at the seafloor (41 to 45 mW/m2) for (1) the thermal effect of the sedimentation and (2) the additional heat from the radioactive elements within the sediments. The sedimentation history, required for the first, was reconstructed at each heat flow site based on ages and thicknesses of the major seismic stratigraphical sequences, age data from the DSDP cores, 3.5-kHz subbottom reflectors, and correlation of turbidite units found in the piston cores. Radiogenic heat production was measured for 55 sediment samples from four DSDP holes in the gulf, whose age ranged from present to Early Cretaceous (0.83 μW/m3 on the average). This provided the correction for the second. The effects of these two secondary factors approximately cancel one another. The lithospheric heat flow under the abyssal plain thus estimated ranges from 40 to 47 mW/m2. These heat flow values are among the lowest in the Mesozoic ocean basins where highly reliable data (45 to 55 mW/m2) have been reported. Therefore the lithosphere under the gulf seems indeed colder than that under other old ocean basins. However, it is not as cold as expected from the large tectonic subsidence. The inconsistency between the depth and heat flow may imply an anomaly in the regional thermal isostasy.

Modelling the behaviour of additives in gun barrels

NASA Astrophysics Data System (ADS)

Rhodes, N.; Ludwig, J. C.

1986-01-01

A mathematical model which predicts the flow and heat transfer in a gun barrel is described. The model is transient, two-dimensional and equations are solved for velocities and enthalpies of a gas phase, which arises from the combustion of propellant and cartridge case, for particle additives which are released from the case; volume fractions of the gas and particles. Closure of the equations is obtained using a two-equation turbulence model. Preliminary calculations are described in which the proportions of particle additives in the cartridge case was altered. The model gives a good prediction of the ballistic performance and the gas to wall heat transfer. However, the expected magnitude of reduction in heat transfer when particles are present is not predicted. The predictions of gas flow invalidate some of the assumptions made regarding case and propellant behavior during combustion and further work is required to investigate these effects and other possible interactions, both chemical and physical, between gas and particles.

Thermal heat-balance mode flow-to-frequency converter

NASA Astrophysics Data System (ADS)

Pawlowski, Eligiusz

2016-11-01

This paper presents new type of thermal flow converter with the pulse frequency output. The integrating properties of the temperature sensor have been used, which allowed for realization of pulse frequency modulator with thermal feedback loop, stabilizing temperature of sensor placed in the flowing medium. The system assures balancing of heat amount supplied in impulses to the sensor and heat given up by the sensor in a continuous way to the flowing medium. Therefore the frequency of output impulses is proportional to the heat transfer coefficient from sensor to environment. According to the King's law, the frequency of those impulses is a function of medium flow velocity around the sensor. The special feature of presented solution is total integration of thermal sensor with the measurement signal conditioning system. Sensor and conditioning system are not the separate elements of the measurement circuit, but constitute a whole in form of thermal heat-balance mode flow-to-frequency converter. The advantage of such system is easiness of converting the frequency signal to the digital form, without using any additional analogue-to-digital converters. The frequency signal from the converter may be directly connected to the microprocessor input, which with use of standard built-in counters may convert the frequency into numerical value of high precision. Moreover, the frequency signal has higher resistance to interference than the voltage signal and may be transmitted to remote locations without the information loss.

Local measurement and numerical modeling of mass/heat transfer from a turbine blade in a linear cascade with tip clearance

NASA Astrophysics Data System (ADS)

Jin, Peitong

2000-11-01

Local mass/heat transfer measurements from the turbine blade near-tip and the tip surfaces are performed using the naphthalene sublimation technique. The experiments are conducted in a linear cascade consisting of five high-pressure blades with a central test-blade configuration. The incoming flow conditions are close to those of the gas turbine engine environment (boundary layer displacement thickness is about 0.01 of chord) with an exit Reynolds number of 6.2 x 105. The effects of tip clearance level (0.86%--6.90% of chord), mainstream Reynolds number and turbulence intensity (0.2 and 12.0%) are investigated. Two methods of flow visualization---oil and lampblack, laser light sheet smoke wire---as well as static pressure measurement on the blade surface are used to study the tip leakage flow and vortex in the cascade. In addition, numerical modeling of the flow and heat transfer processes in the linear cascade with different tip clearances is conducted using commercial software incorporating advanced turbulence models. The present study confirms many important results on the tip leakage flow and vortex from the literature, contributes to the current understanding in the effects of tip leakage flow and vortex on local heat transfer from the blade near-tip and the tip surfaces, and provides detailed local and average heat/mass transfer data applicable to turbine blade tip cooling design.

Perforated fins effect on the heat transfer rate from a circular tube by using wind tunnel: An experimental view

NASA Astrophysics Data System (ADS)

Ahmadi Nadooshan, Afshin; Kalbasi, Rasool; Afrand, Masoud

2018-04-01

Perforated fins effects on the heat transfer rate of a circular tube are examined experimentally. An experimental system is set up through the wind tunnel and equipped with necessary measurement tools. Hot water passes through the finned tube and heat transfers to the fin-side air created using the wind tunnel with different velocities. Two fin sets of identical weight are installed on a circular tube with different outer diameters of 22 and 26 mm. The experiments are conducted at two different mass flow rates of the hot water and six Reynolds number of external air flow. Considering the four finned tubes and one no finned tube, a total of 60 tests are conducted. Results showed that with increasing the internal or external flow rates, the effect of larger cross-sectional area is greater. By opening holes on the fins, in addition to weight loss, the maximum heat transfer rate for perforated fins increases by 8.78% and 9.23% respectively for mass flow rates of 0.05 and 0.1 kg/s at low external Reynolds number. While, at high external Reynolds number, the holes reduces heat transfer by 8.4% and 10.6% for mass flow rates of 0.05 and 0.1 kg/s, respectively.

Additional experiments on flowability improvements of aviation fuels at low temperatures, volume 2

NASA Technical Reports Server (NTRS)

Stockemer, F. J.; Deane, R. L.

1982-01-01

An investigation was performed to study flow improver additives and scale-model fuel heating systems for use with aviation hydrocarbon fuel at low temperatures. Test were performed in a facility that simulated the heat transfer and temperature profiles anticipated in wing fuel tanks during flight of long-range commercial aircraft. The results are presented of experiments conducted in a test tank simulating a section of an outer wing integral fuel tank approximately full-scale in height, chilled through heat exchange panels bonded to the upper and lower horizontal surfaces. A separate system heated lubricating oil externally by a controllable electric heater, to transfer heat to fuel pumped from the test tank through an oil-to-fuel heat exchanger, and to recirculate the heated fuel back to the test tank.

Calibration, Data Acquisition, and Post Analysis of Turbulent Fluid Flow in a Calibration Jet Using Hot-wire Anemometry

NASA Technical Reports Server (NTRS)

Moreno, Michelle

2004-01-01

The Turbine Branch concentrates on the following areas: Computational Fluid Dynamics (CFD), and implementing experimental procedures to obtain physical modeling data. Hot-wire Anemometry is a valuable tool for obtaining physical modeling data. Hot-wire Anemometry is likely to remain the principal research tool for most turbulent air/gas flow studies. The Hot-wire anemometer consists of a fine wire heated by electric current. When placed in a fluid stream, the hot-wire loses heat to the fluid by forced convection. In forced convection, energy transfer is due to molecular motion imposed by an extraneous force moving fluid parcels. When the hot-wire is in "equilibrium", the rate of heat input to the wire is equal to the rate of heat loss at the wire ends. The equality between heat input and heat loss is the basis for King s equation, which relates the electrical parameters of the hot-wire to the flow parameters of the fluid. Hot-wire anemometry is based on convective heat transfer from a heated wire element placed in a fluid flow. Any change in the fluid flow condition that affects the heat transfer from the heated element will be detected virtually instantaneously by a constant-temperature Hot-wire anemometry system. The system implemented for this research is the IFA 300. The system is a fully-integrated, thermal anemometer-based system that measures mean and fluctuating velocity components in air, water, and other fluids. It also measures turbulence and makes localized temperature measurements. A constant-temperature anemometer is a bridge and amplifier circuit that controls a tiny wire at constant temperature. As a fluid flow passes over the heated sensor, the amplifier senses the bridge off-balance and adjusts the voltage to the top of the bridge, keeping the bridge in balance. The voltage on top of the bridge can then be related to the velocity of the flow. The bridge voltage is sensitive to temperature as well as velocity and so the built-in thermocouple circuit can be attached to a thermocouple that can measure the fluid temperature. Additional information is included in the original extended abstract.

SAFSIM theory manual: A computer program for the engineering simulation of flow systems

NASA Astrophysics Data System (ADS)

Dobranich, Dean

1993-12-01

SAFSIM (System Analysis Flow SIMulator) is a FORTRAN computer program for simulating the integrated performance of complex flow systems. SAFSIM provides sufficient versatility to allow the engineering simulation of almost any system, from a backyard sprinkler system to a clustered nuclear reactor propulsion system. In addition to versatility, speed and robustness are primary SAFSIM development goals. SAFSIM contains three basic physics modules: (1) a fluid mechanics module with flow network capability; (2) a structure heat transfer module with multiple convection and radiation exchange surface capability; and (3) a point reactor dynamics module with reactivity feedback and decay heat capability. Any or all of the physics modules can be implemented, as the problem dictates. SAFSIM can be used for compressible and incompressible, single-phase, multicomponent flow systems. Both the fluid mechanics and structure heat transfer modules employ a one-dimensional finite element modeling approach. This document contains a description of the theory incorporated in SAFSIM, including the governing equations, the numerical methods, and the overall system solution strategies.

Two-phase magnetoconvection flow of magnetite (Fe3O4) nanoparticles in a horizontal composite porous annulus

NASA Astrophysics Data System (ADS)

Abbas, Zaheer; Hasnain, Jafar

A numerical study is performed to examine the two-phase magnetoconvection and heat transfer phenomena of Fe3O4 -kerosene nanofluid flow in a horizontal composite porous annulus with an external magnetic field. The annulus is filled with immiscible fluids flowing between two concentric cylinders. The governing equations of the flow problem are obtained using Darcy-Brinkman model. Heat transfer is analyzed in the presence of viscous and Darcian dissipation terms. The shooting method is used as a tool to solve the obtained non-linear ordinary differential equations for the velocity and temperature profiles. The velocity and temperature distributions are analyzed and discussed under the influence of involved flow parameters with the aid of graphs. It is found that both velocity and temperature of fluid are decreased with ferroparticle volume fraction. In addition to that, it is also presented that the existence of magnetic field decreases the benefit of ferrofluids in heat transfer progression.

Two-phase flow research using the DC-9/KC-135 apparatus

NASA Technical Reports Server (NTRS)

McQuillen, John B.; Neumann, Eric S.; Shoemaker, J. Michael

1996-01-01

Low-gravity gas-liquid flow research can be conducted aboard the NASA Lewis Research Center DC-9 or the Johnson Space Center KC-135. Air and water solutions serve as the test liquids in cylindrical test sections with constant or variable inner diameters of approximately 2.54 cm and lengths of up to 3.0 m. Superficial velocities range from 0.1 to 1.1 m/sec for liquids and from 0.1 to 25 m/sec for air. Flow rate, differential pressure, void fraction, film thickness, wall shear stress, and acceleration data are measured and recorded at data rates of up to 1000 Hz throughout the 20-sec duration of the experiment. Flow is visualized with a high-speed video system. In addition, the apparatus has a heat-transfer capability whereby sensible heat is transferred between the test-section wall and a subcooled liquid phase so that the heat-transfer characteristics of gas-liquid two-phase flows can be determined.

A Comprehensive Study of a Micro-Channel Heat Sink Using Integrated Thin-Film Temperature Sensors

PubMed Central

Wang, Tao; Wang, Jiejun; He, Jian; Wu, Chuangui; Luo, Wenbo; Shuai, Yao; Zhang, Wanli; Chen, Xiancai; Zhang, Jian; Lin, Jia

2018-01-01

A micro-channel heat sink is a promising cooling method for high power integrated circuits (IC). However, the understanding of such a micro-channel device is not sufficient, because the tools for studying it are very limited. The details inside the micro-channels are not readily available. In this letter, a micro-channel heat sink is comprehensively studied using the integrated temperature sensors. The highly sensitive thin film temperature sensors can accurately monitor the temperature change in the micro-channel in real time. The outstanding heat dissipation performance of the micro-channel heat sink is proven in terms of maximum temperature, cooling speed and heat resistance. The temperature profile along the micro-channel is extracted, and even small temperature perturbations can be detected. The heat source formed temperature peak shifts towards the flow direction with the increasing flow rate. However, the temperature non-uniformity is independent of flow rate, but solely dependent on the heating power. Specific designs for minimizing the temperature non-uniformity are necessary. In addition, the experimental results from the integrated temperature sensors match the simulation results well. This can be used to directly verify the modeling results, helping to build a convincing simulation model. The integrated sensor could be a powerful tool for studying the micro-channel based heat sink. PMID:29351248

A Comprehensive Study of a Micro-Channel Heat Sink Using Integrated Thin-Film Temperature Sensors.

PubMed

Wang, Tao; Wang, Jiejun; He, Jian; Wu, Chuangui; Luo, Wenbo; Shuai, Yao; Zhang, Wanli; Chen, Xiancai; Zhang, Jian; Lin, Jia

2018-01-19

A micro-channel heat sink is a promising cooling method for high power integrated circuits (IC). However, the understanding of such a micro-channel device is not sufficient, because the tools for studying it are very limited. The details inside the micro-channels are not readily available. In this letter, a micro-channel heat sink is comprehensively studied using the integrated temperature sensors. The highly sensitive thin film temperature sensors can accurately monitor the temperature change in the micro-channel in real time. The outstanding heat dissipation performance of the micro-channel heat sink is proven in terms of maximum temperature, cooling speed and heat resistance. The temperature profile along the micro-channel is extracted, and even small temperature perturbations can be detected. The heat source formed temperature peak shifts towards the flow direction with the increasing flow rate. However, the temperature non-uniformity is independent of flow rate, but solely dependent on the heating power. Specific designs for minimizing the temperature non-uniformity are necessary. In addition, the experimental results from the integrated temperature sensors match the simulation results well. This can be used to directly verify the modeling results, helping to build a convincing simulation model. The integrated sensor could be a powerful tool for studying the micro-channel based heat sink.

Regional blood flow in sea turtles: implications for heat exchange in an aquatic ectotherm.

PubMed

Hochscheid, Sandra; Bentivegna, Flegra; Speakman, John R

2002-01-01

Despite substantial knowledge on thermoregulation in reptiles, the mechanisms involved in heat exchange of sea turtles have not been investigated in detail. We studied blood flow in the front flippers of two green turtles, Chelonia mydas, and four loggerhead turtles, Caretta caretta, using Doppler ultrasound to assess the importance of regional blood flow in temperature regulation. Mean blood flow velocity and heart rate were determined for the water temperature at which the turtles were acclimated (19.3 degrees-22.5 degrees C) and for several experimental water temperatures (17 degrees-32 degrees C) to which the turtles were exposed for a short time. Flipper circulation increased with increasing water temperature, whereas during cooling, flipper circulation was greatly reduced. Heart rate was also positively correlated with water temperature; however, there were large variations between individual heart rate responses. Body temperatures, which were additionally determined for the two green turtles and six loggerhead turtles, increased faster during heating than during cooling. Heating rates were positively correlated with the difference between acclimation and experimental temperature and negatively correlated with body mass. Our data suggest that by varying circulation of the front flippers, turtles are capable of either transporting heat quickly into the body or retaining heat inside the body, depending on the prevailing thermal demands.

Aerothermodynamic measurements for space shuttle configuration in hypersonic wind tunnels

NASA Technical Reports Server (NTRS)

Bertin, J. J.; Williams, F. E.; Baker, R. C.; Goodrich, W. D.; Kessler, W. C.

1972-01-01

The effect of shuttle configuration geometry, angle of attack, and free stream flow conditions on the heat-transfer distribution as influenced by three-dimensional effects, the wing-fuselage shock-interaction, and resultant wing-impingement phenomena are examined. In addition, the data provided information regarding the flow field in the vicinity of the nose and boundary layer transition in the plane of symmetry of the fuselage. The data included measurements of the surface pressure, the heat transfer rate distributions, (using models instrumented with thermocouples and models painted with thermographic phosphor) and schlieren and shadowgraph photographs. Posttest photographs of the painted models supplemented the heat transfer data.

Thermal protection for hypervelocity flight in earth's atmosphere by use of radiation backscattering ablating materials

NASA Technical Reports Server (NTRS)

Howe, John T.; Yang, Lily

1991-01-01

A heat-shield-material response code predicting the transient performance of a material subject to the combined convective and radiative heating associated with the hypervelocity flight is developed. The code is dynamically interactive to the heating from a transient flow field, including the effects of material ablation on flow field behavior. It accomodates finite time variable material thickness, internal material phase change, wavelength-dependent radiative properties, and temperature-dependent thermal, physical, and radiative properties. The equations of radiative transfer are solved with the material and are coupled to the transfer energy equation containing the radiative flux divergence in addition to the usual energy terms.

On radiative heat transfer in stagnation point flow of MHD Carreau fluid over a stretched surface

NASA Astrophysics Data System (ADS)

Khan, Masood; Sardar, Humara; Mudassar Gulzar, M.

2018-03-01

This paper investigates the behavior of MHD stagnation point flow of Carreau fluid in the presence of infinite shear rate viscosity. Additionally heat transfer analysis in the existence of non-linear radiation with convective boundary condition is performed. Moreover effects of Joule heating is observed and mathematical analysis is presented in the presence of viscous dissipation. The suitable transformations are employed to alter the leading partial differential equations to a set of ordinary differential equations. The subsequent non-straight common ordinary differential equations are solved numerically by an effective numerical approach specifically Runge-Kutta Fehlberg method alongside shooting technique. It is found that the higher values of Hartmann number (M) correspond to thickening of the thermal and thinning of momentum boundary layer thickness. The analysis further reveals that the fluid velocity is diminished by increasing the viscosity ratio parameter (β∗) and opposite trend is observed for temperature profile for both hydrodynamic and hydromagnetic flows. In addition the momentum boundary layer thickness is increased with velocity ratio parameter (α) and opposite is true for thermal boundary layer thickness.

Numerical and Experimental Approaches Toward Understanding Lava Flow Heat Transfer

NASA Astrophysics Data System (ADS)

Rumpf, M.; Fagents, S. A.; Hamilton, C.; Crawford, I. A.

2013-12-01

We have performed numerical modeling and experimental studies to quantify the heat transfer from a lava flow into an underlying particulate substrate. This project was initially motivated by a desire to understand the transfer of heat from a lava flow into the lunar regolith. Ancient regolith deposits that have been protected by a lava flow may contain ancient solar wind, solar flare, and galactic cosmic ray products that can give insight into the history of our solar system, provided the records were not heated and destroyed by the overlying lava flow. In addition, lava-substrate interaction is an important aspect of lava fluid dynamics that requires consideration in lava emplacement models Our numerical model determines the depth to which the heat pulse will penetrate beneath a lava flow into the underlying substrate. Rigorous treatment of the temperature dependence of lava and substrate thermal conductivity and specific heat capacity, density, and latent heat release are imperative to an accurate model. Experiments were conducted to verify the numerical model. Experimental containers with interior dimensions of 20 x 20 x 25 cm were constructed from 1 inch thick calcium silicate sheeting. For initial experiments, boxes were packed with lunar regolith simulant (GSC-1) to a depth of 15 cm with thermocouples embedded at regular intervals. Basalt collected at Kilauea Volcano, HI, was melted in a gas forge and poured directly onto the simulant. Initial lava temperatures ranged from ~1200 to 1300 °C. The system was allowed to cool while internal temperatures were monitored by a thermocouple array and external temperatures were monitored by a Forward Looking Infrared (FLIR) video camera. Numerical simulations of the experiments elucidate the details of lava latent heat release and constrain the temperature-dependence of the thermal conductivity of the particulate substrate. The temperature-dependence of thermal conductivity of particulate material is not well known, especially at high temperatures. It is important to have this property well constrained as substrate thermal conductivity is the greatest influence on the rate of lava-substrate heat transfer. At Kilauea and Mauna Loa Volcanoes, Hawaii, and other volcanoes that threaten communities, lava may erupt over a variety of substrate materials including cool lava flows, volcanic tephra, soils, sand, and concrete. The composition, moisture, organic content, porosity, and grain size of the substrate dictate the thermophysical properties, thus affecting the transfer of heat from the lava flow into the substrate and flow mobility. Particulate substrate materials act as insulators, subduing the rate of heat transfer from the flow core. Therefore, lava that flows over a particulate substrate will maintain higher core temperatures over a longer period, enhancing flow mobility and increasing the duration and aerial coverage of the resulting flow. Lava flow prediction models should include substrate specification with temperature dependent material property definitions for an accurate understanding of flow hazards.

Thin Film Heat Flux Sensors: Design and Methodology

NASA Technical Reports Server (NTRS)

Fralick, Gustave C.; Wrbanek, John D.

2013-01-01

Thin Film Heat Flux Sensors: Design and Methodology: (1) Heat flux is one of a number of parameters, together with pressure, temperature, flow, etc. of interest to engine designers and fluid dynamists, (2) The measurement of heat flux is of interest in directly determining the cooling requirements of hot section blades and vanes, and (3)In addition, if the surface and gas temperatures are known, the measurement of heat flux provides a value for the convective heat transfer coefficient that can be compared with the value provided by CFD codes.

Temperature Distribution and Critical Current of Long HTS Cables Cooled with Subcooled Liquid Nitrogen

NASA Astrophysics Data System (ADS)

Vyatkin, V. S.; Ivanov, Y. V.; Watanabe, H.; Chikumoto, N.; Yamaguchi, S.

2017-07-01

Cooling of the long HTS power transmission lines performs by pumping of subcooled liquid nitrogen (LN2) along the cable. The temperature of LN2 along the cable increases due to the heat losses of the cryostat and heat generation in the HTS cable. The experiment using test cable line in Ishikari shows that flow rate of 35 L/min retains increasing of LN2 temperature by 1 K per 1 km of length. The technology when the back flow of LN2 cools the radiation shield surrounding the cable pipe is also applied in Ishikari-2 project. In this case the ambient heat flow into cable pipe is 50 times less than that without radiation shield. Back flow of LN2 removes almost all heat coming from the environment. When transport current is close to the critical value the Joule heat of HTS cable is significant. This heat additionally increases the temperature of LN2 flowing along the HTS cable. Near the outlet the temperature of HTS cable is maximal and the local critical current is minimal. The current matching critical current criterion of average electrical field of E 0 = 10-4 V/m provides the voltage drop and significant Joule heat at the hot end of the cable. It can lead the damage of the cable. The present work contains analysis of temperature distribution along the cable and the way to achieve the fail-safe operation of long HTS cable cooled by subcooled LN2. We also performed extrapolation of obtained results for several times longer cable lines by decreasing the LN2 flow rate.

A one-dimensional heat-transport model for conduit flow in karst aquifers

USGS Publications Warehouse

Long, Andrew J.; Gilcrease, P.C.

2009-01-01

A one-dimensional heat-transport model for conduit flow in karst aquifers is presented as an alternative to two or three-dimensional distributed-parameter models, which are data intensive and require knowledge of conduit locations. This model can be applied for cases where water temperature in a well or spring receives all or part of its water from a phreatic conduit. Heat transport in the conduit is simulated by using a physically-based heat-transport equation that accounts for inflow of diffuse flow from smaller openings and fissures in the surrounding aquifer during periods of low recharge. Additional diffuse flow that is within the zone of influence of the well or spring but has not interacted with the conduit is accounted for with a binary mixing equation to proportion these different water sources. The estimation of this proportion through inverse modeling is useful for the assessment of contaminant vulnerability and well-head or spring protection. The model was applied to 7 months of continuous temperature data for a sinking stream that recharges a conduit and a pumped well open to the Madison aquifer in western South Dakota. The simulated conduit-flow fraction to the well ranged from 2% to 31% of total flow, and simulated conduit velocity ranged from 44 to 353 m/d.

Interfacing a General Purpose Fluid Network Flow Program with the SINDA/G Thermal Analysis Program

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Popok, Daniel

1999-01-01

A general purpose, one dimensional fluid flow code is currently being interfaced with the thermal analysis program Systems Improved Numerical Differencing Analyzer/Gaski (SINDA/G). The flow code, Generalized Fluid System Simulation Program (GFSSP), is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development is conducted in multiple phases. This paper describes the first phase of the interface which allows for steady and quasi-steady (unsteady solid, steady fluid) conjugate heat transfer modeling.

Use of heat as a groundwater tracer in fractured rock hydrology

NASA Astrophysics Data System (ADS)

Bour, Olivier; Le Borgne, Tanguy; Klepikova, Maria V.; Read, Tom; Selker, John S.; Bense, Victor F.; Le Lay, Hugo; Hochreutener, Rebecca; Lavenant, Nicolas

2015-04-01

Crystalline rocks aquifers are often difficult to characterize since flows are mainly localized in few fractures. In particular, the geometry and the connections of the main flow paths are often only partly constrained with classical hydraulic tests. Here, we show through few examples how heat can be used to characterize groundwater flows in fractured rocks at the borehole, inter-borehole and watershed scale. Estimating flows from temperature measurements requires heat advection to be the dominant process of heat transport, but this condition is generally met in fractured rock at least within the few structures where flow is highly channelized. At the borehole scale, groundwater temperature variations with depth can be used to locate permeable fractures and to estimates borehole flows. Measurements can be done with classical multi-parameters probes, but also with recent technologies such as Fiber Optic Distributed Temperature Sensing (FO-DTS) which allows to measure temperature over long distances with an excellent spatial and temporal resolution. In addition, we show how a distributed borehole flowmeter can be achieved using an armored fiber-optic cable and measuring the difference in temperature between a heated and unheated cable that is a function of the fluid velocity. At the inter-borehole scale, temperature changes during cross-borehole hydraulic tests allow to identify the connections and the hydraulic properties of the main flow paths between boreholes. At the aquifer scale, groundwater temperature may be monitored to record temperature changes and estimate groundwater origin. In the example chosen, the main water supply comes from a depth of at least 300 meters through relatively deep groundwater circulation within a major permeable fault zone. The influence of groundwater extraction is clearly identified through groundwater temperature monitoring. These examples illustrate the advantages and limitations of using heat and groundwater temperature measurements for fractured rock hydrology.

Geothermal Heating, Convective Flow and Ice Thickness on Mars

NASA Technical Reports Server (NTRS)

Rosenberg, N. D.; Travis, B. J.; Cuzzi, J.

2001-01-01

Our 3D calculations suggest that hydrothermal circulation may occur in the martian regolith and may significantly thin the surface ice layer on Mars at some locations due to the upwelling of warm convecting fluids driven solely by background geothermal heating. Additional information is contained in the original extended abstract.

Wire-packed heat exchangers for dilution refrigerators.

PubMed

Polturak, E; Rappaport, M; Rosenbaum, R

1978-03-01

Very simple wire-packed step heat exchangers for dilution refrigerators are described. No sintering is used in fabrication. Flow impedances and thermal resistance between the liquid and the copper wires are low. A refrigerator with five wire-packed heat exchangers in addition to a countercurrent heat exchanger attains a temperature of 11.4 mK with a single mixing chamber and 6.1 mK with two mixing chambers. High cooling power is achieved at modest (3)He circulation rates.

Numerical simulations of hydrothermal circulation resulting from basalt intrusions in a buried spreading center

USGS Publications Warehouse

Fisher, A.T.; Narasimhan, T.N.

1991-01-01

A two-dimensional, one by two-kilometer section through the seafloor was simulated with a numerical model to investigate coupled fluid and heat flow resulting from basalt intrusions in a buried spreading center. Boundary and initial conditions and physical properties of both sediments and basalt were constrained by field surveys and drilling in the Guaymas Basin, central Gulf of California. Parametric variations in these studies included sediment and basalt permeability, anisotropy in sediment permeability, and the size of heat sources. Faults were introduced through new intrusions both before and after cooling.Background heat input caused fluid convection at velocities ≤ 3 cm a−1 through shallow sediments. Eighty to ninety percent of the heat introduced at the base of the simulations exited through the upper, horizontal surface, even when the vertical boundaries were made permeable to fluid flow. The simulated injection of a 25–50 m thick basalt intrusion at a depth of 250 m resulted in about 10 yr of pore-fluid expulsion through the sea-floor in all cases, leaving the sediments above the intrusions strongly underpressured. A longer period of fluid recharge followed, sometimes accompanied by reductions in total seafloor heat output of 10% in comparison to pre-intrusion values. Additional discharge-recharge events were dispersed chaotically through the duration of the cooling period. These cycles in heat and fluid flow resulted from the response of the simulated system to a thermodynamic shock, the sudden emplacement of a large heat source, and not from mechanical displacement of sediments and pore fluids, which was not simulated.Water/rock mass ratios calculated from numerical simulations are in good agreement with geochemical estimates from materials recovered from the Guaymas Basin, assuming a bulk basalt permeability value of at least 10−17 m2/(10−2 mD). The addition of faults through intrusions and sediments in these simulations did not facilitate continuous, rapid venting. Increased heat input at the base of the faults resulted in temporarily greater fluid discharge, but the flow could not be sustained because the modeled system could not recharge cold fluid quickly enough to remove sufficient heat through the vents.

Design and Operation of a Cryogenic Nitrogen Pulsating Heat Pipe

NASA Astrophysics Data System (ADS)

Diego Fonseca, Luis; Miller, Franklin; Pfotenhauer, John

2015-12-01

We report the design, experimental setup and successful test results using an innovative passive cooling system called a “Pulsating Heat Pipe” (PHP) operating at temperatures ranging from 77 K to 80 K and using nitrogen as the working fluid. PHPs, which transfer heat by two phase flow mechanisms through a closed loop tubing have the advantage that no electrical pumps are needed to drive the fluid flow. In addition, PHPs have an advantage over copper straps and thermal conductors since they are lighter in weight, exhibit lower temperature gradients and have higher heat transfer rates. PHPs consist of an evaporator section, thermally anchored to a solid, where heat is received at the saturation temperature where the liquid portion of the two-phase flow evaporates, and a condenser where heat is rejected at the saturation temperature where the vapor is condensed. The condenser section in our experiment has been thermally interfaced to a CT cryocooler from SunPower that has a cooling capacity of 10 W at 77 K. Alternating regions of liquid slugs and small vapor plugs fill the capillary tubing, with the vapor regions contracting in the condenser section and expanding in the evaporator section due to an electric heater that will generate heat loads up to 10 W. This volumetric expansion and contraction provides the oscillatory flow of the fluid throughout the capillary tubing thereby transferring heat from one end to the other. The thermal performance and temperature characteristics of the PHP will be correlated as a function of average condenser temperature, PHP fill liquid ratio, and evaporator heat load. The experimental data show that the heat transfer between the evaporator and condenser sections can produce an effective thermal conductivity up to 35000 W/m-K at a 3.5 W heat load.

A Steady State and Quasi-Steady Interface Between the Generalized Fluid System Simulation Program and the SINDA/G Thermal Analysis Program

NASA Technical Reports Server (NTRS)

Schallhorn, Paul; Majumdar, Alok; Tiller, Bruce

2001-01-01

A general purpose, one dimensional fluid flow code is currently being interfaced with the thermal analysis program SINDA/G. The flow code, GFSSP, is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development is conducted in multiple phases. This paper describes the first phase of the interface which allows for steady and quasisteady (unsteady solid, steady fluid) conjugate heat transfer modeling.

Magnetohydrodynamics Carreau nanofluid flow over an inclined convective heated stretching cylinder with Joule heating

NASA Astrophysics Data System (ADS)

Khan, Imad; Shafquatullah; Malik, M. Y.; Hussain, Arif; Khan, Mair

Current work highlights the computational aspects of MHD Carreau nanofluid flow over an inclined stretching cylinder with convective boundary conditions and Joule heating. The mathematical modeling of physical problem yields nonlinear set of partial differential equations. A suitable scaling group of variables is employed on modeled equations to convert them into non-dimensional form. The integration scheme Runge-Kutta-Fehlberg on the behalf of shooting technique is utilized to solve attained set of equations. The interesting aspects of physical problem (linear momentum, energy and nanoparticles concentration) are elaborated under the different parametric conditions through graphical and tabular manners. Additionally, the quantities (local skin friction coefficient, local Nusselt number and local Sherwood number) which are responsible to dig out the physical phenomena in the vicinity of stretched surface are computed and delineated by varying controlling flow parameters.

The inviscid stability of supersonic flow past heated or cooled axisymmetric bodies

NASA Technical Reports Server (NTRS)

Shaw, Stephen J.; Duck, Peter W.

1992-01-01

The inviscid, linear, nonaxisymmetric, temporal stability of the boundary layer associated with the supersonic flow past axisymmetric bodies (with particular emphasis on long thin, straight circular cylinders), subject to heated or cooled wall conditions is investigated. The eigenvalue problem is computed in some detail for a particular Mach number or 3.8, revealing that the effect of curvature and the choice of wall conditions both have a significant effect on the stability of the flow. Both the asymptotic, large azimuthal wavenumber solution and the asymptotic, far downstream solution are obtained for the stability analysis and compared with numerical results. Additionally, asymptotic analyses valid for large radii of curvature with cooled/heated wall conditions are presented. In general, important differences were found to exist between the wall temperature conditions imposed and the adiabatic wall conditions considered previously.

The inviscid stability of supersonic flow past heated or cooled axisymmetric bodies

NASA Technical Reports Server (NTRS)

Shaw, Stephen J.; Duck, Peter W.

1990-01-01

The inviscid, linear, nonaxisymmetric, temporal stability of the boundary layer associated with the supersonic flow past axisymmetric bodies (with particular emphasis on long thin, straight circular cylinders), subject to heated or cooled wall conditions is investigated. The eigenvalue problem is computed in some detail for a particular Mach number or 3.8, revealing that the effect of curvature and the choice of wall conditions both have a significant effect on the stability of the flow. Both the asymptotic, large azimuthal wavenumber solution and the asymptotic, far downstream solution are obtained for the stability analysis and compared with numerical results. Additionally, asymptotic analyses valid for large radii of curvature with cooled/heated wall conditions, are presented. In general, important differences were found to exist between the wall temperature conditions imposed and the adiabatic wall conditions considered previously.

Unsteady Sisko magneto-nanofluid flow with heat absorption and temperature dependent thermal conductivity: A 3D numerical study

NASA Astrophysics Data System (ADS)

Khan, Masood; Ahmad, Latif; Gulzar, M. Mudassar

2018-03-01

The impact of temperature dependent thermal conductivity and convective surface conditions on unsteady 3D Sisko nanofluid flow over a stretching surface is studied in the presence of heat generation/absorption and magnetic field. The numerical solution of nonlinear coupled equations has been carried out to explore the properties of different physical profiles of the fluid flow with varying of parameters. Specifically, the application of generalized Biot numbers and heat generation/absorption parameter in the sketching of temperature and concentration profiles are explored. The effect of all three parameters is noticed in the increasing order for shear thinning (0 < n < 1) and for shear thickening (n > 1) fluids. Moreover, the influence of Biot number γ1 on heat and mass transfer rates, are found in the enhancement and diminishing conducts respectively, in both cases of shear thinning as well as shear thickening fluids and a reverse trend is observed with the variation of Biot number γ2 . Additionally, the present results are validated through skin friction, heat and mass transfer rate values with the comparable values in the existing previous values.

Additive erosion reduction influences in the turbulent boundary layer

NASA Astrophysics Data System (ADS)

Buckingham, A. C.

1981-05-01

Results of a sequence of flow, heat and mass transfer calculations are presented which theoretically characterize the erosive environment at the wall surface of refractory metal coated and uncoated gun barrels. The theoretical results include analysis of the wall surface temperature, heat flux, and shear stress time histories on thin (10 mil.) Cr, Mo, Nb, and Ta plated steel barrel walls as uncoated steel walls. The calculations combine effects of a number of separate processes which were previously (and purposely) studied individually. These include solid particle additive concentrations, gas wall thermochemical influences, and transient turbulent wall boundary layer flow with multicomponent molecular diffusion and reactions from interaction of propellant combustion and the eroding surface. The boundary layer model includes particulate additive concentrations as well as propellant combustion products, considered for the present to be in the local thermochemical equilibrium.

Low-cost Electromagnetic Heating Technology for Polymer Extrusion-based Additive Manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carter, William G.; Rios, Orlando; Akers, Ronald R.

To improve the flow of materials used in in polymer additive manufacturing, ORNL and Ajax Tocco created an induction system for heating fused deposition modeling (FDM) nozzles used in polymer additive manufacturing. The system is capable of reaching a temperature of 230 C, a typical nozzle temperature for extruding ABS polymers, in 17 seconds. A prototype system was built at ORNL and sent to Ajax Tocco who analyzed the system and created a finalized power supply. The induction system was mounted to a PrintSpace Altair desktop printer and used to create several test parts similar in quality to those createdmore » using a resistive heated nozzle.« less

Experimental investigation of convective heat transfer agumentation using Al2O3/water nanofluid in circular pipe

NASA Astrophysics Data System (ADS)

Chavan, Durgeshkumar; Pise, Ashok T.

2015-09-01

In the present paper, experimental study is performed to investigate convective heat transfer and flow characteristics of nanofluids through a circular tube. The heat transfer coefficient and friction factor of the γ-Al2O3-water nanofluid flowing through a pipe of 10 mm inner ID and 1 m in length, with constant wall temperature under turbulent flow conditions are investigated. Experiments are conducted with 30 nm size γ-Al2O3 nanoparticle with a volume fraction between 0.1 and to 1.0 and Reynolds number between 8,000 and 14,000. Experimental results emphasize the heat transfer enhancement with the increase in a Reynolds number or nanoparticle volume fraction. The maximum enhancement of 36 % in the heat transfer coefficient for a Reynolds number of 8,550, by using nanofluid with 1.0 vol% was observed compared with base fluid. Experimental measurement also shows the considerable increase in the pressure drop with small addition of nanoparticles in base fluid. Experimental results of nanofluids were compared with existing convective heat transfer correlations in the turbulent regime. Comparison shows that Maiga's correlation has close agreement with experimental results in comparison with Dittus Boelter correlation.

Using Heat Pulses for Quantifying 3d Seepage Velocity in Groundwater-Surface Water Interactions, Considering Source Size, Regime, and Dispersion

NASA Astrophysics Data System (ADS)

Zlotnik, V. A.; Tartakovsky, D. M.

2017-12-01

The study is motivated by rapid proliferation of field methods for measurements of seepage velocity using heat tracing and is directed to broadening their potential for studies of groundwater-surface water interactions, and hyporheic zone in particular. In vast majority, existing methods assume vertical or horizontal, uniform, 1D seepage velocity. Often, 1D transport assumed as well, and analytical models of heat transport by Suzuki-Stallman are heavily used to infer seepage velocity. However, both of these assumptions (1D flow and 1D transport) are violated due to the flow geometry, media heterogeneity, and localized heat sources. Attempts to apply more realistic conceptual models still lack full 3D view, and known 2D examples are treated numerically, or by making additional simplifying assumptions about velocity orientation. Heat pulse instruments and sensors already offer an opportunity to collect data sufficient for 3D seepage velocity identification at appropriate scale, but interpretation tools for groundwater-surface water interactions in 3D have not been developed yet. We propose an approach that can substantially improve capabilities of already existing field instruments without additional measurements. Proposed closed-form analytical solutions are simple and well suited for using in inverse modeling. Field applications and ramifications for applications, including data analysis are discussed. The approach simplifies data collection, determines 3D seepage velocity, and facilitates interpretation of relations between heat transport parameters, fluid flow, and media properties. Results are obtained using tensor properties of transport parameters, Green's functions, and rotational coordinate transformations using the Euler angles

Investigation of parabolic computational techniques for internal high-speed viscous flows

NASA Technical Reports Server (NTRS)

Anderson, O. L.; Power, G. D.

1985-01-01

A feasibility study was conducted to assess the applicability of an existing parabolic analysis (ADD-Axisymmetric Diffuser Duct), developed previously for subsonic viscous internal flows, to mixed supersonic/subsonic flows with heat addition simulating a SCRAMJET combustor. A study was conducted with the ADD code modified to include additional convection effects in the normal momentum equation when supersonic expansion and compression waves were present. It is concluded from the present study that for the class of problems where strong viscous/inviscid interactions are present a global iteration procedure is required.

Coupling of microprocesses and macroprocesses due to velocity shear: An application to the low-altitude ionosphere

NASA Astrophysics Data System (ADS)

Ganguli, G.; Keskinen, M. J.; Romero, H.; Heelis, R.; Moore, T.; Pollock, C.

1994-05-01

Recent observations indicate that low-altitude (below 1500 km) ion energization and thermal ion upwelling are colocated in the convective flow reversal region. In this region the convective velocity V(sub perpendicular) is generally small but spatial gradients in V(sub perpendicular) can be large. As a result, Joule heating is small. The observed high level of ion heating (few electron volts or more) cannot be explained by classical Joule heating alone but requires additional heating sources such as plasma waves. At these lower altitudes, sources of free energy are not obvious and hence the nature of ion energization remains ill understood. The high degree of correlation of ion heating with shear in the convective velocity (Tsunoda et al., 1989) is suggestive of an important role of velocity shear in this phenomenon. We provide more recent evidence for this correlation and show that even a small amount of velocity shear in the transverse flow is sufficient to excite a large-scale Kelvin-Helmholtz mode, which can nonlinearly steepen and give rise to highly stressed regions of strongly sheared flows. Futhermore, these stressed regions of strongly sheared flows may seed plasma waves in the range of ion cyclotron to lower hybrid frequencies, which are potential sources for ion heating. This novle two-step mechanism for ion energization is applied to typical observations of low-altitude thermal ion upwelling events.

Present-day geothermal characteristics of the Ordos Basin, western North China Craton: new findings from deep borehole steady-state temperature measurements

NASA Astrophysics Data System (ADS)

Gao, Peng; Qiu, Qianfeng; Jiang, Guangzheng; Zhang, Chao; Hu, Shengbiao; Lei, Yuhong; Wang, Xiangzeng

2018-03-01

Heat flow and associated thermal regimes are related to the tectonic evolution and geophysical properties of the lithosphere. The Ordos Basin is located in a tectonic transitional zone: areas to the east of the basin are characterized as tectonically active, while regions to the west of the basin are characterized as tectonically stable. It is of general interest to learn the geothermal characteristics of the basin in such tectonic conditions. To clarify the spatial variability of the present-day geothermal field across the basin and its implications, we report 13 terrestrial heat flow points based on the first systematic steady-state deep borehole temperature measurements in the basin. The new data together with existing data show that the geothermal gradients in the basin range from 12.6 to 42.3° C km-1 with a mean of 27.7 ± 5.3° C km-1; the terrestrial heat flow values range from 43.3 to 88.7 mW/m2 with a mean of 64.7 ± 8.9 mW/m2. Such values are higher than those of typical cratonic basins and lower than those of tectonically active areas. By using all these data in the basin and adjacent areas, we plot geothermal gradient and heat flow distribution maps. The maps reveal that the basin is cooling westward and northward. The distribution pattern of the geothermal field is consistent with the lithospheric thickness variation in the basin. This similarity suggests that the geothermal spatial variability of the Ordos Basin is mainly influenced by heat from the deep mantle. In the southeastern basin, we locate a positive geothermal anomaly caused by the convergence of heat flow in basement highs and the high radiogenic heat production. In addition, the high heat flow in the eastern basin is related to the intense uplift during the Cenozoic Era.

Present-day geothermal characteristics of the Ordos Basin, western North China Craton: new findings from deep borehole steady-state temperature measurements

NASA Astrophysics Data System (ADS)

Gao, Peng; Qiu, Qianfeng; Jiang, Guangzheng; Zhang, Chao; Hu, Shengbiao; Lei, Yuhong; Wang, Xiangzeng

2018-07-01

Heat flow and associated thermal regimes are related to the tectonic evolution and geophysical properties of the lithosphere. The Ordos Basin is located in a tectonic transitional zone: areas to the east of the basin are characterized as tectonically active, while regions to the west of the basin are characterized as tectonically stable. It is of general interest to learn the geothermal characteristics of the basin in such tectonic conditions. To clarify the spatial variability of the present-day geothermal field across the basin and its implications, we report 13 terrestrial heat flow points based on the first systematic steady-state deep borehole temperature measurements in the basin. The new data together with existing data show that the geothermal gradients in the basin range from 12.6 to 42.3 °C km-1 with a mean of 27.7 ± 5.3 °C km-1; the terrestrial heat flow values range from 43.3 to 88.7 mW m-2 with a mean of 64.7 ± 8.9 mW m-2. Such values are higher than those of typical cratonic basins and lower than those of tectonically active areas. By using all these data in the basin and adjacent areas, we plot geothermal gradient and heat flow distribution maps. The maps reveal that the basin is cooling westwards and northwards. The distribution pattern of the geothermal field is consistent with the lithospheric thickness variation in the basin. This similarity suggests that the geothermal spatial variability of the Ordos Basin is mainly influenced by heat from the deep mantle. In the southeastern basin, we locate a positive geothermal anomaly caused by the convergence of heat flow in basement highs and the high radiogenic heat production. In addition, the high heat flow in the eastern basin is related to the intense uplift during the Cenozoic Era.

Development of a new method for the noninvasive measurement of deep body temperature without a heater.

PubMed

Kitamura, Kei-Ichiro; Zhu, Xin; Chen, Wenxi; Nemoto, Tetsu

2010-01-01

The conventional zero-heat-flow thermometer, which measures the deep body temperature from the skin surface, is widely used at present. However, this thermometer requires considerable electricity to power the electric heater that compensates for heat loss from the probe; thus, AC power is indispensable for its use. Therefore, this conventional thermometer is inconvenient for unconstrained monitoring. We have developed a new dual-heat-flux method that can measure the deep body temperature from the skin surface without a heater. Our method is convenient for unconstrained and long-term measurement because the instrument is driven by a battery and its design promotes energy conservation. Its probe consists of dual-heat-flow channels with different thermal resistances, and each heat-flow-channel has a pair of IC sensors attached on its top and bottom. The average deep body temperature measurements taken using both the dual-heat-flux and then the zero-heat-flow thermometers from the foreheads of 17 healthy subjects were 37.08 degrees C and 37.02 degrees C, respectively. In addition, the correlation coefficient between the values obtained by the 2 methods was 0.970 (p<0.001). These results show that our method can be used for monitoring the deep body temperature as accurately as the conventional method, and it overcomes the disadvantage of the necessity of AC power supply. (c) 2009 IPEM. Published by Elsevier Ltd. All rights reserved.

Experimental results from plasma transport on Prototype-Material Plasma Exposure eXperiment and comparison with B2-Eirene modeling

NASA Astrophysics Data System (ADS)

Kafle, N.; Caneses, J. F.; Biewer, T. M.; Owen, L.; Showers, M.; Donovan, D.; Caughman, J. B.; Goulding, R. H.; Rapp, Juergen

2017-10-01

Proto-MPEX at ORNL is a linear plasma device that combines a helicon plasma source with additional microwave and RF heating to deliver high plasma heat and particle fluxes to a target. Double Langmuir probes and Thomson scattering are being used to measure local Te and ne at various radial and axial locations. A recently constructed Mach- double probe provides the added capability of simultaneously measuring Te, ne, and Mach number. With this diagnostic, it is possible to infer the plasma flow, particle flux, and convective heat flux at different locations along the plasma column in Proto-MPEX. Preliminary results show Mach numbers of 0.6 and 0.8 in either direction away from the helicon source, and no flow near the source for the case where the peak magnetic field was 1.0 T. In addition, the Thomson Scattering system has been upgraded to measure ne and Te profiles at two axial locations, upstream at the electron heating location and downstream close to the target. Measurements of particle flow and flux profiles, heat flux, and profiles of ne and Te will be discussed. The extensive coverage provided by these diagnostics permits data-constrained B2-Eirene modeling of the entire plasma column, and comparison with results of modeling of high density mode plasmas will be presented. Supported by the US. D.O.E. contract DE-AC05-00OR22725.

A completely automated flow, heat-capacity, calorimeter for use at high temperatures and pressures

NASA Astrophysics Data System (ADS)

Rogers, P. S. Z.; Sandarusi, Jamal

1990-11-01

An automated, flow calorimeter has been constructed to measure the isobaric heat capacities of concentrated, aqueous electrolyte solutions using a differential calorimetry technique. The calorimeter is capable of operation to 700 K and 40 MPa with a measurement accuracy of 0.03% relative to the heat capacity of the pure reference fluid (water). A novel design encloses the calorimeter within a double set of separately controlled, copper, adiabatic shields that minimize calorimeter heat losses and precisely control the temperature of the inlet fluids. A multistage preheat train, used to efficiently heat the flowing fluid, includes a counter-current heat exchanger for the inlet and outlet fluid streams in tandem with two calorimeter preheaters. Complete system automation is accomplished with a distributed control scheme using multiple processors, allowing the major control tasks of calorimeter operation and control, data logging and display, and pump control to be performed simultaneously. A sophisticated pumping strategy for the two separate syringe pumps allows continuous fluid delivery. This automation system enables the calorimeter to operate unattended except for the reloading of sample fluids. In addition, automation has allowed the development and implementation of an improved heat loss calibration method that provides calorimeter calibration with absolute accuracy comparable to the overall measurement precision, even for very concentrated solutions.

A study of wind effects on collector performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onur, N.; Hewitt, J.C. Jr.

1980-08-01

Convective heat transfer experiments have been run on flat-plate collectors for tilt angles ranging from the horizontal to the vertical and for five different flow velocities. Experimental data are used to evaluate the currently used models, namely, those of Jurges (1924), Drake (1948), and Sparrow et al (1970-79), and it is shown that although none of these models provides an exact fit, they do represent bounds for the present data. It is also shown that the effect of flow from the northern quadrants provides an additional heat loss reduction of 10 to 20%.

Modeling of high pressure arc-discharge with a fully-implicit Navier-Stokes stabilized finite element flow solver

NASA Astrophysics Data System (ADS)

Sahai, A.; Mansour, N. N.; Lopez, B.; Panesi, M.

2017-05-01

This work addresses the modeling of high pressure electric discharge in an arc-heated wind tunnel. The combined numerical solution of Poisson’s equation, radiative transfer equations, and the set of Favre-averaged thermochemical nonequilibrium Navier-Stokes equations allows for the determination of the electric, radiation, and flow fields, accounting for their mutual interaction. Semi-classical statistical thermodynamics is used to determine the plasma thermodynamic properties, while transport properties are obtained from kinetic principles with the Chapman-Enskog method. A multi-temperature formulation is used to account for thermal non-equilibrium. Finally, the turbulence closure of the flow equations is obtained by means of the Spalart-Allmaras model, which requires the solution of an additional scalar transport equation. A Streamline upwind Petrov-Galerkin stabilized finite element formulation is employed to solve the Navier-Stokes equation. The electric field equation is solved using the standard Galerkin formulation. A stable formulation for the radiative transfer equations is obtained using the least-squares finite element method. The developed simulation framework has been applied to investigate turbulent plasma flows in the 20 MW Aerodynamic Heating Facility at NASA Ames Research Center. The current model is able to predict the process of energy addition and re-distribution due to Joule heating and thermal radiation, resulting in a hot central core surrounded by colder flow. The use of an unsteady three-dimensional treatment also allows the asymmetry due to a dynamic electric arc attachment point in the cathode chamber to be captured accurately. The current work paves the way for detailed estimation of operating characteristics for arc-heated wind tunnels which are critical in testing thermal protection systems.

Comparison of Various Supersonic Turbine Tip Designs to Minimize Aerodynamic Loss and Tip Heating

NASA Technical Reports Server (NTRS)

Shyam, Vikram; Ameri, Ali

2012-01-01

The rotor tips of axial turbines experience high heat flux and are the cause of aerodynamic losses due to tip clearance flows, and in the case of supersonic tips, shocks. As stage loadings increase, the flow in the tip gap approaches and exceeds sonic conditions. This introduces effects such as shock-boundary layer interactions and choked flow that are not observed for subsonic tip flows that have been studied extensively in literature. This work simulates the tip clearance flow for a flat tip, a diverging tip gap and several contoured tips to assess the possibility of minimizing tip heat flux while maintaining a constant massflow from the pressure side to the suction side of the rotor, through the tip clearance. The Computational Fluid Dynamics (CFD) code GlennHT was used for the simulations. Due to the strong favorable pressure gradients the simulations assumed laminar conditions in the tip gap. The nominal tip gap width to height ratio for this study is 6.0. The Reynolds number of the flow is 2.4 x 10(exp 5) based on nominal tip width and exit velocity. A wavy wall design was found to reduce heat flux by 5 percent but suffered from an additional 6 percent in aerodynamic loss coefficient. Conventional tip recesses are found to perform far worse than a flat tip due to severe shock heating. Overall, the baseline flat tip was the second best performer. A diverging converging tip gap with a hole was found to be the best choice. Average tip heat flux was reduced by 37 percent and aerodynamic losses were cut by over 6 percent.

Heat transfer in rotating serpentine passages with selected model orientation for smooth or skewed trip walls

NASA Technical Reports Server (NTRS)

Johnson, B. V.; Wagner, J. H.; Steuber, G. D.; Yeh, F. C.

1993-01-01

Experiments were conducted to determine the effects of model orientation as well as buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. Turbine blades have internal coolant passage surfaces at the leading and trailing edges of the airfoil with surfaces at angles which are as large as +/- 50 to 60 degrees to the axis of rotation. Most of the previously-presented, multiple-passage, rotating heat transfer experiments have focused on radial passages aligned with the axis of rotation. Results from serpentine passages with orientations 0 and 45 degrees to the axis of rotation which simulate the coolant passages for the mid chord and trailing edge regions of the rotating airfoil are compared. The experiments were conducted with rotation in both directions to simulate serpentine coolant passages with the rearward flow of coolant or with the forward flow of coolant. The experiments were conducted for passages with smooth surfaces and with 45 degree trips adjacent to airfoil surfaces for the radial portion of the serpentine passages. At a typical flow condition, the heat transfer on the leading surfaces for flow outward in the first passage with smooth walls was twice as much for the model at 45 degrees compared to the model at 0 degrees. However, the differences for the other passages and with trips were less. In addition, the effects of buoyancy and Coriolis forces on heat transfer in the rotating passage were decreased with the model at 45 degrees, compared to the results at 0 degrees. The heat transfer in the turn regions and immediately downstream of the turns in the second passage with flow inward and in the third passage with flow outward was also a function of model orientation with differences as large as 40 to 50 percent occurring between the model orientations with forward flow and rearward flow of coolant.

Reentry heat transfer analysis of the space shuttle orbiter

NASA Technical Reports Server (NTRS)

Ko, W. L.; Quinn, R. D.; Gong, L.

1982-01-01

A structural performance and resizing finite element thermal analysis computer program was used in the reentry heat transfer analysis of the space shuttle. Two typical wing cross sections and a midfuselage cross section were selected for the analysis. The surface heat inputs to the thermal models were obtained from aerodynamic heating analyses, which assumed a purely turbulent boundary layer, a purely laminar boundary layer, separated flow, and transition from laminar to turbulent flow. The effect of internal radiation was found to be quite significant. With the effect of the internal radiation considered, the wing lower skin temperature became about 39 C (70 F) lower. The results were compared with fight data for space transportation system, trajectory 1. The calculated and measured temperatures compared well for the wing if laminar flow was assumed for the lower surface and bay one upper surface and if separated flow was assumed for the upper surfaces of bays other than bay one. For the fuselage, good agreement between the calculated and measured data was obtained if laminar flow was assumed for the bottom surface. The structural temperatures were found to reach their peak values shortly before touchdown. In addition, the finite element solutions were compared with those obtained from the conventional finite difference solutions.

Method and apparatus for fuel gas moisturization and heating

DOEpatents

Ranasinghe, Jatila; Smith, Raub Warfield

2002-01-01

Fuel gas is saturated with water heated with a heat recovery steam generator heat source. The heat source is preferably a water heating section downstream of the lower pressure evaporator to provide better temperature matching between the hot and cold heat exchange streams in that portion of the heat recovery steam generator. The increased gas mass flow due to the addition of moisture results in increased power output from the gas and steam turbines. Fuel gas saturation is followed by superheating the fuel, preferably with bottom cycle heat sources, resulting in a larger thermal efficiency gain compared to current fuel heating methods. There is a gain in power output compared to no fuel heating, even when heating the fuel to above the LP steam temperature.

Flow and heat transfer enhancement in tube heat exchangers

NASA Astrophysics Data System (ADS)

Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

2015-11-01

The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.

Unstart phenomena induced by flow choking in scramjet inlet-isolators

NASA Astrophysics Data System (ADS)

Im, Seong-kyun; Do, Hyungrok

2018-02-01

A review of recent research outcomes in downstream flow choking-driven unstart is presented. Unstart is a flow phenomenon at the inlet that severely reduces the air mass flow rate through the engine, causing a loss of thrust and considerable transient mechanical loading. Therefore, unstart in a scramjet engine crucially affects the design and the operation range of hypersonic vehicles. Downstream flow choking is known to be one of the major mechanisms inducing inlet unstart, as confirmed by recent scramjet-powered flight tests. The current paper examines recent research progress in identifying flow choking mechanisms that trigger unstart. Three different flow choking mechanisms are discussed: flow blockage, mass addition, and heat release from combustion reactions. Current research outcomes on the characteristic of unstarting flows, such as transient and quasi-steady motions, are reviewed for each flow choking mechanism. The characteristics of unstarted flows are described including Buzzing phenomena and oscillatory motions of unstarted shockwaves. Then, the state-of-the-art methods to predict, detect, and control unstart are presented. The review suggests that further investigations with high-enthalpy ground facilities will aid understanding of heat release-driven unstart.

Investigation on heat transfer analysis and its effect on a multi-mode, beam-wave interaction for a 140 GHz, MW-class gyrotron

NASA Astrophysics Data System (ADS)

Liu, Qiao; Liu, Yinghui; Chen, Zhaowei; Niu, Xinjian; Li, Hongfu; Xu, Jianhua

2018-04-01

The interaction cavity of a 140 GHz, 1 MW continuous wave gyrotron developed in UESTC will be loaded with a very large heat load in the inner surface during operation. In order to reduce the heat, the axial wedge grooves of the outside surface of the cavity are considered and employed as the heat radiation structure. Thermoanalysis and structural analysis were discussed in detail to obtain the effects of heat on the cavity. In thermoanalysis, the external coolant-flow rates ranging from 20 L/min to 50 L/min were considered, and the distribution of wall loading was loaded as the heat flux source. In structural analysis, the cavity's deformation caused by the loads of heat and pressure was calculated. Compared with a non-deformed cavity, the effects of deformation on the performance of a cavity were discussed. For a cold-cavity, the results show that the quality factor would be reduced by 72, 89, 99 and 171 at the flow rates of 50 L/min, 40 L/min, 30 L/min and 20 L/min, respectively. Correspondingly, the cold-cavity frequencies would be decreased by 0.13 GHz, 0.15 GHz, 0.19 GHz and 0.38 GHz, respectively. For a hot-cavity, the results demonstrate that the output port frequencies would be dropped down, but the offset would be gradually decreased with increasing coolant-flow rate. Meanwhile, the output powers would be reduced dramatically with decreasing coolant-flow rate. In addition, when the coolant-flow rate reaches 40 L/min, the output power and the frequency are just reduced by 30 kW and 0.151 GHz, respectively.

Enthalpy Distributions of Arc Jet Flow Based on Measured Laser Induced Fluorescence, Heat Flux and Stagnation Pressure Distributions

NASA Technical Reports Server (NTRS)

Suess, Leonard E.; Milhoan, James D.; Oelke, Lance; Godfrey, Dennis; Larin, Maksim Y.; Scott, Carl D.; Grinstead, Jay H.; DelPapa, Steven

2011-01-01

The centerline total enthalpy of arc jet flow is determined using laser induced fluorescence of oxygen and nitrogen atoms. Each component of the energy, kinetic, thermal, and chemical can be determined from LIF measurements. Additionally, enthalpy distributions are inferred from heat flux and pressure probe distribution measurements using an engineering formula. Average enthalpies are determined by integration over the radius of the jet flow, assuming constant mass flux and a mass flux distribution estimated from computational fluid dynamics calculations at similar arc jet conditions. The trends show favorable agreement, but there is an uncertainty that relates to the multiple individual measurements and assumptions inherent in LIF measurements.

Heat convection in a micro impinging jet system

NASA Astrophysics Data System (ADS)

Mai, John Dzung Hoang

2000-10-01

This thesis covers the development of an efficient micro impinging jet heat exchanger, using MEMS technology, to provide localized cooling for present and next generation microelectronic computer chips. Before designing an efficient localized heat exchanger, it is necessary to investigate fluid dynamics and heat transfer in the micro scale. MEMS technology has been used in this project because it is the only tool currently available that can provide a large array of batch-fabricated, micro-scale nozzles for localized cooling. Our investigation of potential MEMS heat exchanger designs begins with experiments that measure the pressure drops and temperature changes in a micro scale tubing system that will be necessary to carry fluid to the impingement point. Our basic MEMS model is a freestanding micro channel with integrated temperature microsensors. The temperature distribution along the channel in a vacuum is measured. The measured flow rates are compared with an analytical model developed for capillary flow that accounts for 2-D, slip and compressibility effects. The work is focused on obtaining correlations in the form of the Nussult number, the Reynolds number and a H/d geometric factor. A set of single MEMS nozzles have been designed to test heat transfer effectiveness as a function of nozzle diameter, ranging from 1.0 mm to 250 um. In addition, nozzle and slot array MEMS devices have been fabricated. In order to obtain quantitative measurements from these micron scale devices, a series of target temperature sensor chips were custom made and characterized for these experiments. The heat transfer characteristics of various MEMS nozzle configurations operating at various steady inlet pressures, at different heights above the heated substrate, have been characterized. These steady results showed that the average heat transfer coefficient, averaged over a 1 cm2 test area, was usually less than 0.035 W/cm 2K for any situation. However, the local heat transfer coefficient, as measured by a single 4mum x 4mum temperature sensor, was as high as 0.5 W/cm2K. Using a mechanical valve and piezo actuator to perturb the flow at frequencies from 10 Hz to 1 kHz, we identify that enhanced heat transfer can occur in an unsteady forced jet. The functional dependence of the enhanced heat transfer on the mean jet speed, perturbation level and perturbing frequency has been established. The expected trend that increased heat transfer at higher values of St number was noticed. In addition the effect of a confined and free jet geometry on an unsteady flow was observed.

Unconfined laminar nanofluid flow and heat transfer around a rotating circular cylinder in the steady regime

NASA Astrophysics Data System (ADS)

Bouakkaz, Rafik; Salhi, Fouzi; Khelili, Yacine; Quazzazi, Mohamed; Talbi, Kamel

2017-06-01

In this work, steady flow-field and heat transfer through a copper- water nanofluid around a rotating circular cylinder with a constant nondimensional rotation rate α varying from 0 to 5 was investigated for Reynolds numbers of 5-40. Furthermore, the range of nanoparticle volume fractions considered is 0-5%. The effect of volume fraction of nanoparticles on the fluid flow and heat transfer characteristics are carried out by using a finite-volume method based commercial computational fluid dynamics solver. The variation of the local and the average Nusselt numbers with Reynolds number, volume fractions, and rotation rate are presented for the range of conditions. The average Nusselt number is found to decrease with increasing value of the rotation rate for the fixed value of the Reynolds number and volume fraction of nanoparticles. In addition, rotation can be used as a drag reduction technique.

Conduction of thermal energy in the neighborhood of the earth's bow shock

NASA Technical Reports Server (NTRS)

Hohlfeld, R. G.

1976-01-01

The Rankine-Hugoniot equations for MHD shocks are generalized by the addition of a term to the energy conservation equation representing a nonzero heat flow in the plasma in the neighborhood of the shock. This generalization is found to be compatible with the assumption of infinite electrical conductivity. The effects of plasma waves in this treatment are of the order of the reciprocal Alfvenic Mach number squared and hence are neglected. The effect of alpha particles in the solar wind is discussed. Seven crossings of the earth's bow shock by Explorer 35 in lunar orbit are analyzed. Sufficient data are available so that the determination of a dimensionless parameter, psi, characterizing the heat-flow difference across the bow shock is possible. The values of psi indicate energy-flux densities due to heat flow which are a nonnegligible fraction of the total energy flux. Two possible interpretations of psi are discussed.

The optimization on flow scheme of helium liquefier with genetic algorithm

NASA Astrophysics Data System (ADS)

Wang, H. R.; Xiong, L. Y.; Peng, N.; Liu, L. Q.

2017-01-01

There are several ways to organize the flow scheme of the helium liquefiers, such as arranging the expanders in parallel (reverse Brayton stage) or in series (modified Brayton stages). In this paper, the inlet mass flow and temperatures of expanders in Collins cycle are optimized using genetic algorithm (GA). Results show that maximum liquefaction rate can be obtained when the system is working at the optimal parameters. However, the reliability of the system is not well due to high wheel speed of the first turbine. Study shows that the scheme in which expanders are arranged in series with heat exchangers between them has higher operation reliability but lower plant efficiency when working at the same situation. Considering both liquefaction rate and system stability, another flow scheme is put forward hoping to solve the dilemma. The three configurations are compared from different aspects, they are respectively economic cost, heat exchanger size, system reliability and exergy efficiency. In addition, the effect of heat capacity ratio on heat transfer efficiency is discussed. A conclusion of choosing liquefier configuration is given in the end, which is meaningful for the optimal design of helium liquefier.

Entropy generation minimization (EGM) of nanofluid flow by a thin moving needle with nonlinear thermal radiation

NASA Astrophysics Data System (ADS)

Waleed Ahmed Khan, M.; Ijaz Khan, M.; Hayat, T.; Alsaedi, A.

2018-04-01

Entropy generation minimization (EGM) and heat transport in nonlinear radiative flow of nanomaterials over a thin moving needle has been discussed. Nonlinear thermal radiation and viscous dissipation terms are merged in the energy expression. Water is treated as ordinary fluid while nanomaterials comprise titanium dioxide, copper and aluminum oxide. The nonlinear governing expressions of flow problems are transferred to ordinary ones and then tackled for numerical results by Built-in-shooting technique. In first section of this investigation, the entropy expression is derived as a function of temperature and velocity gradients. Geometrical and physical flow field variables are utilized to make it nondimensionalized. An entropy generation analysis is utilized through second law of thermodynamics. The results of temperature, velocity, concentration, surface drag force and heat transfer rate are explored. Our outcomes reveal that surface drag force and Nusselt number (heat transfer) enhanced linearly for higher nanoparticle volume fraction. Furthermore drag force decays for aluminum oxide and it enhances for copper nanoparticles. In addition, the lowest heat transfer rate is achieved for higher radiative parameter. Temperature field is enhanced with increase in temperature ratio parameter.

Single-side conduction modeling for high heat flux coolant channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, R.D. Sr.

In the development of plasma-facing components (PFCs), most investigators have erroneously postulated negligible water critical heat flux dependence on the coolant channel length-to-diameter (L/D) ratio above a constant value of L/D. Although encouraging results have been obtained in characterizing peaking factors for local two-dimensional boiling curves and critical heat flux, additional experimental data and theoretical model development are needed to validate the applicability to PFCs. Both these and related issues will affect the flow boiling correlation and data reduction associated with the development of PFCs for fusion reactors and other physical problems that are dependent on conduction modeling in themore » heat flux spectrum of applications. Both exact solutions and numerical conjugate analyses are presented for a one-side heated (OSH) geometry. The results show (a) the coexistence of three flow regimes inside an OSH circular geometry, (b) the correlational dependence of the inside wall heat flux and temperature, and (c) inaccuracies that could arise in some data reduction procedures.« less

Triaxial thermopile array geo-heat-flow sensor

DOEpatents

Carrigan, C.R.; Hardee, H.C.; Reynolds, G.D.; Steinfort, T.D.

1990-01-01

A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings. 6 figs.

CFD simulation of a screw compressor including leakage flows and rotor heating

NASA Astrophysics Data System (ADS)

Spille-Kohoff, Andreas, Dr.; Hesse, Jan; El Shorbagy, Ahmed

2015-08-01

Computational Fluid Dynamics (CFD) simulations have promising potential to become an important part in the development process of positive displacement (PD) machines. CFD delivers deep insights into the flow and thermodynamic behaviour of PD machines. However, the numerical simulation of such machines is more complex compared to dynamic pumps like turbines or fans. The fluid transport in size-changing chambers with very small clearances between the rotors, and between rotors and casing, demands complex meshes that change with each time step. Additionally, the losses due to leakage flows and the heat transfer to the rotors need high-quality meshes so that automatic remeshing is almost impossible. In this paper, setup steps and results for the simulation of a dry screw compressor are shown. The rotating parts are meshed with TwinMesh, a special hexahedral meshing program for gear pumps, gerotors, lobe pumps and screw compressors. In particular, these meshes include axial and radial clearances between housing and rotors, and beside the fluid volume the rotor solids are also meshed. The CFD simulation accounts for gas flow with compressibility and turbulence effects, heat transfer between gas and rotors, and leakage flows through the clearances. We show time- resolved results for torques, forces, interlobe pressure, mass flow, and heat flow between gas and rotors, as well as time- and space-resolved results for pressure, velocity, temperature etc. for different discharge ports and working points of the screw compressor. These results are also used as thermal loads for deformation simulations of the rotors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cirrito, A.J.

Combustion jet pumps ingest waste heat gases from power plant engines and boilers to boost their pressure for the ultimate low temperature utilization of the captured heat for heating homes, full-year hot houses, sterilization purposes, recreational hot water, absorption refrigeration and the like. Jet pump energy is sustained from the incineration of solids, liquids and gases and vapors or simply from burning fuels. This is the energy needed to transport the reaction products to the point of heat utilization and to optimize the heat transfer to that point. Sequent jet pumps raise and preserve energy levels. Crypto-steady and special jetmore » pumps increase pumping efficiency. The distribution conduit accepts fluidized solids, liquids, gases and vapors in multiphase flow. Temperature modulation and flow augmentation takes place by water injection. Macro solids such as dried sewage waste are removed by cyclone separation. Micro particles remain entrained and pass out with waste condensate just beyond each point of final heat utilization to recharge the water table. The non-condensible gases separated at this point are treated for pollution control. Further, jet pump reactions are controlled to yield fuel gas as necessary to power jet pumps or other use. In all these effects introduced sequentially, the available energy necessary to provide the flow energy, for the continuously distributed heating medium, is first extracted from fuel and fuel-like additions to the stream. As all energy, any way, finally converts to heat, which in this case is retained or recaptured in the flow, the captured heat is practically 90% available at the point of low temperature utilization. The jet pump for coal gasification is also disclosed as are examples of coal gasification and hydrogen production.« less

An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers

PubMed Central

Nellis, G. F.; Kelin, S. A.; Zhu, W.; Gianchandani, Y.

2010-01-01

Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid. PMID:20976021

An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers.

PubMed

White, M J; Nellis, G F; Kelin, S A; Zhu, W; Gianchandani, Y

2010-11-01

Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid.

Three-dimensional flow in the Florida platform: Theoretical analysis of Kohout convection at its type locality

USGS Publications Warehouse

Hughes, J.D.; Vacher, H. Leonard; Sanford, W.E.

2007-01-01

Kohout convection is the name given to the circulation of saline groundwater deep within carbonate platforms, first proposed by F.A. Kohout in the 1960s for south Florida. It is now seen as an Mg pump for dolomitization by seawater. As proposed by Kohout, cold seawater is drawn into the Florida platform from the deep Straits of Florida as part of a geothermally driven circulation in which the seawater then rises in the interior of the platform to mix and exit with the discharging meteoric water of the Floridan aquifer system. Simulation of the asymmetrically emergent Florida platform with the new three-dimensional (3-D), finite-element groundwater flow and transport model SUTRA-MS, which couples salinity- and temperature-dependent density variations, allows analysis of how much of the cyclic flow is due to geothermal heating (free convection) as opposed to mixing with meteoric water discharging to the shoreline (forced convection). Simulation of the system with and without geothermal heating reveals that the inflow of seawater from the Straits of Florida would be similar without the heat flow, but the distribution would differ significantly. The addition of heat flow reduces the asymmetry of the circulation: it decreases seawater inflows on the Atlantic side by 8% and on the Guff of Mexico side by half. The study illustrates the complex interplay of freshwater-saltwater mixing, geothermal heat flow, and projected dolomitization in complicated 3-D settings with asymmetric boundary conditions and realistic horizontal and vertical variations in hydraulic properties. ?? 2007 The Geological Society of America.

Effect of Cattaneo-Christov heat flux on buoyancy MHD nanofluid flow and heat transfer over a stretching sheet in the presence of Joule heating and thermal radiation impacts

NASA Astrophysics Data System (ADS)

Dogonchi, A. S.; Ganji, D. D.

2018-06-01

In this study, buoyancy MHD nanofluid flow and heat transfer over a stretching sheet in the presence of Joule heating and thermal radiation impacts, are studied. Cattaneo-Christov heat flux model instead of conventional Fourier's law of heat conduction is applied to investigate the heat transfer characteristics. A similarity transformation is used to transmute the governing momentum and energy equations into non-linear ordinary differential equations with the appropriate boundary conditions. The obtained non-linear ordinary differential equations are solved numerically. The impacts of diverse active parameters such as the magnetic parameter, the radiation parameter, the buoyancy parameter, the heat source parameter, the volume fraction of nanofluid and the thermal relaxation parameter are examined on the velocity and temperature profiles. In addition, the value of the Nusselt number is calculated and presented through figures. The results demonstrate that the temperature profile is lower in the case of Cattaneo-Christov heat flux model as compared to Fourier's law. Moreover, the Nusselt number raises with the raising volume fraction of nanofluid and it abates with the ascending the radiation parameter.

Coherent flow structures and heat transfer in a duct with electromagnetic forcing

NASA Astrophysics Data System (ADS)

Himo, Rawad; Habchi, Charbel

2018-04-01

Coherent vortices are generated electromagnetically in a square duct flow. The vortices are induced by a Lorentz force applied in a small section near the entrance of the duct. The flow structure complexity increases with the electromagnetic forcing since the primary vortices propagating along the duct detach to generate secondary smaller streamwise vortices and hairpin-like structures. The Reynolds number based on the mean flow velocity and hydraulic diameter is 500, and five cases were studied by varying the electromagnetic forcing. Even though this Reynolds number is relatively low, a periodic sequence of hairpin-like structure flow was observed for the high forcing cases. This mechanism enhances the mixing process between the different flow regions resulting in an increase in the thermal performances which reaches 66% relative to the duct flow without forcing. In addition to the flow complexity, lower forcing cases remained steady, unlike high Lorentz forces that induced periodic instabilities with a Strouhal number around 0.59 for the transient eddies. The effect of the flow structure on the heat transfer is analyzed qualitatively and quantitatively using numerical simulations based on the finite volume method. Moreover, proper orthogonal decomposition (POD) analysis was performed on the flow structures to evaluate the most energetic modes contributing in the flow. It is found from the POD analysis that the primary streamwise vortices and hairpin legs are the flow structures that are the most contributing to the heat transfer process.

A noninvasive optical system for the measurement of xylem and phloem sap flow in woody plants of small stem size.

PubMed

Helfter, Carole; Shephard, Jonathon D; Martinez-Vilalta, Jordi; Mencuccini, Maurizio; Hand, Duncan P

2007-02-01

Over the past 70 years, heat has been widely used as a tracer for estimating the flow of water in woody and herbaceous plants. However, most commercially available techniques for monitoring whole plant water use are invasive and the measurements are potentially flawed because of wounding of the xylem tissue. The study of photosynthate transport in the phloem remains in its infancy, and little information about phloem transport rates is available owing to the fragility of the vascular tissue. The aim of our study was to develop a compact, stand-alone non-invasive system allowing for direct detection of phloem and xylem sap movement. The proposed method uses a heat pulse as a tracer for sap flow. Heat is applied to the surface of the stem with a near-infrared laser source, and heat propagation is monitored externally by means of an infrared camera. Heat pulse velocities are determined from the thermometric data and related to the more useful quantity, mass flow rate. Simulation experiments on the xylem tissue of severed silver birch (Betula pendula Roth.) branch segments were performed to assess the feasibility of the proposed approach, highlight the characteristics of the technique and outline calibration strategies. Good agreement between imposed and measured flow rates was achieved leading to experimentation with live silver birch and oak (Quercus robur L.) saplings. It was demonstrated that water flow through xylem vessels can be monitored non-invasively on an intact stem with satisfactory accuracy despite simultaneous sugar transport in the phloem. In addition, it was demonstrated that the technique allows for unequivocal detection of phloem flow velocities.

Numerical Analysis of Convection/Transpiration Cooling

NASA Technical Reports Server (NTRS)

Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale

1999-01-01

An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux, high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary, layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.

Significant consequences of heat generation/absorption and homogeneous-heterogeneous reactions in second grade fluid due to rotating disk

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Qayyum, Sumaira; Alsaedi, Ahmed; Ahmad, Bashir

2018-03-01

Flow of second grade fluid by a rotating disk with heat and mass transfer is discussed. Additional effects of heat generation/absorption are also analyzed. Flow is also subjected to homogeneous-heterogeneous reactions. The convergence of computed solution is assured through appropriate choices of initial guesses and auxiliary parameters. Investigation is made for the effects of involved parameters on velocities (radial, axial, tangential), temperature and concentration. Skin friction and Nusselt number are also analyzed. Graphical results depict that an increase in viscoelastic parameter enhances the axial, radial and tangential velocities. Opposite behavior of temperature is observed for larger values of viscoelastic and heat generation/absorption parameters. Concentration profile is increasing function of Schmidt number, viscoelastic parameter and heterogeneous reaction parameter. Magnitude of skin friction and Nusselt number are enhanced for larger viscoelastic parameter.

[Application of three heat pulse technique-based methods to determine the stem sap flow].

PubMed

Wang, Sheng; Fan, Jun

2015-08-01

It is of critical importance to acquire tree transpiration characters through sap flow methodology to understand tree water physiology, forest ecology and ecosystem water exchange. Tri-probe heat pulse sensors, which are widely utilized in soil thermal parameters and soil evaporation measurement, were applied to implement Salix matsudana sap flow density (Vs) measurements via heat-ratio method (HRM), T-Max method (T-Max) and single-probe heat pulse probe (SHPP) method, and comparative analysis was conducted with additional Grainer's thermal diffusion probes (TDP) measured results. The results showed that, it took about five weeks to reach a stable measurement stage after TPHP installation, Vs measured with three methods in the early stage after installation was 135%-220% higher than Vs in the stable measurement stage, and Vs estimated via HRM, T-Max and SHPP methods were significantly linearly correlated with Vs estimated via TDP method, with R2 of 0.93, 0.73 and 0.91, respectively, and R2 for Vs measured by SHPP and HRM reached 0.94. HRM had relatively higher precision in measuring low rates and reverse sap flow. SHPP method seemed to be very promising to measure sap flow for configuration simplicity and high measuring accuracy, whereas it couldn' t distinguish directions of flow. T-Max method had relatively higher error in sap flow measurement, and it couldn' t measure sap flow below 5 cm3 · cm(-2) · h(-1), thus this method could not be used alone, however it could measure thermal diffusivity for calculating sap flow when other methods were imposed. It was recommended to choose a proper method or a combination of several methods to measure stem sap flow, based on specific research purpose.

Heat Transfer Enhancement for Finned-Tube Heat Exchangers with Vortex Generators: Experimental and Numerical Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Brien, James Edward; Sohal, Manohar Singh; Huff, George Albert

2002-08-01

A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numericalmore » modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.« less

Triaxial thermopile array geo-heat-flow sensor

DOEpatents

Carrigan, Charles R.; Hardee, Harry C.; Reynolds, Gerald D.; Steinfort, Terry D.

1992-01-01

A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers arranged in a vertical string. The transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings.

Heat Flow and Gas Hydrates on the Continental Margin of India: Building on Results from NGHP Expedition 01

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trehu, Anne; Kannberg, Peter

2011-06-30

The Indian National Gas Hydrate Program (NGHP) Expedition 01 presented the unique opportunity to constrain regional heat flow derived from seismic observations by using drilling data in three regions on the continental margin of India. The seismic bottom simulating reflection (BSR) is a well-documented feature in hydrate bearing sediments, and can serve as a proxy for apparent heat flow if data are available to estimate acoustic velocity and density in water and sediments, thermal conductivity, and seafloor temperature. Direct observations of temperature at depth and physical properties of the sediment obtained from drilling can be used to calibrate the seismicmore » observations, decreasing the uncertainty of the seismically-derived estimates. Anomalies in apparent heat flow can result from a variety of sources, including sedimentation, erosion, topographic refraction and fluid flow. We constructed apparent heat flow maps for portions of the Krishna-Godavari (K-G) basin, the Mahanadi basin, and the Andaman basin and modeled anomalies using 1-D conductive thermal models. Apparent heat flow values in the Krishna-Godavari (K-G) basin and Mahanadi basin are generally 0.035 to 0.055 watts per square meter (W/m2). The borehole data show an increase in apparent heat flow as water depth increases from 900 to 1500 m. In the SW part of the seismic grid, 1D modeling of the effect of sedimentation on heat flow shows that ~50% of the observed increase in apparent heat flow with increasing water depth can be attributed to trapping of sediments behind a "toe-thrust" ridge that is forming along the seaward edge of a thick, rapidly accumulating deltaic sediment pile. The remainder of the anomaly can be explained either by a decrease in thermal conductivity of the sediments filling the slope basin or by lateral advection of heat through fluid flow along stratigraphic horizons within the basin and through flexural faults in the crest of the anticline. Such flow probably plays a role in bringing methane into the ridge formed by the toe-thrust. Because of the small anomaly due to this process and the uncertainty in thermal conductivity, we did not model this process explicitly. In the NE part of the K-G basin seismic grid, a number of local heat flow lows and highs are observed, which can be attributed to topographic refraction and to local fluid flow along faults, respectively. No regional anomaly can be resolved. Because of lack of continuity between the K-G basin sites within the seismic grid and those ~70 km to the NE in water depths of 1200 to 1500 m, we do not speculate on the reason for higher heat flow at these depths. The Mahanadi basin results, while limited in geographic extent, are similar to those for the KG basin. The Andaman basin exhibits much lower apparent heat flow values, ranging from 0.015 to 0.025 W/m2. Heat flow here also appears to increase with increasing water depth. The very low heat flow here is among the lowest heat flow observed anywhere and gives rise to a very thick hydrate stability zone in the sediments. Through 1D models of sedimentation (with extremely high sedimentation rates as a proxy for tectonic thickening), we concluded that the very low heat flow can probably be attributed to the combined effects of high sedimentation rate, low thermal conductivity, tectonic thickening of sediments and the cooling effect of a subducting plate in a subduction zone forearc. Like for the K-G basin, much of the local variability can be attributed to topography. The regional increase in heat flow with water depth remains unexplained because the seismic grid available to us did not extend far enough to define the local tectonic setting of the slope basin controlling this observational pattern. The results are compared to results from other margins, both active and passive. While an increase in apparent heat flow with increasing water depth is widely observed, it is likely a result of different processes in different places. The very low heat flow due to sedimentation and tectonics in the Andaman basin is at the low end of global observations from forearc basins, possibly because of unusually high regional sedimentation rates and a high rate of tectonic deformation. In addition to providing an opportunity to follow up on preliminary results from NGHP-01, which was partially funded by DOE to increase understanding of submarine gas hydrates, a primary objective of this project was to provide training for a graduate student who had participated in the data acquisition as a technician. Our approach was to start with very simple analytic models to develop intuition about the relative importance of different parameters both as a learning exercise and to evaluate whether a more complex modeling effort could be constrained by the existing data.« less

Heat Flow and Gas Hydrates on the Continental Margin of India: Building on Results from NGHP Expedition 01

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anne Trehu; Peter Kannberg

2011-06-30

The Indian National Gas Hydrate Program (NGHP) Expedition 01 presented the unique opportunity to constrain regional heat flow derived from seismic observations by using drilling data in three regions on the continental margin of India. The seismic bottom simulating reflection (BSR) is a well-documented feature in hydrate bearing sediments, and can serve as a proxy for apparent heat flow if data are available to estimate acoustic velocity and density in water and sediments, thermal conductivity, and seafloor temperature. Direct observations of temperature at depth and physical properties of the sediment obtained from drilling can be used to calibrate the seismicmore » observations, decreasing the uncertainty of the seismically-derived estimates. Anomalies in apparent heat flow can result from a variety of sources, including sedimentation, erosion, topographic refraction and fluid flow. We constructed apparent heat flow maps for portions of the Krishna-Godavari (K-G) basin, the Mahanadi basin, and the Andaman basin and modeled anomalies using 1-D conductive thermal models. Apparent heat flow values in the Krishna-Godavari (K-G) basin and Mahanadi basin are generally 0.035 to 0.055 watts per square meter (W/m{sup 2}). The borehole data show an increase in apparent heat flow as water depth increases from 900 to 1500 m. In the SW part of the seismic grid, 1D modeling of the effect of sedimentation on heat flow shows that {approx}50% of the observed increase in apparent heat flow with increasing water depth can be attributed to trapping of sediments behind a 'toe-thrust' ridge that is forming along the seaward edge of a thick, rapidly accumulating deltaic sediment pile. The remainder of the anomaly can be explained either by a decrease in thermal conductivity of the sediments filling the slope basin or by lateral advection of heat through fluid flow along stratigraphic horizons within the basin and through flexural faults in the crest of the anticline. Such flow probably plays a role in bringing methane into the ridge formed by the toe-thrust. Because of the small anomaly due to this process and the uncertainty in thermal conductivity, we did not model this process explicitly. In the NE part of the K-G basin seismic grid, a number of local heat flow lows and highs are observed, which can be attributed to topographic refraction and to local fluid flow along faults, respectively. No regional anomaly can be resolved. Because of lack of continuity between the K-G basin sites within the seismic grid and those {approx}70 km to the NE in water depths of 1200 to 1500 m, we do not speculate on the reason for higher heat flow at these depths. The Mahanadi basin results, while limited in geographic extent, are similar to those for the K-G basin. The Andaman basin exhibits much lower apparent heat flow values, ranging from 0.015 to 0.025 W/m{sup 2}. Heat flow here also appears to increase with increasing water depth. The very low heat flow here is among the lowest heat flow observed anywhere and gives rise to a very thick hydrate stability zone in the sediments. Through 1D models of sedimentation (with extremely high sedimentation rates as a proxy for tectonic thickening), we concluded that the very low heat flow can probably be attributed to the combined effects of high sedimentation rate, low thermal conductivity, tectonic thickening of sediments and the cooling effect of a subducting plate in a subduction zone forearc. Like for the K-G basin, much of the local variability can be attributed to topography. The regional increase in heat flow with water depth remains unexplained because the seismic grid available to us did not extend far enough to define the local tectonic setting of the slope basin controlling this observational pattern. The results are compared to results from other margins, both active and passive. While an increase in apparent heat flow with increasing water depth is widely observed, it is likely a result of different processes in different places. The very low heat flow due to sedimentation and tectonics in the Andaman basin is at the low end of global observations from forearc basins, possibly because of unusually high regional sedimentation rates and a high rate of tectonic deformation. In addition to providing an opportunity to follow up on preliminary results from NGHP-01, which was partially funded by DOE to increase understanding of submarine gas hydrates, a primary objective of this project was to provide training for a graduate student who had participated in the data acquisition as a technician. Our approach was to start with very simple analytic models to develop intuition about the relative importance of different parameters both as a learning exercise and to evaluate whether a more complex modeling effort could be constrained by the existing data.« less

Heat transfer, friction, and rheological characteristics of antimisting kerosene

NASA Technical Reports Server (NTRS)

Matthys, E.; Sarohia, V.

1985-01-01

Experiments were performed to determine the skin friction and heat transfer behavior of antimisting kerosene (AMK) in pipe flows. The additive used was FM-9. Based on the results of the experiments, which identify high viscosity and viscoelasticity for AMK, it is recommended that AMK be degraded. Sufficient degradation produces behavior similar to that of jet A.

Tables of critical-flow functions and thermodynamic properties for methane and computational procedures for both methane and natural gas

NASA Technical Reports Server (NTRS)

Johnson, R. C.

1972-01-01

Procedures for calculating the mass flow rate of methane and natural gas through nozzles are given, along with the FORTRAN 4 subroutines used to make these calculations. Three sets of independent variables are permitted in these routines. In addition to the plenum pressure and temperature, the third independent variable is either nozzle exit pressure, Mach number, or temperature. A critical-flow factor that becomes a convenient means for determining the mass flow rate of methane through critical-flow nozzles is tabulated. Other tables are included for nozzle throat velocity and critical pressure, density, and temperature ratios, along with some thermodynamic properties of methane, including compressibility factor, enthalpy, entropy, specific heat, specific-heat ratio, and speed of sound. These tabulations cover a temperature range from 120 to 600 K and pressures to 3 million N/sq m.

Microwave and continuous flow technologies in drug discovery.

PubMed

Sadler, Sara; Moeller, Alexander R; Jones, Graham B

2012-12-01

Microwave and continuous flow microreactors have become mainstream heating sources in contemporary pharmaceutical company laboratories. Such technologies will continue to benefit from design and engineering improvements, and now play a key role in the drug discovery process. The authors review the applications of flow- and microwave-mediated heating in library, combinatorial, solid-phase, metal-assisted, and protein chemistries. Additionally, the authors provide a description of the combination of microwave and continuous flow platforms, with applications in the preparation of radiopharmaceuticals and in drug candidate development. Literature reviewed is chiefly 2000 - 2012, plus key citations from earlier reports. With the advent of microwave irradiation, reactions that normally took days to complete can now be performed in a matter of minutes. Coupled with the introduction of continuous flow microreactors, pharmaceutical companies have an easy way to improve the greenness and efficiency of many synthetic operations. The combined force of these technologies offers the potential to revolutionize discovery and manufacturing processes.

Arrays of flow channels with heat transfer embedded in conducting walls

DOE PAGES

Bejan, A.; Almerbati, A.; Lorente, S.; ...

2016-04-20

Here we illustrate the free search for the optimal geometry of flow channel cross-sections that meet two objectives simultaneously: reduced resistances to heat transfer and fluid flow. The element cross section and the wall material are fixed, while the shape of the fluid flow opening, or the wetted perimeter is free to vary. Two element cross sections are considered, square and equilateral triangular. We find that the two objectives are best met when the solid wall thickness is uniform, i.e., when the wetted perimeters are square and triangular, respectively. In addition, we consider arrays of square elements and triangular elements,more » on the basis of equal mass flow rate per unit of array cross sectional area. The conclusion is that the array of triangular elements meets the two objectives better than the array of square elements.« less

The effect of heat and moisture exchanger and gas flow on humidity and temperature in a circle anaesthetic system.

PubMed

Poopalalingam, R; Goh, M H; Chan, Y W

2002-11-01

The aim of the study was to measure the humidity and temperature of the inspired gas in a circle absorber system at fresh gas flows of 11/min and 31/min and assess the need of a heat and moisture exchanger (HME). This prospective randomised controlled study received the Hospital Ethics Committee approval and informed consent. Forty adult ASA 1 and 11 patients were randomised into four groups to receive with or without HME fresh gas flow of 1L/min or 3L/min. Temperature and the relative humidity readings were taken at the start and every 10 minutes for the first hour of anaesthesia. There was a significantly higher relative humidity, absolute humidity and temperatures of the inspired gases at fresh gas flow of 1L/min and 3L/min with a HME compared to 3L/min without HME. Patients receiving fresh gas flows of lL/min had higher relative and absolute humidity than patients with fresh gas flows of 3L/min. However, the addition of the HME improved the absolute and relative humidity of the inspired gas in patients receiving fresh gas flow of 3l/min to a comparable level. However, the addition of a HME to a fresh gas flow of 1L/min did not significantly improve the humidity of the inspired gas. This suggests that the inherent humidifying property of the circle system at low fresh gas flow of 1L/min was sufficient in short surgeries lasting less than one hour and that the addition of a HME may not be necessary.

Magnetic Heat Pump Containing Flow Diverters

NASA Technical Reports Server (NTRS)

Howard, Frank S.

1995-01-01

Proposed magnetic heat pump contains flow diverters for suppression of undesired flows. If left unchecked, undesired flows mix substantial amounts of partially heated and partially cooled portions of working fluid, effectively causing leakage of heat from heated side to cooled side. By reducing leakage of heat, flow diverters increase energy efficiency of magnetic heat pump, potentially offering efficiency greater than compressor-driven refrigerator.

Geothermal regime and Jurassic source rock maturity of the Junggar basin, northwest China

NASA Astrophysics Data System (ADS)

Nansheng, Qiu; Zhihuan, Zhang; Ershe, Xu

2008-01-01

We analyze the thermal gradient distribution of the Junggar basin based on oil-test and well-logging temperature data. The basin-wide average thermal gradient in the depth interval of 0-4000 m is 22.6 °C/km, which is lower than other sedimentary basins in China. We report 21 measured terrestrial heat flow values based on detailed thermal conductivity data and systematical steady-state temperature data. These values vary from 27.0 to 54.1 mW/m 2 with a mean of 41.8 ± 7.8 mW/m 2. The Junggar basin appears to be a cool basin in terms of its thermal regime. The heat flow distribution within the basin shows the following characteristics. (1) The heat flow decreases from the Luliang Uplift to the Southern Depression; (2) relatively high heat flow values over 50 mW/m 2 are confined to the northern part of the Eastern Uplift and the adjacent parts of the Eastern Luliang Uplift and Central Depression; (3) The lowest heat flow of smaller than 35 mW/m 2 occurs in the southern parts of the basin. This low thermal regime of the Junggar basin is consistent with the geodynamic setting, the extrusion of plates around the basin, the considerably thick crust, the dense lithospheric mantle, the relatively stable continental basement of the basin, low heat generation and underground water flow of the basin. The heat flow of this basin is of great significance to oil exploration and hydrocarbon resource assessment, because it bears directly on issues of petroleum source-rock maturation. Almost all oil fields are limited to the areas of higher heat flows. The relatively low heat flow values in the Junggar basin will deepen the maturity threshold, making the deep-seated widespread Permian and Jurassic source rocks in the Junggar basin favorable for oil and gas generation. In addition, the maturity evolution of the Lower Jurassic Badaowan Group (J 1b) and Middle Jurassic Xishanyao Group (J 2x) were calculated based on the thermal data and burial depth. The maturity of the Jurassic source rocks of the Central Depression and Southern Depression increases with depth. The source rocks only reached an early maturity with a R0 of 0.5-0.7% in the Wulungu Depression, the Luliang Uplift and the Western Uplift, whereas they did not enter the maturity window ( R0 < 0.5%) in the Eastern Uplift of the basin. This maturity evolution will provide information of source kitchen for the Jurassic exploration.

Numerical Analysis of a Pulse Detonation Cross Flow Heat Load Experiment

NASA Technical Reports Server (NTRS)

Paxson, Daniel E.; Naples, Andrew .; Hoke, John L.; Schauer, Fred

2011-01-01

A comparison between experimentally measured and numerically simulated, time-averaged, point heat transfer rates in a pulse detonation (PDE) engine is presented. The comparison includes measurements and calculations for heat transfer to a cylinder in crossflow and to the tube wall itself using a novel spool design. Measurements are obtained at several locations and under several operating conditions. The measured and computed results are shown to be in substantial agreement, thereby validating the modeling approach. The model, which is based in computational fluid dynamics (CFD) is then used to interpret the results. A preheating of the incoming fuel charge is predicted, which results in increased volumetric flow and subsequent overfilling. The effect is validated with additional measurements.

An empirical investigation on thermal characteristics and pressure drop of Ag-oil nanofluid in concentric annular tube

NASA Astrophysics Data System (ADS)

Abbasian Arani, A. A.; Aberoumand, H.; Aberoumand, S.; Jafari Moghaddam, A.; Dastanian, M.

2016-08-01

In this work an experimental study on Silver-oil nanofluid was carried out in order to present the laminar convective heat transfer coefficient and friction factor in a concentric annulus with constant heat flux boundary condition. Silver-oil nanofluid prepared by Electrical Explosion of Wire technique with no nanoparticles agglomeration during nanofluid preparation process and experiments. The average sizes of particles were 20 nm. Nanofluids with various particle Volume fractions of 0.011, 0.044 and 0.171 vol% were employed. The nanofluid flowing between the tubes is heated by an electrical heating coil wrapped around it. The effects of different parameters such as flow Reynolds number, tube diameter ratio and nanofluid particle concentration on heat transfer coefficient are studied. Results show that, heat transfer coefficient increased by using nanofluid instead of pure oil. Maximum enhancement of heat transfer coefficient occurs in 0.171 vol%. In addition the results showed that, there are slight increases in pressure drop of nanofluid by increasing the nanoparticle concentration of nanofluid in compared to pure oil.

Heat Flow, Regional Geophysics and Lithosphere Structure In The Czech Republic

NASA Astrophysics Data System (ADS)

Safanda, J.; Cermak, V.; Kresl, M.; Dedecek, P.

Paper summarises and critically revises heat flow data that have been collected in the Czech Republic to date. The regional heat flow density map was prepared in view of all existing heat flow data completed with the similar in the surrounding countries and taking into consideration also temperature measurements in deep boreholes. Crustal temperature profiles were calculated by using the available geological information, results of deep seismic sounding and the laboratory data on radiogenic heat produc- tion and thermal conductivity. Special attention was paid to numerous temperature logs in two sedimentary basins, namely in the Cheb and Ostrava-Karvina coal basins, for which detailed heat flow patterns were proposed. Relationships between heat flow distribution and the crustal/lithosphere evolution, between heat flow and the heat pro- duction of the crustal rocks, heat flow and crustal thickness and the steady-state vs. transient heat transport are discussed.

Extremely high-power-density atmospheric-pressure thermal plasma jet generated by the nitrogen-boosted effect

NASA Astrophysics Data System (ADS)

Hanafusa, Hiroaki; Nakashima, Ryosuke; Nakano, Wataru; Higashi, Seiichiro

2018-06-01

In this study, the effect of N2 addition to an atmospheric-pressure Ar thermal plasma jet (TPJ) on ultrarapid heating was investigated. With increasing N2 flow rate, a boost of arc voltage to ∼36 V was observed, which significantly improved heating characteristics. As a result, a drastic power density increase from 10 to 125 kW/cm2 was achieved with the addition of 2.0 L/min N2 to 3.0 L/min Ar. The results of optical emission analysis and heating characteristics evaluation implied that dissociation and recombination of N2 molecules and the high thermal transport property of nitrogen gas play important roles in the increase in TPJ power density. Furthermore, we obtained TPJ extension with N2 addition that reached 300 mm, and it showed spatial enhancement of heat transport characteristics.

Combined effects of slip and convective boundary condition on MHD 3D stretched flow of nanofluid through porous media inspired by non-linear thermal radiation

NASA Astrophysics Data System (ADS)

Nayak, M. K.; Shaw, Sachin; Pandey, V. S.; Chamkha, Ali J.

2018-02-01

In the present study, the main concern is to investigate the magnetohydrodynamic nanofluid flow subject to porous matrix and convective heating past a permeable linear stretching sheet. In addition, the influence of velocity slip, viscous dissipation, Joule heating and non-linear thermal radiation are considered. A new micro-convection model known as the Patel model is implemented for considerable enhancement of the thermal conductivity and hence, the heat transfer capability of nanofluids. Moreover, a convective heat transfer model is introduced where the bottom surface of the sheet gets heated due to a convection mechanism from a hot fluid of particular temperature. The numerical results of the transformed governing differential equations have been obtained by using fourth-order Runge-Kutta method along with shooting approach and secant method is used for better approximation. In the present analysis, base fluids such as water and Ethylene glycol and Copper, Silver and Aluminum oxide nanoparticles are considered. Results of the present investigation show that inclusion of porous matrix contributes to slow down the fluid velocity and diminution of wall shear stress (axial as well as transverse). Drag force due to magnetic field strength, velocity slip and imposed fluid suction impede the fluid motion and upsurge the heat transfer rate from the surface. In addition, rise in viscous dissipation widens the thermal boundary layer.

Hot Films on Ceramic Substrates for Measuring Skin Friction

NASA Technical Reports Server (NTRS)

Noffz, Greg; Leiser, Daniel; Bartlett, Jim; Lavine, Adrienne

2003-01-01

Hot-film sensors, consisting of a metallic film on an electrically nonconductive substrate, have been used to measure skin friction as far back as 1931. A hot film is maintained at an elevated temperature relative to the local flow by passing an electrical current through it. The power required to maintain the specified temperature depends on the rate at which heat is transferred to the flow. The heat transfer rate correlates to the velocity gradient at the surface, and hence, with skin friction. The hot-film skin friction measurement method is most thoroughly developed for steady-state conditions, but additional issues arise under transient conditions. Fabricating hot-film substrates using low-thermal-conductivity ceramics can offer advantages over traditional quartz or polyester-film substrates. First, a low conductivity substrate increases the fraction of heat convected away by the fluid, thus increasing sensitivity to changes in flow conditions. Furthermore, the two-part, composite nature of the substrate allows the installation of thermocouple junctions just below the hot film, which can provide an estimate of the conduction heat loss.

Characteristics of melting heat transfer during flow of Carreau fluid induced by a stretching cylinder.

PubMed

Hashim; Khan, Masood; Saleh Alshomrani, Ali

2017-01-01

This article provides a comprehensive analysis of the energy transportation by virtue of the melting process of high-temperature phase change materials. We have developed a two-dimensional model for the boundary layer flow of non-Newtonian Carreau fluid. It is assumed that flow is caused by stretching of a cylinder in the axial direction by means of a linear velocity. Adequate local similarity transformations are employed to determine a set of non-linear ordinary differential equations which govern the flow problem. Numerical solutions to the resultant non-dimensional boundary value problem are computed via the fifth-order Runge-Kutta Fehlberg integration scheme. The solutions are captured for both zero and non-zero curvature parameters, i.e., for flow over a flat plate or flow over a cylinder. The flow and heat transfer attributes are witnessed to be prompted in an intricate manner by the melting parameter, the curvature parameter, the Weissenberg number, the power law index and the Prandtl number. We determined that one of the possible ways to boost the fluid velocity is to increase the melting parameter. Additionally, both the velocity of the fluid and the momentum boundary layer thickness are higher in the case of flow over a stretching cylinder. As expected, the magnitude of the skin friction and the rate of heat transfer decrease by raising the values of the melting parameter and the Weissenberg number.

Heavy liquid metals: Research programs at PSI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeda, Y.

1996-06-01

The author describes work at PSI on thermohydraulics, thermal shock, and material tests for mechnical properties. In the presentation, the focus is on two main programs. (1) SINQ LBE target: The phase II study program for SINQ is planned. A new LBE loop is being constructed. The study has the following three objectives: (a) Pump study - design work on an electromagnetic pump to be integrated into the target. (b) Heat pipe performance test - the use of heat pipes as an additional component of the target cooling system is being considered, and it may be a way to futhermore » decouple the liquid metal and water coolant loops. (c) Mixed convection experiment - in order to find an optimal configuration of the additional flow guide for window cooling, mixed convection around the window is to be studied. The experiment will be started using water and then with LBE. (2) ESS Mercury target: For ESS target study, the following experimental studies are planned, some of which are exampled by trial experiments. (a) Flow around the window: Flow mapping around the hemi-cylindrical window will be made for optimising the flow channels and structures, (b) Geometry optimisation for minimizing a recirculation zone behind the edge of the flow separator, (c) Flow induced vibration and buckling problem for a optimised structure of the flow separator and (d) Gas-liquid two-phase flow will be studied by starting to establish the new experimental method of measuring various kinds of two-phase flow characteristics.« less

Development of a Nonequilibrium Radiative Heating Prediction Method for Coupled Flowfield Solutions

NASA Technical Reports Server (NTRS)

Hartung, Lin C.

1991-01-01

A method for predicting radiative heating and coupling effects in nonequilibrium flow-fields has been developed. The method resolves atomic lines with a minimum number of spectral points, and treats molecular radiation using the smeared band approximation. To further minimize computational time, the calculation is performed on an optimized spectrum, which is computed for each flow condition to enhance spectral resolution. Additional time savings are obtained by performing the radiation calculation on a subgrid optimally selected for accuracy. Representative results from the new method are compared to previous work to demonstrate that the speedup does not cause a loss of accuracy and is sufficient to make coupled solutions practical. The method is found to be a useful tool for studies of nonequilibrium flows.

Wall-wake velocity profile for compressible non-adiabatic flows

NASA Technical Reports Server (NTRS)

Sun, C. C.; Childs, M. E.

1975-01-01

A form of the wall-wake profile, which is applicable to flows with heat transfer, and for which a variation in y = O at y = delta, was suggested. The modified profile, which takes into account the effect of turbulent Prandtl number, was found to provide a good representation of experimental data for a wide range numbers and heat transfer. The Cf values which are determined by a least squares fit of the profile to the data agree well with values which were measured by the floating element technique. In addition, the values of delta determined by the fit correspond more closely to the outer edge of the viscous flow region than those obtained with earlier versions of the wall-wake profile.

Very high pressure liquid chromatography using core-shell particles: quantitative analysis of fast gradient separations without post-run times.

PubMed

Stankovich, Joseph J; Gritti, Fabrice; Stevenson, Paul G; Beaver, Lois A; Guiochon, Georges

2014-01-17

Five methods for controlling the mobile phase flow rate for gradient elution analyses using very high pressure liquid chromatography (VHPLC) were tested to determine thermal stability of the column during rapid gradient separations. To obtain rapid separations, instruments are operated at high flow rates and high inlet pressure leading to uneven thermal effects across columns and additional time needed to restore thermal equilibrium between successive analyses. The purpose of this study is to investigate means to minimize thermal instability and obtain reliable results by measuring the reproducibility of the results of six replicate gradient separations of a nine component RPLC standard mixture under various experimental conditions with no post-run times. Gradient separations under different conditions were performed: constant flow rates, two sets of constant pressure operation, programmed flow constant pressure operation, and conditions which theoretically should yield a constant net heat loss at the column's wall. The results show that using constant flow rates, programmed flow constant pressures, and constant heat loss at the column's wall all provide reproducible separations. However, performing separations using a high constant pressure with programmed flow reduces the analysis time by 16% compared to constant flow rate methods. For the constant flow rate, programmed flow constant pressure, and constant wall heat experiments no equilibration time (post-run time) was required to obtain highly reproducible data. Copyright © 2013 Elsevier B.V. All rights reserved.

Numerical comparison of convective heat transfer augmentation devices used in cooling channels of hypersonic vehicles

NASA Astrophysics Data System (ADS)

Maldonado, Jaime J.

1994-04-01

Hypersonic vehicles are exposed to extreme thermal conditions compared to subsonic aircraft; therefore, some level of thermal management is required to protect the materials used. Normally, hypersonic vehicles experience the highest temperatures in the nozzle throat, and aircraft and propulsion system leading edges. Convective heat transfer augmentation techniques can be used in the thermal management system to increase heat transfer of the cooling channels in those areas. The techniques studied in this report are pin-fin, offset-fin, ribbed and straight roughened channel. A smooth straight channel is used as the baseline for comparing the techniques. SINDA '85, a lumped parameter finite difference thermal analyzer, is used to model the channels. Subroutines are added to model the fluid flow assuming steady one dimensional compressible flow with heat addition and friction. Correlations for convective heat transfer and friction are used in conjunction with the fluid flow analysis mentioned. As expected, the pin-fin arrangement has the highest heat transfer coefficient and the largest pressure drop. All the other devices fall in between the pin-fin and smooth straight channel. The selection of the best heat augmentation method depends on the design requirements. A good approach may be a channel using a combination of the techniques. For instance, several rows of pin-fins may be located at the region of highest heat flux, surrounded by some of the other techniques. Thus, the heat transfer coefficient is maximized at the region of highest heat flux while the pressure drop is not excessive.

Numerical comparison of convective heat transfer augmentation devices used in cooling channels of hypersonic vehicles

NASA Technical Reports Server (NTRS)

Maldonado, Jaime J.

1994-01-01

Hypersonic vehicles are exposed to extreme thermal conditions compared to subsonic aircraft; therefore, some level of thermal management is required to protect the materials used. Normally, hypersonic vehicles experience the highest temperatures in the nozzle throat, and aircraft and propulsion system leading edges. Convective heat transfer augmentation techniques can be used in the thermal management system to increase heat transfer of the cooling channels in those areas. The techniques studied in this report are pin-fin, offset-fin, ribbed and straight roughened channel. A smooth straight channel is used as the baseline for comparing the techniques. SINDA '85, a lumped parameter finite difference thermal analyzer, is used to model the channels. Subroutines are added to model the fluid flow assuming steady one dimensional compressible flow with heat addition and friction. Correlations for convective heat transfer and friction are used in conjunction with the fluid flow analysis mentioned. As expected, the pin-fin arrangement has the highest heat transfer coefficient and the largest pressure drop. All the other devices fall in between the pin-fin and smooth straight channel. The selection of the best heat augmentation method depends on the design requirements. A good approach may be a channel using a combination of the techniques. For instance, several rows of pin-fins may be located at the region of highest heat flux, surrounded by some of the other techniques. Thus, the heat transfer coefficient is maximized at the region of highest heat flux while the pressure drop is not excessive.

Inductively coupled plasma torch with laminar flow cooling

DOEpatents

Rayson, Gary D.; Shen, Yang

1991-04-30

An improved inductively coupled gas plasma torch. The torch includes inner and outer quartz sleeves and tubular insert snugly fitted between the sleeves. The insert includes outwardly opening longitudinal channels. Gas flowing through the channels of the insert emerges in a laminar flow along the inside surface of the outer sleeve, in the zone of plasma heating. The laminar flow cools the outer sleeve and enables the torch to operate at lower electrical power and gas consumption levels additionally, the laminar flow reduces noise levels in spectroscopic measurements of the gaseous plasma.

Cutaneous heat flow during heating and cooling in Alligator mississipiensis.

PubMed

Smith, E N

1976-05-01

Direct in vivo measurement of heat flow across the skin of the American alligator (Alligator mississipiensis) showed increased heat flow during warming. Mean values at 25 degrees C during warming (15-35 degrees C) in air (airspeed 300 cm/s) were 17.9 +/- 92 SE cal/cm2 per h (mean alligator wt 3.27 kg). Cooling heat flow at the same temperature was 13.6 +/- 0.57 cal/cm2 per h. Subdermal heat flow was reduced during warming and was not significantly different from cutaneous heat flow during cooling. This indicated that the alligator was able to control its rate of heat exchange with the environment by altering cutaneous perfusion. Atropine, phenoxybenzamine, nitroglycerin, and Xylocaine did not affect cutaneous heat flow or heating and cooling rates. Atropine blocked bradycardia during cooling.

Rotary magnetic heat pump

DOEpatents

Kirol, Lance D.

1988-01-01

A rotary magnetic heat pump constructed without flow seals or segmented rotor accomplishes recuperation and regeneration by using split flow paths. Heat exchange fluid pumped through heat exchangers and returned to the heat pump splits into two flow components: one flowing counter to the rotor rotation and one flowing with the rotation.

Rotary magnetic heat pump

DOEpatents

Kirol, L.D.

1987-02-11

A rotary magnetic heat pump constructed without flow seals or segmented rotor accomplishes recuperation and regeneration by using split flow paths. Heat exchange fluid pumped through heat exchangers and returned to the heat pump splits into two flow components: one flowing counter to the rotor rotation and one flowing with the rotation. 5 figs.

Experimental study on flowing burning behaviors of a pool fire with dripping of melted thermoplastics.

PubMed

Xie, Qiyuan; Tu, Ran; Wang, Nan; Ma, Xin; Jiang, Xi

2014-02-28

The objective of this work is to quantitatively investigate the dripping-burning and flowing fire of thermoplastics. A new experimental setup is developed with a heating vessel and a T-trough. Hot thermoplastic liquids are generated in the vessel by electric heating. N2 gas is continuously injected into the vessel to avoid a sudden ignition of fuel in it. The detailed flowing burning behaviors of pool fire in the T-trough are analyzed through the measurements of the mass, heat flux and temperatures etc. The experimental results suggest that a continuous dripping of melted thermoplastic liquids in a nearly constant mass rate can be successfully made in the new setup. It also shows that the mass dripping rate of melted PS liquid is smaller than PP and PE since its large viscosity. In addition, the flame spread velocities of hot liquids of PS in the T-trough are also smaller than that of PP and PE because of its large viscosity. The mass burning rate of the PP and PE pool fire in T-trough are smaller than PS. Finally, considering the heating, melting, dripping and flowing burning behaviors of these polymers, it is suggested that the fire hazard of PE and PP are obviously higher than PS for their faster flowing burning. Copyright © 2013 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riggs, J.B.

An experimental test model, which is dynamically similar to an actual UCC (Underground Coal Conversion) system, has been used to determine fluid flow patterns and local heat transfer that occur in the UCC burn cavity. This study was designed to provide insight into the little understood mechanisms (i.e., heat transfer and oxygen transport to the cavity walls) which control maximum cavity width, and therefore resource recovery during UCC. The dynamically similar flow model has been designed by equating the Grashof and Reynolds number of the UCC system and the flow model, which employs water as its fluid. Equating the Grashofmore » number results in a scale factor of 0.13 while equating the Reynolds number yields a volumetric flow rate of water for the model of 30 gallons per minute. Qualitative studies were conducted with the flow model for both a void cavity and a cavity partially filled with simulated rubble. These studies provided insight into the combined effects of forced and free convection in a UCC cavity. In addition, dimensionless correlations were developed for the heat transfer to side walls for the case of a void cavity and these results can be used to predict oxygen transport to the side wall in a UCC cavity.« less

Final Scientific/Technical Report of Gas Hydrate Dynamics on the Alaskan Beaufort Continental Slope: Modeling and Field Characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hornbach, Matthew J; Colwell, Frederick S; Harris, Robert

Methane Hydrates, a solid form of methane and water, exist at high pressures and low temperatures, occurs on every continental margin on Earth, represents one of the largest reservoirs of carbon on the planet, and, if destabilized, may play an important role in both slope stability and climate change. For decades, researchers have studied methane hydrates with the hope of determining if methane hydrates are destabilizing, and if so, how this destabilization might impact slope stability and ocean/atmosphere carbon budgets. In the past ~5 years, it has become well established that the upper “feather-edge” of methane hydrate stability (intermediate watermore » depths of ~200-500 meters below sea level) represents an important frontier for methane hydrates stability research, as this zone is most susceptible to destabilization due to minor fluctuations in ocean temperature in space and time. The Arctic Ocean—one of the fastest warming regions on Earth—is perhaps the best place to study possible changes to methane hydrate stability due to ocean warming. To address the stability of methane hydrates at intermediate ocean depths, Southern Methodist University in partnership with Oregon State University and The United State Geological Survey at Woods Hole began investigating methane hydrate stability in intermediate water depths below both the US Beaufort Sea and the Atlantic Margin, from 2012-2017. The work was funded by the Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). The key goal of the SMU component of this study was to collect the first ever heat flow data in the Beaufort Sea and compare measured shallow (probe-based1) heat flow values with deeper (BSR-derived2) heat flow values, and from this, determine whether hydrates were in thermal equilibrium. In September 2016, SMU/OSU collected the first ever heat flow measurements in the US Beaufort Sea. Despite poor weather and rough seas, the cruise was a success, with 116 heat flow measurements acquired across the margin, spanning 4 transects separated by more than 400 km. Useable heat flow data exists for 97% (113) of probe heat flow measurements, revealing a clear picture of regional heat flow across the basin. During the past 8 months since the cruise, SMU researchers have processed the heat flow and thermal conductivity measurements and compared results to deeper heat flow estimates obtained from seismic data. The analysis reveals clear, consistent trends: All probe heat flow measurements in depths greater than 800 mbsl are consistent with BSR-derived values; heat flow measurements obtained in water depths between ~250-750 mbsl are systematically lower than those estimated from BSRs; and heat flow estimates in water depths shallower than ~250 mbsl are systematically warmer than deeper estimates. The consistency between shallow (probe) and deep (BSR) heat flow measurements at depths greater than ~750 m where ocean temperature changes are minimal supports the premise that the hydrates consist primarily of methane and represent a valuable tool for estimating heat flow. The anomalous cooling trend observed in the upper 250 m is consistent with expected seasonal effects observed in shallow ocean buoy measurements in the arctic, when cold, less dense melting sea ice cools the upper 200 m of the ocean during the summer as ice melting occurs. The discrepancy in heat flow at intermediate water depths is best explained via recent intermediate ocean temperature warming, where long-term (annual or longer) warming intermediate ocean bottom waters result in an anomalously low heat flow in shallow heat flow measurements. Using the characteristic 1D time-length scale for diffusion, we estimate that ocean temperature warming began no later than ~1200 years ago but arguably much more recently as results are limited by seismic resolution. More importantly, our analysis indicates methane hydrate is destabilizing not only in the upper feather edge (200-500 mbsl) but at depths as great as 750 mbsl. The intermediate ocean warming rate supports previous studies suggesting geologically rapid warming (>0.1 deg C/decade) at intermediate ocean depths in the Beaufort Sea. Assuming no further changes or additional warming, our analysis indicates methane hydrates will destabilize at seafloor depths shallower than 750 mbsl in the Beaufort Sea within the next ~3000 years. 1 Probe outfitted with sensors inserted into the seafloor sediment 2 Bottom-simulating reflector (BSR) seismic data indicates presence of hydrate deposits« less

High heat flux loop heat pipes

NASA Astrophysics Data System (ADS)

North, Mark T.; Sarraf, David B.; Rosenfeld, John H.; Maidanik, Yuri F.; Vershinin, Sergey

1997-01-01

Loop Heat Pipes (LHPs) can transport very large thermal power loads, over long distances, through flexible, small diameter tubes and against high gravitational heads. While recent LHPs have transported as much as 1500 W, the peak heat flux through a LHP's evaporator has been limited to about 0.07 MW/m2. This limitation is due to the arrangement of vapor passages next to the heat load which is one of the conditions necessary to ensure self priming of the device. This paper describes work aimed at raising this limit by threefold to tenfold. Two approaches were pursued. One optimized the vapor passage geometry for the high heat flux conditions. The geometry improved the heat flow into the wick and working fluid. This approach also employed a finer pored wick to support higher vapor flow losses. The second approach used a bidisperse wick material within the circumferential vapor passages. The bidisperse material increased the thermal conductivity and the evaporative surface area in the region of highest heat flux, while providing a flow path for the vapor. Proof-of-concept devices were fabricated and tested for each approach. Both devices operated as designed and both demonstrated operation at a heat flux of 0.70 MW/m2. This performance exceeded the known state of the art by a factor of more than six for both conventional heat pipes and for loop heat pipes using ammonia. In addition, the bidisperse-wick device demonstrated boiling heat transfer coefficients up to 100,000 W/m2.K, and the fine pored device demonstrated an orientation independence with its performance essentially unaffected by whether its evaporator was positioned above, below or level with the condenser.

Enzyme kinetics above denaturation temperature: a temperature-jump/stopped-flow apparatus.

PubMed

Kintses, Bálint; Simon, Zoltán; Gyimesi, Máté; Tóth, Júlia; Jelinek, Balázs; Niedetzky, Csaba; Kovács, Mihály; Málnási-Csizmadia, András

2006-12-15

We constructed a "temperature-jump/stopped-flow" apparatus that allows us to study fast enzyme reactions at extremely high temperatures. This apparatus is a redesigned stopped-flow which is capable of mixing the reactants on a submillisecond timescale concomitant with a temperature-jump even as large as 60 degrees C. We show that enzyme reactions that are faster than the denaturation process can be investigated above denaturation temperatures. In addition, the temperature-jump/stopped-flow enables us to investigate at physiological temperature the mechanisms of many human enzymes, which was impossible until now because of their heat instability. Furthermore, this technique is extremely useful in studying the progress of heat-induced protein unfolding. The temperature-jump/stopped-flow method combined with the application of structure-specific fluorescence signals provides novel opportunities to study the stability of certain regions of enzymes and identify the unfolding-initiating regions of proteins. The temperature-jump/stopped-flow technique may become a breakthrough in exploring new features of enzymes and the mechanism of unfolding processes.

Rapid and enhanced activation of microporous coordination polymers by flowing supercritical CO.sub.2

DOEpatents

Matzger, Adam J.; Liu, Baojian; Wong-Foy, Antek G.

2016-07-19

Flowing supercritical CO.sub.2 is used to activate metal organic framework materials (MOF). MOFs are activated directly from N,N-dimethylformamide (DMF) thus avoiding exchange with a volatile solvent. Most MCPs display increased surface areas directly after treatment although those with coordinatively unsaturated metal centers benefit from additional heating.

Heat transfer in a real engine environment

NASA Astrophysics Data System (ADS)

Gladden, Herbert J.

1985-10-01

The hot section facility at the Lewis Research Center was used to demonstrate the capability of instruments to make required measurements of boundary conditions of the flow field and heat transfer processes in the hostile environment of the turbine. The results of thermal scaling tests show that low temperature and pressure rig tests give optimistic estimates of the thermal performance of a cooling design for high pressure and temperature application. The results of measuring heat transfer coefficients on turbine vane airfoils through dynamic data analysis show good comparison with measurements from steady state heat flux gauges. In addition, the data trends are predicted by the STAN5 boundary layer code. However, the magnitude of the experimental data was not predicted by the analysis, particularly in laminar and transitional regions near the leading edge. The infrared photography system was shown capable of providing detailed surface thermal gradients and secondary flow features on a turbine vane and endwell.

Variations and controls on crustal thermal regimes in Southeastern Australia

NASA Astrophysics Data System (ADS)

Mather, Ben; McLaren, Sandra; Taylor, David; Roy, Sukanta; Moresi, Louis

2018-01-01

The surface heat flow field in Australia has for many years been poorly constrained compared to continental regions elsewhere. 182 recent heat flow determinations and 66 new heat production measurements for Southeastern Australia significantly increase our understanding of local and regional lithospheric thermal regimes and allow for detailed thermal modelling. The new data give a mean surface heat flow for Victoria of 71 ± 15 mW m- 2 which fits within the 61-77 mW m- 2 range reported for Phanerozoic-aged crust globally. These data reveal three new thermally and compositionally distinct heat flow sub-provinces within the previously defined Eastern Heat Flow Province: the Delamerian heat flow sub-province (average surface heat flow 60 ± 9 mW m- 2); the Lachlan heat flow sub-province (average surface heat flow 74 ± 13 mW m- 2); and the Newer Volcanics heat flow sub-province (average surface heat flow 72 ± 16 mW m- 2) which includes extreme values that locally exceed 100 mW m- 2. Inversions of reduced heat flow and crustal differentiation find that the Delamerian sub-province has experienced significant crustal reworking compared to the Lachlan and Newer Volcanics sub-provinces. The latter has experienced volcanism within the last 8 Ma and the degree of variability observed in surface heat flow points (up to 8 mW m- 2 per kilometre laterally) cannot be replicated with steady-state thermal models through this sub-province. In the absence of a strong palaeoclimate signal, aquifer disturbances, or highly enriched granites, we suggest that this high variability arises from localised transient perturbations to the upper crust associated with recent intraplate volcanism. This is supported by a strong spatial correlation of high surface heat flow and known eruption points within the Newer Volcanics heat flow sub-province.

A study of boiling heat transfer as applied to the cooling of ball bearings in the high pressure oxygen turbopump of the space shuttle main engine

NASA Technical Reports Server (NTRS)

Schreiber, Will

1986-01-01

Two sets of ball bearings support the main shaft within the High Pressure Oxygen Turbopump (HPOTP) in the Space Shuttle Main Engine (SSME). In operation, these bearings are cooled and lubricated with high pressure liquid oxygen (LOX) flowing axially through the bearing assembly. Currently, modifications in the assembly design are being contemplated in order to enhance the lifetime of the bearings and to allow the HPOTP to operate under larger loads. An understanding of the fluid dynamics and heat transfer characteristics of the flowing LOX is necessary for the implementation of these design changes. The proposed computational model of the LOX fluid dynamics, in addition to dealing with a turbulent flow in a complex geometry, must address the complication associated with boiling and two-phase flow. The feasibility of and possible methods for modeling boiling heat transfer are considered. The theory of boiling as pertains to this particular problem is reviewed. Recommendations are given for experiments which would be necessary to establish validity for correlations needed to model boiling.

Separation and quantification of monoclonal-antibody aggregates by hollow-fiber-flow field-flow fractionation.

PubMed

Fukuda, Jun; Iwura, Takafumi; Yanagihara, Shigehiro; Kano, Kenji

2014-10-01

Hollow-fiber-flow field-flow fractionation (HF5) separates protein molecules on the basis of the difference in the diffusion coefficient, and can evaluate the aggregation ratio of proteins. However, HF5 is still a minor technique because information on the separation conditions is limited. We examined in detail the effect of different settings, including the main-flow rate, the cross-flow rate, the focus point, the injection amount, and the ionic strength of the mobile phase, on fractographic characteristics. On the basis of the results, we proposed optimized conditions of the HF5 method for quantification of monoclonal antibody in sample solutions. The HF5 method was qualified regarding the precision, accuracy, linearity of the main peak, and quantitation limit. In addition, the HF5 method was applied to non-heated Mab A and heat-induced-antibody-aggregate-containing samples to evaluate the aggregation ratio and the distribution extent. The separation performance was comparable with or better than that of conventional methods including analytical ultracentrifugation-sedimentation velocity and asymmetric-flow field-flow fractionation.

Heat Transfer from a Horizontal Cylinder Rotating in Oil

NASA Technical Reports Server (NTRS)

Seban, R. A.; Johnson, H. A.

1959-01-01

Measurements of the heat transfer from a horizontal cylinder rotating about its axis have been made with oil as the surrounding fluid to provide an addition to the heat-transfer results for this system heretofore available only for air. The results embrace a Prandtl number range from about 130 to 660, with Reynolds numbers up to 3 x 10(exp 4), and show an increasing dependence of free-convection heat transfer on rotation as the Prandtl number is increased by reducing the oil temperature. Some correlation of this effect, which agrees with the prior results for air, has been achieved. At higher rotative speeds the flow becomes turbulent, the free- convection effect vanishes, and the results with oil can be correlated generally with those for air and with mass-transfer results for even higher Prandtl numbers. For this system, however, the analogy calculations which have successfully related the heat transfer to the friction for pipe flows at high Prandtl numbers fail.

Refrigerant charge management in a heat pump water heater

DOEpatents

Chen, Jie; Hampton, Justin W.

2014-06-24

Heat pumps that heat or cool a space and that also heat water, refrigerant management systems for such heat pumps, methods of managing refrigerant charge, and methods for heating and cooling a space and heating water. Various embodiments deliver refrigerant gas to a heat exchanger that is not needed for transferring heat, drive liquid refrigerant out of that heat exchanger, isolate that heat exchanger against additional refrigerant flowing into it, and operate the heat pump while the heat exchanger is isolated. The heat exchanger can be isolated by closing an electronic expansion valve, actuating a refrigerant management valve, or both. Refrigerant charge can be controlled or adjusted by controlling how much liquid refrigerant is driven from the heat exchanger, by letting refrigerant back into the heat exchanger, or both. Heat pumps can be operated in different modes of operation, and segments of refrigerant conduit can be interconnected with various components.

User's guide of TOUGH2-EGS-MP: A Massively Parallel Simulator with Coupled Geomechanics for Fluid and Heat Flow in Enhanced Geothermal Systems VERSION 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiong, Yi; Fakcharoenphol, Perapon; Wang, Shihao

2013-12-01

TOUGH2-EGS-MP is a parallel numerical simulation program coupling geomechanics with fluid and heat flow in fractured and porous media, and is applicable for simulation of enhanced geothermal systems (EGS). TOUGH2-EGS-MP is based on the TOUGH2-MP code, the massively parallel version of TOUGH2. In TOUGH2-EGS-MP, the fully-coupled flow-geomechanics model is developed from linear elastic theory for thermo-poro-elastic systems and is formulated in terms of mean normal stress as well as pore pressure and temperature. Reservoir rock properties such as porosity and permeability depend on rock deformation, and the relationships between these two, obtained from poro-elasticity theories and empirical correlations, are incorporatedmore » into the simulation. This report provides the user with detailed information on the TOUGH2-EGS-MP mathematical model and instructions for using it for Thermal-Hydrological-Mechanical (THM) simulations. The mathematical model includes the fluid and heat flow equations, geomechanical equation, and discretization of those equations. In addition, the parallel aspects of the code, such as domain partitioning and communication between processors, are also included. Although TOUGH2-EGS-MP has the capability for simulating fluid and heat flows coupled with geomechanical effects, it is up to the user to select the specific coupling process, such as THM or only TH, in a simulation. There are several example problems illustrating applications of this program. These example problems are described in detail and their input data are presented. Their results demonstrate that this program can be used for field-scale geothermal reservoir simulation in porous and fractured media with fluid and heat flow coupled with geomechanical effects.« less

Reflux cooling experiments on the NCSU scaled PWR facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doster, J.M.; Giavedoni, E.

1993-01-01

Under loss of forced circulation, coupled with the loss or reduction in primary side coolant inventory, horizontal stratified flows can develop in the hot and cold legs of pressurized water reactors (PWRs). Vapor produced in the reactor vessel is transported through the hot leg to the steam generator tubes where it condenses and flows back to the reactor vessel. Within the steam generator tubes, the flow regimes may range from countercurrent annular flow to single-phase convection. As a result, a number of heat transfer mechanisms are possible, depending on the loop configuration, total heat transfer rate, and the steam flowmore » rate within the tubes. These include (but are not limited to) two-phase natural circulation, where the condensate flows concurrent to the vapor stream and is transported to the cold leg so that the entire reactor coolant loop is active, and reflux cooling, where the condensate flows back down the interior of the coolant tubes countercurrent to the vapor stream and is returned to the reactor vessel through the hot leg. While operating in the reflux cooling mode, the cold leg can effectively be inactive. Heat transfer can be further influenced by noncondensables in the vapor stream, which accumulate within the upper regions of the steam generator tube bundle. In addition to reducing the steam generator's effective heat transfer area, under these conditions operation under natural circulation may not be possible, and reflux cooling may be the only viable heat transfer mechanism. The scaled PWR (SPWR) facility in the nuclear engineering department at North Carolina State Univ. (NCSU) is being used to study the effectiveness of two-phase natural circulation and reflux cooling under conditions associated with loss of forced circulation, midloop coolant levels, and noncondensables in the primary coolant system.« less

Heating Augmentation in Laminar Flow Due to Heat-Shield Cavities on the Project Orion CEV

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

2008-01-01

An experimental study has been conducted to assess the effects of compression pad cavities on the aeroheating environment of the Project Orion CEV heat-shield at laminar conditions. Testing was conducted in Mach 6 and Mach 10 perfect-gas wind tunnels to obtain heating measurements on and around the compression pads using global phosphor thermography. Consistent trends in heating augmentation levels were observed in the data and correlations of average and maximum heating at the cavities were formulated in terms of the local boundary-layer parameters and cavity dimensions. Additional heating data from prior testing of Genesis and Mars Science Laboratory models were also examined to extend the parametric range of cavity heating correlations.

Lava-substrate heat transfer: Laboratory experiments and thermodynamic modeling

NASA Astrophysics Data System (ADS)

Rumpf, M.; Fagents, S. A.; Hamilton, C. W.; Wright, R.; Crawford, I.

2012-12-01

We have performed laboratory experiments and numerical modeling to investigate the heat transfer from a lava flow into various substrate materials, focusing on the effects of the differing thermophysical properties of substrate materials. Initial motivation for this project developed from the desire to understand the loss of solar wind volatiles embedded in lunar regolith deposits that were subsequently covered by a lava flow. The Moon lacks a significant atmosphere and magnetosphere, leaving the surface regolith exposed to bombardment by solar flare and solar wind particles, and by the cosmogenic products of galactic cosmic rays. Preservation of particle-rich regolith deposits may have occurred by the emplacement of an active lava flow on top of the regolith layer, provided the embedded particles survive heating by the lava. During future expeditions to the lunar surface, ancient regolith deposits could be sampled through surface drilling to extract the extra-lunar particles, revealing a history of the solar activity and galactic events not available on the Earth. This project also has important implications for terrestrial lava flows, particularly in the prediction of lava flow hazards. Lava erupted on Earth may be emplaced on various substrates, including solid lava rock, volcanic tephra, sands, soils, etc. The composition, grain size, consolidation, moisture content, etc. of these materials will vary greatly and have different effects on the cooling of the flow. Accounting for specific properties of the substrate could be an important improvement in lava flow models We have performed laboratory experiments in collaboration with the Department of Art and Art History at the University of Hawaii at Manoa in which ~5-6 kg of basalt, collected at Kilauea Volcano, Hawaii, is melted to ~1200 °C. The lava is poured into a device constructed of calcium silicate sheeting that has been filled with a solid or particulate substrate material and embedded with thermocouples. Internal temperatures are monitored by the thermocouple array, while external temperatures are monitored by a Forward Looking Infrared Radiometer (FLIR) video camera. The experimental data thus describe the cooling rates of the system, and reveal the release of latent heat of crystallization within the cooling lava. These experiments have been conducted in conjunction with numerical simulations of the heat transfer from a lava flow into various substrates, to quantify the depth reached by the heat pulse as it penetrates the substrate. Models include material-specific, temperature-dependent thermophysical properties, including thermal conductivity, specific heat capacity, and latent heat of crystallization. We find that particulate materials, such as lunar regolith, sand, and soils will be heated to depths shallower than solid materials. In addition, the particulate materials will act as insulators, shielding the lava flow from basal cooling and maintaining high temperatures in the flow core. These results suggest that lava flows emplaced on a dry particulate terrain will remain above solidus for a longer duration, allowing the lava to flow further than when emplaced on a solid substrate.

Investigation of transition from thermal- to solutal-Marangoni flow in dilute alcohol/water mixtures using nano-plasmonic heaters

NASA Astrophysics Data System (ADS)

Namura, Kyoko; Nakajima, Kaoru; Suzuki, Motofumi

2018-02-01

We experimentally investigated Marangoni flows around a microbubble in diluted 1-butanol/water, 2-propanol/water, and ethanol/water mixtures using the thermoplasmonic effect of gold nanoisland film. A laser spot on the gold nanoisland film acted as a highly localized heat source that was utilized to generate stable air microbubbles with diameters of 32-48 μm in the fluid and to induce a steep temperature gradient on the bubble surface. The locally heated bubble has a flow along the bubble surface, with the flow direction showing a clear transition depending on the alcohol concentrations. The fluid is driven from the hot to cold regions when the alcohol concentration is lower than the transition concentration, whereas it is driven from the cold to hot regions when the concentration is higher than the transition concentration. In addition, the transition concentration increases as the carbon number of the alcohol decreases. The observed flow direction transition is explained by the balance of the thermal- and solutal-Marangoni forces that are cancelled out for the transition concentration. The selective evaporation of the alcohol at the locally heated surface allows us to generate stable and rapid thermoplasmonic solutal-Marangoni flows in the alcohol/water mixtures.

User's Guide of TOUGH2-EGS. A Coupled Geomechanical and Reactive Geochemical Simulator for Fluid and Heat Flow in Enhanced Geothermal Systems Version 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fakcharoenphol, Perapon; Xiong, Yi; Hu, Litang

TOUGH2-EGS is a numerical simulation program coupling geomechanics and chemical reactions for fluid and heat flows in porous media and fractured reservoirs of enhanced geothermal systems. The simulator includes the fully-coupled geomechanical (THM) module, the fully-coupled geochemical (THC) module, and the sequentially coupled reactive geochemistry (THMC) module. The fully-coupled flow-geomechanics model is developed from the linear elastic theory for the thermo-poro-elastic system and is formulated with the mean normal stress as well as pore pressure and temperature. The chemical reaction is sequentially coupled after solution of flow equations, which provides the flow velocity and phase saturation for the solute transportmore » calculation at each time step. In addition, reservoir rock properties, such as porosity and permeability, are subjected to change due to rock deformation and chemical reactions. The relationships between rock properties and geomechanical and chemical effects from poro-elasticity theories and empirical correlations are incorporated into the simulator. This report provides the user with detailed information on both mathematical models and instructions for using TOUGH2-EGS for THM, THC or THMC simulations. The mathematical models include the fluid and heat flow equations, geomechanical equation, reactive geochemistry equations, and discretization methods. Although TOUGH2-EGS has the capability for simulating fluid and heat flows coupled with both geomechanical and chemical effects, it is up to the users to select the specific coupling process, such as THM, THC, or THMC in a simulation. There are several example problems illustrating the applications of this program. These example problems are described in details and their input data are presented. The results demonstrate that this program can be used for field-scale geothermal reservoir simulation with fluid and heat flow, geomechanical effect, and chemical reaction in porous and fractured media.« less

Axial flow heat exchanger devices and methods for heat transfer using axial flow devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koplow, Jeffrey P.

Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferredmore » across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.« less

Heat stress redistributes blood flow in arteries of the brain during dynamic exercise.

PubMed

Sato, Kohei; Oue, Anna; Yoneya, Marina; Sadamoto, Tomoko; Ogoh, Shigehiko

2016-04-01

We hypothesized that heat stress would decrease anterior and posterior cerebral blood flow (CBF) during exercise, and the reduction in anterior CBF would be partly associated with large increase in extracranial blood flow (BF). Nine subjects performed 40 min of semirecumbent cycling at 60% of the peak oxygen uptake in hot (35°C; Heat) and thermoneutral environments (25°C; Control). We evaluated BF and conductance (COND) in the external carotid artery (ECA), internal carotid artery (ICA), and vertebral artery (VA) using ultrasonography. During the Heat condition, ICA and VA BF were significantly increased 10 min after the start of exercise (P < 0.05) and thereafter gradually decreased. ICA COND was significantly decreased (P < 0.05), whereas VA COND remained unchanged throughout Heat. Compared with the Control, either BF or COND of ICA and VA at the end of Heat tended to be lower, but not significantly. In contrast, ECA BF and COND at the end of Heat were both higher than levels in the Control condition (P < 0.01). During Heat, a reduction in ICA BF appears to be associated with a decline in end-tidal CO2 tension (r = 0.84), whereas VA BF appears to be affected by a change in cardiac output (r = 0.87). In addition, a change in ECA BF during Heat was negatively correlated with a change in ICA BF (r = -0.75). Heat stress resulted in modification of the vascular response of head and brain arteries to exercise, which resulted in an alteration in the distribution of cardiac output. Moreover, a hyperthermia-induced increase in extracranial BF might compromise anterior CBF during exercise with heat stress. Copyright © 2016 the American Physiological Society.

Institute for High Heat Flux Removal (IHHFR). Phases I, II, and III

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, Ronald D.

2014-08-31

The IHHFR focused on interdisciplinary applications as it relates to high heat flux engineering issues and problems which arise due to engineering systems being miniaturized, optimized, or requiring increased high heat flux performance. The work in the IHHFR focused on water as a coolant and includes: (1) the development, design, and construction of the high heat flux flow loop and facility; (2) test section development, design, and fabrication; and, (3) single-side heat flux experiments to produce 2-D boiling curves and 3-D conjugate heat transfer measurements for single-side heated test sections. This work provides data for comparisons with previously developed andmore » new single-side heated correlations and approaches that address the single-side heated effect on heat transfer. In addition, this work includes the addition of single-side heated circular TS and a monoblock test section with a helical wire insert. Finally, the present work includes: (1) data base expansion for the monoblock with a helical wire insert (only for the latter geometry), (2) prediction and verification using finite element, (3) monoblock model and methodology development analyses, and (4) an alternate model development for a hypervapotron and related conjugate heat transfer controlling parameters.« less

Open-loop heat-recovery dryer

DOEpatents

TeGrotenhuis, Ward Evan

2013-11-05

A drying apparatus is disclosed that includes a drum and an open-loop airflow pathway originating at an ambient air inlet, passing through the drum, and terminating at an exhaust outlet. A passive heat exchanger is included for passively transferring heat from air flowing from the drum toward the exhaust outlet to air flowing from the ambient air inlet toward the drum. A heat pump is also included for actively transferring heat from air flowing from the passive heat exchanger toward the exhaust outlet to air flowing from the passive heat exchanger toward the drum. A heating element is also included for further heating air flowing from the heat pump toward the drum.

Transitions to improved confinement regimes induced by changes in heating in zero-dimensional models for tokamak plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, H.; Chapman, S. C.; Max Planck Institute for the Physics of Complex Systems, Dresden

2014-06-15

It is shown that rapid substantial changes in heating rate can induce transitions to improved energy confinement regimes in zero-dimensional models for tokamak plasma phenomenology. We examine for the first time the effect of step changes in heating rate in the models of Kim and Diamond [Phys. Rev. Lett. 90, 185006 (2003)] and Malkov and Diamond [Phys. Plasmas 16, 012504 (2009)], which nonlinearly couple the evolving temperature gradient, micro-turbulence, and a mesoscale flow; and in the extension of Zhu et al. [Phys. Plasmas 20, 042302 (2013)], which couples to a second mesoscale flow component. The temperature gradient rises, as doesmore » the confinement time defined by analogy with the fusion context, while micro-turbulence is suppressed. This outcome is robust against variation of heating rise time and against introduction of an additional variable into the model. It is also demonstrated that oscillating changes in heating rate can drive the level of micro-turbulence through a period-doubling path to chaos, where the amplitude of the oscillatory component of the heating rate is the control parameter.« less

Determination of shelf heat transfer coefficients along the shelf flow path of a freeze dryer using the shelf fluid temperature perturbation approach.

PubMed

Kuu, Wei Y; Nail, Steven L; Hardwick, Lisa M

2007-01-01

The spatial distribution of local shelf heat transfer coefficients, Ks, was determined by mapping the transient temperature response of the shelf surface along the serpentine internal channels of the shelf while the temperature of the heat transfer fluid was ramped from -40 degrees to 40 degrees C. The solution of a first-order non-steady-state differential equation resulted in a predicted shelf surface temperature as a function of the shelf fluid temperature at any point along the flow path. During the study, the shelf surfaces were maintained under a thermally insulated condition so that the heat transfers by gas conduction and radiation were negligible. To minimize heat conduction by gas, the chamber was evacuated to a low pressure, such as 100 mTorr. To minimize heat transfers between shelves, shelves were moved close together, with a gap of approximately 3 mm between any two shelves, because the shelf surface temperatures at corresponding vertical locations of two shelves are virtually equal. In addition, this also provides a shielding from radiation heat transfer from shelf to walls. Local heat transfer coefficients at the probed locations h(x) ( approximately Ks) were calculated by fitting the experimental shelf temperature response to the theoretical value. While the resulting values of K(s) are in general agreement with previously reported values, the values of Ks close to the inlet are significantly higher than those of other locations of the shelf channel. This observation is most likely attributed to the variation of the flow pattern of heat transfer fluid within the channels.

A Report from the Thermal Science Research Center (TSRC)

NASA Technical Reports Server (NTRS)

Boyd, Ronald D.

1998-01-01

A vertical flow loop was designed and assembled to determine the local (circumferential and axial) and mean wall temperature distributions for single-phase and two-phase (subcooled and saturated) downward flow in both uniformly-heated and single-side heated vertical channels. Freon-11 was used as the working fluid in order to directly relate and compare the results with a previous experimental campaign which employed this same working fluid. For a given steady-state experiment, the following parameters were held constant: (1) exit pressure, (2) inlet temperature, and (3) mass velocity. For a given configuration of the 2.2 m long cylindrical channel test section, which had a 1.2 m long heated section, the applied heat rate was varied from zero through successive quasi-steady states to a level which corresponded to localized film boiling in the test section. The measurements showed that the boiling curve changes significantly at higher mass velocities with respect to both the circumferential and axial directions. The slope of the boiling curve changes in a non-monotonic fashion with respect to the circumferential directions. The slope of the boiling curve changes in a non-monotonic fashion with respect to the circumferential direction. The measurements point to the existence of a dry-out phenomenon occurring at multiple levels of the applied heat for the single-side heated channel. In comparing the heat transfer for horizontal channel flow with a vertically downward flow, the results show that significantly lower heat transfer occurs in the horizontal flow. However, this trend reverses as both the Reynolds number and the applied heat rate increase. Both the Liu-Winterton and Shah correlations were compared with the experimental data. The Shah correlation predicted the uniformly heated tube data better. When a thermal hydraulic diameter approach was used for the single-side heated case, the data at upstream locations for Z/L less than 0.5 was bounded above by the Liu-Winterton correlation and below by the Shah correlation. At Z/L = 0.5, the Shah correlation bounded the data; and for Z/L greater than 0.5, both correlations overpredicted the data with the Shah correlation being closest to the data. The present results indicate that additional correlational development is needed. In addressing some of the advanced space thermal management objectives concerning accommodating high heat fluxes in non-uniformly heated systems, a large battery of experiments 88 have been completed where local two-dimensional wall temperature variations were measured for both single-phase and two-phase flow in a single-side heated circular tube. As noted above, the results show significant axial and circumferential variations. Accurately accounting for such variations can result in optimized future advanced space, enhanced (high heat flux) thermal management systems.

Natural convection of Al2O3-water nanofluid in a wavy enclosure

NASA Astrophysics Data System (ADS)

Leonard, Mitchell; Mozumder, Aloke K.; Mahmud, Shohel; Das, Prodip K.

2017-06-01

Natural convection heat transfer and fluid flow inside enclosures filled with fluids, such as air, water or oil, have been extensively analysed for thermal enhancement and optimisation due to their applications in many engineering problems, including solar collectors, electronic cooling, lubrication technologies, food processing and nuclear reactors. In comparison, little effort has been given to the problem of natural convection inside enclosures filled with nanofluids, while the addition of nanoparticles into a fluid base to alter thermal properties can be a feasible solution for many heat transfer problems. In this study, the problem of natural convection heat transfer and fluid flow inside a wavy enclosure filled with Al2O3-water nanofluid is investigated numerically using ANSYS-FLUENT. The effects of surface waviness and aspect ratio of the wavy enclosure on the heat transfer and fluid flow are analysed for various concentrations of Al2O3 nanoparticles in water. Flow fields and temperature fields are investigated and heat transfer rate is examined for different values of Rayleigh number. Results show that heat transfer within the enclosure can be enhanced by increasing surface waviness, aspect ratio or nanoparticles volume fraction. Changes in surface waviness have little effect on the heat transfer rate at low Rayleigh numbers, but when Ra ≥ 105 heat transfer increases with the increase of surface waviness from zero to higher values. Increasing the aspect ratio causes an increase in heat transfer rate, as the Rayleigh number increases the effect of changing aspect ratio is more apparent with the greatest heat transfer enhancement seen at higher Rayleigh numbers. Nanoparticles volume fraction has a little effect on the average Nusselt number at lower Rayleigh numbers when Ra ≥ 105 average Nusselt number increases with the increase of volume fraction. These findings provide insight into the heat transfer effects of using Al2O3-water nanofluid as a heat transfer medium and the effects of changing geometrical parameters, which will help in developing novel geometries with enhanced and controlled heat-transfer for solar collectors, electronic cooling, and food processing industries.

Effect of the load size on the efficiency of microwave heating under stop flow and continuous flow conditions.

PubMed

Patil, Narendra G; Rebrov, Evgeny V; Eränen, Kari; Benaskar, Faysal; Meuldijk, Jan; Mikkola, Jyri-Pekka; Hessel, Volker; Hulshof, Lumbertus A; Murzin, Dmitry Yu; Schouten, Jaap C

2012-01-01

A novel heating efficiency analysis of the microwave heated stop-flow (i.e. stagnant liquid) and continuous-flow reactors has been presented. The thermal losses to the surrounding air by natural convection have been taken into account for heating efficiency calculation of the microwave heating process. The effect of the load diameter in the range of 4-29 mm on the heating efficiency of ethylene glycol was studied in a single mode microwave cavity under continuous flow and stop-flow conditions. The variation of the microwave absorbing properties of the load with temperature was estimated. Under stop-flow conditions, the heating efficiency depends on the load diameter. The highest heating efficiency has been observed at the load diameter close to the half wavelength of the electromagnetic field in the corresponding medium. Under continuous-flow conditions, the heating efficiency increased linearly. However, microwave leakage above the propagation diameter restricted further experimentation at higher load diameters. Contrary to the stop-flow conditions, the load temperature did not raise monotonously from the inlet to outlet under continuous-flow conditions. This was due to the combined effect of lagging convective heat fluxes in comparison to volumetric heating. This severely disturbs the uniformity of the electromagnetic field in the axial direction and creates areas of high and low field intensity along the load Length decreasing the heating efficiency as compared to stop-flow conditions.

Submarine hydrogeology of the Hawaiian archipelagic apron: 2. Numerical simulations of coupled heat transport and fluid flow

NASA Astrophysics Data System (ADS)

Harris, Robert N.; Garven, Grant; Georgen, Jennifer; McNutt, Marcia K.; Christiansen, Lizet; von Herzen, Richard P.

2000-09-01

We perform numerical simulations of buoyancy-driven, pore fluid flow in the Hawaiian archipelagic apron and underlying oceanic crust in order to determine the extent to which heat redistributed by such flow might cause conductive heat flow measurements to underrepresent the true mantle heat flux. We also seek an understanding of undulations observed in finely spaced heat flow measurements acquired north of Oahu and Maro Reef with wavelengths of 10 to 100 km and amplitudes of 2 to 7 mW m-2. We find that pore fluid flow can impart significant perturbations to seafloor heat flow from the value expected assuming a constant mantle flux. In the simplest scenario, moat-wide circulation driven by bathymetric relief associated with the volcanic edifice recharges a fluid system over the moat and discharges the geothermally heated water through the volcanic edifice. The existing heat flow data are unable to confirm the existence of such a flow regime, in that it produces prominent heat flow anomalies only on the steep flanks of the volcano where heat flow probes cannot penetrate. However, this flow system does not significantly mask the mantle flux for reasonable permeabilities and flow rates. Another numerical simulation in which the upper oceanic basement acts as a aquifer for a flow loop recharged at basement outcrops on the flexural arch and discharged within a permeable volcanic edifice is capable of almost uniformly depressing conductive heat flow across the entire moat by ˜15%. Large heat flow anomalies (>20 mW m-2) are located over the recharge and discharge zones but are beyond the area sampled by our data. Presumably finely spaced heat flow measurements over the flexural arch could test for the existence of the predicted recharge zone. We demonstrate that the prominent, shorter-wave undulations in heat flow across the Oahu and Maro Reef moats are too large to be explained solely by relief in the upper oceanic basement. More likely, shallower large-scale turbidites or debris flows also serve as aquifers within the less permeable moat sediments. With our limited information on the structural geology of the moat, permeability structure of its major geologic units, and their variations in the third dimension, we are not able to exactly match the spatial distribution of heat flow anomalies in our data, but spectral comparisons look promising.

An Experimental and Numerical Investigation of Endwall Aerodynamics and Heat Transfer in a Gas Turbine Nozzle Guide Vane with Slot Film Cooling

NASA Astrophysics Data System (ADS)

Alqefl, Mahmood Hasan

In many regions of the high-pressure gas turbine, film cooling flows are used to protect the turbine components from the combustor exit hot gases. Endwalls are challenging to cool because of the complex system of secondary flows that disturb surface film coolant coverage. The secondary flow vortices wash the film coolant from the surface into the mainstream significantly decreasing cooling effectiveness. In addition to being effected by secondary flow structures, film cooling flow can also affect these structures by virtue of their momentum exchange. In addition, many studies in the literature have shown that endwall contouring affects the strength of passage secondary flows. Therefore, to develop better endwall cooling schemes, a good understanding of passage aerodynamics and heat transfer as affected by interactions of film cooling flows with secondary flows is required. This experimental and computational study presents results from a linear, stationary, two-passage cascade representing the first stage nozzle guide vane of a high-pressure gas turbine with an axisymmetrically contoured endwall. The sources of film cooling flows are upstream combustor liner coolant and endwall slot film coolant injected immediately upstream of the cascade passage inlet. The operating conditions simulate combustor exit flow features, with a high Reynolds number of 390,000 and approach flow turbulence intensity of 11% with an integral length scale of 21% of the chord length. Measurements are performed with varying slot film cooling mass flow to mainstream flow rate ratios (MFR). Aerodynamic effects are documented with five-hole probe measurements at the exit plane. Heat transfer is documented through recovery temperature measurements with a thermocouple. General secondary flow features are observed. Total pressure loss measurements show that varying the slot film cooling MFR has some effects on passage loss. Velocity vectors and vorticity distributions show a very thin, yet intense, cross-pitch flow on the contoured endwall side. Endwall adiabatic effectiveness values and coolant distribution thermal fields show minimal effects of varying slot film coolant MFR. This suggests the dominant effects of combustor liner coolant. show dominant effects of combustor liner coolant on cooling the endwall. A coolant vorticity correlation presenting the advective mixing of the coolant due to secondary flow vorticity at the exit plane is also discussed.

Computational study of the heat transfer of an avian egg in a tray.

PubMed

Eren Ozcan, S; Andriessens, S; Berckmans, D

2010-04-01

The development of an embryo in an avian egg depends largely on its temperature. The embryo temperature is affected by its environment and the heat produced by the egg. In this paper, eggshell temperature and the heat transfer characteristics from one egg in a tray toward its environment are studied by means of computational fluid dynamics (CFD). Computational fluid dynamics simulations have the advantage of providing extensive 3-dimensional information on velocity and eggshell temperature distribution around an egg that otherwise is not possible to obtain by experiments. However, CFD results need to be validated against experimental data. The objectives were (1) to find out whether CFD can successfully simulate eggshell temperature from one egg in a tray by comparing to previously conducted experiments, (2) to visualize air flow and air temperature distribution around the egg in a detailed way, and (3) to perform sensitivity analysis on several variables affecting heat transfer. To this end, a CFD model was validated using 2 sets of temperature measurements yielding an effective model. From these simulations, it can be concluded that CFD can effectively be used to analyze heat transfer characteristics and eggshell temperature distribution around an egg. In addition, air flow and temperature distribution around the egg are visualized. It has been observed that temperature differences up to 2.6 degrees C are possible at high heat production (285 mW) and horizontal low flow rates (0.5 m/s). Sensitivity analysis indicates that average eggshell temperature is mainly affected by the inlet air velocity and temperature, flow direction, and the metabolic heat of the embryo and less by the thermal conductivity and emissivity of the egg and thermal emissivity of the tray.

A Prototype Flux-Plate Heat-Flow Sensor for Venus Surface Heat-Flow Determinations

NASA Technical Reports Server (NTRS)

Morgan, Paul; Reyes, Celso; Smrekar, Suzanne E.

2005-01-01

Venus is the most Earth-like planet in the Solar System in terms of size, and the densities of the two planets are almost identical when selfcompression of the two planets is taken into account. Venus is the closest planet to Earth, and the simplest interpretation of their similar densities is that their bulk compositions are almost identical. Models of the thermal evolution of Venus predict interior temperatures very similar to those indicated for the regions of Earth subject to solid-state convection, but even global analyses of the coarse Pioneer Venus elevation data suggest Venus does not lose heat by the same primary heat loss mechanism as Earth, i.e., seafloor spreading. The comparative paucity of impact craters on Venus has been interpreted as evidence for relatively recent resurfacing of the planet associated with widespread volcanic and tectonic activity. The difference in the gross tectonic styles of Venus and Earth, and the origins of some of the enigmatic volcano-tectonic features on Venus, such as the coronae, appear to be intrinsically related to Venus heat loss mechanism(s). An important parameter in understanding Venus geological evolution, therefore, is its present surface heat flow. Before the complications of survival in the hostile Venus surface environment were tackled, a prototype fluxplate heat-flow sensor was built and tested for use under synthetic stable terrestrial surface conditions. The design parameters for this prototype were that it should operate on a conforming (sand) surface, with a small, self-contained power and recording system, capable of operating without servicing for at least several days. The precision and accuracy of the system should be < 5 mW/sq m. Additional information is included in the original extended abstract.

Upgraded flowing liquid lithium limiter for improving Li coverage uniformity and erosion resistance in EAST device

NASA Astrophysics Data System (ADS)

Zuo, G. Z.; Hu, J. S.; Maingi, R.; Yang, Q. X.; Sun, Z.; Huang, M.; Chen, Y.; Yuan, X. L.; Meng, X. C.; Xu, W.; Gentile, C.; Carpe, A.; Diallo, A.; Lunsford, R.; Mansfield, D.; Osborne, T.; Tritz, K.; Li, J. G.

2017-12-01

We report on design and technology improvements for a flowing liquid lithium (FLiLi) limiter inserted into auxiliary heated discharges in the experimental advanced superconducting tokamak device. In order to enhance Li coverage uniformity and erosion resistance, a new liquid Li distributor with homogenous channels was implemented. In addition, two independent electromagnetic pumps and a new horizontal capillary structure contributed to an improvement in the observed Li flow uniformity (from 30% in the previous FLiLi design to >80% in this FLiLi design). To improve limiter surface erosion resistance, hot isostatic press technology was applied, which improved the thermal contact between thin stainless steel protective layers covering the Cu heat sink. The thickness of the stainless steel layer was increased from 0.1 mm to 0.5 mm, which also helped macroscopic erosion resilience. Despite the high auxiliary heating power up to 4.5 MW, no Li bursts were recorded from FLiLi, underscoring the improved performance of this new design.

Heat transfer in gas turbine engines and three-dimensional flows; Proceedings of the Symposium, ASME Winter Annual Meeting, Chicago, IL, Nov. 27-Dec. 2, 1988

NASA Technical Reports Server (NTRS)

Elovic, E. (Editor); O'Brien, J. E. (Editor); Pepper, D. W. (Editor)

1988-01-01

The present conference on heat transfer characteristics of gas turbines and three-dimensional flows discusses velocity-temperature fluctuation correlations at the flow stagnation flow of a circular cylinder in turbulent flow, heat transfer across turbulent boundary layers with pressure gradients, the effect of jet grid turbulence on boundary layer heat transfer, and heat transfer characteristics predictions for discrete-hole film cooling. Also discussed are local heat transfer in internally cooled turbine airfoil leading edges, secondary flows in vane cascades and curved ducts, three-dimensional numerical modeling in gas turbine coal combustor design, numerical and experimental results for tube-fin heat exchanger airflow and heating characteristics, and the computation of external hypersonic three-dimensional flow field and heat transfer characteristics.

Heat transfer in gas turbine engines and three-dimensional flows; Proceedings of the Symposium, ASME Winter Annual Meeting, Chicago, IL, Nov. 27-Dec. 2, 1988

NASA Astrophysics Data System (ADS)

Elovic, E.; O'Brien, J. E.; Pepper, D. W.

The present conference on heat transfer characteristics of gas turbines and three-dimensional flows discusses velocity-temperature fluctuation correlations at the flow stagnation flow of a circular cylinder in turbulent flow, heat transfer across turbulent boundary layers with pressure gradients, the effect of jet grid turbulence on boundary layer heat transfer, and heat transfer characteristics predictions for discrete-hole film cooling. Also discussed are local heat transfer in internally cooled turbine airfoil leading edges, secondary flows in vane cascades and curved ducts, three-dimensional numerical modeling in gas turbine coal combustor design, numerical and experimental results for tube-fin heat exchanger airflow and heating characteristics, and the computation of external hypersonic three-dimensional flow field and heat transfer characteristics.

Interactions between gravity waves and cold air outflows in a stably stratified uniform flow

NASA Technical Reports Server (NTRS)

Lin, Yuh-Lang; Wang, Ting-An; Weglarz, Ronald P.

1993-01-01

Interactions between gravity waves and cold air outflows in a stably stratified uniform flow forced by various combinations of prescribed heat sinks and sources are studied using a hydrostatic two-dimensional nonlinear numerical model. The formation time for the development of a stagnation point or reversed flow at the surface is not always directly proportional to the Froude number when wave reflections exist from upper levels. A density current is able to form by the wave-otuflow interaction, even though the Froude number is greater than a critical value. This is the result of the wave-outflow interaction shifting the flow response to a different location in the characteristic parameter space. A density current is able to form or be destroyed due to the wave-outflow interaction between a traveling gravity wave and cold air outflow. This is proved by performing experiments with a steady-state heat sink and an additional transient heat source. In a quiescent fluid, a region of cold air, convergence, and upward motion is formed after the collision between two outflows produced by two prescribed heat sinks. After the collision, the individual cold air outflows lose their own identity and merge into a single, stationary, cold air outflow region. Gravity waves tend to suppress this new stationary cold air outflow after the collision. The region of upward motion associated with the collision is confined to a very shallow layer. In a moving airstream, a density current produced by a heat sink may be suppressed or enhanced nonlinearly by an adjacent heat sink due to the wave-outflow interaction.

Magnetic heat pump flow director

NASA Technical Reports Server (NTRS)

Howard, Frank S. (Inventor)

1995-01-01

A fluid flow director is disclosed. The director comprises a handle body and combed-teeth extending from one side of the body. The body can be formed of a clear plastic such as acrylic. The director can be used with heat exchangers such as a magnetic heat pump and can minimize the undesired mixing of fluid flows. The types of heat exchangers can encompass both heat pumps and refrigerators. The director can adjust the fluid flow of liquid or gas along desired flow directions. A method of applying the flow director within a magnetic heat pump application is also disclosed where the comb-teeth portions of the director are inserted into the fluid flow paths of the heat pump.

Multiphase, multicomponent simulations and experiments of reactive flow, relevant for combining geologic CO2 sequestration with geothermal energy capture

NASA Astrophysics Data System (ADS)

Saar, Martin O.

2011-11-01

Understanding the fluid dynamics of supercritical carbon dioxide (CO2) in brine- filled porous media is important for predictions of CO2 flow and brine displacement during geologic CO2 sequestration and during geothermal energy capture using sequestered CO2 as the subsurface heat extraction fluid. We investigate multiphase fluid flow in porous media employing particle image velocimetry experiments and lattice-Boltzmann fluid flow simulations at the pore scale. In particular, we are interested in the motion of a drop (representing a CO2 bubble) through an orifice in a plate, representing a simplified porous medium. In addition, we study single-phase/multicomponent reactive transport experimentally by injecting water with dissolved CO2 into rocks/sediments typically considered for CO2 sequestration to investigate how resultant fluid-mineral reactions modify permeability fields. Finally, we investigate numerically subsurface CO2 and heat transport at the geologic formation scale.

A Global Assessment of Oceanic Heat Loss: Conductive Cooling and Hydrothermal Redistribution of Heat

NASA Astrophysics Data System (ADS)

Hasterok, D. P.; Chapman, D. S.; Davis, E. E.

2011-12-01

A new dataset of ~15000 oceanic heat flow measurements is analyzed to determine the conductive heat loss through the seafloor. Many heat flow values in seafloor younger than 60 Ma are lower than predicted by models of conductively cooled lithosphere. This heat flow deficit is caused by ventilated hydrothermal circulation discharging at crustal outcrops or through thin sedimentary cover. Globally filtering of heat flow data to retain sites with sediment cover >400 m thick and located >60 km from the nearest seamount minimizes the effect of hydrothermal ventilation. Filtered heat flow exhibit a much higher correlation coefficient with seafloor age (up to 0.95 for filtered data in contrast to 0.5 for unfiltered data) and lower variability (reduction by 30%) within an age bin. A small heat flow deficit still persists at ages <25 Ma, possibly as a result of global filtering limitations and incomplete thermal rebound following sediment burial. Detailed heat flow surveys co-located with seismic data can identify environments favoring conductive heat flow; heat flow collected in these environments is higher than that determined by the global dataset, and is more consistent with conductive cooling of the lithosphere. The new filtered data analysis and a growing number of site specific surveys both support estimates of global heat loss in the range 40-47 TW. The estimated hydrothermal deficit is consistent with estimates from geochemical studies ~7 TW, but is a few TW lower than previous estimates derived from heat flow determinations.

Magnetohydrodynamic Heat Transfer Research Related to the Design of Fusion Blankets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barleon, Leopold; Burr, Ulrich; Mack, Klaus Juergen

2001-03-15

Lithium or any lithium alloy like the lithium lead alloy Pb-17Li is an attractive breeder material used in blankets of fusion power reactors because it allows the breeding of tritium and, in the case of self-cooled blankets, the transfer of the heat generated within the liquid metal and the walls of the cooling ducts to an external heat exchanger. Nevertheless, this type of liquid-metal-cooled blanket, called a self-cooled blanket, requires specific design of the coolant ducts, because the interaction of the circulating fluid and the plasma-confining magnetic fields causes magnetohydrodynamic (MHD) effects, yielding completely different flow patterns compared to ordinarymore » hydrodynamics (OHD) and pressure drops significantly higher than there. In contrast to OHD, MHD flows depend strongly on the electrical properties of the wall. Also, MHD flows reveal anisotropic turbulence behavior and are quite sensitive to obstacles exposed to the fluid flow.A comprehensive study of the heat transfer characteristics of free and forced convective MHD flows at fusion-relevant conditions is conducted. The general ideas of the analytical and numerical models to describe MHD heat transfer phenomena in this parameter regime are discussed. The MHD laboratory being installed, the experimental program established, and the experiments on heat transfer of free and forced convective flow being conducted are described. The theoretical results are compared to the results of a series of experiments in forced and free convective MHD flows with different wall properties, such as electrically insulating as well as electric conducting ducts. Based on this knowledge, methods to improve the heat transfer by means of electromagnetic/mechanic turbulence promoters (TPs) or sophisticated, arranged electrically conducting walls are discussed, experimental results are shown, and a cost-benefit analysis related to these methods is performed. Nevertheless, a few experimental results obtained should be highlighted:1. The heat flux removable in rectangular electrically conducting ducts at walls parallel to the magnetic field is by a factor of 2 higher than in the slug flow model previously used in design calculations. Conditions for which this heat transfer enhancement is attainable are presented. The measured dimensionless pressure gradient coincides with the theoretical one and is constant throughout the whole Reynolds number regime investigated (Re = 10{sup 3} {yields} 10{sup 5}), although the flow turns from laminar to turbulent. The use of electromagnetic TPs close to the heated wall leads to nonmeasurable increase of the heat transfer in the same Re regime as long as they do not lead to an interaction with the wall adjacent boundary layers.2. Mechanical TPs used in an electrically insulated rectangular duct improved the heat transfer up to seven times compared to slug flow, but the pressure drop can increase also up to 300%. In a cost-benefit analysis, the advantageous parameter regime for applying this method is determined.3. Experiments performed in a flat box both in a vertical and a horizontal arrangement within a horizontal magnetic field show the expected increase of damping of the fluid motion with increasing Hartmann number M. At high M, buoyant convection will be completely suppressed in the horizontal case. In the vertical setup, the fluid motion is reduced to one large vortex leading to a decreasing heat transfer between heated and cooled plate to pure heat conduction.From an analysis of the experimental and theoretical results, general design criteria are derived for the orientation and shape of the first wall coolant ducts of self-cooled liquid metal blankets. Methods to generate additional turbulence within the flow, which can improve the heat transfer further are elaborated.« less

Model of Heat Exchangers for Waste Heat Recovery from Diesel Engine Exhaust for Thermoelectric Power Generation

NASA Astrophysics Data System (ADS)

Baker, Chad; Vuppuluri, Prem; Shi, Li; Hall, Matthew

2012-06-01

The performance and operating characteristics of a hypothetical thermoelectric generator system designed to extract waste heat from the exhaust of a medium-duty turbocharged diesel engine were modeled. The finite-difference model consisted of two integrated submodels: a heat exchanger model and a thermoelectric device model. The heat exchanger model specified a rectangular cross-sectional geometry with liquid coolant on the cold side, and accounted for the difference between the heat transfer rate from the exhaust and that to the coolant. With the spatial variation of the thermoelectric properties accounted for, the thermoelectric device model calculated the hot-side and cold-side heat flux for the temperature boundary conditions given for the thermoelectric elements, iterating until temperature and heat flux boundary conditions satisfied the convection conditions for both exhaust and coolant, and heat transfer in the thermoelectric device. A downhill simplex method was used to optimize the parameters that affected the electrical power output, including the thermoelectric leg height, thermoelectric n-type to p-type leg area ratio, thermoelectric leg area to void area ratio, load electrical resistance, exhaust duct height, coolant duct height, fin spacing in the exhaust duct, location in the engine exhaust system, and number of flow paths within the constrained package volume. The calculation results showed that the configuration with 32 straight fins was optimal across the 30-cm-wide duct for the case of a single duct with total height of 5.5 cm. In addition, three counterflow parallel ducts or flow paths were found to be an optimum number for the given size constraint of 5.5 cm total height, and parallel ducts with counterflow were a better configuration than serpentine flow. Based on the reported thermoelectric properties of MnSi1.75 and Mg2Si0.5Sn0.5, the maximum net electrical power achieved for the three parallel flow paths in a counterflow arrangement was 1.06 kW for package volume of 16.5 L and exhaust flow enthalpy flux of 122 kW.

Study on Gas-liquid Falling Film Flow in Internal Heat Integrated Distillation Column

NASA Astrophysics Data System (ADS)

Liu, Chong

2017-10-01

Gas-liquid internally heat integrated distillation column falling film flow with nonlinear characteristics, study on gas liquid falling film flow regulation control law, can reduce emissions of the distillation column, and it can improve the quality of products. According to the distribution of gas-liquid mass balance internally heat integrated distillation column independent region, distribution model of heat transfer coefficient of building internal heat integrated distillation tower is obtained liquid distillation falling film flow in the saturated vapour pressure of liquid water balance, using heat transfer equation and energy equation to balance the relationship between the circulating iterative gas-liquid falling film flow area, flow parameter information, at a given temperature, pressure conditions, gas-liquid flow falling film theory makes the optimal parameters to achieve the best fitting value with the measured values. The results show that the geometric gas-liquid internally heat integrated distillation column falling film flow heat exchange area and import column thermostat, the average temperature has significant. The positive correlation between the heat exchanger tube entrance due to temperature difference between inside and outside, the heat flux is larger, with the increase of internal heat integrated distillation column temperature, the slope decreases its temperature rise, which accurately describes the internal gas-liquid heat integrated distillation tower falling film flow regularity, take appropriate measures to promote the enhancement of heat transfer. It can enhance the overall efficiency of the heat exchanger.

Study of a fail-safe abort system for an actively cooled hypersonic aircraft: Computer program documentation

NASA Technical Reports Server (NTRS)

Haas, L. A., Sr.

1976-01-01

The Fail-Safe Abort System TEMPerature Analysis Program, (FASTEMP), user's manual is presented. This program was used to analyze fail-safe abort systems for an actively cooled hypersonic aircraft. FASTEMP analyzes the steady state or transient temperature response of a thermal model defined in rectangular, cylindrical, conical and/or spherical coordinate system. FASTEMP provides the user with a large selection of subroutines for heat transfer calculations. The various modes of heat transfer available from these subroutines are: heat storage, conduction, radiation, heat addition or generation, convection, and fluid flow.

Assessment of Aerothermal Heating Augmentation Attributed to Surface Catalysis in High Enthalpy Shock Tunnel Flows

NASA Astrophysics Data System (ADS)

MacLean, M.; Holden, M.

2009-01-01

The effect of gas/surface interaction in making CFD predictions of convective heating has been considered with application to ground tests performed in high enthalpy shock tunnels where additional heating augmentation attributable to surface recombination has been observed for nitrogen, air and carbon dioxide flows. For test articles constructed of stainless steel and aluminum, measurements have been made with several types of heat transfer instrumentation including thin- film, calorimeter, and coaxial thermocouple sensors. These experiments have been modeled by computations made with the high quality, chemically reacting, Navier- Stokes solver, DPLR and the heating results compared. Some typical cases considered include results on an axisymmetric sphere-cone, axisymmetric spherical capsule, spherical capsule at angle of attack, and two- dimensional cylinder. In nitrogen flows, cases considered show a recombination probability on the order of 10-3, which agrees with published data. In many cases in air and CO2, measurements exceeding the predicted level of convective heating have been observed which are consistent with approximately complete recombination (to O2/N2 or CO2) on the surface of the model (sometimes called a super-catalytic wall). It has been recognized that the conclusion that this behavior is tied to an excessively high degree of catalytic efficiency is dependent on the current understanding of the freestream and shock-layer state of the gas.

Evaporative Cooling and Dehumidification Garment for Portable Life Support Systems

NASA Technical Reports Server (NTRS)

Izenson, Michael; Chen, Weibo; Bue, Grant

2013-01-01

This paper describes the design and development of an innovative thermal and humidity control system for future space suits. The system comprises an evaporation cooling and dehumidification garment (ECDG) and a lithium chloride absorber radiator (LCAR). The ECDG absorbs heat and water vapor from inside the suit pressure garment, while the LCAR rejects heat to space without venting water vapor. The ECDG is built from thin, flexible patches with coversheets made of non-porous, water-permeable membranes that -enclose arrays of vapor flow passages. Water vapor from inside the spacesuit diffuses across the water permeable membranes, enters the vapor flow channels, and then flows to the LCAR, thus dehumidifying the internal volume of the space suit pressure garment. Additional water evaporation inside the ECDG provides cooling for sensible heat loads. -The heat released from condensation and absorption in the LCAR is rejected to the environment by thermal radiation. We have assembled lightweight and flexible ECDG pouches from prototypical materials and measured their performance in a series of separate effects tests under well-controlled, prototypical conditions. Sweating hot plate tests at typical space suit pressures show that ECDG pouches can absorb over 60 W/ft of latent heat and 20 W/ft of sensible heat from the pressure garment environment. These results are in good agreement with the predictions of our analysis models.

Investigation of waste heat recovery of binary geothermal plants using single component refrigerants

NASA Astrophysics Data System (ADS)

Unverdi, M.

2017-08-01

In this study, the availability of waste heat in a power generating capacity of 47.4 MW in Germencik Geothermal Power Plant has been investigated via binary geothermal power plant. Refrigerant fluids of 7 different single components such as R-134a, R-152a, R-227ea, R-236fa, R-600, R-143m and R-161 have been selected. The binary cycle has been modeled using the waste heat equaling to mass flow rate of 100 kg/s geothermal fluid. While the inlet temperature of the geothermal fluid into the counter flow heat exchanger has been accepted as 110°C, the outlet temperature has been accepted as 70°C. The inlet conditions have been determined for the refrigerants to be used in the binary cycle. Finally, the mass flow rate of refrigerant fluid and of cooling water and pump power consumption and power generated in the turbine have been calculated for each inlet condition of the refrigerant. Additionally, in the binary cycle, energy and exergy efficiencies have been calculated for 7 refrigerants in the availability of waste heat. In the binary geothermal cycle, it has been found out that the highest exergy destruction for all refrigerants occurs in the heat exchanger. And the highest and lowest first and second law efficiencies has been obtained for R-600 and R-161 refrigerants, respectively.

Coupled heat and silica transport associated with dike intrusion into sedimentary rock: effects on isotherm location and permeability evolution

NASA Astrophysics Data System (ADS)

Dutrow, Barbara L.; Travis, Bryan J.; Gable, Carl W.; Henry, Darrell J.

2001-11-01

An 11-meter-wide alkalic monchiquite dike recovered from the subsurface of Louisiana has produced a metasomatic aureole in the adjacent interbedded carbonate mudstones and siltstones. The asymmetric contact aureole, which extends nearly 6 m above and 4 m below the intrusion, contains the metamorphic minerals, diopside, pectolite, fluor-apophyllite, fluorite, and garnet. A series of coupled heat and mass transport calculations was undertaken to provide thermal constraints for the aureole, in the absence of robust geothermometric assemblages, and insights into accompanying mass transport associated with the sedimentary rock-dike system. Calculations were completed for systems with homogeneous, anisotropic, and layered permeability, κ. Transport, dissolution, and precipitation of silica were also incorporated into calculations. All systems modeled indicate that the thermal pulse waned in ∼3 yr with a return to background temperatures in ∼10 yr. Heat and fluid transport produce maximum temperature isotherms that are distinctly different in spatial extent and lateral variability for each numerical system. The homogeneous κ case produced isotherms that pinch and swell vertically above the dike and have large lateral variations, in contrast to the anisotropic κ case that produced a single large plume above the dike. The layered system κ case produced the most spatially extensive thermal aureole, unlike that recorded in the rocks. Addition of dissolved silica to the flow system significantly impacts the calculated transport of heat and fluid, primarily due to density changes that affect upwelling dynamics. Although precipitation and dissolution of SiO2 can affect flow through the feedback to permeability, κ changes were found to be minor for these system conditions. Where κ decreased, flow was refocused into higher κ zones, thus mitigating the κ differences over time. This negative feedback tends to defocus flow and provides a mechanism for lateral migration of plumes. Coupled heat and silica transport produces a complex isotherm geometry surrounding the intrusion due to formation of upwelling and downwelling plumes and lateral translation of plumes, leading to variability in the isotherm pattern that does not reflect the inherent heterogeneity of the initial material properties. Initial heterogeneities in κ are not a prerequisite for the development of a complicated flow and transport pattern. In addition, if isotherms reflect isograds, these calculations demonstrate that isograds may not form uniform structures with isograd boundaries characterized by their distance from the heat source.

Peristaltic flow of Powell-Eyring fluid in curved channel with heat transfer: A useful application in biomedicine.

PubMed

Hina, S; Mustafa, M; Hayat, T; Alsaedi, A

2016-10-01

In this work, we explore the heat transfer characteristics in the peristaltic transport of Powell-Eyring fluid inside a curved channel with complaint walls. The study has motivation toward the understanding of blood flow in microcirculatory system. Formulation is developed in the existence of velocity slip and temperature jump conditions. Perturbation approach has been utilized to present series expressions of axial velocity and temperature distributions. Streamlines are prepared to analyze the interesting phenomenon of trapping. Moreover, the plots of heat transfer coefficient for a broad range of embedded parameters are presented and discussed. The results indicate that slip effects substantially influence the velocity and temperature distributions. Axial flow accelerates when slip parameter is incremented. Temperature rises and wall heat flux grows when viscous dissipation effect is strengthened. In contrast to the planar channels, here velocity and temperature functions do not exhibit symmetry with respect to the central line. In addition, bolus size and its shape are different in upper and lower portions of the channel. Heat transfer coefficient enlarges when the curvature effects are reduced. The behaviors of wall tension and wall mass parameters on the profiles are qualitatively similar. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Thermally-Choked Combustor Technology

NASA Technical Reports Server (NTRS)

Knuth, William H.; Gloyer, P.; Goodman, J.; Litchford, R. J.

1993-01-01

A program is underway to demonstrate the practical feasibility of thermally-choked combustor technology with particular emphasis on rocket propulsion applications. Rather than induce subsonic to supersonic flow transition in a geometric throat, the goal is to create a thermal throat by adding combustion heat in a diverging nozzle. Such a device would have certain advantages over conventional flow accelerators assuming that the pressure loss due to heat addition does not severely curtail propulsive efficiency. As an aid to evaluation, a generalized one-dimensional compressible flow analysis tool was constructed. Simplified calculations indicate that the process is fluid dynamically and thermodynamically feasible. Experimental work is also being carried out in an attempt to develop, assuming an array of practical issues are surmountable, a practical bench-scale demonstrator using high flame speed H2/O2 combustibles.

Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts

NASA Astrophysics Data System (ADS)

Zeinali Heris, Saeed; Noie, Seyyed Hossein; Talaii, Elham; Sargolzaei, Javad

2011-12-01

In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles.

A Steady Flow Model for the Differential Emission Measure in the Solar Quiet Region

NASA Astrophysics Data System (ADS)

Bong, S.; Chae, J.; Yun, H.; Lee, J.

2001-05-01

With high quality UV spectroscopy from the SoHO spacecraft, the physical structure of the solar Transition Region (TR) is of renewed interest. We have investigated the thermodynamic structure of the TR using a one dimensional magnetic tube model constrained to Raymond & Doyle's Differential Emission Measure (DEM) in the average quiet sun. We have included the effect of the expansion of magnetic flux tube and a heating which is required in addition to conductive heat, convective energy and radiative cooling. From the resulting heating and flux tube geometry, we also investigated upflows probable in the transition region. To reproduce the Doppler shift of UV lines measured using SoHO/SUMER (Chae, Yun, & Poland 1998), flux tube needs to expand rapidly above T=105 K at a rate of radius increase up to (7.4x 10-2 km-1)~ r4.1 where r4.1 is the radius at log T = 4.1. To balance the energy, an energy supply by more than (9.3x 104 erg cm-2 s-1)~π r4.12 is required at the region between 1.3x 104 K and 2.5x 104 K regardless of filling factor, suggesting a local heating in the chromosphere. As for upflows, in subsonic flow cases, a model with the same additional energy loss as in a downflow is probable. Also, supersonic flows could be easily made and, in this case, supersonic upflows could carry extra energy to corona without increasing DEM, showing the possibility that upflows play a role in corona heating. This work was supported by the Basic Science Research Institute Program, Ministry of Education (BSRI-98-5408) and by the BK21 Project of the Korean Government.

Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

USGS Publications Warehouse

Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

2015-01-01

Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

Modeling MHD Stagnation Point Flow of Thixotropic Fluid with Non-uniform Heat Absorption/Generation

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Shah, Faisal; Khan, Muhammad Ijaz; Alsaedi, Ahmed; Yasmeen, Tabassum

2017-12-01

Here magnetohydrodynamic (MHD) stagnation point flow by nonlinear stretching sheet is discussed. Variable thickness of sheet is accounted. In addition non-uniform heat generation/absorption concept is retained. Numerical treatment to arising nonlinear system is presented. Shooting procedure is adopted for numerical treatment. Graphs and tables lead to physical description of results. It is observed that skin friction enhances for ( H a) and it decays for different rising values of ( K 1), ( K 2) and ( n). Further temperature gradient increases for higher estimation of (Pr) and decreases for larger ( H a). Major findings of present analysis are presented.

Testing of a controller for a hybrid capillary pumped loop thermal control system

NASA Technical Reports Server (NTRS)

Schweickart, Russell; Ottenstein, Laura; Cullimore, Brent; Egan, Curtis; Wolf, Dave

1989-01-01

A controller for a series hybrid capillary pumped loop (CPL) system that requires no moving parts does not resrict fluid flow has been tested and has demonstrated improved performance characteristics over a plain CPL system and simple hybrid CPL systems. These include heat load sharing, phase separation, self-regulated flow control and distribution, all independent of most system pressure drop. In addition, the controlled system demonstrated a greater heat transport capability than the simple CPL system but without the large fluid inventory requirement of the hybrid systems. A description of the testing is presented along with data that show the advantages of the system.

Heat Budget of Large Rivers: Sensitivity to Stream Morphology

NASA Astrophysics Data System (ADS)

Lancaster, S. T.; Haggerty, R.

2014-12-01

In order to assess the feasibility of effecting measurable changes in the heat budget of a large river through restoration, we use a numerical model to analyze the sensitivity of that heat budget to morphological manipulations, specifically those resulting in a narrower main channel with more alcoves. We base model parameters primarily on the gravel-bedded middle Snake River near Marsing, Idaho. The heat budget is represented by an advection-dispersion-reaction equation with, in addition to radiative, evaporative, and sensible heat fluxes, a hyporheic flux term that models lateral flow from the main stream, through bars, and into alcoves and side channels. This term effectively introduces linear dispersion of water temperatures with respect to time, so that the magnitude of the hyporheic term in the heat budget is expected to scale with the ``hyporheic number," defined as , where is dimensionless hyporheic flow rate and is dimensionless mean residence time of water entering the hyporheic zone. Simulations varying the parameters for channel width and hyporheic flow indicate that, for a large river such as the middle Snake River, feasible changes in channel width would produce downstream changes in heat flux an order of magnitude larger than would relatively extreme changes in hyporheic number. Changes, such as reduced channel width and increased hyporheic number, that tend to reduce temperatures in the summer, when temperatures are increasing with time and downstream distance, actually tend to increase temperatures in the fall, when temperatures are decreasing with time and distance.

Colorado Heat Flow Data from IHFC

DOE Data Explorer

Richard E. Zehner

2012-02-01

This layer contains the heat flow sites and data of the State of Colorado compiled from the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI) global heat flow database (www.heatflow.und.edu/index2.html). The data include different items: Item number, descriptive code, name of site, latitude and longitude, elevation, depth interval, number of temperature data, temperature gradient, number of conductivity measurement, average conductivity, number of heat generation measurements, average heat production, heat flow, number of individual sites, references, and date of publication.

Analysis of liquid-metal-jet impingement cooling in a corner region and for a row of jets

NASA Technical Reports Server (NTRS)

Siegel, R.

1975-01-01

A conformal mapping method was used to analyze liquid-metal-jet impingement heat transfer. The jet flow region and energy equation are transformed to correspond to uniform flow in a parallel plate channel with nonuniform heat addition along a portion of one wall. The exact solution for the wall-temperature distribution was obtained in the transformed channel, and the results are mapped back into the physical plane. Two geometries are analyzed. One is for a single slot jet directed either into an interior corner formed by two flat plates, or over the external sides of the corner; the flat plates are uniformly heated, and the corner can have various included angles. The heat-transfer coefficient at the stagnation point at the apex of the plates is obtained as a function of the corner angle, and temperature distributions are calculated along the heated walls. The second geometry is an infinite row of uniformly spaced parallel slot jets impinging normally against a uniformly heated plate. The heat-transfer behavior is obtained as a function of the spacing between the jets. Results are given for several jet Peclet numbers from 5 to 50.

Electro-osmotic infusion for joule heating soil remediation techniques

DOEpatents

Carrigan, Charles R.; Nitao, John J.

1999-01-01

Electro-osmotic infusion of ground water or chemically tailored electrolyte is used to enhance, maintain, or recondition electrical conductivity for the joule heating remediation technique. Induced flows can be used to infuse electrolyte with enhanced ionic conductivity into the vicinity of the electrodes, maintain the local saturation of near-electrode regions and resaturate a partially dried out zone with groundwater. Electro-osmotic infusion can also tailor the conductivity throughout the target layer by infusing chemically modified and/or heated electrolyte to improve conductivity contrast of the interior. Periodic polarity reversals will prevent large pH changes at the electrodes. Electro-osmotic infusion can be used to condition the electrical conductivity of the soil, particularly low permeability soil, before and during the heating operation. Electro-osmotic infusion is carried out by locating one or more electrodes adjacent the heating electrodes and applying a dc potential between two or more electrodes. Depending on the polarities of the electrodes, the induced flow will be toward the heating electrodes or away from the heating electrodes. In addition, electrodes carrying a dc potential may be located throughout the target area to tailor the conductivity of the target area.

The Superorbital Expansion Tube concept, experiment and analysis

NASA Technical Reports Server (NTRS)

Neely, A. J.; Morgan, R. G.

1995-01-01

In response to the need for ground testing facilities for super orbital re-entry research, a small scale facility has been set up at the University of Queensland to demonstrate the superorbital expansion tube concept. This unique device is a free piston driven, triple diaphragm, impulse shock facility which uses the enthalpy multiplication mechanism of the unsteady expansion process and the addition of a secondary shock driver to further heat the driver gas. The pilot facility has been operated to produce quasi-steady test flows in air with shock velocities in excess of 13 km/s and with a usable test flow duration of the order of 15 micro sec. an experimental condition produced in the facility with total enthalpy of 108 MJ/kg and a total pressure of 335 MPa is reported. A simple analytical flow model which accounts for non-ideal rupture of the light tertiary diaphragm and the resulting entropy increase in the test gas is discussed. It is shown that equilibrium calculations more accurately model the unsteady expansion process than calculations assuming frozen chemistry. This is because the high enthalpy flows produced in the facility can only be achieved if the chemical energy stored in the test flow during shock heating of the test gas is partially returned to the flow during the process of unsteady expansion. Measurements of heat transfer rates to a flat plate demonstrate the usability of test flow for aerothermodynamic testing and comparison of these rates with empirical calculations confirms the usable accuracy of the flow model.

Analysis on Operating Parameter Design to Steam Methane Reforming in Heat Application RDE

NASA Astrophysics Data System (ADS)

Dibyo, Sukmanto; Sunaryo, Geni Rina; Bakhri, Syaiful; Zuhair; Irianto, Ign. Djoko

2018-02-01

The high temperature reactor has been developed with various power capacities and can produce electricity and heat application. One of heat application is used for hydrogen production. Most hydrogen production occurs by steam reforming that operated at high temperature. This study aims to analyze the feasibility of heat application design of RDE reactor in the steam methane reforming for hydrogen production using the ChemCAD software. The outlet temperature of cogeneration heat exchanger is analyzed to be applied as a feed of steam reformer. Furthermore, the additional heater and calculating amount of fuel usage are described. Results show that at a low mass flow rate of feed, its can produce a temperature up to 480°C. To achieve the temperature of steam methane reforming of 850°C the additional fired heater was required. By the fired heater, an amount of fuel usage is required depending on the Reformer feed temperature produced from the heat exchanger of the cogeneration system.

Liquid circulation in a stirred system with an axial flow impeller and a cylindrical draft tube

NASA Astrophysics Data System (ADS)

Fořt, Ivan; Vlček, Petr; Jirout, Tomáš

2017-07-01

This study deals with a CFD simulation of the turbulent flow of a homogeneous liquid in a cylindrical stirred system with a pitched-blade impeller and a cylindrical draft tube. Design of investigated pilot plant equipment corresponds to the shape of agitated crystallizer with a draft tube - additional cooling heat exchanger. The results of the computation are expressed by means of the circulation pattern of a stirred liquid and the main flow characteristics of the system - the flow rate numbers and the impeller power number.

Present-day heat flow model of Mars

PubMed Central

Parro, Laura M.; Jiménez-Díaz, Alberto; Mansilla, Federico; Ruiz, Javier

2017-01-01

Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m−2, with an average value of 19 mW m−2. Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7–0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic. PMID:28367996

Dampers for Natural Draft Heaters: Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lutz, James D.; Biermayer, Peter; King, Derek

2008-10-27

Energy required for water heating accounts for approximately 40percent of national residential natural gas consumption in California. With water heating contributing such a substantial portion of natural gas consumption, it is important to pay attention to water heater efficiencies. This paper reports on an investigation of a patented, buoyancy-operated flue damper. It is an add-on design to a standard atmospherically vented natural-draft gas-fired storage water heater. The flue damper was expected to reduce off-cycle standby losses, which would lead to improvements in the efficiency of the water heater. The test results showed that the Energy Factor of the baseline watermore » heater was 0.576. The recovery efficiency was 0.768. The standby heat loss coefficient was 10.619 (BTU/hr-oF). After the damper was installed, the test results show an Energy Factor for the baseline water heater of 0.605. The recovery efficiency was 0.786. The standby heat loss coefficient was 9.135 (BTU/hr-oF). The recovery efficiency increased 2.3percent and the standby heat loss coefficient decreased 14percent. When the burner was on, the baseline water heater caused 28.0 CFM of air to flow from the room. During standby, the flow was 12.4 CFM. The addition of the damper reduced the flow when the burner was on to 23.5 CFM. During standby, flow with the damper was reduced to 11.1 CFM. The flue damper reduced off-cycle standby losses, and improved the efficiency of the water heater. The flue damper also improved the recovery efficiency of the water heater by restricting on-cycle air flows through the flue.With or without the flue damper, off-cycle air flow upthe stack is nearly half the air flow rate as when the burner is firing.« less

Two-phase flow patterns of a top heat mode closed loop oscillating heat pipe with check valves (THMCLOHP/CV)

NASA Astrophysics Data System (ADS)

Thongdaeng, S.; Bubphachot, B.; Rittidech, S.

2016-11-01

This research is aimed at studying the two-phase flow pattern of a top heat mode closed loop oscillating heat pipe with check valves. The working fluids used are ethanol and R141b and R11 coolants with a filling ratio of 50% of the total volume. It is found that the maximum heat flux occurs for the R11 coolant used as the working fluid in the case with the inner diameter of 1.8 mm, inclination angle of -90°, evaporator temperature of 125°C, and evaporator length of 50 mm. The internal flow patterns are found to be slug flow/disperse bubble flow/annular flow, slug flow/disperse bubble flow/churn flow, slug flow/bubble flow/annular flow, slug flow/disperse bubble flow, bubble flow/annular flow, and slug flow/annular flow.

Intracorporeal Heat Distribution from Fully Implantable Energy Sources for Mechanical Circulatory Support: A Computational Proof-of-Concept Study

PubMed Central

Biasetti, Jacopo; Pustavoitau, Aliaksei; Spazzini, Pier Giorgio

2017-01-01

Mechanical circulatory support devices, such as total artificial hearts and left ventricular assist devices, rely on external energy sources for their continuous operation. Clinically approved power supplies rely on percutaneous cables connecting an external energy source to the implanted device with the associated risk of infections. One alternative, investigated in the 70s and 80s, employs a fully implanted nuclear power source. The heat generated by the nuclear decay can be converted into electricity to power circulatory support devices. Due to the low conversion efficiencies, substantial levels of waste heat are generated and must be dissipated to avoid tissue damage, heat stroke, and death. The present work computationally evaluates the ability of the blood flow in the descending aorta to remove the locally generated waste heat for subsequent full-body distribution and dissipation, with the specific aim of investigating methods for containment of local peak temperatures within physiologically acceptable limits. To this aim, coupled fluid–solid heat transfer computational models of the blood flow in the human aorta and different heat exchanger architectures are developed. Particle tracking is used to evaluate temperature histories of cells passing through the heat exchanger region. The use of the blood flow in the descending aorta as a heat sink proves to be a viable approach for the removal of waste heat loads. With the basic heat exchanger design, blood thermal boundary layer temperatures exceed 50°C, possibly damaging blood cells and proteins. Improved designs of the heat exchanger, with the addition of fins and heat guides, allow for drastically lower blood temperatures, possibly leading to a more biocompatible implant. The ability to maintain blood temperatures at biologically compatible levels will ultimately allow for the body-wise distribution, and subsequent dissipation, of heat loads with minimum effects on the human physiology. PMID:29094038

No major differences found between the effects of microwave-based and conventional heat treatment methods on two different liquid foods.

PubMed

Géczi, Gábor; Horváth, Márk; Kaszab, Tímea; Alemany, Gonzalo Garnacho

2013-01-01

Extension of shelf life and preservation of products are both very important for the food industry. However, just as with other processes, speed and higher manufacturing performance are also beneficial. Although microwave heating is utilized in a number of industrial processes, there are many unanswered questions about its effects on foods. Here we analyze whether the effects of microwave heating with continuous flow are equivalent to those of traditional heat transfer methods. In our study, the effects of heating of liquid foods by conventional and continuous flow microwave heating were studied. Among other properties, we compared the stability of the liquid foods between the two heat treatments. Our goal was to determine whether the continuous flow microwave heating and the conventional heating methods have the same effects on the liquid foods, and, therefore, whether microwave heat treatment can effectively replace conventional heat treatments. We have compared the colour, separation phenomena of the samples treated by different methods. For milk, we also monitored the total viable cell count, for orange juice, vitamin C contents in addition to the taste of the product by sensory analysis. The majority of the results indicate that the circulating coil microwave method used here is equivalent to the conventional heating method based on thermal conduction and convection. However, some results in the analysis of the milk samples show clear differences between heat transfer methods. According to our results, the colour parameters (lightness, red-green and blue-yellow values) of the microwave treated samples differed not only from the untreated control, but also from the traditional heat treated samples. The differences are visually undetectable, however, they become evident through analytical measurement with spectrophotometer. This finding suggests that besides thermal effects, microwave-based food treatment can alter product properties in other ways as well.

No Major Differences Found between the Effects of Microwave-Based and Conventional Heat Treatment Methods on Two Different Liquid Foods

PubMed Central

Géczi, Gábor; Horváth, Márk; Kaszab, Tímea; Alemany, Gonzalo Garnacho

2013-01-01

Extension of shelf life and preservation of products are both very important for the food industry. However, just as with other processes, speed and higher manufacturing performance are also beneficial. Although microwave heating is utilized in a number of industrial processes, there are many unanswered questions about its effects on foods. Here we analyze whether the effects of microwave heating with continuous flow are equivalent to those of traditional heat transfer methods. In our study, the effects of heating of liquid foods by conventional and continuous flow microwave heating were studied. Among other properties, we compared the stability of the liquid foods between the two heat treatments. Our goal was to determine whether the continuous flow microwave heating and the conventional heating methods have the same effects on the liquid foods, and, therefore, whether microwave heat treatment can effectively replace conventional heat treatments. We have compared the colour, separation phenomena of the samples treated by different methods. For milk, we also monitored the total viable cell count, for orange juice, vitamin C contents in addition to the taste of the product by sensory analysis. The majority of the results indicate that the circulating coil microwave method used here is equivalent to the conventional heating method based on thermal conduction and convection. However, some results in the analysis of the milk samples show clear differences between heat transfer methods. According to our results, the colour parameters (lightness, red-green and blue-yellow values) of the microwave treated samples differed not only from the untreated control, but also from the traditional heat treated samples. The differences are visually undetectable, however, they become evident through analytical measurement with spectrophotometer. This finding suggests that besides thermal effects, microwave-based food treatment can alter product properties in other ways as well. PMID:23341982

Intracorporeal Heat Distribution from Fully Implantable Energy Sources for Mechanical Circulatory Support: A Computational Proof-of-Concept Study.

PubMed

Biasetti, Jacopo; Pustavoitau, Aliaksei; Spazzini, Pier Giorgio

2017-01-01

Mechanical circulatory support devices, such as total artificial hearts and left ventricular assist devices, rely on external energy sources for their continuous operation. Clinically approved power supplies rely on percutaneous cables connecting an external energy source to the implanted device with the associated risk of infections. One alternative, investigated in the 70s and 80s, employs a fully implanted nuclear power source. The heat generated by the nuclear decay can be converted into electricity to power circulatory support devices. Due to the low conversion efficiencies, substantial levels of waste heat are generated and must be dissipated to avoid tissue damage, heat stroke, and death. The present work computationally evaluates the ability of the blood flow in the descending aorta to remove the locally generated waste heat for subsequent full-body distribution and dissipation, with the specific aim of investigating methods for containment of local peak temperatures within physiologically acceptable limits. To this aim, coupled fluid-solid heat transfer computational models of the blood flow in the human aorta and different heat exchanger architectures are developed. Particle tracking is used to evaluate temperature histories of cells passing through the heat exchanger region. The use of the blood flow in the descending aorta as a heat sink proves to be a viable approach for the removal of waste heat loads. With the basic heat exchanger design, blood thermal boundary layer temperatures exceed 50°C, possibly damaging blood cells and proteins. Improved designs of the heat exchanger, with the addition of fins and heat guides, allow for drastically lower blood temperatures, possibly leading to a more biocompatible implant. The ability to maintain blood temperatures at biologically compatible levels will ultimately allow for the body-wise distribution, and subsequent dissipation, of heat loads with minimum effects on the human physiology.

Refining Southern California Geotherms Using Seismologic, Geologic, and Petrologic Constraints

NASA Astrophysics Data System (ADS)

Thatcher, W. R.; Chapman, D. S.; Allam, A. A.; Williams, C. F.

2017-12-01

Lithospheric deformation in tectonically active regions depends on the 3D distribution of rheology, which is in turn critically controlled by temperature. Under the auspices of the Southern California Earthquake Center (SCEC) we are developing a 3D Community Thermal Model (CTM) to constrain rheology and so better understand deformation processes within this complex but densely monitored and relatively well-understood region. The San Andreas transform system has sliced southern California into distinct blocks, each with characteristic lithologies, seismic velocities and thermal structures. Guided by the geometry of these blocks we use more than 250 surface heat-flow measurements to define 13 geographically distinct heat flow regions (HFRs). Model geotherms within each HFR are constrained by averages and variances of surface heat flow q0 and the 1D depth distribution of thermal conductivity (k) and radiogenic heat production (A), which are strongly dependent on rock type. Crustal lithologies are not always well known and we turn to seismic imaging for help. We interrogate the SCEC Community Velocity Model (CVM) to determine averages and variances of Vp, Vs and Vp/Vs versus depth within each HFR. We bound (A, k) versus depth by relying on empirical relations between seismic wave speed and rock type and laboratory and modeling methods relating (A, k) to rock type. Many 1D conductive geotherms for each HFR are allowed by the variances in surface heat flow and subsurface (A, k). An additional constraint on the lithosphere temperature field is provided by comparing lithosphere-asthenosphere boundary (LAB) depths identified seismologically with those defined thermally as the depth of onset of partial melting. Receiver function studies in Southern California indicate LAB depths that range from 40 km to 90 km. Shallow LAB depths are correlated with high surface heat flow and deep LAB with low heat flow. The much-restricted families of geotherms that intersect peridotite solidi at the seismological LAB depth in each region require that LAB temperatures lie between 1050 to 1250˚ C, a range that is consistent with a hydrous rather than anhydrous mantle below Southern California.

Storage capacity in hot dry rock reservoirs

DOEpatents

Brown, D.W.

1997-11-11

A method is described for extracting thermal energy, in a cyclic manner, from geologic strata which may be termed hot dry rock. A reservoir comprised of hot fractured rock is established and water or other liquid is passed through the reservoir. The water is heated by the hot rock, recovered from the reservoir, cooled by extraction of heat by means of heat exchange apparatus on the surface, and then re-injected into the reservoir to be heated again. Water is added to the reservoir by means of an injection well and recovered from the reservoir by means of a production well. Water is continuously provided to the reservoir and continuously withdrawn from the reservoir at two different flow rates, a base rate and a peak rate. Increasing water flow from the base rate to the peak rate is accomplished by rapidly decreasing backpressure at the outlet of the production well in order to meet periodic needs for amounts of thermal energy greater than a baseload amount, such as to generate additional electric power to meet peak demands. The rate of flow of water provided to the hot dry rock reservoir is maintained at a value effective to prevent depletion of the liquid inventory of the reservoir. 4 figs.

Storage capacity in hot dry rock reservoirs

DOEpatents

Brown, Donald W.

1997-01-01

A method of extracting thermal energy, in a cyclic manner, from geologic strata which may be termed hot dry rock. A reservoir comprised of hot fractured rock is established and water or other liquid is passed through the reservoir. The water is heated by the hot rock, recovered from the reservoir, cooled by extraction of heat by means of heat exchange apparatus on the surface, and then re-injected into the reservoir to be heated again. Water is added to the reservoir by means of an injection well and recovered from the reservoir by means of a production well. Water is continuously provided to the reservoir and continuously withdrawn from the reservoir at two different flow rates, a base rate and a peak rate. Increasing water flow from the base rate to the peak rate is accomplished by rapidly decreasing backpressure at the outlet of the production well in order to meet periodic needs for amounts of thermal energy greater than a baseload amount, such as to generate additional electric power to meet peak demands. The rate of flow of water provided to the hot dry rock reservoir is maintained at a value effective to prevent depletion of the liquid

Heat and moisture exchangers and breathing system filters: their use in anaesthesia and intensive care. Part 2 - practical use, including problems, and their use with paediatric patients.

PubMed

Wilkes, A R

2011-01-01

Heat and moisture exchangers and breathing system filters are intended to replace the normal warming, humidifying and filtering functions of the upper airways. The first part of this review considered the history, principles of operation and efficiency of these devices. The aim of this part of the review is to summarise recent guidelines on the use of these devices and outline the problems that can occur. In particular, the effect of these devices on gas analysis, dead space, resistance to gas flow and blockage of the breathing system is considered. In children, it is important to consider the addition of dead space and resistance to gas flow. A body weight of 2.5 kg is probably the lower weight limit for use with heat and moisture exchangers, and 3 kg for filters. The resistance to gas flow of a heat- and moisture-exchanging filter added to a Mapleson F breathing system can cause a delay in the induction of anaesthesia. © 2010 The Author. Anaesthesia © 2010 The Association of Anaesthetists of Great Britain and Ireland.

Passive containment cooling system

DOEpatents

Conway, Lawrence E.; Stewart, William A.

1991-01-01

A containment cooling system utilizes a naturally induced air flow and a gravity flow of water over the containment shell which encloses a reactor core to cool reactor core decay heat in two stages. When core decay heat is greatest, the water and air flow combine to provide adequate evaporative cooling as heat from within the containment is transferred to the water flowing over the same. The water is heated by heat transfer and then evaporated and removed by the air flow. After an initial period of about three to four days when core decay heat is greatest, air flow alone is sufficient to cool the containment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.

Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow canmore » explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.« less

The analysis of the flow with water injection in a centrifugal compressor stage using CFD simulation

NASA Astrophysics Data System (ADS)

Michal, Tomášek; Richard, Matas; Tomáš, Syka

2017-09-01

This text deals with the principle of direct cooling of the pressure gas in a centrifugal compressor based on evaporation of the additional fluid phase in a control domain. A decrease of the gas temperature is reached by taking the heat, which is required for evaporation of the fluid phase. The influence of additional fluid phase on the parameters of the multiphase flow is compared with the ideal gas simulation in the defined domain and with the same boundary conditions.

Visualization of various working fluids flow regimes in gravity heat pipe

NASA Astrophysics Data System (ADS)

Nemec, Patrik

Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapour and vice versa help heat pipe to transport high heat flux. Amount of heat flux transferred by heat pipe, of course depends on kind of working fluid. The article deal about visualization of various working fluids flow regimes in glass gravity heat pipe by high speed camera and processes casing inside during heat pipe operation. Experiment working fluid flow visualization is performed with two glass heat pipes with different inner diameter (13 mm and 22 mm) filled with water, ethanol and fluorinert FC 72. The working fluid flow visualization explains the phenomena as a working fluid boiling, nucleation of bubbles, and vapour condensation on the wall, vapour and condensate flow interaction, flow down condensate film thickness on the wall occurred during the heat pipe operation.

High Temperature Aquifer Storage

NASA Astrophysics Data System (ADS)

Ueckert, Martina; Niessner, Reinhard; Baumann, Thomas

2016-04-01

Combined heat and power generation (CHP) is highly efficient because excess heat is used for heating and/or process energy. However, the demand of heat energy varies considerably throughout the year while the demand for electrical energy is rather constant. It seems economically and ecologically highly beneficial for municipalities and large power consumers such as manufacturing plants to store excess heat in groundwater aquifers and to recuperate this energy at times of higher demand. Within the project High Temperature Aquifer Storage, scientists investigate storage and recuperation of excess heat energy into the bavarian Malm aquifer. Apart from high transmissivity and favorable pressure gradients, the hydrochemical conditions are crucial for long-term operation. An enormous technical challenge is the disruption of the carbonate equilibrium - modeling results indicated a carbonate precipitation of 10 - 50 kg/d in the heat exchangers. The test included five injection pulses of hot water (60 °C up to 110 °C) and four tracer pulses, each consisting of a reactive and a conservative fluorescent dye, into a depth of about 300 m b.s.l. resp. 470 m b.s.l. Injection and production rates were 15 L/s. To achieve the desired water temperatures, about 4 TJ of heat energy were necessary. Electrical conductivity, pH and temperature were recorded at a bypass where also samples were taken. A laboratory container at the drilling site was equipped for analysing the concentration of the dyes and the major cations at sampling intervals of down to 15 minutes. Additional water samples were taken and analysed in the laboratory. The disassembled heat exchanger prooved that precipitation was successfully prevented by adding CO2 to the water before heating. Nevertheless, hydrochemical data proved both, dissolution and precipitation processes in the aquifer. This was also suggested by the hydrochemical modelling with PhreeqC and is traced back to mixture dissolution and changing temperatures. Optimising the addition of CO2 might help to reduce hydrochemical processes in the aquifer. As a side effect of the extremely good hydraulic conditions, the research well was flowing freely with up to 19.4 L/s which resulted in a significant mixing of the injected water with formation waters during production. Due to the hydrochemical contrast of the sodium concentration, quantification of inflowing reservoir water was possible. Therefore, prognosis of the temperature development during the operation with flow rates of up to 60 L/s can be stated. Energy recovery consituted at the end of the heat storage test almost 50 % - without considering the influx of the cold reservoir water. Recovery rates of the fluorescent dyes are linked to their different sorption behaviour and variied between 23 % up to 79 %. The tracers are an additional tool for interpreting the groundwater flows and matrix interaction in the aquifer.

A note on drillhole depths required for reliable heat flow determinations

USGS Publications Warehouse

Chapman, D.S.; Howell, J.; Sass, J.H.

1984-01-01

In general, there is a limiting depth in a drillhole above which the reliability of a single determination of heat flow decreases rapidly with decreasing depth and below which the statistical uncertainty of a heat flow determination does not change perceptibly with increasing depth. This feature has been established empirically for a test case comprising a group of twelve heat flow sites in the Republic of Zambia. The technique consists of constructing heat flow versus depth curves for individual sites by progressively discarding data from the lower part of the hole and recomputing heat flow from the remaining data. For the Zambian test case, the curves converge towards a uniform value of 67 ?? 3 mW m-2 when all available data are used, but values of heat flow calculated for shallow(< 100 m) parts of the same holes range from 45 to 95 mW m-2. The heat flow versus depth curves are enclosed by a perturbation envelope which has an amplitude of 40 mW m-2 at the surface and decreases linearly to the noise level at 190 m. For the test region of Zambia a depth of 170 m is needed to guarantee a heat flow measurement within ?? 10% of the background regional value. It is reasonable to expect that this depth will be shallower in some regions and deeper in others. Features of heat flow perturbation envelopes can be used as quantitative reliability indices for heat flow studies. ?? 1984.

Thermal and Fluid Mechanical Investigation of an Internally Cooled Piston Rod

NASA Astrophysics Data System (ADS)

Klotsche, K.; Thomas, C.; Hesse, U.

2017-08-01

The Internal Cooling of Reciprocating Compressor Parts (ICRC) is a promising technology to reduce the temperature of the thermally stressed piston and piston rod of process gas compressors. The underlying heat transport is based on the flow of a two-phase cooling medium that is contained in the hollow reciprocating assembly. The reciprocating motion forces the phases to mix, enabling an enhanced heat transfer. In order to investigate this heat transfer, experimental results from a vertically reciprocating hollow rod are presented that show the influence of different liquid charges for different working temperatures. In addition, pressure sensors are used for a crank angle dependent analysis of the fluid mechanical processes inside the rod. The results serve to investigate the two-phase flow in terms of the velocity and distribution of the liquid and vapour phase for different liquid fractions.

Calculation of inviscid surface streamlines and heat transfer on shuttle type configurations. Part 2: Description of computer program

NASA Technical Reports Server (NTRS)

Dejarnette, F. R.; Jones, M. H.

1971-01-01

A description of the computer program used for heating rate calculation for blunt bodies in hypersonic flow is given. The main program and each subprogram are described by defining the pertinent symbols involved and presenting a detailed flow diagram and complete computer program listing. Input and output parameters are discussed in detail. Listings are given for the computation of heating rates on (1) a blunted 15 deg half-angle cone at 20 deg incidence and Mach 10.6, (2) a blunted 70 deg slab delta wing at 10 deg incidence and Mach 8, and (3) the HL-10 lifting body at 20 deg incidence and Mach 10. In addition, the computer program output for two streamlines on the blunted 15 deg half-angle cone is listed. For Part 1, see N71-36186.

Modeling 3D conjugate heat and mass transfer for turbulent air drying of Chilean papaya in a direct contact dryer

NASA Astrophysics Data System (ADS)

Lemus-Mondaca, Roberto A.; Vega-Gálvez, Antonio; Zambra, Carlos E.; Moraga, Nelson O.

2017-01-01

A 3D model considering heat and mass transfer for food dehydration inside a direct contact dryer is studied. The k- ɛ model is used to describe turbulent air flow. The samples thermophysical properties as density, specific heat, and thermal conductivity are assumed to vary non-linearly with temperature. FVM, SIMPLE algorithm based on a FORTRAN code are used. Results unsteady velocity, temperature, moisture, kinetic energy and dissipation rate for the air flow are presented, whilst temperature and moisture values for the food also are presented. The validation procedure includes a comparison with experimental and numerical temperature and moisture content results obtained from experimental data, reaching a deviation 7-10 %. In addition, this turbulent k- ɛ model provided a better understanding of the transport phenomenon inside the dryer and sample.

Results of convective heating tests of a longitudinal gap on the Rockwell flat plate model (15-0, insert 7) in the NASA/Ames Research Center

NASA Technical Reports Server (NTRS)

Quan, M.; Lockman, W. K.

1975-01-01

Results are presented which were obtained from tests in a hypersonic wind tunnel to determine aerodynamic heating rates in a gap running parallel or slightly askew to the flow direction. The model used was a flat plate instrumented in thin-skin sections with chromelconstantan thermocouples. Heating rate profiles lengthwise along and down into the gap were obtained, and additional data were obtained from a total temperature probe and rake fabricated during the test to investigate an apparent aerodynamic cooling trend in the gap. Model variables were width, depth, length, and orientation of the gap relative to the flow direction. The tests were conducted at Mach 5.1 and Reynolds numbers per foot of 500,000, 1,000,000, and 2,000,000.

An inhomogeneous thermal block model of man for the electromagnetic environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, I.; Gandhi, O.P.

An inhomogeneous four layer block thermal model of a human body, composed of 476 electromagnetic-sensitive cubical cells has been developed to study the effects of electromagnetic radiation. Varying tissue properties defined by thermal conductivity, specific heat, blood flow rate and metabolic heat production are accounted for by equations. Peripheral cell temperature is weight-averaged for total cell volume and is thereby higher than actual skin temperature. During electromagnetic field exposure, additional factors considered are increased blood flow rate caused by vasodilation and sweat-induced heat loss. Hot spots have been located in the model and numerical results are presented. Subjected to planemore » wave iradiation, the model's sweating and insensible perspiration cease and all temperatures converge. Testing during electromagnetic hyperthemia shows all temperature body parts to increase approximately at the same rate.« less

On the definition of dominant force regimes for flow boiling heat transfer by using single mini-tubes

NASA Astrophysics Data System (ADS)

Baba, Soumei; Sawada, Kenichiro; Kubota, Chisato; Kawanami, Osamu; Asano, Hitoshi; Inoue, Koichi; Ohta, Haruhiko

Recent increase in the size of space platforms requires the management of larger amount of waste heat under high heat flux conditions and the transportation of it along a long distance to the radiator. Flow boiling applied to the thermal management system in space attracts much attention as promising means to realize high-performance heat transfer and transport because of large latent heat of vaporization. In microgravity two-phase flow phenomena are quite different from those under 1-g condition because buoyancy effects are significantly reduced and surface tension becomes dominant. By the similar reason, flow boiling characteristics in mini channels are not the same as those in channels of normal sizes. In the present stage, however, the boundary between the regimes of body force dominated and of surface tension dominated is not clear. The design of space thermal devices, operated under the conditions where no effect of gravity is expected, will improve the reliability of their ground tests, provided that the boundaries of dominant force regimes are clarified quantitatively in advance. In flow boiling in mini channels or in parallel channels, back flow could be occurred because of rapid growth of bubbles in a confined space, resulting flow rate fluctuation. Flow boiling heat transfer characteristics in mini channels can be changed considerably by the existence of inlet flow rate fluctuation. It is important to pay attention to experimental accuracy and to use a single circular mini-tube to compare heat transfer characteristics with those of normal size tubes. In the present paper, effects of tube orientations, i.e. vertical upward flow, vertical downward flow and horizontal flow, on flow boiling heat transfer characteristics is investigated for FC72 flowing in single mini-tubes with inner diameters of 0.13 and 0.51 mm to establish a reliable dominant force regime map. If the regime map is described by using dimensionless groups of Bond, Weber and Froude numbers, the boundary of dominant forces of inertia and body force is examined by using the mini-tube of the larger diameter at constant Bond number Bo = 0.51, and the boundary of inertia and surface tension by using the mini-tube of smaller diameter at Bo = 0.033. The influence of inertia is varied by the change of vapor quality, i.e. ratio of vapor mass flow rate to the total, under constant mass velocities, where the velocity of liquid-vapor mixtures is increased with increasing vapor quality. For the tube diameter of 0.51 mm, under low inertia conditions at Froude number Fr < 5, heat transfer coefficients were influenced by the tube orientation, while the heat transfer coefficients were almost independent of the orientation for Fr > 5. The results indicated that the boundary between the body force dominated and the inertia force dominated regimes was given by Froude number as Fr ˜ 5. On the other hand, for tube diameter of 0.13 mm, almost no effect of tube = orientation was observed for all combinations of mass velocity and vapor quality, and heat transfer coefficients were independent of vapor quality under low inertia conditions at Weber number We < 5, and vice versa. The results implied the boundary between the surface tension dominated and the inertia force dominated regimes was represented by We ˜ 5. = In addition, by the reflection of both results on the two-dimensional regime map, the boundary between the surface tension dominated and the body force dominated regimes was approx-imately evaluated as Bo ˜ 0.25 from the crossing point of two boundary lines. This value = located in the range of 0.033 < Bo < 0.51 is consistent with the boundaries between the sur-face tension dominated and the body force dominated regimes classified for the smaller and larger mini-tubes, respectively, under low inertia conditions.

Capillary hydrodynamics and transport processes during phase change in microscale systems

NASA Astrophysics Data System (ADS)

Kuznetsov, V. V.

2017-09-01

The characteristics of two-phase gas-liquid flow and heat transfer during flow boiling and condensing in micro-scale heat exchangers are discussed in this paper. The results of numerical simulation of the evaporating liquid film flowing downward in rectangular minichannel of the two-phase compact heat exchanger are presented and the peculiarities of microscale heat transport in annular flow with phase changes are discussed. Presented model accounts the capillarity induced transverse flow of liquid and predicts the microscale heat transport processes when the nucleate boiling becomes suppressed. The simultaneous influence of the forced convection, nucleate boiling and liquid film evaporation during flow boiling in plate-fin heat exchangers is considered. The equation for prediction of the flow boiling heat transfer at low flux conditions is presented and verified using experimental data.

Mixed convective peristaltic flow of carbon nanotubes submerged in water using different thermal conductivity models.

PubMed

Hayat, T; Ahmed, Bilal; Abbasi, F M; Ahmad, B

2016-10-01

Single Walled Carbon Nanotubes (SWCNTs) are the advanced product of nanotechnology having notable mechanical and physical properties. Peristalsis of SWCNTs suspended in water through an asymmetric channel is examined. Such mechanism is studied in the presence of viscous dissipation, velocity slip, mixed convection, temperature jump and heat generation/absorption. Mathematical modeling is carried out under the low Reynolds number and long wavelength approximation. Resulting nonlinear system is solved using the perturbation technique for small Brinkman's number. Physical analysis and comparison of the results in light of three different thermal conductivity models is also provided. It is reported that the heat transfer rate at the boundary increases with an increase in the nanotubes volume fraction. The addition of nanotubes affects the pressure gradient during the peristaltic flow. Moreover, the maximum velocity of the fluid decreases due to addition of the nanotubes. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Topographically driven groundwater flow and the San Andreas heat flow paradox revisited

USGS Publications Warehouse

Saffer, D.M.; Bekins, B.A.; Hickman, S.

2003-01-01

Evidence for a weak San Andreas Fault includes (1) borehole heat flow measurements that show no evidence for a frictionally generated heat flow anomaly and (2) the inferred orientation of ??1 nearly perpendicular to the fault trace. Interpretations of the stress orientation data remain controversial, at least in close proximity to the fault, leading some researchers to hypothesize that the San Andreas Fault is, in fact, strong and that its thermal signature may be removed or redistributed by topographically driven groundwater flow in areas of rugged topography, such as typify the San Andreas Fault system. To evaluate this scenario, we use a steady state, two-dimensional model of coupled heat and fluid flow within cross sections oriented perpendicular to the fault and to the primary regional topography. Our results show that existing heat flow data near Parkfield, California, do not readily discriminate between the expected thermal signature of a strong fault and that of a weak fault. In contrast, for a wide range of groundwater flow scenarios in the Mojave Desert, models that include frictional heat generation along a strong fault are inconsistent with existing heat flow data, suggesting that the San Andreas Fault at this location is indeed weak. In both areas, comparison of modeling results and heat flow data suggest that advective redistribution of heat is minimal. The robust results for the Mojave region demonstrate that topographically driven groundwater flow, at least in two dimensions, is inadequate to obscure the frictionally generated heat flow anomaly from a strong fault. However, our results do not preclude the possibility of transient advective heat transport associated with earthquakes.

Terrestrial heat flow in east and southern Africa

NASA Astrophysics Data System (ADS)

Nyblade, Andrew A.; Pollack, Henry N.; Jones, D. L.; Podmore, Francis; Mushayandebvu, Martin

1990-10-01

We report 26 new heat flow and 13 radiogenic heat production measurements from Zimbabwe, Zambia and Tanzania, together with details and some revisions of 18 previous heat flow measurements by other investigators from Kenya and Tanzania. These measurements come from Archean cratons, Proterozoic mobile belts, and Mesozoic and Cenozoic rifts. Heat flow data from eight new sites in the Archean Zimbabwe Craton are consistent with previous measurements in the Archean Kaapvaal-Zimbabwe Craton and Limpopo Belt (Kalahari Craton) and do not change the mean heat flow of 47±2 mW m-2 (standard error of the mean) in the Kalahari Craton based on 53 previous measurements. Eight new sites in the Archean Tanzania Craton give a mean heat flow of 34±4 mW m-2. The mean heat flow from nine sites in the Proterozoic Mozambique Belt to the east of the Tanzania Craton in Kenya and Tanzania is 47±4 mW m-2. Twelve measurements in the Mesozoic rifted continental margin in east Africa give a mean heat flow of 68±4 mW m-2; four measurements in the Mesozoic Luangwa and Zambezi Rifts range from 44 to 110 mW m-2 with a mean of 76±14 mW m-2. In comparing heat flow in east and southern Africa, we observe a common heat flow pattern of increasing heat flow away from the centers of the Archean cratons. This pattern suggests a fundamental difference in lithospheric thermal structure between the Archean cratons and the Proterozoic and early Paleozoic mobile belts which surround them. Superimposed on this common pattern are two regional variations in heat flow. Heat flow in the Tanzania Craton is lower by about 13 mW m-2 than in the Kalahari Craton, and in the Mozambique Belt in east Africa heat flow is somewhat lower than in the southern African mobile belts at similar distances from the Archean cratonic margin. The two regional variations can be explained in several ways, none of which can as yet be elevated to a preferred status: (1) by variations in crustal heat production, (2) by thin-skinned thrusting of the Mozambique Belt over the Tanzania Cratonic margin, (3) by lateral heat transfer from beneath the rift flanks into the rifts, or (4) by lower mantle heat flow beneath all of eastern Africa prior to the Cenozoic development of the East African rift system.

Geothermal Heat Flux: Linking Deep Earth's Interior and the Dynamics of Large-Scale Ice Sheets

NASA Astrophysics Data System (ADS)

Rogozhina, Irina; Vaughan, Alan

2014-05-01

Regions covered by continental-scale ice sheets have the highest degree of uncertainty in composition and structure of the crust and lithospheric mantle, compounded by the poorest coverage on Earth of direct heat flow measurements. In addition to challenging conditions that make direct measurements and geological survey difficult Greenland and Antarctica are known to be geologically complex. Antarctica in particular is marked by two lithospherically distinct zones. In contrast to young and thin lithosphere of West Antarctica, East Antarctica is a collage of thick Precambrian fragments of Gondwana and earlier supercontinents. However, recent observations and modeling studies have detected large systems of subglacial lakes extending beneath much of the East Antarctic ice sheet base that have been linked to anomalously elevated heat flow. Outcrop samples from the rift margin with Australia (Prydz Bay) have revealed highly radiogenic Cambrian granite intrusives that are implicated in regional increase of crustal heat flux by a factor of two to three compared to the estimated continental background. Taken together, these indicate high variability of heat flow and properties of rocks across Antarctica. Similar conclusions have been made based on direct measurements and observations of the Greenland ice sheet. Airborne ice-penetrating radar and deep ice core projects show very high rates of basal melt for parts of the ice sheet in northern and central Greenland that have been explained by abnormally high heat flux. Archaean in age, the Greenland lithosphere was significantly reworked during the Early Proterozoic. In this region, the interpretation of independent geophysical data is complicated by Proterozoic and Phanerozoic collision zones, compounded by strong thermochemical effects of rifting along the western and eastern continental margins between 80 and 25 million years ago. In addition, high variability of heat flow and thermal lithosphere structure in central Greenland results from the remanent effects of an Early Cenozoic passage of the lithosphere above the Iceland mantle plume that is implicated in strong thermochemical erosion of the lithosphere and significant long-term effects on the present-day subglacial heat flow pattern and thermodynamic state of the Greenland ice sheet. These observations and our modeling results (Petrunin et al., 2013) show that the present-day thermal state of Greenland and Antarctic lithosphere cannot be well understood without taking into account a long-term tectonic history of these regions. The goal of the IceGeoHeat project is to combine existing independent geophysical data and innovative modeling approaches to comprehensively study the evolution and present state of the lithosphere in Greenland and Antarctica, and assess the role of geothermal heat flux in shaping the present-day ice sheet dynamics. This requires multiple collaborations involving experts across a range of disciplines. The project builds on the IceGeoHeat initiative formed in April 2012 and now including researchers from ten countries in the main core (MC) with expertise in numerical modeling and data assessment in geodynamics, geology, geothermics, cryosphere and (paleo-)climate. Petrunin, A., Rogozhina, I., Vaughan, A. P. M., Kukkonen, I. T., Kaban, M., Koulakov, I., Thomas, M. (2013): Heat flux variations beneath central Greenland's ice due to anomalously thin lithosphere. - Nature Geoscience, 6, 746-750.

Interpretation of lunar heat flow data. [for estimating bulk uranium abundance

NASA Technical Reports Server (NTRS)

Conel, J. E.; Morton, J. B.

1975-01-01

Lunar heat flow observations at the Apollo 15 and 17 sites can be interpreted to imply bulk U concentrations for the moon of 5 to 8 times those of normal chondrites and 2 to 4 times terrestrial values inferred from the earth's heat flow and the assumption of thermal steady state between surface heat flow and heat production. A simple model of nearsurface structure that takes into account the large difference in (highly insulating) regolith thickness between mare and highland provinces is considered. This model predicts atypically high local values of heat flow near the margins of mare regions - possibly a factor of 10 or so higher than the global average. A test of the proposed model using multifrequency microwave techniques appears possible wherein heat flow traverse measurements are made across mare-highland contacts. The theoretical considerations discussed here urge caution in attributing global significance to point heat-flow measurements on the moon.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Q.; Kraus, A.; Hu, R.

CFD analysis has been focused on important component-level phenomena using STARCCM+ to supplement the system analysis of integral system behavior. A notable area of interest was the cavity region. This area is of particular interest for CFD analysis due to the multi-dimensional flow and complex heat transfer (thermal radiation heat transfer and natural convection), which are not simulated directly by RELAP5. CFD simulations allow for the estimation of the boundary heat flux distribution along the riser tubes, which is needed in the RELAP5 simulations. The CFD results can also provide additional data to help establish what level of modeling detailmore » is necessary in RELAP5. It was found that the flow profiles in the cavity region are simpler for the water-based concept than for the air-cooled concept. The local heat flux noticeably increases axially, and is higher in the fins than in the riser tubes. These results were utilized in RELAP5 simulations as boundary conditions, to provide better temperature predictions in the system level analyses. It was also determined that temperatures were higher in the fins than the riser tubes, but within design limits for thermal stresses. Higher temperature predictions were identified in the edge fins, in part due to additional thermal radiation from the side cavity walls.« less

Effect of Wind Flow on Convective Heat Losses from Scheffler Solar Concentrator Receivers

NASA Astrophysics Data System (ADS)

Nene, Anita Arvind; Ramachandran, S.; Suyambazhahan, S.

2018-05-01

Receiver is an important element of solar concentrator system. In a Scheffler concentrator, solar rays get concentrated at focus of parabolic dish. While radiation losses are more predictable and calculable since strongly related to receiver temperature, convective looses are difficult to estimate in view of additional factors such as wind flow direction, speed, receiver geometry, prior to current work. Experimental investigation was carried out on two geometries of receiver namely cylindrical and conical with 2.7 m2 Scheffler to find optimum condition of tilt to provide best efficiency. Experimental results showed that as compared to cylindrical receiver, conical receiver gave maximum efficiency at 45° tilt angle. However effect of additional factors like wind speed, wind direction on especially convective losses could not be separately seen. The current work was undertaken to investigate further the same two geometries using computation fluid dynamics using FLUENT to compute convective losses considering all variables such at tilt angle of receiver, wind velocity and wind direction. For cylindrical receiver, directional heat transfer coefficient (HTC) is remarkably high to tilt condition meaning this geometry is critical to tilt leading to higher convective heat losses. For conical receiver, directional average HTC is remarkably less to tilt condition leading to lower convective heat loss.

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

PubMed Central

Gutmann, Bernhard; Glasnov, Toma N; Razzaq, Tahseen; Goessler, Walter; Roberge, Dominique M

2011-01-01

Summary The decomposition of 5-benzhydryl-1H-tetrazole in an N-methyl-2-pyrrolidone/acetic acid/water mixture was investigated under a variety of high-temperature reaction conditions. Employing a sealed Pyrex glass vial and batch microwave conditions at 240 °C, the tetrazole is comparatively stable and complete decomposition to diphenylmethane requires more than 8 h. Similar kinetic data were obtained in conductively heated flow devices with either stainless steel or Hastelloy coils in the same temperature region. In contrast, in a flow instrument that utilizes direct electric resistance heating of the reactor coil, tetrazole decomposition was dramatically accelerated with rate constants increased by two orders of magnitude. When 5-benzhydryl-1H-tetrazole was exposed to 220 °C in this type of flow reactor, decomposition to diphenylmethane was complete within 10 min. The mechanism and kinetic parameters of tetrazole decomposition under a variety of reaction conditions were investigated. A number of possible explanations for these highly unusual rate accelerations are presented. In addition, general aspects of reactor degradation, corrosion and contamination effects of importance to continuous flow chemistry are discussed. PMID:21647324

Flow monitoring of microwave pre-heated resin in LCM processes

NASA Astrophysics Data System (ADS)

Rubino, F.; Paradiso, V.; Carlone, P.

2017-10-01

Liquid composite molding is manufacturing techniques that involve the injection or infusion of catalyzed liquid resin into a mold to impregnate a dry fiber preform. The challenges of LCM processes are related to the obtaining of a complete wetting of the reinforcement as well as a reduction of the void to obtain a final product with high mechanical properties. The heating of the resin prior the injection into the mold cavity has proven to be useful to improve the LCM processes. The increasing of temperature results in a reduction of resin viscosity and allows the resin to flow more easily through the reinforcement; the cure stage is also improved resulting in a reduction of global process time required. Besides the conventional solutions to heat up the resin based on the thermal conduction, in-line microwave heating is a suitable method to heat dielectric materials providing an even temperature distribution through the resin, thereby avoiding a thermal gradient between the surface and the core of liquid resin, which could result in a premature and uncontrolled cure. In the present work, an in-line microwave system, manually controlled, have been coupled with a VARTM apparatus to heat the resin before the infusion. In addition, parallel-plate dielectric sensors and pressure sensors, embedded into the mold, were employed to track the flow front through the fiber reinforcement in two distinct cases: unheated resin and pre-heated resin. The aim of work was to assess the effectiveness of microwave pre-heating to improve the macro and micro-impregnation of dry preform. The obtained results showed capability of in-line microwave heating to shorten the impregnation of dry fabric and provide a homogeneous wetting of fibers.

Fluid-cooled heat sink with improved fin areas and efficiencies for use in cooling various devices

DOEpatents

Bharathan, Desikan; Bennion, Kevin; Kelly, Kenneth; Narumanchi, Sreekant

2015-04-21

The disclosure provides a fluid-cooled heat sink having a heat transfer base and a plurality of heat transfer fins in thermal communication with the heat transfer base, where the heat transfer base and the heat transfer fins form a central fluid channel through which a forced or free cooling fluid may flow. The heat transfer pins are arranged around the central fluid channel with a flow space provided between adjacent pins, allowing for some portion of the central fluid channel flow to divert through the flow space. The arrangement reduces the pressure drop of the flow through the fins, optimizes average heat transfer coefficients, reduces contact and fin-pin resistances, and reduces the physical footprint of the heat sink in an operating environment.

Suppression of the sonic heat transfer limit in high-temperature heat pipes

NASA Astrophysics Data System (ADS)

Dobran, Flavio

1989-08-01

The design of high-performance heat pipes requires optimization of heat transfer surfaces and liquid and vapor flow channels to suppress the heat transfer operating limits. In the paper an analytical model of the vapor flow in high-temperature heat pipes is presented, showing that the axial heat transport capacity limited by the sonic heat transfer limit depends on the working fluid, vapor flow area, manner of liquid evaporation into the vapor core of the evaporator, and lengths of the evaporator and adiabatic regions. Limited comparisons of the model predictions with data of the sonic heat transfer limits are shown to be very reasonable, giving credibility to the proposed analytical approach to determine the effect of various parameters on the axial heat transport capacity. Large axial heat transfer rates can be achieved with large vapor flow cross-sectional areas, small lengths of evaporator and adiabatic regions or a vapor flow area increase in these regions, and liquid evaporation in the evaporator normal to the main flow.

Radiative Heat Loss Measurements During Microgravity Droplet Combustion in a Slow Convective Flow

NASA Technical Reports Server (NTRS)

Hicks, Michael C.; Kaib, Nathan; Easton, John; Nayagam, Vedha; Williams, Forman A.

2003-01-01

Radiative heat loss from burning droplets in a slow convective flow under microgravity conditions is measured using a broad-band (0.6 to 40 microns) radiometer. In addition, backlit images of the droplet as well as color images of the flame were obtained using CCD cameras to estimate the burning rates and the flame dimensions, respectively. Tests were carried out in air at atmospheric pressure using n-heptane and methanol fuels with imposed forced flow velocities varied from 0 to 10 centimeters per second and initial droplet diameters varied from 1 to 3 millimeters. Slow convective flows were generated using three different experimental configurations in three different facilities in preparation for the proposed International Space Station droplet experiments. In the 2.2 Second Drop-Tower Facility a droplet supported on the leading edge of a quartz fiber is placed within a flow tunnel supplied by compressed air. In the Zero-Gravity Facility (five-second drop tower) a tethered droplet is translated in a quiescent ambient atmosphere to establish a uniform flow field around the droplet. In the KC 135 aircraft an electric fan was used to draw a uniform flow past a tethered droplet. Experimental results show that the burn rate increases and the overall flame size decreases with increases in forced-flow velocities over the range of flow velocities and droplet sizes tested. The total radiative heat loss rate, Q(sub r), decreases as the imposed flow velocity increases with the spherically symmetric combustion having the highest values. These observations are in contrast to the trends observed for gas-jet flames in microgravity, but consistent with the observations during flame spread over solid fuels where the burning rate is coupled to the forced flow as here.

Thermal Analysis of Hybrid Thermal Control System and Experimental Investigation of Flow Boiling in Micro-channel Heat Exchangers

NASA Astrophysics Data System (ADS)

Lee, Seunghyun

Future manned space endeavors will require a new class of vehicles, capable of conducting different types of missions and enduring varying gravitational and temperature environments. Thermal management will play a vital role in these new vehicles, and is complicated by the need to tackle both low and high heat sink temperatures. The present study assesses the feasibility of hybrid thermal control system by thermodynamic analysis and investigates the heat transfer mechanisms in two large micro-channel heat exchangers in vapor compression mode and two-phase mode. Unlike prior published two-phase micro-channel studies that concern mostly miniature heat sinks, this study addresses transport characteristics of a heat sink containing large length-to-diameter ratio, up to 609.6 to 1,micro-channels. In the thermodynamic analysis, four different operational modes are considered: single-phase, two-phase, basic heat pump and heat pump with liquid-side, suction-side heat exchanger. A thermodynamic trade study is conducted for six different working fluids to assess important performance parameters including mass flow rate of the working fluid, maximum pressure, radiator area, compressor/pump work, and coefficient of performance (COP). R134a is determined to be most suitable based on its ability to provide a balanced compromise between reducing flow rate and maintaining low system pressure, and a moderate coefficient of performance (COP); this fluid is also both nontoxic and nonflammable, and features zero ozone depletion potential (ODP) and low global warming potential (GWP). It is shown how specific mission stages dictate which mode of operation is most suitable, and this information is used to size the radiator for the H-TCS. The experimental flow boiling investigation consists of exploring the steady-state and the transient two-phase heat transfer characteristics of two large micro-channel heat exchangers that serve as evaporators in the vapor compression loop using R134a as refrigerant. Both heat exchangers feature parallel micro-channels with identical 1x1-mm2 cross-sections. The evaporators are connected in series, with the smaller 152.4-mm long heat exchanger situated upstream of the larger 609.6-mm long heat exchanger. In the steady-state characteristics part, it is shown low qualities are associated with slug flow and dominated by nucleate boiling, and high qualities with annular flow and convective boiling. Important transition points between the different heat transfer regimes are identified as (1) intermittent dryout, resulting from vapor blanket formation in liquid slugs and/or partial dryout in the liquid film surrounding elongated bubbles, (2) incipient dryout, resulting from dry patch formation in the annular film, and (3) complete dryout, following which the wall has to rely entirely on the mild cooling provided by droplets deposited from the vapor core. In the transient characteristics part, heat transfer measurement and high speed video are used to investigate variations of heat transfer coefficient with quality for different mass velocities and heat fluxes, as well as transient fluid flow and heat transfer behavior. An important transient phenomenon that influences both fluid flow and heat transfer is a liquid wave composed of remnants of liquid slugs from the slug flow regime. The liquid wave serves to replenish dry wall patches in the slug flow regime and to a lesser extent the annular regime. Unlike small heat sinks employed in the electronics industry, TCS heat sinks are characterized by large length-to-diameter ratio, for which limited information is presently available. The large length-to-diameter ratio of 609.6 is especially instrumental to capturing detailed axial variations of flow pattern and corresponding variations in local heat transfer coefficient. High-speed video analysis of the inlet plenum shows appreciable vapor backflow under certain operating conditions, which is also reflected in periodic oscillations in the measured pressure drop. In fact, the backflow frequency captured by video matches closely the frequency obtained from Fourier analysis of the pressure drop signal. It is shown the periodic oscillations and vapor backflow are responsible for initiating intermittent dryout and appreciable drop in local heat transfer coefficient in the downstream regions of the channels. A parametric study of oscillation frequency shows a dependence on four dimensionless parameters that account for amount of vapor generation, subcooling, and upstream liquid length, in addition to Weber number. A new correlation for oscillation frequency is constructed that captures the frequency variations relative to these individual parameters. (Abstract shortened by ProQuest.).

Experimental investigation into the interaction between the human body and room airflow and its effect on thermal comfort under stratum ventilation.

PubMed

Cheng, Y; Lin, Z

2016-04-01

Room occupants' comfort and health are affected by the airflow. Nevertheless, they themselves also play an important role in indoor air distribution. This study investigated the interaction between the human body and room airflow under stratum ventilation. Simplified thermal manikin was employed to effectively resemble the human body as a flow obstacle and/or free convective heat source. Unheated and heated manikins were designed to fully evaluate the impact of the manikin at various airflow rates. Additionally, subjective human tests were conducted to evaluate thermal comfort for the occupants in two rows. The findings show that the manikin formed a local blockage effect, but the supply airflow could flow over it. With the body heat from the manikin, the air jet penetrated farther compared with that for the unheated manikin. The temperature downstream of the manikin was also higher because of the convective effect. Elevating the supply airflow rate from 7 to 15 air changes per hour varied the downstream airflow pattern dramatically, from an uprising flow induced by body heat to a jet-dominated flow. Subjective assessments indicated that stratum ventilation provided thermal comfort for the occupants in both rows. Therefore, stratum ventilation could be applied in rooms with occupants in multiple rows. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Methodological specifics of the study of micro HPP based on internal combustion engines with air cooling and cogeneration

NASA Astrophysics Data System (ADS)

Shchinnikov, P. A.; Tomilov, V. G.; Sinelnikov, D. S.

2017-01-01

The article considers some aspects of the research methodology of micro heat power plants based on internal combustion engines with air cooling and cogeneration based on energy balance equations and the laws of heat transfer. The research is conducted for such a setup based on the Hitachi internal combustion engine with 2.4 kW capacity. It has shown the efficiency of cogeneration use in the form of useful heat flow from air, cooling the cylinder head, with its further heating by utilizing the heat of flue gases in an additional plate heat exchanger. It has been shown that the cogeneration can save fuel costs 3-10 times compared with heat guns, depending on the duration of the setup use.

Effects of lava heating on volatile-rich slopes on Io

USGS Publications Warehouse

Dundas, Colin M.

2017-01-01

The upper crust of Io may be very rich in volatile sulfur and SO2. The surface is also highly volcanically active, and slopes may be warmed by radiant heat from the lava. This is particularly the case in paterae, which commonly host volcanic eruptions and long-lived lava lakes. Paterae slopes are highly variable, but some are greater than 70°. I model the heating of a volatile slope for two end-member cases: instantaneous emplacement of a large sheet flow, and persistent heating by a long-lived lava lake. In general, single flows can briefly raise sulfur to the melting temperature, or drive a modest amount of sublimation of SO2. Persistently lava-covered surfaces will drive much more significant geomorphic effects, with potentially significant sublimation and slope retreat. In addition to the direct effects, heating is likely to weaken slope materials and may trigger mass wasting. Thus, if the upper crust of Io is rich in these volatile species, future missions with high-resolution imaging are likely to observe actively retreating slopes around lava lakes and other locations of frequent eruptions.

Exploring the Cattaneo-Christov heat flux phenomenon on a Maxwell-type nanofluid coexisting with homogeneous/heterogeneous reactions

NASA Astrophysics Data System (ADS)

Sarkar, Amit; Kundu, Prabir Kumar

2017-12-01

This specific article unfolds the efficacy of Cattaneo-Christov heat flux on the heat and mass transport of Maxwell nanofluid flow over a stretched sheet with changeable thickness. Homogeneous/heterogeneous reactions in the fluid are additionally considered. The Cattaneo-Christov heat flux model is initiated in the energy equation. Appropriate similarity transformations are taken up to form a system of nonlinear ODEs. The impact of related parameters on the nanoparticle concentration and temperature is inspected through tables and diagrams. It is renowned that temperature distribution increases for lower values of the thermal relaxation parameter. The rate of mass transfer is enhanced for increasing in the heterogeneous reaction parameter but the reverse tendency is ensued for the homogeneous reaction parameter. On the other side, the rate of heat transfer is getting enhanced for the Cattaneo-Christov model compared to the classical Fourier's model for some flow factors. Thus the implication of the current study is to delve its unique effort towards the generalized version of traditional Fourier's law at nano level.

Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

NASA Astrophysics Data System (ADS)

Goodge, John W.

2018-02-01

Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow in East Antarctica come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. As has been done with bedrock exposed along coastal margins and in rare inland outcrops, valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th, and K concentrations in a suite of Proterozoic (1.2-2.0 Ga) granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho) of about 2.6 ± 1.9 µW m-3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo) ranging from 33 to 84 mW m-2 and an average of 48.0 ± 13.6 mW m-2. Estimates of heat production obtained for this suite of glacially sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with an average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal characteristics of the granites indicate that crust in central East Antarctica resembles that in the Proterozoic Arunta and Tennant Creek inliers of Australia but is dissimilar to other areas like the Central Australian Heat Flow Province that are characterized by anomalously high heat flow. Age variation within the sample suite indicates that central East Antarctic lithosphere is heterogeneous, yet the average heat production and heat flow of four age subgroups cluster around the group mean, indicating minor variation in the thermal contribution to the overlying ice sheet from upper crustal heat production. Despite these minor differences, ice-sheet models may favor a geologically realistic input of crustal heat flow represented by the distribution of ages and geothermal characteristics found in these glacial clasts.

Effects of partial slip boundary condition and radiation on the heat and mass transfer of MHD-nanofluid flow

NASA Astrophysics Data System (ADS)

Abd Elazem, Nader Y.; Ebaid, Abdelhalim

2017-12-01

In this paper, the effect of partial slip boundary condition on the heat and mass transfer of the Cu-water and Ag-water nanofluids over a stretching sheet in the presence of magnetic field and radiation. Such partial slip boundary condition has attracted much attention due to its wide applications in industry and chemical engineering. The flow is basically governing by a system of partial differential equations which are reduced to a system of ordinary differential equations. This system has been exactly solved, where exact analytical expression has been obtained for the fluid velocity in terms of exponential function, while the temperature distribution, and the nanoparticles concentration are expressed in terms of the generalized incomplete gamma function. In addition, explicit formulae are also derived from the rates of heat transfer and mass transfer. The effects of the permanent parameters on the skin friction, heat transfer coefficient, rate of mass transfer, velocity, the temperature profile, and concentration profile have been discussed through tables and graphs.

The effect of nitrogen gas flow rate on heat treatment of AISI SS-430: Study of microstructure and hardness

NASA Astrophysics Data System (ADS)

Sebayang, Perdamean; Darmawan, Bobby Aditya; Simbolon, Silviana; Alfirano, Sudiro, Toto; Aryanto, Didik

2018-05-01

The aim of this research was to obtain the austenite phase from ferritic stainless steel through sample heat treatment. The AISI 430 ferritic steel with the thickness of about 0.4 mm was used. The heat treatment was conducted in a tube furnace at elevated temperature of 1150, 1200, 1250 °C and nitrogen gas flow rate of 0.57 and 0.73 l/s. The samples were then rapidly quenched in water bath. An optical microscope, XRD, SEM-EDS and micro vickers hardness tester were used to characterize the sample before and after het treatment. The presence of anneal twins indicated the formation of austenite phase in the sample. Its fraction was varied from 10.89 wt% to 35.10 wt%. In addition, the heat treatment temperature strongly affected the sample hardness. The optimum hardness obtained was about 542.69 HV. According to the results, this material can be considered for biomedical applications.

Physics and chemistry of plasma-assisted combustion.

PubMed

Starikovskiy, Andrey

2015-08-13

There are several mechanisms that affect a gas when using discharge plasma to initiate combustion or to stabilize a flame. There are two thermal mechanisms-the homogeneous and inhomogeneous heating of the gas due to 'hot' atom thermalization and vibrational and electronic energy relaxation. The homogeneous heating causes the acceleration of the chemical reactions. The inhomogeneous heating generates flow perturbations, which promote increased turbulence and mixing. Non-thermal mechanisms include the ionic wind effect (the momentum transfer from an electric field to the gas due to the space charge), ion and electron drift (which can lead to additional fluxes of active radicals in the gradient flows in the electric field) and the excitation, dissociation and ionization of the gas by e-impact, which leads to non-equilibrium radical production and changes the kinetic mechanisms of ignition and combustion. These mechanisms, either together or separately, can provide additional combustion control which is necessary for ultra-lean flames, high-speed flows, cold low-pressure conditions of high-altitude gas turbine engine relight, detonation initiation in pulsed detonation engines and distributed ignition control in homogeneous charge-compression ignition engines, among others. Despite the lack of knowledge in mechanism details, non-equilibrium plasma demonstrates great potential for controlling ultra-lean, ultra-fast, low-temperature flames and is extremely promising technology for a very wide range of applications. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Rapid heat-flowing surveying of geothermal areas, utilizing individual snowfalls as calorimeters

USGS Publications Warehouse

White, Donald E.

1969-01-01

Local differences in rate of heat transfer in vapor and by conduction through the ground in hot spring areas are difficult and time-consuming to measure quantitatively. Individual heavy snowfalls provide a rapid low-cost means of measuring total heat flow from such ground. After a favorable snowfall (heavy, brief duration, little wind, air temperature near 0°C), contacts between snow-covered and snow-free ground are mapped on a suitable base. Each mapped contact, as time elapses after a specific snowfall, is a heat-flow contour representing a decreasing rate of flow. Calibration of each mapped contact or snow line is made possible by the fact that snow remains on insulated surfaces (such as the boardwalks of Yellowstone's thermal areas) long after it has melted on adjacent warm ground. Heat-flow contours mapped to date range from 450 to 5500 μcal/cm2 sec, or 300 to 3700 times the world average of conductive heat flow. The very high rates of heat flow (2000 to > 10,000 μcal/cm2 sec) are probably too high, and the lower heat flows determinable by the method (2 sec) may be too low. Values indicated by the method are, however, probably within a factor of 2 of the total conductive and convective heat flow. Thermal anomalies from infrared imagery are similar in shape to heat-flow contours of a test area near Old Faithful geyser. Snowfall calorimetry provides a rapid means for evaluating the imagery and computer-derived products of the infrared data in terms of heat flow.

Systematic heat flow measurements across the Wagner Basin, northern Gulf of California

NASA Astrophysics Data System (ADS)

Neumann, Florian; Negrete-Aranda, Raquel; Harris, Robert N.; Contreras, Juan; Sclater, John G.; González-Fernández, Antonio

2017-12-01

A primary control on the geodynamics of rifting is the thermal regime. To better understand the geodynamics of rifting in the northern Gulf of California we systematically measured heat-flow across the Wagner Basin, a tectonically active basin that lies near the southern terminus of the Cerro Prieto fault. The heat flow profile is 40 km long, has a nominal measurement spacing of ∼1 km, and is collocated with a seismic reflection profile. Heat flow measurements were made with a 6.5-m violin-bow probe. Although heat flow data were collected in shallow water, where there are significant temporal variations in bottom water temperature, we use CTD data collected over many years to correct our measurements to yield accurate values of heat flow. After correction for bottom water temperature, the mean and standard deviation of heat flow across the western, central, and eastern parts of the basin are 220 ± 60, 99 ± 14, 889 ± 419 mW m-2, respectively. Corrections for sedimentation would increase measured heat flow across the central part of basin by 40 to 60%. We interpret the relatively high heat flow and large variability on the western and eastern flanks in terms of upward fluid flow at depth below the seafloor, whereas the lower and more consistent values across the central part of the basin are suggestive of conductive heat transfer. Moreover, heat flow across the central basin is consistent with gabbroic underplating at a depth of 15 km and suggests that continental rupture here has not gone to completion.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barleon, L.; Buehler, L.; Molokov, S.

Magnetohydrodynamic (MHD) flow through a 90{degrees} bend, in which the flow is turned from the direction perpendicular to magnetic field lines into a direction aligned with the field, is characterized by strong three-dimensional effects leading to additional pressure drop and large deformations in the velocity distribution. Since such bends are basic elements of a fusion reactor blanket, the question whether the additional pressure drop exceeds unacceptable limits or whether the change in flow distribution may lead to unfavorable heat transfer conditions as to be answered. To investigate MHD flows in a right angle bend, several experiments have been performed inmore » a wide range of the relevant parameters. In the lower range of the interaction parameter N (N {much_lt} 10{sup 4}) the total pressure drop over the whole bend shows a pronounced N-dependence but only a weak dependence on the Hartmann number M. Both effects can be combined to a pressure drop correlation. At higher values of N and M the experimental results for pressure drop and potential distribution agree rather well with theoretical ones obtained on the basis of an asymptotic approach for high N and M. It can be shown theoretically and confirmed by the experiment that, even at high N and M the additional pressure drop in a right angle bend is not excessively high. For the investigated bend with conducting channel walls the predicted flow distribution does not show any stagnant zone at the high heat flux walls in the perfectly aligned part of the duct. This result, however, could not be checked experimentally because there is still no reliable velocity measurement technique available for field-aligned flows.« less

Post-Dryout Heat Transfer to a Refrigerant Flowing in Horizontal Evaporator Tubes

NASA Astrophysics Data System (ADS)

Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi; Fukuda, Kenichi

Studies of the post-dryout heat transfer were made based on the experimental data for HFC-134a flowing in horizontal smooth and spiral1y grooved (micro-fin) tubes and the characteristics of the post-dryout heat transfer were c1arified. The heat transfer coefficient at medium and high mass flow rates in the smooth tube was lower than the single-phase heat transfer coefficient of the superheated vapor flow, of which mass flow rate was given on the assumption that the flow was in a thermodynamic equilibrium. A prediction method of post-dryout heat transfer coefficient was developed to reproduce the measurement satisfactorily for the smooth tube. The post dryout heat transfer in the micro-fin tube can be regarded approximately as a superheated vapor single-phase heat transfer.

Towards High-Frequency Shape Memory Alloy Actuators Incorporating Liquid Metal Energy Circuits

NASA Astrophysics Data System (ADS)

Hartl, Darren; Mingear, Jacob; Bielefeldt, Brent; Rohmer, John; Zamarripa, Jessica; Elwany, Alaa

2017-12-01

Large shape memory alloy (SMA) actuators are currently limited to applications with low cyclic actuation frequency requirements due to their generally poor heat transfer rates. This limitation can be overcome through the use of distributed body heating methods such as induction heating or by accelerated cooling methods such as forced convection in internal cooling channels. In this work, a monolithic SMA beam actuator containing liquid gallium-indium alloy-filled channels is fabricated through additive manufacturing. These liquid metal channels enable a novel multi-physical thermal control system, allowing for increased heating and cooling rates to facilitate an increased cyclic actuation frequency. Liquid metal flowing in the channels performs the dual tasks of inductively heating the surrounding SMA material and then actively cooling the SMA via forced internal fluid convection. A coupled thermoelectric model, implemented in COMSOL, predicts a possible fivefold increase in the cyclic actuation frequency due to these increased thermal transfer rates when compared to conventional SMA forms having external heating coils and being externally cooled via forced convection. The first ever experimental prototype SMA actuator of this type is described and, even at much lower flow rates, is shown to exhibit a decrease in cooling time of 40.9%.

Fluid-cooled heat sink for use in cooling various devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bharathan, Desikan; Bennion, Kevin; Kelly, Kenneth

The disclosure provides a fluid-cooled heat sink having a heat transfer base, a shroud, and a plurality of heat transfer fins in thermal communication with the heat transfer base and the shroud, where the heat transfer base, heat transfer fins, and the shroud form a central fluid channel through which a forced or free cooling fluid may flow. The heat transfer pins are arranged around the central fluid channel with a flow space provided between adjacent pins, allowing for some portion of the central fluid channel flow to divert through the flow space. The arrangement reduces the pressure drop ofmore » the flow through the fins, optimizes average heat transfer coefficients, reduces contact and fin-pin resistances, and reduces the physical footprint of the heat sink in an operating environment.« less

Study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flows

NASA Astrophysics Data System (ADS)

Boltenko, E. A.

2016-10-01

The results of the experimental study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flow are presented. The experiments were carried out using electric heated annular channels with one and (or) two heat-release surfaces. For the organization of transit flow on a convex heat-release surface, four longitudinal ribs were installed uniformly at its perimeter. Swirl flow was realized using a capillary wound tightly (without gaps) on the ribs. The ratio between swirl and transit flows in the annular gap was varied by applying longitudinal ribs of different height. The experiments were carried out using a closed-type circulatory system. The experimental data were obtained in a wide range of regime parameters. Both water heated to the temperature less than the saturation temperature and water-steam mixture were fed at the inlet of the channels. For the measurement of the temperature of the heat-release surfaces, chromel-copel thermocouples were used. It was shown that the presence of swirl flow on a convex heatrelease surface led to a significant decrease in critical heat flows (CHF) compared to a smooth surface. To increase CHF, it was proposed to use the interaction of swirl flows of the heat carrier. The second swirl flow was transit flow, i.e., swirl flow with the step equal to infinity. It was shown that CHF values for a channel with swirl and transit flow in all the studied range of regime parameters was higher than CHF values for both a smooth annular channel and a channel with swirl. The empirical ratios describing the dependence of CHF on convex and concave heat-release surfaces of annular channels with swirl and transit flow on the geometrical characteristics of channels and the regime parameters were obtained. The experiments were carried out at the pressure p = 3.0-16.0 MPa and the mass velocity ρw = 250-3000 kg/(m2s).

Heat flow, deep formation temperature and thermal structure of the Tarim Basin, northwest China

NASA Astrophysics Data System (ADS)

Liu, Shaowen; Lei, Xiao; Feng, Changge; Li, Xianglan

2016-04-01

Geothermal regime of a sedimentary basin not only provides constraint on understanding the basin formation and evolution, but also offers fundamental parameters for hydrocarbon resources assessment. As one of three Precambrian blocks in China, the Tarim craton is also a current hydrocarbon exploration target where the largest sedimentary basin (Tarim Basin) develops with great potential. Although considerable advancement of geothermal regime of this basin has been made during the past decades, nearly all the temperature data in previous studies are from the exploration borehole formation testing temperatures. Recently, we have conducted the steady-state temperature logging in the Tarim basin, and measured abundant rock thermal properties, enabling us to re-visit the thermal regime of this area with more confidence. Our results show that the present-day geothermal gradients for the Tarim Basin vary from 23 K/km to 27 K/km, with a mean of 22 K/km; the values of heat flow range from 40 mW/m2 to 49 mW/m2, with a mean of 43 mW/m2. These new data confirmed that the Tarim Basin has relatively low heat flow and shares similar geothermal regime with other Precambrian cratons in the world. In addition, the new temperatures from the steady-state logs are larger than the bottom hole temperatures (BHT) as 22 degree Celsius, indicating the thermal non-equilibrium for the BHTs used in previous studies. Spatial distribution of the estimated formation temperatures-at-depth of 1~5km within the basin is similar and mainly controlled by crystalline basement pattern. Generally, the temperatures at the depth of 1km range from 29 to 41 degree Celsius, with a mean of 35 degree Celsius; while the temperatures at 3km vary from 63 to 100 degree Celsius, and the mean is 82 degree Celsius; at 5km below the surface, the temperatures fall into a range between 90 and 160 degree Celsius, with a mean of 129 degree Celsius. We further proposed the long-term low geothermal background and large burial depth are the favorable conditions for hydrocarbon generation and preservation. As far as heat budget of the Tarim Basin is concerned, the radiogenic heat from the sedimentary cover accounts only for 20 percent of the surface heat flow (~9 mW/m2), while the mantle heat flow is estimated to be low as 6~15 mW/m2; this indicates the dominant contribution of crustal radiogenic heat to the observed heat flow. Any variations in surface heat flow for the Tarim Basin can be due only to changes in crustal heat production. Thermal contrast between the Tarim Basin and Tibet Plateau, represented by a difference in surface heat flow and deep crustal temperature, is remarkable. This inherited thermal contrast can be traced as far as before the India-Asia collision. Moreover, the lithosphere beneath the Tarim Basin is sufficiently strong to resist the gravitational potential energy difference and tectonic forces from Tibet. The observed thermal and rheological contrast accounts for the differential Cenozoic deformation in the Tarim Basin and adjacent areas.

Shielded regeneration heating element for a particulate filter

DOEpatents

Gonze, Eugene V [Pinckney, MI; Ament, Frank [Troy, MI

2011-01-04

An exhaust system includes a particulate filter (PF) that is disposed downstream from an engine. The PF filters particulates within an exhaust from the engine. A heating element heats particulate matter in the PF. A catalyst substrate or a flow converter is disposed upstream from said heating element. The catalyst substrate oxidizes the exhaust prior to reception by the heating element. The flow converter converts turbulent exhaust flow to laminar exhaust flow prior to reception by the heating element.

Experimental evidence of thermal vibrational convection in a nonuniformly heated fluid in a reduced gravity environment.

PubMed

Mialdun, A; Ryzhkov, I I; Melnikov, D E; Shevtsova, V

2008-08-22

We report experimental evidence of convection caused by translational vibration of nonuniformly heated fluid in low gravity. The theory of vibrational convection in weightlessness is well developed but direct experimental proof has been missing. An innovative point of the experiment is the observation of a temperature field in the front and side views of the cubic cell. In addition, particle tracing is employed. The evolution of this field is studied systematically in a wide range of frequencies and amplitudes. The flow structures reported in previous numerical studies are confirmed. The transition from four-vortex flow to the pattern with three vortices is observed in the transient state.

Microwave heating of aqueous samples on a micro-optical-electro-mechanical system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beer, Neil Reginald

2016-04-12

Apparatus for heating a sample includes a microchip; a microchannel flow channel in the microchip, the microchannel flow channel containing the sample; a microwave source that directs microwaves onto the sample for heating the sample; a wall section of the microchannel flow channel that receives the microwaves and enables the microwaves to pass through wall section of the microchannel flow channel, the wall section the microchannel flow channel being made of a material that is not appreciably heated by the microwaves; a carrier fluid within the microchannel flow channel for moving the sample in the microchannel flow channel, the carriermore » fluid being made of a material that is not appreciably heated by the microwaves; wherein the microwaves pass through wall section of the microchannel flow channel and heat the sample.« less

Microwave heating of aqueous samples on a micro-optical-electro-mechanical system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beer, Neil Reginald

Apparatus for heating a sample includes a microchip; a microchannel flow channel in the microchip, the microchannel flow channel containing the sample; a microwave source that directs microwaves onto the sample for heating the sample; a wall section of the microchannel flow channel that receives the microwaves and enables the microwaves to pass through wall section of the microchannel flow channel, the wall section the microchannel flow channel being made of a material that is not appreciably heated by the microwaves; a carrier fluid within the microchannel flow channel for moving the sample in the microchannel flow channel, the carriermore » fluid being made of a material that is not appreciably heated by the microwaves; wherein the microwaves pass through wall section of the microchannel flow channel and heat the sample.« less

Tuning near field radiative heat flux through surface excitations with a metal insulator transition.

PubMed

van Zwol, P J; Ranno, L; Chevrier, J

2012-06-08

The control of heat flow is a formidable challenge due to lack of good thermal insulators. Promising new opportunities for heat flow control were recently theoretically discovered for radiative heat flow in near field, where large heat flow contrasts may be achieved by tuning electronic excitations on surfaces. Here we show experimentally that the phase transition of VO2 entails a change of surface polariton states that significantly affects radiative heat transfer in near field. In all cases the Derjaguin approximation correctly predicted radiative heat transfer in near field, but it underestimated the far field limit. Our results indicate that heat flow contrasts can be realized in near field that can be larger than those obtained in far field.

Wall Area of Influence and Growing Wall Heat Transfer due to Sliding Bubbles in Subcooled Boiling Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Junsoo; Estrada-Perez, Carlos E.; Hassan, Yassin A.

A variety of dynamical features of sliding bubbles and their impact on wall heat transfer were observed at subcooled flow boiling conditions in a vertical square test channel. Among the wide range of parameters observed, we particularly focus in this paper on (i) the sliding bubbles’ effect on wall heat transfer (supplemantry discussion to the authors’ previous work in Yoo et al. (2016a,b)) and (ii) the wall area influenced by sliding bubbles in subcooled boiling flow. At first, this study reveals that the degree of wall heat transfer improvement due to sliding bubbles depended less on the wall superheat conditionmore » as the mass flux increased. Also, the sliding bubble trajectory was found to be one of the critical factors in order to properly describe the wall heat transfer associated with sliding bubbles. In particular, the wall area influenced by sliding bubbles depended strongly on both sliding bubble trajectory and sliding bubble size; the sliding bubble trajectory was also observed to be closely related to the sliding bubble size. Importantly, these results indicate the limitation of current approach in CFD analyses especially for the wall area of bubble influence. In addition, the analyses on the temporal fraction of bubbles’ residence (FR) along the heated wall show that the sliding bubbles typically travel through narrow path with high frequency while the opposite was observed downstream. That is, both FR and sliding bubble trajectory depended substantially on the distance from nucleation site, which is expected to be similar for the quenching heat transfer mode induced by sliding bubbles.« less

Field emission microplasma actuation for microchannel flows

NASA Astrophysics Data System (ADS)

Sashank Tholeti, Siva; Shivkumar, Gayathri; Alexeenko, Alina A.

2016-06-01

Microplasmas offer attractive flow control methodology for gas transport in microsystems where large viscous losses make conventional pumping methods highly inefficient. We study microscale flow actuation by dielectric-barrier discharge (DBD) with field emission (FE) of electrons, which allows lowering the operational voltage from kV to a few hundred volts and below. A feasibility study of FE-DBD for flow actuation is performed using 2D particle-in-cell method with Monte Carlo collisions (PIC/MCC) at 10 MHz in nitrogen at atmospheric pressure. The free diffusion dominated, high velocity field emission electrons create a large positive space charge and a body force on the order of 106 N m-3. The body force and Joule heat decrease with increase in dielectric thickness and electrode thickness. The body force also decreases at lower pressures. The plasma body force distribution along with the Joule heating is then used in the Navier-Stokes simulations to quantify the flow actuation in a microchannel. Theoretical analysis and simulations for plasma actuated planar Poiseuille flow show that the gain in flow rate is inversely proportional to Reynolds number. This theoretical analysis is in good agreement with the simulations for a microchannel with closely placed actuators under incompressible conditions. Flow rate of FE-DBD driven 2D microchannel is around 100 ml min-1 mm-1 for an input power of 64 μW mm-1. The gas temperature rises by 1500 K due to the Joule heating, indicating FE-DBD’s potential for microcombustion, micropropulsion and chemical sensing in addition to microscale pumping and mixing applications.

Combined Lorentz force and ultrasound Doppler velocimetry in a vertical convection liquid metal flow

NASA Astrophysics Data System (ADS)

Zürner, Till; Vogt, Tobias; Resagk, Christian; Eckert, Sven; Schumacher, Jörg

2017-11-01

We report experimental studies on turbulent vertical convection flow in the liquid metal alloy gallium-indium-tin. Flow measurements were conducted by a combined use of local Lorentz force velocimetry (LLFV) and ultrasound Doppler velocimetry (UDV). It is known that the forced convection flow in a duct generates a force on the LLFV magnet system, that grows proportional to the flow velocity. We show that for the slower flow of natural convection LLFV retains this linear dependence in the range of micronewtons. Furthermore experimental results on the scaling of heat and momentum transport with the thermal driving are presented. The results cover a range of Rayleigh numbers 3 ×105 < Ra < 3 ×107 at a Prandtl number Pr 0.032 . The Nusselt number Nu is found to scale as Nu Ra0.31 . A Reynolds number Rez based on the vertical velocities close the heated and cooled side walls scales with Rez Ra0.45 . Additionally a Reynolds number based on the horizontal flow component is scaling as Rex Ra0.67 . These results agree well with numerical simulations and theoretical predictions. This work is funded by the Deutsche Forschungsgemeinschaft under Grant No. GRK 1567.

Entropy Generation in Regenerative Systems

NASA Technical Reports Server (NTRS)

Kittel, Peter

1995-01-01

Heat exchange to the oscillating flows in regenerative coolers generates entropy. These flows are characterized by oscillating mass flows and oscillating temperatures. Heat is transferred between the flow and heat exchangers and regenerators. In the former case, there is a steady temperature difference between the flow and the heat exchangers. In the latter case, there is no mean temperature difference. In this paper a mathematical model of the entropy generated is developed for both cases. Estimates of the entropy generated by this process are given for oscillating flows in heat exchangers and in regenerators. The practical significance of this entropy is also discussed.

A review of surface heat-flow data of the northern Middle Atlas (Morocco)

NASA Astrophysics Data System (ADS)

Chiozzi, Paolo; Barkaoui, Alae-Eddine; Rimi, Abdelkrim; Verdoya, Massimo; Zarhloule, Yassine

2017-12-01

We revised thermal data available from water and oil wells in the northern sector of the Middle Atlas region. To avoid biased estimation of surface heat flow caused by advection likely occurring in shallow aquifers, temperature measurements in water boreholes were carefully inspected and selected. The heat flow in the oil wells was inferred by taking into account the porosity variation with depth, the temperature effect on thermal conductivity of the matrix and the pore fluid, together with the contribution of the radiogenic heat production. Moreover, the possible bias in heat flow caused by convection occurring in confined carbonate aquifers was evaluated. The results of heat flow slightly modify the picture reported in previous investigations. The heat flow value over the investigated region is rather uniform (about 80 mW m-2) and is similar in oil wells and in water boreholes. Geothermal calculations indicate that such a surface heat flow is compatible with a ∼70 km thick thermal lithosphere and normal thermal conditions in the asthenospheric mantle.

Re-evaluation of heat flow data near Parkfield, CA: Evidence for a weak San Andreas Fault

USGS Publications Warehouse

Fulton, P.M.; Saffer, D.M.; Harris, Reid N.; Bekins, B.A.

2004-01-01

Improved interpretations of the strength of the San Andreas Fault near Parkfield, CA based on thermal data require quantification of processes causing significant scatter and uncertainty in existing heat flow data. These effects include topographic refraction, heat advection by topographically-driven groundwater flow, and uncertainty in thermal conductivity. Here, we re-evaluate the heat flow data in this area by correcting for full 3-D terrain effects. We then investigate the potential role of groundwater flow in redistributing fault-generated heat, using numerical models of coupled heat and fluid flow for a wide range of hydrologic scenarios. We find that a large degree of the scatter in the data can be accounted for by 3-D terrain effects, and that for plausible groundwater flow scenarios frictional heat generated along a strong fault is unlikely to be redistributed by topographically-driven groundwater flow in a manner consistent with the 3-D corrected data. Copyright 2004 by the American Geophysical Union.

Upgraded flowing liquid lithium limiter for improving Li coverage uniformity and erosion resistance in EAST device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuo, G. Z.; Hu, J. S.; Maingi, R.

In this paper, we report on design and technology improvements for a flowing liquid lithium (FLiLi) limiter inserted into auxiliary heated discharges in the experimental advanced superconducting tokamak device. In order to enhance Li coverage uniformity and erosion resistance, a new liquid Li distributor with homogenous channels was implemented. In addition, two independent electromagnetic pumps and a new horizontal capillary structure contributed to an improvement in the observed Li flow uniformity (from 30% in the previous FLiLi design to >80% in this FLiLi design). To improve limiter surface erosion resistance, hot isostatic press technology was applied, which improved the thermalmore » contact between thin stainless steel protective layers covering the Cu heat sink. The thickness of the stainless steel layer was increased from 0.1 mm to 0.5 mm, which also helped macroscopic erosion resilience. Finally, despite the high auxiliary heating power up to 4.5 MW, no Li bursts were recorded from FLiLi, underscoring the improved performance of this new design.« less

Mathematical modeling of the human body during water replacement and dehydration: body water changes.

PubMed

Downey, D; Seagrave, R C

2000-03-01

A model of the human body that integrates the variables involved in temperature regulation and blood gas transport within the cardiovascular and respiratory systems is presented here. It expands upon previous work to describe the competition between skin and muscles when both require increased blood flows during exercise and/or heat stress. First, a detailed study of the control relations used to predict skin blood flow was undertaken. Four other control relations employed in the model were also examined and modified as indicated by empirical results found in literature. Internal responses to exercise and/or heat stress can affect both thermoregulation and the cardiorespiratory system. Dehydration was studied in addition to complete water replacement during similar environmental and exercise situations. Control relations for skin blood flow and evaporative heat loss were modified and a water balance was added to study how the loss of water through sweat can be limiting. Runoff from sweating as a function of relative humidity was introduced along with evaporation, and these results were compared to data to validate the model.

Laminar, Transitional, and Turbulent Heating on Mid Lift-to-Drag Ratio Entry Vehicles

NASA Technical Reports Server (NTRS)

Hollis, Brian R.; Hollingsworth, Kevin E.

2012-01-01

The boundary-layer transition characteristics and convective aeroheating levels on mid lift-to-drag ratio entry vehicle configurations have been studied through wind tunnel testing. Several configurations were investigated, including elliptically-blunted cylinders with both circular and elliptically-flattened cross sections, biconic geometries based on launch vehicle dual-use shrouds, and parametrically-optimized analytic geometries. Vehicles of this class have been proposed for high-mass Mars missions, such as sample return and crewed exploration, for which the conventional sphere-cone entry-vehicle geometries of previous Mars missions are insufficient. Testing was conducted at Mach 6 over a range of Reynolds numbers sufficient to generate laminar, transitional, and turbulent flow. Transition onset locations - both straight-line and cross-flow - and heating rates were obtained through global phosphor thermography. Supporting computations were performed to obtain heating rates for comparison with the data. Laminar data and predictions agreed to well within the experimental uncertainty. Fully-turbulent data and predictions also agreed well. However, in transitional flow regions, greater differences were observed. Additional aerodynamic performance data were also generated through Modified-Newtonian analyses of the geometries.

Upgraded flowing liquid lithium limiter for improving Li coverage uniformity and erosion resistance in EAST device

DOE PAGES

Zuo, G. Z.; Hu, J. S.; Maingi, R.; ...

2017-12-14

In this paper, we report on design and technology improvements for a flowing liquid lithium (FLiLi) limiter inserted into auxiliary heated discharges in the experimental advanced superconducting tokamak device. In order to enhance Li coverage uniformity and erosion resistance, a new liquid Li distributor with homogenous channels was implemented. In addition, two independent electromagnetic pumps and a new horizontal capillary structure contributed to an improvement in the observed Li flow uniformity (from 30% in the previous FLiLi design to >80% in this FLiLi design). To improve limiter surface erosion resistance, hot isostatic press technology was applied, which improved the thermalmore » contact between thin stainless steel protective layers covering the Cu heat sink. The thickness of the stainless steel layer was increased from 0.1 mm to 0.5 mm, which also helped macroscopic erosion resilience. Finally, despite the high auxiliary heating power up to 4.5 MW, no Li bursts were recorded from FLiLi, underscoring the improved performance of this new design.« less

Transport Phenomena in Fluid Dynamics: Matrix Heat Exchangers and Their Applications in Energy Systems

DTIC Science & Technology

2009-07-01

presented a summary of recent research on boiling in microchannels . He addressed the topics of macro scale versus micro scale heat transfer , two phase...flow regime, flow boiling 14 heat transfer results for microchannels , heat transfer mechanisms in microchannels , and flow boiling models for... Heat Transfer Boiling In Minichannel And Microchannel Flow Passages Of Compact Evaporators, Keynote Lecture Presented at the Engineering Foundation

Numerical investigation of internal high-speed viscous flows using a parabolic technique

NASA Technical Reports Server (NTRS)

Anderson, O. L.; Power, G. D.

1985-01-01

A feasibility study has been conducted to assess the applicability of an existing parabolic analysis (ADD-Axisymmetric Diffuser Duct), developed previously for subsonic viscous internal flows, to mixed supersonic/subsonic flows with heat addition simulating a SCRAMJET combustor. A study was conducted with the ADD code modified to include additional convection effects in the normal momentum equation when supersonic expansion and compression waves are present. A set of test problems with weak shock and expansion waves have been analyzed with this modified ADD method and stable and accurate solutions were demonstrated provided the streamwise step size was maintained at levels larger than the boundary layer displacement thickness. Calculations made with further reductions in step size encountered departure solutions consistent with strong interaction theory. Calculations were also performed for a flow field with a flame front in which a specific heat release was imposed to simulate a SCRAMJET combustor. In this case the flame front generated relatively thick shear layers which aggravated the departure solution problem. Qualitatively correct results were obtained for these cases using a marching technique with the convective terms in the normal momentum equation suppressed. It is concluded from the present study that for the class of problems where strong viscous/inviscid interactions are present a global iteration procedure is required.

Numerical simulation of hydrothermal circulation in the Cascade Range, north-central Oregon

USGS Publications Warehouse

Ingebritsen, S.E.; Paulson, K.M.

1990-01-01

Alternate conceptual models to explain near-surface heat-flow observations in the central Oregon Cascade Range involve (1) an extensive mid-crustal magmatic heat source underlying both the Quaternary arc and adjacent older rocks or (2) a narrower deep heat source which is flanked by a relatively shallow conductive heat-flow anomaly caused by regional ground-water flow (the lateral-flow model). Relative to the mid-crustal heat source model, the lateral-flow model suggests a more limited geothermal resource base, but a better-defined exploration target. We simulated ground-water flow and heat transport through two cross sections trending west from the Cascade range crest in order to explore the implications of the two models. The thermal input for the alternate conceptual models was simulated by varying the width and intensity of a basal heat-flow anomaly and, in some cases, by introducing shallower heat sources beneath the Quaternary arc. Near-surface observations in the Breitenbush Hot Springs area are most readily explained in terms of lateral heat transport by regional ground-water flow; however, the deep thermal structure still cannot be uniquely inferred. The sparser thermal data set from the McKenzie River area can be explained either in terms of deep regional ground-water flow or in terms of a conduction-dominated system, with ground-water flow essentially confined to Quaternary rocks and fault zones.

Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

NASA Astrophysics Data System (ADS)

Majorowicz, Jacek A.; Embry, Ashton F.

1998-06-01

Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep wells of the Canadian Arctic Archipelago. Corrected bottom hole temperature (BHT) data and drill stem test (DST) temperatures were used to determine the thermal gradients for sites for which the quality of data was sufficient. Thermal gradients evaluated for depths below the base of permafrost for the onshore wells and below sea bottom for the offshore wells were combined with the estimates of effective thermal conductivity to approximate heat flow for these sites. The present geothermal gradient is in the 15-50 mK/m range (mean = 31 ± 7 mK/m). Present heat flow is mainly in the 35-90 mW/m 2 range (mean = 53 ± 12 mW/m 2). Maps of the present geothermal gradient and present heat flow have been constructed for the basin. The analysis of vitrinite reflectance profiles and the calculation of logarithmic coalification gradients for 101 boreholes in the Sverdrup Basin showed large variations related in many cases to regional variations of present terrestrial heat flow. Paleo-geothermal gradients estimated from these data are mostly in the range of 15-50 mK/m (mean = 28 ± 9 mK/m) and paleo-heat flow is in the 40-90 mW/m 2 range (mean = 57 ± 18 mW/m 2) related to the time of maximum burial in the Early Tertiary. Mean values of the present heat flow and paleo-heat flow for the Sverdrup Basin are almost identical considering the uncertainties of the methods used (53 ± 12 versus 57 ± 18 mW/m 2, respectively). Present geothermal gradients and paleo-geothermal gradients are also close when means are compared (31 ± 7 versus 28 ± 9 mK/m respectively). A zone of high present heat flow and a paleo-heat flow zone coincide in places with the northeastern-southwestern incipient rift landward of the Arctic margin first described by Balkwill and Fox (1982). Correlation between present heat flow and paleo-heat flow for the time of maximum burial in the earliest Tertiary suggests that the high heat flow zone has prevailed since that time.

Laboratory simulation of heat exchange for liquids with Pr > 1: Heat transfer

NASA Astrophysics Data System (ADS)

Belyaev, I. A.; Zakharova, O. D.; Krasnoshchekova, T. E.; Sviridov, V. G.; Sukomel, L. A.

2016-02-01

Liquid metals are promising heat transfer agents in new-generation nuclear power plants, such as fast-neutron reactors and hybrid tokamaks—fusion neutron sources (FNSs). We have been investigating hydrodynamics and heat exchange of liquid metals for many years, trying to reproduce the conditions close to those in fast reactors and fusion neutron sources. In the latter case, the liquid metal flow takes place in a strong magnetic field and strong thermal loads resulting in development of thermogravitational convection in the flow. In this case, quite dangerous regimes of magnetohydrodynamic (MHD) heat exchange not known earlier may occur that, in combination with other long-known regimes, for example, the growth of hydraulic drag in a strong magnetic field, make the possibility of creating a reliable FNS cooling system with a liquid metal heat carrier problematic. There exists a reasonable alternative to liquid metals in FNS, molten salts, namely, the melt of lithium and beryllium fluorides (Flibe) and the melt of fluorides of alkali metals (Flinak). Molten salts, however, are poorly studied media, and their application requires detailed scientific substantiation. We analyze the modern state of the art of studies in this field. Our contribution is to answer the following question: whether above-mentioned extremely dangerous regimes of MHD heat exchange detected in liquid metals can exist in molten salts. Experiments and numerical simulation were performed in order to answer this question. The experimental test facility represents a water circuit, since water (or water with additions for increasing its electrical conduction) is a convenient medium for laboratory simulation of salt heat exchange in FNS conditions. Local heat transfer coefficients along the heated tube, three-dimensional (along the length and in the cross section, including the viscous sublayer) fields of averaged temperature and temperature pulsations are studied. The probe method for measurements in a flow is described in detail. Experimental data are designated for verification of codes simulating heat exchange of molten salts.

A computational analysis subject to thermophysical aspects of Sisko fluid flow over a cylindrical surface

NASA Astrophysics Data System (ADS)

Awais, M.; Khalil-Ur-Rehman; Malik, M. Y.; Hussain, Arif; Salahuddin, T.

2017-09-01

The present analysis is devoted to probing the salient features of the mixed convection and non-linear thermal radiation effects on non-Newtonian Sisko fluid flow over a linearly stretching cylindrical surface. Properties of heat transfer are outlined via variable thermal conductivity and convective boundary conditions. The boundary layer approach is implemented to construct the mathematical model in the form of partial differential equations. Then, the requisite PDEs are transmuted into a complex ordinary differential system by invoking appropriate dimensionless variables. Solution of subsequent ODEs is obtained by utilizing the Runge-Kutta algorithm (fifth order) along with the shooting scheme. The graphical illustrations are presented to interpret the features of the involved pertinent flow parameters on concerning profiles. For a better description of the fluid flow, numerical variations in local skin friction coefficient and local Nusselt number are scrutinized in tables. From thorough analysis, it is inferred that the mixed convection parameter and the curvature parameter increase the velocity while temperature shows a different behavior. Additionally, both momentum and thermal distribution of fluid flow decrease with increasing values of the non-linearity index. Furthermore, variable thermal parameter and heat generation/absorption parameter amplify the temperature significantly. The skin friction is an increasing function of all momentum controlling parameters. The local Nusselt number also shows a similar behavior against heat radiation parameter and variable thermal conductivity parameter while it shows a dual nature for the heat generation/absorption parameter. Finally, the obtained results are validated by comparison with the existing literature and hence the correctness of the analysis is proved.

Equilibrium radiative heating tables for aerobraking in the Martian atmosphere

NASA Astrophysics Data System (ADS)

Hartung, Lin C.; Sutton, Kenneth; Brauns, Frank

1990-05-01

Studies currently underway for Mars missions often envision the use of aerobraking for orbital capture at Mars. These missions generally involve blunt-nosed vehicles to dissipate the excess energy of the interplanetary transfer. Radiative heating may be of importance in these blunt-body flows because of the highly energetic shock layer around the blunt nose. In addition, the Martian atmosphere contains CO2, whose dissociation products are known to include strong radiators. An inviscid, equilibrium, stagnation point, radiation-coupled flow-field code has been developed for investigating blunt-body atmospheric entry. The method has been compared with ground-based and flight data for air, and reasonable agreement has been found. In the present work, the method was applied to a matrix of conditions in the Martian atmosphere. These conditions encompass most trajectories of interest for Mars exploration spacecraft. The predicted equilibrium radiative heating to the stagnation point of the vehicle is presented.

Numerical simulation for aspects of homogeneous and heterogeneous reactions in forced convection flow of nanofluid

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Shah, Faisal; Khan, Muhammad Ijaz; Alsaedi, Ahmed

2018-03-01

Mixed convection stagnation point flow of nanofluid by a vertical permeable circular cylinder has been addressed. Water is treated as ordinary liquid while nanoparticles include aluminium oxide, copper and titanium dioxide. Homogeneous-heterogeneous reactions are considered. The nonlinear higher order expressions are changed into first ordinary differential equations and then solved by built-in-Shooting method in mathematica. The results of velocity, temperature, concentration, skin friction and local Nusselt number are discussed. Our results demonstrate that surface drag force and heat transfer rate are enhanced linearly for higher estimation of curvature parameter. Further surface drag force decays for aluminium oxide and it enhances for copper nanoparticle. Heat transfer rate enhances with increasing all three types of nanoparticles. In addition, the lowest heat transfer rate is obtained in case of titanium dioxide when compared with copper and aluminium oxide.

BLOOD PRESSURE REGULATION III: WHAT HAPPENS WHEN ONE SYSTEM MUST SERVE TWO MASTERS: TEMPERATURE AND PRESSURE REGULATION?

PubMed Central

Kenney, W. Larry; Stanhewicz, Anna E.; Bruning, Rebecca S.; Alexander, Lacy M.

2013-01-01

When prolonged intense exercise is performed at high ambient temperatures, cardiac output must meet dual demands for increased blood flow to contracting muscle and to the skin. The literature has commonly painted this scenario as a fierce competition, wherein one circulation preserves perfusion at the expense of the other, with the regulated maintenance of blood pressure as the ultimate goal. This review redefines this scenario as commensalism, an integrated balance of regulatory control where one circulation benefits with little functional effect on the other. In young, healthy subjects, arterial pressure rarely falls to any great extent during either extreme passive heating or prolonged dynamic exercise in the heat. Nor does body temperature rise disproportionately due to a compromised skin blood flow. Rather, it often takes the superimposition of additional stressors – e.g., dehydration or simulated hemorrhage – upon heat stress to substantially impact blood pressure regulation. PMID:23636697

Blood pressure regulation III: what happens when one system must serve two masters: temperature and pressure regulation?

PubMed

Kenney, W Larry; Stanhewicz, Anna E; Bruning, Rebecca S; Alexander, Lacy M

2014-03-01

When prolonged intense exercise is performed at high ambient temperatures, cardiac output must meet dual demands for increased blood flow to contracting muscle and to the skin. The literature has commonly painted this scenario as a fierce competition, wherein one circulation preserves perfusion at the expense of the other, with the regulated maintenance of blood pressure as the ultimate goal. This review redefines this scenario as commensalism, an integrated balance of regulatory control where one circulation benefits with little functional effect on the other. In young, healthy subjects, arterial pressure rarely falls to any great extent during either extreme passive heating or prolonged dynamic exercise in the heat, nor does body temperature rise disproportionately due to a compromised skin blood flow. Rather, it often takes the superimposition of additional stressors--e.g., dehydration or simulated hemorrhage--upon heat stress to substantially impact blood pressure regulation.

Forced-flow once-through boilers. [structural design criteria/aerospace environments

NASA Technical Reports Server (NTRS)

Stone, J. R.; Gray, V. H.; Gutierrez, O. A.

1975-01-01

A compilation and review of NASA-sponsored research on boilers for use in spacecraft electrical power generation systems is presented. Emphasis is on the heat-transfer and fluid-flow problems. In addition to space applications, much of the boiler technology is applicable to terrestrial and marine uses such as vehicular power, electrical power generation, vapor generation, and heating and cooling. Related research areas are discussed such as condensation, cavitation, line and boiler dynamics, the SNAP-8 project (Mercury-Rankine cycle), and conventional terrestrial boilers (either supercritical or gravity-assisted liquid-vapor separation types). The research effort was directed at developing the technology for once-through compact boilers with high heat fluxes to generate dry vapor stably, without utilizing gravity for phase separations. A background section that discusses, tutorially, the complex aspects of the boiling process is presented. Discussions of tests on alkali metals are interspersed with those on water and other fluids on a phenomenological basis.

Numerical simulation of supersonic gap flow.

PubMed

Jing, Xu; Haiming, Huang; Guo, Huang; Song, Mo

2015-01-01

Various gaps in the surface of the supersonic aircraft have a significant effect on airflows. In order to predict the effects of attack angle, Mach number and width-to-depth ratio of gap on the local aerodynamic heating environment of supersonic flow, two-dimensional compressible Navier-Stokes equations are solved by the finite volume method, where convective flux of space term adopts the Roe format, and discretization of time term is achieved by 5-step Runge-Kutta algorithm. The numerical results reveal that the heat flux ratio is U-shaped distribution on the gap wall and maximum at the windward corner of the gap. The heat flux ratio decreases as the gap depth and Mach number increase, however, it increases as the attack angle increases. In addition, it is important to find that chamfer in the windward corner can effectively reduce gap effect coefficient. The study will be helpful for the design of the thermal protection system in reentry vehicles.

Equilibrium radiative heating tables for aerobraking in the Martian atmosphere

NASA Technical Reports Server (NTRS)

Hartung, Lin C.; Sutton, Kenneth; Brauns, Frank

1990-01-01

Studies currently underway for Mars missions often envision the use of aerobraking for orbital capture at Mars. These missions generally involve blunt-nosed vehicles to dissipate the excess energy of the interplanetary transfer. Radiative heating may be of importance in these blunt-body flows because of the highly energetic shock layer around the blunt nose. In addition, the Martian atmosphere contains CO2, whose dissociation products are known to include strong radiators. An inviscid, equilibrium, stagnation point, radiation-coupled flow-field code has been developed for investigating blunt-body atmospheric entry. The method has been compared with ground-based and flight data for air, and reasonable agreement has been found. In the present work, the method was applied to a matrix of conditions in the Martian atmosphere. These conditions encompass most trajectories of interest for Mars exploration spacecraft. The predicted equilibrium radiative heating to the stagnation point of the vehicle is presented.

Effects of spatial gradients in thermophysical properties on the topology of turbulence in heated channel flow of supercritical fluids

NASA Astrophysics Data System (ADS)

Azih, Chukwudi; Yaras, Metin I.

2018-01-01

The current literature suggests that large spatial gradients of thermophysical properties, which occur in the vicinity of the pseudo-critical thermodynamic state, may result in significant variations in forced-convection heat transfer rates. Specifically, these property gradients induce inertia- and buoyancy-driven phenomena that may enhance or deteriorate the turbulence-dominated heat convection process. Through direct numerical simulations, the present study investigates the role of coherent flow structures in channel geometries for non-buoyant and buoyant flows of supercritical water, with buoyant configurations involving wall-normal oriented gravitational acceleration and downstream-oriented gravitational acceleration. This sequence of simulations enables the evaluation of the relative contributions of inertial and buoyancy phenomena to heat transfer variations. In these simulations, the state of the working fluid is in the vicinity of the pseudo-critical point. The uniform wall heat flux and the channel mass flux are specified such that the heat to mass flux ratio is 3 kJ/kg, with an inflow Reynolds number of 12 000 based on the channel hydraulic diameter, the area-averaged inflow velocity, and fluid properties evaluated at the bulk temperature and pressure of the inflow plane. In the absence of buoyancy forces, notable reductions in the density and viscosity in close proximity of the heated wall are observed to promote generation of small-scale vortices, with resultant breakdown into smaller scales as they interact with preexisting larger near-wall vortices. This interaction results in a reduction in the overall thermal mixing at particular wall-normal regions of the channel. Under the influence of wall-normal gravitational acceleration, the wall-normal density gradients are noted to enhance ejection motions due to baroclinic vorticity generation on the lower wall, thus providing additional wall-normal thermal mixing. Along the upper wall, the same mechanism generates streamwise vorticity of the opposing sense of rotation in the close vicinity to the respective legs of the hairpin vortices causing a net reduction in thermal mixing. Finally, in the case of downstream-oriented gravitational acceleration, baroclinic vorticity generation as per spanwise density gradients causes additional wall-normal thermal mixing by promoting larger-scale ejection and sweep motions.

Interaction of Shallow Cold Surges with Topography on Scales of 100-1000 Kilometers.

NASA Astrophysics Data System (ADS)

Toth, James John

1987-09-01

A shallow cold air mass is defined as one not extending to the top of the mountain ridge with which it interacts. The structure of such an airmass is examined using both observational data and a hydrostatic version of the Colorado State University Regional Atmospheric Modeling System. The prime constraint on a shallow cold surge is that the flow must ultimately be parallel to the mountain ridge. It is found that the effects of this constraint are altered significantly by surface sensible heat flux. Cold surges are slowed during the daylight hours, a result consistent with previous observational studies in Colorado east of the Continental Divide. Two case studies are described in detail, and several other events are cited. Since observations alone do not provide a complete description of diversion of the cold air by the mountain range, numerical model simulations provide additional insight into important mechanisms. A case study on 14 June 1985 is described using observational and model data. The model development of a deep boundary layer within the frontal baroclinic zone is consistent with the observations for this and other cases. This development is due to strong surface heating. Turning off the model shortwave radiation is seen to produce a rapid southward acceleration of the surface front, with very shallow cold air behind the front. Model simulations with specified surface temperature differences confirm the importance of upward heat flux from the surface in slowing the southward movement of the cold surge. It is concluded that the slowing is not due simply to the thermal wind developing in response to the heating of higher terrain to the west. Since surface heating is distributed over a deeper layer on the warm side of the temperature discontinuity, there is frontolysis at the surface. But this modification would develop even over flat terrain. Sloping terrain introduces additional effects. Heating at the western, upslope side of the cold surge inhibits the development of pressure gradients favorable to northerly flow. A second contribution comes from westerly winds at ridgetop level. These winds are heated over the higher terrain and flow downslope, further retarding the progression of the cold air at the surface.

Flow and Pollutant Transport in Urban Street Canyons of Different Aspect Ratios with Ground Heating: Large-Eddy Simulation

NASA Astrophysics Data System (ADS)

Li, Xian-Xiang; Britter, Rex E.; Norford, Leslie K.; Koh, Tieh-Yong; Entekhabi, Dara

2012-02-01

A validated large-eddy simulation model was employed to study the effect of the aspect ratio and ground heating on the flow and pollutant dispersion in urban street canyons. Three ground-heating intensities (neutral, weak and strong) were imposed in street canyons of aspect ratio 1, 2, and 0.5. The detailed patterns of flow, turbulence, temperature and pollutant transport were analyzed and compared. Significant changes of flow and scalar patterns were caused by ground heating in the street canyon of aspect ratio 2 and 0.5, while only the street canyon of aspect ratio 0.5 showed a change in flow regime (from wake interference flow to skimming flow). The street canyon of aspect ratio 1 does not show any significant change in the flow field. Ground heating generated strong mixing of heat and pollutant; the normalized temperature inside street canyons was approximately spatially uniform and somewhat insensitive to the aspect ratio and heating intensity. This study helps elucidate the combined effects of urban geometry and thermal stratification on the urban canyon flow and pollutant dispersion.

Experimental study on heat transfer performance of fin-tube exchanger and PSHE for waste heat recovery

NASA Astrophysics Data System (ADS)

Chen, Ting; Bae, Kyung Jin; Kwon, Oh Kyung

2018-02-01

In this paper, heat transfer characteristics of fin-tube heat exchanger and primary surface heat exchanger (PSHE) used in waste heat recovery were investigated experimentally. The flow in the fin-tube heat exchanger is cross flow and in PSHE counter flow. The variations of friction factor and Colburn j factor with air mass flow rate, and Nu number with Re number are presented. Various comparison methods are used to evaluate heat transfer performance, and the results show that the heat transfer rate of the PSHE is on average 17.3% larger than that of fin-tube heat exchanger when air mass flow rate is ranging from 1.24 to 3.45 kg/min. However, the PSHE causes higher pressure drop, and the fin-tube heat exchanger has a wider application range which leads to a 31.7% higher value of maximum heat transfer rate compared to that of the PSHE. Besides, under the same fan power per unit frontal surface, a higher heat transfer rate value is given in the fin-tube heat exchanger.

Exhaust bypass flow control for exhaust heat recovery

DOEpatents

Reynolds, Michael G.

2015-09-22

An exhaust system for an engine comprises an exhaust heat recovery apparatus configured to receive exhaust gas from the engine and comprises a first flow passage in fluid communication with the exhaust gas and a second flow passage in fluid communication with the exhaust gas. A heat exchanger/energy recovery unit is disposed in the second flow passage and has a working fluid circulating therethrough for exchange of heat from the exhaust gas to the working fluid. A control valve is disposed downstream of the first and the second flow passages in a low temperature region of the exhaust heat recovery apparatus to direct exhaust gas through the first flow passage or the second flow passage.

On the development of OpenFOAM solvers based on explicit and implicit high-order Runge-Kutta schemes for incompressible flows with heat transfer

NASA Astrophysics Data System (ADS)

D'Alessandro, Valerio; Binci, Lorenzo; Montelpare, Sergio; Ricci, Renato

2018-01-01

Open-source CFD codes provide suitable environments for implementing and testing low-dissipative algorithms typically used to simulate turbulence. In this research work we developed CFD solvers for incompressible flows based on high-order explicit and diagonally implicit Runge-Kutta (RK) schemes for time integration. In particular, an iterated PISO-like procedure based on Rhie-Chow correction was used to handle pressure-velocity coupling within each implicit RK stage. For the explicit approach, a projected scheme was used to avoid the "checker-board" effect. The above-mentioned approaches were also extended to flow problems involving heat transfer. It is worth noting that the numerical technology available in the OpenFOAM library was used for space discretization. In this work, we additionally explore the reliability and effectiveness of the proposed implementations by computing several unsteady flow benchmarks; we also show that the numerical diffusion due to the time integration approach is completely canceled using the solution techniques proposed here.

Solution of magnetohydrodynamic flow and heat transfer of radiative viscoelastic fluid with temperature dependent viscosity in wire coating analysis

PubMed Central

Khan, Muhammad Altaf; Siddiqui, Nasir; Ullah, Murad; Shah, Qayyum

2018-01-01

Wire coating process is a continuous extrusion process for primary insulation of conducting wires with molten polymers for mechanical strength and protection in aggressive environments. In the present study, radiative melt polymer satisfying third grade fluid model is used for wire coating process. The effect of magnetic parameter, thermal radiation parameter and temperature dependent viscosity on wire coating analysis has been investigated. Reynolds model and Vogel’s models have been incorporated for variable viscosity. The governing equations characterizing the flow and heat transfer phenomena are solved analytically by utilizing homotopy analysis method (HAM). The computed results are also verified by ND-Solve method (Numerical technique) and Adomian Decomposition Method (ADM). The effect of pertinent parameters is shown graphically. In addition, the instability of the flow in the flows of the wall of the extrusion die is well marked in the case of the Vogel model as pointed by Nhan-Phan-Thien. PMID:29596448

Flow Regime Identification of Horizontal Two Phase Refrigerant R-134a Flow Using Neural Networks (Postprint)

DTIC Science & Technology

2013-11-01

Flows in Microchannels ," Heat Transfer Engineering, Vol. 27, No. 9, 2006, pp. 4-19. 2Kandlikar, S. G., " Heat Transfer Mechanisms During Flow...Boiling in Microchannels ," Journal of Heat Transfer , Vol. 126, No. 1, 2004, pp. 8-16. 3Kreitzer, P. J., Byrd, L., and Willebrand, B. J., "Initial...an integral aspect of modeling two phase flows as most pressure drop and heat transfer correlations rely on a priori knowledge of the flow regime for

Time variability in Cenozoic reconstructions of mantle heat flow: plate tectonic cycles and implications for Earth's thermal evolution.

PubMed

Loyd, S J; Becker, T W; Conrad, C P; Lithgow-Bertelloni, C; Corsetti, F A

2007-09-04

The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by approximately 0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.

Time variability in Cenozoic reconstructions of mantle heat flow: Plate tectonic cycles and implications for Earth's thermal evolution

PubMed Central

Loyd, S. J.; Becker, T. W.; Conrad, C. P.; Lithgow-Bertelloni, C.; Corsetti, F. A.

2007-01-01

The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by ∼0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past. PMID:17720806

Architecture for Absorption Based Heaters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moghaddam, Saeed; Chugh, Devesh

An absorption based heater is constructed on a fluid barrier heat exchanging plate such that it requires little space in a structure. The absorption based heater has a desorber, heat exchanger, and absorber sequentially placed on the fluid barrier heat exchanging plate. The vapor exchange faces of the desorber and the absorber are covered by a vapor permeable membrane that is permeable to a refrigerant vapor but impermeable to an absorbent. A process fluid flows on the side of the fluid barrier heat exchanging plate opposite the vapor exchange face through the absorber and subsequently through the heat exchanger. Themore » absorption based heater can include a second plate with a condenser situated parallel to the fluid barrier heat exchanging plate and opposing the desorber for condensation of the refrigerant for additional heating of the process fluid.« less

Simulation of interior ballistics flows in a shock tube

NASA Astrophysics Data System (ADS)

Seiler, F.

1983-07-01

The flow in front of and behind a projectile was investigated in a interior ballistics shock tube simulator. Flow patterns and heat flow were examined for flows with and without gas leakage. The boundary layers behind the piston can clearly be shown by differential interferograms. The dependence of the heat flow into the measuring tube wall on the base form is smaller than the signal perturbations. Flow patterns show no appreciable effect of gas leakage on the flow behind the piston; strong flow effects arise in front of the piston. The same effects are shown by heat flow measurements. In case of gas leakage heat flows into the tube wall before the piston reaches the wall. In the slit between piston and wall a maximum heat flow is found. High temperature gradients, due to the fact that hot gases come closer to the tube wall than in the boundary layer flow behind the piston, lead to high thermal loading of the wall materials which can cause cracks.

Heat exchanger with transpired, highly porous fins

DOEpatents

Kutscher, Charles F.; Gawlik, Keith

2002-01-01

The heat exchanger includes a fin and tube assembly with increased heat transfer surface area positioned within a hollow chamber of a housing to provide effective heat transfer between a gas flowing within the hollow chamber and a fluid flowing in the fin and tube assembly. A fan is included to force a gas, such as air, to flow through the hollow chamber and through the fin and tube assembly. The fin and tube assembly comprises fluid conduits to direct the fluid through the heat exchanger, to prevent mixing with the gas, and to provide a heat transfer surface or pathway between the fluid and the gas. A heat transfer element is provided in the fin and tube assembly to provide extended heat transfer surfaces for the fluid conduits. The heat transfer element is corrugated to form fins between alternating ridges and grooves that define flow channels for directing the gas flow. The fins are fabricated from a thin, heat conductive material containing numerous orifices or pores for transpiring the gas out of the flow channel. The grooves are closed or only partially open so that all or substantially all of the gas is transpired through the fins so that heat is exchanged on the front and back surfaces of the fins and also within the interior of the orifices, thereby significantly increasing the available the heat transfer surface of the heat exchanger. The transpired fins also increase heat transfer effectiveness of the heat exchanger by increasing the heat transfer coefficient by disrupting boundary layer development on the fins and by establishing other beneficial gas flow patterns, all at desirable pressure drops.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sai K. Mylavarapu; Xiaodong Sun; Richard E. Glosup

In high-temperature gas-cooled reactors, such as a very high temperature reactor (VHTR), an intermediate heat exchanger (IHX) is required to efficiently transfer the core thermal output to a secondary fluid for electricity generation with an indirect power cycle and/or process heat applications. Currently, there is no proven high-temperature (750–800 °C or higher) compact heat exchanger technology for high-temperature reactor design concepts. In this study, printed circuit heat exchanger (PCHE), a potential IHX concept for high-temperature applications, has been investigated for their heat transfer and pressure drop characteristics under high operating temperatures and pressures. Two PCHEs, each having 10 hot andmore » 10 cold plates with 12 channels (semicircular cross-section) in each plate are fabricated using Alloy 617 plates and tested for their performance in a high-temperature helium test facility (HTHF). The PCHE inlet temperature and pressure were varied from 85 to 390 °C/1.0–2.7 MPa for the cold side and 208–790 °C/1.0–2.7 MPa for the hot side, respectively, while the mass flow rate of helium was varied from 15 to 49 kg/h. This range of mass flow rates corresponds to PCHE channel Reynolds numbers of 950 to 4100 for the cold side and 900 to 3900 for the hot side (corresponding to the laminar and laminar-to-turbulent transition flow regimes). The obtained experimental data have been analyzed for the pressure drop and heat transfer characteristics of the heat transfer surface of the PCHEs and compared with the available models and correlations in the literature. In addition, a numerical treatment of hydrodynamically developing and hydrodynamically fully-developed laminar flow through a semicircular duct is presented. Relations developed for determining the hydrodynamic entrance length in a semicircular duct and the friction factor (or pressure drop) in the hydrodynamic entry length region for laminar flow through a semicircular duct are given. Various hydrodynamic entrance region parameters, such as incremental pressure drop number, apparent Fanning friction factor, and hydrodynamic entrance length in a semicircular duct have been numerically estimated.« less

THORIUM DISPERSION IN BISMUTH

DOEpatents

Bryner, J.S.

1961-07-01

The growth of thorium bismutaide particles, which are formed when thorium is suspended in liquid bismuth, is inhibited when the liquid metal suspension is being flowed through a reactor and through a heat exchanger in sequence. It involves the addition of as little as 1 part by weight of tellurium to 100 parts of thorium. This addition is sufficient to inhibit particle growth and agglomeration.

Self-sustained flow oscillations and heat transfer in radial flow through co-rotating parallel disks

NASA Astrophysics Data System (ADS)

Mochizuki, S.; Inoue, T.

1990-03-01

An experimental study was conducted to determine the fluid flow and heat transfer characteristics in a passage formed by two parallel rotating disks. The local heat transfer coefficients along the disk radius were measured in detail and the flow patterns between the two rotating disks were visualized by using paraffin mist and a laser-light sheet. It was disclosed that: (1) the self-sustained laminar flow separation which is characteristic of the stationary disks still exists even when the disks are set in motion, giving significant influence to the heat transfer; (2) for small source flow Reynolds number, Re, and large rotational Reynolds number, Re(omega), rotating stall dominates the heat transfer; and (3) heat transfer for steady laminar flow occurs only when Re is less than 1200 and Re(omega) is less than 20.

Development of Naphthalene PLIF for Visualizing Ablation Products From a Space Capsule Heat Shield

NASA Technical Reports Server (NTRS)

Combs, C. S.; Clemens, N. T.; Danehy, P. M.

2014-01-01

The Orion Multi-Purpose Crew Vehicle (MPCV) will use an ablative heat shield. To better design this heat shield and others that will undergo planetary entry, an improved understanding of the ablation process would be beneficial. Here, a technique developed at The University of Texas at Austin that uses planar laser-induced fluorescence (PLIF) of a low-temperature sublimating ablator (naphthalene) to enable visualization of the ablation products in a hypersonic flow is applied. Although high-temperature ablation is difficult and expensive to recreate in a laboratory environment, low-temperature sublimation creates a limited physics problem that can be used to explore ablation-product transport in a hypersonic flow-field. In the current work, a subscale capsule reentry vehicle model with a solid naphthalene heat shield has been tested in a Mach 5 wind tunnel. The PLIF technique provides images of the spatial distribution of sublimated naphthalene in the heat-shield boundary layer, separated shear layer, and backshell recirculation region. Visualizations of the capsule shear layer using both naphthalene PLIF and Schlieren imaging compared favorably. PLIF images have shown high concentrations of naphthalene in the capsule separated flow region, intermittent turbulent structures on the heat shield surface, and interesting details of the capsule shear layer structure. It was shown that, in general, the capsule shear layer appears to be more unsteady at lower angels of attack. The PLIF images demonstrated that during a wind tunnel run, as the model heated up, the rate of naphthalene ablation increased, since the PLIF signal increased steadily over the course of a run. Additionally, the shear layer became increasingly unsteady over the course of a wind tunnel run, likely because of increased surface roughness but also possibly because of the increased blowing. Regions with a relatively low concentration of naphthalene were also identified in the capsule backshell recirculation region and are most likely the result of cross-flow-induced vortices on the capsule afterbody.

Heat flow in eastern Egypt - The thermal signature of a continental breakup

NASA Technical Reports Server (NTRS)

Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

1985-01-01

Data on the heat flow in eastern Egypt were collected to provide information related to the mode and the mechanism of the Red Sea opening. The data indicate a general increase in heat flow towards the Red Sea (75-100 mW/sq m in a zone within 40 km of the coast compared with 35-55 mW/sq m inland). Moderately high heat flow (about 70 mW/sq m) was found for the Gulf of Suez. Heat production data indicate that the coastal thermal anomaly is not primarily related to crustal radiogenic heat production. Possible causes of the anomaly (one of which could be a high mantle heat flow causing a lithospheric thinning centered beneath the Red Sea) are discussed.

L-H transitions driven by ion heating in scrape-off layer turbulence (SOLT) model simulations

NASA Astrophysics Data System (ADS)

Russell, D. A.; D'Ippolito, D. A.; Myra, J. R.

2015-11-01

The original SOLT model now includes the evolution of ion pressure consistent with drift-ordering. It is a two-dimensional, electrostatic reduced model wherein closure relations, obtained by integrating the equations along the B-field, model parallel physics that includes sheath-mediated current and heat flux in the scrape-off-layer and electron drift waves inside the separatrix. Low (L) and high (H) confinement regimes are observed in SOLT simulations, depending on the strength of an ion pressure (i.e., ion heating) source localized inside the separatrix: With increasing heating, particle and energy confinement times at first decrease in the L-mode then rise in the H-mode. The L-H transition is marked by distinct changes in sheared-flow profiles. The addition of ion pressure dynamics enables modeling the self-consistent interaction between the ion diamagnetic drift and the radial electric field (mean and zonal flows). The roles of these sheared flows in mediating the L-H transition are explored. A new diagnostic, based on the density correlation function, is applied to study blob velocities in different regimes. Work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-97ER54392.

Analyses of exergy efficiency for forced convection heat transfer in a tube with CNT nanofluid under laminar flow conditions

NASA Astrophysics Data System (ADS)

Hazbehian, Mohammad; Mohammadiun, Mohammad; Maddah, Heydar; Alizadeh, Mostafa

2017-05-01

In the present study, the theoretical and experimental results of the second law analysis on the performance of a uniform heat flux tube using are presented in the laminar flow regime. For this purpose, carbon nanotube/water nanofluids is considered as the base fluid. The experimental investigations were undertaken in the Reynolds number range from 800 to 2600, volume concentrations of 0.1-1 %. Results are verified with well-known correlations. The focus will be on the entrance region under the laminar flow conditions for SWCNT nanofluid. The results showed that the Nu number increased about 90-270 % with the enhancement of nanoparticles volume concentration compared to water. The enhancement was particularly significant in the entrance region. Based on the exergy analysis, the results show that exergetic heat transfer effectiveness is increased by 22-67 % employing nanofluids. The exergetic efficiency is increase with increase in nanoparticles concentration. On the other hand, exergy loss was reduced by 23-43 % employing nanofluids as a heat transfer medium with comparing to conventional fluid. In addition, the empirical correlation for exergetic efficiency has also been developed. The consequential results obtained from the correlation are found to be in good agreement with the experimental results within ±5 % variation.

Thaw flow control for liquid heat transport systems

DOEpatents

Kirpich, Aaron S.

1989-01-01

In a liquid metal heat transport system including a source of thaw heat for use in a space reactor power system, the thaw flow throttle or control comprises a fluid passage having forward and reverse flow sections and a partition having a plurality of bleed holes therein to enable fluid flow between the forward and reverse sections. The flow throttle is positioned in the system relatively far from the source of thaw heat.

Heat flow and near-surface radioactivity in the Australian continental crust

USGS Publications Warehouse

Sass, J.H.; Jaeger, J.C.; Munroe, Robert J.

1976-01-01

Heat-flow data have been obtained at 44 sites in various parts of Australia. These include seven sites from the old (~ 2500 m.y.) Precambrian shield of Western Australia, seventeen from the younger (~ 600- 2000 m.y.) Precambrian rocks of South Australia, the Northern Territory, and Queensland, and twenty within the eastern Paleozoic and younger rocks. Thirty of the sites are located where no previous heat-flow data existed, and the remainder provide significant extensions or refinements of areas previously studied. Where the holes studied penetrated the crystalline basement rocks, or where the latter rocks were exposed within a few kilometers of the holes, the upper crustal radiogenic heat production has been estimated based on gamma-ray spectrometric determinations of U, Th, and K abundances. Three heat-flow provinces are recognized in Australia based on the linear relation (q = q* + DA0 ) between heat flow q and surface radioactivity A0. New data from the Western Australian shield support earlier studies showing that heat flow is low to normal with values ranging from 0.7 to 1.2 hfu and with the majority of values less than 1.0 hfu, and the parameters q* = 0.63 hfu and 0 = 4.5 km determined previously were confirmed. Heat flow in the Proterozoic shield of central Australia is quite variable, with values ranging between about l and 3 hfu. This variability is attributed mainly to variations in near-surface crustal radioactivity. The parameters of the heat-flow line are q* = 0.64 hfu and 0 = 11.1 km and moderately high temperatures are predicted for the lower crust and upper mantle. Previous suggestions of a band of l ow- to - normal heat flow near the coast in eastern Australia were confirmed in some areas, but the zone is interrupted in at least one region (the Sydney Basin), where heat flow is about 2.0 hfu over a large area. The reduced heat flow, q*, in the Paleozoic intrusive rocks of eastern Australia varies from about 0.8 to 2.0 hfu . This variability might be related to thermal transients associated with Late Tertiary and younger volcanic and tectonic activity, even though the relation between heat-flow values and the age of volcanism is not a simple one. Parts of the high heat-flow area in the southeast might be exploitable for geothermal energy.

Auxiliary reactor for a hydrocarbon reforming system

DOEpatents

Clawson, Lawrence G.; Dorson, Matthew H.; Mitchell, William L.; Nowicki, Brian J.; Bentley, Jeffrey M.; Davis, Robert; Rumsey, Jennifer W.

2006-01-17

An auxiliary reactor for use with a reformer reactor having at least one reaction zone, and including a burner for burning fuel and creating a heated auxiliary reactor gas stream, and heat exchanger for transferring heat from auxiliary reactor gas stream and heat transfer medium, preferably two-phase water, to reformer reaction zone. Auxiliary reactor may include first cylindrical wall defining a chamber for burning fuel and creating a heated auxiliary reactor gas stream, the chamber having an inlet end, an outlet end, a second cylindrical wall surrounding first wall and a second annular chamber there between. The reactor being configured so heated auxiliary reactor gas flows out the outlet end and into and through second annular chamber and conduit which is disposed in second annular chamber, the conduit adapted to carry heat transfer medium and being connectable to reformer reaction zone for additional heat exchange.

Integrated Modeling Study of the Effects of the Magnetospheric Forcing on the Jovian Ionosphere-Thermosphere System

NASA Technical Reports Server (NTRS)

Bogan, Denis (Technical Monitor); Waite, J. Hunter

2005-01-01

The Jupiter Thermosphere General Circulation Model (JTGCM) calculates the global dynamical structure of Jupiter s thermosphere self-consistently with its global thermal structure and composition. The main heat source that drives the thermospheric flow is high-latitude Joule heating. A secondary source of heating is the auroral process of particle precipitation. Global simulations of Jovian thermospheric dynamics indicate strong neutral outflows from the auroral ovals with velocities up to approx.2 km/s and subsequent convergence and downwelling at the Jovian equator. Such circulation is shown to be an important process for transporting significant amounts of auroral energy t o equatorial latitudes and for regulating the global heat budget in a manner consistent with the high thermospheric temperatures observed by the Galileo probe. Adiabatic compression of the neutral atmosphere resulting from downward motion is an important source of equatorial heating (< 0.06 microbar). The adiabatic heating continues to dominate between 0.06 and 0.2 microbar, but with an addition of comparable heating due to horizontal advection induced by the meridional flow. Thermal conduction plays an important role in transporting heat down to lower altitudes (>0.2microbar) where it is balanced by the cooling associated with the wind transport processes. Interestingly, we find that radiative cooling caused by H3(+), CH4, and C2H2 emissions does not play a significant role in interpreting the Galileo temperature profile.

An Initial Multi-Domain Modeling of an Actively Cooled Structure

NASA Technical Reports Server (NTRS)

Steinthorsson, Erlendur

1997-01-01

A methodology for the simulation of turbine cooling flows is being developed. The methodology seeks to combine numerical techniques that optimize both accuracy and computational efficiency. Key components of the methodology include the use of multiblock grid systems for modeling complex geometries, and multigrid convergence acceleration for enhancing computational efficiency in highly resolved fluid flow simulations. The use of the methodology has been demonstrated in several turbo machinery flow and heat transfer studies. Ongoing and future work involves implementing additional turbulence models, improving computational efficiency, adding AMR.

Compressible Navier-Stokes equations: A study of leading edge effects

NASA Technical Reports Server (NTRS)

Hariharan, S. I.; Karbhari, P. R.

1987-01-01

A computational method is developed that allows numerical calculations of the time dependent compressible Navier-Stokes equations.The current results concern a study of flow past a semi-infinite flat plate.Flow develops from given inflow conditions upstream and passes over the flat plate to leave the computational domain without reflecting at the downstream boundary. Leading edge effects are included in this paper. In addition, specification of a heated region which gets convected with the flow is considered. The time history of this convection is obtained, and it exhibits a wave phenomena.

Heat flow, heat production, and crustal temperatures in the Archaean Bundelkhand craton, north-central India: Implications for thermal regime beneath the Indian shield

NASA Astrophysics Data System (ADS)

Podugu, Nagaraju; Ray, Labani; Singh, S. P.; Roy, Sukanta

2017-07-01

Heat flow and heat production data sets constrain the crustal thermal structure in the 2.5-3.5 Ga Bundelkhand craton, the oldest cratonic core in northern Indian shield, for the first time and allow comparisons with the southern Indian shield. Temperature measurements carried out in 10 boreholes at five sites in the craton, combined with systematic thermal conductivity measurements on major rock types, yield low heat flow in the range of 32-41 mW m-2, which is distinct from the generally high heat flow reported from other parts of the northern Indian shield. Radioelemental measurements on 243 samples of drill cores and outcrops reveal both large variability and high average heat production for the Neo-Archaean to Palaeo-Proterozoic granites (4.0 ± 2.1 (SD) μW m-3) relative to the Meso-Archaean tonalite-trondhjemite-granodiorite (TTG) gneisses (2.0 ± 1.0 (SD) μW m-3). On the basis of new heat flow and heat production data sets combined with available geological and geophysical information, a set of steady state, heat flow-crustal heat production models representative of varying crustal scenarios in the craton are envisaged. Mantle heat flow and Moho temperatures are found to be in the range of 12-22 mW m-2 and 290-420°C, respectively, not much different from those reported for the similar age Dharwar craton in southern India. This study reveals similar mantle thermal regimes across the northern and southern parts of the Indian shield, in spite of varying surface heat flow regimes, implying that much of the intraprovince and interprovince variations in the Indian shield are explained by variations in upper crustal heat production.

Simulation of hydrodynamics, temperature, and dissolved oxygen in Beaver Lake, Arkansas, 1994-1995

USGS Publications Warehouse

Haggard, Brian; Green, W. Reed

2002-01-01

The tailwaters of Beaver Lake and other White River reservoirs support a cold-water trout fishery of significant economic yield in northwestern Arkansas. The Arkansas Game and Fish Commission has requested an increase in existing minimum flows through the Beaver Lake dam to increase the amount of fishable waters downstream. Information is needed to assess the impact of additional minimum flows on temperature and dissolved-oxygen qualities of reservoir water above the dam and the release water. A two-dimensional, laterally averaged hydrodynamic, thermal and dissolved-oxygen model was developed and calibrated for Beaver Lake, Arkansas. The model simulates surface-water elevation, currents, heat transport and dissolved-oxygen dynamics. The model was developed to assess the impacts of proposed increases in minimum flows from 1.76 cubic meters per second (the existing minimum flow) to 3.85 cubic meters per second (the additional minimum flow). Simulations included assessing (1) the impact of additional minimum flows on tailwater temperature and dissolved-oxygen quality and (2) increasing initial water-surface elevation 0.5 meter and assessing the impact of additional minimum flow on tailwater temperatures and dissolved-oxygen concentrations. The additional minimum flow simulation (without increasing initial pool elevation) appeared to increase the water temperature (<0.9 degrees Celsius) and decrease dissolved oxygen concentration (<2.2 milligrams per liter) in the outflow discharge. Conversely, the additional minimum flow plus initial increase in pool elevation (0.5 meter) simulation appeared to decrease outflow water temperature (0.5 degrees Celsius) and increase dissolved oxygen concentration (<1.2 milligrams per liter) through time. However, results from both minimum flow scenarios for both water temperature and dissolved oxygen concentration were within the boundaries or similar to the error between measured and simulated water column profile values.

Advanced radiator concepts utilizing honeycomb panel heat pipes (stainless steel)

NASA Technical Reports Server (NTRS)

Fleischman, G. L.; Tanzer, H. J.

1985-01-01

The feasibility of fabricating and processing moderate temperature range heat pipes in a low mass honeycomb sandwich panel configuration for highly efficient radiator fins for the NASA space station was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts were evaluated within constraints dictated by existing manufacturing technology and equipment. Concepts evaluated include: type of material, material and panel thicknesses, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. In addition, the overall performance of the honeycomb panel heat pipe was evaluated analytically.

Method and apparatus for controlling accidental releases of tritium

DOEpatents

Galloway, T.R.

1980-04-01

An improvement is described in a tritium control system based on a catalytic oxidation reactor wherein accidental releases of tritium into room air are controlled by flooding the catalytic oxidation reactor with hydrogen when the tritium concentration in the room air exceeds a specified limit. The sudden flooding with hydrogen heats the catalyst to a high temperature within seconds, thereby greatly increasing the catalytic oxidation rate of tritium to tritiated water vapor. Thus, the catalyst is heated only when needed. In addition to the heating effect, the hydrogen flow also swamps the tritium and further reduces the tritium release. 1 fig.

Method and apparatus for controlling accidental releases of tritium

DOEpatents

Galloway, Terry R. [Berkeley, CA

1980-04-01

An improvement in a tritium control system based on a catalytic oxidation reactor wherein accidental releases of tritium into room air are controlled by flooding the catalytic oxidation reactor with hydrogen when the tritium concentration in the room air exceeds a specified limit. The sudden flooding with hydrogen heats the catalyst to a high temperature within seconds, thereby greatly increasing the catalytic oxidation rate of tritium to tritiated water vapor. Thus, the catalyst is heated only when needed. In addition to the heating effect, the hydrogen flow also swamps the tritium and further reduces the tritium release.

Feedwater temperature control methods and systems

DOEpatents

Moen, Stephan Craig; Noonan, Jack Patrick; Saha, Pradip

2014-04-22

A system for controlling the power level of a natural circulation boiling water nuclear reactor (NCBWR) is disclosed. The system, in accordance with an example embodiment of the present invention, may include a controller configured to control a power output level of the NCBWR by controlling a heating subsystem to adjust a temperature of feedwater flowing into an annulus of the NCBWR. The heating subsystem may include a steam diversion line configured to receive steam generated by a core of the NCBWR and a steam bypass valve configured to receive commands from the controller to control a flow of the steam in the steam diversion line, wherein the steam received by the steam diversion line has not passed through a turbine. Additional embodiments of the invention may include a feedwater bypass valve for controlling an amount of flow of the feedwater through a heater bypass line to the annulus.

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part II-experimental correlation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacharia, T.; David, S.A.; Vitek, J.M.

1989-12-01

In part I of the paper, the results of the heat flow and the fluid flow analysis were presented. Here, in Part II of the paper, predictions of the computational model are verified by comparing the numerically predicted and experimentally observed fusion zone size and shape. Stationary gas tungsten arc and laser beam welds were made on Type 304 stainless steel for different times to provide a variety of solidification conditions such as cooling rate and temperature gradient. Calculated temperatures and cooling rates are correlated with the experimentally observed fusion zone structure. In addition, the effect of sulfur on GTAmore » weld penetration was quantitatively evaluated by considering two heats of 304 stainless steel containing 90 and 240 ppm sulfur. Sulfur, as expected, increased the depth/width ratio by altering the surface tension gradient driven flow in the weld pool.« less

Redesigned Human Metabolic Simulator

NASA Technical Reports Server (NTRS)

Duffield, Bruce; Jeng, Frank; Lange, Kevin

2008-01-01

A design has been formulated for a proposed improved version of an apparatus that simulates atmospheric effects of human respiration by introducing controlled amounts of carbon dioxide, water vapor, and heat into the air. Denoted a human metabolic simulator (HMS), the apparatus is used for testing life-support equipment when human test subjects are not available. The prior version of the HMS, to be replaced, was designed to simulate the respiratory effects of as many as four persons. It exploits the catalytic combustion of methyl acetate, for which the respiratory quotient (the molar ratio of carbon dioxide produced to oxygen consumed) is very close to the human respiratory quotient of about 0.86. The design of the improved HMS provides for simulation of the respiratory effects of as many as eight persons at various levels of activity. The design would also increase safety by eliminating the use of combustion. The improved HMS (see figure) would include a computer that would exert overall control. The computer would calculate the required amounts of oxygen removal, carbon dioxide addition, water addition, and heat addition by use of empirical equations for metabolic profiles of respiration and heat. A blower would circulate air between the HMS and a chamber containing a life-support system to be tested. With the help of feedback from a mass flowmeter, the blower speed would be adjusted to regulate the rate of flow according to the number of persons to be simulated and to a temperature-regulation requirement (the air temperature would indirectly depend on the rate of flow, among other parameters). Oxygen would be removed from the circulating air by means of a commercially available molecular sieve configured as an oxygen concentrator. Oxygen, argon, and trace amounts of nitrogen would pass through a bed in the molecular sieve while carbon dioxide, the majority of nitrogen, and other trace gases would be trapped by the bed and subsequently returned to the chamber. If, as recommended, the oxygen concentrator were of a rotating twelve-bed design, then variations in the product stream could be made very small. Carbon dioxide would be added directly to the circulating air by simple injection from a supply tank. The rate of injection would be maintained at the required rate by use of a mass flowmeter/controller. In the same way, nitrogen would be added to make up for the small amount of nitrogen lost through the oxygen concentrator. Water vapor would be added to the circulating air by heating the corresponding required flow of water to steam in a heat exchanger. More heat, required to complete the simulation of the thermal effect of respiration, would be added through another heat exchanger. Heat would be supplied to both heat exchangers via a hot-oil loop.

In Depth Analysis of AVCOAT TPS Response to a Reentry Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Titov, E. V.; Kumar, Rakesh; Levin, D. A.

2011-05-20

Modeling of the high altitude portion of reentry vehicle trajectories with DSMC or statistical BGK solvers requires accurate evaluation of the boundary conditions at the ablating TPS surface. Presented in this article is a model which takes into account the complex ablation physics including the production of pyrolysis gases, and chemistry at the TPS surface. Since the ablation process is time dependent the modeling of the material response to the high energy reentry flow starts with the solution of the rarefied flow over the vehicle and then loosely couples with the material response. The objective of the present work ismore » to carry out conjugate thermal analysis by weakly coupling a flow solver to a material thermal response model. The latter model solves the one dimensional heat conduction equation accounting for the pyrolysis process that takes place in the reaction zone of an ablative thermal protection system (TPS) material. An estimate of the temperature range within which the pyrolysis reaction (decomposition and volatilization) takes place is obtained from Ref. [1]. The pyrolysis reaction results in the formation of char and the release of gases through the porous charred material. These gases remove additional amount of heat as they pass through the material, thus cooling the material (the process known as transpiration cooling). In the present work, we incorporate the transpiration cooling model in the material thermal response code in addition to the pyrolysis model. The flow in the boundary layer and in the vicinity of the TPS material is in the transitional flow regime. Therefore, we use a previously validated statistical BGK method to model the flow physics in the vicinity of the micro-cracks, since the BGK method allows simulations of flow at pressures higher than can be computed using DSMC.« less

Incorporating Water Boiling in the Numerical Modelling of Thermal Remediation by Electrical Resistance Heating

NASA Astrophysics Data System (ADS)

Molnar, I. L.; Krol, M.; Mumford, K. G.

2017-12-01

Developing numerical models for subsurface thermal remediation techniques - such as Electrical Resistive Heating (ERH) - that include multiphase processes such as in-situ water boiling, gas production and recovery has remained a significant challenge. These subsurface gas generation and recovery processes are driven by physical phenomena such as discrete and unstable gas (bubble) flow as well as water-gas phase mass transfer rates during bubble flow. Traditional approaches to multiphase flow modeling soil remain unable to accurately describe these phenomena. However, it has been demonstrated that Macroscopic Invasion Percolation (MIP) can successfully simulate discrete and unstable gas transport1. This has lead to the development of a coupled Electro Thermal-MIP Model2 (ET-MIP) capable of simulating multiple key processes in the thermal remediation and gas recovery process including: electrical heating of soil and groundwater, water flow, geological heterogeneity, heating-induced buoyant flow, water boiling, gas bubble generation and mobilization, contaminant mass transport and removal, and additional mechanisms such as bubble collapse in cooler regions. This study presents the first rigorous validation of a coupled ET-MIP model against two-dimensional water boiling and water/NAPL co-boiling experiments3. Once validated, the model was used to explore the impact of water and co-boiling events and subsequent gas generation and mobilization on ERH's ability to 1) generate, expand and mobilize gas at boiling and NAPL co-boiling temperatures, 2) efficiently strip contaminants from soil during both boiling and co-boiling. In addition, a quantification of the energy losses arising from steam generation during subsurface water boiling was examined with respect to its impact on the efficacy of thermal remediation. While this study specifically targets ERH, the study's focus on examining the fundamental mechanisms driving thermal remediation (e.g., water boiling) renders these results applicable to a wide range of thermal and gas-based remediation techniques. 1. Mumford, K. G., et al. (2010), Adv. Water Resour. 2010, 33 (4), 504-513. 2. Krol, M. M., et al. (2011), Adv. Water Resour. 2011, 34 (4), 537-549. 3. Hegele, P. R. and Mumford, K. G. Journal of Contaminant Hydrology 2014, 165, 24-36.

Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

NASA Astrophysics Data System (ADS)

Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

2017-10-01

The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

Constraints on The Coupled Thermal Evolution of the Earth's Core and Mantle, The Age of The Inner Core, And The Origin of the 186Os/188Os Core(?) Signal in Plume-Derived Lavas

NASA Astrophysics Data System (ADS)

Lassiter, J. C.

2005-12-01

Thermal and chemical interaction between the core and mantle has played a critical role in the thermal and chemical evolution of the Earth's interior. Outer core convection is driven by core cooling and inner core crystallization. Core/mantle heat transfer also buffers mantle potential temperature, resulting in slower rates of mantle cooling (~50-100 K/Ga) than would be predicted from the discrepancy between current rates of surface heat loss (~44 TW) and internal radioactive heat production (~20 TW). Core/mantle heat transfer may also generate thermal mantle plumes responsible for ocean island volcanic chains such as the Hawaiian Islands. Several studies suggest that mantle plumes, in addition to transporting heat from the core/mantle boundary, also carry a chemical signature of core/mantle interaction. Elevated 186Os/188Os ratios in lavas from Hawaii, Gorgona, and in the 2.8 Ga Kostomuksha komatiites have been interpreted as reflecting incorporation of an outer core component with high time-integrated Pt/Os and Re/Os ( Brandon et al., 1999, 2003; Puchtel et al., 2005). Preferential partitioning of Os relative to Re and Pt into the inner core during inner core growth may generate elevated Re/Os and Pt/Os ratios in the residual outer core. Because of the long half-life of 190Pt (the parent of 186Os, t1/2 = 489 Ga), an elevated 186Os/188Os outer core signature in plume lavas requires that inner core crystallization began early in Earth history, most likely prior to 3.5 Ga. This in turn requires low time-averaged core/mantle heat flow (<~2.5 TW) or large quantities of heat-producing elements in the core. Core/mantle heat flow may be estimated using boundary-layer theory, by measuring the heat transported in mantle plumes, by estimating the heat transported along the outer core adiabat, or by comparing the rates of heat production, surface heat loss, and secular cooling of the mantle. All of these independent methods suggest time-averaged core/mantle heat flow of ~5-14 TW. In the absence of heat-producing elements in the core, such high heat flow rates require an inner core younger than ~1 Ga and preclude the development of significant 186Os enrichment in the outer core. Experimental studies suggest that potassium may partition into Fe-S-O liquids during core formation. Radioactive decay of potassium in the core could provide an additional heat source and reconcile geophysical evidence for high core/mantle heat flow with apparent geochemical evidence for an ancient inner core. However, high concentrations of chalcophile elements such as Cu in the mantle are inconsistent with significant segregation of a S-rich liquid during core formation, precluding K partitioning into the core by this mechanism. Furthermore, core formation scenarios that would lead to high K content in the core (e.g., core formation prior to terrestrial volatile depletion) also result in high core Pb concentrations. Core/mantle interaction would then produce strong negative correlations between 186Os/188Os and 207Pb/204Pb ratios, but such correlations are not observed. In summary, elevated 186Os/188Os ratios in some plume-derived lavas are unlikely to reflect core/mantle interaction because the inner core is too young for this isotopic signature to have developed in the outer core. Melt generation from pyroxenite or fractionation of PGEs between sulfide melts and monosulfide solid solutions provide alternative mechanisms for generating ancient mantle reservoirs with elevated Pt/Os and 186Os/188Os.

Heat flow in the SAFOD pilot hole and implications for the strength of the San Andreas Fault

USGS Publications Warehouse

Williams, C.F.; Grubb, F.V.; Galanis, S.P.

2004-01-01

Detailed thermal measurements have been acquired in the 2.2-km-deep SAFOD pilot hole, located 1.8 km west of the SAF near Parkfield, California. Heat flow from the basement section of the borehole (770 to 2160 m) is 91 mW m-2, higher than the published 74 mW m -2 average for the Parkfield area. Within the resolution of the measurements, heat flow is constant across faults that intersect the borehole, suggesting that fluid flow does not alter the conductive thermal regime. Reanalysis of regional heat flow reveals an increase in heat flow along the SAF northwest of Parkfield. This transition corresponds to a shallowing base of seismicity and a change in fault behavior near the northern terminus of the M6 1966 Parkfield earthquake rupture. The persistence of elevated heat flow in the Coast Ranges to the west appears to rule out frictional heating on the SAF as the source of the SAFOD value.

Measurement and simulation of thermoelectric efficiency for single leg

NASA Astrophysics Data System (ADS)

Hu, Xiaokai; Yamamoto, Atsushi; Ohta, Michihiro; Nishiate, Hirotaka

2015-04-01

Thermoelectric efficiency measurements were carried out on n-type bismuth telluride legs with the hot-side temperature at 100 and 150 °C. The electric power and heat flow were measured individually. Water coolant was utilized to maintain the cold-side temperature and to measure heat flow out of the cold side. Leg length and vacuum pressure were studied in terms of temperature difference across the leg, open-circuit voltage, internal resistance, and heat flow. Finite-element simulation on thermoelectric generation was performed in COMSOL Multiphysics, by inputting two-side temperatures and thermoelectric material properties. The open-circuit voltage and resistance were in good agreement between the measurement and simulation. Much larger heat flows were found in measurements, since they were comprised of conductive, convective, and radiative contributions. Parasitic heat flow was measured in the absence of bismuth telluride leg, and the conductive heat flow was then available. Finally, the maximum thermoelectric efficiency was derived in accordance with the electric power and the conductive heat flow.

Numerical Simulation of Wall Heat Load in Combustor Flow

NASA Astrophysics Data System (ADS)

Panara, D.; Hase, M.; Krebs, W.; Noll, B.

2007-09-01

Due to the major mechanism of NOx generation, there is generally a temperature trade off between improved cycle efficiency, material constraints and low NOx emission. The cycle efficiency is proportional to the highest cycle temperature, but unfortunately also the NOx production increases with increasing combustion temperature. For this reason, the modern combustion chamber design has been oriented towards lean premixed combustion system and more and more attention must be focused on the cooling air management. The challenge is to ensure sufficiently low temperature of the combustion liner with very low amount of film or effusion cooling air. Correct numerical prediction of temperature fields and wall heat load are therefore of critical interest in the modern combustion chamber design. Moreover, lean combustion technology has shown the appearance of thermo-acoustic instabilities which have to be taken into account in the simulation and, more in general, in the design of reliable combustion systems. In this framework, the present investigation addresses the capability of a commercial multiphysics code (ANSYS CFX) to correctly predict the wall heat load and the core flow temperature field in a scaled power generation combustion chamber with a simplified ceramic liner. Comparison are made with the experimental results from the ITS test rig at the University of Karlsruhe [1] and with a previous numerical campaign from [2]. In addition the effect of flow unsteadyness on the wall heat load is discussed showing some limitations of the traditional steady state flow thermal design.

Origin and dynamics of emission line clouds in cooling flow environments

NASA Technical Reports Server (NTRS)

Loewenstein, Michael

1990-01-01

The author suggests that since clouds are born co-moving in a turbulent intra-cluster medium (ICM), the allowed parameter space can now be opened up to a more acceptable range. Large-scale motions can be driven in the central parts of cooling flows by a number of mechanisms including the motion of the central and other galaxies, and the dissipation of advected, focussed rotational and magnetic energy. In addition to the velocity width paradox, two other paradoxes (Heckman et al. 1989) can be solved if the ICM is turbulent. Firstly, the heating source for the emission line regions has always been puzzling - line luminosities are extremely high for a given (optical or radio) galaxy luminosity compared to those in non-cooling flow galaxies, therefore a mechanism peculiar to cooling flows must be at work. However most, if not all, previously suggested heating mechanisms either fail to provide enough ionization or give the wrong line ratios, or both. The kinetic energy in the turbulence provides a natural energy source if it can be efficiently converted to cloud heat. Researchers suggest that this can be done via magneto-hydrodynamic waves through plasma slip. Secondly, while the x ray observations indicate extended mass deposition, the optical line emission is more centrally concentrated. Since many of the turbulence-inducing mechanisms are strongest in the central regions of the ICM, so is the method of heating. In other words material is dropping out everywhere but only being lit up in the center.

Map of Io Volcanic Heat Flow

NASA Image and Video Library

2015-09-15

This frame from an animation shows Jupiter volcanic moon Io as seen by NASA Voyager and Galileo spacecraft (at left) and the pattern of heat flow from 242 active volcanoes (at right). The red and yellow areas are places where local heat flow is greatest -- the result of magma erupting from Io's molten interior onto the surface. The map is the result of analyzing decades of observations from spacecraft and ground-based telescopes. It shows Io's usual volcanic thermal emission, excluding the occasional massive but transient "outburst" eruption; in other words, this is what Io looks like most of the time. This heat flow map will be used to test models of interior heating. The map shows that areas of enhanced volcanic heat flow are not necessarily correlated with the number of volcanoes in a particular region and are poorly correlated with expected patterns of heat flow from current models of tidal heating -- something that is yet to be explained. This research is published in association with a 2015 paper in the journal Icarus by A. Davies et al., titled "Map of Io's Volcanic Heat Flow," (http://dx.doi.org/10.1016/j.icarus.2015.08.003.) http://photojournal.jpl.nasa.gov/catalog/PIA19655

Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.

PubMed

Zhou, Zhanru; Fang, Xiande; Li, Dingkun

2013-01-01

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.

Evaluation of Correlations of Flow Boiling Heat Transfer of R22 in Horizontal Channels

PubMed Central

Fang, Xiande; Li, Dingkun

2013-01-01

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels. PMID:23956695

Thermal Models of the Ocean Floor: from Wegener to Cerro Prieto

NASA Astrophysics Data System (ADS)

Sclater, J. G.; Negrete-Aranda, R.

2017-12-01

Wegener (1925) argued that hot rock could explain the shallower depths of ridges in the center of the Atlantic Ocean. Hess (1963) proposed that the intrusion of molten rock occurred at a world encircling mid-ocean ridge system. However, he accounted for the elevation of the ridges by the formation of serpentinite and thermal convection. Langseth et al. (1966) provided the major advance by using a 100 km thick plate to argue such a concept could not explain the depth, heat flow versus distance relations. They had the correct model but misinterpreted the data. Reformulating theoretically, McKenzie (1967) created the generally accepted thermal model for the ocean floor. Unfortunately, in attempting to match erroneously low heat flow data, he used a 50 km thick plate. Addition of the effect of water and the realization of the importance of advective flow, enabled various groups to create thermal plate models that accounted for the heat flow and depth age relations. From this came the understanding of hydrothermal circulation in the oceanic crust, the thermal boundary layer concept of the oceanic plate and the realization that all thermal models differed only in the way the different groups had chosen to analyze the data. During the past 40 years many have applied similar concepts to continental margins: (1) Measurement of subsidence of the Atlantic margin, continental stretching and a Time Temperature, Depth and Maturation analysis of continental basins have created the field of Basin Analysis; (2) Changes in heat flow at ocean continent boundaries have determined the position of the transition and (3) In attempting to examine the ocean continent transition process in the northernmost basin of the Gulf of California, Neumann et al (in press) observed conductive heat flow values greater than 0.75 Watts, at a depth of < 150 m, along a 10 km section of a profile across the southern extension of the Cerro Prieto fault. The magnitude of these values overwhelms local environmental effects and indicates a very large thermal output. Their full potential depends upon the amount of advective flow. Whatever the case, these measurements have opened up shallow continental margins as a new area for geothermic investigation.

Chitosan-magnesium aluminum silicate composite dispersions: characterization of rheology, flocculate size and zeta potential.

PubMed

Khunawattanakul, Wanwisa; Puttipipatkhachorn, Satit; Rades, Thomas; Pongjanyakul, Thaned

2008-03-03

Composite dispersions of chitosan (CS), a positively charged polymer, and magnesium aluminum silicate (MAS), a negatively charged clay, were prepared and rheology, flocculate size and zeta potential of the CS-MAS dispersions were investigated. High and low molecular weights of CS (HCS and LCS, respectively) were used in this study. Moreover, the effects of heat treatment at 60 degrees C on the characteristics of the CS-MAS dispersions and the zeta potential of MAS upon addition of CS at different pHs were examined. Incorporation of MAS into CS dispersions caused an increase in viscosity and a shift of CS flow type from Newtonian to pseudoplastic flow with thixotropic properties. Heat treatment brought about a significant decrease in viscosity and hysteresis area of the composite dispersions. Microscopic studies showed that flocculation of MAS occurred after mixing with CS. The size and polydispersity index of the HCS-MAS flocculate were greater than those of the LCS-MAS flocculate. However, a narrower size distribution and the smaller size of the HCS-MAS flocculate were found after heating at 60 degrees C. Zeta potentials of the CS-MAS flocculates were positive and slightly increased with increasing MAS content. In the zeta potential studies, the negative charge of the MAS could be neutralized by the addition of CS. Increasing the pH and molecular weight of CS resulted in higher CS concentrations required to neutralize the charge of MAS. These findings suggest that the electrostatic interaction between CS and MAS caused a change in flow behavior and flocculation of the composite dispersions, depending on the molecular weight of CS. Heat treatment affected the rheological properties and the flocculate size of the composite dispersions. Moreover, pH of medium and molecular weight of CS influence the zeta potential of MAS.

Acute vascular effects of carbonated warm water lower leg immersion in healthy young adults.

PubMed

Ogoh, Shigehiko; Nagaoka, Ryohei; Mizuno, Takamasa; Kimura, Shohei; Shidahara, Yasuhiro; Ishii, Tomomi; Kudoh, Michinari; Iwamoto, Erika

2016-12-01

Endothelial dysfunction is associated with increased cardiovascular mortality and morbidity; however, this dysfunction may be ameliorated by several therapies. For example, it has been reported that heat-induced increases in blood flow and shear stress enhance endothelium-mediated vasodilator function. Under these backgrounds, we expect that carbon dioxide (CO 2 )-rich water-induced increase in skin blood flow improves endothelium-mediated vasodilation with less heat stress. To test our hypothesis, we measured flow-mediated dilation (FMD) before and after acute immersion of the lower legs and feet in mild warm (38°C) normal or CO 2 -rich tap water (1000 ppm) for 20 min in 12 subjects. Acute immersion of the lower legs and feet in mild warm CO 2 -rich water increased FMD (P < 0.01) despite the lack of change in this parameter upon mild warm normal water immersion. In addition, FMD was positively correlated with change in skin blood flow regardless of conditions (P < 0.01), indicating that an increase in skin blood flow improves endothelial-mediated vasodilator function. Importantly, the temperature of normal tap water must reach approximately 43°C to achieve the same skin blood flow level as that obtained during mild warm CO 2 -rich water immersion (38°C). These findings suggest that CO 2 -rich water-induced large increases in skin blood flow may improve endothelial-mediated vasodilator function while causing less heat stress. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Utilization of Additive Manufacturing for Aerospace Heat Exchangers

DTIC Science & Technology

2016-02-29

is made up of flat plates that are layered on top of each other creating air passages in between the plates where the hot liquid and cold liquid flow...electron beam- based) for two-dimensional scanning of the heat source on the powder layer , stages that decrease the build plate and increase the powder...build plate and result in uneven coating of subsequent powder layers or complete failure of the system to recoat. The perturbations in recoater

Effects of Hot Streak Shape on Rotor Heating in a High-Subsonic Single-Stage Turbine

NASA Technical Reports Server (NTRS)

Dorney, Daniel J.; Gundy-Burlet, Karen L.; Norvig, Peter (Technical Monitor)

1999-01-01

Experimental data have shown that combustor temperature non-uniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location (clocking) of the hot streak relative to the first-stage vane airfoils can be used to minimize the adverse effects of the hot streak. The effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have also been evaluated. In the present investigation, three-dimensional unsteady Navier-Stokes simulations have been performed for a single-stage high-pressure turbine operating in high subsonic flow. In addition to a simulation of the baseline turbine, simulations have been performed for circular and elliptical hot streaks of varying sizes in an effort to represent different combustor designs. The predicted results for the baseline simulation show good agreement with the available experimental data. The results of the hot streak simulations indicate: that a) elliptical hot streaks mix more rapidly than circular hot streaks, b) for small hot streak surface area the average rotor temperature is not a strong function of hot streak temperature ratio or shape, and c) hot streaks with larger surface area interact with the secondary flows at the rotor hub endwall, generating an additional high temperature region.

Effects of heat exchanger tubes on hydrodynamics and CO 2 capture of a sorbent-based fluidized bed reactor

DOE PAGES

Lai, Canhai; Xu, Zhijie; Li, Tingwen; ...

2017-08-05

In virtual design and scale up of pilot-scale carbon capture systems, the coupled reactive multiphase flow problem must be solved to predict the adsorber's performance and capture efficiency under various operation conditions. This paper focuses on the detailed computational fluid dynamics (CFD) modeling of a pilot-scale fluidized bed adsorber equipped with vertical cooling tubes. Multiphase Flow with Interphase eXchanges (MFiX), an open-source multiphase flow CFD solver, is used for the simulations with custom code to simulate the chemical reactions and filtered sub-grid models to capture the effect of the unresolved details in the coarser mesh for simulations with reasonable accuracymore » and manageable computational effort. Previously developed filtered models for horizontal cylinder drag, heat transfer, and reaction kinetics have been modified to derive the 2D filtered models representing vertical cylinders in the coarse-grid CFD simulations. The effects of the heat exchanger configurations (i.e., horizontal or vertical tubes) on the adsorber's hydrodynamics and CO 2 capture performance are then examined. A one-dimensional three-region process model is briefly introduced for comparison purpose. The CFD model matches reasonably well with the process model while provides additional information about the flow field that is not available with the process model.« less

TEM heat transport and fluctuations in the HSX stellarator: experiments and comparison with gyrokinetic simulation

NASA Astrophysics Data System (ADS)

Smoniewski, J.; Faber, B. J.; Sánchez, E.; Calvo, I.; Pueschel, M. J.; Likin, K. M.; Deng, C. B.; Talmadge, J. N.

2017-10-01

The Helically Symmetric eXperiment (HSX) has demonstrated reduced neoclassical transport in the plasma core with quasi-symmetry [Lore Thesis 2010], while outside this region the electron thermal diffusivity is well above the neoclassical level, likely due to the Trapped Electron Mode (TEM) [Weir PoP 2015, Faber PoP 2015]. We compare gyrokinetic simulations of the TEM to experimental heat flux and density fluctuation measurements for two configurations: Quasi-Helical Symmetry (QHS) and broken symmetry (Mirror). Both experiment and simulation show that the heat flux for Mirror is larger than for QHS by about a factor of two. Initial interferometer measurements provide evidence that density-gradient-driven TEMs are driving turbulence. Calculations of the collisionless damping of zonal flows provide another perspective into the difference between geometries. Similar to other stellarators [Monreal PPCF 2016], the zonal flow residual goes to zero at long wavelengths in both configurations. Additionally, the very short time decay of the zonal flow due to neoclassical polarization is constant between configurations. However, the collisionless damping time is longer and the zonal flow oscillation frequency is smaller in QHS than Mirror, consistent with reduced radial particle drifts. Work supported by the US DOE under Grant DE-FG02-93ER54222.

Plasma flow measurements in the Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) and comparison with B2.5-Eirene modeling

NASA Astrophysics Data System (ADS)

Kafle, N.; Owen, L. W.; Caneses, J. F.; Biewer, T. M.; Caughman, J. B. O.; Donovan, D. C.; Goulding, R. H.; Rapp, J.

2018-05-01

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory is a linear plasma device that combines a helicon plasma source with additional microwave and radio frequency heating to deliver high plasma heat and particle fluxes to a target. Double Langmuir probes and Thomson scattering are being used to measure local electron temperature and density at various radial and axial locations. A recently constructed Mach-double probe provides the added capability of simultaneously measuring electron temperatures ( T e), electron densities ( n e), and Mach numbers (M). With this diagnostic, it is possible to infer the plasma flow, particle flux, and heat flux at different locations along the plasma column in Proto-MPEX. Preliminary results show Mach numbers of 0.5 (towards the dump plate) and 1.0 (towards the target plate) downstream from the helicon source, and a stagnation point (no flow) near the source for the case where the peak magnetic field was 1.3 T. Measurements of particle flow and ne and Te profiles are discussed. The extensive coverage provided by these diagnostics permits data-constrained B2.5-Eirene modeling of the entire plasma column, and comparison with results of modeling in the high-density helicon plasmas will be presented.

Development of an Efficient Meso- scale Multi-phase Flow Solver in Nuclear Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Taehun

2015-10-20

The proposed research aims at formulating a predictive high-order Lattice Boltzmann Equation for multi-phase flows relevant to nuclear energy related application - namely, saturated and sub-cooled boiling in reactors, and liquid- liquid mixing and extraction for fuel cycle separation. An efficient flow solver will be developed based on the Finite Element based Lattice Boltzmann Method (FE- LBM), accounting for phase-change heat transfer and capable of treating multiple phases over length scales from the submicron to the meter. A thermal LBM will be developed in order to handle adjustable Prandtl number, arbitrary specific heat ratio, a wide range of temperature variations,more » better numerical stability during liquid-vapor phase change, and full thermo-hydrodynamic consistency. Two-phase FE-LBM will be extended to liquid–liquid–gas multi-phase flows for application to high-fidelity simulations building up from the meso-scale up to the equipment sub-component scale. While several relevant applications exist, the initial applications for demonstration of the efficient methods to be developed as part of this project include numerical investigations of Critical Heat Flux (CHF) phenomena in nuclear reactor fuel bundles, and liquid-liquid mixing and interfacial area generation for liquid-liquid separations. In addition, targeted experiments will be conducted for validation of this advanced multi-phase model.« less

Large eddy simulations of time-dependent and buoyancy-driven channel flows

NASA Technical Reports Server (NTRS)

Cabot, William H.

1993-01-01

The primary goal of this work has been to assess the performance of the dynamic SGS model in the large eddy simulation (LES) of channel flows in a variety of situations, viz., in temporal development of channel flow turned by a transverse pressure gradient and especially in buoyancy-driven turbulent flows such as Rayleigh-Benard and internally heated channel convection. For buoyancy-driven flows, there are additional buoyant terms that are possible in the base models, and one objective has been to determine if the dynamic SGS model results are sensitive to such terms. The ultimate goal is to determine the minimal base model needed in the dynamic SGS model to provide accurate results in flows with more complicated physical features. In addition, a program of direct numerical simulation (DNS) of fully compressible channel convection has been undertaken to determine stratification and compressibility effects. These simulations are intended to provide a comparative base for performing the LES of compressible (or highly stratified, pseudo-compressible) convection at high Reynolds number in the future.

Numerical study of heat transfer characteristics in BOG heat exchanger

NASA Astrophysics Data System (ADS)

Yan, Yan; Pfotenhauer, John M.; Miller, Franklin; Ni, Zhonghua; Zhi, Xiaoqin

2016-12-01

In this study, a numerical study of turbulent flow and the heat transfer process in a boil-off liquefied natural gas (BOG) heat exchanger was performed. Finite volume computational fluid dynamics and the k - ω based shear stress transport model were applied to simulate thermal flow of BOG and ethylene glycol in a full-sized 3D tubular heat exchanger. The simulation model has been validated and compared with the engineering specification data from its supplier. In order to investigate thermal characteristics of the heat exchanger, velocity, temperature, heat flux and thermal response were studied under different mass flowrates in the shell-side. The shell-side flow pattern is mostly determined by viscous forces, which lead to a small velocity and low temperature buffer area in the bottom-right corner of the heat exchanger. Changing the shell-side mass flowrate could result in different distributions of the shell-side flow. However, the distribution in the BOG will remain in a relatively stable pattern. Heat flux increases along with the shell-side mass flowrate, but the increase is not linear. The ratio of increased heat flux to the mass flow interval is superior at lower mass flow conditions, and the threshold mass flow for stable working conditions is defined as greater than 0.41 kg/s.

Heat exchanger with oscillating flow

NASA Technical Reports Server (NTRS)

Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)

1992-01-01

Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators, or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

Heat exchanger with oscillating flow

NASA Technical Reports Server (NTRS)

Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)

1993-01-01

Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

Experimental and Numerical Analysis of Air Flow, Heat Transfer and Thermal Comfort in Buildings with Different Heating Systems

NASA Astrophysics Data System (ADS)

Sabanskis, A.; Virbulis, J.

2016-04-01

Monitoring of temperature, humidity and air flow velocity is performed in 5 experimental buildings with the inner size of 3×3×3 m3 located in Riga, Latvia. The buildings are equipped with different heating systems, such as an air-air heat pump, air-water heat pump, capillary heating mat on the ceiling and electric heater. Numerical simulation of air flow and heat transfer by convection, conduction and radiation is carried out using OpenFOAM software and compared with experimental data. Results are analysed regarding the temperature and air flow distribution as well as thermal comfort.

Closure models for transitional blunt-body flows

NASA Astrophysics Data System (ADS)

Nance, Robert Paul

1998-12-01

A mean-flow modeling approach is proposed for the prediction of high-speed blunt-body wake flows undergoing transition to turbulence. This method couples the k- /zeta (Enstrophy) compressible turbulence model with a procedure for characterizing non-turbulent fluctuations upstream of transition. Two different instability mechanisms are examined in this study. In the first model, transition is brought about by streamwise disturbance modes, whereas the second mechanism considers instabilities in the free shear layer associated with the wake flow. An important feature of this combined approach is the ability to specify or predict the location of transition onset. Solutions obtained using the new approach are presented for a variety of perfect-gas hypersonic flows over blunt- cone configurations. These results are shown to provide better agreement with experimental heating data than earlier laminar predictions by other researchers. In addition, it is demonstrated that the free-shear-layer instability mechanism is superior to the streamwise mechanism in terms of comparisons with heating measurements. The favorable comparisons are a strong indication that transition to turbulence is indeed present in the flowfields considered. They also show that the present method is a useful predictive tool for transitional blunt-body wake flows.

Aerodynamic pressure and heating-rate distributions in tile gaps around chine regions with pressure gradients at a Mach number of 6.6

NASA Technical Reports Server (NTRS)

Hunt, L. Roane; Notestine, Kristopher K.

1990-01-01

Surface and gap pressures and heating-rate distributions were obtained for simulated Thermal Protection System (TPS) tile arrays on the curved surface test apparatus of the Langley 8-Foot High Temperature Tunnel at Mach 6.6. The results indicated that the chine gap pressures varied inversely with gap width because larger gap widths allowed greater venting from the gap to the lower model side pressures. Lower gap pressures caused greater flow ingress from the surface and increased gap heating. Generally, gap heating was greater in the longitudinal gaps than in the circumferential gaps. Gap heating decreased with increasing gap depth. Circumferential gap heating at the mid-depth was generally less than about 10 percent of the external surface value. Gap heating was most severe at local T-gap junctions and tile-to-tile forward-facing steps that caused the greatest heating from flow impingement. The use of flow stoppers at discrete locations reduced heating from flow impingement. The use of flow stoppers at discrete locations reduced heating in most gaps but increased heating in others. Limited use of flow stoppers or gap filler in longitudinal gaps could reduce gap heating in open circumferential gaps in regions of high surface pressure gradients.

Heating and cooling system for an on-board gas adsorbent storage vessel

DOEpatents

Tamburello, David A.; Anton, Donald L.; Hardy, Bruce J.; Corgnale, Claudio

2017-06-20

In one aspect, a system for controlling the temperature within a gas adsorbent storage vessel of a vehicle may include an air conditioning system forming a continuous flow loop of heat exchange fluid that is cycled between a heated flow and a cooled flow. The system may also include at least one fluid by-pass line extending at least partially within the gas adsorbent storage vessel. The fluid by-pass line(s) may be configured to receive a by-pass flow including at least a portion of the heated flow or the cooled flow of the heat exchange fluid at one or more input locations and expel the by-pass flow back into the continuous flow loop at one or more output locations, wherein the by-pass flow is directed through the gas adsorbent storage vessel via the by-pass line(s) so as to adjust an internal temperature within the gas adsorbent storage vessel.

The Characteristics of Heat Flow in the Ryukyu Trench-Arc-Basin System: Constraints on Thermal Structure and Evolution of the Okinawa Trough

NASA Astrophysics Data System (ADS)

Zhang, L.

2017-12-01

Heat flow is an important constraint to study the thermal structure and evolution in modeling experiments. Based on the surface heat flow map and recent geochemistry results, a 2D transient heat conduction-advection model is used to investigate how the effects of sedimentation rate, magmatic intrusion, extension duration and rate on the surface heat flow distribution of the Okinawa Trough. Surface heat flow distribution map is interpolated based on a data set with 664 measurements in the Ryukyu trench-arc-basin system. The map shows an obviously correspondence between heat flows and tectonic zones, characterized by belts in E-W and blocks in S-N. The heat flow is extremely high and variable in the central Okinawa Trough (COT). The lowest heat values are distributed in the northwest of West Philippine Sea near the Ryukyu Trench. This phenomenon is likely related to increasing hydrothermal circulation of cold water into the upper portion of the incoming plate because of bend-faulting and little sediment coverage. Simulation results show that (1) High sedimentation rate can reduce heat flow by 30-35 % in the southern OT. (2) The sedimentation-corrected heat flow indicates that mantle upwelling occurred in the whole OT. The isotherm of 1000°C reaches to the depth of 19 km in the axil of the COT after 10 Ma. (3) The heat flow can be improved drastically by dyke intrusion along normal faults, but subsequent decreases rapidly about 15% after 0.1 Ma, which indicates the age of dyke intrusion under the Iheya area is younger than 0.5 Ma, and the depth is shallower than 2 km. Moreover, the magma fluid upward migrated along the magma conduits is required for the extremely high heat flow and its Darcy velocity can reach to 9 cm/yr. Based on the distribution of heat flow, we suggest that there is a different evolution model between the central- northern OT and the southern. The time of rifting in the NOT-COT began at 10 Ma with the mean rate of 0.4 cm/yr, while the rifting of the SOT started from 6 Ma with higher rate of 0.6 cm/yr.

Laser heating of aqueous samples on a micro-optical-electro-mechanical system

DOEpatents

Beer, Neil Reginald; Kennedy, Ian

2013-12-17

A system of heating a sample on a microchip includes the steps of providing a microchannel flow channel in the microchip; positioning the sample within the microchannel flow channel, providing a laser that directs a laser beam onto the sample for heating the sample; providing the microchannel flow channel with a wall section that receives the laser beam and enables the laser beam to pass through wall section of the microchannel flow channel without being appreciably heated by the laser beam; and providing a carrier fluid in the microchannel flow channel that moves the sample in the microchannel flow channel wherein the carrier fluid is not appreciably heated by the laser beam.

Laser heating of aqueous samples on a micro-optical-electro-mechanical system

DOEpatents

Beer, Neil Reginald; Kennedy, Ian

2013-02-05

A system of heating a sample on a microchip includes the steps of providing a microchannel flow channel in the microchip; positioning the sample within the microchannel flow channel, providing a laser that directs a laser beam onto the sample for heating the sample; providing the microchannel flow channel with a wall section that receives the laser beam and enables the laser beam to pass through wall section of the microchannel flow channel without being appreciably heated by the laser beam; and providing a carrier fluid in the microchannel flow channel that moves the sample in the microchannel flow channel wherein the carrier fluid is not appreciably heated by the laser beam.

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part I - theoretical analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacharia, T.; David, S.A.; Vitek, J.M.

1989-12-01

A computational and experimental study was carried out to quantitatively understand the influence of the heat flow and the fluid flow in the transient development of the weld pool during gas tungsten arc (GTA) and laser beam welding of Type 304 stainless steel. Stationary gas tungsten arc and laser beam welds were made on two heats of Type 304 austenitic stainless steels containing 90 ppm sulfur and 240 ppm sulfur. A transient heat transfer model was utilized to simulate the heat flow and fluid flow in the weld pool. In this paper, the results of the heat flow and fluidmore » flow analysis are presented.« less

Polyimide processing additives

NASA Technical Reports Server (NTRS)

Fletcher, James C. (Inventor); Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)

1992-01-01

A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.

Polyimide processing additives

NASA Technical Reports Server (NTRS)

Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)

1993-01-01

A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of the additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.

A mechanistic model of heat transfer for gas-liquid flow in vertical wellbore annuli.

PubMed

Yin, Bang-Tang; Li, Xiang-Fang; Liu, Gang

2018-01-01

The most prominent aspect of multiphase flow is the variation in the physical distribution of the phases in the flow conduit known as the flow pattern. Several different flow patterns can exist under different flow conditions which have significant effects on liquid holdup, pressure gradient and heat transfer. Gas-liquid two-phase flow in an annulus can be found in a variety of practical situations. In high rate oil and gas production, it may be beneficial to flow fluids vertically through the annulus configuration between well tubing and casing. The flow patterns in annuli are different from pipe flow. There are both casing and tubing liquid films in slug flow and annular flow in the annulus. Multiphase heat transfer depends on the hydrodynamic behavior of the flow. There are very limited research results that can be found in the open literature for multiphase heat transfer in wellbore annuli. A mechanistic model of multiphase heat transfer is developed for different flow patterns of upward gas-liquid flow in vertical annuli. The required local flow parameters are predicted by use of the hydraulic model of steady-state multiphase flow in wellbore annuli recently developed by Yin et al. The modified heat-transfer model for single gas or liquid flow is verified by comparison with Manabe's experimental results. For different flow patterns, it is compared with modified unified Zhang et al. model based on representative diameters.

Turbomachinery for Low-to-High Mach Number Flight

NASA Technical Reports Server (NTRS)

Tan, Choon S.; Shah, Parthiv N.

2004-01-01

The thrust capability of turbojet cycles is reduced at high flight Mach number (3+) by the increase in inlet stagnation temperature. The 'hot section' temperature limit imposed by materials technology sets the maximum heat addition and, hence, sets the maximum flight Mach number of the operating envelope. Compressor pre-cooling, either via a heat exchanger or mass-injection, has been suggested as a means to reduce compressor inlet temperature and increase mass flow capability, thereby increasing thrust. To date, however, no research has looked at compressor cooling (i.e., using a compressor both to perform work on the gas path air and extract heat from it simultaneously). We wish to assess the feasibility of this novel concept for use in low-to-high Mach number flight. The results to-date show that an axial compressor with cooling: (1) relieves choking in rear stages (hence opening up operability), (2) yields higher-pressure ratio and (3) yields higher efficiency for a given corrected speed and mass flow. The performance benefit is driven: (i) at the blade passage level, by a decrease in the total pressure reduction coefficient and an increase in the flow turning; and (ii) by the reduction in temperature that results in less work required for a given pressure ratio. The latter is a thermodynamic effect. As an example, calculations were performed for an eight-stage compressor with an adiabatic design pressure ratio of 5. By defining non-dimensional cooling as the percentage of compressor inlet stagnation enthalpy removed by a heat sink, the model shows that a non-dimensional cooling of percent in each blade row of the first two stages can increase the compressor pressure ratio by as much as 10-20 percent. Maximum corrected mass flow at a given corrected speed may increase by as much as 5 percent. In addition, efficiency may increase by as much as 5 points. A framework for characterizing and generating the performance map for a cooled compressor has been developed. The approach is based upon CFD computations and mean line analysis. Figures of merit that characterize the bulk performance of blade passage flows with and without cooling are extracted from CFD solutions. Such performance characterization is then applied to a preliminary compressor design framework (mean line). The generic nature of this approach makes it suitable for assessing the effect of different types of compressor cooling schemes, such as heat exchange or evaporative cooling (mass injection). Future work will focus on answering system level questions regarding the feasibility of compressor cooling. Specifically, we wish to determine the operational parametric space in which compressor cooling would be advantageous over other high flight Mach number propulsion concepts. In addition, we will explore the design requirements of cooled compressor turbomachinery, as well as the flow phenomena that limit and control its operation, and the technology barriers that must be crossed for its implementation.

Effects of variable properties on MHD heat and mass transfer flow near a stagnation point towards a stretching sheet in a porous medium with thermal radiation

NASA Astrophysics Data System (ADS)

M. Salem, A.; Rania, Fathy

2012-05-01

The effect of variable viscosity and thermal conductivity on steady magnetohydrodynamic (MHD) heat and mass transfer flow of viscous and incompressible fluid near a stagnation point towards a permeable stretching sheet embedded in a porous medium are presented, taking into account thermal radiation and internal heat genberation/absorbtion. The stretching velocity and the ambient fluid velocity are assumed to vary linearly with the distance from the stagnation point. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing fundamental equations are first transformed into a system of ordinary differential equations using a scaling group of transformations and are solved numerically by using the fourth-order Rung—Kutta method with the shooting technique. A comparison with previously published work has been carried out and the results are found to be in good agreement. The results are analyzed for the effect of different physical parameters, such as the variable viscosity and thermal conductivity, the ratio of free stream velocity to stretching velocity, the magnetic field, the porosity, the radiation and suction/injection on the flow, and the heat and mass transfer characteristics. The results indicate that the inclusion of variable viscosity and thermal conductivity into the fluids of light and medium molecular weight is able to change the boundary-layer behavior for all values of the velocity ratio parameter λ except for λ = 1. In addition, the imposition of fluid suction increases both the rate of heat and mass transfer, whereas fluid injection shows the opposite effect.

Thermal regime of the San Andreas fault near Parkfield, California

USGS Publications Warehouse

Sass, J.H.; Williams, C.F.; Lachenbruch, A.H.; Galanis, S.P.; Grubb, F.V.

1997-01-01

Knowledge of the temperature variation with depth near the San Andreas fault is vital to understanding the physical processes that occur within the fault zone during earthquakes and creep events. Parkfield is near the southern end of the Coast Ranges segment of the San Andreas fault. This segment has higher mean heat flow than the Cape Mendocino segment to the northwest or the Mojave segment to the southeast. Boreholes were drilled specifically for the U.S. Geological Survey's Parkfield earthquake prediction experiment or converted from other uses at 25 sites within a few kilometers of the fault near Parkfield. These holes, which range in depth from 150 to over 1500 m, were intended mainly for the deployment of volumetric strain meters, water-level recorders, and other downhole instruments. Temperature profiles were obtained from all the holes, and heat flow values were estimated from 17 of them. For a number of reasons, including a paucity of thermal conductivity data and rugged local topography, the accuracy of individual determinations was not sufficiently high to document local variations in heat flow. Values range from 54 to 92 mW m-2, with mean and 95% confidence limits of 74 ?? 4 mW m-2. This mean is slightly lower than the mean (83 ?? 3) of 39 previously published values from the central Coast Ranges, but it is consistent with the overall pattern of elevated heat flow in the Coast Ranges, and it is transitional to the mean of 68 ?? 2 mW m-2 that characterizes the Mojave segment of the San Andreas fault immediately to the south. The lack of a heat flow peak near the fault underscores the absence of a frictional thermal anomaly and provides additional support for a very small resolved shear stress parallel to the San Andreas fault and the nearly fault-normal maximum compressive stress observed in this region. Estimates of subsurface thermal conditions indicate that the seismic-aseismic transition for the Parkfield segment corresponds to temperatures in the range of 350??-400??C. Increasing heat flow to the northwest of Parkfield corresponds to a transition from locked to creeping sections and to a shallowing of the base of seismicity and confirms the importance of temperature in controlling the thickness of the seismogenic crust. Lateral variations in heat flow do not appear to have any major role in determining the regularity of M5.5-6 earthquakes at Parkfield.

Advanced Transportation Systems, Alternate Propulsion Subsystem Concepts

NASA Technical Reports Server (NTRS)

1997-01-01

An understanding of the basic flow of of the subject hybrid model has been gained through this series of testing. Changing injectors (axial vs. radial) and inhibiting the flow between the upstream plenum and the CP section changes the basic flow structure, as evidenced by streamline and velocity contour plots. Numerous shear layer structures were identified in the test configurations; these structures include both standing and traveling vortices which may affect combustion ion stability. Standing vortices may play a role in the heat addition process as the oxidizer enters the motor, while traveling vortices may be instability mechanisms in themselves. Finally, the flow visualization and LVD measurements give insight into determining the effects of flow induced shear layers.

Heat transfer analysis of a lab scale solar receiver using the discrete ordinates model

NASA Astrophysics Data System (ADS)

Dordevich, Milorad C. W.

This thesis documents the development, implementation and simulation outcomes of the Discrete Ordinates Radiation Model in ANSYS FLUENT simulating the radiative heat transfer occurring in the San Diego State University lab-scale Small Particle Heat Exchange Receiver. In tandem, it also serves to document how well the Discrete Ordinates Radiation Model results compared with those from the in-house developed Monte Carlo Ray Trace Method in a number of simplified geometries. The secondary goal of this study was the inclusion of new physics, specifically buoyancy. Implementation of an additional Monte Carlo Ray Trace Method software package known as VEGAS, which was specifically developed to model lab scale solar simulators and provide directional, flux and beam spread information for the aperture boundary condition, was also a goal of this study. Upon establishment of the model, test cases were run to understand the predictive capabilities of the model. It was shown that agreement within 15% was obtained against laboratory measurements made in the San Diego State University Combustion and Solar Energy Laboratory with the metrics of comparison being the thermal efficiency and outlet, wall and aperture quartz temperatures. Parametric testing additionally showed that the thermal efficiency of the system was very dependent on the mass flow rate and particle loading. It was also shown that the orientation of the small particle heat exchange receiver was important in attaining optimal efficiency due to the fact that buoyancy induced effects could not be neglected. The analyses presented in this work were all performed on the lab-scale small particle heat exchange receiver. The lab-scale small particle heat exchange receiver is 0.38 m in diameter by 0.51 m tall and operated with an input irradiation flux of 3 kWth and a nominal mass flow rate of 2 g/s with a suspended particle mass loading of 2 g/m3. Finally, based on acumen gained during the implementation and development of the model, a new and improved design was simulated to predict how the efficiency within the small particle heat exchange receiver could be improved through a few simple internal geometry design modifications. It was shown that the theoretical calculated efficiency of the small particle heat exchange receiver could be improved from 64% to 87% with adjustments to the internal geometry, mass flow rate, and mass loading.

Non-equilibrium thermodynamics, heat transport and thermal waves in laminar and turbulent superfluid helium

NASA Astrophysics Data System (ADS)

Mongiovì, Maria Stella; Jou, David; Sciacca, Michele

2018-01-01

This review paper puts together some results concerning non equilibrium thermodynamics and heat transport properties of superfluid He II. A one-fluid extended model of superfluid helium, which considers heat flux as an additional independent variable, is presented, its microscopic bases are analyzed, and compared with the well known two-fluid model. In laminar situations, the fundamental fields are density, velocity, absolute temperature, and heat flux. Such a theory is able to describe the thermomechanical phenomena, the propagation of two sounds in liquid helium, and of fourth sound in superleak. It also leads in a natural way to a two-fluid model on purely macroscopical grounds and allows a small amount of entropy associated with the superfluid component. Other important features of liquid He II arise in rotating situations and in superfluid turbulence, both characterized by the presence of quantized vortices (thin vortex lines whose circulation is restricted by a quantum condition). Such vortices have a deep influence on the transport properties of superfluid helium, as they increase very much its thermal resistance. Thus, heat flux influences the vortices which, in turn, modify the heat flux. The dynamics of vortex lines is the central topic in turbulent superfluid helium. The model is generalized to take into account the vortices in different cases of physical interest: rotating superfluids, counterflow superfluid turbulence, combined counterflow and rotation, and mass flow in addition to heat flow. To do this, the averaged vortex line density per unit volume L, is introduced and its dynamical equations are considered. Linear and non-linear evolution equations for L are written for homogeneous and inhomogeneous, isotropic and anisotropic situations. Several physical experiments are analyzed and the influence of vortices on the effective thermal conductivity of turbulent superfluid helium is found. Transitions from laminar to turbulent flows, from diffusive to ballistic regimes, from isotropic to anisotropic situations, are analyzed, thus providing a wide range of practical applications. Besides the steady-state effective thermal conductivity, the propagation of harmonic waves is also studied, motivated by the fact that vortex line density is experimentally detected via the attenuation of second sound and because it provides dynamical information on heat transport and thermal waves which complement the static information of the thermal conductivity.

K-65-12.8 condensing steam turbine

NASA Astrophysics Data System (ADS)

Valamin, A. E.; Kultyshev, A. Yu.; Gol'dberg, A. A.; Sakhnin, Yu. A.; Bilan, V. N.; Stepanov, M. Yu.; Polyaeva, E. N.; Shekhter, M. V.; Shibaev, T. L.

2016-11-01

A new condensing steam turbine K-65-12.8 is considered, which is the continuation of the development of the steam turbine family of 50-70 MW and the fresh steam pressure of 12.8 MPa, such as twocylinder T-50-12.8 and T-60/65-12.8 turbines. The turbine was developed using the modular design. The design and the main distinctive features of the turbine are described, such as a single two-housing cylinder with the steam flow loop; the extraction from the blading section for the regeneration, the inner needs, and heating; and the unification of some assemblies of serial turbines with shorter time of manufacture. The turbine uses the throttling steam distribution; steam from a boiler is supplied to a turbine through a separate valve block consisting of a central shut-off valve and two side control valves. The blading section of a turbine consists of 23 stages: the left flow contains ten stages installed in the inner housing and the right flow contains 13 stages with diaphragm placed in holders installed in the outer housing. The disks of the first 16 stages are forged together with a rotor, and the disks of the rest stages are mounted. Before the two last stages, the uncontrolled steam extraction is performed for the heating of a plant with the heat output of 38-75 GJ/h. Also, a turbine has five regenerative extraction points for feed water heating and the additional steam extraction to a collector for the inner needs with the consumption of up to 10 t/h. The feasibility parameters of a turbine plant are given. The main solutions for the heat flow diagram and the layout of a turbine plant are presented. The main principles and features of the microprocessor electro hydraulic control and protection system are formulated.

Updates to Multi-Dimensional Flux Reconstruction for Hypersonic Simulations on Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2010-01-01

The quality of simulated hypersonic stagnation region heating with tetrahedral meshes is investigated by using an updated three-dimensional, upwind reconstruction algorithm for the inviscid flux vector. An earlier implementation of this algorithm provided improved symmetry characteristics on tetrahedral grids compared to conventional reconstruction methods. The original formulation however displayed quantitative differences in heating and shear that were as large as 25% compared to a benchmark, structured-grid solution. The primary cause of this discrepancy is found to be an inherent inconsistency in the formulation of the flux limiter. The inconsistency is removed by employing a Green-Gauss formulation of primitive gradients at nodes to replace the previous Gram-Schmidt algorithm. Current results are now in good agreement with benchmark solutions for two challenge problems: (1) hypersonic flow over a three-dimensional cylindrical section with special attention to the uniformity of the solution in the spanwise direction and (2) hypersonic flow over a three-dimensional sphere. The tetrahedral cells used in the simulation are derived from a structured grid where cell faces are bisected across the diagonal resulting in a consistent pattern of diagonals running in a biased direction across the otherwise symmetric domain. This grid is known to accentuate problems in both shock capturing and stagnation region heating encountered with conventional, quasi-one-dimensional inviscid flux reconstruction algorithms. Therefore the test problems provide a sensitive indicator for algorithmic effects on heating. Additional simulations on a sharp, double cone and the shuttle orbiter are then presented to demonstrate the capabilities of the new algorithm on more geometrically complex flows with tetrahedral grids. These results provide the first indication that pure tetrahedral elements utilizing the updated, three-dimensional, upwind reconstruction algorithm may be used for the simulation of heating and shear in hypersonic flows in upwind, finite volume formulations.

New Marine Heat Flow measurements at the Costa Rica Rift, Panama Basin

NASA Astrophysics Data System (ADS)

Harris, R. N.; Kolandaivelu, K. P.; Gregory, E. P. M.; Alshafai, R.; Lowell, R. P.; Hobbs, R. W.

2016-12-01

We report new heat flow measurements collected along the southern flank of the Costa Rica ridge. This ridge flank has been the site of numerous seismic, heat flow, and ocean drilling experiments and has become an important type location for investigations of off-axis hydrothermal processes. These data were collected as part of an interdisciplinary NERC and NSF-funded collaboration entitled: Oceanographic and Seismic Characterization of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR), to better understand links between crustal evolution, hydrothermal heat loss and the impact of this heat loss and fluid mass discharge on deep ocean circulation. The heat flow measurements are collocated with a newly acquired high-resolution seismic profile collected using a GI-gun source to image the sedimentary and upper crustal section. The profile is tied to ODP Hole 504B and provides robust estimates of the sediment thickness as well as its internal structure. In total five heat flow stations consisting of 67 new heat flow measurements were made, spanning crustal ages between 1.3 and 5.4 Myr. The full spreading rate of 66 mm/yr gives rise to abyssal hill basement relief between 500 and 250 m. Sediment cover is relatively incomplete in this region and varies between 0 and 290 m. The majority of heat flow values fall below half-space cooling models indicating that significant amounts of heat are removed by hydrothermal circulation. Low heat flow values are observed in sediment ponds between abyssal hill relief and high values are generally associated with ridge-ward dipping faults bounding abyssal hills. These faults are likely high permeability pathways where heated fluids are discharging, providing an example where large-scale faulting and block rotation plays a major role in ventilated ridge flank fluid circulation. The heat flow fraction (qobs/qpred) varies between varies between 0.01 and 4.1 and has a mean of 0.3 indicating that on average 70% of the expected heat is advected. The mass flux associated with this heat advection is 5 x 10-6 kg/m2-s assuming temperature discharge on the ridge flank is 10° C above ambient.

Periodic unsteady effects on turbulent boundary layer transport and heat transfer: An experimental investigation in a cylinder-wall junction flow

NASA Astrophysics Data System (ADS)

Xie, Qi

Heat transfer in a turbulent boundary layer downstream of junction with a cylinder has many engineering applications including controlling heat transfer to the endwall in gas turbine passages and cooling of protruding electronic chips. The main objective of this research is to study the fundamental process of heat transport and wall heat transfer in a turbulent three-dimensional flow superimposed with local large-scale periodic unsteadiness generated by vortex shedding from the cylinder. Direct measurements of the Reynolds heat fluxes (/line{utheta},\\ /line{vtheta}\\ and\\ /line{wtheta}) and time-resolved wall heat transfer rate will provide insight into unsteady flow behavior and data for advanced turbulence models for numerical simulation of complex engineering flows. Experiments were conducted in an open-circuit, low-speed wind tunnel. Reynolds stresses and heat fluxes were obtained from turbulent heat-flux probes which consisted of two hot wires, arranged in an X-wire configuration, and a cold wire located in front of the X-wire. Thin-film surface heat flux sensors were designed for measuring time-resolved wall heat flux. A reference probe and conditional-sampling technique connected the flow field dynamics to wall heat transfer. An event detecting and ensemble-averaging method was developed to separate effects of unsteadiness from those of background turbulence. Results indicate that unsteadiness affects both heat transport and wall heat transfer. The flow behind the cylinder can be characterized by three regions: (1) Wake region, where unsteadiness is observed to have modest effect; (2) Unsteady region, where the strongest unsteadiness effect is found; (3) Outer region, where the flow approaches the two-dimensional boundary-layer behavior. Vortex shedding from both sides of the cylinder contributes to mixing enhancement in the wake region. Unsteadiness contributes up to 51% of vertical and 59% of spanwise turbulent heat fluxes in the unsteady region. The instantaneous wall Stanton number increased up to 100% compared with an undisturbed flow. Large-scale fluctuations of wall Stanton number were due to the periodic thinning and thickening of the thermal layer caused by periodic vertical velocity fluctuations. This suggests that the outerlayer motion affects near-wall flow behavior and wall heat transfer.

Heat flow in Oklahoma

NASA Astrophysics Data System (ADS)

Cranganu, Constantin

Twenty new heat flow values are incorporated, along with 40 previously published data, into a heat flow map of Oklahoma. The new heat flow data were estimated using previous temperature measurements in boreholes made by American Petroleum Institute researchers and 1,498 thermal conductivity measurements on drill cuttings. The mean of 20 average thermal gradients is 30.50sp°C/km. In general, thermal gradients increase from SW (14.11sp°C/km) to NE (42.24sp°C/km). The range of 1,498 in situ thermal conductivity measurements (after corrections for anisotropy, in situ temperature, and porosity) is 0.90-6.1 W/m-K; the average is 1.68 W/m-K. Estimated near-surface heat flow (±20%) at 20 new sites in Oklahoma varies between 22 ± 4 mW/msp2 and 86 ± 17 mW/msp2; the average is 50 mW/msp2. Twenty-seven new heat-generation estimates, along with 22 previously published data, are used to create a heat generation map of Oklahoma. The range of heat production estimates is 1.1-3.5 muW/msp3, with an average of 2.5 muW/msp3. The heat flow regime in Oklahoma is primarily conductive in nature, except for a zone in northeast. Transient effects due to sedimentary processes and metamorphic/igneous activity, as well as past climatic changes, do not significantly influence the thermal state of the Oklahoma crust. Heat flow near the margins of the Arkoma and Anadarko Basins may be depressed or elevated by 5-13 mW/msp2 by refraction of heat from sedimentary rocks of relatively low thermal conductivity (1-2 W/m-K) into crystalline basement rocks of relatively high thermal conductivity (˜3-4 W/m-K). The heat generation-heat flow relationship shows a modest correlation. The relatively high heat flow (˜70-80 mW/msp2) in part of northeastern Oklahoma suggests that the thermal regime there may be perturbed by regional groundwater flow originating in the fractured outcrops of the Arbuckle-Simpson aquifer in the Arbuckle Mountains.

Heat Pipe Planets

NASA Technical Reports Server (NTRS)

Moore, William B.; Simon, Justin I.; Webb, A. Alexander G.

2014-01-01

When volcanism dominates heat transport, a terrestrial body enters a heat-pipe mode, in which hot magma moves through the lithosphere in narrow channels. Even at high heat flow, a heat-pipe planet develops a thick, cold, downwards-advecting lithosphere dominated by (ultra-)mafic flows and contractional deformation at the surface. Heat-pipes are an important feature of terrestrial planets at high heat flow, as illustrated by Io. Evidence for their operation early in Earth's history suggests that all terrestrial bodies should experience an episode of heat-pipe cooling early in their histories.

Global map of heat flow on a 2 degree grid - digitally available

NASA Astrophysics Data System (ADS)

Davies, J. Huw

2014-05-01

A global map of surface heat flow is developed on a 2° by 2° equal area grid, and is made available digitally. It is based on a global heat flow data set of over 38,000 measurements, very similar to that used in Davies & Davies (2010). The map consists of three components. Firstly, in regions of young ocean crust (<67.7Ma) the model estimate uses a half-space conduction model based on the age of the oceanic crust, using parameters of Jaupart et al., (2007). This is done since it is well known that raw data measurements are frequently influenced by significant hydrothermal circulation. Secondly in other regions of data coverage the estimate is based on data measurements. At the map resolution these two categories (young ocean, data covered) cover 65% of Earth's surface. The estimate has been developed in two different ways. In one way the mean value is used and in the second the median is used. The median estimate might be expected to be less sensitive to outliers. Thirdly, for all other regions the estimate is based on the assumption that there is a correlation between heat-flow and geology. This is undertaken using the CCGM (2000) digital geology map. This assumption is assessed and the correlation is found to provide a minor improvement over assuming that heat flow would be represented by the global average. The estimate for Antarctica is guided by proxy measurements. All the work is undertaken using GIS methods. Estimates are made of the errors for all components. The results have been made available as digital files, including shapefiles and tab-delimited and csv ASCII files. In addition to the equal area grid, the results are also available on an equal longitude grid. The map has been published -Davies (2013). The digital files are available in the supplementary information of the publication. Commission for the Geological Map of the World (2000), Geological Map of the World at 1:25000000, UNESCO/CCGM, Paris. Davies, JH, (2013) A global map of solid Earth surface heat flow, Geochemistry, Geophysics and Geosystems, 14, 4608-4622, doi 10.1002/ggge.20271. Davies JH & Davies DR, (2010) Earth's surface heat flux, Solid Earth, 1, 5-24, www.solid-earth.net/1/5/2010/. Jaupart C, Labrosse S, Mareschal J-C, (2007) Temperatures, heat and energy in the mantle of the Earth, in Treatise on Geophysics, v7 Mantle Convection, ed D. Bercovici, 253-303, Elsevier, Amsterdam

Experimental study of Cu-water nanofluid forced convective flow inside a louvered channel

NASA Astrophysics Data System (ADS)

Khoshvaght-Aliabadi, M.; Hormozi, F.; Zamzamian, A.

2015-03-01

Heat transfer enhancement plays a very important role for energy saving in plate-fin heat exchangers. In the present study, the influences of simultaneous utilization of a louvered plate-fin channel and copper-base deionized water nanofluid on performance of these exchangers are experimentally explored. The effects of flow rate (2-5 l/min) and nanoparticles weight fraction (0-0.4 %) on heat transfer and pressure drop characteristics are determined. Experimental results indicate that the use of louvered channel instead of the plain one can improve the heat transfer performance. Likewise, addition of small amounts of copper nanoparticles to the base fluid augments the convective heat transfer coefficient remarkably. The maximum rise of 21.7 % in the convective heat transfer coefficient is observed for the 0.4 % wt nanofluid compared to the base fluid. Also, pumping power for the base fluid and nanofluids are calculated based on the measured pressure drop in the louvered channel. The average increase in pumping power is 11.8 % for the nanofluid with 0.4 % wt compared to the base fluid. Applied performance criterion shows a maximum performance index of 1.167 for the nanofluid with 0.1 % wt Finally, two correlations are proposed for Nusselt number and friction factor which fit the experimental data with in ±10 %.

Calculation of heat flux through a wall containing a cavity: Comparison of several models

NASA Astrophysics Data System (ADS)

Park, J. E.; Kirkpatrick, J. R.; Tunstall, J. N.; Childs, K. W.

1986-02-01

This paper describes the calculation of the heat transfer through the standard stud wall structure of a residential building. The wall cavity contains no insulation. Results from five test cases are presented. The first four represent progressively more complicated approximations to the heat transfer through and within a hollow wall structure. The fifth adds the model components necessary to severely inhibit the radiative energy transport across the empty cavity. Flow within the wall cavity is calculated from the Navier-Stokes equations and the energy conservation equation for an ideal gas using an improvement to the Implicit-Compressible Eulerian (ICE) algorithm of Harlow and Amsden. An algorithm is described to efficiently couple the fluid flow calculations to the radiation-conduction model for the solid portions of the system. Results indicate that conduction through still plates contributes less than 2% of the total heat transferred through a composite wall. All of the other elements (conduction through wall board, sheathing, and siding; convection from siding and wallboard to am bients; and radiation across the wall cavity) are required to accurately predict the heat transfer through a wall. Addition of a foil liner on one inner surface of the wall cavity reduces the total heat transferred by almost 50%.

Frictional strength and heat flow of southern San Andreas Fault

NASA Astrophysics Data System (ADS)

Zhu, P. P.

2016-01-01

Frictional strength and heat flow of faults are two related subjects in geophysics and seismology. To date, the investigation on regional frictional strength and heat flow still stays at the stage of qualitative estimation. This paper is concentrated on the regional frictional strength and heat flow of the southern San Andreas Fault (SAF). Based on the in situ borehole measured stress data, using the method of 3D dynamic faulting analysis, we quantitatively determine the regional normal stress, shear stress, and friction coefficient at various seismogenic depths. These new data indicate that the southern SAF is a weak fault within the depth of 15 km. As depth increases, all the regional normal and shear stresses and friction coefficient increase. The former two increase faster than the latter. Regional shear stress increment per kilometer equals 5.75 ± 0.05 MPa/km for depth ≤15 km; regional normal stress increment per kilometer is equal to 25.3 ± 0.1 MPa/km for depth ≤15 km. As depth increases, regional friction coefficient increment per kilometer decreases rapidly from 0.08 to 0.01/km at depths less than ~3 km. As depth increases from ~3 to ~5 km, it is 0.01/km and then from ~5 to 15 km, and it is 0.002/km. Previously, frictional strength could be qualitatively determined by heat flow measurements. It is difficult to obtain the quantitative heat flow data for the SAF because the measured heat flow data exhibit large scatter. However, our quantitative results of frictional strength can be employed to investigate the heat flow in the southern SAF. We use a physical quantity P f to describe heat flow. It represents the dissipative friction heat power per unit area generated by the relative motion of two tectonic plates accommodated by off-fault deformation. P f is called "fault friction heat." On the basis of our determined frictional strength data, utilizing the method of 3D dynamic faulting analysis, we quantitatively determine the regional long-term fault friction heat at various seismogenic depths in the southern SAF. The new data show that as depth increases, regional friction stress increases within the depth of 15 km; its increment per kilometer equals 5.75 ± 0.05 MPa/km. As depth increases, regional long-term fault friction heat increases; its increment per kilometer is equal to 3.68 ± 0.03 mW/m2/km. The values of regional long-term fault friction heat provided by this study are always lower than those from heat flow measurements. The difference between them and the scatter existing in the measured heat flow data are mainly caused by the following processes: (i) heat convection, (ii) heat advection, (iii) stress accumulation, (iv) seismic bursts between short-term lull periods in a long-term period, and (v) influence of seismicity in short-term periods upon long-term slip rate and heat flow. Fault friction heat is a fundamental parameter in research on heat flow.

PUMPS FOR LIQUID CURRENT-CONDUCTING MATERIAL

DOEpatents

Watt, D.A.

1958-12-23

An induction-type liquid conductor pump is described wherein the induced current flow is substantially tnansverse to the flow of the liquid in the duct, thus eliminating parallel current flow that tends to cause unwanted pressures resulting in turbulence, eddy-flow, heating losses, and reduced pumping efficiency. This improvement is achieved by offering the parallel current a path of lower impedance along the duct than that offered by the liquid so that the induced currents remaining in the liquid flow in a substantially transverse directlon. Thick copper bars are brazed to the liquid duct parallel to the flow, and additional induced currents are created in the copper bars of appropriate magnitude to balance the ohmic drop ln the current paths outside of the liquid metal.

A prototype heat pipe heat exchanger for the capillary pumped loop flight experiment

NASA Technical Reports Server (NTRS)

Ku, Jentung; Yun, Seokgeun; Kroliczek, Edward J.

1992-01-01

A Capillary Pumped Two-Phase Heat Transport Loop (CAPL) Flight Experiment, currently planned for 1993, will provide microgravity verification of the prototype capillary pumped loop (CPL) thermal control system for EOS. CAPL employs a heat pipe heat exchanger (HPHX) to couple the condenser section of the CPL to the radiator assembly. A prototype HPHX consisting of a heat exchanger (HX), a header heat pipe (HHP), a spreader heat pipe (SHP), and a flow regulator has been designed and tested. The HX transmits heat from the CPL condenser to the HHP, while the HHP and SHP transport heat to the radiator assembly. The flow regulator controls flow distribution among multiple parallel HPHX's. Test results indicated that the prototype HPHX could transport up to 800 watts with an overall heat transfer coefficient of more than 6000 watts/sq m-deg C. Flow regulation among parallel HPHX's was also demonstrated.

Using hydrogeologic data to evaluate geothermal potential in the eastern Great Basin

USGS Publications Warehouse

Masbruch, Melissa D.; Heilweil, Victor M.; Brooks, Lynette E.

2012-01-01

In support of a larger study to evaluate geothermal resource development of high-permeability stratigraphic units in sedimentary basins, this paper integrates groundwater and thermal data to evaluate heat and fluid flow within the eastern Great Basin. Previously published information from a hydrogeologic framework, a potentiometric-surface map, and groundwater budgets was compared to a surficial heat-flow map. Comparisons between regional groundwater flow patterns and surficial heat flow indicate a strong spatial relation between regional groundwater movement and surficial heat distribution. Combining aquifer geometry and heat-flow maps, a selected group of subareas within the eastern Great Basin are identified that have high surficial heat flow and are underlain by a sequence of thick basin-fill deposits and permeable carbonate aquifers. These regions may have potential for future geothermal resources development.

Mathematical model development and simulation of heat pump fruit dryer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achariyaviriya, S.; Soponronnarit, S.; Terdyothin, A.

2000-01-01

A mathematical model of a heat pump fruit dryer was developed to study the performance of heat pump dryers. Using the moisture content of papaya glace drying, the refrigerant temperature at the evaporator and condenser and the performance, was verified. It was found that the simulated results using closed loop heat pump dryer were close to the experimental results. The criteria for evaluating the performance were specific moisture extraction rate and drying rate. The results showed that ambient conditions affected significantly on the performance of the open loop dryer and the partially closed loop dryer. Also, the fraction of evaporatormore » bypass air affected markedly the performance of all heat pump dryers. In addition, it was found that specific air flow rate and drying air temperature affected significantly the performance of all heat pump dryers.« less

Survey of literature on convective heat transfer coefficients and recovery factors for high atmosphere thermometry

NASA Technical Reports Server (NTRS)

Chung, S.

1973-01-01

Heat transfer phenomena of rarefied gas flows is discussed based on a literature survey of analytical and experimental rarefied gas dynamics. Subsonic flows are emphasized for the purposes of meteorological thermometry in the high atmosphere. The heat transfer coefficients for three basic geometries are given in the regimes of free molecular flow, transition flow, slip flow, and continuum flow. Different types of heat phenomena, and the analysis of theoretical and experimental data are presented. The uncertainties calculated from the interpolation rule compared with the available experimental data are discussed. The recovery factor for each geometry in subsonic rarefied flows is also given.

Heat-flow measurements at shot points along the 1978 Saudi Arabia seismic deep-refraction line; Part I, Results of the measurements

USGS Publications Warehouse

Gettings, M.E.; Showail, Abdullah

1982-01-01

Heat-flow measurements were made at five onland shot points of the 1978 Saudi Arabian seismic deep-refraction line, which sample major tectonic elements of the Arabian Shield along a profile from Ar Riyad to the Farasan Islands. Because of the pattern drilling at each shot point, several holes (60 m deep) could be logged for temperature at each site and thus allow a better estimate of the geothermal gradient. Each site was mapped and sampled in detail, and modal and. chemical analyses of representative specimens were made in the laboratory. Thermal conductivities were computed from the modal analyses and single-mineral conductivity data. The resulting heat-flow values, combined with published values for the Red Sea and coastal plain, indicate a three-level pattern, with a heat flow of about 4.5 heat-flow unit (HFU) over the Red Sea axial trough, about 3.0 HFU over the shelf and coastal plain, and an essentially constant 1.0 HFU over the Arabian Shield at points well away from the suture zone with the oceanic crust. At three sites where the rocks are granitic, gamma-ray spectrometry techniques were employed to estimate thorium, potassium, and uranium concentrations. The resulting plot of heat generation versus heat flow suggests that in the Arabian Shield the relationship between heat flow and heat production is not linear. More heat-flow data are essential to establish or reject this conclusion.

Particle shape effect on heat transfer performance in an oscillating heat pipe.

PubMed

Ji, Yulong; Wilson, Corey; Chen, Hsiu-Hung; Ma, Hongbin

2011-04-05

The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP) was investigated experimentally. A binary mixture of ethylene glycol (EG) and deionized water (50/50 by volume) was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP.

Particle shape effect on heat transfer performance in an oscillating heat pipe

PubMed Central

2011-01-01

The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP) was investigated experimentally. A binary mixture of ethylene glycol (EG) and deionized water (50/50 by volume) was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP. PMID:21711830

A computationally efficient method for full-core conjugate heat transfer modeling of sodium fast reactors

DOE PAGES

Hu, Rui; Yu, Yiqi

2016-09-08

For efficient and accurate temperature predictions of sodium fast reactor structures, a 3-D full-core conjugate heat transfer modeling capability is developed for an advanced system analysis tool, SAM. The hexagon lattice core is modeled with 1-D parallel channels representing the subassembly flow, and 2-D duct walls and inter-assembly gaps. The six sides of the hexagon duct wall and near-wall coolant region are modeled separately to account for different temperatures and heat transfer between coolant flow and each side of the duct wall. The Jacobian Free Newton Krylov (JFNK) solution method is applied to solve the fluid and solid field simultaneouslymore » in a fully coupled fashion. The 3-D full-core conjugate heat transfer modeling capability in SAM has been demonstrated by a verification test problem with 7 fuel assemblies in a hexagon lattice layout. In addition, the SAM simulation results are compared with RANS-based CFD simulations. Very good agreements have been achieved between the results of the two approaches.« less

Mathematical Modeling of Dual Layer Shell Type Recuperation System for Biogas Dehumidification

NASA Astrophysics Data System (ADS)

Gendelis, S.; Timuhins, A.; Laizans, A.; Bandeniece, L.

2015-12-01

The main aim of the current paper is to create a mathematical model for dual layer shell type recuperation system, which allows reducing the heat losses from the biomass digester and water amount in the biogas without any additional mechanical or chemical components. The idea of this system is to reduce the temperature of the outflowing gas by creating two-layered counter-flow heat exchanger around the walls of biogas digester, thus increasing a thermal resistance and the gas temperature, resulting in a condensation on a colder surface. Complex mathematical model, including surface condensation, is developed for this type of biogas dehumidifier and the parameter study is carried out for a wide range of parameters. The model is reduced to 1D case to make numerical calculations faster. It is shown that latent heat of condensation is very important for the total heat balance and the condensation rate is highly dependent on insulation between layers and outside temperature. Modelling results allow finding optimal geometrical parameters for the known gas flow and predicting the condensation rate for different system setups and seasons.

Experimental and numerical investigation on thermal fluid-structure interaction on ceramic plates in high enthalpy flow

NASA Astrophysics Data System (ADS)

Willems, Sebastian; Esser, Burkard; Gülhan, Ali

2015-12-01

A detailed knowledge of the fluid-structure interaction in hypersonic flows is important for the design of future space transportation systems. The thermal aspect of such an interaction was investigated with the help of a generic model in the arc-heated wind tunnel L3K at the German Aerospace Center in Cologne. Flat and curved panels of the fibre-reinforced ceramics C/C-SiC with and without anti-oxidation coating where used. Several configurations with and without back plane insulation were tested at 10° and 20° angle of attack. The panel heating was measured with an infrared camera, several thermocouples and pyrometers. The experimental results show the influence of the shape as well as of radiation cooling and radiation heating. The experiments also reveal the effect of additional heating due to recombination of atomic oxygen on the surface. At certain configurations a local temperature peak moved over the panel. This thermal wave is also influenced by the silicon carbide coating. The analysis is supported by coupled fluid and structure simulations.

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Georgiadis, Nicholas J.; Locke, Randy J.

2018-01-01

Film cooling is used in a wide variety of engineering applications for protection of surfaces from hot or combusting gases. The design of more efficient thin film cooling geometries/configurations could be facilitated by an ability to accurately model and predict the effectiveness of current designs using computational fluid dynamics (CFD) code predictions. Hence, a benchmark set of flow field property data were obtained for use in assessing current CFD capabilities and for development of better turbulence models. Both Particle Image Velocimetry (PIV) and spontaneous rotational Raman scattering (SRS) spectroscopy were used to acquire high quality, spatially-resolved measurements of the mean velocity, turbulence intensity and also the mean temperature and normalized root mean square (rms) temperatures in a single injector cooling flow arrangement. In addition to flowfield measurements, thermocouple measurements on the plate surface enabled estimates of the film effectiveness. Raman spectra in air were obtained across a matrix of radial and axial locations downstream from a 68.07 mm square nozzle blowing heated air over a range of temperatures and Mach numbers, across a 30.48 cm long plate equipped with a single injector cooling hole. In addition, both centerline streamwise 2-component PIV and cross-stream 3-component Stereo PIV data at 15 axial stations were collected in the same flows. The velocity and temperature data were then compared against Wind-US CFD code predictions for the same flow conditions. The results of this and planned follow-on studies will support NASA's development and assessment of turbulence models for heated flows.

PIV and Rotational Raman-Based Temperature Measurements for CFD Validation in a Single Injector Cooling Flow

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Georgiadis, Nicholas J.; Locke, Randy J.

2018-01-01

Film cooling is used in a wide variety of engineering applications for protection of surfaces from hot or combusting gases. The design of more efficient thin film cooling geometries/configurations could be facilitated by an ability to accurately model and predict the effectiveness of current designs using computational fluid dynamics (CFD) code predictions. Hence, a benchmark set of flow field property data were obtained for use in assessing current CFD capabilities and for development of better turbulence models. Both Particle Image Velocimetry (PIV) and spontaneous rotational Raman scattering (SRS) spectroscopy were used to acquire high quality, spatially-resolved measurements of the mean velocity, turbulence intensity and also the mean temperature and normalized root mean square (rms) temperatures in a single injector cooling flow arrangement. In addition to flowfield measurements, thermocouple measurements on the plate surface enabled estimates of the film effectiveness. Raman spectra in air were obtained across a matrix of radial and axial locations downstream from a 68.07 mm square nozzle blowing heated air over a range of temperatures and Mach numbers, across a 30.48cm long plate equipped with a single injector cooling hole. In addition, both centerline streamwise 2-component PIV and cross-stream 3-component Stereo PIV data at 15 axial stations were collected in the same flows. The velocity and temperature data were then compared against Wind-US CFD code predictions for the same flow conditions. The results of this and planned follow-on studies will support NASA's development and assessment of turbulence models for heated flows.

Experiment of flow regime map and local condensing heat transfer coefficients inside three dimensional inner microfin tubes

NASA Astrophysics Data System (ADS)

Du, Yang; Xin, Ming Dao

1999-03-01

This paper developed a new type of three dimensional inner microfin tube. The experimental results of the flow patterns for the horizontal condensation inside these tubes are reported in the paper. The flow patterns for the horizontal condensation inside the new made tubes are divided into annular flow, stratified flow and intermittent flow within the test conditions. The experiments of the local heat transfer coefficients for the different flow patterns have been systematically carried out. The experiments of the local heat transfer coefficients changing with the vapor dryness fraction have also been carried out. As compared with the heat transfer coefficients of the two dimensional inner microfin tubes, those of the three dimensional inner microfin tubes increase 47-127% for the annular flow region, 38-183% for the stratified flow and 15-75% for the intermittent flow, respectively. The enhancement factor of the local heat transfer coefficients is from 1.8-6.9 for the vapor dryness fraction from 0.05 to 1.

Mathematical modeling heat and mass transfer processes in porous media

NASA Astrophysics Data System (ADS)

Akhmed-Zaki, Darkhan

2013-11-01

On late development stages of oil-fields appears a complex problem of oil-recovery reduction. One of solution approaches is injecting of surfactant together with water in the form of active impurities into the productive layer - for decreasing oil viscosity and capillary forces between ``oil-water'' phases system. In fluids flow the surfactant can be in three states: dissolved in water, dissolved in oil and adsorbed on pore channels' walls. The surfactant's invasion into the reservoir is tracked by its diffusion with reservoir liquid and mass-exchange with two phase (liquid and solid) components of porous structure. Additionally, in this case heat exchange between fluids (injected, residual) and framework of porous medium has practical importance for evaluating of temperature influences on enhancing oil recovery. Now, the problem of designing an adequate mathematical model for describing a simultaneous flowing heat and mass transfer processes in anisotropic heterogeneous porous medium -surfactant injection during at various temperature regimes has not been fully researched. In this work is presents a 2D mathematical model of surfactant injections into the oil reservoir. Description of heat- and mass transfer processes in a porous media is done through differential and kinetic equations. For designing a computational algorithm is used modify version of IMPES method. The sequential and parallel computational algorithms are developed using an adaptive curvilinear meshes which into account heterogeneous porous structures. In this case we can evaluate the boundaries of our process flows - fronts (``invasion'', ``heat'' and ``mass'' transfers), according to the pressure, temperature, and concentration gradient changes.

The Constrained Vapor Bubble Experiment - Interfacial Flow Region

NASA Technical Reports Server (NTRS)

Kundan, Akshay; Wayner, Peter C., Jr.; Plawsky, Joel L.

2015-01-01

Internal heat transfer coefficient of the CVB correlated to the presence of the interfacial flow region. Competition between capillary and Marangoni flow caused Flooding and not a Dry-out region. Interfacial flow region growth is arrested at higher power inputs. 1D heat model confirms the presence of interfacial flow region. 1D heat model confirms the arresting phenomena of interfacial flow region Visual observations are essential to understanding.

Planetary heat flow measurements.

PubMed

Hagermann, Axel

2005-12-15

The year 2005 marks the 35th anniversary of the Apollo 13 mission, probably the most successful failure in the history of manned spaceflight. Naturally, Apollo 13's scientific payload is far less known than the spectacular accident and subsequent rescue of its crew. Among other instruments, it carried the first instrument designed to measure the flux of heat on a planetary body other than Earth. The year 2005 also should have marked the launch of the Japanese LUNAR-A mission, and ESA's Rosetta mission is slowly approaching comet Churyumov-Gerasimenko. Both missions carry penetrators to study the heat flow from their target bodies. What is so interesting about planetary heat flow? What can we learn from it and how do we measure it?Not only the Sun, but all planets in the Solar System are essentially heat engines. Various heat sources or heat reservoirs drive intrinsic and surface processes, causing 'dead balls of rock, ice or gas' to evolve dynamically over time, driving convection that powers tectonic processes and spawns magnetic fields. The heat flow constrains models of the thermal evolution of a planet and also its composition because it provides an upper limit for the bulk abundance of radioactive elements. On Earth, the global variation of heat flow also reflects the tectonic activity: heat flow increases towards the young ocean ridges, whereas it is rather low on the old continental shields. It is not surprising that surface heat flow measurements, or even estimates, where performed, contributed greatly to our understanding of what happens inside the planets. In this article, I will review the results and the methods used in past heat flow measurements and speculate on the targets and design of future experiments.

Heat flow from the Liberian Precambrian Shield

NASA Astrophysics Data System (ADS)

Sass, J. H.; Behrendt, J. C.

1980-06-01

Uncorrected heat flow in iron formation rocks from three areas within the Liberian part of the West African Shield ranges from 50 to more than 80 mW m-2. When corrections are applied for topography and refraction, the range of heat flow is narrowed to between 38 and 42 mW m-2. In comparison with heat flows from other parts of the West African Craton, these values are consistent with preliminary results from Ghana (42±8 mW m-2) and Nigeria (38±2 mW m-2) but are somewhat higher than values from Niger (20 mW m-2) and neighboring Sierra Leone (26 mW m-2). The Liberian values are significantly lower than the heat flow offshore in the equatorial Atlantic Ocean (58±8 m W m-2), suggesting large lateral temperature gradients within the lithosphere near the coast. Values of heat production from outcrops of crystalline basement rocks near the holes are between 2 and 2.3 /μW m-3. A heat-flow/heat-production relation cannot be established because of the small range of values; however, assuming a `characteristic depth' of 8 km (similar to the North American Craton) the reduced heat flow of from 20 to 25 mW m-2 is consistent with that from other Precambrian shields.

Development of a test facility and preliminary testing of flow boiling heat transfer of R410A refrigerant with Al2O3 nanolubricants

NASA Astrophysics Data System (ADS)

Wong, Thiam

In vapor compression cycles, a small portion of the oil circulates with the refrigerant throughout the system components, while most of the oil stays in the compressors. In heat exchangers, the lubricant in excess penalizes the heat transfer and increases the pressure losses: both effects are highly undesired but yet unavoidable. Nanoparticles dispersed in the excess lubricant are expected to provide enhancements in heat transfer. While solubility and miscibility of refrigerants in polyolesters (POE) lubricant are well established knowledge, there is a lack of information regarding if and how nanoparticles dispersed in the lubricant affect these properties. This thesis presents experimental data of solubility of two types of Al2O3 nanolubricants with refrigerant R-410A. The nanoparticles were dispersed in POE lubricant by using different surfactants and dispersion methods. The nanolubricants appeared to have slightly lower solubility than that of R-410A but actually the solid nanoparticles did not really interfere with the POE oil solubility characteristics. A test facility and experimental methodology was developed for the investigation of heat transfer coefficient and pressure drop. The pressure drop of the refrigerant lubricant mixtures during flow boiling depended on the mass flux of the refrigerant. Greater augmentation was seen in the pressure drop results with decreasing mass flow rate. Pure refrigerant R410A showed the lowest pressure drop, addition of nanolubricants to the refrigerant showed a slightly higher pressure drop and POE-refrigerant mixture showed the highest pressure drop in the tests conducted. Enhancement or degradation in heat transfer coefficient during flow boiling depended on the nanoparticle concentration in the lubricant as well as the lubricant concentration in refrigerant. R410A showed the highest heat transfer coefficient for all conditions tested. For a concentration of 1% nanolubricant in refrigerant, the heat transfer coefficient showed more enhancement with increase in nanoparticle concentration compared to POE refrigerant mixtures. For a concentration of 3% nanolubricant in refrigerant mixtures there was little to no enhancement for tests conducted.

Flow instabilities in non-uniformly heated helium jet arrays used for divertor PFCs

DOE PAGES

Youchison, Dennis L.

2015-07-30

In this study, due to a lack of prototypical experimental data, little is known about the off-normal behavior of recently proposed divertor jet cooling concepts. This article describes a computational fluid dynamics (CFD) study on two jet array designs to investigate their susceptibility to parallel flow instabilities induced by non-uniform heating and large increases in the helium outlet temperature. The study compared a single 25-jet helium-cooled modular divertor (HEMJ) thimble and a micro-jet array with 116 jets. Both have pure tungsten armor and a total mass flow rate of 10 g/s at a 600 °C inlet temperature. We investigated flowmore » perturbations caused by a 30 MW/m 2 off-normal heat flux applied over a 25 mm 2 area in addition to the nominal 5 MW/m 2 applied over a 75 mm 2 portion of the face. The micro-jet array exhibited lower temperatures and a more uniform surface temperature distribution than the HEMJ thimble. We also investigated the response of a manifolded nine-finger HEMJ assembly using the nominal heat flux and a 274 mm 2 heated area. For the 30 MW/m2 case, the micro-jet array absorbed 750 W in the helium with a maximum armor surface temperature of 1280 °C and a fluid/solid interface temperature of 801 °C. The HEMJ absorbed 750 W with a maximum armor surface temperature of 1411 °C and a fluid/solid interface temperature of 844 °C. For comparison, both the single HEMJ finger and the micro-jet array used 5-mm-thick tungsten armor. The ratio of maximum to average temperature and variations in the local heat transfer coefficient were lower for the micro-jet array compared to the HEMJ device. Although high heat flux testing is required to validate the results obtained in these simulations, the results provide important guidance in jet design and manifolding to increase heat removal while providing more even temperature distribution and minimizing non-uniformity in the gas flow and thermal stresses at the armor joint.« less

Experimental determination of heat transfer in a Poiseuille-Rayleigh-Bénard flow

NASA Astrophysics Data System (ADS)

Taher, R.; Abid, C.

2018-05-01

This paper deals with an experimental study of heat transfer in a Poiseuille-Rayleigh-Bénard flow. This situation corresponds to a mixed convection phenomenon in a horizontal rectangular channel uniformly heated from below. Flow visualisation and temperature measurements were achieved in order to describe the flow regimes and heat transfer behaviour. The classical measurement techniques such employing thermocouples give local measurement on one hand and on other hand they often disturb the flow. As the flow is three-dimensional, these techniques are not efficient. In order to not disturb the flow, a non-intrusive method is used for thermal measurement. The Planar laser Induced Fluorescence (PLIF) was implemented to determine thermal fields in the fluid. Experiments conducted for various Reynolds and Rayleigh numbers allow to determine the heat transfer and thus to propose correlation for Nusselt number for a mixed convection flow in Poiseuille-Rayleigh-Bénard configuration. First a description of the use of this technique in water flow is presented and then the obtained results for various Reynolds and Rayleigh numbers allow to propose a correlation for the Nusselt number for such configuration of mixed convection. The comparison between the obtained heat transfer and the pure forced convection one confirms the well-known result that the convective heat transfer is greatly enhanced in mixed convection. Indeed, secondary flow induced by buoyant forces contributes to the refreshment of thermal boundary layers and so acts like mixers, which significantly enhances heat transfer.

Analysis of Unsteady Tip and Endwall Heat Transfer in a Highly Loaded Transonic Turbine Stage

NASA Technical Reports Server (NTRS)

Shyam, Vikram; Ameri, Ali; Chen, Jen-Ping

2010-01-01

In a previous study, vane-rotor shock interactions and heat transfer on the rotor blade of a highly loaded transonic turbine stage were simulated. The geometry consists of a high pressure turbine vane and downstream rotor blade. This study focuses on the physics of flow and heat transfer in the rotor tip, casing and hub regions. The simulation was performed using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) code MSU-TURBO. A low Reynolds number k-epsilon model was utilized to model turbulence. The rotor blade in question has a tip gap height of 2.1 percent of the blade height. The Reynolds number of the flow is approximately 3x10(exp 6) per meter. Unsteadiness was observed at the tip surface that results in intermittent "hot spots". It is demonstrated that unsteadiness in the tip gap is governed by inviscid effects due to high speed flow and is not strongly dependent on pressure ratio across the tip gap contrary to published observations that have primarily dealt with subsonic tip flows. The high relative Mach numbers in the tip gap lead to a choking of the leakage flow that translates to a relative attenuation of losses at higher loading. The efficacy of new tip geometry is discussed to minimize heat flux at the tip while maintaining choked conditions. In addition, an explanation is provided that shows the mechanism behind the rise in stagnation temperature on the casing to values above the absolute total temperature at the inlet. It is concluded that even in steady mode, work transfer to the near tip fluid occurs due to relative shearing by the casing. This is believed to be the first such explanation of the work transfer phenomenon in the open literature. The difference in pattern between steady and time-averaged heat flux at the hub is also explained.

Heat Transfer Characteristics of Mixed Electroosmotic and Pressure Driven Micro-Flows

NASA Astrophysics Data System (ADS)

Horiuchi, Keisuke; Dutta, Prashanta

We analyze heat transfer characteristics of steady electroosmotic flows with an arbitrary pressure gradient in two-dimensional straight microchannels considering the effects of Joule heating in electroosmotic pumping. Both the temperature distribution and local Nusselt number are mathematically derived in this study. The thermal analysis takes into consideration of the interaction among advective, diffusive, and Joule heating terms to obtain the thermally developing behavior. Unlike macro-scale pipes, axial conduction in micro-scale cannot be negligible, and the governing energy equation is not separable. Thus, a method that considers an extended Graetz problem is introduced. Analytical results show that the Nusselt number of pure electrooosmotic flow is higher than that of plane Poiseulle flow. Moreover, when the electroosmotic flow and pressure driven flow coexist, it is found that adverse pressure gradient to the electroosmotic flow makes the thermal entrance length smaller and the heat transfer ability stronger than pure electroosmotic flow case.

Laser heating of aqueous samples on a micro-optical-electro-mechanical system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beer, Neil Reginald; Kennedy, Ian

2013-12-17

A system of heating a sample on a microchip includes the steps of providing a microchannel flow channel in the microchip; positioning the sample within the microchannel flow channel, providing a laser that directs a laser beam onto the sample for heating the sample; providing the microchannel flow channel with a wall section that receives the laser beam and enables the laser beam to pass through wall section of the microchannel flow channel without being appreciably heated by the laser beam; and providing a carrier fluid in the microchannel flow channel that moves the sample in the microchannel flow channelmore » wherein the carrier fluid is not appreciably heated by the laser beam.« less

40 CFR 1066.125 - Data updating, recording, and control.

Code of Federal Regulations, 2014 CFR

2014-07-01

... minimum recording frequency, such as for sample flow rates from a CVS that does not have a heat exchanger... exhaust flow rate from a CVS with a heat exchanger upstream of the flow measurement 1 Hz. 40 CFR 1065.545§ 1066.425 Diluted exhaust flow rate from a CVS without a heat exchanger upstream of the flow measurement...

Turbulence modeling and surface heat transfer in a stagnation flow region

NASA Technical Reports Server (NTRS)

Wang, C. R.; Yeh, F. C.

1987-01-01

Analysis for the turbulent flow field and the effect of freestream turbulence on the surface heat transfer rate of a stagnation flow is presented. The emphasis is on modeling and its augmentation of surface heat transfer rate. The flow field considered is the region near the forward stagnation point of a circular cylinder in a uniform turbulent mean flow.

SEAWAT Version 4: A Computer Program for Simulation of Multi-Species Solute and Heat Transport

USGS Publications Warehouse

Langevin, Christian D.; Thorne, Daniel T.; Dausman, Alyssa M.; Sukop, Michael C.; Guo, Weixing

2008-01-01

The SEAWAT program is a coupled version of MODFLOW and MT3DMS designed to simulate three-dimensional, variable-density, saturated ground-water flow. Flexible equations were added to the program to allow fluid density to be calculated as a function of one or more MT3DMS species. Fluid density may also be calculated as a function of fluid pressure. The effect of fluid viscosity variations on ground-water flow was included as an option. Fluid viscosity can be calculated as a function of one or more MT3DMS species, and the program includes additional functions for representing the dependence on temperature. Although MT3DMS and SEAWAT are not explicitly designed to simulate heat transport, temperature can be simulated as one of the species by entering appropriate transport coefficients. For example, the process of heat conduction is mathematically analogous to Fickian diffusion. Heat conduction can be represented in SEAWAT by assigning a thermal diffusivity for the temperature species (instead of a molecular diffusion coefficient for a solute species). Heat exchange with the solid matrix can be treated in a similar manner by using the mathematically equivalent process of solute sorption. By combining flexible equations for fluid density and viscosity with multi-species transport, SEAWAT Version 4 represents variable-density ground-water flow coupled with multi-species solute and heat transport. SEAWAT Version 4 is based on MODFLOW-2000 and MT3DMS and retains all of the functionality of SEAWAT-2000. SEAWAT Version 4 also supports new simulation options for coupling flow and transport, and for representing constant-head boundaries. In previous versions of SEAWAT, the flow equation was solved for every transport timestep, regardless of whether or not there was a large change in fluid density. A new option was implemented in SEAWAT Version 4 that allows users to control how often the flow field is updated. New options were also implemented for representing constant-head boundaries with the Time-Variant Constant-Head (CHD) Package. These options allow for increased flexibility when using CHD flow boundaries with the zero-dispersive flux solute boundaries implemented by MT3DMS at constant-head cells. This report contains revised input instructions for the MT3DMS Dispersion (DSP) Package, Variable-Density Flow (VDF) Package, Viscosity (VSC) Package, and CHD Package. The report concludes with seven cases of an example problem designed to highlight many of the new features.

A Si/Glass Bulk-Micromachined Cryogenic Heat Exchanger for High Heat Loads: Fabrication, Test, and Application Results.

PubMed

Zhu, Weibin; White, Michael J; Nellis, Gregory F; Klein, Sanford A; Gianchandani, Yogesh B

2010-02-01

This paper reports on a micromachined Si/glass stack recuperative heat exchanger with in situ temperature sensors. Numerous high-conductivity silicon plates with integrated platinum resistance temperature detectors (Pt RTDs) are stacked, alternating with low-conductivity Pyrex spacers. The device has a 1 x 1-cm(2) footprint and a length of up to 3.5 cm. It is intended for use in Joule-Thomson (J-T) coolers and can sustain pressure exceeding 1 MPa. Tests at cold-end inlet temperatures of 237 K-252 K show that the heat exchanger effectiveness is 0.9 with 0.039-g/s helium mass flow rate. The integrated Pt RTDs present a linear response of 0.26%-0.30%/K over an operational range of 205 K-296 K but remain usable at lower temperatures. In self-cooling tests with ethane as the working fluid, a J-T system with the heat exchanger drops 76.1 K below the inlet temperature, achieving 218.7 K for a pressure of 835.8 kPa. The system reaches 200 K in transient state; further cooling is limited by impurities that freeze within the flow stream. In J-T self-cooling tests with an external heat load, the system reaches 239 K while providing 1 W of cooling. In all cases, there is an additional parasitic heat load estimated at 300-500 mW.

Low-Temperature Additive Performance in Jet A Fuels

DTIC Science & Technology

2013-04-01

coking issues for the U-2 aircraft while still retaining the required low temperature flow improvement. For the Global Hawk a lower optimum ...employ the additive at the lower concentration (2,000 mg/L), so the failure at 4,000 mg/L should not be a problem . Fuel POSF-3602 shows a JFTOT...combustor, may experience no problems due to the increased fuel viscosity caused by the additive. However, another fuel system that puts less heat into the

Use of a Scale Model in the Design of Modifications to the NASA Glenn Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Canacci, Victor A.; Gonsalez, Jose C.; Spera, David A.; Burke, Thomas (Technical Monitor)

2001-01-01

Major modifications were made in 1999 to the 6- by 9-Foot (1.8- by 2.7-m) Icing Research tunnel (IRT) at the NASA Glenn Research Center, including replacement of its heat exchanger and associated ducts and turning vanes, and the addition of fan outlet guide vanes (OGV's). A one-tenth scale model of the IRT (designated as the SMIRT) was constructed with and without these modifications and tested to increase confidence in obtaining expected improvements in flow quality around the tunnel loop. The SMIRT is itself an aerodynamic test facility whose flow patterns without modifications have been shown to be accurate, scaled representations of those measured in the IRT prior to the 1999 upgrade program. In addition, tests in the SMIRT equipped with simulated OGV's indicated that these devices in the IRT might reduce flow distortions immediately downstream of the fan by two thirds. Flow quality parameters measured in the SMIRT were projected to the full-size modified IRT, and quantitative estimates of improvements in flow quality were given prior to construction. In this paper, the results of extensive flow quality studies conducted in the SMIRT are documented. Samples of these are then compared with equivalent measurements made in the full-scale IRT, both before and after its configuration was upgraded. Airspeed, turbulence intensity, and flow angularity distributions are presented for cross sections downstream of the drive fan, both upstream and downstream of the replacement flat heat exchanger, in the stilling chamber, in the test section, and in the wakes of the new comer turning vanes with their unique expanding and contracting designs. Lessons learned from these scale-model studies are discussed.