Investigation of heat transfer efficiency in coplanar channels
NASA Astrophysics Data System (ADS)
Pelevin, F. V.; Yaroslavtsev, N. L.; Vikulin, A. V.; Orlin, S. A.; Ponomarev, A. V.
2015-03-01
Achieving more efficient heat transfer in heat-transfer devices is a topical problem. Heat transfer and pressure drop in paths containing coplanar channels of different shapes are experimentally studied in this work. It is found that the mutual crossing angles of coplanar channels, finning ratio, and the dimensions of coplanar channels are the main parameters influencing heat transfer enhancement. The best effect from using coplanar channels is achieved at the values of Reynolds number Re = 103-104. The coefficient of heat transfer in coplanar channels can be increased by a factor of 3-10 as compared with that for a smooth channel. The pressure drop coefficient ξ increases with increasing the total mutual channel crossing angle. It is found that heat transfer in flat paths with coplanar channels becomes less efficient with decreasing the coplanar channel's equivalent hydraulic diameter to 0.5-1.0 mm, whereas more efficient heat transfer is obtained by fitting these channels with flow microturbulizers. It is shown that increasing the finning height in cylindrical paths with coplanar channels has no effect on vortex formation in them; however, it results in a higher finning ratio, due to which more efficient heat transfer is obtained
Effect of microfouling on heat-transfer efficiency
Little, B.; Berger, L.R.
1980-01-01
Field experiments, performed at Keahole Point, Hawaii and in the Gulf of Mexico, were designed to determine the relationship between decreased heat transfer efficiency and the accumulation of corrosion and/or biofouling films on heat exchanger surfaces. The sample tubes were maintained under conditions simulating those of an Ocean Thermal Energy Conversion (OTEC) system and data from the two sites have been compared. Seawater flowed through 2.54 (internal diameter) metal tubes at approximately 1.8m sec/sup -1/. Four types of tubes were used: 5052 Aluminum (A1), Grade 2 titanium (Ti), 90-10 copper-nickel (Cu-Ni) and Allegheny-Ludlum 6X stainless ssteel (SS). All surfaces were colonized by microorganisms, though colonization of the Cu-Ni surface was initially retarded. Total film weight was greatest for the Al and Cu-Ni surfaces which were characterized by corrosion as well as microbial fouling. The total organic carbon: total nitrogen ratios of the fouling films from Ti, Al, SS and Cu-Ni, 4.2, 4.0, 4.8 and 7.9 respectively, remained constant throughout the experiment. The degradation of heat transfer efficiency due to the formation of fouling layers on Ti and SS is neither linear nor a simple exponential function. A microfouling model is proposed for corrosion-resistant surfaces that is consistent with field observations.
Surface heat transfer coefficient, heat efficiency, and temperature of pulsed solid-state lasers
Mann, K.; Weber, H.
1988-08-01
The temperature of solid-state lasers is a critical parameter. Efficiency and output power are strongly influenced by it. The two parameters which determine the temperature are the heat generation efficiency (HGE) and the surface heat transfer coefficient (SHTC) of the laser rod. These parameters allow the scaling of the rod temperature up to high pumping powers. Moreover, from the temperature inside the rod, the temperature gradients and the mechanical stress can be evaluated. Using transient temperature measurements, the SHTC and the HGE were determined for air- and water-cooled Nd:YAG and alexandrite lasers. The SHTC can be confirmed by theoretical considerations.
Field-structured composites for efficient, directed heat transfer
NASA Astrophysics Data System (ADS)
Martin, James E.; Gulley, G.
2009-10-01
Thermally conductive composites are needed for a variety of applications, especially as thermal interface materials. Unfortunately, the addition of even highly conductive particles to a polymer raises its conductivity only slightly and incurs a commensurate increase in the viscosity of the prepolymer resin. Meaningful increases in the thermal conductivity of the final composite require a filled resin that has the rheology of a typical paste. In this paper, we report on the use of uniaxial, biaxial, and triaxial ac magnetic fields to organize thermally conductive magnetic particles into structures that conduct heat more efficiently. Experimental results are compared to an extension of the Maxwell-Eucken theory that takes into account spatial correlations between particles. Both theory and experiment show that the thermal conductivity of field-structured composites increases essentially linearly with particle loading, and that the enhancement is significantly greater than that of unstructured composites. The measured conductivity enhancements are found to be comparable to the enhancements in magnetic permeability of these composites and are far less than the enhancements in the electrical conductivity. These results indicate the value of field structuring in enhancing the performance of a thermal interface material and show that particle percolation is not a critical factor in achieving high performance.
Efficiency of a Curzon and Ahlborn engine with Dulong-Petit heat transfer law
NASA Astrophysics Data System (ADS)
Ladino-Luna, D.
2003-02-01
Using the maximization of the power output per cycle, the optimization of a thermal engine performing a Carnot-type cycle is considered. It is assumed that the heat transfer between the reservoirs and the engine occurs according to the Dulong and Petit's heat transfer law. It is, found that the efficiency obtained with this heat transfer law can be written as a power series in the parameter lambda similar to 1/(In V-max - InVmin), where V-max and V-min are the maximum volume and minimum volume spanned by the cycle, respectively. It is also shown that the calculated efficiency verifies the semi-sum property of the ecological efficiency.
Zhang, M.; Ibekwe, S.; Li, G.; Pang, S.S.; and Lian, K.
2006-07-01
The Pressurized Water Reactors (PWRs in Figure 1) were originally developed for naval propulsion purposes, and then adapted to land-based applications. It has three parts: the reactor coolant system, the steam generator and the condenser. The Steam generator (a yellow area in Figure 1) is a shell and tube heat exchanger with high-pressure primary water passing through the tube side and lower pressure secondary feed water as well as steam passing through the shell side. Therefore, a key issue in increasing the efficiency of heat exchanger is to improve the design of steam generator, which is directly translated into economic benefits. The past research works show that the presence of a pin-fin array in a channel enhances the heat transfer significantly. Hence, using microfabrication techniques, such as LIGA, micro-molding or electroplating, some special microstructures can be fabricated around the tubes in the heat exchanger to increase the heat-exchanging efficiency and reduce the overall size of the heat-exchanger for the given heat transfer rates. In this paper, micro-pin fins of different densities made of SU-8 photoresist are fabricated and studied to evaluate overall heat transfer efficiency. The results show that there is an optimized micro pin-fin configuration that has the best overall heat transfer effects.
A new method of efficient heat transfer and storage at very high temperatures
NASA Technical Reports Server (NTRS)
Shaw, D.; Bruckner, A. P.; Hertzberg, A.
1980-01-01
A unique, high temperature (1000-2000 K) continuously operating capacitive heat exchanger system is described. The system transfers heat from a combustion or solar furnace to a working gas by means of a circulating high temperature molten refractory. A uniform aggregate of beads of a glass-like refractory is injected into the furnace volume. The aggregate is melted and piped to a heat exchanger where it is sprayed through a counter-flowing, high pressure working gas. The refractory droplets transfer their heat to the gas, undergoing a phase change into the solid bead state. The resulting high temperature gas is used to drive a suitable high efficiency heat engine. The solidified refractory beads are delivered back to the furnace and melted to continue the cycle. This approach avoids the important temperature limitations of conventional tube-type heat exchangers, giving rise to the potential of converting heat energy into useful work at considerably higher efficiencies than currently attainable and of storing energy at high thermodynamic potential.
NASA Astrophysics Data System (ADS)
Laptev, A. G.; Lapteva, E. A.
2015-07-01
The efficiency of heat and mass transfer in the bubbling bed on the plate has been investigated with the use of the method of combined physical and mathematical modeling based on the representation of the physical process in the form of a combination of elementary phenomena having a hierarchy of scales that permits realizing a scale transition in designing a contact device. The mathematical modeling of the heat and mass transfer in the above bed is based on the idea that the structure of this bed is invariant with its size and the interaction of the phases in it. A parametric investigation of the interaction of various effects in the process of heat and mass transfer in the bubbling bed on the plate and their conjugation has been carried out on the basis of the variational formulation of the conservation laws. Examples of calculating the efficiencies of the heat and mass transfer processes on bubbling plates are given. The results of calculations were compared with the corresponding experimental data.
Effects of Tip Clearance and Casing Recess on Heat Transfer and Stage Efficiency in Axial Turbines
NASA Technical Reports Server (NTRS)
Ameri, A. A.; Steinthorsson, E.; Rigby, David L.
1998-01-01
Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered. The geometry and the flow conditions of the GE-E 3 first stage turbine, which represents a modem gas turbine blade were used for the analysis. Clearance heights of 0%, 1%, 1.5% and 3% of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side but the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased. There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess, however only a small reduction was observed on the casing itself. It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances.
Improving the heat transfer efficiency of synthetic oil with silica nanoparticles.
Timofeeva, Elena V; Moravek, Michael R; Singh, Dileep
2011-12-01
The heat transfer properties of synthetic oil (Therminol 66) used for high temperature applications was improved by introducing 15 nm silicon dioxide nanoparticles. Stable suspensions of inorganic nanoparticles in the non-polar fluid were prepared using a cationic surfactant (benzalkonium chloride). The effects of nanoparticle and surfactant concentrations on thermo-physical properties (viscosity, thermal conductivity and total heat absorption) of these nanofluids were investigated in a wide temperature range. The surfactant-to-nanoparticle (SN) ratio was optimized for higher thermal conductivity and lower viscosity, which are both critical for the efficiency of heat transfer. The rheological behavior of SiO(2)/TH66 nanofluids was correlated to average agglomerate sizes, which were shown to vary with SN ratio and temperature. The conditions of ultrasonic treatment were studied and the temporary decrease of agglomerate size from an equilibrium size (characteristic to SN ratio) was demonstrated. The heat transfer efficiencies were estimated for the formulated nanofluids for both turbulent and laminar flow regimes and were compared to the performance of the base fluid. PMID:21889163
Zhao, Ye; Luo, Yuting; Zhu, Jie; Li, Juan; Gao, Xuefeng
2015-06-10
We report a type of copper-based ultrathin nickel nanocone films with high-efficiency dropwise condensation heat transfer (DCHT) performance, which can be fabricated by facile electrodeposition and low-surface-energy chemistry modification. Compared with flat copper samples, our nanosamples show condensate microdrop self-propelling (CMDSP) function and over 89% enhancement in the DCHT coefficient. Such remarkable enhancement may be ascribed to the cooperation of surface nanostructure-induced CMDSP function as well as in situ integration and ultrathin nature of nanofilms. These findings are very significant to design and develop advanced DCHT materials and devices, which help improve the efficiency of thermal management and energy utilization. PMID:26011021
Zhu, Jie; Luo, Yuting; Tian, Jian; Li, Juan; Gao, Xuefeng
2015-05-27
We report that the dropwise condensation heat transfer (DCHT) effectiveness of copper surfaces can be dramatically enhanced by in situ grown clustered ribbed-nanoneedles. Combined experiments and theoretical analyses reveal that, due to the microscopically rugged and low-adhesive nature of building blocks, the nanosamples can not only realize high-density nucleation but constrain growing condensates into suspended microdrops via the self-transport and/or self-expansion mode for subsequently self-propelled jumping, powered by coalescence-released excess surface energy. Consequently, our nanosample exhibits over 125% enhancement in DCHT coefficient. This work helps develop advanced heat-transfer materials and devices for efficient thermal management and energy utilization. PMID:25966966
Development of an efficient solution method for solving the radiative heat transfer equation
Xing Ouyang; Minardi, A.; Kassab, A.
1996-12-31
The radiative heat transfer equation in a participating medium is a Fredholm integral equation of the second kind whose kernels are formally singular at the position where the incident radiation is to be determined. A general method is developed to remove this singularity by capitalizing on the mutual interactions between the source function and the exponential integral appearing in the kernel. The method is based on an interpolation of the unknown source functions, and the analytical integration of the resulting product in the integrand (source function expansion multiplied by the known exponential integral). As such, the method is considered semi-analytical. The method is superior to traditional solution techniques which employ quadratures approximating both the unknown and known functions appearing in the integrand, and which consequently, have numerical difficulties in addressing singularities. The general approach is presented in detail for one-dimensional problems, and extensions to two-dimensional enclosures are also given. One and two-dimensional numerical examples are considered, comparing the predictions to benchmark work. The method is shown to be computationally efficient and highly accurate. In comparison with traditional quadrature based techniques, the method readily handles the singularity of the exponential integral of first order at zero, converges rapidly under grid refinement, and provides superior prediction for radiative heat transfer. The technique is shown to be valid for a wide range of values of the scattering albedo and optical thickness. The proposed technique could be applied to a wide range of conservation problems which lend themselves to an integral formulation.
McGuire, Joseph C.
1982-01-01
A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
Not Available
1980-03-07
A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
NASA Astrophysics Data System (ADS)
Yadav, R. K.; Gastine, T.; Christensen, U. R.; Duarte, L. D. V.; Reiners, A.
2016-02-01
We study rotating thermal convection in spherical shells as prototype for flow in the cores of terrestrial planets, gas planets or in stars. We base our analysis on a set of about 450 direct numerical simulations of the (magneto)hydrodynamic equations under the Boussinesq approximation. The Ekman number ranges from 10-3 to 10-5. The supercriticality of the convection reaches about 1000 in some models. Four sets of simulations are considered: non-magnetic simulations and dynamo simulations with either free-slip or no-slip flow boundary conditions. The non-magnetic setup with free-slip boundaries generates the strongest zonal flows. Both non-magnetic simulations with no-slip flow boundary conditions and self-consistent dynamos with free-slip boundaries have drastically reduced zonal-flows. Suppression of shear leads to a substantial gain in heat-transfer efficiency, increasing by a factor of 3 in some cases. Such efficiency enhancement occurs as long as the convection is significantly influenced by rotation. At higher convective driving the heat-transfer efficiency tends towards that of the classical non-rotating Rayleigh-Bénard system. Analysis of the latitudinal distribution of heat flow at the outer boundary reveals that the shear is most effective at suppressing heat-transfer in the equatorial regions. Simulations with convection zones of different thickness show that the zonal flows become less energetic in thicker shells, and, therefore, their effect on heat-transfer efficiency decreases. Furthermore, we explore the influence of the magnetic field on the non-zonal flow components of the convection. For this we compare the heat-transfer efficiency of no-slip non-magnetic cases with that of the no-slip dynamo simulations. We find that at E = 10-5 magnetic field significantly affects the convection and a maximum gain of about 30 per cent (as compared to the non-magnetic case) in heat-transfer efficiency is obtained for an Elsasser number of about 3. Our analysis
Quenching fundamentals: Heat transfer
MacKenzie, D.S.; Totten, G.E.; Webster, G.M.
1996-12-31
Quenching is essentially a heat transfer problem. It is necessary to quench parts fast enough that adequate mechanical and corrosion properties are achieved, but not so fast that detrimental distortion and residual stresses are formed. In addition, non-uniform heat transfer across the surface of a part will produce thermal gradients which will also create distortion or residual stresses. In this paper, the role of agitation will be discussed in terms of the heat transfer coefficient. A brief review of the published heat transfer literature will be discussed in terms of the fluid flow on heat transfer coefficient, with implications on quenching.
Kurek, Harry; Wagner, John
2010-01-25
Direct Flame Impingement involves the use of an array of very high-velocity flame jets impinging on a work piece to rapidly heat the work piece. The predominant mode of heat transfer is convection. Because of the locally high rate of heat transfer at the surface of the work piece, the refractory walls and exhaust gases of a DFI furnace are significantly cooler than in conventional radiant heating furnaces, resulting in high thermal efficiency and low NOx emissions. A DFI furnace is composed of a successive arrangement of heating modules through or by which the work piece is conveyed, and can be configured for square, round, flat, and curved metal shapes (e.g., billets, tubes, flat bars, and coiled bars) in single- or multi-stranded applications.
Heat transfer in energy problems
NASA Astrophysics Data System (ADS)
Mizushina, T.; Yang, W. J.
Results of recent research are presented concerning heat transfer in energy problems, including high-temperature heat transfer, high-flux heat transfer, high-performance heat transfer, heat transfer in nonconventional energy (power and propulsion) systems, and novel heat transfer techniques. Topics discussed include studies of full-coverage film cooling, radiative properties of metals and alloys at high temperature, critical heat flux conditions in high-quality boiling systems, heat transfer characteristics of the evaporation of a liquid droplet on heated surfaces, high-performance surfaces for non-boiling heat transfer, and high performance heat transfer surfaces for boiling and condensation. Also examined are high flux heat transfer in gaseous solid suspension flow, nuclear process heat applications of high temperature heat exchange, heat transfer considerations in the use of new energy resources, and high performance mist-cooled condensers for geothermal binary cycle plants. No individual items are abstracted in this volume
NASA Technical Reports Server (NTRS)
Burbach, T.
1985-01-01
The heat transfer from hot water to a cold copper pipe in laminar and turbulent flow condition is determined. The mean flow through velocity in the pipe, relative test length and initial temperature in the vessel were varied extensively during tests. Measurements confirm Nusselt's theory for large test lengths in laminar range. A new equation is derived for heat transfer for large starting lengths which agrees satisfactorily with measurements for large starting lengths. Test results are compared with the new Prandtl equation for heat transfer and correlated well. Test material for 200- and to 400-diameter test length is represented at four different vessel temperatures.
Heat transfer fluids containing nanoparticles
Singh, Dileep; Routbort, Jules; Routbort, A.J.; Yu, Wenhua; Timofeeva, Elena; Smith, David S.; France, David M.
2016-05-17
A nanofluid of a base heat transfer fluid and a plurality of ceramic nanoparticles suspended throughout the base heat transfer fluid applicable to commercial and industrial heat transfer applications. The nanofluid is stable, non-reactive and exhibits enhanced heat transfer properties relative to the base heat transfer fluid, with only minimal increases in pumping power required relative to the base heat transfer fluid. In a particular embodiment, the plurality of ceramic nanoparticles comprise silicon carbide and the base heat transfer fluid comprises water and water and ethylene glycol mixtures.
NASA Astrophysics Data System (ADS)
Shin, Sangwoo; Seok Kim, Beom; Choi, Geehong; Lee, Hwanseong; Hee Cho, Hyung
2012-12-01
Micro-nano hybrid structure (MNHS) that comprises of microcavities and nanowires is a specific class of MNHS that is considered to be ideal for two-phase boiling heat transfer applications. Realizing MNHS with electrodeposition is favorable in boiling heat transfer, but the realization has been very difficult and time-consuming to achieve. Here, we demonstrate a simple, robust, rapid, and photolithography-free route to fabricate MNHS that consists of individual microcavities and copper nanowires on a large area. We show that this MNHS can be extremely beneficial in boiling heat transfer compared to the state-of-the-art nanowire surface.
Thermal radiation heat transfer.
NASA Technical Reports Server (NTRS)
Siegel, R.; Howell, J. R.
1972-01-01
A comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation. Among the topics considered are property prediction by electromagnetic theory, the observed properties of solid materials, radiation in the presence of other modes of energy transfer, the equations of transfer for an absorbing-emitting gas, and radiative transfer in scattering and absorbing media. Also considered are radiation exchange between black isothermal surfaces, radiation exchange in enclosures composed of diffuse gray surfaces and in enclosures having some specularly reflecting surfaces, and radiation exchange between nondiffuse nongray surfaces. The use of the Monte Carlo technique in solving radiant-exchange problems and problems of radiative transfer through absorbing-emitting media is explained.
ERIC Educational Resources Information Center
Knapp, Henry H., III
This module on heat transfer is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies. The…
Gambill, W.R.; Greene, N.D.
1960-08-30
A method is given for increasing burn-out heat fluxes under nucleate boiling conditions in heat exchanger tubes without incurring an increase in pumping power requirements. This increase is achieved by utilizing a spinning flow having a rotational velocity sufficient to produce a centrifugal acceleration of at least 10,000 g at the tube wall. At this acceleration the heat-transfer rate at burn out is nearly twice the rate which can be achieved in a similar tube utilizing axial flow at the same pumping power. At higher accelerations the improvement over axial flow is greater, and heat fluxes in excess of 50 x 10/sup 6/ Btu/hr/sq ft can be achieved.
Methane heat transfer investigation
NASA Technical Reports Server (NTRS)
1984-01-01
Future high chamber pressure LOX/hydrocarbon booster engines require copper base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and reusable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper base alloy material adjacent to he fuel coolant. High pressure methane cooling and coking characteristics recently evaluated at Rocketdyne using stainless steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.
Methane heat transfer investigation
NASA Technical Reports Server (NTRS)
Cook, R. T.
1984-01-01
Future high chamber pressure LOX/hydrocarbon booster engines require copper-base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and resuable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper-base alloy material adjacent to the fuel coolant. High-pressure methane cooling and coking characteristics were recently evaluated using stainless-steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper-base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.
Nano materials for efficiently lowering the freezing point of heat transfer nanofluids
NASA Astrophysics Data System (ADS)
Hong, Haiping; Roy, Walter
2007-09-01
In this paper, we report, for the first time, the effect of the lowered freezing point in a 50% water / 50% antifreeze coolant (PAC) or 50% water / 50% ethylene glycol (EG) solution by the addition of carbon nanotubes and other particles. The experimental results indicated that the nano materials are much more efficient (hundreds fold) in lowering the freezing point than the regular ionic materials (e.g. NaCl). The possible explanation for this interesting phenomenon is the colligative property of fluid and relative small size of nano material. It is quite certain that the carbon nanotubes and metal oxide nano particles could be a wonderful candidate for the nano coolant application because they could not only increase the thermal conductivity, but also efficiently lower the freezing point of traditional coolants.
Basmajian, V.V.
1986-01-28
This patent describes a heat transfer apparatus which consists of: heat exchanging means for orientation in the earth below ground substantially vertically, having a hollow conduit of length from top to bottom much greater than the span across the hollow conduit orthogonal to its length with a top, bottom and an intermediate portion contiguous and communicating with the top and bottom portions for allowing thermally conductive fluid to flow freely between the top, intermediate and bottom portions for immersion in thermally conductive fluid in the region around the heat exchanging means for increasing the heat flow between the latter and earth when inserted into a substantially vertical borehole in the earth with the top portion above the bottom portion. The heat exchanger consists of heat exchanging conduit means in the intermediate portion for carrying refrigerant. The heat exchanging conduit consisting of tubes of thermally conductive material for carrying the refrigerant and extending along the length of the hollow conduit for a tube length that is less than the length of the hollow conduit. The hollow conduit is formed with port means between the top and the plurality of tubes for allowing the thermally conductive fluid to pass in a flow path embracing the tubes, the bottom portion, an outer channel around the hollow conduit and the port means.
Transferring heat during a bounce
NASA Astrophysics Data System (ADS)
Shiri, Samira; Bird, James
2015-11-01
When a hot liquid drop impacts a cold non-wetting surface, the temperature difference drives heat transfer. If the drop leaves the surface before reaching thermal equilibrium, the amount of heat transfer may depend on the contact time. Past studies exploring finite-time heat exchange with droplets focus on the Leidenfrost condition where heat transfer is regulated by a thin layer of vapor. Here, we present systematic experiments to measure the heat transferred by a bouncing droplet in non-Leidenfrost conditions. We propose a physical model of this heat transfer and compare our model to the experiments.
Heat-Transfer Coupling For Heat Pipes
NASA Technical Reports Server (NTRS)
Nesmith, Bill J.
1991-01-01
Proposed welded heat-transfer coupling joins set of heat pipes to thermoelectric converter. Design avoids difficult brazing operation. Includes pair of mating flanged cups. Upper cup integral part of housing of thermoelectric converter, while lower cup integral part of plate supporting filled heat pipes. Heat pipes prefilled. Heat of welding applied around periphery of coupling, far enough from heat pipes so it would not degrade working fluid or create excessive vapor pressure in the pipes.
Heat transfer in aeropropulsion systems
NASA Astrophysics Data System (ADS)
Simoneau, R. J.
1985-07-01
Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.
Heat transfer in aeropropulsion systems
NASA Technical Reports Server (NTRS)
Simoneau, R. J.
1985-01-01
Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.
Frank, Jeffrey I.; Rosengart, Axel J.; Kasza, Ken; Yu, Wenhua; Chien, Tai-Hsin; Franklin, Jeff
2006-10-10
Apparatuses, systems, methods, and computer code for, among other things, monitoring the health of samples such as the brain while providing local cooling or heating. A representative device is a heat transfer probe, which includes an inner channel, a tip, a concentric outer channel, a first temperature sensor, and a second temperature sensor. The inner channel is configured to transport working fluid from an inner inlet to an inner outlet. The tip is configured to receive at least a portion of the working fluid from the inner outlet. The concentric outer channel is configured to transport the working fluid from the inner outlet to an outer outlet. The first temperature sensor is coupled to the tip, and the second temperature sensor spaced apart from the first temperature sensor.
"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"
Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann
2008-06-12
ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers
Thermodynamics of Flow Boiling Heat Transfer
NASA Astrophysics Data System (ADS)
Collado, F. J.
2003-05-01
Convective boiling in sub-cooled water flowing through a heated channel is essential in many engineering applications where high heat flux needs to be accommodated. It has been customary to represent the heat transfer by the boiling curve, which shows the heat flux versus the wall-minus-saturation temperature difference. However it is a rather complicated problem, and recent revisions of two-phase flow and heat transfer note that calculated values of boiling heat transfer coefficients present many uncertainties. Quite recently, the author has shown that the average thermal gap in the heated channel (the wall temperature minus the average temperature of the coolant) was tightly connected with the thermodynamic efficiency of a theoretical reversible engine placed in this thermal gap. In this work, whereas this correlation is checked again with data taken by General Electric (task III) for water at high pressure, a possible connection between this wall efficiency and the reversible-work theorem is explored.
Conduction heat transfer solutions
VanSant, J.H.
1983-08-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.
Conduction heat transfer solutions
VanSant, J.H.
1980-03-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references.
Tubing for augmented heat transfer
Yampolsky, J.S.; Pavlics, P.
1983-08-01
The objectives of the program reported were: to determine the heat transfer and friction characteristics on the outside of spiral fluted tubing in single phase flow of water, and to assess the relative cost of a heat exchanger constructed with spiral fluted tubing with one using conventional smooth tubing. An application is examined where an isolation water/water heat exchanger was used to transfer the heat from a gaseous diffusion plant to an external system for energy recovery. (LEW)
Efficient transfer of francium atoms
NASA Astrophysics Data System (ADS)
Aubin, Seth; Behr, John; Gorelov, Alexander; Pearson, Matt; Tandecki, Michael; Collister, Robert; Gwinner, Gerald; Shiells, Kyle; Gomez, Eduardo; Orozco, Luis; Zhang, Jiehang; Zhao, Yanting; FrPNC Collaboration
2016-05-01
We report on the progress of the FrPNC collaboration towards Parity Non Conservation Measurements (PNC) using francium atoms at the TRIUMF accelerator. We demonstrate efficient transfer (higher than 40%) to the science vacuum chamber where the PNC measurements will be performed. The transfer uses a downward resonant push beam from the high-efficiency capture magneto optical trap (MOT) towards the science chamber where the atoms are recaptured in a second MOT. The transfer is very robust with respect to variations in the parameters (laser power, detuning, alignment, etc.). We accumulate a growing number of atoms at each transfer pulse (limited by the lifetime of the MOT) since the push beam does not eliminate the atoms already trapped in the science MOT. The number of atoms in the science MOT is on track to meet the requirements for competitive PNC measurements when high francium rates (previously demonstrated) are delivered to our apparatus. The catcher/neutralizer for the ion beam has been tested reliably to 100,000 heating/motion cycles. We present initial tests on the direct microwave excitation of the ground hyperfine transition at 45 GHz. Support from NSERC and NRC from Canada, NSF and Fulbright from USA, and CONACYT from Mexico.
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.
Fraas, A.P.; Wislicenus, G.F.
1961-07-11
A heat exchanger is adapted to unifomly cool a spherical surface. Equations for the design of a spherical heat exchanger hav~g tubes with a uniform center-to-center spining are given. The heat exchanger is illustrated in connection with a liquid-fueled reactor.
NASA Astrophysics Data System (ADS)
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-07-01
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-01-01
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body. PMID:26189698
NASA Technical Reports Server (NTRS)
Widener, Edward L.
1992-01-01
The objective is to introduce some concepts of thermodynamics in existing heat-treating experiments using available items. The specific objectives are to define the thermal properties of materials and to visualize expansivity, conductivity, heat capacity, and the melting point of common metals. The experimental procedures are described.
NASA Technical Reports Server (NTRS)
Friedell, M. V.; Anderson, A. J.
1974-01-01
Thermal switch maintains temperature of planetary lander, within definite range, by transferring heat. Switch produces relatively large stroke and force, uses minimum electrical power, is lightweight, is vapor pressure actuated, and withstands sterilization temperatures without damage.
Heat transfer, diffusion, and evaporation
NASA Technical Reports Server (NTRS)
Nusselt, Wilhelm
1954-01-01
Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.
Heat exchanger with heat transfer control
Wiard, M.R.
1986-11-18
This patent describes a multi-sided plate and fin type heat exchanger core in which plate elements, intermediately positioning spacer elements and fin strips are stacked in a layered assembly providing fluid passages for different fluids to flow in a segregated heat transfer relation to one another. The core is characterized in that at certain locations in a stacked assembly layers include spacer elements substantially closing all sides of the heat exchangers to define between adjacent fluid passages layers of increased heat transfer resistance. The fin strips are sheet-like elements corrugated to forms specifically identifiable in terms of fins per inch, there being fin strips in at least certain resistance layers differing in terms of fins per inch from other strips in certain resistance layers.
Heat transfer from oriented heat exchange areas
NASA Astrophysics Data System (ADS)
Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej
2014-03-01
This paper deals with the transfer of heat-driven heat transfer surface area in relation to the construction of the criterion equation for "n" horizontal pipe one about another. On the bases of theoretical models have been developed for calculating the thermal performance of natural convection by Churilla and Morgan, for various pipe diameters and temperatures. These models were compared with models created in CFD-Fluent Ansys the same boundary conditions. The aim of the analyse of heat and fluxional pipe fields "n" pipes one about another at natural convection is the creation of criterion equation on the basis of which the heat output of heat transfer from pipe oriented areas one above another with given spacing could be quantified. At presence a sum of criterion equations exists for simple geometrical shapes of individual oriented geometrical areas but the criterion equation which would consider interaction of fluxional field generated by free convection from multiple oriented areas is not mentioned in standardly accessible technical literature and other magazine publications.
Heat transfer characteristics for disk fans
NASA Astrophysics Data System (ADS)
Prikhodko, Yu. M.; Chekhov, V. P.; Fomichev, V. P.
2014-08-01
Multiple-disk fans belong to the class of friction machines; they can be designed in two variants: centrifugal disk fans and diametrical disk fans. Flow patterns in these two types of machines are different, and they possess different heat transfer characteristics. The paper presents results of experimental study for a centrifugal disk fan under atmospheric pressure with air taken as working gas. The radial temperature distribution for a disk was obtained at different rotation speed of the rotor and different heating of the disks. Heat transfer characteristics of a centrifugal disk fan and a diametrical disk fan were compared. The research results demonstrate a higher heat transfer efficiency for centrifugal design versus diametrical disk design.
Nanofluid impingement jet heat transfer.
Zeitoun, Obida; Ali, Mohamed
2012-01-01
Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669
Nanofluid impingement jet heat transfer
2012-01-01
Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669
Examination of Liquid Fluoride Salt Heat Transfer
Yoder Jr, Graydon L
2014-01-01
The need for high efficiency power conversion and energy transport systems is increasing as world energy use continues to increase, petroleum supplies decrease, and global warming concerns become more prevalent. There are few heat transport fluids capable of operating above about 600oC that do not require operation at extremely high pressures. Liquid fluoride salts are an exception to that limitation. Fluoride salts have very high boiling points, can operate at high temperatures and low pressures and have very good heat transfer properties. They have been proposed as coolants for next generation fission reactor systems, as coolants for fusion reactor blankets, and as thermal storage media for solar power systems. In each case, these salts are used to either extract or deliver heat through heat exchange equipment, and in order to design this equipment, liquid salt heat transfer must be predicted. This paper discusses the heat transfer characteristics of liquid fluoride salts. Historically, heat transfer in fluoride salts has been assumed to be consistent with that of conventional fluids (air, water, etc.), and correlations used for predicting heat transfer performance of all fluoride salts have been the same or similar to those used for water conventional fluids an, water, etc). A review of existing liquid salt heat transfer data is presented, summarized, and evaluated on a consistent basis. Less than 10 experimental data sets have been found in the literature, with varying degrees of experimental detail and measured parameters provided. The data has been digitized and a limited database has been assembled and compared to existing heat transfer correlations. Results vary as well, with some data sets following traditional correlations; in others the comparisons are less conclusive. This is especially the case for less common salt/materials combinations, and suggests that additional heat transfer data may be needed when using specific salt eutectics in heat transfer
Experimental Investigations of Heat and Mass Transfer in Microchannel Heat-Transfer Elements
NASA Astrophysics Data System (ADS)
Konovalov, D. A.
2016-06-01
The present work seeks to develop and investigate experimentally microchannel heat-exchange apparatuses of two designs: with porous elements manufactured from titanium and copper, and also based on the matrix of filamentary silicon single crystals under operating conditions with high heat loads, unsteadiness, and nonlinear flow of the coolant. For experimental investigations, the authors have developed and manufactured a unique test bench allowing tests of the developed heat-transfer elements in unsteady operating regimes. The performed experimental investigations have made it possible to obtain criterial dependences of the heat-transfer coefficient on the Reynolds and Prandtl numbers and to refine the values of viscous and inertial coefficients. It has been established that microchannel heat-transfer elements based on silicon single crystals, which make it possible to remove a heat flux above 100 W/cm2, are the most efficient. For porous heat-transfer elements, the best result was attained for wedge-shaped copper samples. According to investigation results, the authors have considered the issues of optimization of thermal and hydraulic characteristics of the heat-transfer elements under study. In the work, the authors have given examples of practical use of the developed heat-transfer elements for cooling systems of radioelectronic equipment.
Experimental Investigations of Heat and Mass Transfer in Microchannel Heat-Transfer Elements
NASA Astrophysics Data System (ADS)
Konovalov, D. A.
2016-05-01
The present work seeks to develop and investigate experimentally microchannel heat-exchange apparatuses of two designs: with porous elements manufactured from titanium and copper, and also based on the matrix of filamentary silicon single crystals under operating conditions with high heat loads, unsteadiness, and nonlinear flow of the coolant. For experimental investigations, the authors have developed and manufactured a unique test bench allowing tests of the developed heat-transfer elements in unsteady operating regimes. The performed experimental investigations have made it possible to obtain criterial dependences of the heat-transfer coefficient on the Reynolds and Prandtl numbers and to refine the values of viscous and inertial coefficients. It has been established that microchannel heat-transfer elements based on silicon single crystals, which make it possible to remove a heat flux above 100 W/cm2, are the most efficient. For porous heat-transfer elements, the best result was attained for wedge-shaped copper samples. According to investigation results, the authors have considered the issues of optimization of thermal and hydraulic characteristics of the heat-transfer elements under study. In the work, the authors have given examples of practical use of the developed heat-transfer elements for cooling systems of radioelectronic equipment.
NASA Astrophysics Data System (ADS)
Chapman, K. S.; Ramadhyani, S.; Ramamurthy, H.; Viskanta, R.
1990-04-01
One and two-dimensional mathematical models have been developed to predict the steady state thermal performance and combustion characteristics of a natural gas-fired straight-through radiant tube. The effects of burner geometry, equivalence ratio, and preheat temperature and fuel firing rate on fuel burn-up have been investigated. The one-dimensional models for straight-through and single-ended recuperative radiant tubes have been validated using available experimental data. Thermal system models have been developed for the continuous and batch indirectly fired (radiant tube) furnaces to identify opportunities for fuel savings and enhanced productivity. Extensive parametric investigations were performed to examine the effects of load and refractory emissivities, load throughput rate and thickness on the thermal performance of the furnaces. Batch and continuous direct-fired furnace thermal system models were developed to analyze the effect of various design and operation parameters on the furnace thermal performance. An attempt was made to validate the batch furnace model by using experimental data from a small experimental furnace. Due to the size of the furnace, the two-dimensional heat conduction effects near the corners and edges of the furnace walls were significant. Since the effects were neglected in the system model, which is intended to simulate a large industrial furnace, the validation was unsuccessful. The parametric study consisted of examining the effect of the load and refractory emissivities and other operating and load parameters on the thermal performance of the batch and continuous furnaces.
Boost Process Heating Efficiency - PHAST
2005-05-01
Use the Process Heating Assessment and Survey Tool (PHAST) to survey all process heating equipment within a facility, select the equipment that uses the most energy, and identify ways to increase efficiency.
Coolant passage heat transfer with rotation
NASA Astrophysics Data System (ADS)
Hajek, T. J.; Wagner, J.; Johnson, B. V.
1986-10-01
In current and advanced gas turbine engines, increased speeds, pressures and temperatures are used to reduce specific fuel consumption and increase thrust/weight ratios. Hence, the turbine airfoils are subjected to increased heat loads escalating the cooling requirements to satisfy life goals. The efficient use of cooling air requires that the details of local geometry and flow conditions be adequately modeled to predict local heat loads and the corresponding heat transfer coefficients. The objective of this program is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.
Sodium heat transfer system modeling
NASA Astrophysics Data System (ADS)
Baker, A. F.; Fewell, M. E.
1983-11-01
The sodium heat transfer system of the international energy agency (IEA) small solar power systems (SSPS) central receiver system (CRS), which includes the heliostat field, receiver, hot and cold storage vessels, and sodium/water steam generator was modeled. The computer code SOLTES (simulator of large thermal energy systems), was used to model this system. The results from SOLTES are compared to measured data.
Host turbine heat transfer overview
NASA Technical Reports Server (NTRS)
Rohde, J. E.
1984-01-01
Improved methods of predicting airfoil local metal temperatures require advances in the understanding of the physics and methods of analytically predicting the following four aerothermal loads: hot gas flow over airfoils, heat transfer rates on the gas-side of airfoils, cooling air flow inside airfoils, and heat transfer rates on the coolant-side of airfoils. A systematic building block research approach is being pursued to investigate these four areas of concern from both the experimental and analytical sides. Experimental approaches being pursued start with fundamental experiments using simple shapes and flat plates in wind tunnels, progress to more realistic cold and hot cascade tests using airfoils, continue to progress in large low-speed rigs and turbines and warm turbines, and finally, combine all the interactive effects in tests using real engines or real engine type turbine rigs. Analytical approaches being pursued also build from relatively simple steady two dimensional inviscid flow and boundary layer heat transfer codes to more advanced steady two and three dimensional viscous flow and heat transfer codes. These advanced codes provide more physics to model better the interactive effects and the true real-engine environment.
Enhancement of heat transfer in waste-heat heat exchangers
NASA Astrophysics Data System (ADS)
Stoeffler, R. C.
1980-07-01
The Fluidfire shallow fluidized bed heat transfer facility was modified to give increased air flow capacity and to allow testing with different distributor plates and with two stage heat exchangers. The effect of reduced distributor plate pressure loss and amount and type of bed material on the heat transfer performance of a single stage fluidized bed heat exchanger is explored. Elutriation from the bed was measured for different bed materials and distributor plates; alternate heat exchanger surfaces having different fin spacings were also tested. Two types of two stage fluidized bed heat exchangers were tested: one having a baffle (having almost no pressure loss) located between the stages and which allowed bed material to recirculate between upper and lower beds; the second having two distributor plates in series with no recirculation of the bed material.
Experimental research on heat transfer of pulsating heat pipe
NASA Astrophysics Data System (ADS)
Li, Jia; Yan, Li
2008-06-01
Experimental research was conducted to understand heat transfer characteristic of pulsating heat pipe in this paper, and the PHP is made of high quality glass capillary tube. Under different fill ratio, heat transfer rate and many other influence factors, the flow patterns were observed in the start-up, transition and stable stage. The effects of heating position on heat transfer were discussed. The experimental results indicate that no annular flow appears in top heating condition. Under different fill ratios and heat transfer rate, the flow pattern in PHP is transferred from bulk flow to semi-annular flow and annular flow, and the performance of heat transfer is improved for down heating case. The experimental results indicate that the total heat resistant of PHP is increased with fill ratio, and heat transfer rate achieves optimum at filling rate 50%. But for pulsating heat pipe with changing diameters the thermal resistance is higher than that with uniform diameters.
Heat transfer in aerospace propulsion
NASA Technical Reports Server (NTRS)
Simoneau, Robert J.; Hendricks, Robert C.; Gladden, Herbert J.
1988-01-01
Presented is an overview of heat transfer related research in support of aerospace propulsion, particularly as seen from the perspective of the NASA Lewis Research Center. Aerospace propulsion is defined to cover the full spectrum from conventional aircraft power plants through the Aerospace Plane to space propulsion. The conventional subsonic/supersonic aircraft arena, whether commercial or military, relies on the turbine engine. A key characteristic of turbine engines is that they involve fundamentally unsteady flows which must be properly treated. Space propulsion is characterized by very demanding performance requirements which frequently push systems to their limits and demand tailored designs. The hypersonic flight propulsion systems are subject to severe heat loads and the engine and airframe are truly one entity. The impact of the special demands of each of these aerospace propulsion systems on heat transfer is explored.
Heat transfer reviews 1976-1986
NASA Astrophysics Data System (ADS)
Eckert, Ernst Rudolf Georg; Goldstein, R. J.; Irvine, T. F., Jr.; Hartnett, J. P.
Theoretical and experimental investigations of heat-transfer phenomena are surveyed in a collection of annual review essays. The reviews were originally published in the International Journal of Heat and Mass Transfer. Cumulative author and subject indices are provided.
Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants
NASA Astrophysics Data System (ADS)
Yoshida, Suguru; Fujita, Yasunobu
The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.
Cueff, Sebastien; Labbe, Christophe; Cardin, Julien; Doualan, Jean-Louis; Khomenkova, Larysa; Hijazi, Khalil; Rizk, Richard
2010-09-15
This study investigates the influence of the deposition temperature T{sub d} on the Si-mediated excitation of Er ions within silicon-rich silicon oxide layers obtained by magnetron cosputtering. For T{sub d} exceeding 200 deg. C, an efficient indirect excitation of Er ions is observed for all as-deposited samples. The photoluminescence intensity improves gradually up to a maximum at T{sub d}=600 deg. C before decreasing for higher T{sub d} values. The effects of this ''growth-induced annealing'' are compared to those resulting from the same thermal budget used for the ''classical'' approach of postdeposition annealing performed after a room temperature deposition. It is demonstrated that the former approach is highly beneficial, not only in terms of saving time but also in the fourfold enhancement of the Er photoluminescence efficiency.
Nonlinear Heat Transfer 2d Structure
Energy Science and Technology Software Center (ESTSC)
1987-09-01
DOT-BPMD is a general-purpose, finite-element, heat-transfer program used to predict thermal environments. The code considers linear and nonlinear transient or steady-state heat conduction in two-dimensional planar or axisymmetric representations of structures. Capabilities are provided for modeling anisotropic heterogeneous materials with temperature-dependent thermal properties and time-dependent temperature, heat flux, convection and radiation boundary conditions, together with time-dependent internal heat generation. DOT-BPMD may be used in the evaluation of steady-state geothermal gradients as well as in themore » transient heat conduction analysis of repository and waste package subsystems. Strengths of DOT-BPMD include its ability to account for a wide range of possible boundary conditions, nonlinear material properties, and its efficient equation solution algorithm. Limitations include the lack of a three-dimensional analysis capability, no radiative or convective internal heat transfer, and the need to maintain a constant time-step in each program execution.« less
Heat transfer in GTA welding arcs
NASA Astrophysics Data System (ADS)
Huft, Nathan J.
Heat transfer characteristics of Gas Tungsten Arc Welding (GTAW) arcs with arc currents of 50 to 125 A and arc lengths of 3 to 11 mm were measured experimentally through wet calorimetry. The data collected were used to calculate how much heat reported to the cathode and anode and how much was lost from the arc column. A Visual Basic for Applications (VBA) macro was written to further analyze the data and account for Joule heating within the electrodes and radiation and convection losses from the arc, providing a detailed account of how heat was generated and dissipated within the system. These values were then used to calculate arc efficiencies, arc column voltages, and anode and cathode fall voltages. Trends were noted for variances in the arc column voltage, power dissipated from the arc column, and the total power dissipated by the system with changing arc length. Trends for variances in the anode and cathode fall voltages, total power dissipated, Joule heating within the torches and electrodes with changing arc current were also noted. In addition, the power distribution between the anode and cathode for each combination of arc length and arc current was examined. Keywords: Gas Tungsten Arc Welding, GTAW, anode fall, cathode fall, heat transfer, wet calorimetry
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P.
2012-07-24
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2015-03-24
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2013-12-10
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P.
2015-12-08
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Heat Transfer in a Thermoacoustic Process
ERIC Educational Resources Information Center
Beke, Tamas
2012-01-01
Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…
Heat transfer and planetary evolution
NASA Astrophysics Data System (ADS)
Tozer, D. C.
1985-06-01
The object of this account is to show how much one can interprete and predict about the present state of material forming planet size objects, despite the fact we do not and could never have the kind of exact or prior knowledge of initial conditions and in situ material behaviour that would make a formal mathematical analysis of the dynamical problems of planetary evolution an efficient or meaningful exercise The interest and usefulness of results obtained within these limitations stem from the highly non linear nature of planetary scale heat transfer problems when posed in any physically plausible form. The non linearity arising from a strongly temperature dependent rheology assumed for in situ planetary material is particularly valuable in deriving results insensitive to such uncertainties. Qualitatively, the thermal evolution of a planet is quite unlike that given by heat conduction calculation below a very superficial layer, and much unnecessary argument and confusion results from a persistent failure to recognise that fact. At depths that are no greater on average than a few tens of kilometres in the case of Earth, the temperature distribution is determined by a convective flow regime inaccessble to the laboratory experimenter and to the numerical methods regularly employed to study convective movement. A central and guiding quantitative result is the creation in homogeneous planet size objects having surface temperatures less than about half the absolute melting temperature of their material, of internal states with horizontally a veraged viscosity values ˜1021 poise. This happens in times short compared with the present Solar System age. The significance of this result for an understanding of such processes and features as isostasy, continental drift, a minimum in seismic S wave velocity in Earth's upper mantle, a uniformity of mantle viscosity values, the survival of liquid planetary cores and the differentiation of terrestrial planet material is examined
Combustion and heat transfer in porous media
Sathe, S.B.; Peck, R.E.; Tong, T.W.
1990-06-01
The objective of the present study is to generate fundamental knowledge about heat transfer and combustion in porous radiant burners (PRBs) in order to improve their performance. A theoretical heat transfer and combustion model is developed to study the characteristics of PRBs. The model accounts for non-local thermal equilibrium between the solid and gas phases. The solid is assumed to absorb, emit and scatter radiant energy. Combustion is modeled as a one-step global reaction. It is revealed that the flame speed inside the porous medium is enhanced compared to the adiabatic flame speeds due to the higher conductivity of the solid compared to the gas as well as due to radiative preheating of the reactants. The effects of the properties of the porous material on the flame speeds, radiative outputs and efficiencies were investigated. To improve the radiative output from the burner, it is desirable that the porous layer has an optical thickness of about ten. The radiative output and the efficiency is higher for lower scattering albedo. The heat transfer coupling between the solid and gas phases should be high enough to ensure local thermal equilibrium, by choosing a fine porous matrix. Higher solid phase conduction enhances the flame speed and the radiative output. Experiments are performed on a ceramic foam to verify the theoretical findings. The existence of the two stability regions was verified experimentally.
Liquid metal heat transfer issues
Hoffman, H.W.; Yoder, G.L.
1984-01-01
An alkali liquid metal cooled nuclear reactor coupled with an alkali metal Rankine cycle provides a practicable option for space systems/missions requiring power in the 1 to 100 MW(e) range. Thermal issues relative to the use of alkali liquid metals for this purpose are identified as these result from the nature of the alkali metal fluid itself, from uncertainties in the available heat transfer correlations, and from design and performance requirements for system components operating in the earth orbital microgravity environment. It is noted that, while these issues require further attention to achieve optimum system performance, none are of such magnitude as to invalidate this particular space power concept.
Efficiency of Brownian heat engines.
Derényi, I; Astumian, R D
1999-06-01
We study the efficiency of one-dimensional thermally driven Brownian ratchets or heat engines. We identify and compare the three basic setups characterized by the type of the connection between the Brownian particle and the two heat reservoirs: (i) simultaneous, (ii) alternating in time, and (iii) position dependent. We make a clear distinction between the heat flow via the kinetic and the potential energy of the particle, and show that the former is always irreversible and it is only the third setup where the latter is reversible when the engine works quasistatically. We also show that in the third setup the heat flow via the kinetic energy can be reduced arbitrarily, proving that even for microscopic heat engines there is no fundamental limit of the efficiency lower than that of a Carnot cycle. PMID:11969723
Heat-Transfer Head For Stirling-Cycle Machine
NASA Technical Reports Server (NTRS)
Emigh, Stuart G.; Lehmann, Gregory A.; Noble, Jack E.
1995-01-01
New common heat-transfer head for two cylinders of opposed-cylinder Stirling-cycle machine performs function formerly performed by two heat acceptors-one for each cycle. Simplifies structure of machine and increases efficiency of operation by reducing resistance to flow of working gas and/or increasing transfer of heat to or from working gas during flow between compression and expansion spaces of machine.
Heat Transfer in Complex Fluids
Mehrdad Massoudi
2012-01-01
(linear) behavior for a given range of parameters or geometries; there are many empirical or semi-empirical constitutive equations suggested for these fluids. There have also been many non-linear constitutive relations which have been derived based on the techniques of continuum mechanics. The non-linearities oftentimes appear due to higher gradient terms or time derivatives. When thermal and or chemical effects are also important, the (coupled) momentum and energy equations can give rise to a variety of interesting problems, such as instability, for example the phenomenon of double-diffusive convection in a fluid layer. In Conclusion, we have studied the flow of a compressible (density gradient type) non-linear fluid down an inclined plane, subject to radiation boundary condition. The heat transfer is also considered where a source term, similar to the Arrhenius type reaction, is included. The non-dimensional forms of the equations are solved numerically and the competing effects of conduction, dissipation, heat generation and radiation are discussed. It is observed that the velocity increases rapidly in the region near the inclined surface and is slower in the region near the free surface. Since R{sub 7} is a measure of the heat generation due to chemical reaction, when the reaction is frozen (R{sub 7}=0.0) the temperature distributions would depend only on R{sub 1}, and R{sub 2}, representing the effects of the pressure force developed in the material due to the distribution, R{sub 3} and R{sub 4} viscous dissipation, R{sub 5} the normal stress coefficient, R{sub 6} the measure of the emissivity of the particles to the thermal conductivity, etc. When the flow is not frozen (RP{sub 7} > 0) the temperature inside the flow domain is much higher than those at the inclined and free surfaces. As a result, heat is transferred away from the flow toward both the inclined surface and the free surface with a rate that increases as R{sub 7} increases. For a given temperature, an
Heat transfer in circulating fluidized bed combustor
Bucak, O.; Dogan, O.M.; Uysal, B.Z.
1999-07-01
The importance of fluidized bed combustion in utilizing the energy of especially low quality coals is widely accepted. Among various fluidized bed combustion technologies, circulating fluidized beds are preferred as a result of the efforts to get higher combustion efficiencies. The aim of the present research was to investigate the applicability of this technology to Turkish lignites. To achieve this object a 6.5 m tall pilot circulating fluidized bed combustor with 155 mm diameter and all the auxiliary equipment were designed, constructed and tested using Seyitomer lignite of 0.9--2.38 mm in size. Heat transfer from the bed to the water cooling jackets was examined to recover the combustion energy. The inside heat transfer coefficient was determined to be around 121 W/m{sup 2} K for the suspension density of 20--55 kg/m{sup 3}. The agreement of the experimental findings with theoretical estimations was also checked. Furthermore, the thermal efficiency of the system for the heat recovered was found to be 63%.
NASA Technical Reports Server (NTRS)
Garg, Vijay K.
2001-01-01
The turbine gas path is a very complex flow field. This is due to a variety of flow and heat transfer phenomena encountered in turbine passages. This manuscript provides an overview of the current work in this field at the NASA Glenn Research Center. Also, based on the author's preference, more emphasis is on the computational work. There is much more experimental work in progress at GRC than that reported here. While much has been achieved, more needs to be done in terms of validating the predictions against experimental data. More experimental data, especially on film cooled and rough turbine blades, are required for code validation. Also, the combined film cooling and internal cooling flow computation for a real blade is yet to be performed. While most computational work to date has assumed steady state conditions, the flow is clearly unsteady due to the presence of wakes. All this points to a long road ahead. However, we are well on course.
Twin reservoir heat transfer circuit
Urch, J.F.
1986-09-23
This patent describes a heat transfer means comprising circuitry defining a closed flow path for working fluid; a primary circuit forming part of the path and having two ends at one of which the working fluid is at a high pressure and at the other of which the working fluid is at a low pressure. The circuitry defines a fluid supply reservoir and a fluid collection reservoir disposed respectively at the two ends; ejector means in the primary circuit; a drive fluid inlet, and exhaust outlet and a suction inlet provided on the ejector means. Also included are a branch circuit bridging a section of the primary circuit and an outlet end of the branch circuit connected to the suction inlet of the ejector means.
Recovering waste industrial heat efficiently
Hnat, J.G.; Bartone, L.M.; Cutting, J.C.; Patten, J.S.
1983-03-01
Organic Rankine Cycles (ORC's) are being used in the generation of electrical or mechanical power in situations where little demand exists for process steam. Using organic fluids in Rankine cycles improves the potential for economic recovery of waste heat. The right organic fluid can enhance the conversion efficiency by tailoring the ORC heat recovery cycle to the thermodynamic characteristics of the waste heat stream. The selection of the working fluid is affected by its flammability, toxicity, environmental impact, materials compatibility, and cost. Water, ethanol, 2-methyl Pyridine/H2O, Flourinol, Toluene, Freon R-11, and Freon R-113 are compared. An organic cycle using toluene as the working fluid is schematicized.
A Compact Remote Heat Transfer Device for Space Cryocoolers
NASA Astrophysics Data System (ADS)
Yan, T.; Zhao, Y.; Liang, T.
In this paper a compact remote heat transfer device (CRHD) for cryocoolers is proposed. This device is especially attractive in cases where cryocoolers are not easy to set near the heat source, generally the infrared sensor. The CRHD is designed on basis of the concept of loop heat pipes, while the primary evaporator is located near the cryocooler cold head and a simple tube-in-tube secondary evaporator is remotely located and thermally connected with the heat source for cooling. With such a device a cooling power of 1 W is achieved across a heat transfer distance of about 2 m. The major problem of this device is the low heat transfer efficiency (1 W of net cooling power at the cost of about 7 W of cooling power from the cryocooler), and in the future a secondary wicked evaporator will be used instead of the tube-in-tube evaporator in order to improve the efficiency.
Conjugate heat transfer with the entropic lattice Boltzmann method
NASA Astrophysics Data System (ADS)
Pareschi, G.; Frapolli, N.; Chikatamarla, S. S.; Karlin, I. V.
2016-07-01
A conjugate heat-transfer model is presented based on the two-population entropic lattice Boltzmann method. The present approach relies on the extension of Grad's boundary conditions to the two-population model for thermal flows, as well as on the appropriate exact conjugate heat-transfer condition imposed at the fluid-solid interface. The simplicity and efficiency of the lattice Boltzmann method (LBM), and in particular of the entropic multirelaxation LBM, are retained in the present approach, thus enabling simulations of turbulent high Reynolds number flows and complex wall boundaries. The model is validated by means of two-dimensional parametric studies of various setups, including pure solid conduction, conjugate heat transfer with a backward-facing step flow, and conjugate heat transfer with the flow past a circular heated cylinder. Further validations are performed in three dimensions for the case of a turbulent flow around a heated mounted cube.
Conjugate heat transfer with the entropic lattice Boltzmann method.
Pareschi, G; Frapolli, N; Chikatamarla, S S; Karlin, I V
2016-07-01
A conjugate heat-transfer model is presented based on the two-population entropic lattice Boltzmann method. The present approach relies on the extension of Grad's boundary conditions to the two-population model for thermal flows, as well as on the appropriate exact conjugate heat-transfer condition imposed at the fluid-solid interface. The simplicity and efficiency of the lattice Boltzmann method (LBM), and in particular of the entropic multirelaxation LBM, are retained in the present approach, thus enabling simulations of turbulent high Reynolds number flows and complex wall boundaries. The model is validated by means of two-dimensional parametric studies of various setups, including pure solid conduction, conjugate heat transfer with a backward-facing step flow, and conjugate heat transfer with the flow past a circular heated cylinder. Further validations are performed in three dimensions for the case of a turbulent flow around a heated mounted cube. PMID:27575234
Radiative heat transfer in porous uranium dioxide
Hayes, S.L.
1992-12-01
Due to low thermal conductivity and high emissivity of UO{sub 2}, it has been suggested that radiative heat transfer may play a significant role in heat transfer through pores of UO{sub 2} fuel. This possibility was computationally investigated and contribution of radiative heat transfer within pores to overall heat transport in porous UO{sub 2} quantified. A repeating unit cell was developed to model approximately a porous UO{sub 2} fuel system, and the heat transfer through unit cells representing a wide variety of fuel conditions was calculated using a finite element computer program. Conduction through solid fuel matrix as wekk as pore gas, and radiative exchange at pore surface was incorporated. A variety of pore compositions were investigated: porosity, pore size, shape and orientation, temperature, and temperature gradient. Calculations were made in which pore surface radiation was both modeled and neglected. The difference between yielding the integral contribution of radiative heat transfer mechanism to overall heat transport. Results indicate that radiative component of heat transfer within pores is small for conditions representative of light water reactor fuel, typically less than 1% of total heat transport. It is much larger, however, for conditions present in liquid metal fast breeder reactor fuel; during restructuring of this fuel type early in life, the radiative heat transfer mode was shown to contribute as much as 10-20% of total heat transport in hottest regions of fuel.
Low heat transfer oxidizer heat exchanger design and analysis
NASA Technical Reports Server (NTRS)
Kanic, P. G.; Kmiec, T. D.; Peckham, R. J.
1987-01-01
The RL10-IIB engine, a derivative of the RLIO, is capable of multi-mode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2 percent of full thrust, and pumped idle (PI), which is 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for log-g deployment. Stable combustion of the RL10-IIB engine at THI and PI thrust levels can be accomplished by providing gaseous oxygen at the propellant injector. Using gaseous hydrogen from the thrust chamber jacket as an energy source, a heat exchanger can be used to vaporize liquid oxygen without creating flow instability. This report summarizes the design and analysis of a United Aircraft Products (UAP) low-rate heat transfer heat exchanger concept for the RL10-IIB rocket engine. The design represents a second iteration of the RL10-IIB heat exchanger investigation program. The design and analysis of the first heat exchanger effort is presented in more detail in NASA CR-174857. Testing of the previous design is detailed in NASA CR-179487.
Flow characteristics and heat transfer in wavy walled channels
NASA Astrophysics Data System (ADS)
Mills, Zachary; Shah, Tapan; Monts, Vontravis; Warey, Alok; Balestrino, Sandro; Alexeev, Alexander
2013-11-01
Using lattice Boltzmann simulations, we investigated the effects of wavy channel geometry on the flow and heat transfer within a parallel plate heat exchanger. We observed three distinct flow regimes that include steady flow with and without recirculation and unsteady time-periodic flow. We determined the critical Reynolds numbers at which the flow transitions between different flow regimes. To validate our computational results, we compared the simulated flow structures with the structures observed in a flowing soap film. Furthermore, we examine the effects of the wavy channel geometry on the heat transfer. We find that the unsteady flow regime drastically enhances the rate of heat transfer and show that heat exchangers with wavy walls outperform currently used heat exchangers with similar volume and power characteristics. Results from our study point to a simple and efficient method for increasing performance in compact heat exchangers.
Thermodynamics of flame impingement heat transfer
NASA Astrophysics Data System (ADS)
Som, S. K.; Agrawal, G. K.; Chakraborty, Suman
2007-08-01
A theoretical model for entropy generation and utilization of work potential (exergy) in flame impingement (both premixed and diffusion) heat transfer has been developed in this article, to offer physical insights on the optimal operational regimes, depicting high values of the surface heat flux with minimal exergy destruction, within the practical constraints. The irreversibility components due to different physical processes have been evaluated from a general entropy transport equation. The velocity, temperature, and species concentration fields required for the solution of entropy transport equation have been determined from the numerical computation of flow-field in the flame. Global two-step chemical kinetics has been considered with methane (CH4) and air as fuel and oxidizer, respectively. The results have been predicted in terms of average nondimensional heat flux, expressed as Nusselt number at the target plate, the irreversibility components, and second law efficiency, as functions of the pertinent input parameters such as the jet Reynolds number and the ratio of plate separation distance to nozzle diameter (H /d). The average Nusselt number has been found to increase with an increase in jet Reynolds number and a decrease in H /d ratio, up to a value of 8. The dominant source of thermodynamic irreversibility in a premixed flame has been attributed to the thermal energy exchange whereas, in a diffusion flame, the same has been attributed to an uncontrolled exchange of electrons accompanying the reactive kinetics. The second law efficiency has been found to increase with an increase in jet Reynolds number and an increase in the H /d ratio, up to a value of 20. Values of the jet Reynolds number greater than 10 000 and H /d ratio in the tune of 15 have been observed to pertain to the regime of optimum flame impingement heat transfer, consistent with the energy and exergy balance constraints.
Radiation heat transfer in two-phase media
Adzerikho, K.S.
1988-05-01
The state of the art of approximate and numerical methods of the theory of radiation heat transfer is analyzed. The principles for producing engineering methods of computing the radiation heat-transfer characteristics in power plants are examined. These principles include: the integration of the transport equation, computing the radiation heat transfer in nonisothermal two-phase media bounded by emitting and reflecting surfaces, the thermal efficiency of screens as a function of the optical properties of the boundary surfaces and the furnace medium, the scattering processes, temperature distribution, and a program NOTAK in the FORTRAN-IV language.
2011-12-05
HEATS Project: USF is developing low-cost, high-temperature phase-change materials (PCMs) for use in thermal energy storage systems. Heat storage materials are critical to the energy storage process. In solar thermal storage systems, heat can be stored in these materials during the day and released at night—when the sun is not out—to drive a turbine and produce electricity. In nuclear storage systems, heat can be stored in these materials at night and released to produce electricity during daytime peak-demand hours. Most PCMs do not conduct heat very well. Using an innovative, electroless encapsulation technique, USF is enhancing the heat transfer capability of its PCMs. The inner walls of the capsules will be lined with a corrosion-resistant, high-infrared emissivity coating, and the absorptivity of the PCM will be controlled with the addition of nano-sized particles. USF’s PCMs remain stable at temperatures from 600 to 1,000°C and can be used for solar thermal power storage, nuclear thermal power storage, and other applications.
Advanced turbine cooling, heat transfer, and aerodynamic studies
Je-Chin Han; Schobeiri, M.T.
1995-10-01
The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect on Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Periodic Heat Transfer at Small Pressure Fluctuations
NASA Technical Reports Server (NTRS)
Pfriem, H.
1943-01-01
The effect of cyclic gas pressure variations on the periodic heat transfer at a flat wall is theoretically analyzed and the differential equation describing the process and its solution for relatively. Small pressure fluctuations developed, thus explaining the periodic heat cycle between gas and wall surface. The processes for pure harmonic pressure and temperature oscillations, respectively, in the gas space are described by means of a constant heat transfer coefficient and the equally constant phase angle between the appearance of the maximum values of the pressure and heat flow most conveniently expressed mathematically in the form of a complex heat transfer coefficient. Any cyclic pressure oscillations, can be reduced by Fourier analysis to harmonic oscillations, which result in specific, mutual relationships of heat-transfer coefficients and phase angles for the different harmonics.
Phase Change Heat Transfer Device for Process Heat Applications
Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson
2010-10-01
The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up to approx.1300 K) and industrial scale power transport (=50MW), but also due to a potentially large separation distance between the nuclear and industrial plants (100+m) dictated by safety and licensing mandates. The work reported here is the preliminary analysis of two-phase thermosyphon heat transfer performance with alkali metals. A thermosyphon is a thermal device for transporting heat from one point to another with quite extraordinary properties. In contrast to single-phased forced convective heat transfer via ‘pumping a fluid’, a thermosyphon (also called a wickless heat pipe) transfers heat through the vaporization/condensing process. The condensate is further returned to the hot source by gravity, i.e., without any requirement of pumps or compressors. With this mode of heat transfer, the thermosyphon has the capability to transport heat at high rates over appreciable distances, virtually isothermally and without any requirement for external pumping devices. Two-phase heat transfer by a thermosyphon has the advantage of high enthalpy transport that includes the sensible heat of the liquid, the latent heat of vaporization, and vapor superheat. In contrast, single-phase forced convection transports only the sensible heat of the fluid. Additionally, vapor-phase velocities within a thermosyphon are much greater than single-phase liquid velocities within a forced convective loop. Thermosyphon performance can be limited by the sonic limit (choking) of vapor flow and/or by condensate entrainment. Proper thermosyphon requires analysis of both.
Gopinath, A.; Sadhal, S.S.; Jones, P.D.; Seyed-Yagoobi, J.; Woodbury, K.A.
1996-12-31
In the first section on heat transfer in microgravity, the papers cover phase-change phenomena and thermocapillary flows and surface effects. In the second section, several papers cover solution methods for radiative heat transfer while the rest cover heat transfer in low-temperature environments. The last section covers papers containing valuable information for thermal contact conductance of various materials plus papers on inverse problems in heat transfer. Separate abstracts were prepared for most papers in this volume.
Heat and mass transfer considerations in advanced heat pump systems
Panchal, C.B.; Bell, K.J.
1992-01-01
Advanced heat-pump cycles are being investigated for various applications. However, the working media and associated thermal design aspects require new concepts for maintaining high thermal effectiveness and phase equilibrium for achieving maximum possible thermodynamic advantages. In the present study, the heat- and mass-transfer processes in two heat-pump systems -- those based on absorption processes, and those using refrigerant mixtures -- are analyzed. The major technical barriers for achieving the ideal performance predicted by thermodynamic analysis are identified. The analysis provides general guidelines for the development of heat- and mass-transfer equipment for advanced heat-pump systems.
Heat and mass transfer considerations in advanced heat pump systems
Panchal, C.B.; Bell, K.J.
1992-08-01
Advanced heat-pump cycles are being investigated for various applications. However, the working media and associated thermal design aspects require new concepts for maintaining high thermal effectiveness and phase equilibrium for achieving maximum possible thermodynamic advantages. In the present study, the heat- and mass-transfer processes in two heat-pump systems -- those based on absorption processes, and those using refrigerant mixtures -- are analyzed. The major technical barriers for achieving the ideal performance predicted by thermodynamic analysis are identified. The analysis provides general guidelines for the development of heat- and mass-transfer equipment for advanced heat-pump systems.
Droplet heat transfer and chemical reactions during direct containment heating
Baker, L. Jr.
1986-01-01
A simplified model of heat transfer and chemical reaction has been adapted to evaluate the expected behavior of droplets containing unreacted Zircaloy and stainless steel moving through the containment atmosphere during postulated accidents involving direct containment heating. The model includes internal and external diffusive resistances to reaction. The results indicate that reactions will be incomplete for many conditions characteristic of direct containment heating sequences.
Variable-Conductance Heat-Transfer Module
NASA Technical Reports Server (NTRS)
Hewitt, D. R.
1984-01-01
Working lengths of heat pipes electronically controlled. Rate of heat transfer controlled by electrical heaters shorten effective working lengths of heat pipes. Concept not limited to right circular cylindrical shape. Concept adaptable to terrestrial instruments or processes in which atmospheres or fluids must be cooled and returned to instruments or processes at fixed lower temperatures.
Numerical Simulation of Flow Instability and Heat Transfer
NASA Astrophysics Data System (ADS)
Dou, Hua-Shu; Jiang, Gang
2014-11-01
This paper numerically investigates the physical mechanism of flow instability and heat transfer of natural convection in a cavity with thin fin(s). The left and the right walls of the cavity are differentially heated. The cavity is given an initial temperature, and the thin fin(s) is fixed on the hot wall in order to control the heat transfer. The finite volume method with the SIMPLE scheme is used to simulate the flow. Distributions of the temperature, the pressure, the velocity and the total pressure are achieved. Then, the energy gradient method is employed to study the physical mechanism of flow instability and the effect of the thin fin(s) on heat transfer. Based on the energy gradient method, the energy gradient function K represents the characteristic of flow instability. It is observed from the simulation results that the positions where instabilities take place in the temperature contours accord well with those of higher K value, which demonstrates that the energy gradient method reveals the physical mechanism of flow instability. Furthermore, the effect of the fin length, the fin position, the fin number, and Ra on heat transfer is also investigated. It is found that the effect of the fin length on heat transfer is negligible when Ra is relatively high. When there is only one fin, the most efficient heat transfer rate is achieved as the fin is fixed at the middle height of the cavity. The fin blocks heat transfer with a relatively small Ra, but the fin enhances heat transfer with a relatively large Ra. The fin(s) enhances heat transfer gradually with the increase of Ra under the influence of the thin fin(s). Finally, it is observed that both Kmax and Ra can reveal the physical mechanism of natural convection from different approaches.
Near field heat transfer in superlattices
NASA Astrophysics Data System (ADS)
Esquivel-Sirvent, Raul
2015-03-01
I present a theoretical calculation of the near field heat transfer between super lattices made of alternative layers of both metallic and semiconducting materials. The calculation of the near field transfer requires the knowledge of the reflectivities, that are obtained by calculating the surface impedance of the super lattice. Depending on the periodicity of the lattice and the dielectric function of the materials the near field heat transfer can be modulated or engineered. Additional control on the heat transfer is achieved by introducing defects in the superlattice. The results are extended to include photonic hypercrystals that effectively behave like a hyperbolic metamaterial even in the near field (1), where the tuning of the heat transfer is modified by Partial Support from DGAPA-UNAM project IN 111214.
Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger
Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari
2014-01-01
This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%–0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%–24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles. PMID:27433521
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred
1988-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred (Inventor)
1987-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Prediction of Unshsrouded Rotor Blade Tip Heat Transfer
NASA Technical Reports Server (NTRS)
Ameri, A. A.; Steinthorsson, E.
1994-01-01
The rate of heat transfer on the tip of a turbine rotor blade and on the blade surface in the vicinity of the tip, was successfully predicted. The computations were performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations using an efficient multigrid method. The case considered for the present calculations was the Space Shuttle Main Engine (SSME) high pressure fuel side turbine. The predictions of the blade tip heat transfer agreed reasonably well with the experimental measurements using the present level of grid refinement. On the tip surface, regions with high rate of heat transfer was found to exist close to the pressure side and suction side edges. Enhancement of the heat transfer was also observed on the blade surface near the tip. Further comparison of the predictions was performed with results obtained from correlations based on fully developed channel flow.
Heat transfer peculiarities in supersonic flows
NASA Astrophysics Data System (ADS)
Borovoi, V. Ia.; Brazhko, V. N.; Maikapar, G. I.; Skuratov, A. S.; Struminskaia, I. V.
1992-12-01
A method of heat transfer and gas flow investigation based on the application of thermal sensitive coatings or thermocouple sensors and various visualization techniques is described. The thermal sensitive coatings and visualization reveal heat transfer peculiarities, and the complex nature of the method contributes to understanding the processes and generalization of quantitative results. Data concerning heat transfer on the leeward side of a blunt cone in the regions of the shock-wave boundary layer and bow wave interaction, in gaps and cavities of the orbiter's thermal insulation, and in the vicinity of them, are presented.
Passive heat transfer means for nuclear reactors
Burelbach, James P.
1984-01-01
An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heat pipes are operatively interposed between the components, with the vaporizing section of the heat pipe proximate the hot component operable to cool it and the primary condensing section of the heat pipe proximate the other and cooler component operable to heat it. Each heat pipe further has a secondary condensing section that is located outwardly beyond the reactor confinement and in a secondary heat sink, such as air ambient the containment, that is cooler than the other reactor component. Means such as shrouding normally isolated the secondary condensing section from effective heat transfer with the heat sink, but a sensor responds to overheat conditions of the reactor to open the shrouding, which thereby increases the cooling capacity of the heat pipe. By having many such heat pipes, an emergency passive cooling system is defined that is operative without electrical power.
HEAT TRANSFER AND TRITIUM PRODUCING SYSTEM
Johnson, E.F.
1962-06-01
This invention related to a circulating lithium-containing blanket system in a neution source hav'ing a magnetic field associated therewith. The blanket serves simultaneously and efficiently as a heat transfer mediunm and as a source of tritium. The blanket is composed of a lithium-6-enriched fused salt selected from the group consisting of lithium nitrite, lithium nitrate, a mixture of said salts, a mixture of each of said salts with lithium oxide, and a mixture of said salts with each other and with lithium oxide. The moderator, which is contained within the blanket in a separate conduit, can be water. A stellarator is one of the neutron sources which can be used in this invention. (AEC)
Nanofluids for heat transfer : an engineering approach.
Timofeeva, E. V.; Yu, W.; France, D. M.; Singh, D.; Routbort, J. L.
2011-02-28
An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties.
Computing Efficiency Of Transfer Of Microwave Power
NASA Technical Reports Server (NTRS)
Pinero, L. R.; Acosta, R.
1995-01-01
BEAM computer program enables user to calculate microwave power-transfer efficiency between two circular apertures at arbitrary range. Power-transfer efficiency obtained numerically. Two apertures have generally different sizes and arbitrary taper illuminations. BEAM also analyzes effect of distance and taper illumination on transmission efficiency for two apertures of equal size. Written in FORTRAN.
Determination of the heat transfer coefficients in transient heat conduction
NASA Astrophysics Data System (ADS)
Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.
2013-09-01
The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.
Base fluid in improving heat transfer for EV car battery
NASA Astrophysics Data System (ADS)
Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.
2015-05-01
This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.
Heat transfer behavior of molten nitrate salt
NASA Astrophysics Data System (ADS)
Das, Apurba K.; Clark, Michael M.; Teigen, Bard C.; Fiveland, Woodrow A.; Anderson, Mark H.
2016-05-01
The usage of molten nitrate salt as heat transfer fluid and thermal storage medium decouples the generation of electricity from the variable nature of the solar resource, allowing CSP plants to avoid curtailment and match production with demand. This however brings some unique challenges for the design of the molten salt central receiver (MSCR). An aspect critical to the use of molten nitrate (60wt%/40wt% - NaNO3/KNO3) salt as heat transfer fluid in the MSCR is to understand its heat transfer behavior. Alstom collaborated with the University of Wisconsin to conduct a series of experiments and experimentally determined the heat transfer coefficients of molten nitrate salt up to high Reynolds number (Re > 2.0E5) and heat flux (q″ > 1000 kW/m2), conditions heretofore not reported in the literature. A cartridge heater instrumented with thermocouples was installed inside a stainless steel pipe to form an annular test section. The test section was installed in the molten salt flow loop at the University of Wisconsin facility, and operated over a range of test conditions to determine heat transfer data that covered the expected operating regime of a practical molten salt receiver. Heat transfer data were compared to widely accepted correlations found in heat transfer literature, including that of Gnielinski. At lower Reynolds number conditions, the results from this work concurred with the molten salt heat transfer data reported in literature and followed the aforementioned correlations. However, in the region of interest for practical receiver design, the correlations did not accurately model the experimentally determined heat transfer data. Two major effects were observed: (i) all other factors remaining constant, the Nusselt numbers gradually plateaued at higher Reynolds number; and (ii) at higher Reynolds number a positive interaction of heat flux on Nusselt number was noted. These effects are definitely not modeled by the existing correlations. In this paper a new
Heat transfer near turbine nozzle endwall.
Chyu, M K
2001-05-01
This paper gives an overview and reviews recent findings concerning turbine endwall cooling in the literature. The text below begins with a brief discussion of the secondary flows and heat transfer around cascade endwall. This will be followed by a review of recent developments in cooling concepts and related heat transfer results. Key topics include: film cooling, upstream bleeding, endwall contouring, and leakage through component interfaces. PMID:11460636
Nanoparticle enhanced ionic liquid heat transfer fluids
Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.
2014-08-12
A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.
NASA Astrophysics Data System (ADS)
Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi
2016-03-01
For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio ( h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.
Heat and mass transfer in materials processing
NASA Astrophysics Data System (ADS)
Tanasawa, Ichiro; Lior, Noam
Various papers on heat and mass transfer in materials processing are presented. The topics addressed include: heat transfer in plasma spraying, structure of ultrashort pulse plasma for CVD processing, heat flow and thermal contraction during plasma spray deposition, metal melting process by laser heating, improved electron beam weld design and control with beam current profile measurements, transport phenomena in laser materials processing, perspectives on integrated modeling of transport processes in semiconductor crystal growth, numerical simulation of natural convection in crystal growth in space and on the earth, conjugate heat transfer in crystal growth, effects of convection on the solidification of binary mixtures. Also discussed are: heat transfer in in-rotating-liquid-spinning process, thermal oscillations in materials processing, modeling and simulation of manufacturing processes of advanced composite materials, reaction engineering principles of combustion synthesis of advanced materials, numerical evaluation of the physical properties of magnetic fluids suitable for heat transfer control, and measurement techniques of thermophysical properties of high temperature melts. (For individual items see A93-10827 to A93-10843)
Heat transfer measurements for Stirling machine cylinders
NASA Technical Reports Server (NTRS)
Kornhauser, Alan A.; Kafka, B. C.; Finkbeiner, D. L.; Cantelmi, F. C.
1994-01-01
The primary purpose of this study was to measure the effects of inflow-produced heat turbulence on heat transfer in Stirling machine cylinders. A secondary purpose was to provide new experimental information on heat transfer in gas springs without inflow. The apparatus for the experiment consisted of a varying-volume piston-cylinder space connected to a fixed volume space by an orifice. The orifice size could be varied to adjust the level of inflow-produced turbulence, or the orifice plate could be removed completely so as to merge the two spaces into a single gas spring space. Speed, cycle mean pressure, overall volume ratio, and varying volume space clearance ratio could also be adjusted. Volume, pressure in both spaces, and local heat flux at two locations were measured. The pressure and volume measurements were used to calculate area averaged heat flux, heat transfer hysteresis loss, and other heat transfer-related effects. Experiments in the one space arrangement extended the range of previous gas spring tests to lower volume ratio and higher nondimensional speed. The tests corroborated previous results and showed that analytic models for heat transfer and loss based on volume ratio approaching 1 were valid for volume ratios ranging from 1 to 2, a range covering most gas springs in Stirling machines. Data from experiments in the two space arrangement were first analyzed based on lumping the two spaces together and examining total loss and averaged heat transfer as a function of overall nondimensional parameter. Heat transfer and loss were found to be significantly increased by inflow-produced turbulence. These increases could be modeled by appropriate adjustment of empirical coefficients in an existing semi-analytic model. An attempt was made to use an inverse, parameter optimization procedure to find the heat transfer in each of the two spaces. This procedure was successful in retrieving this information from simulated pressure-volume data with artificially
Interactive Heat Transfer Simulations for Everyone
ERIC Educational Resources Information Center
Xie, Charles
2012-01-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…
Heat transfer coefficient of nanofluids in minichannel heat sink
NASA Astrophysics Data System (ADS)
Utomo, Adi T.; Zavareh, Ashkan I. T.; Poth, Heiko; Wahab, Mohd; Boonie, Mohammad; Robbins, Phillip T.; Pacek, Andrzej W.
2012-09-01
Convective heat transfer in a heat sink consisting of rectangular minichannels and cooled with alumina and titania nanofluids has been investigated experimentally and numerically. Numerical simulations were carried out in a three dimensional domain employing homogeneous mixture model with effective thermo-physical properties of nanofluids. The predictions of base temperature profiles of the heat sink cooled with both water and nanofluids agree well with the experimental data. Experimental and numerical results show that the investigated nanofluids neither exhibits unusual enhancement of heat transfer coefficient nor decreases the heat sink base temperature. Although both nanofluids showed marginal thermal conductivity enhancements, the presence of solid nanoparticles lowers the specific heat capacity of nanofluids offseting the advantage of thermal conductivity enhancement. For all investigated flow rates, the Nusselt number of both nanofluids overlaps with that of water indicating that both nanofluids behave like single-phase fluids.
Heat Transfer to Fuel Sprays Injected into Heated Gases
NASA Technical Reports Server (NTRS)
Selden, Robert F; Spencer, Robert C
1938-01-01
This report presents the results of a study made of the influence of several variables on the pressure decrease accompanying injection of a relatively cool liquid into a heated compressed gas. Indirectly, this pressure decrease and the time rate of change of it are indicative of the total heat transferred as well as the rate of heat transfer between the gas and the injected liquid. Air, nitrogen, and carbon dioxide were used as ambient gases; diesel fuel and benzene were the injected liquids. The gas densities and gas-fuel ratios covered approximately the range used in compression-ignition engines. The gas temperatures ranged from 150 degrees c. to 350 degrees c.
Heat transfer studies. Quarterly report
Boehm, R.; Chen, Y.T.; Ma, L.
1995-04-20
Nitrogen gas has been replaced by room air in the extension of multi-phase models to sub-residual saturation experiments on drying. The TOUGH2 code has been used to simulate the same problem with the identical boundary conditions. A constant heat flux boundary condition on the heater has been performed in the repository drift experiment. The desired constant heat flux can produce a steady-state heater temperature ({approx}238{degrees}C) close to the constant heater surface temperature used before. What occurs in the air annulus and in the porous medium with the different thermal boundary conditions and water quantities is reported.
Interactive Heat Transfer Simulations for Everyone
NASA Astrophysics Data System (ADS)
Xie, Charles
2012-04-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy, temperature distribution, and heat transfer may provide a straightforward method for teaching and learning these concepts. Through interacting with visual representations of the concepts and observing how they respond to manipulations, the misconceptions may be dispelled more effectively. This paper presents a new educational simulation tool called Energy2D developed to explore this idea.
Code for Multiblock CFD and Heat-Transfer Computations
NASA Technical Reports Server (NTRS)
Fabian, John C.; Heidmann, James D.; Lucci, Barbara L.; Ameri, Ali A.; Rigby, David L.; Steinthorsson, Erlendur
2006-01-01
The NASA Glenn Research Center General Multi-Block Navier-Stokes Convective Heat Transfer Code, Glenn-HT, has been used extensively to predict heat transfer and fluid flow for a variety of steady gas turbine engine problems. Recently, the Glenn-HT code has been completely rewritten in Fortran 90/95, a more object-oriented language that allows programmers to create code that is more modular and makes more efficient use of data structures. The new implementation takes full advantage of the capabilities of the Fortran 90/95 programming language. As a result, the Glenn-HT code now provides dynamic memory allocation, modular design, and unsteady flow capability. This allows for the heat-transfer analysis of a full turbine stage. The code has been demonstrated for an unsteady inflow condition, and gridding efforts have been initiated for a full turbine stage unsteady calculation. This analysis will be the first to simultaneously include the effects of rotation, blade interaction, film cooling, and tip clearance with recessed tip on turbine heat transfer and cooling performance. Future plans call for the application of the new Glenn-HT code to a range of gas turbine engine problems of current interest to the heat-transfer community. The new unsteady flow capability will allow researchers to predict the effect of unsteady flow phenomena upon the convective heat transfer of turbine blades and vanes. Work will also continue on the development of conjugate heat-transfer capability in the code, where simultaneous solution of convective and conductive heat-transfer domains is accomplished. Finally, advanced turbulence and fluid flow models and automatic gridding techniques are being developed that will be applied to the Glenn-HT code and solution process.
Indirect evaporative coolers with enhanced heat transfer
Kozubal, Eric; Woods, Jason; Judkoff, Ron
2015-09-22
A separator plate assembly for use in an indirect evaporative cooler (IEC) with an air-to-air heat exchanger. The assembly includes a separator plate with a first surface defining a dry channel and a second surface defining a wet channel. The assembly includes heat transfer enhancements provided on the first surface for increasing heat transfer rates. The heat transfer enhancements may include slit fins with bodies extending outward from the first surface of separator plate or may take other forms including vortex generators, offset strip fins, and wavy fins. In slit fin implementations, the separator plate has holes proximate to each of the slit fins, and the separator plate assembly may include a sealing layer applied to the second surface of the separator plate to block air flow through the holes. The sealing layer can be a thickness of adhesive, and a layer of wicking material is applied to the adhesive.
Capillary-Condenser-Pumped Heat-Transfer Loop
NASA Technical Reports Server (NTRS)
Silverstein, Calvin C.
1989-01-01
Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.
Modeling microscale heat transfer using Calore.
Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley
2005-09-01
Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.
Simplified models for heat transfer in rooms
NASA Astrophysics Data System (ADS)
Graca, Guilherme C. C. Carrilho Da
Buildings protect their occupants from the outside environment. As a semi-enclosed environment, buildings tend to contain the internally generated heat and air pollutants, as well as the solar and conductive heat gains that can occur in the facade. In the warmer months of the year this generally leads to overheating, creating a need for a cooling system. Ventilation air replaces contaminated air in the building and is often used as the dominant medium for heat transfer between indoor and outdoor environments. The goal of the research presented in this thesis is to develop a better understanding of the important parameters in the performance of ventilation systems and to develop simplified convective heat transfer models. The general approach used in this study seeks to capture the dominant physical processes for these problems with first order accuracy, and develop simple models that show the correct system behavior trends. Dimensional analysis, in conjunction with simple momentum and energy conservation, scaled model experiments and numerical simulations, is used to improve airflow and heat transfer rate predictions in both single and multi room ventilation systems. This study includes the three commonly used room ventilation modes: mixing, displacement and cross-ventilation. A new modeling approach to convective heat transfer between the building and the outside is presented: the concept of equivalent room heat transfer coefficient. The new model quantifies the reduction in heat transfer between ventilation air and internal room surfaces caused by limited thermal capacity and temperature variation of the air for the three modes studied. Particular emphasis is placed on cross-ventilation, and on the development of a simple model to characterize the airflow patterns that occur in this case. The implementation of the models in a building thermal simulation software tool is presented as well as comparisons between model predictions, experimental results and complex
A heat transfer model of a horizontal ground heat exchanger
NASA Astrophysics Data System (ADS)
Mironov, R. E.; Shtern, Yu. I.; Shtern, M. Yu.; Rogachev, M. S.
2016-04-01
Ground-source heat pumps are gaining popularity in Eastern Europe, especially those which are using the horizontal ground heat exchanger (GHX). Due to the difficulty of accessing GHX after the installation, materials and the quality of the installation must satisfy the very high requirements. An inaccurate calculation of GHX can be the reason of a scarcity of heat power in a crucial moment. So far, there isn't any appropriate mathematical description of the horizontal GHX which takes into account the mutual influence of GHX pipes on each other. To solve this problem we used the temperature wave approach. As a result, a mathematical model which describes the dependence of the heat transfer rate per unit length of the horizontal GHX pipe on the thermal properties of soil, operating time of GHX and the distance between pipes was obtained. Using this model, heat transfer rates per unit length of a horizontal GHX were plotted as functions of the distance between pipes and operating time. The modeling shows that heat transfer rates decreases rapidly with the distance between pipes lower then 2 meters. After the launch of heat pump, heat power of GHX is reduced during the first 20 - 30 days and get steady after that. The obtained results correlate with experimental data. Therefore the proposed mathematical model can be used to design a horizontal GHX with the optimal characteristics, and predict its capability during operation.
Experimental and numerical investigation of HyperVapotron heat transfer
NASA Astrophysics Data System (ADS)
Wang, Weihua; Deng, Haifei; Huang, Shenghong; Chu, Delin; Yang, Bin; Mei, Luoqin; Pan, Baoguo
2014-12-01
The divertor first wall and neutral beam injection (NBI) components of tokamak devices require high heat flux removal up to 20-30 MW m-2 for future fusion reactors. The water cooled HyperVapotron (HV) structure, which relies on internal grooves or fins and boiling heat transfer to maximize the heat transfer capability, is the most promising candidate. The HV devices, that are able to transfer large amounts of heat (1-20 MW m-2) efficiently, have therefore been developed specifically for this application. Until recently, there have been few attempts to observe the detailed bubble characteristics and vortex evolvement of coolant flowing inside their various parts and understand of the internal two-phase complex heat transfer mechanism behind the vapotron effect. This research builds the experimental facilities of HyperVapotron Loop-I (HVL-I) and Pressure Water HyperVapotron Loop-II (PWHL-II) to implement the subcooled boiling principle experiment in terms of typical flow parameters, geometrical parameters of test section and surface heat flux, which are similar to those of the ITER-like first wall and NBI components (EAST and MAST). The multiphase flow and heat transfer phenomena on the surface of grooves and triangular fins when the subcooled water flowed through were observed and measured with the planar laser induced fluorescence (PLIF) and high-speed photography (HSP) techniques. Particle image velocimetry (PIV) was selected to reveal vortex formation, the flow structure that promotes the vapotron effect during subcooled boiling. The coolant flow data for contributing to the understanding of the vapotron phenomenon and the assessment of how the design and operational conditions that might affect the thermal performance of the devices were collected and analysed. The subcooled flow boiling model and methods of HV heat transfer adopted in the considered computational fluid dynamics (CFD) code were evaluated by comparing the calculated wall temperatures with the
Characteristics of Transient Boiling Heat Transfer
Liu, Wei; Monde, Masanori; Mitsutake, Y.
2002-07-01
In this paper, one dimensional inverse heat conduction solution is used for a measurement of pool boiling curve. The experiments are performed under atmospheric pressure for copper, brass, carbon steel and gold. Boiling curves, including unsteady transition boiling region, are found can be traced fairly well from a simple experiment system by solving inverse heat conduction solution. Boiling curves for steady heating and transient heating, for heating process and cooling process are compared. Surface behavior around CHF point, transition boiling and film-boiling regions are observed by using a high-speed camera. The results show the practicability of the inverse heat conduction solution in tracing boiling curve and thereby supply us a new way in boiling heat transfer research. (authors)
NASA Astrophysics Data System (ADS)
Utaka, Yoshio; Saito, Akio; Nakata, Naoki
The objectives of this report are to propose a new method of the high performance cold energy storage using ice as a phase change material and to clarify the heat transfer characteristics of the apparatus of ice cold energy storage based on the proposed principle. A working medium vapor layer a water layer and a working medium liquid layer stratified in this order from the top were kept in an enclosure composed of a condenser, an evaporator and a condensate receiver-and-return tube. The direct contact heat transfers between water or ice and a working medium in an enclosure were applied for realizing the high performance cold energy storage and release. In the storage and release processes, water changes the phase between the liquid and the solid, and the working medium cnanges between the vapor and the liquid with a natural circulation. Experimental apparatus was manufactured and R12 and R114 were selected as working media in the thermal energy storage enclosure. It was confirmed by the measurements that the efficient formation and melting of ice were achieved. Then, th e heat transfer characteristics were clarified for the effects of the initial water height, the initial height of woking medium liquid layer and the inlet coolant temperature.
Heat transfer in pressurized circulating fluidized beds
Wirth, K.E.
1997-12-31
The wall-to-suspension heat transfer in circulating fluidized beds (CFBs) operated at almost atmospheric pressure depends on the fluid mechanics immediately near the wall and on the thermal properties of the gas used. No influence of the superficial gas velocity adjusted is present. Consequently, the wall-to-suspension heat transfer coefficient in the form of the Nusselt number can be described by the Archimedes number of the gas-solid-system and the pressure drop number. The last number relates the cross-sectional average solids concentration to the solids concentration at minimum fluidization condition. However, with pressurized CFBs an influence of the superficial gas velocity on the wall-to-suspension heat transfer can be observed. Normalizing the superficial gas velocity in the form of the particle Froude number, two cases for the heat transfer in pressurized CFBs can be detected: with small particle Froude numbers (smaller than four) the same flow behavior and consequently the same heat transfer correlation is valid as it is for CFBs operated at almost atmospheric conditions; and with high particle Froude numbers (for example higher than four) the flow behavior immediately near the heat exchanger surface (CFB wall) can change. Instead of curtains of solids falling down with almost atmospheric pressure swirls of gas and solids can occur in the vicinity of the CFB wall when the static pressure is increased. With the change of the flow pattern near the CFB wall, i.e., the heat exchanger surface, a change of the heat transfer coefficient takes place. For the same Archimedes number, i.e., the same gas-solid system, and the same pressure drop number, i.e., the same cross-sectional average solids concentration, the Nusselt number, i.e., the heat transfer coefficient, increases when the flow pattern near the CFB wall changes from the curtain-type flow to that of the swirl-type flow. From experimentally obtained data in a cold running CFB a very simple correlation was
Radiant heat transfer from storage casks to the environment
Carlson, R W; Hovingh, J; Thomas, G R
1999-05-10
A spent fuel storage cask must efficiently transfer the heat released by the fuel assemblies through the cask walls to the environment. This heat must be transferred through passive means, limiting the energy transfer mechanisms from the cask to natural convection and radiation heat transfer.. Natural convection is essentially independent of the characteristics of the array of casks, provided there is space between casks to permit a convection loop. Radiation heat transfer, however, depends on the geometric arrangement of the array of casks because the peripheral casks will shadow the interior casks and restrict radiant heat transfer from all casks to the environment. The shadowing of one cask by its neighbors is determined by a view factor that represents the fraction of radiant energy that leaves the surface of a cask and reaches the environment. This paper addresses the evaluation of the view factor between a centrally located spent fuel storage cask and the environment. By combining analytic expressions for the view factor of (1) infinitely long cylinders and (2) finite cylinders with a length-to-diameter ratio of 2 to represent spent fuel storage casks, the view factor can be evaluated for any practical array of spent fuel storage casks.
Fluid dynamics at transition regions of enhanced heat transfer channels
NASA Astrophysics Data System (ADS)
Case, Jennifer C.; Pohlman, Nicholas A.
2012-11-01
Helical wire coil inserts are used to enhance heat transfer in high heat flux cooling channels. Past research using temperature probes has sufficiently proven that wire coils increase heat transfer by factors of three to five through the disruption of the boundary layer in the channels. The coils are passive devices that are inexpensive to manufacture and easily integrate into existing heat exchangers given the limited pressure drop they produce. Most of the fluid mechanics research in flow over helical coils has focused on the dynamics and vortex structure in fully developed regions rather than the short transition region where the enhanced heat transfer is often expected. Understanding how the development of the flow occurs over the axial length of the cooling channel will determine minimum dimensions necessary for enhanced heat transfer. Results of particle-shadow velocimetry (PSV) measurements report on the flow velocities and turbulence that occurs in the transition regions at the beginning of wire coil inserts. The ability to relate parameters such as flow rate, wire diameter, coil pitch, and the total tube length will increase fundamental knowledge and will allow for more efficient heat exchanger designs. Funding provided by NIU's Undergraduate Special Opportunities in Artistry & Research grant program.
HOST turbine heat transfer program summary
NASA Technical Reports Server (NTRS)
Gladden, Herbert J.; Simoneau, Robert J.
1988-01-01
The objectives of the HOST Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena and to assess and improve the analytical methods used to predict the flow and heat transfer in high temperature gas turbines. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. A building-block approach was utilized and the research ranged from the study of fundamental phenomena and modeling to experiments in simulated real engine environments. Experimental research accounted for approximately 75 percent of the funding with the remainder going to analytical efforts. A healthy government/industry/university partnership, with industry providing almost half of the research, was created to advance the turbine heat transfer design technology base.
Heat transfer on accreting ice surfaces
NASA Technical Reports Server (NTRS)
Yamaguchi, Keiko; Hansman, R. John, Jr.
1990-01-01
Based on previous observations of glaze ice accretion, a 'Multi-Zone' model with distinct zones of different surface roughness is demonstrated. The use of surface roughness in the LEWICE ice accretion prediction code is examined. It was found that roughness is used in two ways: to determine the laminar to turbulent transition location and to calculate the turbulent heat transfer coefficient. A two zone version of the Multi-Zone model is implemented in the LEWICE code, and compared with experimental heat transfer coefficient and ice accretin results. The analysis of the boundary layer transition, surface roughness, and viscous flow field effects significantly increased the accuracy in predicting heat transfer coefficients. The Multi-Zone model was found to greatly improve the ice accretion prediction for the cases compared.
Heat transfer on accreting ice surfaces
NASA Technical Reports Server (NTRS)
Yamaguchi, Keiko; Hansman, R. John, Jr.
1993-01-01
Based on previous observations of glaze ice accretion on aircraft surfaces, a multizone model with distinct zones of different surface roughness is demonstrated. The use of surface roughness in the LEWICE ice accretion prediction code is examined. It was found that roughness is used in two ways: (1) to determine the laminar to turbulent boundary-layer transition location; and (2) to calculate the convective turbulent heat-transfer coefficient. A two-zone version of the multizone model is implemented in the LEWICE code, and compared with experimental convective heat-transfer coefficient and ice accretion results. The analysis of the boundary-layer transition, surface roughness, and viscous flowfield effects significantly increased the accuracy in predicting heat-transfer coefficients. The multizone model was found to significantly improve the ice accretion prediction for the cases compared.
Gondrexon, N; Cheze, L; Jin, Y; Legay, M; Tissot, Q; Hengl, N; Baup, S; Boldo, P; Pignon, F; Talansier, E
2015-07-01
This paper aims to illustrate the interest of ultrasound technology as an efficient technique for both heat and mass transfer intensification. It is demonstrated that the use of ultrasound results in an increase of heat exchanger performances and in a possible fouling monitoring in heat exchangers. Mass transfer intensification was observed in the case of cross-flow ultrafiltration. It is shown that the enhancement of the membrane separation process strongly depends on the physico-chemical properties of the filtered suspensions. PMID:25216897
Self supporting heat transfer element
Story, Grosvenor Cook; Baldonado, Ray Orico
2002-01-01
The present invention provides an improved internal heat exchange element arranged so as to traverse the inside diameter of a container vessel such that it makes good mechanical contact with the interior wall of that vessel. The mechanical element is fabricated from a material having a coefficient of thermal conductivity above about 0.8 W cm.sup.-1.degree. K.sup.-1 and is designed to function as a simple spring member when that member has been cooled to reduce its diameter to just below that of a cylindrical container or vessel into which it is placed and then allowed to warm to room temperature. A particularly important application of this invention is directed to a providing a simple compartmented storage container for accommodating a hydrogen absorbing alloy.
Mounting for diodes provides efficient heat sink
NASA Technical Reports Server (NTRS)
1964-01-01
Efficient heat sink is provided by soldering diodes to metal support bars which are brazed to a ceramic base. Electrical connections between diodes on adjacent bars are made flexible by metal strips which aid in heat dissipation.
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Koplow, Jeffrey P.
2016-02-16
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 transferred 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.
Enhanced boiling heat transfer using radial fins
NASA Astrophysics Data System (ADS)
Razelos, P.; Das, S.; Krikkis, R. N.
2008-04-01
A numerical bifurcation analysis is carried out in order to determine the solution structure of radial fins subjected to multi-boiling heat transfer mode. One-dimensional conduction is employed throughout the thermal analysis. The fluid heat transfer coefficient is temperature dependent on the three regimes of phase-change of the fluid. Six fin profiles, defined in the text, are considered. Multiplicity structure is obtained to determine different types of bifurcation diagrams, which describe the dependence of a state variable of the system like the temperature or the heat dissipation on the fin design parameters, conduction convection parameter (CCP) or base temperature difference (Δ T). Specifically, the effects of Δ T, CCP and Biot number are analyzed. The results are presented graphically, showing the significant behavioral features of the heat rejection mechanism.
Metallized Gelled Propellant Heat Transfer Tests Analyzed
NASA Technical Reports Server (NTRS)
Palaszewski, Bryan A.
1997-01-01
A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted at the NASA Lewis Research Center. These experiments used a small 20- to 40-lbf thrust engine composed of a modular injector, an igniter, a chamber, and a nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt % loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each channel used water flow to carry heat away from the chamber and the attached thermocouples; flow meters allowed heat flux estimates at each of the 31 stations.
Heat transfer during evaporation on a small surface (Review)
NASA Astrophysics Data System (ADS)
Tolubinskii, V. I.; Antonenko, V. A.; Kudritskii, G. R.; Ostrovskii, Iu. N.
Experimental data in the literature on the intensity of heat transfer and critical heat loads associated with the boiling of a liquid on a small surface are examined. Various methods for intensifying heat transfer are discussed. Expressions are presented for calculating heat transfer coefficients and critical heat flux densities.
Heat transfer characteristics of an emergent strand
NASA Technical Reports Server (NTRS)
Simon, W. E.; Witte, L. C.; Hedgcoxe, P. G.
1974-01-01
A mathematical model was developed to describe the heat transfer characteristics of a hot strand emerging into a surrounding coolant. A stable strand of constant efflux velocity is analyzed, with a constant (average) heat transfer coefficient on the sides and leading surface of the strand. After developing a suitable governing equation to provide an adequate description of the physical system, the dimensionless governing equation is solved with Laplace transform methods. The solution yields the temperature within the strand as a function of axial distance and time. Generalized results for a wide range of parameters are presented, and the relationship of the results and experimental observations is discussed.
Evaporative heat transfer in beds of sensible heat pellets
Arimilli, R.V.; Moy, C.A.
1989-03-01
An experimental study of boiling/evaporative heat transfer from heated spheres in vertical packed beds with downward liquid-vapor flow of Refrigerant-113 was conducted. Surface superheats of 1 to 50{degrees}C, mass flow rates of 1.7 to 5.6 Kg/min, sphere diameters of 1.59 and 2.54 cm, quality (i.e., mass fraction of vapor) of the inlet flow of 0.02 to 1.0, and two surface conditions were considered. Instrumented smooth and rough aluminum spheres were used to measure the heat transfer coefficients under steady state conditions. Heat transfer coefficients were independently determined for each sphere at three values three values of surface superheat. The quantitative results of this extensive experimental study are successfully correlated. The correlation equation for the boiling heat transfer coefficients is presented in terms of a homogeneous model. The correlation may be used in the development of numerical models to simulate the transient thermal performance of packed bed thermal energy storage unit while operating as an evaporator. The boiling of the liquid-vapor flow around the spheres in the packed bed was visually observed with a fiber-optic baroscope and recorded on a videotape. The visualization results showed qualitatively the presence of four distinct flow regimes. One of these occurs under saturated inlet conditions and are referred to as the Low-quality, Medium-quality, and High-quality Regimes. The regimes are discussed in detail in this paper.
Heat transfer mechanisms in pulsating heat-pipes with nanofluid
NASA Astrophysics Data System (ADS)
Gonzalez, Miguel; Kelly, Brian; Hayashi, Yoshikazu; Kim, Yoon Jo
2015-01-01
In this study, the effect of silver nanofluid on a pulsating heat-pipe (PHP) thermal performance was experimentally investigated to figure out how nanofluid works with PHP. A closed loop PHP was built with 3 mm diameter tubes. Thermocouples and pressure transducers were installed for fluid and surface temperature and pressure measurements. The operating temperature of the PHP varied from 30-100 °C, with power rates of 61 W and 119 W. The fill ratio of 30%, 50%, and 70% were tested. The results showed that the evaporator heat transfer performance was degraded by the addition of nanoparticles due to increased viscosity at high power rate, while the positive effects of high thermal conductivity and enhanced nucleate boiling worked better at low power rate. In the condenser section, owing to the relatively high liquid content, nanofluid more effectively improved the heat transfer performance. However, since the PHP performance was dominantly affected by evaporator heat transfer performance, the overall benefit of enhanced condenser section performance was greatly limited. It was also observed that the poor heat transfer performance with nanofluid at the evaporator section led to lower operating pressure of PHP.
Experimental determination of stator endwall heat transfer
NASA Technical Reports Server (NTRS)
Boyle, Robert J.; Russell, Louis M.
1989-01-01
Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane passage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Results were obtained for Reynolds numbers based on inlet velocity and axial chord between 73,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heat transfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heat transfer. Endwall heat transfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heat transfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.
Experimental determination of stator endwall heat transfer
NASA Technical Reports Server (NTRS)
Boyle, Robert J.; Russell, Louis M.
1989-01-01
Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane possage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Resutls were obtained for Reynolds numbers based on inlet velocity and axial chord between 75,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heat transfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heat transfer. Endwall heat transfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heat transfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.
Microscale surface modifications for heat transfer enhancement.
Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C
2013-10-01
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process. PMID:24003985
NASA Astrophysics Data System (ADS)
Xing, BaoYu; Liu, Kun; Huang, MinChao; Cheng, MouSen
2014-06-01
Solar thermal propulsion system includes solar thermal propulsion and nuclear thermal propulsion, and it is a significant issue to improve the heat transfer efficiency of the solar thermal thruster. This paper proposes a platelet configuration to be used in the heat exchanger core, which is the most important component of solar thermal system. The platelet passage can enhance the heat transfer between the propellant and the hot core heated by the concentrated sunlight. Based on fluid-solid coupled heat transfer, the paper utilized the platelet heat transfer characteristic to simulate the heat transfer and flow field of the platelet passage. A coupled system includes the coupled flow and heat transfer between the fluid region and solid region. The simulation result shows that the propellant can be heated to the design temperature of 2300K in platelet passage of the thermal propulsion system, and the fluid-solid coupled method can solve the heat transfer in the platelet structure more precisely.
Natural convective heat transfer from square cylinder
NASA Astrophysics Data System (ADS)
Novomestský, Marcel; Smatanová, Helena; Kapjor, Andrej
2016-06-01
This article is concerned with natural convective heat transfer from square cylinder mounted on a plane adiabatic base, the cylinders having an exposed cylinder surface according to different horizontal angle. The cylinder receives heat from a radiating heater which results in a buoyant flow. There are many industrial applications, including refrigeration, ventilation and the cooling of electrical components, for which the present study may be applicable
Estimation of radiative heat transfer using a geometric human model.
Kakuta, N; Yokoyama, S; Nakamura, M; Mabuchi, K
2001-03-01
In order to provide a detailed estimate of radiative heat transfer between a human body and its surrounding environment, we have developed a geometric model of a human form and an algorithm. The model closely resembles the actual shape of a human body and is composed of small quadrilateral surfaces. Dealing with an object or a space with an arbitrary shape, the developed algorithm can judge efficiently whether there is an obstruction between a pair of surfaces. As a result, the angle factors between a pair of surfaces that only occur during radiative heat transfer can be defined. The distribution of the radiative heat transfer rates shows the characteristics of body shape and variations in posture. PMID:11327500
Heat flux sensors for infrared thermography in convective heat transfer.
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-01-01
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-01-01
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758
Computational Aspects of Heat Transfer in Structures
NASA Technical Reports Server (NTRS)
Adelman, H. M. (Compiler)
1982-01-01
Techniques for the computation of heat transfer and associated phenomena in complex structures are examined with an emphasis on reentry flight vehicle structures. Analysis methods, computer programs, thermal analysis of large space structures and high speed vehicles, and the impact of computer systems are addressed.
Turbulent Heat Transfer in Ribbed Pipe Flow
NASA Astrophysics Data System (ADS)
Kang, Changwoo; Yang, Kyung-Soo
2012-11-01
From the view point of heat transfer control, surface roughness is one of the popular ways adopted for enhancing heat transfer in turbulent pipe flow. Such a surface roughness is often modeled with a rib. In the current investigation, Large Eddy Simulation has been performed for turbulent flow in a pipe with periodically-mounted ribs at Reτ=700, Pr=0.71, and p / k =2, 4, and 8. Here, p and k represent the pitch and rib height, respectively. The rib height is fixed as one tenth of the pipe radius. The profiles of mean velocity components, mean temperature, root-mean-squares (rms) of temperature fluctuation are presented at the selected streamwise locations. In comparison with the smooth-pipe case at the same Re and Pr, the effects of the ribs are clearly identified, leading to overall enhancement of turbulent heat transfer in terms of Nu. The budget of temperature variance is presented in the form of contours. The results of an Octant analysis are also given to elucidate the dominant events. Our LES results shed light on a complete understanding of the heat-transfer mechanisms in turbulent ribbed-pipe flow which has numerous applications in engineering. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2012013019).
Heat transfer in magma in situ
Dunn, J.C.; Carrigan, C.R.; Wemple, R.P.
1983-12-16
Heat transfer rates in a basaltic magma were measured under typical magma chamber conditions and a numerical model of the experiment was used to estimate magma viscosity. The results are of value for assessing methods of thermal energy extraction from magma bodies in the upper crust as well as for modeling the evolutionary track of these systems. 13 references, 3 figures.
FED. Zoning for TRUMP Heat Transfer Code
Elrod, D.
1987-10-23
FED reduces the effort required to obtain the necessary geometric input for problems which are to be solved using the heat-transfer code, TRUMP. TRUMP calculates transient and steady-state temperature distributions in multidimensional systems. FED can properly zone any body of revolution in one, two, or three dimensions.
Heat transfer in rotating coolant channels
NASA Astrophysics Data System (ADS)
Wang, Baoguan; Zheng, Jirui; Ding, Xiaojiang
The effect of cooling channels' rotation on the local and mean heat transfer is investigated using an experimental simulation of three types of flow in rotating circular tubes: (1) flow parallel to the rotating axis, (2) radially outward flow perpendicular to the rotating axis, and (3) radially inward flow perpendicular to the rotating axis. Theoretical analysis uses the boundary layer model method, in which the flow in a tube is divided into the core and boundary layer zones with different assumptions for each zone, and the equations are solved using the momentum integration method. Experimental results were obtained using a specially designed facility incorporating all three modes of flow. The results confirm that rotation of the flow in a tube can enhance the heat transfer processes whether the flow is parallel or perpendicular to the rotating axis. The incremental increase in heat transfer rate due to rotation was found to be more pronounced at low rotational speeds than at high speeds. The variation of local heat transfer coefficients along axial direction is affected by the inlet and outlet sections and by the ratio of length to diameter.
Heat Transfer and Thermodynamics: a Compilation
NASA Technical Reports Server (NTRS)
1974-01-01
A compilation is presented for the dissemination of information on technological developments which have potential utility outside the aerospace and nuclear communities. Studies include theories and mechanical considerations in the transfer of heat and the thermodynamic properties of matter and the causes and effects of certain interactions.
Forced Convection Heat Transfer in Circular Pipes
ERIC Educational Resources Information Center
Tosun, Ismail
2007-01-01
One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…
Information highway and numerical heat transfer
Shih, T.M.; Minkowycz, W.J.
1996-11-22
It is proposed that researchers in the numerical heat transfer community need to realize the trend of the information highway and agree to use a protocol or a module that constitutes the core of a computer program solving heat transfer problems. This will avoid duplicate programming and accelerate the technology advancement of numerical heat transfer. The module for two-dimensional incompressible Navier-Stokes flows is presented and explained. It is further demonstrated that, using this module as the foundation, the user can straightforwardly build up an entire personal computer code by inputting the data, specifying boundary conditions, and outputting the result. Other modules for slightly more complicated problems, such as transient flows with variable viscosity in irregular geometries, are also presented. Other than zoning matches for problems with multizones, the programming task for a user becomes minimal and simple: input, prescribe the boundary conditions, and output. The availability of Navier-Stokes modules is particularly helpful for less experienced numerical researchers, newcomers, and graduate students who have just entered the area of heat transfer and fluid flows.
Heat transfer in a nuclear rocket engine
Konyukhov, G.V.; Petrov, A.I.
1995-02-01
Special features of heat transfer in the reactor of a nuclear rocket engine (NRE) are dealt with. It is shown that the design of the cooling system of the NRE reactor is governed by its stability to small deviations of the parameters from the corresponding calculated values and the possibility of compensating for effects due to nonuniformities and distrubances of various types and scales.
NASA Astrophysics Data System (ADS)
Chen, Feng; Xu, Ai-Guo; Zhang, Guang-Cai; Gan, Yan-Biao; Cheng, Tao; Li, Ying-Jun
2009-10-01
We present a highly efficient lattice Boltzmann model for simulating compressible flows. This model is based on the combination of an appropriate finite difference scheme, a 16-discrete-velocity model [Kataoka and Tsutahara, Phys. Rev. E 69 (2004) 035701(R)] and reasonable dispersion and dissipation terms. The dispersion term effectively reduces the oscillation at the discontinuity and enhances numerical precision. The dissipation term makes the new model more easily meet with the von Neumann stability condition. This model works for both high-speed and low-speed flows with arbitrary specific-heat-ratio. With the new model simulation results for the well-known benchmark problems get a high accuracy compared with the analytic or experimental ones. The used benchmark tests include (i) Shock tubes such as the Sod, Lax, Sjogreen, Colella explosion wave, and collision of two strong shocks, (ii) Regular and Mach shock reflections, and (iii) Shock wave reaction on cylindrical bubble problems. With a more realistic equation of state or free-energy functional, the new model has the potential tostudy the complex procedure of shock wave reaction on porous materials.
Cooperative heat transfer and ground coupled storage system
Metz, P.D.
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
Cooperative heat transfer and ground coupled storage system
Metz, Philip D.
1982-01-01
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor
NASA Technical Reports Server (NTRS)
Golliher, Eric L.; Gotti, Daniel J.; Rymut, Joseph Edward; Nguyen, Brian K; Owens, Jay C.; Pace, Gregory S.; Fisher, John W.; Hong, Andrew E.
2013-01-01
This paper will discuss the status of microgravity analysis and testing for the development of a Heat Melt Compactor (HMC). Since fluids behave completely differently in microgravity, the evaporation process for the HMC is expected to be different than in 1-g. A thermal model is developed to support the design and operation of the HMC. Also, low-gravity aircraft flight data is described to assess the point at which water may be squeezed out of the HMC during microgravity operation. For optimum heat transfer operation of the HMC, the compaction process should stop prior to any water exiting the HMC, but nevertheless seek to compact as much as possible to cause high heat transfer and therefore shorter evaporation times.
BWR Core Heat Transfer Code System.
Energy Science and Technology Software Center (ESTSC)
1999-04-27
Version 00 MOXY is used for the thermal analysis of a planar section of a boiling water reactor (BWR) fuel element during a loss-of-coolant accident (LOCA). The code emplyoys models that describe heat transfer by conduction, convection, and thermal radiation, and heat generation by metal-water reaction and fission product decay. Models are included for considering fuel-rod swelling and rupture, energy transport across the fuel-to-cladding gap, and the thermal response of the canister. MOXY requires thatmore » time-dependent data during the blowdown process for the power normalized to the steady-state power, for the heat-transfer coefficient, and for the fluid temperature be provided as input. Internal models provide these parameters during the heatup and emergency cooling phases.« less
Advanced Heat Transfer and Thermal Storage Fluids
Moens, L.; Blake, D.
2005-01-01
The design of the next generation solar parabolic trough systems for power production will require the development of new thermal energy storage options with improved economics or operational characteristics. Current heat-transfer fluids such as VP-1?, which consists of a eutectic mixture of biphenyl and diphenyl oxide, allow a maximum operating temperature of ca. 300 C, a limit above which the vapor pressure would become too high and would require pressure-rated tanks. The use of VP-1? also suffers from a freezing point around 13 C that requires heating during cold periods. One of the goals for future trough systems is the use of heat-transfer fluids that can act as thermal storage media and that allow operating temperatures around 425 C combined with lower limits around 0 C. This paper presents an outline of our latest approach toward the development of such thermal storage fluids.
Numerical Modeling of Ablation Heat Transfer
NASA Technical Reports Server (NTRS)
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.
Heat transfer in bioengineering and medicine
Chato, J.C.; Diller, T.E.; Diller, K.R.; Roemer, R.B.
1987-01-01
This book contains the following papers: New ideas in heat transfer for agricultural animals; Issues in heat transfer and tumor blood flow in localized hyperthermia treatments of cancer; Ultrasound enhances adriamycin toxicity in vitro; Scanned, focused ultrasound hyperthermia treatment of brain tumors; Mathematical prediction and phantom studies of the clinical target ''hot spot'' using a three applicator phased array system (TRIPAS); Development of an endoscopic RF hyperthermia system for deep tumor therapy; Simultaneous measurement of intrinsic and effective thermal conductivity; Determination of the transport of thermal energy by conduction in perfused tissue; A whole body thermal model of man with a realistic circulatory system; and Canine muscle blood flow changes in response to initial heating rates.
NASA Astrophysics Data System (ADS)
Pohner, John A.; Dempsey, Brian P.; Herold, Leroy M.
1990-07-01
Space Station elements and advanced military spacecraft will require rejection of tens of kilowatts of waste heat. Large space radiators and two-phase heat transport loops will be required. To minimize radiator size and weight, it is critical to minimize the temperature drop between the heat source and sink. Under an Air Force contract, a unique, high-performance heat exchanger is developed for coupling the radiator to the transport loop. Since fluid flow through the heat exchanger is driven by capillary forces which are easily dominated by gravity forces in ground testing, it is necessary to perform microgravity thermal testing to verify the design. This contract consists of an experiment definition phase leading to a preliminary design and cost estimate for a shuttle-based flight experiment of this heat exchanger design. This program will utilize modified hardware from a ground test program for the heat exchanger.
NASA Technical Reports Server (NTRS)
Pohner, John A.; Dempsey, Brian P.; Herold, Leroy M.
1990-01-01
Space Station elements and advanced military spacecraft will require rejection of tens of kilowatts of waste heat. Large space radiators and two-phase heat transport loops will be required. To minimize radiator size and weight, it is critical to minimize the temperature drop between the heat source and sink. Under an Air Force contract, a unique, high-performance heat exchanger is developed for coupling the radiator to the transport loop. Since fluid flow through the heat exchanger is driven by capillary forces which are easily dominated by gravity forces in ground testing, it is necessary to perform microgravity thermal testing to verify the design. This contract consists of an experiment definition phase leading to a preliminary design and cost estimate for a shuttle-based flight experiment of this heat exchanger design. This program will utilize modified hardware from a ground test program for the heat exchanger.
Microscale Heat Transfer Transduced by Surface Plasmon Resonant Gold Nanoparticles
Roper, D. Keith; Ahn, W.; Hoepfner, M.
2008-01-01
Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ≤10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation equaled heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat by microvolume suspensions of gold nanoparticles was determined by applying an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Measured values of transduction efficiency were increased from 3.4% to 9.9% by modulating the incident continuous wave irradiation. PMID:19011696
Wildemeersch, S; Jamin, P; Orban, P; Hermans, T; Klepikova, M; Nguyen, F; Brouyère, S; Dassargues, A
2014-11-15
Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54MJ/m(3)/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for
Analysis of a heat transfer device for measuring film coefficients
NASA Technical Reports Server (NTRS)
Medrow, R. A.; Johnson, R. L.; Loomis, W. R.; Wedeven, L. D.
1975-01-01
A heat transfer device consisting of a heated rotating cylinder in a bath was analyzed for its effectiveness to determine heat transfer coefficient of fluids. A time dependent analysis shows that the performance is insensitive to the value of heat transfer coefficient with the given rig configuration.
Combined heat and mass transfer device for improving separation process
Tran, Thanh Nhon
1999-01-01
A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area.
Combined heat and mass transfer device for improving separation process
Tran, T.N.
1999-08-24
A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area. 12 figs.
Heterogeneous nanofluids: natural convection heat transfer enhancement
2011-01-01
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case. PMID:21711755
Heterogeneous nanofluids: natural convection heat transfer enhancement.
Oueslati, Fakhreddine Segni; Bennacer, Rachid
2011-01-01
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case. PMID:21711755
Heterogeneous nanofluids: natural convection heat transfer enhancement
NASA Astrophysics Data System (ADS)
Oueslati, Fakhreddine Segni; Bennacer, Rachid
2011-12-01
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration φ and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case.
Unsteady heat transfer during subcooled film boiling
NASA Astrophysics Data System (ADS)
Yagov, V. V.; Zabirov, A. R.; Lexin, M. A.
2015-11-01
Cooling of high-temperature bodies in subcooled liquid is of importance for quenching technologies and also for understanding the processes initiating vapor explosion. An analysis of the available experimental information shows that the mechanisms governing heat transfer in these processes are interpreted ambiguously; a more clear-cut definition of the Leidenfrost temperature notion is required. The results of experimental observations (Hewitt, Kenning, and previous investigations performed by the authors of this article) allow us to draw a conclusion that there exists a special mode of intense heat transfer during film boil- ing of highly subcooled liquid. For revealing regularities and mechanisms governing intense transfer of energy in this process, specialists of Moscow Power Engineering Institute's (MPEI) Department of Engineering Thermal Physics conduct systematic works aimed at investigating the cooling of high-temperature balls made of different metals in water with a temperature ranging from 20 to 100°C. It has been determined that the field of temperatures that takes place in balls with a diameter of more than 30 mm in intense cooling modes loses its spherical symmetry. An approximate procedure for solving the inverse thermal conductivity problem for calculating the heat flux density on the ball surface is developed. During film boiling, in which the ball surface temperature is well above the critical level for water, and in which liquid cannot come in direct contact with the wall, the calculated heat fluxes reach 3-7 MW/m2.
Full Eulerian lattice Boltzmann model for conjugate heat transfer
NASA Astrophysics Data System (ADS)
Hu, Yang; Li, Decai; Shu, Shi; Niu, Xiaodong
2015-12-01
In this paper a full Eulerian lattice Boltzmann model is proposed for conjugate heat transfer. A unified governing equation with a source term for the temperature field is derived. By introducing the source term, we prove that the continuity of temperature and its normal flux at the interface is satisfied automatically. The curved interface is assumed to be zigzag lines. All physical quantities are recorded and updated on a Cartesian grid. As a result, any complicated treatment near the interface is avoided, which makes the proposed model suitable to simulate the conjugate heat transfer with complex interfaces efficiently. The present conjugate interface treatment is validated by several steady and unsteady numerical tests, including pure heat conduction, forced convection, and natural convection problems. Both flat and curved interfaces are also involved. The obtained results show good agreement with the analytical and/or finite volume results.
Full Eulerian lattice Boltzmann model for conjugate heat transfer.
Hu, Yang; Li, Decai; Shu, Shi; Niu, Xiaodong
2015-12-01
In this paper a full Eulerian lattice Boltzmann model is proposed for conjugate heat transfer. A unified governing equation with a source term for the temperature field is derived. By introducing the source term, we prove that the continuity of temperature and its normal flux at the interface is satisfied automatically. The curved interface is assumed to be zigzag lines. All physical quantities are recorded and updated on a Cartesian grid. As a result, any complicated treatment near the interface is avoided, which makes the proposed model suitable to simulate the conjugate heat transfer with complex interfaces efficiently. The present conjugate interface treatment is validated by several steady and unsteady numerical tests, including pure heat conduction, forced convection, and natural convection problems. Both flat and curved interfaces are also involved. The obtained results show good agreement with the analytical and/or finite volume results. PMID:26764851
Acquisition systems for heat transfer measurement
De Witt, R.J.
1983-01-01
Practical heat transfer data acquisition systems are normally characterized by the need for high-resolution, low-drift, low-speed recording devices. Analog devices such as strip chart or circular recorders and FM analog magnetic tape have excellent resolution and work well when data will be presented in temperature versus time format only and need not be processed further. Digital systems are more complex and require an understanding of the following components: digitizing devices, interface bus types, processor requirements, and software design. This paper discusses all the above components of analog and digital data acquisition, as they are used in current practice. Additional information on thermocouple system analysis will aid the user in developing accurate heat transfer measuring systems.
Heat transfer performance of a novel double-layer mini-channel heat sink
NASA Astrophysics Data System (ADS)
Tang, Biao; Zhou, Rui; Bai, Pengfei; Fu, Ting; Lu, Longsheng; Zhou, Guofu
2016-07-01
High pressure drop and significant non-uniformity in temperature distribution along the streamwise direction are still challenges to the design of mini-channel heat sink. High density mini-channel arrays with high liquid-wall contact area are usually pursued in a conventional single-layer design of heat sink, which also inevitably brings high pressure drop. A novel double-layer structured heat sink is proposed in this paper. Four heat sinks with various designs in mini-channel density and flow direction were fabricated and studied experimentally on the heat transfer performance. The single factor of heat load does not show obvious effect on the overall thermal resistance of the heat sinks. On the other hand, slight decrease in thermal resistance was found with the increase in heat load at high flow rates. Moreover, a computational fluid dynamics modeling work was conducted. The results indicate that the parallel cross-flow field regulated by the double-layer structure enhances the heat exchange in both horizontal and vertical directions and consequently gives an uniform temperature distribution and high heat transfer efficiency.
Modeling heat transfer within porous multiconstituent materials
NASA Astrophysics Data System (ADS)
Niezgoda, Mathieu; Rochais, Denis; Enguehard, Franck; Rousseau, Benoit; Echegut, Patrick
2012-06-01
The purpose of our work has been to determine the effective thermal properties of materials considered heterogeneous at the microscale but which are regarded as homogenous in the macroscale environment in which they are used. We have developed a calculation code that renders it possible to simulate thermal experiments over complex multiconstituent materials from their numerical microstructural morphology obtained by volume segmentation through tomography. This modeling relies on the transient solving of the coupled conductive and radiative heat transfer in these voxelized structures.
Heat and mass transfer in materials processing
Tanasawa, I. . Inst. of Industrial Science); Lior, N. . Dept. of Mechanical Engineering and Applied Mechanics)
1992-01-01
This book contains forty papers presented at the seminar. The papers are representative of the seminar's scope, and include plasma spraying, laser and electron beam processing, crystal growth, solidification, steel processing, casting and molding, and papermaking, as well as fundamental heat transfer issues and physical properties underlying all of the above. The seminar emphasized thorough discussion of the presentations and of the subfields. Brief summaries of the discussions are presented in the rapporteurs' reports.
Radiation heat transfer shapefactors for combustion systems
NASA Technical Reports Server (NTRS)
Emery, A. F.; Johansson, O.; Abrous, A.
1987-01-01
The computation of radiation heat transfer through absorbing media is commonly done through the zoning method which relies upon values of the geometric mean transmittance and absorptance. The computation of these values is difficult and expensive, particularly if many spectral bands are used. This paper describes the extension of a scan line algorithm, based upon surface-surface radiation, to the computation of surface-gas and gas-gas radiation transmittances.
Heat Transfer in a Superelliptic Transition Duct
NASA Technical Reports Server (NTRS)
Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven
2008-01-01
Local heat transfer measurements were experimentally mapped using a transient liquid-crystal heat transfer technique on the surface of a circular-to-rectangular transition duct. The transition duct had a length-to-diameter ratio of 1.5 and an exit-plane aspect ratio of 3. The crosssectional geometry was defined by the equation of a superellipse. The cross-sectional area was the same at the inlet and exit but varied up to 15 percent higher through the transition. The duct was preheated to a uniform temperature (nominally 64 C) before allowing room temperature air to be suddenly drawn through it. As the surface cooled, the resulting isothermal contours on the duct surface were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the surface temperature and time data for all points on the duct surfaces during each test. Using this surface temperature-time data together with the temperature of the air flowing through the model and the initial temperature of the model wall, the heat transfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heat transfer conduction model. Test results are reported for inlet diameter-based Reynolds numbers ranging from 0.4x106 to 2.4x106 and two grid-generated freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.
Coolant passage heat transfer with rotation
NASA Astrophysics Data System (ADS)
Hajek, T. J.; Higgins, A. W.
1985-10-01
The objective is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques, and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.
Low-melting point heat transfer fluid
Cordaro, Joseph Gabriel; Bradshaw, Robert W.
2010-11-09
A low-melting point, heat transfer fluid made of a mixture of five inorganic salts including about 29.1-33.5 mol % LiNO.sub.3, 0-3.9 mol % NaNO.sub.3, 2.4-8.2 mol % KNO.sub.3, 18.6-19.9 mol % NaNO.sub.2, and 40-45.6 mol % KNO.sub.2. These compositions can have liquidus temperatures below 80.degree. C. for some compositions.
Dust as a Working Fluid for Heat Transfer Project
NASA Technical Reports Server (NTRS)
Mantovani, James G.
2015-01-01
The project known as "Dust as a Working Fluid" demonstrates the feasibility of a dust-based system for transferring heat radiatively into space for those space applications requiring higher efficiency, lower mass, and the need to operate in extreme vacuum and thermal environments - including operating in low or zero gravity conditions in which the dust can be conveyed much more easily than on Earth.
Parallel and vector computation in heat transfer
Georgiadis, J.G. ); Murthy, J.Y. )
1990-01-01
This collection of manuscripts complements a number of other volumes related to engineering numerical analysis in general; it also gives a preview of the potential contribution of vector and parallel computing to heat transfer. Contributions have been made from the fields of heat transfer, computational fluid mechanics or physics, and from researchers in industry or in academia. This work serves to indicate that new or modified numerical algorithms have to be developed depending on the hardware used (as the long titles of most of the papers in this volume imply). This volume contains six examples of numerical simulation on parallel and vector computers that demonstrate the competitiveness of the novel methodologies. A common thread through all the manuscripts is that they address problems involving irregular geometries or complex physics, or both. Comparative studies of the performance of certain algorithms on various computers are also presented. Most machines used in this work belong to the coarse- to medium-grain group (consisting of a few to a hundred processors) with architectures of the multiple-instruction-stream-multiple- data-stream (MIMD) type. Some of the machines used have both parallel and vector processors, while parallel computations are certainly emphasized. We hope that this work will contribute to the increasing involvement of heat transfer specialists with parallel computation.
Enhanced condensation heat transfer with wettability patterning
NASA Astrophysics Data System (ADS)
Sinha Mahapatra, Pallab; Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine
2015-11-01
Condensation of water vapor on metal surfaces is useful for many engineering applications. A facile and scalable method is proposed for removing condensate from a vertical plate during dropwise condensation (DWC) in the presence of non-condensable gases (NCG). We use wettability-patterned superhydrophilic tracks (filmwise condensing domains) on a mirror-finish (hydrophilic) aluminum surface that promotes DWC. Tapered, horizontal ``collection'' tracks are laid to create a Laplace pressure driven flow, which collects condensate from the mirror-finish domains and sends it to vertical ``drainage tracks'' for gravity-induced shedding. An optimal design is achieved by changing the fractional area of superhydrophilic tracks with respect to the overall plate surface, and augmenting capillary-driven condensate-drainage by adjusting the track spatial layout. The design facilitates pump-less condensate drainage and enhances DWC heat transfer on the mirror-finish regions. The study highlights the relative influences of the promoting and retarding effects of dropwise and filmwise condensation zones on the overall heat transfer improvement on the substrate. The study demonstrated ~ 34% heat transfer improvement on Aluminum surface for the optimized design.
Pressure loss and heat transfer in a toothed finned heat transfer medium
NASA Astrophysics Data System (ADS)
Ebeling, W. D.; Leidinger, B. J. G.
Thermohydraulic investigation was carried out in a special toothed-finned geometry, which was provided for increasing heat transfer in an evaporator cooler. The evaporator cooler has applications in space navigation. The toothed-finned heat carrier was used in a counter current, with a view to simplifying the heat transfer coefficient evaluation, from the temperature and volume flows measured. Test results obtained confirmed the suitability of this test arrangement. Relationships were derived from test results, for the pressure loss coefficient and the Nusselt number, with regard to the Reynolds number for this determined finned geometry.
Two Heat-Transfer Improvements for Gas Liquefiers
NASA Technical Reports Server (NTRS)
Martin, Jerry L.
2005-01-01
Two improvements in heat-transfer design have been investigated with a view toward increasing the efficiency of refrigerators used to liquefy gases. The improvements could contribute to the development of relatively inexpensive, portable oxygen liquefiers for medical use. A description of the heat-transfer problem in a pulse-tube refrigerator is prerequisite to a meaningful description of the first improvement. In a pulse-tube refrigerator in particular, one of in-line configuration heat must be rejected from two locations: an aftercooler (where most of the heat is rejected) and a warm heat exchanger (where a small fraction of the total input power must be rejected as heat). Rejection of heat from the warm heat exchanger can be problematic because this heat exchanger is usually inside a vacuum vessel. When an acoustic-inertance tube is used to provide a phase shift needed in the pulse-tube cooling cycle, another problem arises: Inasmuch as the acoustic power in the acoustic-inertance tube is dissipated over the entire length of the tube, the gas in the tube must be warmer than the warm heat exchanger in order to reject heat at the warm heat exchanger. This is disadvantageous because the increase in viscosity with temperature causes an undesired increase in dissipation of acoustic energy and an undesired decrease in the achievable phase shift. Consequently, the overall performance of the pulse-tube refrigerator decreases with increasing temperature in the acoustic-inertance tube. In the first improvement, the acoustic-inertance tube is made to serve as the warm heat exchanger and to operate in an approximately isothermal condition at a lower temperature, thereby increasing the achievable phase shift and the overall performance of the refrigerator. This is accomplished by placing the acoustic-inertance tube inside another tube and pumping a cooling fluid (e.g., water) in the annular space between the tubes. Another benefit of this improvement is added flexibility of
Visualization study on pool boiling heat transfer
NASA Astrophysics Data System (ADS)
Kamei, Shuya; Hirata, Masaru
1991-04-01
The visualized boiling phenomena were observed by means of high speed photographic shadowgraphy using a rotating prism camera (nac HIGH SPEED CAMERA model-16HD) with the speed of about 3500 frames per second. The photographs show that pool boiling heat transfer phenomena are varied for the boiling curve based on the experiments. Experiments have been carried out to investigate pool boiling heat transfer phenomena on a horizontal thin filament in subcooled and saturated distilled water. The experiments were performed for atmospheric pressure,for filament diameters of about 0.3 mm, for region of natural convection to film boiling. The color-film made by high speed movie camera are converted to high speed color video-tape. It is convenient to edit and show the tape for visualization with teaching the students. The high speed color video showed that the successive motion and shape of bubbles during their process of detachment varied with increasing heat flux on the heated surface of a filament. From these results, it was confirmed that the high speed phenomena of boiling by the slow motion video pictures could be estimated clearly.
High heat transfer oxidizer heat exchanger design and analysis. [RL10-2B engine
NASA Technical Reports Server (NTRS)
Kmiec, Thomas D.; Kanic, Paul G.; Peckham, Richard J.
1987-01-01
The RL10-2B engine, a derivative of the RL10, is capable of multimode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2% of full thrust, and pumped idle (PI), which is 10% of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for low-g deployment. Stable combustion of the RL10-2B engine during the low thrust operating modes can be accomplished by using a heat exchanger to supply gaseous oxygen to the propellant injector. The oxidizer heat exchanger (OHE) vaporizes the liquid oxygen using hydrogen as the energy source. The design, concept verification testing and analysis for such a heat exchanger is discussed. The design presented uses a high efficiency compact core to vaporize the oxygen, and in the self-contained unit, attenuates any pressure and flow oscillations which result from unstable boiling in the core. This approach is referred to as the high heat transfer design. An alternative approach which prevents unstable boiling of the oxygen by limiting the heat transfer is referred to as the low heat transfer design and is reported in Pratt & Whitney report FR-19135-2.
An experimental study of the flow and heat transfer between enhanced heat transfer plates for PHEs
Li, Xiao-wei; Meng, Ji-an; Li, Zhi-xin
2010-11-15
The flow and heat transfer between inclined discrete rib plates for plate heat exchangers have been experimentally studied. Dye injection method is used to visualize the flow structures. The visualization results show that front vortex, rear vortex and main vortex are formed between the plates. The rib parameter influence is also studied using visualization method. The pressure drop and heat transfer between the inclined discrete rib plates as well as that between inclined continuous rib plates and smooth plates are also measured. The measured results show that the inclined discrete rib plate can enhanced heat transfer 20-25% at the same pumping power compared with the commonly used inclined continuous rib plates. (author)
Heat transfer characteristics of tube bundles during boiling in vacuum
NASA Astrophysics Data System (ADS)
Slesarenko, V. N.; Zakharov, G. A.
1992-06-01
Heat transfer during boiling in vacuum was compared experimentally for single tubes, rows of tube, and tube bundles to analyze characteristic properties of vaporization under such conditions. Relations for calculating heat transfer coefficients are proposed.
Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)
Not Available
2010-08-01
Fact sheet describing NREL CSP Program capabilities in the area of thermal storage and advanced heat transfer fluids: measuring thermophysical properties, measuring fluid flow and heat transfer, and simulating flow of thermal energy and fluid.
A multilevel method for conductive-radiative heat transfer
Banoczi, J.M.; Kelley, C.T.
1996-12-31
We present a fast multilevel algorithm for the solution of a system of nonlinear integro-differential equations that model steady-state combined radiative-conductive heat transfer. The equations can be formulated as a compact fixed point problem with a fixed point map that requires both a solution of the linear transport equation and the linear heat equation for its evaluation. We use fast transport solvers developed by the second author, to construct an efficient evaluation of the fixed point map and then apply the Atkinson-Brakhage, method, with Newton-GMRES as the coarse mesh solver, to the full nonlinear system.
Radiative heat transfer between two dielectric-filled metal gratings
NASA Astrophysics Data System (ADS)
Dai, J.; Dyakov, S. A.; Yan, M.
2016-04-01
Nanoscale surface corrugation is known to be able to drastically enhance radiative heat transfer between two metal plates. Here we numerically calculate the radiative heat transfer between two dielectric-filled metal gratings at dissimilar temperatures based on a scattering approach. It is demonstrated that, compared to unfilled metal gratings, the heat flux for a fixed geometry can be further enhanced, by up to 650% for the geometry separated by a vacuum gap of g =1 μ m and temperature values concerned in our study. The enhancement in radiative heat transfer is found to depend on refractive index of the filling dielectric, the specific grating temperatures, and naturally the gap size between the two gratings. The enhancement can be understood through examining the transmission factor spectra, especially the spectral locations of the spoof surface plasmon polariton modes. Of more practical importance, it's shown that the radiative heat flux can exceed that between two planar SiC plates with same thickness, separation, and temperature settings over a wide temperature range. This reaffirms that one can harness rich electromagnetic modal properties in nanostructured materials for efficient thermal management at nanoscale.
Heat and mass transfer over slippery, superhydrophobic surfaces
NASA Astrophysics Data System (ADS)
Haase, A. Sander; Lammertink, Rob G. H.
2016-04-01
The classical Graetz-Nusselt problem is extended to describe heat and mass transfer over heterogeneously slippery, superhydrophobic surfaces. The cylindrical wall consists of segments with a constant temperature/concentration and areas that are insulating/impermeable. Only in the case of mass transport do the locations of hydrodynamic slip and mass exchange coincide. This makes advection near the mass exchanging wall segments larger than near the heat exchanging regions. Also the direction of radial fluid flow is reversed for heat and mass transport, which has an influence on the location where the concentration or temperature boundary layer is compressed or extended. As a result, mass transport is more efficient than heat transfer. Also the influence of axial diffusion on the Nusselt and Sherwood numbers is investigated for various Péclet numbers Pe. When Pe < 102, which is characteristic for heat transfer over superhydrophobic surfaces, axial conduction should be taken into account. For Pe ≥ 102, which are typical numbers for mass transport in microfluidic systems, axial diffusion can be neglected.
The heat recovery with heat transfer methods from solar photovoltaic systems
NASA Astrophysics Data System (ADS)
Özakın, A. N.; Karsli, S.; Kaya, F.; Güllüce, H.
2016-04-01
Although there are many fluctuations in energy prices, they seems like rising day by day. Thus energy recovery systems have increasingly trend. Photovoltaic systems converts solar radiation directly into electrical energy thanks to semiconductors. But due to the nature of semiconductors, whole of solar energy cannot turn into electrical energy and the remaining energy turns into waste heat. The aim of this research is evaluate this waste heat energy by air cooling system. So, the energy efficiency of the system will be increased using appropriate heat transfer technologies such as fin, turbulator etc.
NASA Astrophysics Data System (ADS)
Kanzaka, Mitsuo; Iwabuchi, Makio
1992-11-01
Heat transfer characteristics in heated tubes under periodically reversing flow conditions have been experimentally investigated, using a test apparatus that simulates heat exchangers for an actual Stirling engine. It is shown that the heat transfer characteristics under these conditions are greatly affected by the piston phase difference that generates the reversing flow of working fluid, and this phenomenon is peculiar to heat transfer under periodically reversing flow. The experimental correlation for the heat transfer coefficient under these conditions is obtained through the use of the working gas velocity evaluated from the Schmidt cycle model, which is one of the ideal Stirling cycles concerning the influence of the piston phase difference.
Measuring Furnace/Sample Heat-Transfer Coefficients
NASA Technical Reports Server (NTRS)
Rosch, William R.; Fripp, Archibald L., Jr.; Debnam, William J., Jr.; Woodell, Glenn A.
1993-01-01
Complicated, inexact calculations now unnecessary. Device called HTX used to simulate and measure transfer of heat between directional-solidification crystal-growth furnace and ampoule containing sample of crystalline to be grown. Yields measurement data used to calculate heat-transfer coefficients directly, without need for assumptions or prior knowledge of physical properties of furnace, furnace gas, or specimen. Determines not only total heat-transfer coefficients but also coefficients of transfer of heat in different modes.
NASA Astrophysics Data System (ADS)
Hou, Xiuhui; Deng, Zichen; Yin, Guansheng
2014-12-01
The thermal properties for the multi-re-entrant honeycomb are investigated, where the hexagon and re-entrant topologies are applied for comparison. A compact model was adopted for the local heat transfer rate and pressure drop estimations while the total heat transfer rate was analyzed using the transfer matrix method. A thermal performance index was specified to characterize a good heat exchange medium that can transfer more heat at the expense of lower pressure loss. Numerical results reveal better thermal performances of multi-re-entrant honeycombs over hexagon and re-entrant topologies, attributed to the presence of added base walls. Auxetic effect introduced in multi-re-entrant honeycomb generally provides enhanced out-of-plane thermal conductivity and increased total heat transfer efficiency due to higher surface area density.
Condensing heat exchangers for maximum boiler efficiency
Johnson, D.W.; DiVitto, J.G.; Rakocy, M.E.
1994-12-31
Until now, boiler efficiency has been limited due to the minimum temperature allowed at the stack. Heat lost up the stack was in exchange for keeping the flue gas temperature above the water vapor dew point. If water vapor was allowed to condense out, rapid deterioration, due to acid corrosion, of the outlet duct and stack would result. With the development of the condensing heat exchanger, boiler efficiency can now exceed 90%. Approximately 1% gain in boiler efficiency can be expected for every 40 F (4.5 C) reduction in flue gas stack temperature. In the CHX{reg_sign} condensing heat exchanger, all gas wetted surfaces are covered with DuPont Teflon{reg_sign}. The Teflon covered heat exchanger surfaces are impervious to all acids normally resulting from the combustion of fossil fuels. This allows the flue gas to be cooled to below the water vapor dew point with no subsequent corrosion of the heat exchanger surfaces.
Various methods to improve heat transfer in exchangers
NASA Astrophysics Data System (ADS)
Pavel, Zitek; Vaclav, Valenta
2015-05-01
The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.
NASA Astrophysics Data System (ADS)
Shokati, Naser; Mohammadkhani, Farzad; Farrokhi, Navid; Ranjbar, Faramarz
2014-12-01
During manufacture of engines, evaluation of engine performance is essential. This is accomplished in test cells. During the test, a significant portion of heat energy released by the fuel is wasted. In this study, in order to recover these heat losses, Organic Rankine Cycle (ORC) is recommended. The study has been conducted assuming the diesel oil to be composed of a single hydrocarbon such as C12H26. The composition of exhaust gases (products of combustion) have been computed (and not determined experimentally) from the stoichiometric equation representing the combustion reaction. The test cell heat losses are recovered in three separate heat exchangers (preheater, evaporator and superheater). These heat exchangers are separately designed, and the whole system is analyzed from energy and exergy viewpoints. Finally, a parametric study is performed to investigate the effect of different variables on the system performance characteristics such as the ORC net power, heat exchangers effectiveness, the first law efficiency, exergy destruction and heat transfer surfaces. The results of the study show that by utilizing ORC, heat recovery equivalent to 8.85 % of the engine power is possible. The evaporator has the highest exergy destruction rate, while the pump has the lowest among the system components. Heat transfer surfaces are calculated to be 173.6, 58.7, and 11.87 m2 for the preheater, evaporator and superheater, respectively.
Heat Transfer Through Turbulent Friction Layers
NASA Technical Reports Server (NTRS)
Reichardt, H.
1943-01-01
The "general Prandtl number" Pr(exp 1) - A(sub q)/A Pr, aside from the Reynolds number determines the ratio of turbulent to molecular heat transfer, and the temperature distribution in turbulent friction layers. A(sub q) = exchange coefficient for heat; A = exchange coefficient for momentum transfer. A formula is derived from the equation defining the general Prandtl number which describes the temperature as a function of the velocity. For fully developed thermal boundary layers all questions relating to heat transfer to and from incompressible fluids can be treated in a simple manner if the ratio of the turbulent shear stress to the total stress T(sub t)/T in the layers near the wall is known, and if the A(sub q)/A can be regarded as independent of the distance from the wall. The velocity distribution across a flat smooth channel and deep into the laminar sublayer was measured for isothermal flow to establish the shear stress ratio T(sub t)/T and to extend the universal wall friction law. The values of T(sub t)/T which resulted from these measurements can be approximately represented by a linear function of the velocity in the laminar-turbulent transition zone. The effect of the temperature relationship of the material values on the flow near the wall is briefly analyzed. It was found that the velocity at the laminar boundary (in contrast to the thickness of the laminar layer) is approximately independent of the temperature distribution. The temperature gradient at the wall and the distribution of temperature and heat flow in the turbulent friction layers were calculated on the basis of the data under two equations. The derived formulas and the figures reveal the effects of the Prandtl number, the Reynolds number, the exchange quantities and the temperature relationship of the material values.
Enhancement of heat and mass transfer by cavitation
NASA Astrophysics Data System (ADS)
Zhang, Y. N.; Zhang, Y. N.; Du, X. Z.; Xian, H. Z.
2015-01-01
In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment.
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
ERIC Educational Resources Information Center
Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.
2010-01-01
This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…
Film-Cooling Heat-Transfer Measurements Using Liquid Crystals
NASA Technical Reports Server (NTRS)
Hippensteele, Steven A.
1997-01-01
The following topics are discussed: (1) The Transient Liquid-Crystal Heat-Transfer Technique; (2) 2-D Film-Cooling Heat-Transfer on an AlliedSignal Vane; and (3) Effects of Tab Vortex Generators on Surface Heat Transfer. Downstream of a Jet in Crossflow.
High efficiency pump for space helium transfer
NASA Technical Reports Server (NTRS)
Hasenbein, Robert; Izenson, Michael G.; Swift, Walter L.; Sixsmith, Herbert
1991-01-01
A centrifugal pump was developed for the efficient and reliable transfer of liquid helium in space. The pump can be used to refill cryostats on orbiting satellites which use liquid helium for refrigeration at extremely low temperatures. The pump meets the head and flow requirements of on-orbit helium transfer: a flow rate of 800 L/hr at a head of 128 J/kg. The overall pump efficiency at the design point is 0.45. The design head and flow requirements are met with zero net positive suction head, which is the condition in an orbiting helium supply Dewar. The mass transfer efficiency calculated for a space transfer operation is 0.99. Steel ball bearings are used with gas fiber-reinforced teflon retainers to provide solid lubrication. These bearings have demonstrated the longest life in liquid helium endurance tests under simulated pumping conditions. Technology developed in the project also has application for liquid helium circulation in terrestrial facilities and for transfer of cryogenic rocket propellants in space.
NASA Astrophysics Data System (ADS)
Yankovskii, A. P.
2015-07-01
The author has obtained equations describing thermal conductivity of composite bodies spatially reinforced with a system of smooth tubes in which an incompressible liquid heat-transfer agent is pumped in a developed turbulent regime. The corresponding boundary-value heat-conduction problem was formulated and its qualitative analysis was made. Specific calculations were performed for steady-state temperature fields in cylindrical concrete shells spirally reinforced with steel tubes through which a heat-transfer agent (air) is pumped. A study has been made of the influence of the reinforcement parameters and of the velocity and direction of the heat-transfer agent in the tubes and the dimensions of their cross sections on the temperature field. It has been established that variation of these characteristics enables one to substantially change the intensity of heat removal from the shells, opening up wide opportunities for efficient control of the heat transfer in them.
Energy transfer simulation for radiantly heated and cooled enclosures
Chapman, K.S.; Zhang, P.
1996-11-01
This paper presents the development of a three-dimensional mathematical model to compute heat transfer within a radiantly heated or cooled room, which then calculates the mass-averaged room air temperature and the wall surface temperature distributions. The radiation formulation used in the model accommodates arbitrary placement of walls and objects within the room. The convection model utilizes Nusselt number correlations published in the open literature. The complete energy transfer model is validated by comparing calculated room temperatures to temperatures measured in a radiantly heated room. This three-dimensional model may be applied to a building to assist the heating/cooling system design engineer in sizing a radiant heating/cooling system. By coupling this model with a thermal comfort model, the comfort levels throughout the room can be easily and efficiently mapped for a given radiant heater/cooler location. In addition, obstacles such as airplanes, trucks, furniture, and partitions can be easily incorporated to determine their effect on the radiant heating system performance.
Liquid metal heat exchanger for efficient heating of soils and geologic formations
DeVault, Robert C [Knoxville, TN; Wesolowski, David J [Kingston, TN
2010-02-23
Apparatus for efficient heating of subterranean earth includes a well-casing that has an inner wall and an outer wall. A heater is disposed within the inner wall and is operable within a preselected operating temperature range. A heat transfer metal is disposed within the outer wall and without the inner wall, and is characterized by a melting point temperature lower than the preselected operating temperature range and a boiling point temperature higher than the preselected operating temperature range.
Heat transfer model for quenching by submerging
NASA Astrophysics Data System (ADS)
Passarella, D. N.; Varas, F.; Martín, E. B.
2011-05-01
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Thermochromic liquid crystals in heat transfer research
NASA Astrophysics Data System (ADS)
Stasiek, Jan A.; Kowalewski, Tomasz A.
2002-06-01
In recent years Thermochromic Liquid Crystals (TLC) have been successfully used in non-intrusive heat transfer and fluid mechanics studies. Thin coatings of TLC's at surfaces is utilized to obtain detailed heat transfer data of steady or transient process. Application of TLC tracers allows instantaneous measurement of the temperature and velocity fields for two-dimensional cross-section of flow. Computerized flow visualization techniques allow automatic quantification of temperature of the analyzed surface or the visualized flow cross-section. Here we describe our experience in applying the method to selected problems studied in our laboratory. They include modeling flow configurations in the differentially heated inclined cavity with vertical temperature gradient simulating up-slope flow as well as thermal convection under freezing surface. The main aim of these experimental models is to generate reliable experimental database on velocity and temperature fields for specific flow. The methods are based on computerized true-color analysis of digital images for temperature measurements and modified Particle Image Velocimetry and Thermometry (PIVT) used to obtain the flow field velocity.
Laminar heat transfer in annular sector ducts
Soliman, H.M. )
1987-02-01
The continuing interest in compact heat exchangeers has created the need for friction factor and Nusselt number data for different passage shapes. It has long been recognized that circular tube results are generally not applicable to noncircular passages even when the hydraulic diameter is used as the characteristic dimension. Hence, design data should be generated for each passage individually, and a good source of such information is Shah and London. One duct geometry for which complete design information does not appear to be available in the open literature is that of annular sector ducts. Such configuration is encountered in multipassage internally finned tubes and many other compact het exchanger applications. The fluid flow problem for this configuration has been solved by Sparrow et al., and more recently by Niida. However, to the beest of the author's knowledge, the heat transfer results are not available yet. The purpose of this note is to summarize the analysis and results of fluid flow and heat transfer in annular sector ducts.
Heat transfer to a supercritical hydrocarbon fuel with endothermic reaction.
Yu, W.; France, D. M.; Wambsganss, M. W.; Energy Technology; Univ. of Illinois at Chicago
2000-01-01
Supercritical fuel reforming is being studied as a technology for reducing emissions of industrial gas turbine engines. In this study, experiments were performed in a 2.67-mm-inside-diameter stainless steel tube with a heated length of 0.610 m for the purpose of investigating the characteristics of supercritical heat transfer with endothermic fuel reforming. Thermocouples were positioned along the tube both in the fluid stream and on the heated wall for local heat transfer measurements. Both heat transfer coefficients and endotherms were calculated from the measured results. State-of-the-art correlations for heat transfer were evaluated, and a correlation for supercritical heat transfer to hydrocarbon fuel has been developed. The results provide a basis for supercritical fuel heat-exchanger/reactor design and its practical applications, in an area that has received relatively little attention in the engineering literature, viz., supercritical forced convection heat transfer with endothermic chemical reaction.
A Model of Respiratory Heat Transfer in a Small Mammal
Collins, J. C.; Pilkington, T. C.; Schmidt-Nielsen, K.
1971-01-01
A steady-state model of the heat and water transfer occurring in the upper respiratory tract of the kangaroo rat, Dipodomys spectabilis, is developed and tested. The model is described by a steady-state energy balance equation in which the rate of energy transfer from a liquid stream (representing the flow of heat and blood from the body core to the nasal region) is equated with the rate of energy transfer by thermal conduction from the nose tip to the environment. All of the variables in the equation except the flow rate of the liquid stream can be either measured directly or estimated from physiological measurements, permitting the solution of the equation for the liquid stream flow rate. After solving for the liquid stream flow rate by using data from three animals, the energy balance equation is used to compute values of energy transfer, expired air temperature, rates of water loss, and efficiency of vapor recovery for a variety of ambient conditions. These computed values are compared with values measured or estimated from physiological measurements on the same three animals, and the equation is thus shown to be internally consistent. To evaluate the model's predictive value, calculated expired air temperatures are compared with measured expired air temperatures of eight additional animals. Finally, the model is used to examine the general dependence of expired air temperature, of rates of water loss, and of efficiency of vapor recovery on ambient conditions. PMID:5113001
Scaling of heat transfer in granular material in rotating drums
NASA Astrophysics Data System (ADS)
Yohannes, Bereket; Emady, Heather; Pardes, Ingrid; Javed, Maham; Borghard, William; Glasser, Benjamin; Muzzio, Fernando; Cuitino, Alberto
Several industrial processes involve thermal treatment of granular materials and powders, in devices such as rotating drums, to bring about a desired chemical and/or physical transformation. Developing a better understanding of the heat transfer process can significantly improve the quality of the end product and efficiency. However, there is a lack of predictive models, for example, to predict the evolution of the distribution and average of the particles' temperature, particularly for the purposes of scale-up from laboratory scale experiments to manufacturing scale productions. We used discrete element method (DEM) based simulations to study the distribution of particles' temperature in rotating drums at low temperature. Various physical, mechanical, and thermal properties of particles were considered in the simulations and in the analysis. In addition, the effect of operating conditions such as size of drum, material fill level, and speed of rotation on the heat transfer were investigated. Based on the simulations, we identified timescales relevant to the heat transfer process and developed a relationship between these timescales that can be used to predict the average temperature of particles. We also found that the evolution of the temperature distribution, since different particles may have different temperatures, can be predicted based on these timescales. These findings can be used to predict the required time to heat up all particles to the desired temperature.
Advances in refrigeration and heat transfer engineering
Bansal, Pradeep; Cremaschi, Prof. Lorenzo
2015-05-13
This special edition of Science and Technology for the Built Environment (STBE) presents selected high quality papers that were presented at the 15th International Refrigeration and Air Conditioning Conference held at Purdue University during July 14-17 2014. All papers went through the additional review before being finally accepted for publication in this special issue of Science and Technology and the Built Environment. Altogether 20 papers made to this special issue that cover a wide range of topics, including advancements in alternative refrigerants, heat exchangers/heat transfer, nano-fluids, systems design and optimization and modeling approaches. Although CO2 may perhaps have been themore » most researched and popular refrigerant in the past decade, R32 is being seriously considered lately as an alternative and environmentally friendly refrigerant for small systems due to its low Global Warming Potential (GWP).« less
USINT. Heat and Mass Transfer In Concrete
Eyberger, L.R.
1989-12-01
USINT was developed to model the thermal response of concrete to very high heating rates such as might occur from sodium spills on concrete surfaces in a breeder reactor. The major phenomena treated are conductive energy transport; chemical decomposition of concrete; and two-phase, three-component heat and mass transfer of the decomposition products: steam, liquid water, and carbon dioxide. The USINT model provides for porosity to increase as water and carbon-dioxide are formed from the concrete. The concrete is treated generally as divided into two basic regions, wet and dry. In the wet region, steam, carbon-dioxide, and liquid water may co-exist, but in the dry region, there is no liquid water. There is also the possibility of a third region in which there is only liquid water and no gases.
USINT. Heat and Mass Transfer in Concrete
Beck, J.V.; Knight, R.L.
1989-12-01
USINT was developed to model the thermal response of concrete to very high heating rates such as might occur from sodium spills on concrete surfaces in a breeder reactor. The major phenomena treated are conductive energy transport; chemical decomposition of concrete; and two-phase, three-component heat and mass transfer of the decomposition products: steam, liquid water, and carbon dioxide. The USINT model provides for porosity to increase as water and carbon-dioxide are formed from the concrete. The concrete is treated generally as divided into two basic regions, wet and dry. In the wet region, steam, carbon-dioxide, and liquid water may co-exist, but in the dry region, there is no liquid water. There is also the possibility of a third region in which there is only liquid water and no gases.
3-D Finite Element Heat Transfer
Energy Science and Technology Software Center (ESTSC)
1992-02-01
TOPAZ3D is a three-dimensional implicit finite element computer code for heat transfer analysis. TOPAZ3D can be used to solve for the steady-state or transient temperature field on three-dimensional geometries. Material properties may be temperature-dependent and either isotropic or orthotropic. A variety of time-dependent and temperature-dependent boundary conditions can be specified including temperature, flux, convection, and radiation. By implementing the user subroutine feature, users can model chemical reaction kinetics and allow for any type of functionalmore » representation of boundary conditions and internal heat generation. TOPAZ3D can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in the material surrounding the enclosure. Additional features include thermal contact resistance across an interface, bulk fluids, phase change, and energy balances.« less
Advances in refrigeration and heat transfer engineering
Bansal, Pradeep; Cremaschi, Prof. Lorenzo
2015-05-13
This special edition of Science and Technology for the Built Environment (STBE) presents selected high quality papers that were presented at the 15th International Refrigeration and Air Conditioning Conference held at Purdue University during July 14-17 2014. All papers went through the additional review before being finally accepted for publication in this special issue of Science and Technology and the Built Environment. Altogether 20 papers made to this special issue that cover a wide range of topics, including advancements in alternative refrigerants, heat exchangers/heat transfer, nano-fluids, systems design and optimization and modeling approaches. Although CO_{2} may perhaps have been the most researched and popular refrigerant in the past decade, R32 is being seriously considered lately as an alternative and environmentally friendly refrigerant for small systems due to its low Global Warming Potential (GWP).
Heat transfer augmentation in nanofluids via nanofins.
Vadasz, Peter
2011-01-01
Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C. Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins. The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism. PMID:21711695
Heat transfer augmentation in nanofluids via nanofins
2011-01-01
Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C. Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heat transfer augmentation via nanofins. The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism. PMID:21711695
Solar Pond Fluid Dynamics and Heat Transfer
NASA Technical Reports Server (NTRS)
Jones, G. F.
1984-01-01
The primary objective of the solar pond research was to obtain an indepth understanding of solar pond fluid dynamics and heat transfer. The key product was the development of a validated one-dimensional computer model with the capability to accurately predict time-dependent solar pond temperature, salinities, and interface motions. Laboratory scale flow visualization experiments were conducted to better understand layer motion. Two laboratory small-scale ponds and a large-scale outdoor solar pond were designed and built to provide quantitative data. This data provided a basis for validating the model and enhancing the understanding of pond dynamic behavior.
Porous media heat transfer for injection molding
Beer, Neil Reginald
2016-05-31
The cooling of injection molded plastic is targeted. Coolant flows into a porous medium disposed within an injection molding component via a porous medium inlet. The porous medium is thermally coupled to a mold cavity configured to receive injected liquid plastic. The porous medium beneficially allows for an increased rate of heat transfer from the injected liquid plastic to the coolant and provides additional structural support over a hollow cooling well. When the temperature of the injected liquid plastic falls below a solidifying temperature threshold, the molded component is ejected and collected.
Investigation of heat transfer in the petal detector structure
NASA Astrophysics Data System (ADS)
Lávička, David; Kňourek, Jindřich
2016-03-01
This paper describes the CFD numerical simulation of heat transfer in the petal complex structure. Petal consists of core structure and detectors designed to improve the detection capabilities of the ATLAS detector and take advantage of operating at the High Luminosity LHC (HL-LHC). New generation silicon detectors in the petal require more efficient cooling of the front-end electronics and the silicon sensors themselves. To minimize reverse annealing of the silicon sensors the operating temperatures need to be reduced. In this case the evaporative CO2 cooling medium is used as it is ideal for this purpose. This work describes the flow simulation setup and results for the current prototype and heat transfer behavior for different operating states.
Rocket engine thrust chamber heat transfer calculation and analysis
NASA Technical Reports Server (NTRS)
Saha, H.
1974-01-01
A parametric study of the heat transfer rate along the wall of a rocket nozzle is presented. The influences of different parameters; laminar and turbulent Lewis number, mixture ratio, initial wall temperature distribution, and eddy viscosity, were considered. The numerical evaluation of these influences on heat transfer rate was done by using three different compressible, reacting laminar and turbulent boundary layer computer programs; MABL (Mass Addition Boundary Layer Program), MABL-KE (MABL program is modified to include turbulent kinetic energy equation), and BLIMP (Boundary Layer Integral Matrix Procedure). This study also provided an excellent opportunity to evaluate the efficiencies of these three computer programs and to suggest one of them for future computational purposes.
A review of turbine blade tip heat transfer.
Bunker, R S
2001-05-01
This paper presents a review of the publicly available knowledge base concerning turbine blade tip heat transfer, from the early fundamental research which laid the foundations of our knowledge, to current experimental and numerical studies utilizing engine-scaled blade cascades and turbine rigs. Focus is placed on high-pressure, high-temperature axial-turbine blade tips, which are prevalent in the majority of today's aircraft engines and power generating turbines. The state of our current understanding of turbine blade tip heat transfer is in the transitional phase between fundamentals supported by engine-based experience, and the ability to a priori correctly predict and efficiently design blade tips for engine service. PMID:11460670
Van der Waals interaction-tuned heat transfer in nanostructures
NASA Astrophysics Data System (ADS)
Sun, Tao; Wang, Jianxiang; Kang, Wei
2012-12-01
Interfaces usually impede heat transfer in heterogeneous structures. Recent experiments show that van der Waals (vdW) interactions can significantly enhance thermal conductivity parallel to the interface of a bundle of nanoribbons compared to a single layer of freestanding nanoribbon. In this paper, by simulating heat transfer in nanostructures based on a model of nonlinear one-dimensional lattices interacting via van der Waals interactions, we show that the vdW interface interaction can adjust the thermal conductivity parallel to the interface. The efficiency of the adjustment depends on the intensity of interactions and temperature. The nonlinear dependence of the conductivity on the intensity of interactions agrees well with experimental results for carbon nanotube bundles, multi-walled carbon nanotubes, multi-layer graphene, and nanoribbons.
Glycol coolants improve heat transfer and corrosion control
Holfield, R.
1995-03-01
Various liquids from plain water to exotic fluids have been used as coolants in large stationary diesel engines that drive compressors on natural gas pipeline distribution systems. Although water is an efficient heat transfer medium, its drawbacks of freezing at {minus}32 F and boiling at 212 F seriously limit its usefulness. Special glycol-based heat transfer fluids are available and refined specifically for long-term needs of gas compressor engines. Appropriate corrosion inhibitors have been formulated for metallurgy and operating conditions encountered with these engines. Propylene glycol was developed as an alternative for use in environmentally sensitive areas. Glycol-based fluids must be specifically inhibited for industrial applications because uninhibited or improperly inhibited coolants can seriously damage reciprocating engines.
Flow and heat transfer in a curved channel
NASA Technical Reports Server (NTRS)
Brinich, P. F.; Graham, R. W.
1977-01-01
Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.
Heat transfer analysis in rotating sphericall shells
NASA Astrophysics Data System (ADS)
Cabello, Ares; Avila, Ruben
2015-11-01
The study of flow patterns within rotating spherical annular geometries with natural convection, is essential to understand the internal dynamics of the planets. We investigate the convective flows and the heat transfer rate in an spherical gap in which a temperature difference between the inner sphere and the outer sphere is present. A self gravity field which varies as a function of 1 /rn (where r is the radial position and the integer exponent n has the values 2,3,4,5) is assumed. The Boussinesq fluid equations are solved by using a spectral element method (SEM). To avoid the singularity at the poles, the cubed-sphere algorithm is used to generate the spherical mesh. Heat fluxes at the surface of both spheres are analyzed. We find, for several Ekman and Rayleigh numbers, that there exists a high correlation between the azimuthal motion of both the Busse cells and the zones where the maximum surface heat fluxes occur. The azimuthal position, as a function of time, of the maximum heat flux zones (which are located symmetrically with respect to the equator), allows to speculate on the nature of the phenomena occurring (in geological times) on the surface of the terrestrial planets. Thanks to DGAPA-PAPIIT project: IN117314-3.
Nanoscale heat transfer and phase transformation surrounding intensely heated nanoparticles
NASA Astrophysics Data System (ADS)
Sasikumar, Kiran
Over the last decade there has been significant ongoing research to use nanoparticles for hyperthermia-based destruction of cancer cells. In this regard, the investigation of highly non-equilibrium thermal systems created by ultrafast laser excitation is a particularly challenging and important aspect of nanoscale heat transfer. It has been observed experimentally that noble metal nanoparticles, illuminated by radiation at the plasmon resonance wavelength, can act as localized heat sources at nanometer-length scales. Achieving biological response by delivering heat via nanoscale heat sources has also been demonstrated. However, an understanding of the thermal transport at these scales and associated phase transformations is lacking. A striking observation made in several laser-heating experiments is that embedded metal nanoparticles heated to extreme temperatures may even melt without an associated boiling of the surrounding fluid. This unusual phase stability is not well understood and designing experiments to understand the physics of this phenomenon is a challenging task. In this thesis, we will resort to molecular dynamics (MD) simulations, which offer a powerful tool to investigate this phenomenon, without assumptions underlying continuum-level model formulations. We present the results from a series of steady state and transient non-equilibrium MD simulations performed on an intensely heated nanoparticle immersed in a model liquid. For small nanoparticles (1-10 nm in diameter) we observe a stable liquid phase near the nanoparticle surface, which can be at a temperature well above the boiling point. Furthermore, we report the existence of a critical nanoparticle size (4 nm in diameter) below which we do not observe formation of vapor even when local fluid temperatures exceed the critical temperature. Instead, we report the existence of a stable fluid region with a density much larger than that of the vapor phase. We explain this stability in terms of the
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht
2007-10-03
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in ancircular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.
NASA Technical Reports Server (NTRS)
Throckmorton, D. A.; Zoby, E. V.; Hamilton, H. H., II
1983-01-01
During that portion of Space Shuttle orbiter entry when significant aerodynamic heat transfer occurs, the flow over the vehicle is in chemical nonequilibrium. The parameter which most significantly influences the level of surface heat transfer in such a flow field is the catalytic efficiency of the surface with respect to the recombination of dissociated oxygen atoms. Significant, and instantaneous, changes were observed in the level of heat transfer at several lower surface centerline locations on STS-2 and STS-3. This phenomenon apparently resulted from a sudden change in the surface catalytic efficiency at these locations due to contamination of the surface by metallic oxides. As a result, data obtained from affected measurements cannot be considered as benchmark data with which to attempt to characterize nonequilibrium heat transfer to the orbiter's lower surface centerline.
Heat Transfer in High Temperature Multilayer Insulation
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Miller, Steve D.; Cunnington, George R.
2007-01-01
High temperature multilayer insulations have been investigated as an effective component of thermal-protection systems for atmospheric re-entry of reusable launch vehicles. Heat transfer in multilayer insulations consisting of thin, gold-coated, ceramic reflective foils and Saffil(TradeMark) fibrous insulation spacers was studied both numerically and experimentally. A finite volume numerical thermal model using combined conduction (gaseous and solid) and radiation in porous media was developed. A two-flux model with anisotropic scattering was used for radiation heat transfer in the fibrous insulation spacers between the reflective foils. The thermal model was validated by comparison with effective thermal conductivity measurements in an apparatus based on ASTM standard C201. Measurements were performed at environmental pressures in the range from 1x10(exp -4) to 760 torr over the temperature range from 300 to 1300 K. Four multilayer samples with nominal densities of 48 kg/cu m were tested. The first sample was 13.3 mm thick and had four evenly spaced reflective foils. The other three samples were 26.6 mm thick and utilized either one, two, or four reflective foils, located near the hot boundary with nominal foil spacing of 1.7 mm. The validated thermal model was then used to study relevant design parameters, such as reflective foil spacing and location in the stack-up and coating of one or both sides of foils.
Nucleation and Heat Transfer in Liquid Nitrogen
NASA Astrophysics Data System (ADS)
Roth, Eric Warner
1993-01-01
With the advent of the new high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions are examined. Using a metal hot wire/plate technique, it is verified that there is a premature transition to film boiling in the transient case at power levels as much as 30 percent lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity. The second part of this research analyses the nucleation (boiling) process from a dynamical systems point of view. By observing how the boiling system variables evolve and fluctuate over time, it is hoped that physical insight and predictive information can be gained. One goal is to discover some indicator or signature in the data that anticipates the transition from nucleate boiling to film boiling. Some of the important variables that make up the boiling system are the temperature of the heater and the heat flux through the heater surface into the liquid nitrogen. The result, gained by plotting the system's trajectory in the heat flux-temperature plane, is that on average the system follows a counterclockwise trajectory. A physical model is constructed that explains this behavior. Also, as the applied heater power approaches levels at which the transition to film is known to occur, the area per unit time swept out in the heat flux-temperature plane is seen to reach a maximum. This could be of practical interest as the threshold to film boiling can be anticipated and possibly prevented.