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Sample records for melting heat transfer

  1. Low-melting point heat transfer fluid

    DOEpatents

    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.

  2. Low-melting point heat transfer fluid

    DOEpatents

    Cordaro, Joseph G [Oakland, CA; Bradshaw, Robert W [Livermore, CA

    2011-04-12

    A low-melting point, heat transfer fluid comprising a mixture of LiNO.sub.3, NaNO.sub.3, KNO.sub.3, NaNO.sub.2 and KNO.sub.2 salts where the Li, Na and K cations are present in amounts of about 20-33.5 mol % Li, about 18.6-40 mol % Na, and about 40-50.3 mol % K and where the nitrate and nitrite anions are present in amounts of about 36-50 mol % NO.sub.3, and about 50-62.5 mol % NO.sub.2. These compositions can have liquidus temperatures between 70.degree. C. and 80.degree. C. for some compositions.

  3. 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.

  4. Analytical approach for the effect of melting heat transfer on nanofluid heat transfer

    NASA Astrophysics Data System (ADS)

    Sheikholeslami, M.; Nimafar, M.; Ganji, D. D.

    2017-09-01

    In this article, the impact of melting heat transfer on nanofluid flow in the presence of Lorentz forces is reported. Different shapes of nanoparticles are considered. The impacts of Joule heating, viscous dissipation and thermal radiation are added in the governing equations. The Homotopy Analysis Method (HAM) is selected to solve Ordinary Differential Equations (ODEs). The roles of nanofluid volume fraction, shape of the nanoparticles, Hartmann number, porosity parameter, melting parameter, Eckert number are presented graphically. The results reveal that choosing a platelet shape leads to the maximum Nusselt number. The temperature reduces with the rise of the melting parameter but velocity increases with the increase of the melting parameter. Nu augments with the increase of the Lorentz forces while it reduces with the augment of porosity and melting parameters.

  5. Low-melting point inorganic nitrate salt heat transfer fluid

    DOEpatents

    Bradshaw, Robert W.; Brosseau, Douglas A.

    2009-09-15

    A low-melting point, heat transfer fluid made of a mixture of four inorganic nitrate salts: 9-18 wt % NaNO.sub.3, 40-52 wt % KNO.sub.3, 13-21 wt % LiNO.sub.3, and 20-27 wt % Ca(NO.sub.3).sub.2. These compositions can have liquidus temperatures less than 100 C; thermal stability limits greater than 500 C; and viscosity in the range of 5-6 cP at 300 C; and 2-3 cP at 400 C.

  6. Modeling and database for melt-water interfacial heat transfer

    SciTech Connect

    Farmer, M.T.; Spencer, B.W.; Schneider, J.P.; Bonomo, B.; Theofanous, G.

    1992-04-01

    A mechanistic model is developed to predict the transition superficial gas velocity between bulk cooldown and crust-limited heat transfer regimes in a sparged molten pool with a coolant overlayer. The model has direct applications in the analysis of ex-vessel severe accidents, where molten corium interacts with concrete, thereby producing sparging concrete decomposition gases. The analysis approach embodies thermal, mechanical, and hydrodynamic aspects associated with incipient crust formation at the melt/coolant interface. The model is validated against experiment data obtained with water (melt) and liquid nitrogen (coolant) simulants. Predictions are then made for the critical gas velocity at which crust formation will occur for core material interacting with concrete in the presence of water.

  7. Modeling and database for melt-water interfacial heat transfer

    SciTech Connect

    Farmer, M.T.; Spencer, B.W. ); Schneider, J.P. ); Bonomo, B. ); Theofanous, G. )

    1992-01-01

    A mechanistic model is developed to predict the transition superficial gas velocity between bulk cooldown and crust-limited heat transfer regimes in a sparged molten pool with a coolant overlayer. The model has direct applications in the analysis of ex-vessel severe accidents, where molten corium interacts with concrete, thereby producing sparging concrete decomposition gases. The analysis approach embodies thermal, mechanical, and hydrodynamic aspects associated with incipient crust formation at the melt/coolant interface. The model is validated against experiment data obtained with water (melt) and liquid nitrogen (coolant) simulants. Predictions are then made for the critical gas velocity at which crust formation will occur for core material interacting with concrete in the presence of water.

  8. An analytical and experimental investigation of melting heat transfer

    NASA Astrophysics Data System (ADS)

    Wen, C.; Sheffield, J. W.; O'dell, M. P.; Leland, J. E.

    1988-01-01

    A computational model is presented for the prediction of the heat transfer between a heat transfer fluid (HTF) and a phase change material (PCM) of a latent heat storage unit. Two models of flow, hydrodynamically fully developed flow and developing flow, of the HTF were proposed in this study. A two-dimensional enthalpy method was used for the computation of the phase change heat transfer in the PCM. A fully implicit finite difference scheme was utilized for the calculation of convective heat transfer in the HTF. The unknown time dependent boundary condition between the HTF and the PCM was found iteratively. The predictions are substantiated by their excellent agreement with experimental data. Factors which affect the heat transfer rates between the HTF and the PCM were studied numerically for both hydrodynamically fully developed flow and developing flow. It is found that the Nusselt number is significantly increased by the developing temperature profiles. The developing velocity profiles also will increase the Nusselt number. However, the influence on Nusselt number due to the developing temperature profiles. Other factors which affect the Nusselt number are discussed. The heat transfer of this latent heat storage unit was also studied experimentally. The experimental results were compared with the numerical results for P116, a sun wax.

  9. Modeling of heat and mass transfer processes during core melt discharge from a reactor pressure vessel

    SciTech Connect

    Dinh, T.N.; Bui, V.A.; Nourgaliev, R.R.

    1995-09-01

    The objective of the paper is to study heat and mass transfer processes related to core melt discharge from a reactor vessel is a severe light water reactor accident. The phenomenology of the issue includes (1) melt convection in and heat transfer from the melt pool in contact with the vessel lower head wall; (2) fluid dynamics and heat transfer of the melt flow in the growing discharge hole; and (3) multi-dimensional heat conduction in the ablating lower head wall. A program of model development, validation and application is underway (i) to analyse the dominant physical mechanisms determining characteristics of the lower head ablation process; (ii) to develop and validate efficient analytic/computational methods for estimating heat and mass transfer under phase-change conditions in irregular moving-boundary domains; and (iii) to investigate numerically the melt discharge phenomena in a reactor-scale situation, and, in particular, the sensitivity of the melt discharge transient to structural differences and various in-vessel melt progression scenarios. The paper presents recent results of the analysis and model development work supporting the simulant melt-structure interaction experiments.

  10. Studying regimes of convective heat transfer in the production of high-temperature silicate melts

    NASA Astrophysics Data System (ADS)

    Volokitin, O. G.; Sheremet, M. A.; Shekhovtsov, V. V.; Bondareva, N. S.; Kuzmin, V. I.

    2016-09-01

    The article presents the results of theoretical and experimental studies of the production of high-temperature silicate melts using the energy of low-temperature plasma in a conceptually new setup. A mathematical model of unsteady regimes of convective heat and mass transfer is developed and numerically implemented under the assumption of non-Newtonian nature of flow in the melting furnace with plasma-chemical synthesis of high-temperature silicate melts. Experiments on melting silicate containing materials were carried out using the energy of low-temperature plasma. The dependence of dynamic viscosity of various silicate materials (basalt, ash, waste of oil shale) was found experimentally.

  11. Two phase modeling of nanofluid flow in existence of melting heat transfer by means of HAM

    NASA Astrophysics Data System (ADS)

    Sheikholeslami, M.; Jafaryar, M.; Bateni, K.; Ganji, D. D.

    2017-08-01

    In this article, Buongiorno Model is applied for investigation of nanofluid flow over a stretching plate in existence of magnetic field. Radiation and Melting heat transfer are taken into account. Homotopy analysis method (HAM) is selected to solve ODEs which are obtained from similarity transformation. Roles of Brownian motion, thermophoretic parameter, Hartmann number, porosity parameter, Melting parameter and Eckert number are presented graphically. Results indicate that nanofluid velocity and concentration enhance with rise of melting parameter. Nusselt number reduces with increase of porosity and melting parameters.

  12. Heat and mass transfer in semiconductor melts during single-crystal growth processes

    NASA Astrophysics Data System (ADS)

    Kakimoto, Koichi

    1995-03-01

    The quality of large semiconductor crystals grown from melts is significantly affected by the heat and mass transfer in the melts. The current understanding of the phenomena, especially melt convection, is reviewed starting from the results of visualization using model fluids or silicon melt, and continuing to the detailed numerical calculations needed for quantitative modeling of processing with solidification. The characteristics of silicon flows are also reviewed by focusing on the Coriolis force in the rotating melt. Descriptions of flow instabilities are included that show the level of understanding of melt convection with a low Prandtl number. Based on hydrodynamics, the origin of the silicon flow structure is reviewed, and it is discussed whether silicon flow is completely turbulent or has an ordered structure. The phase transition from axisymmetric to nonaxisymmetric flow is discussed using different geometries. Additionally, surface-tension-driven flow is reviewed for Czochralski crystal growth systems.

  13. Heat-transfer analysis of the basal melting of Antarctic ice shelves

    SciTech Connect

    Minale, M.; Astarita, G.

    1993-12-01

    Basal melting of Antarctic ice shelves is an important element in the overall balance of Antarctic ice. A heat-transfer model for the basal melting of the Drygalski Ice Tongue is presented. The model does not contain any adjustable parameter. The calculated basal melting rate agrees very well with the value estimated from an overall ice balance on the ice tongue. It is concluded that relatively simple concepts of transport phenomena may be used to model some important features of the dynamics of the Antarctic ice sheet.

  14. On heat transfer characteristics of real and simulant melt pool experiments

    SciTech Connect

    Dinh, T.N.; Nourgaliev R.R.; Sehgal, B.R.

    1995-09-01

    The paper presents results of analytical studies of natural convection heat transfer in scaled and/or simulant melt pool experiments related to the PWR in-vessel melt retention issue. Specific reactor-scale effects of a large decay-heated core melt pool in the reactor pressure vessel lower plenum are first reviewed, and then the current analytical capability of describing physical processes under prototypical situations is examined. Experiments and experimental approaches are analysed by focusing on their ability to represent prototypical situations. Calculations are carried out in order to assess the significance of some selected effects, including variations in melt properties, pool geometry and heating conditions. Rayleigh numbers in the present analysis are limited to 10{sup 12}, where uncertainties in turbulence modeling are not overriding other uncertainties. The effects of fluid Prandtl number on heat transfer to the lowermost part of cooled pool walls are examined for square and semicircular cavities. Calculations are performed also to explore limitations of using side-wall heating and direct electrical heating in reproducing the physical picture of interest. Needs for further experimental and analytical efforts are discussed as well.

  15. Radiation effects on stagnation point flow with melting heat transfer and second order slip

    NASA Astrophysics Data System (ADS)

    Mabood, F.; Shafiq, A.; Hayat, T.; Abelman, S.

    This article examines the effects of melting heat transfer and thermal radiation in stagnation point flow towards a stretching/shrinking surface. Mathematical formulation is made in the presence of mass transfer and second order slip condition. Numerical solutions to the resulting nonlinear problems are obtained by Runge-Kutta fourth fifth order method. Physical quantities like velocity, temperature, concentration, skin friction, Nusselt and Sherwood number are analyzed via sundry parameters for stretching/shrinking, first order slip, second order slip, radiation, melting, Prandtl and Schmidt. A comparative study with the previously published results in limiting sense is made.

  16. Melting heat transfer in an axisymmetric stagnation-point flow of the Jeffrey fluid

    NASA Astrophysics Data System (ADS)

    Nawaz, M.; Hayat, T.; Zeeshan, A.

    2016-03-01

    This investigation explores the characteristics of melting heat transfer in a boundary layer flow of the Jeffrey fluid near the stagnation point on a stretching sheet subject to an applied magnetic field. The governing boundary layer equations are transformed to ordinary differential equations by similarity transformations. Resulting nonlinear problems are solved analytically by the homotopy analysis method. It is noticed that an increase in the melting parameter decreases the dimensionless velocity and temperature, while an increase in the Deborah number increases the velocity and momentum boundary layer thickness.

  17. A computational model for viscous fluid flow, heat transfer, and melting in in situ vitrification melt pools

    SciTech Connect

    McHugh, P.R.; Ramshaw, J.D.

    1991-11-01

    MAGMA is a FORTRAN computer code designed to viscous flow in in situ vitrification melt pools. It models three-dimensional, incompressible, viscous flow and heat transfer. The momentum equation is coupled to the temperature field through the buoyancy force terms arising from the Boussinesq approximation. All fluid properties, except density, are assumed variable. Density is assumed constant except in the buoyancy force terms in the momentum equation. A simple melting model based on the enthalpy method allows the study of the melt front progression and latent heat effects. An indirect addressing scheme used in the numerical solution of the momentum equation voids unnecessary calculations in cells devoid of liquid. Two-dimensional calculations can be performed using either rectangular or cylindrical coordinates, while three-dimensional calculations use rectangular coordinates. All derivatives are approximated by finite differences. The incompressible Navier-Stokes equations are solved using a new fully implicit iterative technique, while the energy equation is differenced explicitly in time. Spatial derivatives are written in conservative form using a uniform, rectangular, staggered mesh based on the marker and cell placement of variables. Convective terms are differenced using a weighted average of centered and donor cell differencing to ensure numerical stability. Complete descriptions of MAGMA governing equations, numerics, code structure, and code verification are provided. 14 refs.

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

    PubMed

    Hashim; Khan, Masood; Saleh Alshomrani, Ali

    2017-01-01

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

  19. Heat Transfer in Waste Glass Melts - Measurement and Implications for Nuclear Waste Vitrification

    NASA Astrophysics Data System (ADS)

    Wang, Chuan

    Thermal properties of waste glass melts, such as high temperature density and thermal conductivity, are relevant to heat transfer processes in nuclear waste vitrification. Experimental measurement techniques were developed and applied to four nuclear waste glasses representative of those currently projected for treatment of Hanford HLW and LAW streams to study heat flow mechanisms in nuclear waste vitrification. Density measurement results by Archimedes' method indicated that densities of the melts investigated varied considerably with composition and temperature. Thermal diffusivities of waste melts were determined at nominal melter operating temperatures using a temperature-wave technique. Thermal conductivities were obtained by combining diffusivity data with the experimentally-acquired densities of the melts and their known heat capacities. The experimental results display quite large positive dependences of conductivities on temperature for some samples and much weaker positive temperature dependences for others. More importantly, there is observed a big change in the slopes of the conductivities versus temperature as temperature is increased for two of the melts, but not for the other two. This behavior was interpreted in terms of the changing contributions of radiation and conduction with temperature and composition dependence of the absorption coefficient. Based on the obtained thermal conductivities, a simple model for a waste glass melter was set up, which was used to analyze the relative contributions of conduction and radiation individually and collectively to the overall heat flow and to investigate factors and conditions that influence the radiation contribution to heat flow. The modeling results showed that unlike the case at lower temperatures, the radiant energy flow through waste melts could be predominant compared with conduction at temperature of about 900 °C or higher. However, heat flow due to radiation was roughly equal to that from

  20. Heat transfer enhancement of PCM melting in 2D horizontal elliptical tube using metallic porous matrix

    NASA Astrophysics Data System (ADS)

    Jourabian, Mahmoud; Farhadi, Mousa; Rabienataj Darzi, Ahmad Ali

    2016-12-01

    In this study, the melting process of ice as a phase-change material (PCM) saturated with a nickel-steel porous matrix inside a horizontal elliptical tube is investigated. Due to the low thermal conductivity of the PCM, it is motivated to augment the heat transfer performance of the system simultaneously by finding an optimum value of the aspect ratio and impregnating a metallic porous matrix into the base PCM. The lattice Boltzmann method with a double distribution function formulated based on the enthalpy method, is applied at the representative elementary volume scale under the local thermal equilibrium assumption between the PCM and porous matrix in the composite. While reducing or increasing the aspect ratio of the circular tubes leads to the expedited melting, the 90° inclination of each elliptical tube in the case of the pure PCM melting does not affect the melting rate. With the reduction in the porosity, the effective thermal conductivity and melting rate in all tubes promoted. Although the natural convection is fully suppressed due to the significant flow blockage in the porous structure, the melting rates are generally increased in all cases.

  1. Melting heat transfer in stagnation point flow of carbon nanotubes towards variable thickness surface

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Muhammad, Khursheed; Farooq, M.; Alsaedi, A.

    2016-01-01

    This work concentrates on the mathematical modeling for stagnation point flow of nanofluids over an impermeable stretching sheet with variable thickness. Carbon nanotubes [single-wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs)] as the nanoparticles are utilized. Water and kerosene oil are taken as the base fluids. Heat transfer through melting effect is discussed. Transformation procedure is adapted to obtain the non-linear ordinary differential equations from the fundamental laws of mass, linear momentum and energy. The optimal values of convergence control parameters and corresponding individual and total residual errors for SWCNTs and MWCNTs are computed by means of homotopy analysis method (HAM) based BVPh 2.0. Characteristics of different involved parameters on the velocity, temperature, skin friction coefficient and Nusselt number are discussed. Higher velocity profile is observed for wall thickness parameter in case of water carbon nanotubes when compared with the kerosene oil carbon nanotubes.

  2. Melting of nanoparticle-enhanced phase change material inside an enclosure heated by laminar heat transfer fluid flow

    NASA Astrophysics Data System (ADS)

    Elbahjaoui, Radouane; El Qarnia, Hamid; El Ganaoui, Mohammed

    2016-05-01

    The proposed work presents a numerical investigation of the melting of a phase change material (PCM: Paraffin wax P116) dispersed with nanoparticles (Al2O3) in a latent heat storage unit (LHSU). The latter is composed of a number of vertical and identical slabs of nano-enhanced phase change material (NEPCM) separated by rectangular channels through which passes heat transfer fluid (HTF: water). A mathematical model based on the conservation equations of mass, momentum and energy has been developed. The resulting equations are discretized using the finite volume approach. The numerical model has been validated by experimental and numerical results published in literature. Numerical investigations have been conducted to evaluate the effects of the volumetric fraction of nanoparticles, HTF mass flow rate and inlet temperature on the latent heat storage unit's thermal behaviour and performance. Modelling results show that the volumetric fraction, HTF mass flow rate and inlet temperature need to be designed to achieve a significant improvement in thermal performance. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  3. Melting heat transfer in the MHD flow of a third-grade fluid over a variable-thickness surface

    NASA Astrophysics Data System (ADS)

    Hayat, Tasawar; Kiran, Asmara; Imtiaz, Maria; Alsaedi, Ahmed; Ayub, M.

    2017-06-01

    The present study addresses the magnetohydrodynamic (MHD) flow of a third-grade fluid over a nonlinear stretched surface with variable thickness. The heat transfer phenomenon is discussed through melting. The system of nonlinear ordinary differential equations is attained by considering proper transformations. Convergent series solutions of velocity and temperature are developed. Fluid flow, temperature, skin friction coefficient and Nusselt number are examined through graphs for different parameters. It is noted that velocity and temperature decrease with decreasing the wall thickness parameter. It is also revealed that the temperature distribution enhances for increasing values of the Prandtl number. Here the velocity field reduces for increasing values of the melting parameter.

  4. Multiple Solutions of an Unsteady Stagnation-Point Flow with Melting Heat Transfer in a Darcy-Brinkman Porous Medium

    NASA Astrophysics Data System (ADS)

    Khalid Aurangzaib, M.; Bhattacharyya, Krishnendu; Shafie, Sharidan

    2016-06-01

    The characteristics of the unsteady boundary layer flow with melting heat transfer near a stagnation-point towards a flat plate embedded in a DarcyBrinkman porous medium with thermal radiation are investigated. The governing partial differential equations are transformed into self-similar ordinary differential equations by similarity transformations. The transformed self-similar equations are solved numerically using bvp4c from Matlab for several values of the flow parameters. The study reveals that the multiple solutions exist for the decelerating (A < 0) flow, whereas for the accelerating (A ≥ 0) flow, the solution is unique. The results also indicate that the melting phenomenon increases the rate of heat transfer and delays the boundary layer separation. To validate the current numerical results, comparison with available results is made and found to be in a good agreement.

  5. Characteristics of magnetic field and melting heat transfer in stagnation point flow of Tangent-hyperbolic liquid

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Shafiq, Anum; Alsaedi, A.

    2016-05-01

    This paper examines the influence of melting heat transfer in the stagnation point flow of an incompressible magnetohydrodynamic (MHD) Tangent hyperbolic fluid. Stretched flow by a vertical surface is considered. Inclined nature of magnetic field is taken for an electrically conducting liquid. The resulting non-linear differential systems are computed for the convergent series solutions. Influences of various pertinent parameters like Weissenberg, magnetic, melting, ratio, angle of inclination, mixed convection, Eckert and Prandtl on the velocity and temperature are analyzed. Numerical data for various parameters on skin friction coefficient and local Nusselt number is also examined. It is found that the melting parameter reduces the temperature and thermal boundary layer while it shows opposite behavior for the velocity. Mixed convection has different role in the assisting and opposing flows.

  6. Numerical analysis of fluid flow and heat transfer during melting inside a cylindrical container for thermal energy storage system

    NASA Astrophysics Data System (ADS)

    Bellan, Selvan; Cheok, Cho Hyun; Gokon, Nobuyuki; Matsubara, Koji; Kodama, Tatsuya

    2017-06-01

    This paper presents a numerical analysis of unconstrained melting of high temperature(>1000K) phase change material (PCM) inside a cylindrical container. Sodium chloride and Silicon carbide have been used as phase change material and shell of the capsule respectively. The control volume discretization approach has been used to solve the conservation equations of mass, momentum and energy. The enthalpy-porosity method has been used to track the solid-liquid interface of the PCM during melting process. Transient numerical simulations have been performed in order to study the influence of radius of the capsule and the Stefan number on the heat transfer rate. The simulation results show that the counter-clockwise Buoyancy driven convection over the top part of the solid PCM enhances the melting rate quite faster than the bottom part.

  7. Thermal Conductive Heat Transfer and Partial Melting of Volatiles in Icy Moons, Asteroids, and Kuiper Belt Objects (Invited)

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Furfaro, R.

    2013-12-01

    Thermal gradients within conductive layers of icy satellite and asteroids depend partly on heat flow, which is related to the secular decay of radioactive isotopes, to heat released by chemical phase changes, by conversion of gravitational potential energy to heat during differentiation, tidal energy dissipation, and to release of heat stored from prior periods. Thermal gradients are also dependent on the thermal conductivity of materials, which in turn depends on their composition, crystallinity, porosity, crystal fabric anisotropy, and details of their mixture with other materials. Small impurities can produce lattice defects and changes in polymerization, and thereby have a huge influence on thermal conductivity, as can cage-inclusion (clathrate) compounds. Heat flow and thermal gradients can be affected by fluid phase advection of mass and heat (in oceans or sublimating upper crusts), by refraction related to heterogeneities of thermal conductivity due to lateral variations and composition or porosity. Thermal profiles depend also on the surface temperature controlled by albedo and climate, surface relief, and latitude, orbital obliquity and surface insolation, solid state greenhouses, and endogenic heating of the surface. The thermal state of icy moon interiors and thermal gradients can be limited at depth by fluid phase advection of heat (e.g., percolating meteoric methane or gas emission), by the latent heat of phase transitions (melting, solid-state transitions, and sublimation), by solid-state convective or diapiric heat transfer, and by foundering. Rapid burial of thick volatile deposits can also affect thermal gradients. For geologically inactive or simple icy objects, most of these controls on heat flow and thermal gradients are irrelevant, but for many other icy objects they can be important, in some cases causing large lateral and depth variations in thermal gradients, large variations in heat flow, and dynamically evolving thermal states. Many of

  8. Numerical Modeling of Fluid Flow, Heat Transfer and Arc-Melt Interaction in Tungsten Inert Gas Welding

    NASA Astrophysics Data System (ADS)

    Li, Linmin; Li, Baokuan; Liu, Lichao; Motoyama, Yuichi

    2017-04-01

    The present work develops a multi-region dynamic coupling model for fluid flow, heat transfer and arc-melt interaction in tungsten inert gas (TIG) welding using the dynamic mesh technique. The arc-weld pool unified model is developed on basis of magnetohydrodynamic (MHD) equations and the interface is tracked using the dynamic mesh method. The numerical model for arc is firstly validated by comparing the calculated temperature profiles and essential results with the former experimental data. For weld pool convection solution, the drag, Marangoni, buoyancy and electromagnetic forces are separately validated, and then taken into account. Moreover, the model considering interface deformation is adopted in a stationary TIG welding process with SUS304 stainless steel and the effect of interface deformation is investigated. The depression of weld pool center and the lifting of pool periphery are both predicted. The results show that the weld pool shape calculated with considering the interface deformation is more accurate.

  9. Heat transfer and fluid flow in floating-zone crystal growth with a mostly covered melt surface

    NASA Technical Reports Server (NTRS)

    Lan, C. W.; Kou, Sindo

    1992-01-01

    Computer simulation was conducted to study a modified floating-zone crystal growth process, in which the melt surface is mostly covered with a heated ring. The growth of 6-mm diameter single crystals of NaNO3 was considered, and the effects of the following parameters were studied: (1) temperature of the ring, (2) growth rate, (3) surface tension-temperature coefficient of the melt, (4) thermal expansion coefficient of the melt, and (5) gravity. It was demonstrated that thermocapillary convection in the melt zone is reduced significantly in this modified process. The model was checked against the measured lengths of the meniscus near the growth front and axial temperature distribution in a growing crystal, and the agreement was good.

  10. Heat transfer and fluid flow in floating-zone crystal growth with a mostly covered melt surface

    NASA Technical Reports Server (NTRS)

    Lan, C. W.; Kou, Sindo

    1992-01-01

    Computer simulation was conducted to study a modified floating-zone crystal growth process, in which the melt surface is mostly covered with a heated ring. The growth of 6-mm diameter single crystals of NaNO3 was considered, and the effects of the following parameters were studied: (1) temperature of the ring, (2) growth rate, (3) surface tension-temperature coefficient of the melt, (4) thermal expansion coefficient of the melt, and (5) gravity. It was demonstrated that thermocapillary convection in the melt zone is reduced significantly in this modified process. The model was checked against the measured lengths of the meniscus near the growth front and axial temperature distribution in a growing crystal, and the agreement was good.

  11. Bulk heat transfer coefficient in the ice-upper ocean system in the ice melt season derived from concentration-temperature relationship

    NASA Astrophysics Data System (ADS)

    Nihashi, Sohey; Ohshima, Kay I.

    2008-06-01

    The bulk heat transfer coefficient in the ice-upper ocean system (Kb) in the ice melt season is estimated by a new method at 18 areas that cover much of the Antarctic seasonal ice zone. The method is based on a model in which ice melting is caused only by heat input through open water and is treated in a bulk fashion in the ice-upper ocean system. Kb is estimated by fitting a convergent curve derived from the model to an observed ice concentration-temperature plot (CT-plot). Estimated Kb is 1.15 ± 0.72 × 10-4 m s-1 on average. If Kb can be expressed by the product of the heat transfer coefficient (ch) and the friction velocity (uτ), ch is 0.0113 ± 0.0055. This value is about two times larger than that estimated at the ice bottom. The relationship between Kb and the geostrophic wind speed (Uw), which is roughly proportional to uτ, shows a significant positive correlation, as expected. Further, Kb seems more likely to be proportional to the square or cube of Uw rather than a linear relationship. Since Kb estimated from our method is associated with ice melting in a bulk fashion in the ice-upper ocean system, this relationship likely indicates both the mixing process of heat in the upper ocean (proportional to uτ3) and the local heat transfer process at the ice-ocean interface (proportional to uτ).

  12. Influence of gravitational and vibrational convection on the heat- and mass transfer in the melt during crystal growing by Bridgman and floating zone methods

    NASA Astrophysics Data System (ADS)

    Fedorov, Oleg

    2016-07-01

    Space materials science is one of the priorities of different national and international space programs. The physical processes of heat and mass transfer in microgravity (including effect of g-jitter) is far from complete clarity, especially for important practical technology for producing crystals from the melt. The idea of the impact on crystallizing melt by low frequency vibration includes not only the possibility to suppress unwanted microaccelerations, but also to actively influence the structure of the crystallization front. This approach is one of the most effective ways to influence the quality of materials produced in flight conditions. The subject of this work is the effect of vibrations on the thermal and hydrodynamic processes during crystal growth using Bridgman and floating zone techniques, which have the greatest prospect of practical application in space. In the present approach we consider the gravitational convection, Marangoni convection, as well as the effect of vibration on the melt for some special cases. The results of simulation were compared with some experimental data obtained by the authors using a transparent model substance - succinonitrile (Bridgman method), and silicon (floating zone method). Substances used, process parameters and characteristics of the experimental units correspond the equipment developed for onboard research and serve as a basis for selecting optimum conditions vibration exposure as a factor affecting the solidification pattern. The direction of imposing vibrations coincides with the axis of the crystal, the frequency is presented by the harmonic law, and the force of gravity was varied by changing its absolute value. Mathematical model considered axisymmetric approximation of joint convective-conductive energy transfer in the system crystal - melt. Upon application of low-frequency oscillations of small amplitude along the axis of growing it was found the suppression of the secondary vortex flows near the

  13. An Experimental Investigation of Ice Melting and Heat Transfer Characteristics from Submerged Jets of Hot Water, Implications for Subglacial Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Jamshidnia, H.; Gudmundsson, M. T.

    2014-12-01

    The rates and processes of energy transfer in water-filled cavities formed under glaciers by geothermal and volcanic activity has been investigated by designing, developing, and using an experimental setup in which hot water jets can impinge on an ice block. Systematic sets of experimental runs typically lasting 60-90 seconds with water jet temperatures in the range 10° - 90°C have been performed with initial ice block temparature. It is quantitatively found that heat flux from flowing water to ice is linearly dependent on temperature of the jet flow. The hot water jet meltes out a cavity into the ice block during the process. The cavities had steep to vertical sides with a doming roof. Some of the ice blocks used had trapped air bubbles. In these cases melting of the ice lead to the trapping of air at the top of the cavity, partially insulating the roof from the hot water jet. Such cavities had lower aspect ratios (height/width) and flatter and less dome shaped roofs than did cavities in ice blocks with little or no air bubbles. The overall heat transfer rate in cavity formation varied with jet temperature from <100 kW m-2 to ~900 kW m-2 while melting rates in the vertical direction yield heat transfer rates of 200-1200 kW m-2. The observed experimental heat transfer rates can be compared to data on subglacial melting observed for ice cauldrons in various settings in Iceland. For the lowest experimental temperatures the numbers are comparable to those found for geothermal water in cool, subglacial water bodies and above subglacial flowpaths of jökulhlaups. However, the highest experimental rates for 80-90°C jets are 3-10 times less than inferred from observations of recent subglacial eruptions (2000-4000 kW m-2). This can indicate that single phase liquid water convection alone is not sufficient to explain the rates seen in recent subglacial eruptions in Iceland, suggesting that during such eruptions forced two-phase (liquid and steam) or three phase (liquid

  14. SCALE ANALYSIS OF CONVECTIVE MELTING WITH INTERNAL HEAT GENERATION

    SciTech Connect

    John Crepeau

    2011-03-01

    Using a scale analysis approach, we model phase change (melting) for pure materials which generate internal heat for small Stefan numbers (approximately one). The analysis considers conduction in the solid phase and natural convection, driven by internal heat generation, in the liquid regime. The model is applied for a constant surface temperature boundary condition where the melting temperature is greater than the surface temperature in a cylindrical geometry. We show the time scales in which conduction and convection heat transfer dominate.

  15. Thermal radiation and chemical reaction effects on boundary layer slip flow and melting heat transfer of nanofluid induced by a nonlinear stretching sheet

    NASA Astrophysics Data System (ADS)

    Krishnamurthy, M. R.; Gireesha, B. J.; Prasannakumara, B. C.; Gorla, Rama Subba Reddy

    2016-09-01

    A theoretically investigation has been performed to study the effects of thermal radiation and chemical reaction on MHD velocity slip boundary layer flow and melting heat transfer of nanofluid induced by a nonlinear stretching sheet. The Brownian motion and thermophoresis effects are incorporated in the present nanofluid model. A set of proper similarity variables is used to reduce the governing equations into a system of nonlinear ordinary differential equations. An efficient numerical method like Runge-Kutta-Fehlberg-45 order is used to solve the resultant equations for velocity, temperature and volume fraction of the nanoparticle. The effects of different flow parameters on flow fields are elucidated through graphs and tables. The present results have been compared with existing one for some limiting case and found excellent validation.

  16. Heat transfer system

    DOEpatents

    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.

  17. Heat transfer system

    DOEpatents

    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.

  18. Enhancement of heat transfer

    NASA Astrophysics Data System (ADS)

    Nakayama, W.

    Recent publications on enhancement of heat transfer are reviewed, emphasizing the effects of roughness elements, fins, and porous surfaces. Enhancement of forced convective heat transfer on roughened surfaces, performance evaluation of enhanced surfaces, viscous flows in cooled tubes and tubes with swirlers, and active methods of enhancement are addressed. Aspects of pool boiling heat transfer are considered, including nucleate boiling heat transfer on rough surfaces and porous surfaces, and maximum and minimum heat fluxes. Evaporative heat transfer is discussed for thin-film evaporation on structured surfaces and liquid spray cooling of a heated surface. Condensation heat transfer on external surfaces is covered, including filmwise condensation on vertical finned and fluted surfaces and on horizontal tubes. In-tube boiling and condensation are treated, discussing their enhancement by fins and inserts, as well as critical heat flux in coiled, rifled, and corrugated tubes.

  19. Introductory heat-transfer

    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.

  20. Physics-Based Modeling of Electric Operation, Heat Transfer, and Scrap Melting in an AC Electric Arc Furnace

    NASA Astrophysics Data System (ADS)

    Opitz, Florian; Treffinger, Peter

    2016-04-01

    Electric arc furnaces (EAF) are complex industrial plants whose actual behavior depends upon numerous factors. Due to its energy intensive operation, the EAF process has always been subject to optimization efforts. For these reasons, several models have been proposed in literature to analyze and predict different modes of operation. Most of these models focused on the processes inside the vessel itself. The present paper introduces a dynamic, physics-based model of a complete EAF plant which consists of the four subsystems vessel, electric system, electrode regulation, and off-gas system. Furthermore the solid phase is not treated to be homogenous but a simple spatial discretization is employed. Hence it is possible to simulate the energy input by electric arcs and fossil fuel burners depending on the state of the melting progress. The model is implemented in object-oriented, equation-based language Modelica. The simulation results are compared to literature data.

  1. Heat transfer in microwave heating

    NASA Astrophysics Data System (ADS)

    Peng, Zhiwei

    Heat transfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heat transfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heat transfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, wüstite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heat transfer process in microwave heating of magnetite

  2. Heat transfer equipment design

    NASA Astrophysics Data System (ADS)

    Shah, R. K.; Subbarao, Eleswarapu Chinna; Mashelkar, R. A.

    A comprehensive presentation is made of state-of-the-art configurations and design methodologies for heat transfer devices applicable to industrial processes, automotive systems, air conditioning/refrigeration, cryogenics, and petrochemicals refining. Attention is given to topics in heat exchanger mechanical design, single-phase convection processes, thermal design, two-phase exchanger thermal design, heat-transfer augmentation, and rheological effects. Computerized analysis and design methodologies are presented for the range of heat transfer systems, as well as advanced methods for optimization and performance projection.

  3. Heat transfer in pipes

    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.

  4. Melt Segregation and Tidal Heating at Io

    NASA Astrophysics Data System (ADS)

    Rajendar, A.; Dufek, J.; Roberts, J. H.; Paty, C. S.

    2011-12-01

    Recent evidence of melt beneath Io's surface (Khurana et al., 2010) and repeated observation of volcanic activity and features consistent with volcanic activity at the surface (e.g. Veeder et al, 1994; Rathbun et al., 2004; Lopes-Gautier et al., 1999; Smith et al., 1979) has raised further questions about the structure of the Galilean moon and the processes that shape it. In this study we examine the thermal state, melt fraction, and multiphase dynamics of melt segregation within Io's interior. Using a coupled multiphase dynamics and tidal heating model we explore the location, spatial extent, and temporal residence times of melt in Io's subsurface, as well as response to orbital parameters. In a thermally evolving body subject to tidal forcing, in which melt production and migration takes place, feedback can occur with respect to the physical and thermal properties. We explore this feedback to produce a thermal model of Io, taking into account the rate of tidal heating and fluid motion within the interior. First, a layered model of the internal structure is assumed. The equations of motion for forced oscillations in a layered spherical body are then solved using the propagator matrix method (Sabadini and Vermeesen, 2004) to obtain the displacements and strains due to tidal motion (Roberts and Nimmo, 2008). From this, the radial distribution of tidal heat generation within Io is calculated. This radial heating profile is then used as input for a multi-phase fluid model in order to obtain an estimate of the radial temperature distribution and thus the material properties and melt fractions. In the multiphase model individual phases (melt and solid residue) separately conserve mass, momentum and enthalpy (Dufek and Bachmann, 2010) allowing us to explore melt segregation phenomena. Enthalpy closure is provided by the MELTS (Ghiorso and Sack, 1995) thermodynamics algorithm, which is called at each point in space. This accounts for the partitioning between latent and

  5. An Experimental Investigation of Ice-melting and heat transfer rates from submerged warm water jets upward impinging into ice-blocks as analogous for water-filled cavities formed during subglacial eruptions.

    NASA Astrophysics Data System (ADS)

    Jamshidnia, Hamidreza; Gudmundsson, Magnus Tumi

    2016-11-01

    Rates of energy transfer in water-filled cavities formed under glaciers by geothermal and volcanic activity are investigated by conducting experiments in which hot water jets (10°- 90°C) impinging into an ice block for jet Reynolds numbers in turbulent regime of 10000 -70000. It is found that heat flux is linearly dependent on jet flow temperature. Water jet melts a cavity into an ice block. Cavities had steep to vertical sides with a doming roof. Some of ice blocks used had trapped air bubbles. In these cases that melting of the ice could have led to trapping of air at the top of cavity, partially insulating the roof from hot water jet. The overall heat transfer rate in cavity formation varied with jet temperature from <100 kW m-2 to 900 kW m-2 while melting rates in the vertical direction yield heat transfer rates of 200-1200 kW m-2. Experimental heat transfer rates can be compared to data on subglacial melting observed for ice cauldrons in Iceland. For lowest temperatures the numbers are comparable to those for geothermal water in cool, subglacial water bodies and above subglacial flowpaths of jökulhlaups. Highest experimental rates for 80-90°C jets are 3-10 times less than inferred from observations of recent subglacial eruptions (2000-4000 kW m-2) . This can indicate that single phase liquid water convection alone may not be sufficient to explain the rates seen in recent subglacial eruptions, suggesting that forced 2 or 3 phase convection can be common.

  6. Digitized Heat Transfer

    NASA Astrophysics Data System (ADS)

    Mohseni, Kamran; Young, Patrick

    2007-11-01

    This presentation presents theoretical and numerical results describing digitized heat transfer (DHT), an active thermal management technique for high-power electronics and integrated micro systems. In digitized heat transfer discrete droplets are employed. The internal flow inside a discrete droplet is dominated by internal circulation imposed by the boundaries. This internal circulation imposes a new timescale for recirculating cold liquid from the middle of the droplet to the boundary. This internal circulation produces periodic oscillation in the overall convective heat transfer rate. Numerical simulations are presented for heat transfer in the droplet for both constant temperature and flux boundary conditions. The effectiveness of DHT for managing both localized temperature spikes and steady state cooling is demonstrated, identifying key parameters for optimization of the DHT method.

  7. Turbine heat transfer

    NASA Technical Reports Server (NTRS)

    Rohde, J. E.

    1982-01-01

    Objectives and approaches to research in turbine heat transfer are discussed. Generally, improvements in the method of determining the hot gas flow through the turbine passage is one area of concern, as is the cooling air flow inside the airfoil, and the methods of predicting the heat transfer rates on the hot gas side and on the coolant side of the airfoil. More specific areas of research are: (1) local hot gas recovery temperatures along the airfoil surfaces; (2) local airfoil wall temperature; (3) local hot gas side heat transfer coefficients on the airfoil surfaces; (4) local coolant side heat transfer coefficients inside the airfoils; (5) local hot gas flow velocities and secondary flows at real engine conditions; and (6) local delta strain range of the airfoil walls.

  8. Heat transfer fluids containing nanoparticles

    DOEpatents

    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.

  9. Heat transfer studies

    SciTech Connect

    Boehm, R.; Chen, Y.T.; Sathappan, A.K.

    1995-10-20

    Work continued from last quarter related to studies of heat transfer and fluid flow in porous media. One experiment focused on issues of drying in subresidually-saturated systems. The other experiment deals with studies of flows in a repository-like geometry around a heated horizontal annulus. In the subresidual saturation studies, elevated temperature environments were considered during this quarter. A 1 in. {times} 8 ft long heating tape (heating capabilities of 8.6 W/in{sup 2}) with an on-off type temperature controller has been used to maintain a constant temperature on the aluminum test section (the latter has been described in earlier reports). Nitrogen gas with a flow rate of 1 SLPM was flowed through a glass-bead medium with an isothermal (90{degrees}C) boundary condition. The drying characteristics of this system are reported. In a second experiment, that of flow and heat transfer around a simulated drift, a low, constant heat flux boundary condition on the heater has been used. Two different admitted water quantities, 200 ml and 300 ml, have been used as before. The response of temperatures and relative humidity in the porous medium and annulus are very similar to the results of the high constant heat flux on the case of 300 ml water experiments. This is not the case for the 200 ml water experiment. The low constant heat flux with a small quantity of water is found to have no significant effect on the temperature responses.

  10. Ultrafast radiative heat transfer.

    PubMed

    Yu, Renwen; Manjavacas, Alejandro; García de Abajo, F Javier

    2017-02-23

    Light absorption in conducting materials produces heating of their conduction electrons, followed by relaxation into phonons within picoseconds, and subsequent diffusion into the surrounding media over longer timescales. This conventional picture of optical heating is supplemented by radiative cooling, which typically takes place at an even lower pace, only becoming relevant for structures held in vacuum or under extreme thermal isolation. Here, we reveal an ultrafast radiative cooling regime between neighboring plasmon-supporting graphene nanostructures in which noncontact heat transfer becomes a dominant channel. We predict that more than 50% of the electronic heat energy deposited on a graphene disk can be transferred to a neighboring nanoisland within a femtosecond timescale. This phenomenon is facilitated by the combination of low electronic heat capacity and large plasmonic field concentration in doped graphene. Similar effects should occur in other van der Waals materials, thus opening an unexplored avenue toward efficient heat management.Electron relaxation, which is the dominant release channel of electronic heat in nanostructures, occurs with characteristic times of several picoseconds. Here, the authors predict that an ultrafast (femtosecond) radiative cooling regime takes place in plasmonically active neighboring graphene nanodisks prior to electron relaxation.

  11. 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.

  12. Solar Energy: Heat Transfer.

    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…

  13. Metal loss and charge heating in the melt in an electric arc furnace

    NASA Astrophysics Data System (ADS)

    Serikov, V. A.; Bikeev, R. A.; Cherednichenko, M. V.; Cherednichenko, V. S.

    2015-12-01

    The heat exchange between a metallic melt and a slag with a charge is simulated with allowance for possible formation of a skull on the charge surface. It is shown that the charge melting rate in the melt is determined by the coefficient of heat transfer between the metal and the charge and the ratio of the mass of a charge fragment to its surface area interacting with the melt. A skull is found to form on the charge surface at a low coefficient of heat transfer between the metal and the charge. The main heat parameters, the control of which by an automatic control system ensures an increase in the charge melting rate in the melt and a decrease in the metal loss, are formulated.

  14. 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.

  15. 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.

  16. HEAT TRANSFER METHOD

    DOEpatents

    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.

  17. Gas Blowing: Mass Transfer in Gas and Melt

    NASA Astrophysics Data System (ADS)

    Sortland, Øyvind Sunde; Tangstad, Merete

    2014-09-01

    Metallurgical routes for solar grade silicon production are being developed as alternatives to chemical processes for their potential to achieve cost reductions, increased production volume, and reduced environmental and safety concerns. An important challenge in the development of metallurgical routes relates to the higher impurity concentrations in the silicon product, particularly for boron and other elements that are not efficiently segregated in solidification techniques. The reactive gas refining process is studied for its potential to remove boron below the solar grade silicon target concentration in a single step by blowing steam and hydrogen gas jets onto the melt surface. Boron in a silicon melt is extracted to HBO gas in parallel to active oxidation of silicon. The literature is not unified regarding the rate determining step in this process. Relevant theories and equations for gas blowing in induction furnaces are combined and used to explain mass transfer in experiments. Mass transfer in the melt and gas is investigated by comparing resistance and induction heating of the melt, and varying gas flow rate, crucible diameter, diameter of the gas lance, and the position of the gas lance above the melt surface. The rate of boron removal is found to increase with increasing gas flow rate and crucible diameter. A relatively high fraction of the reactive gas is utilized in the process, and supply of steam in the bulk gas is the only identified rate determining step.

  18. Geothermal Heat Transfer

    SciTech Connect

    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.

  19. Subglacial lava propagation, ice melting and heat transfer during emplacement of an intermediate lava flow in the 2010 Eyjafjallajökull eruption

    NASA Astrophysics Data System (ADS)

    Oddsson, Björn; Gudmundsson, Magnús T.; Edwards, Benjamin R.; Thordarson, Thorvaldur; Magnússon, Eyjólfur; Sigurðsson, Gunnar

    2016-07-01

    During the 2010 Eyjafjallajökull eruption in South Iceland, a 3.2-km-long benmoreite lava flow was emplaced subglacially during a 17-day effusive-explosive phase from April 18 to May 4. The lava flowed to the north out of the ice-filled summit caldera down the outlet glacier Gígjökull. The flow has a vertical drop of about 700 m, an area of ca. 0.55 km2, the total lava volume is ca. 2.5·107 m3 and it is estimated to have melted 10-13·107 m3 of ice. During the first 8 days, the lava advanced slowly (<100 m day-1), building up to a thickness of 80-100 m under ice that was initially 150-200 m thick. Faster advance (up to 500 m day-1) formed a thinner (10-20 m) lava flow on the slopes outside the caldera where the ice was 60-100 m thick. This subglacial lava flow was emplaced along meltwater tunnels under ice for the entire 3.2 km of the flow field length and constitutes 90 % of the total lava volume. The remaining 10 % belong to subaerial lava that was emplaced on top of the subglacial lava flow in an ice-free environment at the end of effusive activity, forming a 2.7 km long a'a lava field. About 45 % of the thermal energy of the subglacial lava was used for ice melting; 4 % was lost with hot water; about 1 % was released to the atmosphere as steam. Heat was mostly released by forced convection of fast-flowing meltwater with heat fluxes of 125-310 kWm-2.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Heat transfer probe

    DOEpatents

    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.

  5. Heat transfer device

    NASA Technical Reports Server (NTRS)

    Kalkbrenner, R. W. (Inventor)

    1974-01-01

    A heat transfer device is characterized by an hermetically sealed tubular housing including a tubular shell terminating in spaced end plates, and a tubular mesh wick concentrically arranged and operatively supported within said housing. The invention provides an improved wicking restraint formed as an elongated and radially expanded tubular helix concentrically related to the wick and adapted to be axially foreshortened and radially expanded into engagement with the wick in response to an axially applied compressive load. The wick is continuously supported in a contiguous relationship with the internal surfaces of the shell.

  6. Conduction heat transfer solutions

    SciTech Connect

    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.

  7. Conduction heat transfer solutions

    SciTech Connect

    VanSant, James 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.

  8. Heat transfer and fire spread

    Treesearch

    Hal E. Anderson

    1969-01-01

    Experimental testing of a mathematical model showed that radiant heat transfer accounted for no more than 40% of total heat flux required to maintain rate of spread. A reasonable prediction of spread was possible by assuming a horizontal convective heat transfer coefficient when certain fuel and flame characteristics were known. Fuel particle size had a linear relation...

  9. Tubing for augmented heat transfer

    SciTech Connect

    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)

  10. How to detect melting in laser heating diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Liuxiang, Yang

    2016-07-01

    Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now, large discrepancies still exist in the melting curve of iron, the most interesting and extensively studied element in geoscience research. Here we present a summary about techniques detecting melting in the laser heating diamond anvil cell.

  11. Directional melting of alumina via polarized microwave heating

    NASA Astrophysics Data System (ADS)

    Hu, Yuan; Nakano, Aiichiro; Wang, Joseph

    2017-01-01

    Dynamical instabilities and melting of crystals upon heating are fundamental problems in physics and materials science. Using molecular dynamics simulations, we found that drastically different melting temperatures and behaviors can be achieved in α-alumina using microwave heating, where the electric field is aligned with different crystallographic orientations. Namely, alumina melts much earlier at lower temperatures when the electric field is parallel to the c-axis. The atomistic mechanism was identified as selective liberation of the Al sublattice due to the shear instability along the c-axis. This directional melting concept may be used for triggering distinct dynamical instabilities and melting of dielectric crystals using polarized microwave fields.

  12. Scale/Analytical Analyses of Freezing and Convective Melting with Internal Heat Generation

    SciTech Connect

    Ali S. Siahpush; John Crepeau; Piyush Sabharwall

    2013-07-01

    Using a scale/analytical analysis approach, we model phase change (melting) for pure materials which generate constant internal heat generation for small Stefan numbers (approximately one). The analysis considers conduction in the solid phase and natural convection, driven by internal heat generation, in the liquid regime. The model is applied for a constant surface temperature boundary condition where the melting temperature is greater than the surface temperature in a cylindrical geometry. The analysis also consider constant heat flux (in a cylindrical geometry).We show the time scales in which conduction and convection heat transfer dominate.

  13. Heat Transfer in Complex Fluids

    SciTech Connect

    Mehrdad Massoudi

    2012-01-01

    Amongst the most important constitutive relations in Mechanics, when characterizing the behavior of complex materials, one can identify the stress tensor T, the heat flux vector q (related to heat conduction) and the radiant heating (related to the radiation term in the energy equation). Of course, the expression 'complex materials' is not new. In fact, at least since the publication of the paper by Rivlin & Ericksen (1955), who discussed fluids of complexity (Truesdell & Noll, 1992), to the recently published books (Deshpande et al., 2010), the term complex fluids refers in general to fluid-like materials whose response, namely the stress tensor, is 'non-linear' in some fashion. This non-linearity can manifest itself in variety of forms such as memory effects, yield stress, creep or relaxation, normal-stress differences, etc. The emphasis in this chapter, while focusing on the constitutive modeling of complex fluids, is on granular materials (such as coal) and non-linear fluids (such as coal-slurries). One of the main areas of interest in energy related processes, such as power plants, atomization, alternative fuels, etc., is the use of slurries, specifically coal-water or coal-oil slurries, as the primary fuel. Some studies indicate that the viscosity of coal-water mixtures depends not only on the volume fraction of solids, and the mean size and the size distribution of the coal, but also on the shear rate, since the slurry behaves as shear-rate dependent fluid. There are also studies which indicate that preheating the fuel results in better performance, and as a result of such heating, the viscosity changes. Constitutive modeling of these non-linear fluids, commonly referred to as non-Newtonian fluids, has received much attention. Most of the naturally occurring and synthetic fluids are non-linear fluids, for example, polymer melts, suspensions, blood, coal-water slurries, drilling fluids, mud, etc. It should be noted that sometimes these fluids show Newtonian

  14. Heat transfer and thermal control

    NASA Astrophysics Data System (ADS)

    Crosbie, A. L.

    Radiation heat transfer is considered along with conduction heat transfer, heat pipes, and thermal control. Attention is given to the radiative properties of a painted layer containing nonspherical pigment, bidirectional reflectance measurements of specular and diffuse surfaces with a simple spectrometer, the radiative equilibrium in a general plane-parallel environment, and the application of finite-element techniques to the interaction of conduction and radiation in participating medium, a finite-element approach to combined conductive and radiative heat transfer in a planar medium. Heat transfer in irradiated shallow layers of water, an analytical and experimental investigation of temperature distribution in laser heated gases, numerical methods for the analysis of laser annealing of doped semiconductor wafers, and approximate solutions of transient heat conduction in a finite slab are also examined. Consideration is also given to performance testing of a hydrogen heat pipe, heat pipe performance with gravity assist and liquid overfill, vapor chambers for an atmospheric cloud physics laboratory, a prototype heat pipe radiator for the German Direct Broadcasting TV Satellite, free convection in enclosures exposed to compressive heating, and a thermal analysis of a multipurpose furnace for material processing in space.

  15. HEAT TRANSFER MEANS

    DOEpatents

    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.

  16. Heat transfer through a paraffin wax solar energy storage characterized by a temperature dependent specific heat

    SciTech Connect

    Gobin, D.; Benard, C.; Levesque, D.; Gogy, J.C.

    1981-01-01

    The numerical solution of heat transfer equations in the melting process of a phase change material (PCM) has been studied. This problem generally concerns pure materials presenting a frank solid-liquid transition at a precise melting temperature. This problem allows the simulated comparison of various types of PCMs and testing the behavior of a given system for variations of different parameters. 3 refs.

  17. Advances in enhanced heat transfer: 1987

    SciTech Connect

    Jensen, M.K.; Carey, V.P.

    1987-01-01

    This book contains nine selections. Some of the titles are: High Heat-Flux, Forced-Convection Heat Transfer for Tubes with Twisted-Tape Inserts; Heat Transfer Augmentation by Interrupted Surfaces - Experimental Consideration; Turbulent Flow Heat Transfer from Externally Roughened Tubes in Axial Flow in Concentric Pipe Heat Exchangers; and Heat Transfer Enhancement of Turbulent Flow in Pipes with an Internal Circular Rib.

  18. Turbulent convection driven by internal radiative heating of melt ponds on sea ice

    NASA Astrophysics Data System (ADS)

    Wells, Andrew; Langton, Tom; Rees Jones, David; Moon, Woosok

    2016-11-01

    The melting of Arctic sea ice is strongly influenced by heat transfer through melt ponds which form on the ice surface. Melt ponds are internally heated by the absorption of incoming radiation and cooled by surface heat fluxes, resulting in vigorous buoyancy-driven convection in the pond interior. Motivated by this setting, we conduct two-dimensional direct-numerical simulations of the turbulent convective flow of a Boussinesq fluid between two horizontal boundaries, with internal heating predicted from a two-stream radiation model. A linearised thermal boundary condition describes heat exchange with the overlying atmosphere, whilst the lower boundary is isothermal. Vertically asymmetric convective flow modifies the upper surface temperature, and hence controls the partitioning of the incoming heat flux between emission at the upper and lower boundaries. We determine how the downward heat flux into the ice varies with a Rayleigh number based on the internal heating rate, the flux ratio of background surface cooling compared to internal heating, and a Biot number characterising the sensitivity of surface fluxes to surface temperature. Thus we elucidate the physical controls on heat transfer through Arctic melt ponds which determine the fate of sea ice in the summer.

  19. Development of Magnetic Field Assisted Melt Stabilization with Heat and Mass Transfer Control in Low Pressure LEC Growth of GaAs

    DTIC Science & Technology

    1988-10-01

    of GaAs Crystals in LEC Growth Configuration: Optimum Thermal Characteristics of the Growth Environment", Ferrofluidics Corp., Nashua, NH, January...accomplish the task of controlling the temperature distribution in the melt. Thermocouples or single color pyrometers are generally used as sensors for this...D subsystem where a second LUT is used to false color the outgoing monochrome signal. The LUT is defined to map low intensities to blue and high

  20. Sphere Drag and Heat Transfer.

    PubMed

    Duan, Zhipeng; He, Boshu; Duan, Yuanyuan

    2015-07-20

    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.

  1. Sphere Drag and Heat Transfer

    PubMed Central

    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

  2. Heat-transfer thermal switch

    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.

  3. 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.

  4. Tidal Heating and Melt Segregation and Migration within Io

    NASA Astrophysics Data System (ADS)

    Rajendar, A.; Paty, C. S.; Dufek, J.; Roberts, J. H.

    2014-12-01

    Io's volcanic activity is driven by the dissipation of energy in its interior due to tidal forces exerted by Jupiter, maintained by its orbital resonances with Europa and Ganymede. The 2011 discovery of a global partial melt layer beneath Io's surface has raised further questions about the structure of the Galilean moon and the processes that shape it. In this study we use two coupled simulations, the MFIX multiphase dynamics and the TiRADE tidal heating models, to investigate the location and extent, thermal state, melt fraction, stability, and migration of melt Io's viscous asthenosphere. We explore the feedback between melt migration and production, taking into account the rate of tidal heating and melt migration through the magma ocean layer. We begin with an assumed 1D layered internal structure based on previous investigations. This structure is input into TiRADE, which solves the equations of motion for forced oscillations in a layered spherical body using the propagator matrix method to obtain the displacements and strains due to tidal forcing. From this, we obtain the radial distribution of tidal heat generation within Io. This heating profile is then used as input for the MFIX multiphase fluid model in order to obtain the vertical flow of partially molten material, as well as the radial temperature distribution and thus the material properties and melt fractions. In the multiphase model, individual phases (melt and solid residue) separately conserve mass, momentum and enthalpy allowing us to explore melt segregation phenomena. Enthalpy closure is provided by the MELTS thermodynamics algorithm, which is called at each point in space, accounting for the partitioning between latent and sensible heat, and updating the physical properties of the melt and solid phases. This approach allows us to explore the sensitivity of melt generation to internal structure, as well as the time scales that govern melt production and eruption (i.e.: the residence and migration

  5. Heat Transfer Parametric System Identification

    DTIC Science & Technology

    1993-06-01

    Transfer Parametric System Identification 6. AUTHOR(S Parker, Gregory K. 7. PERFORMING ORGANIZATION NAME(S) AND AOORESS(ES) 8. PERFORMING ORGANIZATION...distribution is unlimited. Heat Transfer Parametric System Identification by Gregory K. Parker Lieutenant, United States Navy BS., DeVry Institute of...Modeling Concept ........ ........... 3 2. Lumped Parameter Approach ...... ......... 4 3. Parametric System Identification ....... 4 B. BASIC MODELING

  6. Heat transfer in damaged material

    NASA Astrophysics Data System (ADS)

    Kruis, J.

    2013-10-01

    Fully coupled thermo-mechanical analysis of civil engineering problems is studied. The mechanical analysis is based on damage mechanics which is useful for modeling of behaviour of quasi-brittle materials, especially in tension. The damage is assumed to be isotropic. The heat transfer is assumed in the form of heat conduction governed by the Fourier law and heat radiation governed by the Stefan-Boltzmann law. Fully coupled thermo-mechanical problem is formulated.

  7. Enhanced heat transfer using nanofluids

    DOEpatents

    Choi, Stephen U. S.; Eastman, Jeffrey A.

    2001-01-01

    This invention is directed to a method of and apparatus for enhancing heat transfer in fluids such as deionized water. ethylene glycol, or oil by dispersing nanocrystalline particles of substances such as copper, copper oxide, aluminum oxide, or the like in the fluids. Nanocrystalline particles are produced and dispersed in the fluid by heating the substance to be dispersed in a vacuum while passing a thin film of the fluid near the heated substance. The fluid is cooled to control its vapor pressure.

  8. 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.

  9. Endothermic freezing on heating and exothermic melting on cooling.

    PubMed

    Tombari, E; Ferrari, C; Salvetti, G; Johari, G P

    2005-08-01

    Generally, a liquid freezes exothermally on cooling and a crystal melts endothermally on heating. Here we report an opposite occurrence--a liquid's endothermic freezing on heating and the resulting crystal's exothermic melting on cooling at ambient pressures. C(p) decreases on freezing and increases on melting, and the equilibrium temperature meets the thermodynamic requirement. Melting on cooling takes longer than freezing on heating. A rapidly cooled crystal state becomes kinetically frozen, evocative of a nonergodic state. Both C(p) and enthalpy relax like those of glasses, though the viscosity is only a few centipoise. The crystal state belongs to energy minima higher than those of the melt, which has consequences for the use of potential-energy landscape, or inherent structures, for a thermodynamic description of a material.

  10. Nanofluid impingement jet heat transfer

    PubMed Central

    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

  11. Measurement of thermoacoustic convection heat transfer phenomenon

    NASA Technical Reports Server (NTRS)

    Parang, M.; Salah-Eddine, A.

    1983-01-01

    In this paper the results of an experimental investigation of thermoacoustic convection (TAC) heat transfer phenomenon in both zero-gravity and gravity environment are presented and compared with pure conduction heat transfer. The numerical solutions of the governing equations obtained by others for TAC heat transfer phenomenon are also discussed. The experimental results show that for rapid heating rate at a boundary, the contribution of TAC heat transfer to a gas could be significantly (one order of magnitude) higher than heat transfer rate from pure conduction. The results also show significantly reduced transient time in heat transfer processes involving thermoacoustic convective heat transfer mode in both space and gravity environment.

  12. Effect of Ultrasonic Vibrations on Accelerating Heat Transfer of Pcm

    NASA Astrophysics Data System (ADS)

    Yang, Ho Dong; Oh, Yool Kwon

    This study presents the effect on accelerating heat transfer of phase change material (PCM) when the ultrasonic vibrations were applied. Applying ultrasonic waves in a medium may cause the flow velocity of the medium to increase: an effect known as acoustic streaming. Hence, the objective of the present study was to investigate the melting process of a PCM from a heated vertical wall for the following: one without ultrasonic vibration (natural melting) and the other ultrasonic vibrations. The heat flow was measured in the absence of and in the presence of acoustic streaming. The streaming created by ultrasonic vibrations was visualized by a particle image velocimetry (PIV) and a thermal infrared camera. The experimental results revealed that acoustic streaming could accelerate the melting process as much as 2.5 times. Also, total consumed electricity was saved about 2.3 ~ 2.8 Wh, compared to the rate of natural melting. Moreover, we investigate the relationship between acoustic pressure variations and enhancement of heat transfer applying for coupled finite element-boundary element method (Coupled FE-BEM) as a numerical analysis. From the result study, as the acoustic pressure increases, the higher enhancement ratio of heat transfer is obtained. In the end, acoustic pressure variations are related to the acceleration of heat transfer by ultrasonic vibrations.

  13. Numerical and experimental investigation of melting with internal heat generation within cylindrical enclosures

    SciTech Connect

    Amber Shrivastava; Brian Williams; Ali S. Siahpush; Bruce Savage; John Crepeau

    2014-06-01

    There have been significant efforts by the heat transfer community to investigate the melting phenomenon of materials. These efforts have included the analytical development of equations to represent melting, numerical development of computer codes to assist in modeling the phenomena, and collection of experimental data. The understanding of the melting phenomenon has application in several areas of interest, for example, the melting of a Phase Change Material (PCM) used as a thermal storage medium as well as the melting of the fuel bundle in a nuclear power plant during an accident scenario. The objective of this research is two-fold. First a numerical investigation, using computational fluid dynamics (CFD), of melting with internal heat generation for a vertical cylindrical geometry is presented. Second, to the best of authors knowledge, there are very limited number of engineering experimental results available for the case of melting with Internal Heat Generation (IHG). An experiment was performed to produce such data using resistive, or Joule, heating as the IHG mechanism. The numerical results are compared against the experimental results and showed favorable correlation. Uncertainties in the numerical and experimental analysis are discussed. Based on the numerical and experimental analysis, recommendations are made for future work.

  14. Investigation of Heat Transfer From

    NASA Technical Reports Server (NTRS)

    Lewis, James P.; Ruggeri, Robert S.

    1956-01-01

    The convective heat transfer from the surface of an ellipsoidal forebody of fineness ratio 3 and 20-inch maximum diameter was investigated in clear air for both stationary and rotating operation over a range of conditions including air speeds up to 240 knots, rotational speeds up to 1200 rpm, and angles of attack of 0 deg, 3 deg, and 6 deg. The results are presented in the form of heat-transfer coefficients and the correlation of Nusselt and Reynolds numbers. Both a uniform surface temperature and a uniform input heater density distribution were used. The experimental results agree well with theoretical predictions for uniform surface temperature distribution. Complete agreement was not obtained with uniform input heat density in the laminar-flow region because of conduction effects. No significant effects of rotation were obtained over the range of airstream and rotational speeds investigated. Operation at angle of attack had only minor effects on the local heat transfer. Transition from laminar to turbulent heat transfer occurred over a wide range of Reynolds numbers. The location of transition depended primarily on surface roughness and pressure and temperature gradients. Limited transient heating data indicate that the variation of surface temperature with time followed closely an exponential relation.

  15. Internal stress-induced melting below melting temperature at high-rate laser heating

    SciTech Connect

    Hwang, Yong Seok; Levitas, Valery I.

    2014-06-30

    In this Letter, continuum thermodynamic and phase field approaches (PFAs) predicted internal stress-induced reduction in melting temperature for laser-irradiated heating of a nanolayer. Internal stresses appear due to thermal strain under constrained conditions and completely relax during melting, producing an additional thermodynamic driving force for melting. Thermodynamic melting temperature for Al reduces from 933.67 K for a stress-free condition down to 898.1 K for uniaxial strain and to 920.8 K for plane strain. Our PFA simulations demonstrated barrierless surface-induced melt nucleation below these temperatures and propagation of two solid-melt interfaces toward each other at the temperatures very close to the corresponding predicted thermodynamic equilibrium temperatures for the heating rate Q≤1.51×10{sup 10}K/s. At higher heating rates, kinetic superheating competes with a reduction in melting temperature and melting under uniaxial strain occurs at 902.1 K for Q = 1.51 × 10{sup 11 }K/s and 936.9 K for Q = 1.46 × 10{sup 12 }K/s.

  16. 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

  17. Direct contact heat transfer for thermal energy storage

    NASA Astrophysics Data System (ADS)

    Wright, J. D.

    1982-03-01

    Direct contact heat exchange offers the potential for increased efficiency and lower heat transfer costs in a variety of thermal energy storage systems. SERI models of direct contact heat transfer based on literature information identified dispersed phase drop size, the mechanism of heat transfer within the drop, and dispersed phase holdup as the parameters controlling direct contact system performance. Tests were defined and equipment constructed to provide independent determination of drop size, heat transfer mechanism, and hold up. Further experiments are needed to conclusively determine whether the salt in a salt hydrate melt acts to block internal circulation. The potential of low temperature oil/salt hydrate latent heat storage systems is being evaluated in the laboratory.

  18. Direct contact heat transfer for thermal energy storage

    NASA Astrophysics Data System (ADS)

    Wright, J. D.

    1980-11-01

    Direct contact heat exchange offers the potential for increased efficiency and lower heat transfer costs in a variety of thermal energy storage systems. Models of direct contact heat transfer based on literature information identified dispersed phase drop size, the mechanism of heat transfer within the drop, and dispersed phase holdup as the parameters controlling direct contact system performance. Tests were defined and equipment constructed to provide independent determination of drop size, heat transfer mechanism, and hold up. Experiments with heptane dispersed in water are described. The velocity at which drop formation changes from dropwise to jetting was overpredicted by all literature correlations. Further experiments are needed to conclusively determine whether the salt in a salt hydrate melt acts to block internal circulation. In addition, the potential of low temperature oil/salt hydrate latent heat storage systems is evaluated in the laboratory.

  19. Optimization of Temperatures Heating Melt and Annealing Soft Magnetic Alloys

    NASA Astrophysics Data System (ADS)

    Tsepelev, Vladimir; Starodubtsev, Yuri

    2017-05-01

    Taking into account the concept of the quasi-chemical model of the liquid micro-non-uniform composition and the research made on the physical properties of the Fe-based melts being crystallized, the unique technology of the melt time-temperature treatment has been developed. Amorphous ribbons produced using this technology require optimal annealing temperatures to be specifically selected. Temperature dependences of the kinematic viscosity of a multicomponent Fe72.5Cu1Nb2Mo1.5Si14B9 melt have been studied. A critical temperature is detected above which the activation energy of viscous flow of the melt changes. Upon cooling the overheated melt, the temperature curves of the kinematic viscosity become linear within the given coordinates. In amorphous ribbon produced in the mode with overheating the melt above the critical temperature, the enthalpy of crystallization grows, the following heat treatment results in an increase in magnetic permeability.

  20. Radiative heat transfer

    NASA Astrophysics Data System (ADS)

    Chapman, K.; Ramadhyani, S.; Ramamurthy, H.; Viskanta, R.

    1989-03-01

    A simple two-dimensional mathematical model was developed to predict the steady state thermal performance and combustion characteristics of a natural gas indirectly fired once-through radiant tube. Different burner geometries were studied and a grid size analysis was performed to determine the optimum grid spacing for each case. The rate of fuel burn-up was correlated using the burner geometry, the equivalence ratio, the fuel firing rate and air preheat temperatures as variables for non-swirling diffusion flames in the radiant tube. The model predictions were also compared with available experimental data for the purpose of validating the model. The transient, zero-dimensional model was used to conduct a detailed parametric study of a directly-fired batch reheating furnace. The parameters that were investigated are the load and refractory emissivities, the air preheat temperature, the heat capacity of the load, and the height of the combustion space. A one-dimensional model of a directly-fired continuous reheating furnace was also developed. A parametric study was completed to examine the effect of the local throughput on the furnace performance.

  1. Short duration heat transfer measurements

    NASA Astrophysics Data System (ADS)

    Arts, T.; Camci, C.

    Shock tunnels, blowdown cascades, and isentropic light piston compression tubes used to study heat transfer and aerodynamic phenomena in turbine components are described. Thin film heat transfer gages, calorimeter gages, and optical measurements methods are presented. Compression tube investigations of convective heat transfer on a flat plate, with and without film cooling; and convective heat transfer on a high pressure rotor blade with and without film cooling are summarized. Results show that along the suction side, laminar to turbulent transition is strongly influenced by the presence of the leading edge cooling holes, even when no coolant flow is ejected. Along the pressure side, the boundary layer behavior is dominated by the free stream pressure gradient rather than by the existence of the cooling holes. Significant coolant temperature effects are also observed. At low blowing rate this effect is mainly observed up to 35 to 40 hole diameters downstream of the suction side ejection rows when the coolant temperature is lowered from wall temperature to half of the mainstream level. At high blowing rate, the influence of the coolant temperature is felt much further downstream.

  2. 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.

  3. 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.

  4. 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.

  5. Heat transfer measurements of the 1983 kilauea lava flow.

    PubMed

    Hardee, H C

    1983-10-07

    Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.

  6. Heat-transfer measurements of the 1983 Kilauea lava flow

    SciTech Connect

    Hardee, H.C.

    1983-10-07

    Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.

  7. Heat recovery and melting system for scrap metals

    SciTech Connect

    Jenson, R.E.; Pryor, J.C.

    1982-03-16

    Metallic scrap contaminated with combustibles is melted in a reverberatory melting furnace having two communicating wells; one being an enclosed sidewell, which is the receiving well for scrap material during melting, and the other being an enclosed main holding well for molten metal. The main well has burner means to provide heat for melting the metal and treating the scrap material. Heat from molten metal flowing between the main well and the sidewell produces exhaust gases by vaporizing the combustibles of the scrap material. An external passage circulates the exhaust gases from the sidewell to the main well for incineration by the main well's burner means. The external passage has an eductor means which draws the exhaust gases from the sidewell and propels them towards the main well.

  8. Numerical methods in heat transfer

    SciTech Connect

    Lewis, R.W.; Morgan, K.; Schrefler, B.A.

    1983-01-01

    Topics discussed in this book include modelling the effects of fire, ablation, heat flow in porous rock, thermal stress and dissolving coal. Alternative energy sources such as geothermal reservoirs and solar radiation are also discussed. Includes bibliographies at the end of the papers, a cited author index, and a subject index. Contents, abridged: Exact finite element solutions for linear steady state thermal problems. Steep gradient modelling in diffusion problems. Numerical solution of coupled conduction-convection problems using lumped-parameter methods. The prediction of turbulent heat transfer by the finite element methods. The influence of creep and transformation plasticity in the analysis of stresses due to heat treatment. Heat and moisture movement in wood composite materials during the pressing operation-a simplified model. Index.

  9. Heat Capacity of Hydrous Silicate Melts

    NASA Astrophysics Data System (ADS)

    Robert, G.; Whittington, A. G.; Stechern, A.; Behrens, H.

    2015-12-01

    We determined the heat capacities of four series of glasses and liquids of basaltic and basaltic andesite compositions including two natural remelts from Fuego volcano, Guatemala, and two Fe-free analogs. The samples are low-alkali, Ca- and Mg-rich aluminosilicates with non-bridging oxygen to tetrahedrally-coordinated cation ratios (NBO/T) ranging between 0.33 and 0.67. Differential scanning calorimetry measurements were performed at atmospheric pressure between room temperature and ≈100 K above the glass transition for hydrous samples and up to ≈1800 K for dry samples. The water contents investigated range up to 5.34 wt.% (16.4 mol%). Water does not measurably affect the heat capacity of glasses (T heat capacity, which generally gets larger with increasing water content and with decreasing polymerization. The onset of the glass transition in hydrous samples also occurs below the Dulong-Petit limit of 3R/g atom. We see little change in liquid heat capacity with increasing water content; hydrous liquid heat capacities are within 3-6% of the dry liquid, at low temperatures just above the glass transition. However, dry liquids show a decrease in heat capacity with increasing temperature above the glass transition, from supercooled to superliquidus temperatures. Liquid heat capacity values just above the glass transition range between 95-100 J/mol K, whereas liquid heat capacity values at superliquidus temperatures are between 85-91 J/mol K. Comparison with other studies of the heat capacity of hydrous glasses and liquids shows that the liquid heat capacity of strongly depolymerized samples (NBO/T ≥ 0.8) increases with increasing water content, whereas depolymerized samples (0.4 ≤ NBO/T ≤ 0.8) or polymerized samples (NBO/T ≤ 0.4) generally show little change or a moderate decrease in liquid heat capacity with increasing water content.

  10. Combustion, heat transfer and analysis

    SciTech Connect

    Not Available

    1986-01-01

    This book presents papers on diesel engines combustion. Topics considered include combustion control, high-speed photography, visual studies of diesel combustion, swirl chambers, heat insulated turbochargers, direct injection, autoignition, statistical analysis software, particulate emissions, improvements in exhaust gas emissions and cold startability of diesel engines with new injection-rate-control pumps, jet mixing processes, a thermodynamic simulation model, heat transfer in ceramic combustion chamber walls, temperature distribution in a diesel piston, and the application of a variable swirl device to a two-stroke engine.

  11. Selective tube roughening increases heat transfer capability

    NASA Technical Reports Server (NTRS)

    Carlson, L. W.

    1966-01-01

    Selectively roughening inside surfaces of tubes increases the heat transfer capabilities, but minimizes the pressure drop. This technique is used to construct roughened test sections for hydrogen heat transfer studies.

  12. 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.

  13. Study of Using Solar Thermal Power for the Margarine Melting Heat Process.

    PubMed

    Sharaf Eldean, Mohamed A; Soliman, A M

    2015-04-01

    The heating process of melting margarine requires a vast amount of thermal energy due to its high melting point and the size of the reservoir it is contained in. Existing methods to heat margarine have a high hourly cost of production and use fossil fuels which have been shown to have a negative impact on the environment. Thus, we perform an analytical feasibility study of using solar thermal power as an alternative energy source for the margarine melting process. In this study, the efficiency and cost effectiveness of a parabolic trough collector (PTC) solar field are compared with that of a steam boiler. Different working fluids (water vapor and Therminol-VP1 heat transfer oil (HTO)) through the solar field are also investigated. The results reveal the total hourly cost ($/h) by the conventional configuration is much greater than the solar applications regardless of the type of working fluid. Moreover, the conventional configuration causes a negative impact to the environment by increasing the amount of CO2, CO, and NO2 by 117.4 kg/day, 184 kg/day, and 74.7 kg/day, respectively. Optimized period of melt and tank volume parameters at temperature differences not exceeding 25 °C are found to be 8-10 h and 100 m(3), respectively. The solar PTC operated with water and steam as the working fluid is recommended as a vital alternative for the margarine melting heating process.

  14. Melting of troilite at high pressure in a diamond cell by laser heating

    NASA Technical Reports Server (NTRS)

    Bassett, William A.; Weathers, Maura S.

    1987-01-01

    A system for measuring melting temperatures at high pressures is described. The sample is heated with radiation from a YAG laser. The beam is reflected downward through a microscope objective, through the upper diamond anvil, and focused onto the sample. Hense, intense heating is produced only at the sample and not within the diamond anvils. A vidicon system is used to observe the sample during heating. Incandescent light from the heated sample passes back through the objective lens into a grating spectrometer. The spectrum of the incandescent light is received by the photodiode array and stored in the multichannel analyzer. These data can then be transferred to floppy disk for analysis. A curve fitting program is used to compare the spectra with standard blackbody curves and to determine the temperature. Pressure is measured by the ruby fluorescence method. The system was used to study the melting behavior of natural troilite (FeS).

  15. Slip and frictional heating of extruded polyethylene melts

    NASA Astrophysics Data System (ADS)

    Pérez-González, José; Marín-Santibáñez, Benjamín M.; Zamora-López, Héctor S.; Rodríguez-González, Francisco

    2017-05-01

    Extrusion of polymer melts with slip at the die generates frictional heating. The relationship between slip flow and frictional heating during the continuous extrusion of a non-slipping linear low-density (LLDPE) and a slipping high-density polyethylene (HDPE), respectively, both pure as well as blended with a fluoropolymer processing aid (PA), was investigated in this work by Rheo-particle image velocimetry and thermal imaging. Significant rises in temperature were measured under slip and no slip conditions, being these much higher than the values predicted by the adiabatic flow assumption. Clear difference was made between viscous and frictional heating before the stick-slip regime for the LLDPE, even though they could not be distinguished from one another at higher stresses. Such a difference, however, could not be made for the slipping HDPE, since overall in the presence of slip, frictional and viscous heating act synergistically to increase the melt temperature.

  16. Heat exchanger device and method for heat removal or transfer

    DOEpatents

    Koplow, Jeffrey P [San Ramon, CA

    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.

  17. Heat exchanger device and method for heat removal or transfer

    DOEpatents

    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.

  18. Heat exchanger device and method for heat removal or transfer

    DOEpatents

    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.

  19. Heat exchanger device and method for heat removal or transfer

    DOEpatents

    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.

  20. Flash heating in the diamond cell: melting curve of rhenium.

    PubMed

    Yang, Liuxiang; Karandikar, Amol; Boehler, Reinhard

    2012-06-01

    A new method for measuring melting temperatures in the laser-heated diamond cell is described. This method circumvents previous problems associated with the sample instability, thermal runaway, and chemical reactions. Samples were heated with a single, 20 milliseconds rectangular pulse from a fiber laser, monitoring their thermal response with a fast photomultiplier while measuring the steady state temperature with a CCD spectrometer. The samples were recovered and analyzed using scanning electron microscopy. Focused ion beam milling allowed to examine both the lateral and the vertical solid-liquid boundaries. Ambient pressure tests reproducibly yielded the known melting temperatures of rhenium and molybdenum. Melting of Re was measured to 50 GPa, a 5-fold extension of previous data. The refractory character of Re is drastically enhanced by pressure, in contrast to Mo.

  1. 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…

  2. 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…

  3. Heat transfer enhancement in a paraffin wax thermal storage system

    SciTech Connect

    Eftekhar, J.; Haji-Sheikh, A.; Lou, Y.S.

    1984-08-01

    Heat transfer enhancement in a thermal storage system consisting of vertically arranged fins between a heated and cooled horizontal finned-tube arrangement is reported. The high thermal expansion coefficient and low viscosity of paraffin wax, at temperatures above 50/sup 0/C, are utilized to induce natural convection in the liquid phase even at small thicknesses. The experimental data on the rate of production of liquid as a function of time and temperature of the hot surface is presented. The photographs of the melted zone indicate a naturally buoyant flow induced in the neighborhood of the vertical fins causes a rapid melting of the solid wax and a downdraft along the cooler solid phase surface. The heat transfer coefficient at the interface is calculated from experimentally determined instantaneous locations of the moving boundary.

  4. Peltier heats in cryolite melts with alumina

    SciTech Connect

    Flem, B.E.; Ratkje, S.K.; Sterten, A.

    1996-10-01

    The Seebeck coefficient was measured for cells with electrolytes of molten mixtures of sodium fluoride and aluminum fluoride saturated with alumina. The electrodes were either a pair of oxygen electrodes or a pair of aluminum electrodes. For the molar ratio NaF/AlF{sub 3} equal to 1.8, 1.2 and 1.0, the authors obtained the Seebeck coefficients {minus}1.80 mV K{sup {minus}1} at 971 C, {minus}1.63 mV K{sup {minus}1} at 813.6 C and {minus}0.583 mV K{sup {minus}1} at 758 C, respectively, for the oxygen electrodes. For the aluminum electrodes, the authors obtained the Seebeck coefficient {minus}1.23 mV K{sup {minus}1} at 962 C, for the molar ratio NaF/AlF{sub 3} equal to 1.8. The results suggest that there is a substantial reversible heat consumption at the anode during aluminum electrolysis and a large reversible heat production at the cathode. The highest temperature in the Hall-Heroult cell is then closer to the cathode than the anode. The transported entropies of Al{sup 3+} and O{sup 2{minus}} were calculated to be 77 J mol{sup {minus}1} K{sup {minus}1} and 10 J mol{sup {minus}1} K{sup {minus}1}, respectively, when the molar ratio NaF/AlF{sub 3} was equal to 1.0.

  5. Handbook of heat transfer applications (2nd edition)

    NASA Astrophysics Data System (ADS)

    Rohsenow, W. M.; Hartnett, J. P.; Ganic, E. N.

    The applications of heat transfer in engineering problems are considered. Among the applications discussed are: mass transfer cooling; heat exchangers; and heat pipes. Consideration is also given to: heat transfer in nonNewtonian fluids; fluidized and packed beds; thermal energy storage; and heat transfer in solar collectors. Additional topics include: heat transfer in buildings; cooling towers and ponds; and geothermal heat transfer.

  6. High Resolution Convective Heat Transfer Measurements

    DTIC Science & Technology

    2001-05-30

    ONR Thermal Materials Workshop 2001 1 HIGH RESOLUTION CONVECTIVE HEAT TRANSFER MEASUREMENTS Peter Ireland and Terry Jones R-R UTC in Heat Transfer...temperatures. • Fluid dynamics correct through use of Reynolds number, Mach number and Prandtl number. Mach)Pr,(Re,fNu Dimensionless heat transfer...depends on local h su rf ac e te m p T s gas temperature Tg timestart of test hTc Calibration Test data ONR Thermal Materials Workshop 2001 10 Heat

  7. Heat transfer measurements with TOIRT method

    NASA Astrophysics Data System (ADS)

    Solnař, S.; Petera, K.; Dostál, M.; Jirout, T.

    Temperature Oscillation Infra-Red Thermography (TOIRT) method was used to measure heat transfer coefficients between a at surface and a confined impinging jet generated by an impeller in a difusor and baffled vessel. The TOIRT method is based on measuring a phase-lag between the oscillating heat flux applied to the heat transfer surface and the surface temperature response using a contactless infra-red camera. The phase lag is in a direct relationship with the heat transfer coefficient.

  8. Tunable heat transfer with smart nanofluids.

    PubMed

    Bernardin, Michele; Comitani, Federico; Vailati, Alberto

    2012-06-01

    Strongly thermophilic nanofluids are able to transfer either small or large quantities of heat when subjected to a stable temperature difference. We investigate the bistability diagram of the heat transferred by this class of nanofluids. We show that bistability can be exploited to obtain a controlled switching between a conductive and a convective regime of heat transfer, so as to achieve a controlled modulation of the heat flux.

  9. Study made of transfer of heat energy through metal joints in vacuum environment

    NASA Technical Reports Server (NTRS)

    Elliot, D. H.

    1967-01-01

    Heat energy transfer is concentrated closely around a melted joint and the temperature drop across it decreases rapidly as the bolt and nut are tightened to a minimum torque level. Flat metal surfaces pressed together display a cyclical improvement in heat energy transfer as the interface pressure is increased.

  10. 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

  11. Industrial furnace with improved heat transfer

    SciTech Connect

    Hoetzl, M.; Lingle, T.M.

    1992-07-07

    This patent describes an industrial furnace for heating work which emits volatiles during heating. It comprises a generally cylindrical, closed end furnace section defining a sealable heat transfer chamber for heating work disposed therein; fan means for directing furnace atmosphere as a swirling wind mass about the interior of the furnace section over a portion thereof; heat means for heating the wind mass within the fan chamber; and an incineration track formed as a circumferentially extending groove about the exterior of the furnace section and in heat transfer relationship with and situated at least to extend about a portion of the fan chamber.

  12. Nonaqueous purification of mixed nitrate heat transfer media

    DOEpatents

    Fiorucci, Louis C.; Morgan, Michael J.

    1983-12-20

    A nonaqueous, in-line method for removing carbonate and hydroxide contamination from a molten mixed sodium nitrate/potassium nitrate heat transfer salt. The method comprises dissolving a stoichiometric quantity of anhydrous Ca(NO.sub.3).sub.2 in the melt whereby an insoluble CaCO.sub.3 and Ca(OH).sub.2 precipitate is formed. The precipitate can be removed by settling, filtration or floatation techniques.

  13. Heat Transfer in Gas Turbines

    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.

  14. Convective Heat Transfer for Ship Propulsion.

    DTIC Science & Technology

    1981-04-01

    OF RILJORT 6 PelIOO COVERED Convective Heat Transfer for Ship Propulsion . Annual gummary Report / (Sixth Annual Sumary Report) //115 Jan 180-30 Mard...DO* IrCOVE) Sixth Annual Summary Report CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION By M. A. Habib and D. M. McEligot Aerospace and Mechanical...permitted for any purpose of the United States Government. ._ _ _ _ _ _ I CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION M. A. Habib* and D. M. McEligot

  15. Heat-transfer data for hydrogen

    NASA Technical Reports Server (NTRS)

    Mc Carthy, J. R.; Miller, W. S.; Okuda, A. S.; Seader, J. D.

    1970-01-01

    Information is given regarding experimental heat-transfer data compiled for the turbulent flow of hydrogen within straight, electrically heated, round cross section tubes. Tube materials, test conditions, parameters studied, and generalized conclusions are presented.

  16. Characteristics of Multiple-Pass Heat Exchanger with Melting of Falling Snow

    NASA Astrophysics Data System (ADS)

    Ishikawa, Nobuyuki; Aoki, Kazuo; Hattori, Masaru; Kobayashi, Yoshiharu

    The structure of a multiple-pass heat exchanger composed of pipes and plate fins is similar to that of heat exchangers used for melting snow. In this study, we investigated the characteristics of a multiple-pass heat exchanger having two types, a regular pitch type and an irregular one, focusing on the brine pipe pitch of the multiple-pass heat exchanger. The perfect melting condition and the melting efficiency were related to the dimensionless parameters of the heat exchanger and its operating conditions. The calculated results for the perfect melting condition and the melting efficiency agreed with the results obtained from field tests on melting of falling snow. Applying the irregular pitch extends the critical condition for perfect melting when the flow rate of brine is low or the area for melting of falling snow is large. Also, the melting efficiency of the irregular pitch is higher than that of the regular pitch.

  17. Radiative heat transfer in porous uranium dioxide

    SciTech Connect

    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.

  18. Heat transfer in vertically aligned phase change energy storage systems

    SciTech Connect

    El-Dessouky, H.T.; Bouhamra, W.S.; Ettouney, H.M.; Akbar, M.

    1999-05-01

    Convection effects on heat transfer are analyzed in low temperature and vertically aligned phase change energy storage systems. This is performed by detailed temperature measurements in the phase change material (PCM) in eighteen locations forming a grid of six radial and three axial positions. The system constitutes a double pipe configuration, where commercial grade paraffin wax is stored in the annular space between the two pipes and water flows inside the inner pipe. Vertical alignment of the system allowed for reverse of the flow direction of the heat transfer fluid (HTF), which is water. Therefore, the PCM is heated from the bottom for HTF flow from bottom to top and from the top as the HTF flow direction is reversed. For the former case, natural convection affects the melting process. Collected data are used to study variations in the transient temperature distribution at axial and radial positions as well as for the two-dimensional temperature field. The data are used to calculate the PCM heat transfer coefficient and to develop correlations for the melting Fourier number. Results indicate that the PCM heat transfer coefficient is higher for the case of PCM heating from bottom to top. Nusselt number correlations are developed as a function of Rayleigh, Stefan, and Fourier numbers for the HTF flow from bottom to top and as a function of Stefan and Fourier numbers for HTF flow from top to bottom. The enhancement ratio for heat transfer caused by natural convection increases and then levels off as the inlet temperature of the HTF is increased.

  19. Enhancement of Forced Convection Heat Transfer

    NASA Astrophysics Data System (ADS)

    Tanasawa, Ichiro

    There has been strong demand for enhancement techniques of single-phase forced convection heat transfer because of its wide area of application on the one side and because of inferior heat-transfer capability, when compared with phase change heat transfer such as boiling and condensation, on the other side. The enhancement techniques are indispensable when gases are used as heat-transfer media. In this article the basic principles of enhancement of single-phase forced convection heat transfer are described in the first place. Three principal techniques currently employed, i.e.,(a) interrupted fins, (b) twisted tapes, and (c) turbulence promoters, are introduced. Mechanisms of heat-tansfer enhancement and the state-of-the art review on the R&D are presented for these techniques. In addition to these, supplementary remarks are given on techniques utilizing multiphase flow and electrostatic field.

  20. Beating the Heat - Fast Scanning Melts Silk Beta Sheet Crystals

    NASA Astrophysics Data System (ADS)

    Cebe, Peggy; Hu, Xiao; Kaplan, David L.; Zhuravlev, Evgeny; Wurm, Andreas; Arbeiter, Daniela; Schick, Christoph

    2013-01-01

    Beta-pleated-sheet crystals are among the most stable of protein secondary structures, and are responsible for the remarkable physical properties of many fibrous proteins, such as silk, or proteins forming plaques as in Alzheimer's disease. Previous thinking, and the accepted paradigm, was that beta-pleated-sheet crystals in the dry solid state were so stable they would not melt upon input of heat energy alone. Here we overturn that assumption and demonstrate that beta-pleated-sheet crystals melt directly from the solid state to become random coils, helices, and turns. We use fast scanning chip calorimetry at 2,000 K/s and report the first reversible thermal melting of protein beta-pleated-sheet crystals, exemplified by silk fibroin. The similarity between thermal melting behavior of lamellar crystals of synthetic polymers and beta-pleated-sheet crystals is confirmed. Significance for controlling beta-pleated-sheet content during thermal processing of biomaterials, as well as towards disease therapies, is envisioned based on these new findings.

  1. Beating the Heat - Fast Scanning Melts Silk Beta Sheet Crystals

    PubMed Central

    Cebe, Peggy; Hu, Xiao; Kaplan, David L.; Zhuravlev, Evgeny; Wurm, Andreas; Arbeiter, Daniela; Schick, Christoph

    2013-01-01

    Beta-pleated-sheet crystals are among the most stable of protein secondary structures, and are responsible for the remarkable physical properties of many fibrous proteins, such as silk, or proteins forming plaques as in Alzheimer's disease. Previous thinking, and the accepted paradigm, was that beta-pleated-sheet crystals in the dry solid state were so stable they would not melt upon input of heat energy alone. Here we overturn that assumption and demonstrate that beta-pleated-sheet crystals melt directly from the solid state to become random coils, helices, and turns. We use fast scanning chip calorimetry at 2,000 K/s and report the first reversible thermal melting of protein beta-pleated-sheet crystals, exemplified by silk fibroin. The similarity between thermal melting behavior of lamellar crystals of synthetic polymers and beta-pleated-sheet crystals is confirmed. Significance for controlling beta-pleated-sheet content during thermal processing of biomaterials, as well as towards disease therapies, is envisioned based on these new findings. PMID:23350037

  2. 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.

  3. Impingement Heat Transfer of Reciprocating Jet Array

    NASA Astrophysics Data System (ADS)

    Su, Lo May; Chang, Shyy Woei; Chiou, Shyr Fuu

    This paper describes an experimental study of impingement heat transfer of reciprocating jet-array with piston cooling application for marine heavy-duty diesel engine. A selection of heat transfer measurements illustrates the manner by which the individual and interactive influences of reciprocating force and buoyancy on heat transfer for the impinging jet-array. It is demonstrated that the reciprocating force coupled with buoyancy interaction causes considerable heat transfer modifications from the static results. The isolated reciprocating force effect could initially reduce heat transfer to a level about 0.45 of static level with weak reciprocation but recovers when the reciprocating force increases. Heat transfer improvement and impediment could be aided by the location-dependent buoyancy effect in addition to the reciprocating force effect. An empirical heat transfer correlation, which is physically consistent, has been developed to permit the evaluation of the individual and synergistic effects of reciprocating force and buoyancy interaction on local heat transfer of the impinging jet-array.

  4. Fundamental heat transfer experiments of heat pipes for turbine cooling

    SciTech Connect

    Yamawaki, S.; Yoshida, T.; Taki, M.; Mimura, F.

    1998-07-01

    Fundamental heat transfer experiments were carried out for three kinds of heat pipes that may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B, and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium (Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium (NaK). Heat pipes B and C included noncondensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, an infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm{sup 2}. The start-up time was about 6 minutes for heat pipe B and about 6 minutes for heat pipe A. Thus, adding noncondensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the start-up time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 deg. There was no significant gravitational dependence on heat transport for heat pipes including noncondensible gas.

  5. A novel approach to determine the heat transfer coefficient in directional solidification furnaces

    NASA Technical Reports Server (NTRS)

    Banan, Mohsen; Gray, Ross T.; Wilcox, William R.

    1990-01-01

    The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was determined using an approach utilizing in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the value estimated by standard heat transfer calculations.

  6. Phase Change Heat Transfer Device for Process Heat Applications

    SciTech Connect

    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.

  7. Active latent heat storage with a screw heat exchanger - experimental results for heat transfer and concept for high pressure steam

    NASA Astrophysics Data System (ADS)

    Zipf, Verena; Willert, Daniel; Neuhäuser, Anton

    2016-05-01

    An innovative active latent heat storage concept was invented and developed at Fraunhofer ISE. It uses a screw heat exchanger (SHE) for the phase change during the transport of a phase change material (PCM) from a cold to a hot tank or vice versa. This separates heat transfer and storage tank in comparison to existing concepts. A test rig has been built in order to investigate the heat transfer coefficients of the SHE during melting and crystallization of the PCM. The knowledge of these characteristics is crucial in order to assess the performance of the latent heat storage in a thermal system. The test rig contains a double shafted SHE, which is heated or cooled with thermal oil. The overall heat transfer coefficient U and the convective heat transfer coefficient on the PCM side hPCM both for charging and discharging have been calculated based on the measured data. For charging, the overall heat transfer coefficient in the tested SHE was Uch = 308 W/m2K and for discharging Udis = 210 W/m2K. Based on the values for hPCM the overall heat transfer coefficients for a larger SHE with steam as heat transfer fluid and an optimized geometry were calculated with Uch = 320 W/m2K for charging and Udis = 243 W/m2K for discharging. For pressures as high as p = 100 bar, an SHE concept has been developed, which uses an organic fluid inside the flight of the SHE as working media. With this concept, the SHE can also be deployed for very high pressure, e.g. as storage in solar thermal power plants.

  8. "Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"

    SciTech Connect

    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

  9. Heat transfer coefficient of cryotop during freezing.

    PubMed

    Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J

    2013-01-01

    Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).

  10. Rotary Joint for Heat Transfer

    NASA Technical Reports Server (NTRS)

    Shauback, R.

    1986-01-01

    Rotary joint exchanges heat between two heat pipes - one rotating and one stationary. Joint accommodates varying heat loads with little temperature drop across interface. According to concept, heat pipe enters center of disklike stationary section of joint. There, wicks in central artery of heat pipe separate into multiple strands that lead to concentric channels on rotaryinterface side of stationary disk. Thin layer of liquid sodium/potassium alloy carries heat from one member of rotary joint to other. Liquid conducts heat efficiently while permitting relative motion between members. Polypropylene rings contain liquid without interfering with rotation.

  11. Pool Boiling Heat Transfer on structured Surfaces

    NASA Astrophysics Data System (ADS)

    Addy, J.; Olbricht, M.; Müller, B.; Luke, A.

    2016-09-01

    The development in the process and energy sector shows the importance of efficient utilization of available resources to improve thermal devices. To achieve this goal, all thermal components have to be optimized continuously. Various applications of multi-phase heat and mass transfer have to be improved. Therefore, the heat transfer and the influence of surface roughness in nucleate boiling with the working fluid propane is experimentally investigated on structured mild steel tubes, because only few data are available in the literature. The mild steel tube is sandblasted to obtain different surface roughness. The measurements are carried out over wide ranges of heat flux and pressure. The experimental results are compared with correlations from literature and the effect of surface roughness on the heat transfer is discussed. It is shown that the heat transfer coefficient increases with increasing surface roughness, heat flux and reduced pressure at nucleate pool boiling.

  12. Forced convective heat transfer in curved diffusers

    NASA Technical Reports Server (NTRS)

    Rojas, J.; Whitelaw, J. H.; Yianneskis, M.

    1987-01-01

    Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal thermography in a wind tunnel. The thermographic technique allowed the rapid and inexpensive measurement of wall heat transfer coefficients along flat walls of arbitrary boundary shapes with an accuracy of about 5 percent. The results show that an increase in secondary flow velocities near the heated wall causes an increase in the local wall heat transfer coefficient, and quantify the variation for maximum secondary-flow velocities in a range from 1.5 to 17 percent of the bulk flow velocity.

  13. 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.

  14. Heat-transfer coefficients in agitated vessels. Sensible heat models

    SciTech Connect

    Kumpinsky, E.

    1995-12-01

    Transient models for sensible heat were developed to assess the thermal performance of agitated vessels with coils and jackets. Performance is quantified with the computation of heat-transfer coefficients by introducing vessel heating and cooling data into model equations. Of the two model categories studied, differential and macroscopic, the latter is preferred due to mathematical simplicity and lower sensitivity to experimental data variability.

  15. Heat transfer research on enhanced heating surfaces in pool boiling

    NASA Astrophysics Data System (ADS)

    Kalawa, Wojciech; Wójcik, Tadeusz M.; Piasecka, Magdalena

    The paper focuses on the analysis of the enhanced surfaces in such applications as boiling heat transfer. The testing measurement module with enhanced heating surfaces was used for pool boiling research. Pool boiling experiments were conducted with distilled water at atmospheric pressure in the vessel using an enhanced sample as the bottom heating surface. The samples are soldered to a copper heating block of the round cross-section .They were placed: in the fluid (saturation temperature measurement), under the sample for temperature determination. A vessel made of four flat glass panes was used for visualization. The heated surfaces in contact with the fluid differed in roughness were smooth or enhanced. This paper analyzes the effects of the microstructured heated surface on the heat transfer coefficient. The results are presented as relationships between the heat transfer coefficient and the heat flux and as boiling curves. The experimental data obtained for the two types of enhanced heated surfaces was compared with the results recorded for the smooth heated surface. The highest local values of the heat transfer coefficient were reported for the enhanced surfaces.

  16. Fluid flow and heat transfer in polygonal micro heat pipes

    NASA Astrophysics Data System (ADS)

    Rao, Sai; Wong, Harris

    2015-11-01

    Micro heat pipes have been used to cool microelectronic devices, but their heat transfer coefficients are low compared with those of conventional heat pipes. We model heat and mass transfer in triangular, square, hexagonal, and rectangular micro heat pipes under small imposed temperature differences. A micro heat pipe is a closed microchannel filled with a wetting liquid and a long vapor bubble. When a temperature difference is applied across a micro heat pipe, the equilibrium vapor pressure at the hot end is higher than that at the cold end, and the difference drives a vapor flow. As the vapor moves, the vapor pressure at the hot end drops below the saturation pressure. This pressure drop induces continuous evaporation from the interface. Two dimensionless numbers emerge from the momentum and energy equations: the heat-pipe number H, and the evaporation exponent S. When H >> 1 and S >> 1, vapor-flow heat transfer dominates and a thermal boundary layer appears at the hot end, the thickness of which scales as L/S, where L is the half-length of the pipe. A similar boundary layer exists at the cold end. Outside the boundary layers, the temperature is uniform. We also find a dimensionless optimal pipe length Sm =Sm(H) for maximum evaporative heat transfer. Thus, our model suggests that micro heat pipes should be designed with H >> 1 and S =Sm. We calculate H and S for four published micro-heat-pipe experiments, and find encouraging support for our design criterion.

  17. Development of advanced low-temperature heat transfer fluids for district heating and cooling

    SciTech Connect

    Not Available

    1991-09-30

    The feasibility of adding phase change materials (PCMs) and surfactants to the heat transfer fluids in district cooling systems was investigated. It increases the thermal capacity of the heat transfer fluid and therefore decreases the volume that needs to be pumped. It also increases the heat transfer rate, resulting in smaller heat exchangers. The thermal behavior of two potential PCMs, hexadecane and tetradecane paraffin wax, was experimentally evaluated. The heat of fusion of these materials is approximately 60% of that of ice. They exhibit no supercooling and are stable under repeated thermal cycling. While test results for laboratory grade materials showed good agreement with data in the literature, both melting point and heat of fusion for commercial grade hexadecane were found to be considerably lower than literaturevalues. PCM/water mixtures were tested in a laboratory-scale test loop to determine heat transfer and flow resistance properties. When using PCMs in district cooling systems, clogging of frozen PCM particles isone of the major problems to be overcome. In the present project it is proposed to minimize or prevent clogging by the addition of an emulsifier. Effects of the emulsifier on the mixture of water and hexadecane(a PCM) were studied. As the amount of the emulsifier was increased, the size of the solid PCM particles became smaller. When the size of the particles was small enough, they did not stick together or stick to the cold surface of a heat exchanger. The amount of emulsifier to produce this condition was determined.

  18. ASME Heat Transfer Division: Proceedings. Volume 1: Heat transfer in microgravity systems, radiative heat transfer and radiative heat transfer in low-temperature environments, and thermal contact conductance and inverse problems in heat transfer; HTD-Volume 332

    SciTech Connect

    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.

  19. Thermographic heat transfer measurements in separated flows

    NASA Astrophysics Data System (ADS)

    Scherer, V.; Wittig, S.; Bittlinger, G.; Pfeiffer, A.

    1993-12-01

    A measurement technique to determine the surface heat transfer distribution in complex turbulent flows is described. For this purpose, a constant wall heat flux test surface has been designed. To measure the surface temperature of the test plate, an infrared camera was used. The instrumentation allows the determination of the heat transfer with high accuracy and detailed spatial resolution. In examining combustor-type separated flow, the capabilities of the technique are demonstrated and its accuracy is verified by appropriate conventional techniques.

  20. Heat flow in impact melts - Apollo 17 Station 6 Boulder and some applications to other breccias and xenolith laden melts

    NASA Technical Reports Server (NTRS)

    Onorato, P. I. K.; Uhlmann, D. R.; Simonds, C. H.

    1976-01-01

    The paper presents results of calculations for the cooling of an impact melt, the specific application being the clast-laden sheet sampled in the Apollo 17 Station 6 Boulder. The calculations were carried out using a two-stage cooling model which involves a short initial phase of thermal equilibration between small clasts and the surrounding melt and a second phase of heat loss from the melt sheet to the surroundings.

  1. Transport phenomena of crystal growth—heat and mass transfer

    NASA Astrophysics Data System (ADS)

    Rudolph, Peter

    2010-07-01

    Selected fundamentals of transport processes and their importance for crystal growth are given. First, principal parameters and equations of heat and mass transfer, like thermal flux, radiation and diffusion are introduced. The heat- and mass- balanced melt-solid and solution-solid interface velocities are derived, respectively. The today's significance of global numeric simulation for analysis of thermo-mechanical stress and related dislocation dynamics within the growing crystal is shown. The relation between diffusion and kinetic regime is discussed. Then, thermal and solutal buoyancy-driven and Marangoni convections are introduced. Their important interplay with the diffusion boundary layer, component and particle incorporation as well as morphological interface stability is demonstrated. Non-steady crystallization phenomena (striations) caused by convective fluctuations are considered. Selected results of global 3D numeric modeling are shown. Finally, advanced methods to control heat and mass transfer by external forces, such as accelerated container rotation, ultrasonic vibration and magnetic fields are discussed.

  2. Heat Transfer and Latent Heat Storage in Inorganic Molten Salts for Concentrating Solar Power Plants

    SciTech Connect

    Mathur, Anoop

    2013-08-14

    A key technological issue facing the success of future Concentrating Solar Thermal Power (CSP) plants is creating an economical Thermal Energy Storage (TES) system. Current TES systems use either sensible heat in fluids such as oil, or molten salts, or use thermal stratification in a dual-media consisting of a solid and a heat-transfer fluid. However, utilizing the heat of fusion in inorganic molten salt mixtures in addition to sensible heat , as in a Phase change material (PCM)-based TES, can significantly increase the energy density of storage requiring less salt and smaller containers. A major issue that is preventing the commercial use of PCM-based TES is that it is difficult to discharge the latent heat stored in the PCM melt. This is because when heat is extracted, the melt solidifies onto the heat exchanger surface decreasing the heat transfer. Even a few millimeters of thickness of solid material on heat transfer surface results in a large drop in heat transfer due to the low thermal conductivity of solid PCM. Thus, to maintain the desired heat rate, the heat exchange area must be large which increases cost. This project demonstrated that the heat transfer coefficient can be increase ten-fold by using forced convection by pumping a hyper-eutectic salt mixture over specially coated heat exchanger tubes. However,only 15% of the latent heat is used against a goal of 40% resulting in a projected cost savings of only 17% against a goal of 30%. Based on the failure mode effect analysis and experience with pumping salt at near freezing point significant care must be used during operation which can increase the operating costs. Therefore, we conclude the savings are marginal to justify using this concept for PCM-TES over a two-tank TES. The report documents the specialty coatings, the composition and morphology of hypereutectic salt mixtures and the results from the experiment conducted with the active heat exchanger along with the lessons learnt during

  3. Low Melt Viscosity Resins for Resin Transfer Molding

    NASA Technical Reports Server (NTRS)

    Harris, Frank W.

    2002-01-01

    In recent years, resin transfer molding (RTM) has become one of the methods of choice for high performance composites. Its cost effectiveness and ease of fabrication are major advantages of RTM. RTM process usually requires resins with very low melt viscosity (less than 10 Poise). The optimum RTM resins also need to display high thennal-oxidative stability, high glass transition temperature (T(sub g)), and good toughness. The traditional PMR-type polyimides (e.g. PMR-15) do not fit this requirement, because the viscosities are too high and the nadic endcap cures too fast. High T(sub g), low-melt viscosity resins are highly desirable for aerospace applications and NASA s Reusable Launch Vehicle (RLV) program. The objective of this work is to prepare low-melt viscosity polyimide resins for RTM or resin film infusion (RFI) processes. The approach involves the synthesis of phenylethynyl-terminated imide oligomers. These materials have been designed to minimize their melt viscosity so that they can be readily processed. During the cure, the oligomers undergo both chain extension and crosslinking via the thermal polymerization of the phenylethynyl groups. The Phenylethynyl endcap is preferred over the nadic group due to its high curing temperature, which provides broader processing windows. This work involved the synthesis and polymerization of oligomers containing zig-zag backbones and twisted biphenyl structures. Some A-B type precursors which possessed both nitro and anhydride functionality, or both nitro and amine functionality, were also synthesized in order to obtain the well defined oligomers. The resulting zig-zag structured oligomers were then end-capped with 4-phenylethynylphthalic anhydride (PEPA) for further cure. The properties of these novel imide oligomers are evaluated.

  4. Space Mission Utility and Requirements for a Heat Melt Compactor

    NASA Technical Reports Server (NTRS)

    Fisher, John W.; Lee, Jeffrey M.

    2016-01-01

    Management of waste on long-duration space missions is both a problem and an opportunity. Uncontained or unprocessed waste is a crew health hazard and a habitat storage problem. A Heat Melt Compactor (HMC) such as NASA has been developing is capable of processing space mission trash and converting it to useful products. The HMC is intended to process space mission trash to achieve a number of objectives including: volume reduction, biological safening and stabilization, water recovery, radiation shielding, and planetary protection. This paper explores the utility of the HMC to future space missions and how this translates into HMC system requirements.

  5. Source Contaminant Control for the Heat Melt Compactor

    NASA Technical Reports Server (NTRS)

    Roman, Monsi; Howard, David

    2015-01-01

    The Logistics Reduction and Repurposing project includes the heat melt compactor (HMC), a device that compacts waste containing plastic into a tile that will minimize volume, and may be used as materials for radiation shielding. During the process, a small purge gas stream is directed through the HMC chamber to transport out gasses and humidity released from the process. NASA Marshall Space Flight Center is tasked with developing and delivering a contamination control system to clean the purge gas prior to exhausting it back into the cabin for crew inhalation.

  6. Heat transfer characteristics of rotating triangular thermosyphon

    NASA Astrophysics Data System (ADS)

    Ibrahim, E.; Moawed, M.; Berbish, N. S.

    2012-09-01

    An experimental investigation is carried out to study heat transfer characteristics of a rotating triangular thermosyphon, using R-134a refrigerant as the working fluid. The tested thermosyphon is an equilateral triangular tube made from copper material of 11 mm triangular length, 2 mm thickness, and a total length of 1,500 mm. The length of the evaporator section is 600 mm, adiabatic section is 300 mm, and condenser section is 600 mm. The effects of the rotational speed, filling ratio, and the evaporator heat flux on each of the evaporator heat transfer coefficient, he, condenser heat transfer coefficient, hc, and the overall effective thermal conductance, Ct are studied. Experiments are performed with a vertical position of thermosyphon within heat flux ranges from 11 to 23 W/m2 for the three selected filling ratios of 10, 30 and 50 % of the evaporator section volume. The results indicated that the maximum values of the tested heat transfer parameters of the rotational equilateral triangular thermosyphon are obtained at the filling ratio of 30 %. Also, it is found that the heat transfer coefficient of the condensation is increased with increasing the rotational speed. The tested heat transfer parameters of the thermosyphon are correlated as a function of the evaporator heat flux and angular velocity.

  7. Heat Transfer in Metal Foam Heat Exchangers at High Temperature

    NASA Astrophysics Data System (ADS)

    Hafeez, Pakeeza

    Heat transfer though open-cell metal foam is experimentally studied for heat exchanger and heat shield applications at high temperatures (˜750°C). Nickel foam sheets with pore densities of 10 and 40 pores per linear inch (PPI), have been used to make the heat exchangers and heat shields by using thermal spray coating to deposit an Inconel skin on a foam core. Heat transfer measurements were performed on a test rig capable of generating hot gas up to 1000°C. The heat exchangers were tested by exposing their outer surface to combustion gases at a temperature of 550°C and 750°C while being cooled by air flowing through them at room temperature at velocities up to 5 m/s. The temperature rise of the air, the surface temperature of the heat exchangers and the air temperature inside the heat exchanger were measured. The volumetric heat transfer coefficient and Nusselt number were calculated for different velocities. The heat transfer performance of the 40PPI sample brazed with the foil is found to be the most efficient. Pressure drop measurements were also performed for 10 and 40PPI metal foam. Thermographic measurements were done on 40PPI foam heat exchangers using a high temperature infrared camera. A high power electric heater was used to produce hot air at 300°C that passed over the foam heat exchanger while the cooling air was blown through it. Heat shields were made by depositing porous skins on metal foam and it was observed that a small amount of coolant leaking through the pores notably reduces the heat transfer from the hot gases. An analytical model was developed based assuming local thermal non-equilibrium that accounts for the temperature difference between solid and fluid phase. The experimental results are found to be in good agreement with the predicted values of the model.

  8. Heating and melting of small icy satellites by the decay of 26Al.

    PubMed

    Prialnik, D; Bar-Nun, A

    1990-05-20

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors.

  9. Heating and melting of small icy satellites by the decay of 26Al

    NASA Technical Reports Server (NTRS)

    Prialnik, D.; Bar-Nun, A.; Owen, T. (Principal Investigator)

    1990-01-01

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors.

  10. Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger.

    PubMed

    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.

  11. Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger

    PubMed Central

    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

  12. Novel Heat Transfer Device Research

    DTIC Science & Technology

    2012-04-01

    Thermography Comparison of the Qu Tube with the Wicked Heat Pipe .................. 4 3.3 Quantitative Characterization of both Qu Tube and Heat Pipe...the Qu Tube operations in comparison with a wicked water heat pipe using the IR thermography . III. Quantitative characterization of both Qu Tubes...4 Approved for public release; distribution unlimited. Figure 2: X-Ray Images of Copper Heat Pipes 3.2 IR Thermography

  13. Van der Waals Force Assisted Heat Transfer

    NASA Astrophysics Data System (ADS)

    Sasihithlu, K.; Pendry, J. B.; Craster, R. V.

    2017-02-01

    Phonons (collective atomic vibrations in solids) are more effective in transporting heat than photons. This is the reason why the conduction mode of heat transport in nonmetals (mediated by phonons) is dominant compared to the radiation mode of heat transport (mediated by photons). However, since phonons are unable to traverse a vacuum gap (unlike photons), it is commonly believed that two bodies separated by a gap cannot exchange heat via phonons. Recently, a mechanism was proposed [J. B. Pendry, K. Sasihithlu, and R. V. Craster, Phys. Rev. B 94, 075414 (2016)] by which phonons can transport heat across a vacuum gap - through the Van der Waals interaction between two bodies with gap less than the wavelength of light. Such heat transfer mechanisms are highly relevant for heating (and cooling) of nanostructures; the heating of the flying heads in magnetic storage disks is a case in point. Here, the theoretical derivation for modelling phonon transmission is revisited and extended to the case of two bodies made of different materials separated by a vacuum gap. Magnitudes of phonon transmission, and hence the heat transfer, for commonly used materials in the micro- and nano-electromechanical industry are calculated and compared with the calculation of conduction heat transfer through air for small gaps as well as the heat transfer calculation due to photon exchange.

  14. Analysis of Water Recovery Rate from the Heat Melt Compactor

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Hegde, U.; Gokoglu, S.

    2013-01-01

    Human space missions generate trash with a substantial amount of plastic (20% or greater by mass). The trash also contains water trapped in food residue and paper products and other trash items. The Heat Melt Compactor (HMC) under development by NASA Ames Research Center (ARC) compresses the waste, dries it to recover water and melts the plastic to encapsulate the compressed trash. The resulting waste disk or puck represents an approximately ten-fold reduction in the volume of the initial trash loaded into the HMC. In the current design concept being pursued, the trash is compressed by a piston after it is loaded into the trash chamber. The piston face, the side walls of the waste processing chamber and the end surface in contact with the waste can be heated to evaporate the water and to melt the plastic. Water is recovered by the HMC in two phases. The first is a pre-process compaction without heat or with the heaters initially turned on but before the waste heats up. Tests have shown that during this step some liquid water may be expelled from the chamber. This water is believed to be free water (i.e., not bound with or absorbed in other waste constituents) that is present in the trash. This phase is herein termed Phase A of the water recovery process. During HMC operations, it is desired that liquid water recovery in Phase A be eliminated or minimized so that water-vapor processing equipment (e.g., condensers) downstream of the HMC are not fouled by liquid water and its constituents (i.e., suspended or dissolved matter) exiting the HMC. The primary water recovery process takes place next where the trash is further compacted while the heated surfaces reach their set temperatures for this step. This step will be referred to herein as Phase B of the water recovery process. During this step the waste chamber may be exposed to different selected pressures such as ambient, low pressure (e.g., 0.2 atm), or vacuum. The objective for this step is to remove both bound and

  15. 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.

  16. 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.

  17. Conjugate heat transfer characterization in cooling channels

    NASA Astrophysics Data System (ADS)

    Cukurel, Beni; Arts, Tony; Selcan, Claudio

    2012-06-01

    Cooling technology of gas turbine blades, primarily ensured via internal forced convection, is aimed towards withdrawing thermal energy from the airfoil. To promote heat exchange, the walls of internal cooling passages are lined with repeated geometrical flow disturbance elements and surface non-uniformities. Raising the heat transfer at the expense of increased pressure loss; the goal is to obtain the highest possible cooling effectiveness at the lowest possible pressure drop penalty. The cooling channel heat transfer problem involves convection in the fluid domain and conduction in the solid. This coupled behavior is known as conjugate heat transfer. This experimental study models the effects of conduction coupling on convective heat transfer by applying iso-heat-flux boundary condition at the external side of a scaled serpentine passage. Investigations involve local temperature measurements performed by Infrared Thermography over flat and ribbed slab configurations. Nusselt number distributions along the wetted surface are obtained by means of heat flux distributions, computed from an energy balance within the metal domain. For the flat plate experiments, the effect of conjugate boundary condition on heat transfer is estimated to be in the order of 3%. In the ribbed channel case, the normalized Nusselt number distributions are compared with the basic flow features. Contrasting the findings with other conjugate and convective iso-heat-flux literature, a high degree of overall correlation is evident.

  18. Experimental investigation of interfacial heat transfer for molten metal solidification on a substrate

    SciTech Connect

    Wang, G.X.; Matthys, E.F.

    1995-12-31

    Thermal contact at the melt/substrate interface is an important issue in many material processes such as mold casting, strip and slab casting, splat cooling, melt-spinning, spray deposition, etc. In all these processes, the molten metal is brought in contact with a colder substrate, and the heat is transferred from the melt into this substrate. Here, experiments have been conducted to quantify the interfacial heat transfer between molten copper and a cold metallic substrate, and in particular to investigate the heat transfer variation as the initial liquid/solid contact becomes a solid/solid contact after nucleation. A high heat transfer coefficient (ranging from 10{sup 4} to 10{sup 5} W/m{sup 2}K) during the earlier liquid cooling phase and a lower heat transfer coefficient (from 10{sup 3} to 10{sup 4} W/m{sup 2}K) during the subsequent solid splat cooling phase were estimated through matching of model calculations and measured temperature history of the sample. The dynamic variations in the interfacial heat transfer resulting from the solidification process were quantified for splat cooling and were found to be affected by the melt superheat, the substrate material, and the substrate surface finish.

  19. Passive heat transfer means for nuclear reactors

    SciTech Connect

    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.

  20. Convective Heat Transfer for Ship Propulsion.

    DTIC Science & Technology

    1980-01-30

    Report Contract No. N00014-75-C-0694 Contract Authority NR-097-395 I0 I CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION Prepared for Office of Naval...Vj~ / TITE find~&ie S.~ TYPE OF REPOAT-& PERIOD COVERED CovcieHeat Transfer for Ship Propulsion # nna umary /epS’Ptoi ", 1’ . Anua MING 14G RE an...ee Fifth Annual Summary Report CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION By S. E. Faas and D. M. McEligot Aerospace and Mechanical Engineering

  1. Fundamental phenomena governing heat transfer during rolling

    NASA Astrophysics Data System (ADS)

    Chen, W. C.; Samarasekera, I. V.; Hawbolt, E. B.

    1993-06-01

    To quantify the effect of roll chilling on the thermal history of a slab during hot rolling, tests were conducted at the Canada Center for Mineral and Energy Technology (CANMET) and at the University of British Columbia (UBC). In these tests, the surface and the interior temperatures of specimens were recorded during rolling using a data acquisition system. The corresponding heat-transfer coefficients in the roll bite were back-calculated by a trial-and-error method using a heat-transfer model. The heat-transfer coefficient was found to increase along the arc of contact and reach a maximum, followed by a decrease, until the exit of the roll bite. Its value was influenced by rolling parameters, such as percent reduction, rolling speed, rolling temperature, material type, etc. It was shown that the heat-transfer coefficient in the roll gap was strongly dependent on the roll pressure, and the effect of different variables on the interfacial heat-transfer coefficient can be related to their influence on pressure. At low mean roll pressure, such as in the case of rolling plain carbon steels at elevated temperature, the maximum heat-transfer coefficient in the roll bite was in the 25 to 35 kW/m2 °C range. As the roll pressure increased with lower rolling temperature and higher deformation resistance of stainless steel and microalloyed grades, the maximum heat-transfer coefficient reached a value of 620 kW/m2 °C. Obviously, the high pressure improved the contact between the roll and the slab surface, thereby reducing the resistance to heat flow. The mean roll-gap heat-transfer coefficient at the interface was shown to be linearly related to mean roll pressure. This finding is important because it permitted a determination of heat-transfer coefficients applicable to industrial rolling from pilot mill data. Thus, the thermal history of a slab during rough rolling was computed using a model in which the mean heat-transfer coefficient between the roll and the slab was

  2. Control of heat transfer in continuous-feeding Czochralski-silicon crystal growth with a water-cooled jacket

    NASA Astrophysics Data System (ADS)

    Zhao, Wenhan; Liu, Lijun

    2017-01-01

    The continuous-feeding Czochralski method is an effective method to reduce the cost of single crystal silicon. By promoting the crystal growth rate, the cost can be reduced further. However, more latent heat will be released at the melt-crystal interface under a high crystal growth rate. In this study, a water-cooled jacket was applied to enhance the heat transfer at the melt-crystal interface. Quasi-steady-state numerical calculation was employed to investigate the impact of the water-cooled jacket on the heat transfer at the melt-crystal interface. Latent heat released during the crystal growth process at the melt-crystal interface and absorbed during feedstock melting at the feeding zone was modeled in the simulations. The results show that, by using the water-cooled jacket, heat transfer in the growing crystal is enhanced significantly. Melt-crystal interface deflection and thermal stress increase simultaneously due to the increase of radial temperature at the melt-crystal interface. With a modified heat shield design, heat transfer at the melt-crystal interface is well controlled. The crystal growth rate can be increased by 20%.

  3. Heat transfer enhancement using 2MHz ultrasound.

    PubMed

    Bulliard-Sauret, Odin; Ferrouillat, Sebastien; Vignal, Laure; Memponteil, Alain; Gondrexon, Nicolas

    2017-11-01

    The present work focuses on possible heat transfer enhancement from a heating plate towards tap water in forced convection by means of 2MHz ultrasound. The thermal approach allows to observe the increase of local convective heat transfer coefficients in the presence of ultrasound and to deduce a correlation between ultrasound power and Nusselt number. Heat transfer coefficient under ultrasound remains constant while heat transfer coefficient under silent conditions increases with Reynolds number from 900 up to 5000. Therefore, heat transfer enhancement factor ranges from 25% up to 90% for the same energy conditions (supplied ultrasonic power=110W and supplied thermal power=450W). In the same time cavitational activity due to 2MHz ultrasound emission was characterized from mechanical and chemical viewpoints without significant results. At least, Particle Image Velocimetry (PIV) measurements have been performed in order to investigate hydrodynamic modifications due to the presence of 2MHz ultrasound. It was therefore possible to propose a better understanding of heat transfer enhancement mechanism with high frequency ultrasound. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. 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

  5. Heat Transfer Correlations for compressible flow in Micro Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Coppola, M. A.; Croce, G.

    2016-09-01

    The paper discusses the definition of dimensionless parameters useful to define a local correlation for convective heat transfer in compressible, micro scale gaseous flows. A combination of static and stagnation temperatures is chosen, as it allows to weight the temperature change related to the heat transfer and that induced by conversion of internal energy into kinetic one. The correlation offers a purely convective local Nusselt number, i.e. correlating the heat flow rate with the local flow parameters and wall surface temperature. The correlation is validated through a series of numerical computations in both counter-current and co-current micro heat exchanger configurations. The numerical computations take into account rarefaction and conjugate heat transfer effects.

  6. Coolant passage heat transfer with rotation

    NASA Technical Reports Server (NTRS)

    Rohde, J. E.

    1982-01-01

    Although the effects of the coriolis and buoyancy forces due to rotation on coolant-side heat transfer are generally not included in the design methods for blades, the influence of these forces could be large. Comparisons of nonrotating heat transfer data and extrapolations of available correlation for the average heat transfer coefficients with radial outflow of cooling air showed that neglecting rotation at gas turbine engine conditions result in variations in the heat transfer coefficient by as much as 45 percent. This, in effect, results in blade metal temperatures running as much as 100 F different from predicted values. This also may explain why rotating blade metal temperatures in engine tests are often higher than expected from results obtained in nonrotating cascade tests.

  7. Cooling Heat Transfer of Supercritical Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Dang, Chaobin; Hihara, Eiji

    The characteristics of carbon dioxide cooled under supercritical condition were investigated theoretically and experimentally. Based on the results of numerical calculation and experimental measurements described in the 1st report, a new correlation was proposed to predict the heat transfer coefficient, and the Filonenko's equation was found adequate to predict the pressure drop inside as mall seized tube. Those correlations were compared with measurement results and the deviations were found lower than ±20%. Furthermore, a compressor cycle was assembled to investigate the effect of lubricant oil on heat transfer and pressure drop. The oil content in CO2 was set to be about 0.5% during the measurements. This amount of lubricant oil was found affected the heat transfer coefficient significantly, with largest degradation of heat transfer coefficient at the pseudocritical point to nearly 50%. The effect of lubricant oil at small concentration on the pressure drop was found negligible.

  8. Solving nonlinear heat transfer constant area fin problems

    NASA Technical Reports Server (NTRS)

    1968-01-01

    Tables and graphs were compiled for solving nonlinear heat transfer constant area fin problems. The differential equation describing one-dimensional steady-state temperature distribution and heat flow under three modes of heat transfer with heat generation was investigated.

  9. Nanoparticle enhanced ionic liquid heat transfer fluids

    DOEpatents

    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.

  10. Convective Heat Transfer for Ship Propulsion.

    DTIC Science & Technology

    1982-04-01

    RD-A124 Wi CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION (U) ARIZONA 112 UNIV TUCSON ENGINEERING EXPERIMENT STATION PARK ET AL. 01 APR 82 1248-9 N814...395 CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION Prepared for Office of Naval Research Code 431 Arlington, Virginia Prepared by J. S. Park, M. F...FOR SHIP PROPULSION By J. S. Park, M. F. Taylor and D. M. McEligot Aerospace and Mechanical Engineering Department University of Arizona Tucson

  11. Condensation heat transfer in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Chow, L. C.; Parish, R. C.

    1986-01-01

    In the present treatment of the condensation heat transfer process in a microgravity environment, two mechanisms for condensate removal are analyzed in light of two problems: (1) film condensation on a flat, porous plate, with condensate being removed by wall suction; and (2) the analytical prediction of the heat transfer coefficient of condensing annular flows, where the condensate film is driven by vapor shear. Both suction and vapor shear can effectively drain the condensate, ensuring continuous operation in microgravity.

  12. Analytical Prediction of Turbulent Heat Transfer Parameters.

    DTIC Science & Technology

    1985-04-01

    ofMaterfals (McGraw-Hill, equations show that the resistive bending moment in the New York, 1949), p. 184. cross section is OA . Bejan. J. Heat Transfer...178011981. graphed wavelengths agree with each other and with the ’ OA . Bejan, Lett. Heat Mass Transfer 8, 187 119810. buckling wavelength -’D/2...nicht- tear hslresaemto.wiht oeft ’ zahe Bereich der Fahne (die _Fahnensdule-) elastische Eigen- * schaften besitzt ihnlich jener elastischer Stiibe

  13. Heat transfer mechanisms in microgravity flow boiling.

    PubMed

    Ohta, Haruhiko

    2002-10-01

    The objective of this paper is to clarify the mechanisms of heat transfer and dryout phenomena in flow boiling under microgravity conditions. Liquid-vapor behavior in annular flow, encountered in the moderate quality region, has extreme significance for practical application in space. To clarify the gravity effect on the heat transfer observed for an upward flow in a tube, the research described here started from the measurement of pressure drop for binary gas-liquid mixture under various gravity conditions. The shear stress acting on the surface of the annular liquid film was correlated by an empirical method. Gravity effects on the heat transfer due to two-phase forced convection were investigated by the analysis of velocity and temperature profiles in the film. The results reproduce well the trends of heat transfer coefficients varying with the gravity level, quality, and mass velocity. Dryout phenomena in the moderate quality region were observed in detail by the introduction of a transparent heated tube. At heat fluxes just lower and higher than CHF value, a transition of the heat transfer coefficient was calculated from oscillating wall temperature, where a series of opposing heat transfer trends--the enhancement due to the quenching of dried areas or evaporation from thin liquid films and the deterioration due to the extension of dry patches--were observed between the passage of disturbance waves. The CHF condition that resulted from the insufficient decrease of wall temperature in the period of enhanced heat transfer was overcome by a temperature increase in the deterioration period. No clear effect of gravity on the mechanisms of dryout was observed within the range of experiments.

  14. 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.

  15. Coupled reactor kinetics and heat transfer model for heat pipe cooled reactors

    NASA Astrophysics Data System (ADS)

    Wright, Steven A.; Houts, Michael

    2001-02-01

    Heat pipes are often proposed as cooling system components for small fission reactors. SAFE-300 and STAR-C are two reactor concepts that use heat pipes as an integral part of the cooling system. Heat pipes have been used in reactors to cool components within radiation tests (Deverall, 1973); however, no reactor has been built or tested that uses heat pipes solely as the primary cooling system. Heat pipe cooled reactors will likely require the development of a test reactor to determine the main differences in operational behavior from forced cooled reactors. The purpose of this paper is to describe the results of a systems code capable of modeling the coupling between the reactor kinetics and heat pipe controlled heat transport. Heat transport in heat pipe reactors is complex and highly system dependent. Nevertheless, in general terms it relies on heat flowing from the fuel pins through the heat pipe, to the heat exchanger, and then ultimately into the power conversion system and heat sink. A system model is described that is capable of modeling coupled reactor kinetics phenomena, heat transfer dynamics within the fuel pins, and the transient behavior of heat pipes (including the melting of the working fluid). This paper focuses primarily on the coupling effects caused by reactor feedback and compares the observations with forced cooled reactors. A number of reactor startup transients have been modeled, and issues such as power peaking, and power-to-flow mismatches, and loading transients were examined, including the possibility of heat flow from the heat exchanger back into the reactor. This system model is envisioned as a tool to be used for screening various heat pipe cooled reactor concepts, for designing and developing test facility requirements, for use in safety evaluations, and for developing test criteria for in-pile and out-of-pile test facilities. .

  16. Examination of Liquid Fluoride Salt Heat Transfer

    SciTech Connect

    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

  17. Heat transfer between fish and ambient water.

    PubMed

    Stevens, E D; Sutterlin, A M

    1976-08-01

    1. The ability of fish gills to transfer heat was measured by applying a heat pulse to blood in the ventral aorta and measuring it before and after passing through the gills of a teleost, Hemitripterus americanus. 2. 80-90% of heat contained in the blood is lost during passage through the gills. 3. The fraction of heat not lost during passage through the gills is due to direct transfer of heat between the afferent and efferent artery within the gill bar. 4. The major fraction of metabolic heat (70 - 90%) is lost through the body wall and fins of the sea raven in sea water at 5 degrees C; the remainder is lost through the gills.

  18. Conjugate Heat Transfer Study in Hypersonic Flows

    NASA Astrophysics Data System (ADS)

    Sahoo, Niranjan; Kulkarni, Vinayak; Peetala, Ravi Kumar

    2017-05-01

    Coupled and decoupled conjugate heat transfer (CHT) studies are carried out to imitate experimental studies for heat transfer measurement in hypersonic flow regime. The finite volume based solvers are used for analyzing the heat interaction between fluid and solid domains. Temperature and surface heat flux signals are predicted by both coupled and decoupled CHT analysis techniques for hypersonic Mach numbers. These two methodologies are also used to study the effect of different wall materials on surface parameters. Effectiveness of these CHT solvers has been verified for the inverse problem of wall heat flux recovery using various techniques reported in the literature. Both coupled and decoupled CHT techniques are seen to be equally useful for prediction of local temperature and heat flux signals prior to the experiments in hypersonic flows.

  19. 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,…

  20. 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,…

  1. 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

  2. Study on Snow-Melting System around Steel Top of Underground Fire Cistern using Heat Pipe

    NASA Astrophysics Data System (ADS)

    Nagai, Niro; Nakano, Norimasa; Takeuchi, Masanori; Maekawa, Yoshitaka; Maegawa, Yoshikazu

    This research aims to develop snow melting system around steel top of underground fire cistern by using heat pipe, for realizing quick finding of the steel top under heavy snow fall. Water in a fire cistern installed underground is heated by underground heat source, 10 ~15 °C. The iron top is put on snow melting panel made of reinforced concrete. Heat is transported from water to the snow melting panel by heat pipes, which melts snow on it. The experimental results obtained for two years show that this system can melt the snow around the steel top in winter season preferably. The numerical simulation using only weather data was found to predict temperature variations of the whole system with good agreements to the experimental data. Therefore, this simulation software can be used for designing this snow-melting system.

  3. 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.

  4. Melting and solidification characteristics of a mixture of two types of latent heat storage material in a vessel

    NASA Astrophysics Data System (ADS)

    Yu, JikSu; Horibe, Akihiko; Haruki, Naoto; Machida, Akito; Kato, Masashi

    2016-11-01

    In this study, we investigated the fundamental melting and solidification characteristics of mannitol, erythritol, and their mixture (70 % by mass mannitol: 30 % by mass erythritol) as potential phase-change materials (PCMs) for latent heat thermal energy storage systems, specifically those pertaining to industrial waste heat, having temperatures in the range of 100-250 °C. The melting point of erythritol and mannitol, the melting peak temperature of their mixture, and latent heat were measured using differential scanning calorimetry. The thermal performance of the mannitol mixture was determined during melting and solidification processes, using a heat storage vessel with a pipe heat exchanger. Our results indicated phase-change (fusion) temperatures of 160 °C for mannitol and 113 and 150 °C for the mannitol mixture. Nondimensional correlation equations of the average heat transfer during the solidification process, as well as the temperature and velocity efficiencies of flowing silicon oil in the pipe and the phase-change material (PCM), were derived using several nondimensional parameters.

  5. Bistable heat transfer in a nanofluid.

    PubMed

    Donzelli, Gea; Cerbino, Roberto; Vailati, Alberto

    2009-03-13

    Heat convection in water can be suppressed by adding a small amount of highly thermophilic nanoparticles. We show that such suppression is not effective when a suspension with uniform concentration of nanoparticles is suddenly heated from below. At Rayleigh numbers smaller than a sample dependent threshold Ra;{*} we observe transient oscillatory convection. Unexpectedly, the duration of convection diverges at Ra;{*}. Above Ra;{*} oscillatory convection becomes permanent and the heat transferred exhibits bistability. Our results are explained only partially and qualitatively by existing theories.

  6. 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.

  7. 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.

  8. Heat Transfer Characteristics in Crank-Shape Thermosyphons

    NASA Astrophysics Data System (ADS)

    Imura, Hedeaki; Koito, Yasushi

    A two-phase closed thermosyphon is applied to gas-to-gas heat exchangers, the cooling of heat generation devices, the melting of snow, the prevention from icing of water on roads and so on. Generally, straight tubes are used as the thermosyphon. However, because of the limited space for the straight thermosyphon to be installed, it is considered that a bent thermosyphon is enforced to employ. In response to this, fundamental experiments are conducted on the heat transfer characteristics in a two-phase crank shape closed thermosyphon, in which an evaporator and a condenser are vertically positioned, and a connecting adiabatic section is horizontal. Ethylene glycol aqueous solutions which have lower freezing points and hydrofluoroether 7100 and 7200 which do not contain chloride are used as the working fluids Heat transfer coefficients and critical heat fluxes in the thermosyphon are measured by changing the amount of charged working fluid (0.30,0.40,0.50 and 0.60 of the evaporator volume),the temperature of the adiabatic section (40,50,60,70 and 80°C) and heat flux (from 4.0 kW /m2 to critical). The experimental results are shown and compared with those taken using water as the working fluid.

  9. Modeling of Heat and Mass Transfer in Fusion Welding

    SciTech Connect

    Zhang, Wei

    2011-01-01

    In fusion welding, parts are joined together by melting and subsequent solidification. Although this principle is simple, complex transport phenomena take place during fusion welding, and they determine the final weld quality and performance. The heat and mass transfer in the weld pool directly affect the size and shape of the pool, the solidification microstructure, the formation of weld defects such as porosity and humping, and the temperature distribution in the fusion zone and heat-affected zone (HAZ). Furthermore, the temperature evolution affects the kinetics and extent of various solid-state phase transformations, which in turn determine the final weld microstructure and mechanical properties. The formation of residual stresses and distortion originates from the thermal expansion and contraction during welding heating and cooling, respectively.

  10. Laboratory simulation of heat exchange for liquids with Pr > 1: Heat transfer

    NASA Astrophysics Data System (ADS)

    Belyaev, I. A.; Zakharova, O. D.; Krasnoshchekova, T. E.; Sviridov, V. G.; Sukomel, L. A.

    2016-02-01

    Liquid metals are promising heat transfer agents in new-generation nuclear power plants, such as fast-neutron reactors and hybrid tokamaks—fusion neutron sources (FNSs). We have been investigating hydrodynamics and heat exchange of liquid metals for many years, trying to reproduce the conditions close to those in fast reactors and fusion neutron sources. In the latter case, the liquid metal flow takes place in a strong magnetic field and strong thermal loads resulting in development of thermogravitational convection in the flow. In this case, quite dangerous regimes of magnetohydrodynamic (MHD) heat exchange not known earlier may occur that, in combination with other long-known regimes, for example, the growth of hydraulic drag in a strong magnetic field, make the possibility of creating a reliable FNS cooling system with a liquid metal heat carrier problematic. There exists a reasonable alternative to liquid metals in FNS, molten salts, namely, the melt of lithium and beryllium fluorides (Flibe) and the melt of fluorides of alkali metals (Flinak). Molten salts, however, are poorly studied media, and their application requires detailed scientific substantiation. We analyze the modern state of the art of studies in this field. Our contribution is to answer the following question: whether above-mentioned extremely dangerous regimes of MHD heat exchange detected in liquid metals can exist in molten salts. Experiments and numerical simulation were performed in order to answer this question. The experimental test facility represents a water circuit, since water (or water with additions for increasing its electrical conduction) is a convenient medium for laboratory simulation of salt heat exchange in FNS conditions. Local heat transfer coefficients along the heated tube, three-dimensional (along the length and in the cross section, including the viscous sublayer) fields of averaged temperature and temperature pulsations are studied. The probe method for measurements in

  11. Enhancement of heat transfer rate on phase change materials with thermocapillary flows

    NASA Astrophysics Data System (ADS)

    Madruga, Santiago; Mendoza, Carolina

    2016-07-01

    We carry out simulations of the melting process on the phase change material n-octadecane in squared geometries in the presence of natural convection and including thermocapillary effects. We show how the introduction of thermocapillary effects enhances the heat transfer rate, being the effect especially relevant for small Bond numbers. Thus induction of Marangoni flows results in a useful mechanism to enhance the typical slow heat transfer rate of paraffin waxes in applications of energy storage or passive control management.

  12. Enhancement of heat transfer rate on phase change materials with thermocapillary flows

    NASA Astrophysics Data System (ADS)

    Madruga, Santiago; Mendoza, Carolina

    2017-04-01

    We carry out simulations of the melting process on the phase change material n-octadecane in squared geometries in the presence of natural convection and including thermocapillary effects. We show how the introduction of thermocapillary effects enhances the heat transfer rate, being the effect especially relevant for small Bond numbers. Thus induction of Marangoni flows results in a useful mechanism to enhance the typical slow heat transfer rate of paraffin waxes in applications of energy storage or passive control management.

  13. Thermophysical and heat transfer properties of phase change material candidate for waste heat transportation system

    NASA Astrophysics Data System (ADS)

    Kaizawa, Akihide; Maruoka, Nobuhiro; Kawai, Atsushi; Kamano, Hiroomi; Jozuka, Tetsuji; Senda, Takeshi; Akiyama, Tomohiro

    2008-05-01

    A waste heat transportation system trans-heat (TH) system is quite attractive that uses the latent heat of a phase change material (PCM). The purpose of this paper is to study the thermophysical properties of various sugars and sodium acetate trihydrate (SAT) as PCMs for a practical TH system and the heat transfer property between PCM selected and heat transfer oil, by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA) and a heat storage tube. As a result, erythritol, with a large latent heat of 344 kJ/kg at melting point of 117°C, high decomposition point of 160°C and excellent chemical stability under repeated phase change cycles was found to be the best PCM among them for the practical TH system. In the heat release experiments between liquid erythritol and flowing cold oil, we observed foaming phenomena of encapsulated oil, in which oil droplet was coated by solidification of PCM.

  14. The Principles of Turbulent Heat Transfer

    NASA Technical Reports Server (NTRS)

    Reichardt, H.

    1957-01-01

    The literature on turbulent heat transfer has in the course of years attained a considerable volume. Since this very complicated problem has not as yet found a complete solution, further studies in this field may be expected. The heat engineer must therefore accomodate himself to a constantly increasing number of theories and formulas. Since the theories generally start from hypothetical assumptions, and since they contain true and false assertions, verified knowledge and pure suppositions often being intermingled in a manner difficult to tell them apart, the specialist had difficulty in forming a correct evaluation of the individual studies. The need therefore arises for a presentation of the problem of turbulent heat transfer which is not initially bound by hypothetical assumptions and in which uninvestigated can be clearly distinguished form each other. Such a presentation will be given in the present treatment. Brief remarks with regard to the development of the theory of local heat transfer are included.

  15. Indirect evaporative coolers with enhanced heat transfer

    DOEpatents

    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.

  16. Heat transfer in rocket combustion chambers

    NASA Technical Reports Server (NTRS)

    Anderson, P.; Cheng, G.; Farmer, R.

    1993-01-01

    Complexities of liquid rocket engine heat transfer which involve the injector faceplate and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis was used to describe localized heating phenomena associated with particular injector configurations and film coolant flows. These components were analyzed, and the analyses verified when appropriate test data were available. The component analyses are being synthesized into an overall flowfield/heat transfer model. A Navier-Stokes flow solver, the FDNS code, was used to make the analyses. Particular attention was given to the representation of the thermodynamic properties of the fluid streams. Unit flow models of specific coaxial injector elements have been developed and are being used to describe the flame structure near the injector faceplate.

  17. 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.

  18. Modeling microscale heat transfer using Calore.

    SciTech Connect

    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.

  19. 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

  20. Ice melting properties of steel fiber modified asphalt mixtures with induction heating

    NASA Astrophysics Data System (ADS)

    Fang, Hao; Sun, Yihan; Liu, Quantao; Li, Bin; Wu, Shaopeng; Tang, Jin

    2017-03-01

    In this paper, the ice melting performance of asphalt concrete with steel fibers was studied. Steel fiber modified asphalt mixtures were prepared, five different fiber amount of steel fiber modified asphalt mixtures were mixed to study their induction heating rate. The samples covered with different thickness of ice were heated with induction heating to study their ice melting efficency. It was proved that the induction heating of steel fiber modified asphalt mixtures could significantly improve their ice melting efficency compared with the natural condition. And it was found that the thickness of the ice had little influence on the induction heating rate of the asphalt concrete.

  1. Characteristics of Transient Boiling Heat Transfer

    SciTech Connect

    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)

  2. Heat transfer in suspensions of rigid particles

    NASA Astrophysics Data System (ADS)

    Brandt, Luca; Niazi Ardekani, Mehdi; Abouali, Omid

    2016-11-01

    We study the heat transfer in laminar Couette flow of suspensions of rigid neutrally buoyant particles by means of numerical simulations. An Immersed Boundary Method is coupled with a VOF approach to simulate the heat transfer in the fluid and solid phase, enabling us to fully resolve the heat diffusion. First, we consider spherical particles and show that the proposed algorithm is able to reproduce the correlations between heat flux across the channel, the particle volume fraction and the heat diffusivity obtained in laboratory experiments and recently proposed in the literature, results valid in the limit of vanishing inertia. We then investigate the role of inertia on the heat transfer and show an increase of the suspension diffusivity at finite particle Reynolds numbers. Finally, we vary the relativity diffusivity of the fluid and solid phase and investigate its effect on the effective heat flux across the channel. The data are analyzed by considering the ensemble averaged energy equation and decomposing the heat flux in 4 different contributions, related to diffusion in the solid and fluid phase, and the correlations between wall-normal velocity and temperature fluctuations. Results for non-spherical particles will be examined before the meeting. Supported by the European Research Council Grant No. ERC-2013- CoG-616186, TRITOS. The authors acknowledge computer time provided by SNIC (Swedish National Infrastructure for Computing).

  3. Calorimetric measurements of energy transfer efficiency and melting efficiency in CO sub 2 laser beam welding

    SciTech Connect

    Fuerschbach, P.W.

    1990-01-01

    Our previous calorimetric studies of weld melting efficiency and arc efficiency in the GTAW and PAW processes have naturally led us to speculate as to the magnitude of the efficiencies in the LBW process which to data have also not been adequately investigated. Most welding engineers that have had experience with the LBW process are acutely aware that the metals' absorptivity, the surface finish, and the laser wavelength, all play an important role in affecting the energy transfer efficiency, but the extent of their influence and our understanding of the influence of other process variables is not well understood. In addition, it is widely thought that only the LBW or EBW processes can be selected for applications where thermal damage and distortion from the welding process must be kept to a minimum. For these reasons, we have looked forward to performing these calorimetric experiments since they potentially can answer such important questions as: whether or not the melting efficiency of the LBW process is superior to that obtainable with conventional GTAW and PAW welding processes This study was prompted by poor production yields on switching device due to cracking of the ceramic header after final closure welding with the CO{sub 2} LBW process. This calorimetric study was begun in hopes of determining if allowed variations in production process control variables were responsible for increases in heat input and the resulting thermal stresses. By measuring the net heat input to the workpiece with the calorimeter and by measuring the laser output energy and the weld fusion zone size it was possible to determine the magnitudes of both the energy transfer efficiency and the melting efficiency as well as observe their dependence on the process variables. 3 refs.

  4. Post-dryout heat transfer in sodium-cooled fast reactors

    SciTech Connect

    Cheung, F.B.; Pedersen, D.R.

    1982-01-01

    The heat-transfer behavior of a heat-generating, dry, particulate bed resulting from a postulated core meltdown accident in sodium-cooled fast reactors is investigated theoretically. The processes of combined conduction and thermal radiation in the dry particulate bed and transient heat conduction in the structure in contact with the bed are modeled. Also modeled is the contribution of direct gamma-ray radiation to heat transfer. Results for the transient temperature distribution of the system are obtained by the method of successive approximation. Various post-dryout situations are considered and the conditions leading either to an incipient melting system or to a coolable non-melting system are identified. These are found to depend on four groups of dimensionless parameters, namely, the thermal property group, the radiation and internal heating group, the gamma-ray heating group, and the external cooling group.

  5. Heat transfer in pressurized circulating fluidized beds

    SciTech Connect

    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

  6. Deep Eutectic Salt Formulations Suitable as Advanced Heat Transfer Fluids

    SciTech Connect

    Raade, Justin; Roark, Thomas; Vaughn, John; Bradshaw, Robert

    2013-07-22

    Concentrating solar power (CSP) facilities are comprised of many miles of fluid-filled pipes arranged in large grids with reflective mirrors used to capture radiation from the sun. Solar radiation heats the fluid which is used to produce steam necessary to power large electricity generation turbines. Currently, organic, oil-based fluid in the pipes has a maximum temperature threshold of 400 °C, allowing for the production of electricity at approximately 15 cents per kilowatt hour. The DOE hopes to foster the development of an advanced heat transfer fluid that can operate within higher temperature ranges. The new heat transfer fluid, when used with other advanced technologies, could significantly decrease solar electricity cost. Lower costs would make solar thermal electricity competitive with gas and coal and would offer a clean, renewable source of energy. Molten salts exhibit many desirable heat transfer qualities within the range of the project objectives. Halotechnics developed advanced heat transfer fluids (HTFs) for application in solar thermal power generation. This project focused on complex mixtures of inorganic salts that exhibited a high thermal stability, a low melting point, and other favorable characteristics. A high-throughput combinatorial research and development program was conducted in order to achieve the project objective. Over 19,000 candidate formulations were screened. The workflow developed to screen various chemical systems to discover salt formulations led to mixtures suitable for use as HTFs in both parabolic trough and heliostat CSP plants. Furthermore, salt mixtures which will not interfere with fertilizer based nitrates were discovered. In addition for use in CSP, the discovered salt mixtures can be applied to electricity storage, heat treatment of alloys and other industrial processes.

  7. Gas-side heat transfer with rotation

    NASA Technical Reports Server (NTRS)

    Dring, R. P.

    1983-01-01

    The primary basis for heat transfer analysis of turbine blades is experimental data obtained in linear cascades. These data have been very valuable in identifying the major heat transfer and fluid flow features of a turbine airfoil. The question of major interest is how well all of these data translate to the rotating turbine blade. It is known from the work of Lokay and Trushin that average heat transfer coefficients on the rotor may be as much as 40 percent above the values measured on the same blades nonrotating. Recent work by Dunn and Holt supports the Russian conclusion. What is lacking is a set of data from a rotating system which is of sufficient detail as to make careful local comparisons between static system in which there is sufficient documentation of the flow field to support the computer analyses being developed today. A second major question is the influence, if any, of the first stator row on the heat transfer of the second stator row after the flow has passed through the rotor. An objective of the present program, is to obtain a detailed set of heat transfer coefficients along the midspan of a blade in a rotating turbine.

  8. Dissociation heat transfer characteristics of methane hydrates

    SciTech Connect

    Kamath, V.A.; Holder, G.D.

    1987-02-01

    Knowledge of the interfacial heat transfer phenomenon during the dissociation of gas hydrates is essential in modeling the hydrate dissociation process. Such knowledge has applications in natural gas processing, storage, or transportation; in the drilling and recovery of oil and gas in the presence of gas hydrates; in the desalination of sea water; and in the production of natural gas from hydrate reservoirs. The process of hydrate dissociation is a unique phenomenon in which gas and water are simultaneously produced at the dissociated hydrate surface and play an important role in the mechanism of heat transfer to hydrates. An earlier study of propane hydrate dissociation showed that hydrate dissociation is a heat-transfer-limited process and somewhat similar to the nucleate boiling of liquids. In the present study, heat transfer limitations for methane hydrate dissociation were studied for two reasons. First, a comparison of the results of this study with propane hydrate was desired. Second, the effect of hydrate structure and gas molecule type on the rate of heat transfer during hydrate dissociation was sought.

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

    DOEpatents

    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.

  10. Ties of Heat and Mass Transport Properties in Glasses and Melts, with Emphasis on Natural Lava Compositions

    NASA Astrophysics Data System (ADS)

    Hofmeister, A. M.; Whittington, A. G.; Robert, G.; Sehlke, A.

    2016-12-01

    We have discovered strong ties of mass and heat transport properties in glasses and melts via coordinated measurements of thermal diffusivity (D) and viscosity (η). Over the course of several studies we have compared over 50 remelted natural lavas, tektites, and synthetic glasses and melts, with substantially different chemical compositions, e.g., from 50 to 100% silica, and with slight variations in H and Fe cations and the presence/absence of Al. We use laser flash analysis to obtain D, which avoids contact and radiative errors and constrain η over a wide range of temperature (T). We use a combination of parallel-plate and concentric-cylinder viscometry to obtain η from the glass transition to above the liquidus. Our most recent studies include differential scanning calorimetric measurements of heat capacity (CP) to calculate their thermal conductivity (k), and we are now measuring thermal expansivity using dilatometry. The combined datasets show consistent macroscopic behavior, providing an improved understanding of microscopic behavior, particularly of heat transport properties, which have been misunderstood. Both viscosity and the glass transition temperature decrease with decreasing melt polymerization. Clear correlations exist between D of glass or melt with Si content, density, NBO/T, and, most strongly, with fragility (obtained from η). Glass thermal diffusivity is represented by D = FT-G +HT, where F, G and H are fitting parameters. For melts, D drops upon melting but we could only resolve D/T for a small number of samples. The results show that high-T behavior is controlled by Fe oxidation state and polymerization and involves radiative transfer (HT) but at infrared frequencies. In disordered materials, acoustic scattering is less important to heat transfer than is IR absorption/re-emissions. We find that k for glasses is described by a Maier-Kelly formula, consistent with the T response being dominated by CP. Trends in k are irregular due to k being

  11. Heat transfer in vertical Bridgman growth of oxides - Effects of conduction, convection, and internal radiation

    NASA Technical Reports Server (NTRS)

    Brandon, S.; Derby, J. J.

    1992-01-01

    In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.

  12. Heat transfer enhancement for thermal energy storage using metal foams embedded within phase change materials (PCMs)

    SciTech Connect

    Zhao, C.Y.; Lu, W.; Tian, Y.

    2010-08-15

    In this paper the experimental investigation on the solid/liquid phase change (melting and solidification) processes have been carried out. Paraffin wax RT58 is used as phase change material (PCM), in which metal foams are embedded to enhance the heat transfer. During the melting process, the test samples are electrically heated on the bottom surface with a constant heat flux. The PCM with metal foams has been heated from the solid state to the pure liquid phase. The temperature differences between the heated wall and PCM have been analysed to examine the effects of heat flux and metal foam structure (pore size and relative density). Compared to the results of the pure PCM sample, the effect of metal foam on solid/liquid phase change heat transfer is very significant, particularly at the solid zone of PCMs. When the PCM starts melting, natural convection can improve the heat transfer performance, thereby reducing the temperature difference between the wall and PCM. The addition of metal foam can increase the overall heat transfer rate by 3-10 times (depending on the metal foam structures and materials) during the melting process (two-phase zone) and the pure liquid zone. The tests for investigating the solidification process under different cooling conditions (e.g. natural convection and forced convection) have been carried out. The results show that the use of metal foams can make the sample solidified much faster than pure PCM samples, evidenced by the solidification time being reduced by more than half. In addition, a two-dimensional numerical analysis has been carried out for heat transfer enhancement in PCMs by using metal foams, and the prediction results agree reasonably well with the experimental data. (author)

  13. Electromagnetic Heat Transfer in Artificial Materials

    NASA Astrophysics Data System (ADS)

    Woods, Lilia; Drosdoff, David; Phan, Anh

    2014-03-01

    Electromagnetic energy exchange has found promising new opportunities by greatly enhancing the heat transfer between bodies via radiation in the near-field regime. The greatest heat transfer occurs when the bodies support surface plasmons or polaritons that share the same resonant frequency. It has been shown, however, that 2-D materials such as graphene can have their surface plasmons tuned by modifying the chemical potential and temperature. This allows for tuning its resonance with other systems. In this talk, we investigated the electromagnetic radiation in metamaterials characterized by a strong magnetic response. We study theoretically Pendry-like and magnetically active metamaterial/graphene composites. The possibility for enhancing or inhibiting the heat transfer via the graphene properties is investigated.

  14. Condensation heat transfer under a microgravity environment

    NASA Technical Reports Server (NTRS)

    Chow, L. C.

    1986-01-01

    A description of the condensation heat transfer process in microgravity is given. A review of the literature is also reported. The most essential element of condensation heat transfer in microgravity is the condensate removal mechanism. Two mechanisms for condensate removal are analyzed by looking into two problems. The first problem is concerned with film condensation on a flat porous plate with the condensate being removed by suction at the wall. The second problem is an analytical prediction of the heat transfer coefficient for condensing annular flows with the condensate film driven by the vapor shear. It is concluded that both suction and vapor shear can effectively drain the condensate to ensure continuous operation of the condensers operated under a microgravity environment. It is recommended that zero-g flight experiments be carried out to verify the prediction made in the present report. The results contained in this report should also aid in the design of future space condensers.

  15. Radiant heat transfer between nongray directional surfaces.

    NASA Technical Reports Server (NTRS)

    Fischer, W. D.; Hering, R. G.

    1972-01-01

    Real surface property effects on local and overall heat transfer are studied for a simple system of interacting opaque surfaces. Wavelength, temperature and directional dependence of surface properties is included in the analysis for equal and unequal temperature specularly reflecting surfaces. Tungsten is employed as a representative metal and Roberts' model is used to describe the wavelength and temperature dependence of its optical parameters. The relationships of electromagnetic theory are employed to describe the directional dependence of spectral properties. Numerical results establish that gray direction independent property analysis adequately predicts the general trends of real surface analysis. The results also establish that spectral and temperature dependence of surface properties influences radiant heat transfer to a greater degree than does directional dependence of properties. Property models which adequately account for the nongray character of engineering surfaces while neglecting directional dependence of properties can provide heat transfer results of acceptable engineering accuracy.

  16. Evaporative heat transfer in beds of sensible heat pellets

    SciTech Connect

    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.

  17. 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.

  18. Heat Transfer Measurements of Internally Finned Rotating Heat Pipes.

    DTIC Science & Technology

    1983-12-01

    Noncondensable Gases, Rotating Heat Pipe , Performance, Helical and Straight Pin, Internal Heat Transfer Coefficient. AS"RACY (40115111111141 WH ide of* 0686...improvement over the smooth condenser. By helically finning the tube wall in addition to increasing the internal area, the counter-clockwise spiral ... spirally -finned condenser then on the straight-finned condenser. Apparently, during fabrication of the helically -finned condenser, a series of

  19. 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.

  20. Coolant passage heat transfer with rotation

    NASA Technical Reports Server (NTRS)

    Hajek, T. J.; Wagner, J.; Johnson, B. V.

    1986-01-01

    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.

  1. Transfer of radiative heat through clothing ensembles.

    PubMed

    Lotens, W A; Pieters, A M

    1995-06-01

    A mathematical model was designed to calculate the temperature and dry heat transfer in the various layers of a clothing ensemble, and the total heat loss of a human who is irradiated for a certain fraction of his or her area. The clothing ensemble that is irradiated by an external heat source is considered to be composed of underclothing, trapped air, and outer fabric. The model was experimentally tested with heat balance methods, using subjects, varying the activity, wind, and radiation characteristics of the outer garment of two-layer ensembles. In two experiments the subjects could only give off dry heat because they were wrapped in plastic foil. The model appeared to be correct within about 1 degree C (rms error) and 10 Wm-2 (rms error). In a third experiment, sweat evaporation was also taken into account, showing that the resulting physiological heat load of 10 to 30% of the intercepted additional radiation is compensated by additional sweating. The resulting heat strain was rather mild. It is concluded that the mathematical model is a valid tool for the investigation of heat transfer through two-layer ensembles in radiant environments.

  2. Low-temperature heat transfer in nanowires.

    PubMed

    Glavin, B A

    2001-05-07

    A new regime of low-temperature heat transfer in suspended nanowires is predicted. It takes place when (i) only "acoustic" phonon modes of the wire are thermally populated and (ii) phonons are subject to the effective elastic scattering. Qualitatively, the main peculiarities of heat transfer originate due to the appearance of the flexural modes with high density of states in the wire phonon spectrum. They give rise to the T(1/2) temperature dependence of the wire thermal conductance. Experimental situations where the new regime is likely to be detected are discussed.

  3. Convective heat transfer during dendritic growth

    NASA Technical Reports Server (NTRS)

    Glicksman, M. E.; Huang, S. C.

    1979-01-01

    Axial growth rate measurements were carried out at 17 levels of supercooling between 0.043 C and 2 C, a temperature range in which convection, instead of diffusion, becomes the controlling mechanism of heat transfer in the dentritic growth process. The growth velocity, normalized to that expected for pure diffusive heat transfer, displays a dependence on orientation. The ratio of the observed growth velocity to that for convection-free growth and the coefficients of supercooling are formulated. The dependence of normalized growth rate in supercooling is described for downward growing dendrites. These experimental correlations can be justified theoretically only to a limited extent.

  4. Splice connector with internal heat transfer jacket

    DOEpatents

    Silva, Frank A.; Mayer, Robert W.

    1977-01-01

    A heat transfer jacket is placed over the terminal portions of the conductors of a pair of high voltage cables which are connected in a splice connection wherein a housing surrounds the connected conductor portions, the heat transfer jacket extending longitudinally between the confronting ends of a pair of adaptor sleeves placed upon the insulation of the cables to engage and locate the adaptor sleeves relative to one another, and laterally between the conductors and the housing to provide a path of relatively high thermal conductivity between the connected conductor portions and the housing.

  5. 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.

  6. 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.

  7. Heat transfer during quenching of gases

    NASA Astrophysics Data System (ADS)

    Ambraziavichius, A.

    Results of theoretical and experimental investigations of gas-side heat transfer of subsonic laminar or turbulent flows of diatomic gases (air or nitrogen) heated to 5000 K in cold-wall pipes are presented. While determining the mixing length, physical parameters which consider local temperatures of the boundary layer were adopted. Thus, the generalized fields of velocities and temperatures in the turbulent region of the boundary layer are identical for both moderate and high gas temperature ranges, and Pr-sub-t may be considered constant and approximately equal to 0.9. The temperature level of gases in turblent flow is shown to insignificantly affect heat transfer equations, provided the physical parameters in the similarity numbers are chosen according to the bulk flow temperature. A calculation technique is developed for heat transfer of dissociated diatomic gases in annular and rectangular channels, in slots, and over bundles of square tubes in cross flow. Also, a relation is shown between the heat transfer coefficient, quenching velocity, and nitrogen oxide concentration in the air exhaust of a nitrogen oxide quenching apparatus.

  8. Microscale surface modifications for heat transfer enhancement.

    PubMed

    Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C

    2013-10-09

    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.

  9. Natural convective heat transfer from square cylinder

    SciTech Connect

    Novomestský, Marcel Smatanová, Helena Kapjor, Andrej

    2016-06-30

    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.

  10. 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.

  11. Heat Transfer and Cooling in Gas Turbines

    DTIC Science & Technology

    1985-09-01

    pillar -like protrusions. .1-2 The accurate determination of ILet transfer coefficient distributions in these blade passages is vital at the design...verification. The fin analysis had indirectly assumed absence of any contact resistance between the copper endwall and the wood pins, woich could be...thin layer of epoxy (-.005-.006 cm) between the copper pin and the endwalls of less than 1% of the heat transfer surface temperature. The resulting

  12. Self supporting heat transfer element

    DOEpatents

    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.

  13. Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer

    PubMed Central

    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

  14. Heat flux sensors for infrared thermography in convective heat transfer.

    PubMed

    Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso

    2014-11-07

    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.

  15. Effect of inclined magnetic field on natural convection melting in a square cavity with a local heat source

    NASA Astrophysics Data System (ADS)

    Bondareva, Nadezhda S.; Sheremet, Mikhail A.

    2016-12-01

    MHD natural convection melting in a square cavity with a local heater has been analyzed numerically. The domain of interest is an enclosure bounded by isothermal vertical walls of low constant temperature and adiabatic horizontal walls. A heat source of constant temperature is located on the bottom wall. An inclined uniform magnetic field affects the natural convective heat transfer and fluid flow inside the melt. The governing equations formulated in dimensionless stream function, vorticity and temperature with corresponding initial and boundary conditions have been solved using implicit finite difference method of the second-order accuracy. The effects of the Rayleigh number, Stefan number, Hartmann number, magnetic field inclination angle and dimensionless time on streamlines, isotherms and Nusselt number at the heat source surface have been analyzed.

  16. Characterization of Heat Melt Compactor (HMC) Product Water

    NASA Technical Reports Server (NTRS)

    Harris, Linden; Wignarajah, Kanapathipi; Alba, Richard Gilbert; Pace, Gregory S.; Fisher, John W.

    2013-01-01

    The Heat Melt Compactor (HMC) is designed to sterilize and process wastes produced during space missions. Benefits of the HMC include reduction of biohazards to the crew, reduction in volume of wastes that would otherwise require storage, production of radiation shielding tiles, and recovery of water and other resources. Water reuse is critical onboard spacecrafts; it reduces the need for resupply missions and saves valuable storage space. The main sources of water in HMC batches are food, beverages, shampoo, disinfecting wipes, toothpaste, and diapers. Water reclaimed by the HMC was analyzed for concentrations of Na+, NH4+, K+, Mg2+, Ca2+, Cl-­-, NO2-­-, Br-­-, NO3-­-, PO43-­-, SO42-­-, total organic carbon (TOC), total inorganic carbon (TIC), % total solids, and pH. The data are discussed in relation to the current water input characteristics established for the International Space Station Water Processor Assembly system. Batches with higher than average amounts of food produced HMC product water with higher sulfate content, and batches with higher proportions of disinfectant wipes and food yielded HMC product water with higher ammonium concentration. We also compared theoretical chemical composition of HMC product water based on food labels and literature values to experimental results.

  17. Cooperative heat transfer and ground coupled storage system

    DOEpatents

    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.

  18. Cooperative heat transfer and ground coupled storage system

    DOEpatents

    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.

  19. Numerical modeling of heat transfer in molten silicon during directional solidification process

    SciTech Connect

    Srinivasan, M.; Ramasamy, P.

    2015-06-24

    Numerical investigation is performed for some of the thermal and fluid flow properties of silicon melt during directional solidification by numerical modeling. Dimensionless numbers are extremely useful to understand the heat and mass transfer of fluid flow on Si melt and control the flow patterns during crystal growth processes. The average grain size of whole crystal would increase when the melt flow is laminar. In the silicon growth process, the melt flow is mainly driven by the buoyancy force resulting from the horizontal temperature gradient. The thermal and flow pattern influences the quality of the crystal through the convective heat and mass transport. The computations are carried out in a 2D axisymmetric model using the finite-element technique. The buoyancy effect is observed in the melt domain for a constant Rayleigh number and for different Prandtl numbers. The convective heat flux and Reynolds numbers are studied in the five parallel horizontal cross section of melt silicon region. And also, velocity field is simulated for whole melt domain with limited thermal boundaries. The results indicate that buoyancy forces have a dramatic effect on the most of melt region except central part.

  20. Heat transfer characteristics of d-mannitol as a phase change material for a medium thermal energy system

    NASA Astrophysics Data System (ADS)

    Shibahara, Makoto; Liu, Qiusheng; Fukuda, Katsuya

    2016-09-01

    Melting process and heat transfer characteristics of d-mannitol were investigated experimentally and numerically to construct a fundamental database of the waste heat recovery systems for ships. d-Mannitol which has relatively high latent heat was selected in this study as a phase-change material for medium thermal energy storage. Experimental results indicate that the melting temperature and latent heat of d-mannitol were affected by the heating rate. The weight of d-mannitol did not decrease with the increase in temperature between 436 and 455 K. Moreover, numerical simulation was conducted using the commercial CFD code, ANSYS FLUENT. On the basis of the numerical simulation, melting process was affected by natural convection at the inner wall. As the heat flux of the cartridge heater input came from the inner wall, the liquid fraction increased from the inner wall to the outer wall through natural convection. The numerical result was compared with the experimental data. The temperature of the numerical simulation was approximately consistent with the experimental data. Moreover, the local heat transfer coefficients at the heater surface were calculated by the result of the numerical simulation. The heat transfer coefficients decreased during the phase change. It was considered that the heat transfer process changed from conductive heat transfer of solid state to natural convection heat transfer of liquid state as the liquid fraction increased with time.

  1. Optimization of the heating surface shape in the contact melting problem

    NASA Technical Reports Server (NTRS)

    Fomin, Sergei A.; Cheng, Shangmo

    1991-01-01

    The theoretical analysis of contact melting by the migrating heat source with an arbitrary shaped isothermal heating surface is presented. After the substantiated simplification, the governing equations are transformed to the convenient equations for engineering calculations relationships. Analytical solutions are used for numerical prediction of optimal shape of the heating surface. The problem is investigated for the constant and for temperature dependent physical properties of the melt.

  2. Heating and melting of small icy satellites by the decay of Al-26

    NASA Technical Reports Server (NTRS)

    Prialnik, Dina; Bar-Nun, Akiva

    1990-01-01

    The effect of radiogenic heating due to Al-26 on the thermal evolution of small icy satellites is studied. The object is to find the extent of internal melting as a function of the satellite radius and of the initial Al-26 abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of about 10 to the 6th yr (comparable with the lifetime of Al-26. The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of K-40, Th-232, U-235, and U-238, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10 to the 9th yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. The main conclusion is that the initial Al-26 abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, about 7 x 10 to the -7th by mass).

  3. Heating and melting of small icy satellites by the decay of Al-26

    NASA Technical Reports Server (NTRS)

    Prialnik, Dina; Bar-Nun, Akiva

    1990-01-01

    The effect of radiogenic heating due to Al-26 on the thermal evolution of small icy satellites is studied. The object is to find the extent of internal melting as a function of the satellite radius and of the initial Al-26 abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of about 10 to the 6th yr (comparable with the lifetime of Al-26. The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of K-40, Th-232, U-235, and U-238, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10 to the 9th yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. The main conclusion is that the initial Al-26 abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, about 7 x 10 to the -7th by mass).

  4. Heating and melting of small icy satellites by the decay of Al-26

    NASA Astrophysics Data System (ADS)

    Prialnik, Dina; Bar-Nun, Akiva

    1990-05-01

    The effect of radiogenic heating due to Al-26 on the thermal evolution of small icy satellites is studied. The object is to find the extent of internal melting as a function of the satellite radius and of the initial Al-26 abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of about 10 to the 6th yr (comparable with the lifetime of Al-26. The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of K-40, Th-232, U-235, and U-238, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10 to the 9th yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. The main conclusion is that the initial Al-26 abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, about 7 x 10 to the -7th by mass).

  5. Heating and melting of small icy satellites by the decay of Al-26

    SciTech Connect

    Prialnik, D.; Bar-Nun, A. )

    1990-05-01

    The effect of radiogenic heating due to Al-26 on the thermal evolution of small icy satellites is studied. The object is to find the extent of internal melting as a function of the satellite radius and of the initial Al-26 abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of about 10 to the 6th yr (comparable with the lifetime of Al-26). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of K-40, Th-232, U-235, and U-238, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10 to the 9th yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. The main conclusion is that the initial Al-26 abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, about 7 x 10 to the -7th by mass). 34 refs.

  6. Heat transfer variations of bicycle helmets.

    PubMed

    Brühwiler, P A; Buyan, M; Huber, R; Bogerd, C P; Sznitman, J; Graf, S F; Rösgen, T

    2006-09-01

    Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets.

  7. 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…

  8. 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.

  9. 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.

  10. 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…

  11. FED. Zoning for TRUMP Heat Transfer Code

    SciTech Connect

    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.

  12. Turbine airfoil gas side heat transfer

    NASA Technical Reports Server (NTRS)

    Turner, E. R.

    1984-01-01

    Work is currently underway to develop and characterize an analytical approach, based on boundary layer theory, for predicting the effects of leading edge (showerhead) film cooling on downstream gas side heat transfer rates. Parallel to this work, experiments are being conducted to build a relevant data base for present and future methods verification.

  13. 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).

  14. Boiling heat transfer characteristics of liquid xenon

    NASA Astrophysics Data System (ADS)

    Haruyama, T.

    2002-05-01

    Liquid xenon is one of the excellent media for high-energy particle calorimeter. In order to detect a scintillation light effectively, a large number of photo-multipliers (PMTs) will be immersed in liquid xenon. Many chip-resistors equipped with the PMTs dissipate heat into liquid and possibly generate thermal turbulence, such as bubbles, convection flow under a certain operating condition. There is, however, no heat transfer curve (q-ΔT curve) in the literature. Boiling heat transfer characteristics of liquid xenon were measured at a saturated pressure of 0.1 MPa for the first time by using a small pulse tube refrigerator. The heat transfer surface is a thin platinum wire of 0.1 mm diameter and 25 mm long. The measured results were in good agreement with the calculated values both in natural convection and nucleate boiling condition. The film boiling state was difficult to obtain due to its poor reproducibility, and only one data was obtained. The relationship between the heat flux q and temperature difference ΔT was in good agreement with the Morgan's empirical equation in the natural convection region, and with the Kutateladze's equation in the nucleate boiling region.

  15. Advanced Heat Transfer and Thermal Storage Fluids

    SciTech Connect

    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.

  16. Heat transfer in a real engine environment

    NASA Astrophysics Data System (ADS)

    Gladden, Herbert J.

    1985-10-01

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

  17. Heat transfer in a real engine environment

    NASA Technical Reports Server (NTRS)

    Gladden, Herbert J.

    1985-01-01

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

  18. 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.

  19. Heat transfer in bioengineering and medicine

    SciTech Connect

    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.

  20. Numerical study of heat transfer characteristics in BOG heat exchanger

    NASA Astrophysics Data System (ADS)

    Yan, Yan; Pfotenhauer, John M.; Miller, Franklin; Ni, Zhonghua; Zhi, Xiaoqin

    2016-12-01

    In this study, a numerical study of turbulent flow and the heat transfer process in a boil-off liquefied natural gas (BOG) heat exchanger was performed. Finite volume computational fluid dynamics and the k - ω based shear stress transport model were applied to simulate thermal flow of BOG and ethylene glycol in a full-sized 3D tubular heat exchanger. The simulation model has been validated and compared with the engineering specification data from its supplier. In order to investigate thermal characteristics of the heat exchanger, velocity, temperature, heat flux and thermal response were studied under different mass flowrates in the shell-side. The shell-side flow pattern is mostly determined by viscous forces, which lead to a small velocity and low temperature buffer area in the bottom-right corner of the heat exchanger. Changing the shell-side mass flowrate could result in different distributions of the shell-side flow. However, the distribution in the BOG will remain in a relatively stable pattern. Heat flux increases along with the shell-side mass flowrate, but the increase is not linear. The ratio of increased heat flux to the mass flow interval is superior at lower mass flow conditions, and the threshold mass flow for stable working conditions is defined as greater than 0.41 kg/s.

  1. 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.

  2. Quasi-stationary phase change heat transfer on a fin

    NASA Astrophysics Data System (ADS)

    Orzechowski, Tadeusz; Stokowiec, Katarzyna

    2016-03-01

    The paper presents heat transfer research basing on a long fin with a circular cross-section. Its basis is welded to the pipe where the hot liquid paraffin, having a temperature of 70°C at the inflow, is pumped. The analyzed element is a recurrent part of a refrigeration's condenser, which is immersed in a paraffin. The temperature of the inflowing liquid is higher than the temperature of the melting process for paraffin, which allows the paraffin to liquify. The temperature at the basis of the rib changes and it is assumed that the heat transfer is quasi-stationary. On this basis the estimation of the mean value of heat transfer coefficient was conducted. The unsteady thermal field of the investigated system was registered with an infrared camera V50 produced by a Polish company Vigo System. This device is equipped with a microbolometric detector with 384 × 288 elements and the single pixel size 25 × 25 μm. Their thermal resolution is lower than 70 mK at a temperature of 30 °C. The camera operates at 7,5 ÷ 14 μm long-wave infrared radiation range. For a typical lens 35 mm the special resolution is 0.7 mrad. The result of the calculations is mean heat transfer coefficient for the considered time series. It is equal to 50 W m -2 K-1 and 47 W m -2 K-1 on the left and right side of the fin, respectively. The distance between the experimental data and the curve approximating the temperature distribution was assessed with the standard deviation, Sd = 0.04 K.

  3. 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

  4. Water Recovery with the Heat Melt Compactor in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Golliher, Eric L.; Goo, Jonathan; Fisher, John

    2015-01-01

    The Heat Melt Compactor is a proposed utility that will compact astronaut trash, extract the water for eventual re-use, and form dry square tiles that can be used as additional ionizing radiation shields for future human deep space missions. The Heat Melt Compactor has been under development by a consortium of NASA centers. The downstream portion of the device is planned to recover a small amount of water while in a microgravity environment. Drop tower low gravity testing was performed to assess the effect of small particles on a capillary-based water/air separation device proposed for the water recovery portion of the Heat Melt Compactor.

  5. Study on solid liquid interface heat transfer of PCM under simultaneous charging and discharging (SCD) in horizontal cylinder annulus

    NASA Astrophysics Data System (ADS)

    Omojaro, Adebola Peter; Breitkopf, Cornelia

    2017-01-01

    Heat transfer performance during the simultaneous charging and discharging (SCD) operation process for phase change materials (PCM) contained inside the annulus of concentric horizontal cylinder was investigated. In the experimental set-up, the PCM inside the annulus serves as the heat sink along with an externally imposed forced cooling air. The obtained time wise temperature profile was used to determine the effects of different heat fluxes and the imposed forced convection cooling on the melt fraction values and the transition shift time from the observed conduction to natural convection heat transfer patterns. Furthermore, non-dimensional analysis was presented for the heat transfer at the interface to enable generalizing the result. Comparison of the results show that the SCD operation mode establish the condition that enables much PCM phase transition time and thus longer time of large latent heat transfer effect than the Partial and non simultaneous operations. Analysis results show that the variation of the heat flux for the SCD mode did not change the dominance of the natural convection over conduction heat transfers in the PCM. However, it significantly influences the commencement/transition shift time and melting rate while higher heat fluxes yields melt fraction that was 38-63% more for investigated process time. Variation with different cooling air flow rate shows more influences on the melt fraction than on the mode of heat transfer occurring in the PCM during melting. Available non-SCD modes correlation was shown to be insufficient to accurately predict interface heat transfer for the SCD modes.

  6. Study on solid liquid interface heat transfer of PCM under simultaneous charging and discharging (SCD) in horizontal cylinder annulus

    NASA Astrophysics Data System (ADS)

    Omojaro, Adebola Peter; Breitkopf, Cornelia

    2017-07-01

    Heat transfer performance during the simultaneous charging and discharging (SCD) operation process for phase change materials (PCM) contained inside the annulus of concentric horizontal cylinder was investigated. In the experimental set-up, the PCM inside the annulus serves as the heat sink along with an externally imposed forced cooling air. The obtained time wise temperature profile was used to determine the effects of different heat fluxes and the imposed forced convection cooling on the melt fraction values and the transition shift time from the observed conduction to natural convection heat transfer patterns. Furthermore, non-dimensional analysis was presented for the heat transfer at the interface to enable generalizing the result. Comparison of the results show that the SCD operation mode establish the condition that enables much PCM phase transition time and thus longer time of large latent heat transfer effect than the Partial and non simultaneous operations. Analysis results show that the variation of the heat flux for the SCD mode did not change the dominance of the natural convection over conduction heat transfers in the PCM. However, it significantly influences the commencement/transition shift time and melting rate while higher heat fluxes yields melt fraction that was 38-63% more for investigated process time. Variation with different cooling air flow rate shows more influences on the melt fraction than on the mode of heat transfer occurring in the PCM during melting. Available non-SCD modes correlation was shown to be insufficient to accurately predict interface heat transfer for the SCD modes.

  7. Three-dimensional model of heat transport during In Situ Vitrification with melting and cool down

    SciTech Connect

    Hawkes, G.L.

    1993-07-01

    A potential technology for permanent remediation of buried wastes is the In Situ Vitrification (ISV) process. This process uses electrical resistance heating to melt waste and contaminated soil in place to produce a durable, glasslike material that encapsulates and immobilizes buried wastes. The magnitude of the resulting electrical resistance heating is sufficient to cause soil melting. As the molten region grows, surface heat losses cause the soil near the surface to re solidify. This paper presents numerical results obtained by considering heat transport and melting when solving the conservation of mass and energy equations using finite element methods. A local heat source is calculated by solving the electric field equation and calculating a Joule Heat source term. The model considered is a three-dimensional model of the electrodes and surrounding soil. Also included in the model is subsidence; where the surface of the melted soil subsides due to the change in density when the soil melts. A power vs. time profile is implemented for typical ISV experiments. The model agrees well with experimental data for melt volume and melt shape.

  8. Heterogeneous nanofluids: natural convection heat transfer enhancement

    PubMed Central

    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

  9. 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.

  10. Electromagnetic levitation facility incorporating electron beam. [for vacuum heating and melting

    NASA Technical Reports Server (NTRS)

    Wouch, G.; Okress, E. C.; Frost, R. T.; Rutecki, D. J.

    1975-01-01

    An electromagnetic levitation apparatus incorporating an electron beam for auxiliary heating and melting has been developed for experiments on containerless vacuum purification and undercooled solidification of high melting materials. Stable levitation of 10-g specimens of molten tungsten has been achieved and a variety of containerless solidification experiments is being performed, including pure polycrystalline castings and single tungsten crystals grown from the undercooled levitated melts.

  11. Heat Transfer Problems of Mixed Refrigerants

    NASA Astrophysics Data System (ADS)

    Fujii, Tetsu; Koyama, Shigeru; Goto, Masao; Takamatsu, Hiroshi

    From the point of view of the application of non-azeotropic mixed refrigerants to heat pump and refrigeration cycles, literatures on condensation and evaporation are surveyed and future problems to be studied are extracted. All researches on the relevant problems are recently started and still in developing way except for condensation on a single horizontal tube. Particularly, the studies for condensation and evaporation of mixed Freon refrigerant in a horizontal tube, which are the most important in practice, are far backward in comparison with single component refrigerant in every point of heat transfer characteristics, flow pattern and theoretical analysis.

  12. Ice Melting by Radiantly Heated Dust Grains on the Martian Northern Pole

    NASA Astrophysics Data System (ADS)

    Losiak, A.; Czechowski, L.; Velbel, M. A.

    2014-09-01

    We present results of the numerical modeling of melting of ice within the martian northern ice cap as a result of radiant heating of a single dust grain exposed within the south-facing side of the spiral trench. Ice can be melted.

  13. Heat transfer in completely and partially filled spherical phase change thermal energy storage modules

    NASA Astrophysics Data System (ADS)

    Rahman, Muhammad Mustafizur

    2016-07-01

    A comprehensive investigation of heat transfer and induced fluid flow interactions during melting in a confined storage medium is reported in this paper. This study focuses on thermal characterization of a single constituent storage module rather than an entire storage system to precisely capture the energy exchange contributions of all fundamental heat transfer mechanisms during phase change process. Two-dimensional, axisymmetric, transient equations for mass, momentum and energy conservation were solved numerically by the finite volume scheme. Results report the influence of the Grashof, Stefan and Prandtl numbers on the melting dynamics of capsules with various diameters (20, 30, 40, and 50 mm). Also the effects of the shell material have been analyzed. Correlating equations for melt fraction and Nusselt number have been developed for possible general design applications.

  14. Acquisition systems for heat transfer measurement

    SciTech Connect

    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.

  15. Coolant passage heat transfer with rotation

    NASA Technical Reports Server (NTRS)

    Hajek, T. J.; Higgins, A. W.

    1985-01-01

    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.

  16. Heat Transfer Characteristics of SHS Reactions

    DTIC Science & Technology

    1990-07-01

    A+R?0 Qt43 =5 -YA co ,/A FINAL REPORT AD- A225 769-=-_ HEAT TRANSFER CHARACTERISTICS OF SHS REACTIONS K. V. Logan, G. R. Villalobos, J. N. Harris, P...2741 Ta 180.9 3287 5731 Cr 52.0 2130 2945 lNb 95.9 2890 4919 W 183.8 3683 >6000 Mli 54.9 1518 2335 Fe 55.8 1808 3135 Co 58.9 1768 3201 Ni 58.7 1726

  17. Boiling Heat Transfer in Confined Space.

    DTIC Science & Technology

    1981-10-01

    the problem the following assumptions were made: Cl) The problem is steady state with constant properties for the fluid. (2) The flow is laminar in...T7ax - 1 62 (11) Heat Transfer: Considering the constant properties and neglecting the viscous dissipation, the energy equation of the laminar flow in...evaluated from the assumed local quality and fluid properties using I.J equation (6). Using an assumed local friction factor f , the local pressure gradient

  18. 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.

  19. 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.

  20. Unsteady heat transfer on turbine blades

    NASA Technical Reports Server (NTRS)

    Cebeci, Tuncer; Simoneau, Robert J.; Platzer, Max F.

    1990-01-01

    This paper describes a method for calculating heat transfer on turbine blades subjected to passing wakes. It is based on the numerical solution of the boundary-layer equations for laminar, transitional, and turbulent flows with a novel procedure to account for the movement of the stagnation point. Results are presented for a model flow and show that the procedure is numerically sound and produces results that can give good agreement with measurements provided that the turbulence model is adequate.

  1. Unsteady heat transfer on turbine blades

    NASA Technical Reports Server (NTRS)

    Cebeci, Tuncer; Simoneau, Robert J.; Platzer, Max F.

    1990-01-01

    This paper describes a method for calculating heat transfer on turbine blades subjected to passing wakes. It is based on the numerical solution of the boundary-layer equations for laminar, transitional, and turbulent flows with a novel procedure to account for the movement of the stagnation point. Results are presented for a model flow and show that the procedure is numerically sound and produces results that can give good agreement with measurements provided that the turbulence model is adequate.

  2. Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)

    SciTech Connect

    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.

  3. HOST turbine heat transfer subproject overview

    NASA Technical Reports Server (NTRS)

    Gladden, Herbert J.

    1986-01-01

    The experimental part of the turbine heat transfer subproject consists of six large experiments, which are highlighted in this overview, and three of somewhat more modest scope. One of the initial efforts was the stator airfoil heat transfer program. The non-film cooled and the showerhead film cooled data have already been reported. The gill region film cooling effort is currently underway. The investigation of secondary flows in a 90 deg curved duct, was completed. The first phase examined flows with a relatively thin inlet boundary layer and low free stream turbulence. The second phase studied a thicker inlet boundary layer and higher free stream turbulence. A comparison of analytical and experimental cross flow velocity vectors is shown for the 60 deg plane. Two experiments were also conducted in the high pressure facility. One examined full coverage film cooled vanes, and the other, advanced instrumentation. The other three large experimental efforts were conducted in a rotation reference frame. An experiment to obtain gas path airfoil heat transfer coefficients in the large, low speed turbine was completed. Single-stage data with both high and low-inlet turbulence were taken. The second phase examined a one and one-half stage turbine and focused on the second vane row. Under phase 3 aerodynamic quantities such as interrow time-averaged and rms values of velocity, flow angle, inlet turbulence, and surface pressure distribution were measured.

  4. Combustion and heat transfer in porous media

    SciTech Connect

    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.

  5. Supercritical oxygen heat transfer. [regenerative cooling

    NASA Technical Reports Server (NTRS)

    Spencer, R. G.; Rousar, D. C.

    1977-01-01

    Heat transfer to supercritical oxygen was experimentally measured in electrical heated tubes. Experimental data were obtained for pressures ranging from 17 to 34.5 MPa (2460 to 5000 psia), and heat fluxes from 2 to 90 million w/sq cm (1.2 to 55 Btu/(sq in. sec)). Bulk temperatures ranged from 96 to 217 K (173 to 391 R). Experimental data obtained by other investigators were added to this to increase the range of pressure down to 2 MPa (290 psia) and increase the range of bulk temperature up to 566 K (1019 R). From this compilation of experimental data a correlating equation was developed which predicts over 95% of the experimental data within + or - 30%.

  6. 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.

  7. Heat transfer of ascending cryomagma on Europa

    NASA Astrophysics Data System (ADS)

    Quick, Lynnae C.; Marsh, Bruce D.

    2016-06-01

    Jupiter's moon Europa has a relatively young surface (60-90 Myr on average), which may be due in part to cryovolcanic processes. Current models for both effusive and explosive cryovolcanism on Europa may be expanded and enhanced by linking the potential for cryovolcanism at the surface to subsurface cryomagmatism. The success of cryomagma transport through Europa's crust depends critically on the rate of ascent relative to the rate of solidification. The final transport distance of cryomagma is thus governed by initial melt volume, ascent rate, overall ascent distance, transport mechanism (i.e., diapirism, diking, or ascent in cylindrical conduits), and melt temperature and composition. The last two factors are especially critical in determining the budget of expendable energy before complete solidification. Here we use these factors as constraints to explore conditions under which cryomagma may arrive at Europa's surface to facilitate cryovolcanism. We find that 1-5 km radius warm ice diapirs ascending from the base of a 10 km thick stagnant lid can reach the shallow subsurface in a partially molten state. Cryomagma transport may be further facilitated if diapirs travel along pre-heated ascent paths. Under certain conditions, cryolava transported from 10 km depths in tabular dikes or pipe-like conduits may reach the surface at temperatures exceeding 250 K. Ascent rates for these geometries may be high enough that isothermal transport is approached. Cryomagmas containing significant amounts of low eutectic impurities can also be delivered to Europa's surface by propagating dikes or pipe-like conduits.

  8. Melting processes of oligomeric α and β isotactic polypropylene crystals at ultrafast heating rates.

    PubMed

    Ji, Xiaojing; He, Xuehao; Jiang, Shichun

    2014-02-07

    The melting behaviors of α (stable) and β (metastable) isotactic polypropylene (iPP) crystals at ultrafast heating rates are simulated with atomistic molecular dynamics method. Quantitative information about the melting processes of α- and β-iPP crystals at atomistic level is achieved. The result shows that the melting process starts from the interfaces of lamellar crystal through random dislocation of iPP chains along the perpendicular direction of lamellar crystal structure. In the melting process, the lamellar crystal gradually expands but the corresponding thickness decreases. The analysis shows that the system expansion lags behind the crystallinity decreasing and the lagging extents for α- and β-iPP are significantly different. The apparent melting points of α- and β-iPP crystals rise with the increase of the heating rate and lamellar crystal thickness. The apparent melting point of α-iPP crystal is always higher than that of β-iPP at differently heating rates. Applying the Gibbs-Thomson rule and the scaling property of the melting kinetics, the equilibrium melting points of perfect α- and β-iPP crystals are finally predicted and it shows a good agreement with experimental result.

  9. Melting processes of oligomeric α and β isotactic polypropylene crystals at ultrafast heating rates

    SciTech Connect

    Ji, Xiaojing; He, Xuehao E-mail: scjiang@tju.edu.cn; Jiang, Shichun E-mail: scjiang@tju.edu.cn

    2014-02-07

    The melting behaviors of α (stable) and β (metastable) isotactic polypropylene (iPP) crystals at ultrafast heating rates are simulated with atomistic molecular dynamics method. Quantitative information about the melting processes of α- and β-iPP crystals at atomistic level is achieved. The result shows that the melting process starts from the interfaces of lamellar crystal through random dislocation of iPP chains along the perpendicular direction of lamellar crystal structure. In the melting process, the lamellar crystal gradually expands but the corresponding thickness decreases. The analysis shows that the system expansion lags behind the crystallinity decreasing and the lagging extents for α- and β-iPP are significantly different. The apparent melting points of α- and β-iPP crystals rise with the increase of the heating rate and lamellar crystal thickness. The apparent melting point of α-iPP crystal is always higher than that of β-iPP at differently heating rates. Applying the Gibbs-Thomson rule and the scaling property of the melting kinetics, the equilibrium melting points of perfect α- and β-iPP crystals are finally predicted and it shows a good agreement with experimental result.

  10. Study for radionuclide transfer ratio of aerosols generated during heat cutting

    SciTech Connect

    Iguchi, Yukihiro; Baba, Tsutomu; Kawakami, Hiroto; Kitahara, Takashi; Watanabe, Atsushi; Kodama, Mitsuhiro

    2007-07-01

    The metallic elements with a low melting point and high vapor pressure seemed to transfer in aerosols selectively at dismantling reactor internals using heat cutting. Therefore, the arc melting tests of neutron irradiated zirconium alloy were conducted to investigate the radionuclide transfer behavior of aerosols generated during the heat cutting of activated metals. The arc melting test was conducted using a tungsten inert gas welding machine in an inert gas or air atmosphere. The radioactive aerosols were collected by filter and charcoal filter. The test sample was obtained from Zry-2 fuel cladding irradiated in a Japanese boiling water reactor for five fuel cycles. The activity analysis, chemical composition measurement and scanning electron microscope observation of aerosols were carried out. Some radionuclides were enriched in the aerosols generated in an inert gas atmosphere and the radionuclide transfer ratio did not change remarkably by the presence of air. The transfer ratio of Sb-125 was almost the same as that of Co-60. It was expected that Sb-125 was enriched from other elements since Sb is an element with a low melting point and high vapor pressure compared with the base metal (Zr). In the viewpoint of the environmental impact assessment, it became clear that the influence if Sb-125 is comparable to Co-60. The transfer ratio of Mn-54 was one order higher compared with other radionuclides. The results were discussed on the basis of thermal properties and oxide formation energy of the metallic elements. (authors)

  11. 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…

  12. 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…

  13. 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.

  14. 7 CFR 2902.54 - Heat transfer fluids.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 15 2011-01-01 2011-01-01 false Heat transfer fluids. 2902.54 Section 2902.54... Items § 2902.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to... heat transfer fluids....

  15. 7 CFR 3201.54 - Heat transfer fluids.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 15 2012-01-01 2012-01-01 false Heat transfer fluids. 3201.54 Section 3201.54... Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants...

  16. 7 CFR 3201.54 - Heat transfer fluids.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 15 2014-01-01 2014-01-01 false Heat transfer fluids. 3201.54 Section 3201.54... Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants...

  17. 7 CFR 3201.54 - Heat transfer fluids.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 15 2013-01-01 2013-01-01 false Heat transfer fluids. 3201.54 Section 3201.54... Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants...

  18. 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.

  19. Non-eruptive ice melt driven by internal heat at glaciated stratovolcanoes

    NASA Astrophysics Data System (ADS)

    Hemmings, Brioch; Whitaker, Fiona; Gottsmann, Joachim; Hawes, Molly C.

    2016-11-01

    Mudflows, floods and lahars from rapid snow and ice melting present potentially devastating hazards to populations surrounding glacial stratovolcanoes. Most ice-melt induced lahars have resulted from eruptive processes. However, there is evidence for non-eruptive hydrothermal volcanic unrest generating rapid and hazardous glacial melt. Here, we use TOUGH2 numerical fluid flow simulations to explore ice melt potential associated with hydrothermal perturbation. Our simulations are loosely based on Cotopaxi Volcano, Ecuadorian Andes. We show that dynamic permeability has a strong control on ice melt response to perturbation. In the absence of concurrent permeability increases, the delay time between onset of a deep hydrothermal perturbation and a response in surface heat flow is on the order of many 10s of years. When increased hot fluid influx at depth is combined with permeability enhancement, the surface heat flow response can be immediate. However, our results suggest that melt rates resulting from such hydrothermal perturbation are still orders of magnitude lower than those induced by eruptive processes; potentially hazardous melt volumes take many months to accumulate, compared to minutes for eruption induced melting. Additional mechanisms, such as glacier destabilisation, meltwater impounding and hydrothermal outburst, may be required to generate volumes of water similar to those associated with catastrophic eruption initiated ice-melt lahars.

  20. Initial solidification phenomena: Factors affecting heat transfer in strip casting

    NASA Astrophysics Data System (ADS)

    Nolli, Paolo

    In the last few years a few companies have announced the final stage of the commercial development of strip casting of steels. In strip casting heat extraction and productivity are limited by the thermal resistance at the interface between processed material and moving mold (rolls for twin-roll strip casters). Among many factors influencing interfacial heat transfer, films of various composition, either formed during casting or deposited before casting on the surface of the rolls, melt superheat and gas atmosphere composition can have a significantly positive or negative effect on the achieved heat transfer rate. From an industrial point view, methods to improve interfacial heat transfer rates must be found, in order to increase productivity. The objective of this research project is to assess if it is feasible to improve heat transfer rates during solidification of steel in direct contact with a copper mold: (1) by the application of thin coatings on the mold surface; (2) by adding a reactive gas species containing sulfur in the gas shrouding where casting is performed. To address the former, solidification experiments were performed with the mold surface either kept uncoated or coated with coatings of different compositions. To address the latter, the experiments were performed in gas shrouding atmospheres with or without sulphydric acid. It was observed that the resulting heat extraction rates were improved by the application of certain coatings and by the addition of H2S to the gas atmosphere. These findings prove that the application of coatings and the use of small amounts of reactive gaseous species containing sulfur may be methods to increase productivity in strip casting. The effect of superheat and the effect of naturally deposited oxides (Mn-oxide) were also evaluated experimentally. A numerical study of the effect of the critical undercooling on the productivity of a twin-roll strip caster showed that the maximum allowable casting speed can be increased

  1. Natural Convection Heat Transfer in a Rectangular Liquid Metal Pool With Bottom Heating and Top Cooling

    SciTech Connect

    Lee, Il S.; Yu, Yong H.; Son, Hyoung M.; Hwang, Jin S.; Suh, Kune Y.

    2006-07-01

    An experimental study is performed to investigate the natural convection heat transfer characteristics with subcooled coolant to create engineering database for basic applications in a lead alloy cooled reactor. Tests are performed in the ALTOS (Applied Liquid-metal Thermal Operation Study) apparatus as part of MITHOS (Metal Integrated Thermo Hydrodynamic Operation System). A relationship is determined between the Nusselt number Nu and the Rayleigh number Ra in the liquid metal rectangular pool. Results are compared with correlations and experimental data in the literature. Given the similar Ra condition, the present test results for Nu of the liquid metal pool with top subcooling are found to be similar to those predicted by the existing correlations or experiments. The current test results are utilized to develop natural convection heat transfer correlations applicable to low Prandtl number Pr fluids that are heated from below and cooled by the external coolant above. Results from this study are slated to be used in designing BORIS (Battery Optimized Reactor Integral System), a small lead cooled modular fast reactor for deployment at remote sites cycled with MOBIS (Modular Optimized Brayton Integral System) for electricity generation, tied with NAVIS (Naval Application Vessel Integral System) for ship propulsion, joined with THAIS (Thermochemical Hydrogen Acquisition Integral System) for hydrogen production, and coupled with DORIS (Desalination Optimized Reactor Integral System) for seawater desalination. Tests are performed with Wood's metal (Pb-Bi-Sn-Cd) filling a rectangular pool whose lower surface is heated and upper surface cooled by forced convection of water. The test section is 20 cm long, 11.3 cm high and 15 cm wide. The simulant has a melting temperature of 78 deg. C. The constant temperature and heat flux condition was realized for the bottom heating once the steady state had been met. The test parameters include the heated bottom surface temperature

  2. The role of heat transfer in strip casting

    NASA Astrophysics Data System (ADS)

    Misra, Paretosh

    . It was discovered that these films originate from the metal itself. A high degree of interdendritic supersaturation can lead to the formation of low melting point oxide phases by the deoxidizing agents in the steel. As the temperature lowers further the film may get ejected out of the metal due to the non-wetting of the metal by the oxide phase. If enough oxide film can be generated then this can result in an almost two-fold increase in the rate of heat transfer during initial solidification---the first 20 milliseconds. The results indicate that if a proper control of these films is ensured then it provides an attractive alternative to increasing the roll diameter as a mechanism of increasing the rate of production of a strip caster. This mechanism will work even with smaller diameter rolls, in fact, perhaps better in that case due to a smaller interface area over which uniformity of heat transfer has to be ensured, thus leveraging its full advantages. If successfully implemented at a plant, this technique can help the strip casting machines to increase their productivity and emerge as a competitive technology to produce steel strip.

  3. 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.

  4. Lattice Boltzmann technique for heat transport phenomena coupled with melting process

    NASA Astrophysics Data System (ADS)

    Ibrahem, A. M.; El-Amin, M. F.; Mohammadein, A. A.; Gorla, Rama Subba Reddy

    2017-01-01

    In this work, the heat transport phenomena coupled with melting process are studied by using the enthalpy-based lattice Boltzmann method (LBM). The proposed model is a modified version of thermal LB model, where could avoid iteration steps and ensures high accuracy. The Bhatnagar-Gross-Krook (BGK) approximation with a D1Q2 lattice was used to determine the temperature field for one-dimensional melting by conduction and multi-distribution functions (MDF) with D2Q9 lattice was used to determine the density, velocity and temperature fields for two-dimensional melting by natural convection. Different boundary conditions including Dirichlet, adiabatic and bounce-back boundary conditions were used. The influence of increasing Rayleigh number (from 103 to 105) on temperature distribution and melting process is studied. The obtained results show that a good agreement with the analytical solution for melting by conduction case and with the benchmark solution for melting by convection.

  5. Consistent melting behavior induced by Joule heating between Ag microwire and nanowire meshes.

    PubMed

    Tsuchiya, Kaoru; Li, Yuan; Saka, Masumi

    2014-01-01

    The melting behavior of an Ag microwire mesh induced by Joule heating was numerically investigated and compared with that of the corresponding Ag nanowire mesh with the same structure but different geometrical and physical properties of the wire itself. According to the relationship of melting current and melting voltage during the melting process, a similar repetitive zigzag pattern in melting behavior was discovered in both meshes. On this basis, a dimensionless parameter defined as figure of merit was proposed to characterize the current-carrying ability of the mesh. The consistent feature of figure of merit in both meshes indicates that the melting behavior of the Ag nanowire mesh can be predicted from the present results of the corresponding Ag microwire mesh with the same structure but made from a different wire (e.g., different size, different material) through simple conversion. The present findings can provide fundamental insight into the reliability analysis on the metallic nanowire mesh-based transparent conductive electrode.

  6. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

  7. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

  8. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's heat...

  9. Ice melting properties of steel slag asphalt concrete with microwave heating

    NASA Astrophysics Data System (ADS)

    Li, Bin; Sun, Yihan; Liu, Quantao; Fang, Hao; Wu, Shaopeng; Tang, Jin; Ye, Qunshan

    2017-03-01

    The ice on the surface of asphalt pavement in winter significantly influences the road transportation safety. This paper aims at the improvement of the ice melting efficiency on the surface of asphalt pavement. The steel slag asphalt concrete was prepared and the high ice melting efficiency was achieved with the microwave heating. A series of experiments were conducted to evaluate the ice melting performance of steel slag asphalt concrete, including the heating test, ice melting test, thermal conductivity test and so on. The results indicated that the microwave heating of steel slag concrete can improve the efficiency of deicing, mainly because the heating rates of steel slag asphalt mixture are much better than traditional limestone asphalt mixture. According to different thickness lever of ice, the final temperatures of each sample were very close to each other at the end of melting test. It is believed the thickness of the ice has a limited impact on the ice melting efficiency. According to the heating tests results, the bonding of ice and asphalt concrete is defined failure at the moment when the surface temperature of the ice reached 3 °C.

  10. Influence of controlling vibrations on heat transfer in floating zone crystal growth*

    NASA Astrophysics Data System (ADS)

    Fedyushkin, A. I.

    The crystal growth processes of monocrystals are strongly vibrational sensitive systems and in particular it concerns to a floating zone method as presence of a free surface and two fronts of crystallization and melting that aggravate it The given work is devoted to numerical investigations of the influence of controlling vibrations on heat transfer during crystal growth by floating zone technique Normal and weightless environment conditions are considered Mathematical simulation is performed on the numerical solutions of basis unsteady Navier-Stokes equations for incompressible fluid flows and energy equation 2D axisymmetric geometry was used in model Marangoni convection and radiation condition on the curvature free surface were taken in account The calculations of the shape of a free surface of a liquid zone and influences on it of a corner of wetting force of weight and size of factor of a superficial tension are carried out The simulations of convective heat transfer for real curvature free surface of a liquid zone with and without the taking into account of the following factors parameters of radiation rotations natural and Marangoni convection and vibrations are carried out The given calculations are carried out for semiconductors melts with Prandtl number Pr 1 and for oxides Pr 1 The influence of vibrations of a crystal on melt flow and on the wide of dynamic and thermal boundary layers at melt-crystal interface is studied The action of vibrations on an enhancement of heat fluxes at the melt crystal interface is shown

  11. 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.

  12. Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling

    NASA Astrophysics Data System (ADS)

    Passalacqua, Olivier; Ritz, Catherine; Parrenin, Frédéric; Urbini, Stefano; Frezzotti, Massimo

    2017-09-01

    Basal melt rate is the most important physical quantity to be evaluated when looking for an old-ice drilling site, and it depends to a great extent on the geothermal flux (GF), which is poorly known under the East Antarctic ice sheet. Given that wet bedrock has higher reflectivity than dry bedrock, the wetness of the ice-bed interface can be assessed using radar echoes from the bedrock. But, since basal conditions depend on heat transfer forced by climate but lagged by the thick ice, the basal ice may currently be frozen whereas in the past it was generally melting. For that reason, the risk of bias between present and past conditions has to be evaluated. The objective of this study is to assess which locations in the Dome C area could have been protected from basal melting at any time in the past, which requires evaluating GF. We used an inverse approach to retrieve GF from radar-inferred distribution of wet and dry beds. A 1-D heat model is run over the last 800 ka to constrain the value of GF by assessing a critical ice thickness, i.e. the minimum ice thickness that would allow the present local distribution of basal melting. A regional map of the GF was then inferred over a 80 km × 130 km area, with a N-S gradient and with values ranging from 48 to 60 mW m-2. The forward model was then emulated by a polynomial function to compute a time-averaged value of the spatially variable basal melt rate over the region. Three main subregions appear to be free of basal melting, two because of a thin overlying ice and one, north of Dome C, because of a low GF.

  13. 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.

  14. Measurement of Latent Heat of Melting of Thermal Storage Materials for Dynamic Type Ice Thermal Storage

    NASA Astrophysics Data System (ADS)

    Sawada, Hisashi; Okada, Masashi; Nakagawa, Shinji

    In order to measure the latent heat of melting of ice slurries with various solute concentrations, an adiabatic calorimeter was constructed. Ice slurries were made from each aqueous solution of ethanol, ethylene glycol and silane coupling agent. The latent heat of melting of ice made from tap water was measured with the present calorimeter and the uncertainty of the result was one percent. Ice slurries were made both by mixing ice particles made from water with each aqueous solution and by freezing each aqueous solution with stirring in a vessel. The latent heat of melting of these ice slurries was measured with various concentrations of solution. The latent heat of melting decreased as the solute concentration or the freezing point depression increased. The latent heat of ice slurries made from ethanol or ethylene glycol aqueous solution agreed with that of ice made from pure water known already. The latent heat of melting of ice slurries made from silane coupling agent aqueous solution got smaller than that of ice made from pure water as the freezing point depression increased.

  15. Numerical and Experimental Approaches Toward Understanding Lava Flow Heat Transfer

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    We have performed numerical modeling and experimental studies to quantify the heat transfer from a lava flow into an underlying particulate substrate. This project was initially motivated by a desire to understand the transfer of heat from a lava flow into the lunar regolith. Ancient regolith deposits that have been protected by a lava flow may contain ancient solar wind, solar flare, and galactic cosmic ray products that can give insight into the history of our solar system, provided the records were not heated and destroyed by the overlying lava flow. In addition, lava-substrate interaction is an important aspect of lava fluid dynamics that requires consideration in lava emplacement models Our numerical model determines the depth to which the heat pulse will penetrate beneath a lava flow into the underlying substrate. Rigorous treatment of the temperature dependence of lava and substrate thermal conductivity and specific heat capacity, density, and latent heat release are imperative to an accurate model. Experiments were conducted to verify the numerical model. Experimental containers with interior dimensions of 20 x 20 x 25 cm were constructed from 1 inch thick calcium silicate sheeting. For initial experiments, boxes were packed with lunar regolith simulant (GSC-1) to a depth of 15 cm with thermocouples embedded at regular intervals. Basalt collected at Kilauea Volcano, HI, was melted in a gas forge and poured directly onto the simulant. Initial lava temperatures ranged from ~1200 to 1300 °C. The system was allowed to cool while internal temperatures were monitored by a thermocouple array and external temperatures were monitored by a Forward Looking Infrared (FLIR) video camera. Numerical simulations of the experiments elucidate the details of lava latent heat release and constrain the temperature-dependence of the thermal conductivity of the particulate substrate. The temperature-dependence of thermal conductivity of particulate material is not well known

  16. [Mechanism of heat transfer in various regions of human body].

    PubMed

    Luchakov, Iu I; Nozdrachev, A D

    2009-01-01

    The processes of heat transfer in a human body were studied with the use of a mathematical model. It has been shown that only conductive or only convective heat transfer may occur in different body areas. The rate of blood-mediated heat transfer in the presence of blood circulation is many times higher than heat transfer due to temperature gradient; therefore, the convective process prevails over the conductive process. The body core contains a variety of blood vessels, and the bulk of blood concentrates there in the norm. Hence, heat transfer in it is mainly convective. In surface tissues, where the rate of blood circulation is lower and the vasculature has certain specific features, heat transfer is mainly conductive. Hence, the core and surface tissues are absolutely different body zones in terms of heat transfer.

  17. Transient heat transfer in superfluid helium

    SciTech Connect

    Dresner, L.

    1981-01-01

    According to the Goerter-Mellink law, the heat flux in superfluid helium is proportional to the cube root of the temperature gradient. If we use this proportionality in place of Fourier's linear law to derive an equation of heat conduction, we obtain a non-linear partial differential equation. Such equations are usually difficult to solve because we cannot superpose solutions to obtain others. In spite of this, the problem of this paper, the constant-flux problem, can be solved because its temperature profiles are self-similar. Self-similarity means that the temperature profile at one time can be obtained from that at a different time by suitable (different) stretching of the distance and temperature axes of the latter profle. The self-similarity of the temperature profiles is connected with the invariance of the non-linear partial differential equation to certain groups of transformations. We reduce the partial differential equation of heat conduction to an ordinary differential equation, the appropriate solution of which we find without extensive computation. The reduction involves the similarity variables ..delta..T/..sqrt..t and z/..sqrt..t, where ..delta..T is the temperature rise at a distance z from the heated face at a time t after the (constant) heating has begun. Use of these variables should, and does, reduce all of the experimental temperature profiles reported by van Sciver to a single, universal curve. We obtain this curve as well by solving the differential equation; agreement is excellent. In fact agreement with all the experimental data reported by van Sciver is excellent, so that the Goerter-Mellink law seems to be a very successful basis for describing transient heat transfer in superfluid helium.

  18. Advances in refrigeration and heat transfer engineering

    DOE PAGES

    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

  19. Advances in refrigeration and heat transfer engineering

    SciTech Connect

    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 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).

  20. Convective heat transfer and infrared thermography.

    PubMed

    Carlomagno, Giovanni M; Astarita, Tommaso; Cardone, Gennaro

    2002-10-01

    Infrared (IR) thermography, because of its two-dimensional and non-intrusive nature, can be exploited in industrial applications as well as in research. This paper deals with measurement of convective heat transfer coefficients (h) in three complex fluid flow configurations that concern the main aspects of both internal and external cooling of turbine engine components: (1) flow in ribbed, or smooth, channels connected by a 180 degrees sharp turn, (2) a jet in cross-flow, and (3) a jet impinging on a wall. The aim of this study was to acquire detailed measurements of h distribution in complex flow configurations related to both internal and external cooling of turbine components. The heated thin foil technique, which involves the detection of surface temperature by means of an IR scanning radiometer, was exploited to measure h. Particle image velocimetry was also used in one of the configurations to precisely determine the velocity field.

  1. Heat Transfer Model for Hot Air Balloons

    NASA Astrophysics Data System (ADS)

    Llado-Gambin, Adriana

    A heat transfer model and analysis for hot air balloons is presented in this work, backed with a flow simulation using SolidWorks. The objective is to understand the major heat losses in the balloon and to identify the parameters that affect most its flight performance. Results show that more than 70% of the heat losses are due to the emitted radiation from the balloon envelope and that convection losses represent around 20% of the total. A simulated heating source is also included in the modeling based on typical thermal input from a balloon propane burner. The burner duty cycle to keep a constant altitude can vary from 10% to 28% depending on the atmospheric conditions, and the ambient temperature is the parameter that most affects the total thermal input needed. The simulation and analysis also predict that the gas temperature inside the balloon decreases at a rate of -0.25 K/s when there is no burner activity, and it increases at a rate of +1 K/s when the balloon pilot operates the burner. The results were compared to actual flight data and they show very good agreement indicating that the major physical processes responsible for balloon performance aloft are accurately captured in the simulation.

  2. Porous media heat transfer for injection molding

    DOEpatents

    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.

  3. Heat transfer augmentation in nanofluids via nanofins.

    PubMed

    Vadasz, Peter

    2011-02-18

    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.

  4. Convective Heat Transfer for Ship Propulsion.

    DTIC Science & Technology

    1985-11-29

    frpiac i aU cd i INds-- butl .<. Contract No. N00014-75-C-0694; NR-097-395 ! _; "’ ~CONVECTIVE HEAT TRANSFER FOR SHIP PROPULSION -’- Aerospace and...Claaification, CONVECTIVEHET7 TRNSE FOR SHIP PROPULSION (U) ______ 1.PRSONAL AUTHOR(S) McEligot, Donald M., P. 0. Box 4282, Middletown, Rhode Island...cooled -"ireactors using N2 04 compared with atomic2 4- I.- electric stations using sodium. The potential benefits for ship propulsion are obvious

  5. 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.

  6. Analysis of radial fin assembly heat transfer with dehumidification

    SciTech Connect

    Rosario, L.; Rahman, M.M.

    1996-12-31

    The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing heat transfer rate with and without fins under the same operating conditions. Numerical calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. Results were compared to those published for rectangular fin under humid condition showed excellent agreement when the present model was used to compute that limiting condition. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature.

  7. 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.

  8. Fibre optic sensors for heat transfer studies

    NASA Astrophysics Data System (ADS)

    Sinha, Pranay G.

    This thesis describes the design and development of a prototype sensor, based on a miniature optical fiber Fabry-Perot interferometer, for heat transfer studies on model turbomachinery components in transient flow wind tunnels. These sensors overcome a number of difficulties which are often encountered in using conventional electrical thin-film resistance gauges such as in the measurement of rapidly varying heat transfer rates, spatial resolution, electromagnetic interference, calibration and signal processing. The special features of the optical sensor are: (1) short length (less than 5 mm), and therefore embeddable in thin structures of model components; (2) direct measurement of heat flux rates; (3) calorimetric operation with temperature resolution of less than 25 mK over a measurement bandwidth of 100 kHz; (4) capability of measuring heat flux less than 5 kWm(exp -2) with measurement range in excess of 10 MWm(exp -2); (5) temporal response time of less than 10 microseconds; (6) minimal thermal disturbances because models are often made of ceramic materials with thermal properties similar to those of the optical fiber from which sensors are made;(7) possibility of using in models with dissimilar thermal properties to the optical fiber, for example, metals; (8) spatial resolution of less than 5 microns; (9) remote operation; (10) an ability to be multiplexed; and (11) immunity to electromagnetic interference. A detailed discussion of the design considerations for the sensor, system development, evaluation of the sensor performance both in the laboratory and wind tunnel environments is presented in this thesis. The performance of the sensor compared favorably with electrical gauges namely, platinum thin-film resistance thermometers. A 4-sensor multiplexed system has been successfully operated, and is reported in the thesis. A brief discussion is also included to indicate that the same sensor design may be considered for applications in other engineering areas.

  9. Fibre Optic Sensors for Heat Transfer Studies.

    NASA Astrophysics Data System (ADS)

    Sinha, Pranay G.

    Available from UMI in association with The British Library. This thesis describes the design and development of a prototype sensor, based on a miniature optical fibre Fabry-Perot interferometer, for heat transfer studies on model turbomachinery components in transient flow wind tunnels. These sensors overcome a number of difficulties which are often encountered in using conventional electrical thin-film resistance gauges such as in the measurement of rapidly varying heat transfer rates, spatial resolution, electromagnetic interference, calibration and signal processing. The special features of the optical sensor are: (i) short length (<5 mm), and therefore embeddable in thin structures of model components; (ii) direct measurement of heat flux rates; (iii) calorimetric operation with temperature resolution of <25 mK over a measurement bandwidth of 100 kHz: (iv) capability of measuring heat flux <5 kWm^ {-2} with measurement range in excess of 10 MWm^{-2}; (v) temporal response time of <10 mus; (vi) minimal thermal disturbances because models are often made of ceramic materials with thermal properties similar to those of the optical fibre from which sensors are made; (vii) possibility of using in models with dissimilar thermal properties to the optical fibre, for example, metals; (viii) spatial resolution of <5 mu m; (ix) remote operation; (x) an ability to be multiplexed; and (xi) immunity to electromagnetic interference. A detailed discussion of the design considerations for the sensor, system development, evaluation of the sensor performance both in the laboratory and wind tunnel environments is presented in this thesis. The performance of the sensor compared favourably with electrical gauges namely, platinum thin-film resistance thermometers. A 4-sensor multiplexed system has been sucessfully operated, and is reported in the thesis. A brief discussion is also included to indicate that the same sensor design may be considered for applications in other engineering

  10. Core-concrete molten pool dynamics and interfacial heat transfer. [PWR; BWR

    SciTech Connect

    Benjamin, A.S.

    1980-01-01

    Theoretical models are derived for the heat transfer from molten oxide pools to an underlying concrete surface and from molten steel pools to a general concrete containment. To accomplish this, two separate effects models are first developed, one emphasizing the vigorous agitation of the molten pool by gases evolving from the concrete and the other considering the insulating effect of a slag layer produced by concrete melting. The resulting algebraic expressions, combined into a general core-concrete heat transfer representation, are shown to provide very good agreement with experiments involving molten steel pours into concrete crucibles.

  11. Novel Low-Melt Viscosity Polyimides for Resin Transfer Molding (RTM)

    DTIC Science & Technology

    2008-08-29

    are amenable to RTM , and potentially adaptable to vacuum assisted resin transfer molding ( VARTM ) processes. Figure 2 shows that the absolute...2008 Research/Final 01/02/2006 -28/05/08 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER NOVEL LOW-MELT VISCOSITY POLYIMIDES FOR RESIN TRANSFER MOLDING ( RTM ...the range of 10-30 poise and high glass transition temperatures (T,s) of 330-370 ’C were developed for resin transfer molding ( RTM ) applications

  12. Heat Transfer Phenomena in Supercritical Water Nuclear Reactors

    SciTech Connect

    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.

  13. Active chimney effect using heated porous layers: optimum heat transfer

    NASA Astrophysics Data System (ADS)

    Mehiris, Abdelhak; Ameziani, Djamel-Edine; Rahli, Omar; Bouhadef, Khadija; Bennacer, Rachid

    2017-05-01

    The purpose of the present work is to treat numerically the problem of the steady mixed convection that occurs in a vertical cylinder, opened at both ends and filled with a succession of three fluid saturated porous elements, namely a partially porous duct. The flow conditions fit with the classical Darcy-Brinkman model allowing analysing the flow structure on the overall domain. The induced heat transfer, in terms of local and average Nusselt numbers, is discussed for various controlling parameters as the porous medium permeability, Rayleigh and Reynolds numbers. The efficiency of the considered system is improved by the injection/suction on the porous matrices frontier. The undertaken numerical exploration particularly highlighted two possible types of flows, with and without fluid recirculation, which principally depend on the mixed convection regime. Thus, it is especially shown that recirculation zones appear in some domain areas under specific conditions, obvious by a negative central velocity and a prevalence of the natural convection effects, i.e., turnoff flow swirls. These latter are more accentuated in the areas close to the porous obstacles and for weak permeability. Furthermore, when fluid injection or suction is considered, the heat transfer increases under suction and reduces under injection. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  14. Thermal Assessment of a Latent-Heat Energy Storage Module During Melting and Freezing for Solar Energy Applications

    NASA Astrophysics Data System (ADS)

    Ramos Archibold, Antonio

    Capital investment reduction, exergetic efficiency improvement and material compatibility issues have been identified as the primary techno-economic challenges associated, with the near-term development and deployment of thermal energy storage (TES) in commercial-scale concentrating solar power plants. Three TES techniques have gained attention in the solar energy research community as possible candidates to reduce the cost of solar-generated electricity, namely (1) sensible heat storage, (2) latent heat (tank filled with phase change materials (PCMs) or encapsulated PCMs packed in a vessel) and (3) thermochemical storage. Among these the PCM macro-encapsulation approach seems to be one of the most-promising methods because of its potential to develop more effective energy exchange, reduce the cost associated with the tank and increase the exergetic efficiency. However, the technological barriers to this approach arise from the encapsulation techniques used to create a durable capsule, as well as an assessment of the fundamental thermal energy transport mechanisms during the phase change. A comprehensive study of the energy exchange interactions and induced fluid flow during melting and solidification of a confined storage medium is reported in this investigation from a theoretical perspective. Emphasis has been placed on the thermal characterization of a single constituent storage module rather than an entire storage system, in order to, precisely capture the energy exchange contributions of all the fundamental heat transfer mechanisms during the phase change processes. Two-dimensional, axisymmetric, transient equations for mass, momentum and energy conservation have been solved numerically by the finite volume scheme. Initially, the interaction between conduction and natural convection energy transport modes, in the absence of thermal radiation, is investigated for solar power applications at temperatures (300--400°C). Later, participating thermal radiation

  15. Results from the DCH-1 (Direct Containment Heating) experiment. [Pressurized melt ejection and direct containment heating

    SciTech Connect

    Tarbell, W.W.; Brockmann, J.E.; Pilch, M.; Ross, J.E.; Oliver, M.S.; Lucero, D.A.; Kerley, T.E.; Arellano, F.E.; Gomez, R.D.

    1987-05-01

    The DCH-1 (Direct Containment Heating) test was the first experiment performed in the Surtsey Direct Heating Test Facility. The test involved 20 kg of molten core debris simulant ejected into a 1:10 scale model of the Zion reactor cavity. The melt was produced by a metallothermic reaction of iron oxide and aluminum powders to yield molten iron and alumina. The cavity model was placed so that the emerging debris propagated directly upwards along the vertical centerline of the chamber. Results from the experiment showed that the molten material was ejected from the caviity as a cloud of particles and aerosol. The dispersed debris caused a rapid pressurization of the 103-m/sup 3/ chamber atmosphere. Peak pressure from the six transducers ranged from 0.09 to 0.13 MPa (13.4 to 19.4 psig) above the initial value in the chamber. Posttest debris collection yielded 11.6 kg of material outside the cavity, of which approximately 1.6 kg was attributed to the uptake of oxygen by the iron particles. Mechanical sieving of the recovered debris showed a lognormal size distribution with a mass mean size of 0.55 mm. Aerosol measurements indicated a subsantial portion (2 to 16%) of the ejected mass was in the size range less than 10 m aerodynamic equivalent diameter.

  16. Study and Analysis of Heat Transfer Limitation of Separated Heat Pipe

    NASA Astrophysics Data System (ADS)

    Mou, Qizheng; Mou, Kai

    2002-01-01

    satellite and spacecraft. evaporator, heat isolation and condenser along the axial direction. The working fluid absorbs heat and evaporates in evaporator, and then the vapor flows to condenser and gives out heat. The condensed liquid is pumped to evaporator by wick. By the circulation, the heat can by transferred continuously. heat pipe as follow: - Vapor-liquid two phase flow inside pipe; - The manner of latent heat to transfer heat; - Automatic circulation by working fluid flowing - A certain extent of vacuum. and the traditional heat pipe, that is, the vapor fluid and liquid fluid flow along the same direction. So it is obviously that the separated heat pipe has special internal heat transfer characteristic and crisis. This paper has regard for the heat transfer crisis of the separated heat pipe, and meanwhile relevant calculation and analysis have been done. 1. FLOW TYPE OF THE WORKING FLUID IN SEPARATED HEAT PIPE 2. HEAT TRANSFER CRISIS IN THE EVAPORATOR 3. CARRYING PHENOMENON INSIDE SEPARATED HEAT PIPE 4. THE STAGNANT FLOW PHENOMENON AND THE BACKWARD FLOW PHENOMENON IN EVAPORATOR CONCLUSION transfer limitation of location burn-out, and the heat transfer limitation of flow unconventionality in erective pipe. The carrying phenomenon can occurs not only in evaporator but also in condenser of separated heat pipe. It is in the evaporator that should take place the heat transfer limitation of liquid film dry-out at first. Then with the increasing of heat flux, the heat transfer limitation of location burn-out would happen. In order to avoid the heat transfer limitation of flow unconventionality in erective pipe, the length and diameter of the outflow tube and inflow tube must be reasonably calculated to control the flow velocity of the working fluid inside pipe. Key words:Separated Heat PipeHeat Transfer LimitationDry-OutCarryingStagnancy

  17. 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.

  18. 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.

  19. Micro-grooved heat transfer combustor wall

    NASA Technical Reports Server (NTRS)

    Ward, Steven D. (Inventor)

    1994-01-01

    A gas turbine engine hot section combustor liner is provided a non-film cooled portion of a heat transfer wall having a hot surface and a plurality of longitudinally extending micro-grooves disposed in the portion of the wall along the hot surface in a direction parallel to the direction of the hot gas flow. The depth of the micro-grooves is very small and on the order of magnitude of a predetermined laminar sublayer of a turbulent boundary layer. The micro-grooves are sized so as to inhibit heat transfer from the hot gas flow to the hot surface of the wall while reducing NOx emissions of the combustor relative to an otherwise similar combustor having a liner wall portion including film cooling apertures. In one embodiment the micro-grooves are about 0.001 inches deep and have a preferred depth range of from about 0.001 inches to 0.005 inches and which are square, rectangular, or triangular in cross-section and the micro-grooves are spaced about one width apart.

  20. Transient critical heat flux and blowdown heat-transfer studies

    SciTech Connect

    Leung, J.C.

    1980-05-01

    Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.

  1. Material transport in laser-heated diamond anvil cell melting experiments

    NASA Technical Reports Server (NTRS)

    Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

    1992-01-01

    A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

  2. Material transport in laser-heated diamond anvil cell melting experiments

    NASA Technical Reports Server (NTRS)

    Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

    1992-01-01

    A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

  3. Boiling local heat transfer enhancement in minichannels using nanofluids

    NASA Astrophysics Data System (ADS)

    Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony

    2013-03-01

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

  4. Boiling local heat transfer enhancement in minichannels using nanofluids

    PubMed Central

    2013-01-01

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

  5. Boiling local heat transfer enhancement in minichannels using nanofluids.

    PubMed

    Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony

    2013-03-18

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

  6. A Novel Heat Treatment Process for Surface Hardening of Steel: Metal Melt Surface Hardening

    NASA Astrophysics Data System (ADS)

    Fu, Yong-sheng; Zhang, Wei; Xu, Xiaowei; Li, Jiehua; Li, Jun; Xia, Mingxu; Li, Jianguo

    2017-09-01

    A novel heat treatment process for surface hardening of steel has been demonstrated and named as "metal melt surface hardening (MMSH)." A surface layer with a thickness of about 400 μm and a hardness of about 700 HV has been achieved by ejecting AISI 304 stainless steel melt at a temperature of about 1783 K (1510 °C) onto the 40Cr steel surface. This proposed MMSH provides a very promising application for surface hardening of steel.

  7. Heat transfer assembly for a fluorescent lamp and fixture

    DOEpatents

    Siminovitch, M.J.; Rubenstein, F.M.; Whitman, R.E.

    1992-12-29

    In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure. 11 figs.

  8. Heat transfer assembly for a fluorescent lamp and fixture

    DOEpatents

    Siminovitch, Michael J.; Rubenstein, Francis M.; Whitman, Richard E.

    1992-01-01

    In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure.

  9. Fundamental heat transfer processes related to phase change thermal storage media

    SciTech Connect

    Sparrow, E. M.; Ramsey, J. W.

    1981-01-01

    Research on fundamental heat transfer processes which occur in phase-change thermal storage systems is described. The research encompasses both melting and freezing, and includes both experiment and analysis. The status of four research problems is discussed. One of the freezing problems was focused on investigating, via experiment, the extent to which freezing can be enhanced by the attachment of fins to the external surface of a cooled vertical tube situated in a liquid phase-change medium. Very substantial enhancements were encountered which neutralize the degradation of freezing due to the thermal resistance of the frozen layer and to natural convection in the liquid phase. The second of the freezing problems was analytical in nature and sought to obtain solutions involving both the phase-change medium and the heat transfer fluid used either to add heat to or extract heat from the medium. For freezing on a plane wall, it was possible to obtain a closed-form analytical solution, while for freezing about a coolant-carrying circular tube, a new numerical methodology was devised to obtain finite-difference solutions. For melting, quantitative design-quality heat transfer coefficients were determined experimentally for melting adjacent to a heated vertical tube. These experiments explored the effects of solid-phase subcooling and of open versus closed top containment on the coefficients. A dimensionless correlation enables these results to be used for a wide range of phase-change media. Studies on melting of a phase-change material situated within a circular tube are in progress.

  10. Convective heat transfer in porous media

    NASA Astrophysics Data System (ADS)

    Cheng, P.

    Recent emerging technologies on the extraction of geothermal energy, the design of insulation systems for energy conservation, the use of aquifers for hot-water storage, the disposal of nuclear wastes in sub-seabeds, the enhanced recovery of oils by thermal methods, and the design of catalyst-bed reactors have demanded an improved understanding of heat transfer mechanisms in fluid-filled porous media. Experiments have been conducted to investigate the onset of free convection in rectangular and cylindrical enclosures filled with porous media and heated from below. The Nusselt numbers determined from these experiments during steady conditions are correlated in terms of the Rayleigh number. The data for free convection in rectangular geometries show considerable scattering among investigators using different porous media and fluids. Recently, some data has been obtained for free convect on in water-filled glass beads adjacent to a heated vertical flat plate, a horizontal cylinder and between vertical concentric cylinders. The data obtained at low Rayleigh numbers is found to be in good agreement with theoretical predictions based on Darcy's law.

  11. Control of Impingement Heat Transfer Using Mist

    NASA Astrophysics Data System (ADS)

    Kanamori, Azusa; Hiwada, Munehiko; Mimatsu, Junji; Sugimoto, Hiraku; Oyakawa, Kenyuu

    Impingement heat transfer from a circular orifice jet by using latent heat of water mists was studied experimentally. The amounts of mists of about Zauter's mean diameter 14 µm were from 60 to 200 g/h within a range where liquid films were not formed on the target plate and mists were added near the orifice edge. Experiments covered Reynolds numbers from 12,500 to 50,000 and a heat flux is 1,400 W/m2. The experimental results indicate that adding mists had little influence on free jet mean velocity profiles and target plate pressure coefficients. On the other hand, mists had a strong influence on temperature and humidity profiles of a free jet and they also influenced Nusselt number distributions on the target plate. Increases of mists and Reynolds number caused increases in Nusselt number on the developed region. In addition, we investigated influence of the way mists were added and these results showed that Nusselt number was influenced not only by the amounts of mists but also by the adding method. Local Nusselt number profiles with mists were closely related to temperature distributions of the free jet at the location corresponding to the target plate.

  12. The heat transfer of cooling fins on moving air

    NASA Technical Reports Server (NTRS)

    Doetsch, Hans

    1935-01-01

    The present report is a comparison of the experimentally defined temperature and heat output of cooling fins in the air stream with theory. The agreement is close on the basis of a mean coefficient of heat transfer with respect to the total surface. A relationship is established between the mean coefficient of heat transfer, the dimensions of the fin arrangement, and the air velocity.

  13. Heat transfer from starlings sturnus vulgaris during flight

    PubMed

    Ward; Rayner; MOLler; Jackson; Nachtigall; Speakman

    1999-06-01

    Infrared thermography was used to measure heat transfer by radiation and the surface temperature of starlings (Sturnus vulgaris) (N=4) flying in a wind tunnel at 6-14 m s-1 and at 15-25 degrees C. Heat transfer by forced convection was calculated from bird surface temperature and biophysical modelling of convective heat transfer coefficients. The legs, head and ventral brachial areas (under the wings) were the hottest parts of the bird (mean values 6.8, 6.0 and 5.3 degrees C, respectively, above air temperature). Thermal gradients between the bird surface and the air decreased at higher air temperatures or during slow flight. The legs were trailed in the air stream during slow flight and when air temperature was high; this could increase heat transfer from the legs from 1 to 12 % of heat transfer by convection, radiation and evaporation (overall heat loss). Overall heat loss at a flight speed of 10.2 m s-1 averaged 11. 3 W, of which radiation accounted for 8 % and convection for 81 %. Convection from the ventral brachial areas was the most important route of heat transfer (19 % of overall heat loss). Of the overall heat loss, 55 % occurred by convection and radiation from the wings, although the primaries and secondaries were the coolest parts of the bird (2.2-2.5 degrees C above air temperature). Calculated heat transfer from flying starlings was most sensitive to accurate measurement of air temperature and convective heat transfer coefficients.

  14. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's...

  15. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430 Section 153.430... Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo cooling system required by... separated from all other cooling and heating systems; and (c) Allow manual regulation of the system's...

  16. Strain heating in process zones; implications for metamorphism and partial melting in the lithosphere

    NASA Astrophysics Data System (ADS)

    Devès, Maud H.; Tait, Stephen R.; King, Geoffrey C. P.; Grandin, Raphaël

    2014-05-01

    Since the late 1970s, most earth scientists have discounted the plausibility of melting by shear-strain heating because temperature-dependent creep rheology leads to negative feedback and self-regulation. This paper presents a new model of distributed shear-strain heating that can account for the genesis of large volumes of magmas in both the crust and the mantle of the lithosphere. The kinematic (geometry and rates) frustration associated with incompatible fault junctions (e.g. triple-junction) prevents localisation of all strain on the major faults. Instead, deformation distributes off the main faults forming a large process zone that deforms still at high rates under both brittle and ductile conditions. The increased size of the shear-heated region minimises conductive heat loss, compared with that commonly associated with narrow shear zones, thus promoting strong heating and melting under reasonable rheological assumptions. Given the large volume of the heated zone, large volumes of melt can be generated even at small melt fractions.

  17. Ocean heat drives rapid basal melt of the Totten Ice Shelf

    PubMed Central

    Rintoul, Stephen Rich; Silvano, Alessandro; Pena-Molino, Beatriz; van Wijk, Esmee; Rosenberg, Mark; Greenbaum, Jamin Stevens; Blankenship, Donald D.

    2016-01-01

    Mass loss from the West Antarctic ice shelves and glaciers has been linked to basal melt by ocean heat flux. The Totten Ice Shelf in East Antarctica, which buttresses a marine-based ice sheet with a volume equivalent to at least 3.5 m of global sea-level rise, also experiences rapid basal melt, but the role of ocean forcing was not known because of a lack of observations near the ice shelf. Observations from the Totten calving front confirm that (0.22 ± 0.07) × 106 m3 s−1 of warm water enters the cavity through a newly discovered deep channel. The ocean heat transport into the cavity is sufficient to support the large basal melt rates inferred from glaciological observations. Change in ocean heat flux is a plausible physical mechanism to explain past and projected changes in this sector of the East Antarctic Ice Sheet and its contribution to sea level. PMID:28028540

  18. Ocean heat drives rapid basal melt of the Totten Ice Shelf.

    PubMed

    Rintoul, Stephen Rich; Silvano, Alessandro; Pena-Molino, Beatriz; van Wijk, Esmee; Rosenberg, Mark; Greenbaum, Jamin Stevens; Blankenship, Donald D

    2016-12-01

    Mass loss from the West Antarctic ice shelves and glaciers has been linked to basal melt by ocean heat flux. The Totten Ice Shelf in East Antarctica, which buttresses a marine-based ice sheet with a volume equivalent to at least 3.5 m of global sea-level rise, also experiences rapid basal melt, but the role of ocean forcing was not known because of a lack of observations near the ice shelf. Observations from the Totten calving front confirm that (0.22 ± 0.07) × 10(6) m(3) s(-1) of warm water enters the cavity through a newly discovered deep channel. The ocean heat transport into the cavity is sufficient to support the large basal melt rates inferred from glaciological observations. Change in ocean heat flux is a plausible physical mechanism to explain past and projected changes in this sector of the East Antarctic Ice Sheet and its contribution to sea level.

  19. Melting Phenomenon in MHD Stagnation Point Flow of Dusty Fluid over a Stretching Sheet in the Presence of Thermal Radiation and Non-Uniform Heat Source/Sink

    NASA Astrophysics Data System (ADS)

    Prasannakumara, B. C.; Gireesha, B. J.; Manjunatha, P. T.

    2015-09-01

    A comprehensive numerical study is conducted to investigate the effect of melting on flow and heat transfer of incompressible viscous dusty fluid near two-dimensional stagnation-point flow over a stretching surface, in the presence of thermal radiation, non-uniform heat source/sink and applied magnetic field. Using suitable transformations, the governing nonlinear partial differential equations are transformed into a set of coupled nonlinear ordinary differential equations and then they are solved numerically. The influence of the various interesting parameters on the flow and heat transfer is analyzed and discussed in detail through plotted graphs. Comparison of the present results with existing results is shown and a good agreement is observed. We found that the velocity and temperature fields increase with an increase in the melting process of the stretching sheet.

  20. The dry-heat loss effect of melt-spun phase change material fibres.

    PubMed

    Tjønnås, Maria Suong; Færevik, Hilde; Sandsund, Mariann; Reinertsen, Randi E

    2015-01-01

    Phase change materials (PCM) have the ability to store latent heat when they change phases, a property that gives clothing that incorporates PCM its cooling effect. This study investigated the effect of dry-heat loss (cooling) of a novel melt-spun PCM fibre on the basis of the area covered, mass, the latent heat of fusion and melting temperature, compared to a known PCM clothing product. PCM fibres with melting temperatures of 28.4 and 32.0°C and PCM packs with melting temperatures of 28.0 and 32.0°C were studied. The results showed that the PCM fibres had a larger initial peak cooling effect than that of the PCM packs. The duration of the cooling effect of PCM fibres was primarily dependent on the PCM mass and the latent heat of fusion capacity, and secondly on the covered area and melting temperature of the PCM. This study investigates the cooling effect of PCM fibres on a thermal manikin. The PCM fibres had a high but short-lasting cooling effect. This study contributes to the knowledge of how the body's temperature regulation may be affected by the cooling properties of clothing that incorporates PCM.

  1. Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles

    NASA Astrophysics Data System (ADS)

    Kılıç, Bayram; İpek, Osman

    2017-02-01

    In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.

  2. Radiative heat transfer in curved specular surfaces in Czochralski crystal growth furnace

    SciTech Connect

    Guo, Z.; Maruyama, Shigenao; Tsukada, Takao

    1997-11-07

    A numerical investigation of radiative heat transfer constructed by curved surfaces with specular and diffuse reflection components is carried out. The ray tracing method is adopted for the calculation of view factors, in which a new ray emission model is proposed. The second-degree radiation ring elements are introduced, which are of engineering importance and numerical efficiency. The accuracy of the method is analyzed and verified using a simple configuration. The present computation using the proposed ray emission model is in good agreement with the analytical solution. As a numerical example and engineering application, the effects of the specular reflection and the meniscus of the melt surface in Czochralski (CZ) crystal growth are investigated. A marked temperature decrease in the melt surface is found by introducing specular reflection and the meniscus. The combined effects of the specular reflection and the meniscus should be considered in precision heat transfer control of a CZ apparatus.

  3. Natural convection heat transfer analysis of ATR fuel elements

    SciTech Connect

    Langerman, M.A.

    1992-05-01

    Natural convection air cooling of the Advanced Test Reactor (ATR) fuel assemblies is analyzed to determine the level of decay heat that can be removed without exceeding the melting temperature of the fuel. The study was conducted to assist in the level 2 PRA analysis of a hypothetical ATR water canal draining accident. The heat transfer process is characterized by a very low Rayleigh number (Ra {approx} 10{sup {minus}5}) and a high temperature ratio. Since neither data nor analytical models were available for Ra < 0.1, an analytical approach is presented based upon the integral boundary layer equations. All assumptions and simplifications are presented and assessed and two models are developed from similar foundations. In one model, the well-known Boussinesq approximations are employed, the results from which are used to assess the modeling philosophy through comparison to existing data and published analytical results. In the other model, the Boussinesq approximations are not used, thus making the model more general and applicable to the ATR analysis.

  4. Modelling heat transfer in heterogeneous media using fractional calculus.

    PubMed

    Sierociuk, Dominik; Dzielinski, Andrzej; Sarwas, Grzegorz; Petras, Ivo; Podlubny, Igor; Skovranek, Tomas

    2013-05-13

    This paper presents the results of modelling the heat transfer process in heterogeneous media with the assumption that part of the heat flux is dispersed in the air around the beam. The heat transfer process in a solid material (beam) can be described by an integer order partial differential equation. However, in heterogeneous media, it can be described by a sub- or hyperdiffusion equation which results in a fractional order partial differential equation. Taking into consideration that part of the heat flux is dispersed into the neighbouring environment we additionally modify the main relation between heat flux and the temperature, and we obtain in this case the heat transfer equation in a new form. This leads to the transfer function that describes the dependency between the heat flux at the beginning of the beam and the temperature at a given distance. This article also presents the experimental results of modelling real plant in the frequency domain based on the obtained transfer function.

  5. Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. V.; Shamirzaev, A. S.

    2015-11-01

    The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.

  6. Effects of the heat transfer fluid velocity on the storage characteristics of a cylindrical latent heat energy storage system: a numerical study

    NASA Astrophysics Data System (ADS)

    Ogoh, Wilson; Groulx, Dominic

    2012-03-01

    A numerical study of the effects of the thermal fluid velocity on the storage characteristics of a cylindrical latent heat energy storage system (LHESS) was conducted. Due to the low thermal conductivity of phase change materials (PCMs) used in LHESS, fins were added to the system to increase the rate of heat transfer and charging. Finite elements were used to implement the developed numerical method needed to study and solve for the phase change heat transfer (melting of PCM) encountered in a LHESS during charging. The effective heat capacity method was applied in order to account for the large amount of latent energy stored during melting of the PCM and the moving interface between the solid and liquid phases. The effects of the heat transfer fluid (HTF) velocity on the melting rate of the PCM were studied for configurations having between 0 and 18 fins. Results show that the overall heat transfer rate to the PCM increases with an increase in the HTF velocity. However, the effect of the HTF velocity was observed to be small in configurations having very few fins, owing to the large residual thermal resistance offered by the PCM. However, the effect of the HTF velocity becomes more pronounced with addition of fins; since the thermal resistance on the PCM side of the LHESS is significantly reduce by the large number of fins in the system.

  7. Heat transfer analysis of cylindrical anaerobic reactors with different sizes: a heat transfer model.

    PubMed

    Liu, Jiawei; Zhou, Xingqiu; Wu, Jiangdong; Gao, Wen; Qian, Xu

    2017-08-28

    The temperature is the essential factor that influences the efficiency of anaerobic reactors. During the operation of the anaerobic reactor, the fluctuations of ambient temperature can cause a change in the internal temperature of the reactor. Therefore, insulation and heating measures are often used to maintain anaerobic reactor's internal temperature. In this paper, a simplified heat transfer model was developed to study heat transfer between cylindrical anaerobic reactors and their surroundings. Three cylindrical reactors of different sizes were studied, and the internal relations between ambient temperature, thickness of insulation, and temperature fluctuations of the reactors were obtained at different reactor sizes. The model was calibrated by a sensitivity analysis, and the calibrated model was well able to predict reactor temperature. The Nash-Sutcliffe model efficiency coefficient was used to assess the predictive power of heat transfer models. The Nash coefficients of the three reactors were 0.76, 0.60, and 0.45, respectively. The model can provide reference for the thermal insulation design of cylindrical anaerobic reactors.

  8. Nanofluids for heat transfer: an engineering approach.

    PubMed

    Timofeeva, Elena V; Yu, Wenhua; France, David M; Singh, Dileep; Routbort, Jules 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.

  9. Turbine disk cavity aerodynamics and heat transfer

    NASA Technical Reports Server (NTRS)

    Johnson, B. V.; Daniels, W. A.

    1992-01-01

    Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant flow injected into the disk cavities; (3) coolant density; (4) leakage flows through the seal between blades; and (5) the role that each of these various flows has in determining the adiabatic recovery temperature at all of the critical locations within the cavities. The model and the test apparatus provide close geometrical and aerodynamic simulation of all the two-stage cavity flow regions for the SSME High Pressure Fuel Turbopump and the ability to simulate the sources and sinks for each cavity flow.

  10. Heat transfer characteristics in film cooling applications

    NASA Astrophysics Data System (ADS)

    Licu, Dragos Nicolae

    1998-11-01

    The leading edge region of gas turbine blades and vanes experiences high thermal and mechanical stresses and has to be properly cooled. External cooling of the leading edge region is typically achieved by a film cooling technique. An investigation into the film cooling effectiveness of three different large scale leading edge geometries is presented in this study. One of the geometries investigated represents an original design and is an example of an improved film cooling layout. AD geometries used have four rows of cooling holes placed symmetrically about the geometrical leading edge, but the layout of the cooling holes is different from one leading edge geometry to another. A broad range of variables is considered including mass flow ratio, coolant density, and jet Reynolds number. Film cooling effectiveness measurements were made in a low speed wind tunnel environment using a flame ionization detector technique and the mass/heat transfer analogy. These measurements significantly extend the insight into the effects of hole geometry on the film cooling characteristics of the leading edge of turbine blades and provide new data for design purposes. The effect of geometry is more important for the case of double row injection where spanwise-averaged film cooling effectiveness is improved by the use of compound angle holes. The spanwise-averaged film cooling effectiveness is higher at lower mass flow ratios and decreases typically as the mass flow ratio increases. At higher mass flow ratios, the newly designed leading edge geometry produces higher spanwise-averaged film cooling effectiveness than the other two geometries investigated thus providing the necessary backflow margin at operating conditions more relevant to gas turbine use. For the case of single row injection, the effects of geometry scale reasonably well when the local mass flow ratio is used in the analysis of the spanwise-averaged film cooling effectiveness immediately downstream of the injection holes

  11. Nanofluids for heat transfer : an engineering approach.

    SciTech Connect

    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.

  12. Heat and mass transfer in flames

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.

    1986-01-01

    Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.

  13. Heat and mass transfer in flames

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.

    1986-01-01

    Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.

  14. Submersible pumping system with heat transfer mechanism

    DOEpatents

    Hunt, Daniel Francis Alan; Prenger, F. Coyne; Hill, Dallas D; Jankowski, Todd Andrew

    2014-04-15

    A submersible pumping system for downhole use in extracting fluids containing hydrocarbons from a well. In one embodiment, the pumping system comprises a rotary induction motor, a motor casing, one or more pump stages, and a cooling system. The rotary induction motor rotates a shaft about a longitudinal axis of rotation. The motor casing houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted. The pump stages are attached to the shaft outside of the motor casing, and are configured to impart fluid being extracted from the well with an increased pressure. The cooling system is disposed at least partially within the motor casing, and transfers heat generated by operation of the rotary induction motor out of the motor casing.

  15. HEAT TRANSFER AND TRITIUM PRODUCING SYSTEM

    DOEpatents

    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)

  16. Analysis of the heat transfer in double and triple concentric tube heat exchangers

    NASA Astrophysics Data System (ADS)

    Rădulescu, S.; Negoiţă, L. I.; Onuţu, I.

    2016-08-01

    The tubular heat exchangers (shell and tube heat exchangers and concentric tube heat exchangers) represent an important category of equipment in the petroleum refineries and are used for heating, pre-heating, cooling, condensation and evaporation purposes. The paper presents results of analysis of the heat transfer to cool a petroleum product in two types of concentric tube heat exchangers: double and triple concentric tube heat exchangers. The cooling agent is water. The triple concentric tube heat exchanger is a modified constructive version of double concentric tube heat exchanger by adding an intermediate tube. This intermediate tube improves the heat transfer by increasing the heat area per unit length. The analysis of the heat transfer is made using experimental data obtained during the tests in a double and triple concentric tube heat exchanger. The flow rates of fluids, inlet and outlet temperatures of water and petroleum product are used in determining the performance of both heat exchangers. Principally, for both apparatus are calculated the overall heat transfer coefficients and the heat exchange surfaces. The presented results shows that triple concentric tube heat exchangers provide better heat transfer efficiencies compared to the double concentric tube heat exchangers.

  17. Methods and problems in heat and mass transfer

    NASA Astrophysics Data System (ADS)

    Kotliar, Iakov Mikhailovich; Sovershennyi, Viacheslav Dmitrievich; Strizhenov, Dmitrii Sergeevich

    The book focuses on the mathematical methods used in heat and mass transfer problems. The theory, statement, and solution of some problems of practical importance in heat and mass transfer are presented, and methods are proposed for solving algebraic, transcendental, and differential equations. Examples of exact solutions to heat and mass transfer equations are given. The discussion also covers some aspects of the development of a mathematical model of turbulent flows.

  18. Flow and heat transfer in microchannels using a microcontinuum approach

    SciTech Connect

    Jacobi, A.M. )

    1989-11-01

    Heat and mass transfer in small channels has many important applications. Recent advances in electronic cooling technology have suggested the use of microchannels for cooling electronic components. The purpose of this note is to employ Eringen's theory to predict how heat transfer may be affected as the classical fluid model breaks down. Such predictions hold not only theoretical importance, but may serve useful in modeling heat transfer in microchannel, or arterioles where the theory has been widely applied.

  19. Liquid jet impingement heat transfer with or without boiling

    NASA Astrophysics Data System (ADS)

    Ma, C. F.; Gan, Y. P.; Tian, Y. C.; Lei, D. H.; Gomi, T.

    1993-03-01

    The purpose of this paper is to summarize the important studies in the area of impingement heat transfer with or without phase change, with emphasis on the research conducted at Beijing Polytechnic University mainly with circular jets. Heat transfer characteristics of single phase jets are discussed in detail. Comment is presented on boiling heat transfer of impinging jets for steady and transient states. Some special cooling configurations of two-phase jets are also introduced.

  20. Sensitivity Analysis of the Gap Heat Transfer Model in BISON.

    SciTech Connect

    Swiler, Laura Painton; Schmidt, Rodney C.; Williamson, Richard; Perez, Danielle

    2014-10-01

    This report summarizes the result of a NEAMS project focused on sensitivity analysis of the heat transfer model in the gap between the fuel rod and the cladding used in the BISON fuel performance code of Idaho National Laboratory. Using the gap heat transfer models in BISON, the sensitivity of the modeling parameters and the associated responses is investigated. The study results in a quantitative assessment of the role of various parameters in the analysis of gap heat transfer in nuclear fuel.

  1. In - line determination of heat transfer coefficients in a plate heat exchanger

    NASA Astrophysics Data System (ADS)

    Sotelo, S. Silva; Domínguez, R. J. Romero

    This paper shows an in - line determination of heat transfer coefficients in a plate heat exchanger. Water and aqueous working solution of lithium bromide + ethylene glycol are considered. Heat transfer coefficients are calculated for both fluids. "Type T" thermocouples were used for monitoring the wall temperature in a plate heat exchanger, which is one of the main components in an absorption system. Commercial software Agilent HP Vee Pro 7.5 was used for monitoring the temperatures and for the determination of the heat transfer coefficients. There are not previous works for heat transfer coefficients for the working solution used in this work.

  2. High thermal power density heat transfer. [thermionic converters

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1980-01-01

    Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. The heat pipe is used to cool the nuclear reactor while the heat pipe is connected thermally and electrically to a thermionic converter. If the receiver requires greater thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparatively low thermal power densities through the electrically non-conducting gap between the two heat pipes.

  3. Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump

    DOEpatents

    Phillips, Benjamin A.; Zawacki, Thomas S.; Marsala, Joseph

    1994-11-29

    Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium.

  4. Heat transfer enhancement by application of nano-powder

    NASA Astrophysics Data System (ADS)

    Mosavian, M. T. Hamed; Heris, S. Zeinali; Etemad, S. Gh.; Esfahany, M. Nasr

    2010-09-01

    In this investigation, laminar flow heat transfer enhancement in circular tube utilizing different nanofluids including Al2O3 (20 nm), CuO (50 nm), and Cu (25 nm) nanoparticles in water was studied. Constant wall temperature was used as thermal boundary condition. The results indicate enhancement of heat transfer with increasing nanoparticle concentrations, but an optimum concentration for each nanofluid suspension can be found. Based on the experimental results, metallic nanoparticles show better enhancement of heat transfer coefficient in comparison with oxide particles. The promotions of heat transfer due to utilizing nanoparticles are higher than the theoretical correlation prediction.

  5. Nonlinear Transient Problems Using Structure Compatible Heat Transfer Code

    NASA Technical Reports Server (NTRS)

    Hou, Gene

    2000-01-01

    The report documents the recent effort to enhance a transient linear heat transfer code so as to solve nonlinear problems. The linear heat transfer code was originally developed by Dr. Kim Bey of NASA Largely and called the Structure-Compatible Heat Transfer (SCHT) code. The report includes four parts. The first part outlines the formulation of the heat transfer problem of concern. The second and the third parts give detailed procedures to construct the nonlinear finite element equations and the required Jacobian matrices for the nonlinear iterative method, Newton-Raphson method. The final part summarizes the results of the numerical experiments on the newly enhanced SCHT code.

  6. Conjugate Heat Transfer in Porous Cavity: ANN approach

    NASA Astrophysics Data System (ADS)

    Jafer Kazi1, Mohammed; Yunus Khan, T. M.

    2017-08-01

    Artificial neural network is a technique to predict the outcome of a function depending on various input parameters that could be either or geometric variables. This technique is widely used in many fields to predict an outcome. The current article discusses the usage of artificial neural network to predict conjugate heat transfer behaviour inside the porous cavity. The artificial neural network is run with neurons placed in multiple layers. The heat transfer inside the porous cavity is predicted in terms of Nusselt number which shows the convective heat transfer in relation to its conduction counterpart. The heat transfer prediction is compared with the results obtained by finite element method.

  7. Ethyl alcohol boiling heat transfer on multilayer meshed surfaces

    NASA Astrophysics Data System (ADS)

    Dåbek, Lidia; Kapjor, Andrej; Orman, Łukasz J.

    2016-06-01

    The paper presents the problem of heat transfer enhancement with the application of multilayer metal mesh structures during boiling of ethyl alcohol at ambient pressure. The preparation of samples involved sintering fine copper meshes with the copper base in the reduction atmosphere in order to prevent oxidation of the samples. The experiments included testing up to 4 layers of copper meshes. Significant augmentation of boiling heat transfer is possible, however, considerable number of meshes actually hinders heat transfer conditions and leads to the reduction in the heat flux transferred from the heater surface.

  8. Liquid-Infused Smooth Surface for Improved Condensation Heat Transfer.

    PubMed

    Tsuchiya, Hirotaka; Tenjimbayashi, Mizuki; Moriya, Takeo; Yoshikawa, Ryohei; Sasaki, Kaichi; Togasawa, Ryo; Yamazaki, Taku; Manabe, Kengo; Shiratori, Seimei

    2017-09-12

    Control of vapor condensation properties is a promising approach to manage a crucial part of energy infrastructure conditions. Heat transfer by vapor condensation on superhydrophobic coatings has garnered attention, because dropwise condensation on superhydrophobic surfaces with rough structures leads to favorable heat-transfer performance. However, pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation of superhydrophobic surfaces limit their heat-transfer increase. Recently, slippery liquid-infused surfaces (SLIPS) have been investigated, because of their high water sliding ability and surface smoothness originating from the liquid layer. However, even on SLIPS, condensed water droplets are eventually pinned to degrade their heat-transfer properties after extended use, because the rough base layer is exposed as infused liquid is lost. Herein, we report a liquid-infused smooth surface named "SPLASH" (surface with π electron interaction liquid adsorption, smoothness, and hydrophobicity) to overcome the problems derived from the rough structures in previous approaches to obtain stable, high heat-transfer performance. The SPLASH displayed a maximum condensation heat-transfer coefficient that was 175% higher than that of an uncoated substrate. The SPLASH also showed higher heat-transfer performance and more stable dropwise condensation than superhydrophobic surfaces and SLIPS from the viewpoints of condensed water droplet mobility and the thermodynamic energy barrier for nucleation. The effects of liquid-infused surface roughness and liquid viscosity on condensation heat transfer were investigated to compare heat-transfer performance. This research will aid industrial applications using vapor condensation.

  9. Heat transfer coefficient in serpentine coolant passage for CCDTL

    SciTech Connect

    Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.

    1998-12-31

    A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.

  10. Heat Transfer Variation on Protuberances and Surface Roughness Elements

    NASA Technical Reports Server (NTRS)

    Henry, Robert C.; Hansman, R. John, Jr.; Breuer, Kenneth S.

    1995-01-01

    In order to determine the effect of surface irregularities on local convective heat transfer, the variation in heat transfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heat transfer enhancement was observed to vary over the roughness elements with the maximum heat transfer on the upstream face. This heat transfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heat transfer enhancement was relatively constant with velocity, but did increase with element size. When multiple roughness elements were studied, no influence of adjacent roughness elements on heat transfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heat transfer was observed on the downstream elements. Implications of the observed roughness enhanced heat transfer on ice accretion modeling are discussed.

  11. CarbAl Heat Transfer Material

    NASA Technical Reports Server (NTRS)

    Fink, Richard

    2015-01-01

    The increasing use of power electronics, such as high-current semiconductor devices and modules, within space vehicles is driving the need to develop specialty thermal management materials in both the packaging of these discrete devices and the packaging of modules consisting of these device arrays. Developed by Applied Nanotech, Inc. (ANI), CarbAl heat transfer material is uniquely characterized by its low density, high thermal diffusivity, and high thermal conductivity. Its coefficient of thermal expansion (CTE) is similar to most power electronic materials, making it an effective base plate substrate for state-of-the-art silicon carbide (SiC) super junction transistors. The material currently is being used to optimize hybrid vehicle inverter packaging. Adapting CarbAl-based substrates to space applications was a major focus of the SBIR project work. In Phase I, ANI completed modeling and experimentation to validate its deployment in a space environment. Key parameters related to cryogenic temperature scaling of CTE, thermal conductivity, and mechanical strength. In Phase II, the company concentrated on improving heat sinks and thermally conductive circuit boards for power electronic applications.

  12. TACO: a finite element heat transfer code

    SciTech Connect

    Mason, W.E. Jr.

    1980-02-01

    TACO is a two-dimensional implicit finite element code for heat transfer analysis. It can perform both linear and nonlinear analyses and can be used to solve either transient or steady state problems. Either plane or axisymmetric geometries can be analyzed. TACO has the capability to handle time or temperature dependent material properties and materials may be either isotropic or orthotropic. A variety of time and temperature dependent loadings and boundary conditions are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additionally, TACO has some specialized features such as internal surface conditions (e.g., contact resistance), bulk nodes, enclosure radiation with view factor calculations, and chemical reactive kinetics. A user subprogram feature allows for any type of functional representation of any independent variable. A bandwidth and profile minimization option is also available in the code. Graphical representation of data generated by TACO is provided by a companion post-processor named POSTACO. The theory on which TACO is based is outlined, the capabilities of the code are explained, the input data required to perform an analysis with TACO are described. Some simple examples are provided to illustrate the use of the code.

  13. Heat transfer characteristics of igniter output plumes

    NASA Astrophysics Data System (ADS)

    Evans, N. A.; Durand, N. A.

    Seven types of pyrotechnic igniters were each mounted at one end of a closed cylindrical bore hole representative of the center hole in a thermal battery. Measurements of local bore wall temperature, T(sub w), using commercially available, fast response (10 microsec) sheathed chromel-constantan thermocouples allowed calculation of local heat transfer rates, q, and wall heat flows, Q. The principal charge constituents of all these igniters were titanium and potassium perchlorate, while three types also contained barium styphnate as an ignition sensitizer. Igniter closure disc materials included glass-ceramic, glass, metal (plain, scored, with and without capture cone), and kapton/RTV. All igniters produced the lowest values of T(sub w) and q at the beginning of the bore, and, except for the igniter with the kapton/RTV closure disc, these quantities increased with distance along the bore. For igniters containing only titanium/potassium perchlorate, the rates of increase of Q along the bore length, compared with those for T(sub w) and q, were generally lower and more variable. The inclusion of barium styphnate produced rates of change in Q that were essentially constant to the end of the bore. The highest overall average wall temperatures were achieved by two igniter types with metal closure discs and no capture cone. No clear correlation was established between peak bore pressure and maximum wall temperature.

  14. Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump

    DOEpatents

    Phillips, Benjamin A.; Zawacki, Thomas S.

    1996-12-03

    Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. A combination of weak and rich liquor working solution is used as the heat transfer medium.

  15. Personalized recommendation based on heat bidirectional transfer

    NASA Astrophysics Data System (ADS)

    Ma, Wenping; Feng, Xiang; Wang, Shanfeng; Gong, Maoguo

    2016-02-01

    Personalized recommendation has become an increasing popular research topic, which aims to find future likes and interests based on users' past preferences. Traditional recommendation algorithms pay more attention to forecast accuracy by calculating first-order relevance, while ignore the importance of diversity and novelty that provide comfortable experiences for customers. There are some levels of contradictions between these three metrics, so an algorithm based on bidirectional transfer is proposed in this paper to solve this dilemma. In this paper, we agree that an object that is associated with history records or has been purchased by similar users should be introduced to the specified user and recommendation approach based on heat bidirectional transfer is proposed. Compared with the state-of-the-art approaches based on bipartite network, experiments on two benchmark data sets, Movielens and Netflix, demonstrate that our algorithm has better performance on accuracy, diversity and novelty. Moreover, this method does better in exploiting long-tail commodities and cold-start problem.

  16. Heat transfer enhancement -- the maturing of second-generation heat transfer technology

    SciTech Connect

    Bergles, A.E.

    1997-01-01

    This paper is basically the text of the Kern Lecture for 1991 (the 1990 Kern Award). The paper begins with some remarks about Dr. Kern. By way of introduction to heat transfer enhancement, historical notes and the evolution of literature in this area are presented. Comments are made about the increasing practical applications of enhancement technology. Developments in single-phase convection are presented, with particular emphasis on offset strip fins and twisted-tape inserts. Pool boiling and flow boiling (particularly microfin tubes) are then considered in some detail. It is concluded that enhancement represents a powerful technology to improve heat exchanger performance.

  17. The heat transfer coefficients of the heating surface of 300 MWe CFB boiler

    NASA Astrophysics Data System (ADS)

    Wu, Haibo; Zhang, Man; Lu, Qinggang; Sun, Yunkai

    2012-08-01

    A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.

  18. Heat Transfer Model of a Small-Scale Waste Glass Melter with Cold Cap Layer

    SciTech Connect

    Abboud, Alexander; Guillen, Donna Post; Pokorny, Richard

    2016-09-01

    At the Hanford site in the state of Washington, more than 56 million gallons of radioactive waste is stored in underground tanks. The cleanup plan for this waste is vitrification at the Waste Treatment Plant (WTP), currently under construction. At the WTP, the waste will be blended with glass-forming materials and heated to 1423K, then poured into stainless steel canisters to cool and solidify. A fundamental understanding of the glass batch melting process is needed to optimize the process to reduce cost and decrease the life cycle of the cleanup effort. The cold cap layer that floats on the surface of the glass melt is the primary reaction zone for the feed-to-glass conversion. The conversion reactions include water release, melting of salts, evolution of batch gases, dissolution of quartz and the formation of molten glass. Obtaining efficient heat transfer to this region is crucial to achieving high rates of glass conversion. Computational fluid dynamics (CFD) modeling is being used to understand the heat transfer dynamics of the system and provide insight to optimize the process. A CFD model was developed to simulate the DM1200, a pilot-scale melter that has been extensively tested by the Vitreous State Laboratory (VSL). Electrodes are built into the melter to provide Joule heating to the molten glass. To promote heat transfer from the molten glass into the reactive cold cap layer, bubbling of the molten glass is used to stimulate forced convection within the melt pool. A three-phase volume of fluid approach is utilized to model the system, wherein the molten glass and cold cap regions are modeled as separate liquid phases, and the bubbling gas and plenum regions are modeled as one lumped gas phase. The modeling of the entire system with a volume of fluid model allows for the prescription of physical properties on a per-phase basis. The molten glass phase and the gas phase physical properties are obtained from previous experimental work. Finding representative

  19. Condensation heat transfer coefficient with noncondensible gases for heat transfer in thermal hydraulic codes

    SciTech Connect

    Banerjee, S.; Hassan, Y.A.

    1995-09-01

    Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology`s (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values.

  20. Synthesis, heating, and melting of stoichiometric glass (CaSiO3·SiO2)

    NASA Astrophysics Data System (ADS)

    Engelsht, V. S.; Muratalieva, V. Zh.

    2014-01-01

    Thermodynamic analysis (TERRA program) of synthesis, heating, and melting of stoichiometric glass CaSiO3·SiO2 has been carried out. Chemically pure substances silica and lime are subjected to exothermic reaction with further external heating and melting. Wollastonite is synthesized, the chemical reaction generates heat Q chr = -505.3 kJ/kg, and temperature increases T = 820 K. When T melt = 1812-1814 K, wollastonite melts, and a mixture of liquid wollastonite and condensed silica is formed. At T melt = 1995-1997 K, silica melts, and stoichiometric glass (CaSiO3·SiO2) is formed. Evolutions of temperature and melting of wollastonite and silica have been studied by detailed step-by-step thermodynamic calculation (Δ T = 0.1 K).

  1. Heat transfer research on supercritical water flow upward in tube

    SciTech Connect

    Li, H. B.; Yang, J.; Gu, H. Y.; Zhao, M.; Lu, D. H.; Zhang, J. M.; Wang, F.; Zhang, Y.

    2012-07-01

    The experimental research of heat transfer on supercritical water has been carried out on the supercritical water multipurpose test loop with a 7.6 mm upright tube. The experimental data of heat transfer is obtained. The experimental results of thermal-hydraulic parameters on flow and heat transfer of supercritical water show that: Heat transfer enhancement occurs when the fluid temperature reaches pseudo-critical point with low mass flow velocity, and peters out when the mass flow velocity increases. The heat transfer coefficient and Nusselt number decrease with the heat flux or system pressure increases, and increase with the increasing of mass flow velocity. The wall temperature increases when the mass flow velocity decreases or the system pressure increases. (authors)

  2. Study of a high performance evaporative heat transfer surface

    NASA Technical Reports Server (NTRS)

    Saaski, E. W.; Hamasaki, R. H.

    1977-01-01

    An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.

  3. ^40Ar-^39Ar Step Heating of Nördlinger Ries Crater Impact Melts

    NASA Astrophysics Data System (ADS)

    Schwarz, W. H.; Lippolt, H. J.

    2013-09-01

    Ries impact melt samples were analyzed via Ar-Ar step heating technique. All samples contain excess argon increasing the app. ages. Only for one sample a plateau age can be calculated to 14.6 ± 0.2 Ma identical with published age values for Moldavites.

  4. Thermooptical properties of gold nanoparticles embedded in ice: characterization of heat generation and melting.

    PubMed

    Richardson, Hugh H; Hickman, Zackary N; Govorov, Alexander O; Thomas, Alyssa C; Zhang, Wei; Kordesch, Martin E

    2006-04-01

    We investigate the system of optically excited gold NPs in an ice matrix aiming to understand heat generation and melting processes at the nanoscale level. Along with the traditional fluorescence method, we introduce thermooptical spectroscopy based on phase transformation of a matrix. With this, we can not only measure optical response but also thermal response, that is, heat generation. After several recrystallization cycles, the nanoparticles are embedded into the ice film where the optical and thermal properties of the nanoparticles are probed. Spatial fluorescence mapping shows the locations of Au nanoparticles, whereas the time-resolved Raman signal of ice reveals the melting process. From the time-dependent Raman signals, we determine the critical light intensities at which the laser beam is able to melt ice around the nanoparticles. The melting intensity depends strongly on temperature and position. The position-dependence is especially strong and reflects a mesoscopic character of heat generation. We think that it comes from the fact that nanoparticles form small complexes of different geometry and each complex has a unique thermal response. Theoretical calculations and experimental data are combined to make a quantitative measure of the amount of heat generated by optically excited Au nanoparticles and agglomerates. The information obtained in this study can be used to design nanoscale heaters and actuators.

  5. Partial melting of a Pb-Sn mushy layer due to heating from above, and implications for regional melting of Earth's directionally solidified inner core

    NASA Astrophysics Data System (ADS)

    Yu, James; Bergman, Michael I.; Huguet, Ludovic; Alboussiere, Thierry

    2015-09-01

    Superimposed on the radial solidification of Earth's inner core may be hemispherical and/or regional patches of melting at the inner-outer core boundary. Little work has been carried out on partial melting of a dendritic mushy layer due to heating from above. Here we study directional solidification, annealing, and partial melting from above of Pb-rich Sn alloy ingots. We find that partial melting from above results in convection in the mushy layer, with dense, melted Pb sinking and resolidifying at a lower height, yielding a different density profile than for those ingots that are just directionally solidified, irrespective of annealing. Partial melting from above causes a greater density deeper down and a corresponding steeper density decrease nearer the top. There is also a change in microstructure. These observations may be in accordance with inferences of east-west and perhaps smaller-scale variations in seismic properties near the top of the inner core.

  6. Numerical Heat Transfer Model for a Heat-Barrier-Piston Engine with Hypergolic Combustion.

    DTIC Science & Technology

    1986-02-01

    MODEL FOR A HEAT-BARRIER-PISTON ENGINE WITH I HYPERGOLIC COMBUSTION David A. Blank, LCD. , USN UNITED STATES NAVAL ACADEMY Annapolis, MD 21402 February...1fflOMG STATEMENT 1 ^ELECTE I MAR 101986 Dub~ -- t I~ NUMERICAL HEAT TRANSFER MODEL FOR A 4 - HEAT-BARRIER-PISTON ENGINE WITH HYPERGOLI C COMBUSTION...COVERED Numerical Heat Transfer Model for a Heat- IIBarrier-Piston Engine with Hypergolic Combustion Progress, 19a2-1986 I. .29AFORMINC, ORG. REPORT

  7. Heat capacity, enthalpy of mixing, and thermal conductivity of Hg(1-x)Cd(x)Te pseudobinary melts

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua

    1986-01-01

    Heat capacity and enthalpy of mixing of Hg(1-x)Cd(x)Te pseudobinary melts were calculated assuming an associated solution model for the liquid phase. The thermal conductivity of the pseudobinary melts for x = 0, 0.05, 0.1, and 0.2 was then calculated from the heat capacity values and the experimental values of thermal diffusivity and density for these melts. The thermal conductivity for the pseudobinary solid solution is also discussed.

  8. Capillary Pumped Heat Transfer (CHT) Experiment

    NASA Technical Reports Server (NTRS)

    Hallinan, Kevin P.; Allen, J. S.

    1998-01-01

    The operation of Capillary Pumped Loops (CPL's) in low gravity has generally been unable to match ground-based performance. The reason for this poorer performance has been elusive. In order to investigate the behavior of a CPL in low-gravity, an idealized, glass CPL experiment was constructed. This experiment, known as the Capillary-driven Heat Transfer (CHT) experiment, was flown on board the Space Shuttle Columbia in July 1997 during the Microgravity Science Laboratory mission. During the conduct of the CHT experiment an unexpected failure mode was observed. This failure mode was a result of liquid collecting and then eventually bridging the vapor return line. With the vapor return line blocked, the condensate was unable to return to the evaporator and dry-out subsequently followed. The mechanism for this collection and bridging has been associated with long wavelength instabilities of the liquid film forming in the vapor return line. Analysis has shown that vapor line blockage in present generation CPL devices is inevitable. Additionally, previous low-gravity CPL tests have reported the presence of relatively low frequency pressure oscillations during erratic system performance. Analysis reveals that these pressure oscillations are in part a result of long wavelength instabilities present in the evaporator pores, which likewise lead to liquid bridging and vapor entrapment in the porous media. Subsequent evaporation to the trapped vapor increases the vapor pressure. Eventually the vapor pressure causes ejection of the bridged liquid. Recoil stresses depress the meniscus, the vapor pressure rapidly increases, and the heated surface cools. The process then repeats with regularity.

  9. Two dimensional finite element heat transfer models for softwood

    Treesearch

    Hongmei Gu; John F. Hunt

    2004-01-01

    The anisotropy of wood creates a complex problem for solving heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential directions and have not differentiated the effects of cellular alignment, earlywood/latewood...

  10. Improving Heat Transfer Performance of Printed Circuit Boards

    NASA Technical Reports Server (NTRS)

    Schatzel, Donald V.

    2009-01-01

    This paper will explore the ability of printed circuit boards laminated with a Carbon Core Laminate to transfer heat vs. standard printed circuit boards that use only thick layers of copper. The paper will compare the differences in heat transfer performance of printed circuit boards with and without CCL.

  11. Improving Heat Transfer Performance of Printed Circuit Boards

    NASA Technical Reports Server (NTRS)

    Schatzel, Donald V.

    2009-01-01

    This paper will explore the ability of printed circuit boards laminated with a Carbon Core Laminate to transfer heat vs. standard printed circuit boards that use only thick layers of copper. The paper will compare the differences in heat transfer performance of printed circuit boards with and without CCL.

  12. Mixed convection heat transfer in concave and convex channels

    SciTech Connect

    Moukalled, F.; Doughan, A.; Acharya, S.

    1997-07-01

    Mixed convection heat transfer studies in the literature have been primarily confined to pipe and rectangular channel geometry's. In some applications, however, heat transfer in curved channels may be of interest (e.g., nozzle and diffuser shaped passages in HVAC systems, fume hoods, chimneys, bell-shaped or dome-shaped chemical reactors, etc.). A numerical investigation of laminar mixed convection heat transfer of air in concave and convex channels is presented. Six different channel aspects ratios (R/L = 1.04, 1.25, 2.5, 5, 10, and {infinity}) and five different values of Gr/Re{sup 2} (Gr/Re{sup 2} = 0, 0.1, 1, 3, 5) are considered. Results are displayed in terms of streamline and isotherm plots, velocity and temperature profiles, and local and average Nusselt number estimates. Numerical predictions reveal that compared to straight channels of equal height, concave channels of low aspect ratio have lower heat transfer at relatively low values of Gr/Re{sup 2} and higher heat transfer at high values of Gr/Re{sup 2}. When compared to straight channels of equal heated length, concave channels are always found to have lower heat transfer and for all values of Gr/Re{sup 2}. On the other hand, predictions for convex channels revealed enhancement in heat transfer compared to straight channels of equal height and/or equal heated length for all values of Gr/Re{sup 2}.

  13. Influence of oscillation-induced diffusion on heat transfer in a uniformly heated channel

    SciTech Connect

    Siegel, R. )

    1987-02-01

    The purpose of this note is to show that, for forced convection in slow laminar flow in a channel with uniform heat addition, the effect of flow oscillation will be to reduce the channel heat transfer coefficient. This is becausethe heat addition along the channel wall produces an increasing fluid temperature along the channel length. The flow oscillations interacting with this positive temperature gradient will induce a heat flow back toward the channel inlet. This will tend to inhibit the heat transfer process and will raise the wall temperature required to transfer away a given amount of heating at the channel wall.

  14. An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

    SciTech Connect

    Boyer, B.D.; Parlatan, Y.; Slovik, G.C.

    1995-09-01

    RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations at these conditions were compared with the GIRAFFE data. The effects of PCCS cell noding on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {plus_minus}5% of the data with a three--node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.

  15. Heat transfer characteristics of a linear solar collector.

    PubMed

    Seraphin, B O

    1973-02-01

    The heat transfer characteristics of a linear solar energy collector are calculated as functions of dimensions, spectral quality of the selective absorber surface, optical flux concentration of the optical configuration, and thermal parameters and flow rate of the heat transfer medium. Carnot efficiency, exit temperature, and an upper limit to the amount of heat extracted are determined for systems in which liquid sodium serves as the heat transfer medium. The performance is evaluated for selective absorber surfaces representing the state of the art as well as for surfaces requiring a more mature thin-film technology.

  16. Simultaneous velocity-surface heat transfer behavior of turbulent spots

    NASA Astrophysics Data System (ADS)

    Sabatino, D.; Smith, C. R.

    2002-06-01

    The properties of artificially initiated turbulent spots in a heated laminar boundary layer were investigated in a water channel facility. The instantaneous velocity field and surface heat transfer were determined simultaneously over a temporal sequence using a technique that combines traditional particle image velocimetry and thermochromic liquid crystal temperature measurements. The correlated results indicate that the highest surface heat transfer occurs in the trailing region of the spot where only the near-wall fluid is energetic. The results suggest that the "body" of the spot entrains, and subsequently recirculates, warm surface fluid within the spot, which reduces the effective heat transfer.

  17. Fem Formulation of Coupled Partial Differential Equations for Heat Transfer

    NASA Astrophysics Data System (ADS)

    Ameer Ahamad, N.; Soudagar, Manzoor Elahi M.; Kamangar, Sarfaraz; Anjum Badruddin, Irfan

    2017-08-01

    Heat Transfer in any field plays an important role for transfer of energy from one region to another region. The heat transfer in porous medium can be simulated with the help of two partial differential equations. These equations need an alternate and relatively easy method due to complexity of the phenomenon involved. This article is dedicated to discuss the finite element formulation of heat transfer in porous medium in Cartesian coordinates. A triangular element is considered to discretize the governing partial differential equations and matrix equations are developed for 3 nodes of element. Iterative approach is used for the two sets of matrix equations involved representing two partial differential equations.

  18. Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel

    NASA Technical Reports Server (NTRS)

    Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo; Woodiga, Sudesh

    2012-01-01

    This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.

  19. Experimental study of heat transfer to falling liquid films

    NASA Astrophysics Data System (ADS)

    Fagerholm, N. E.; Kivioja, K.; Ghazanfari, A. R.; Jaervinen, E.

    1985-12-01

    This project was initiated in order to obtain more knowledge about thermal design of falling film heat exchangers and to find methods to improve heat transfer in film flow. A short literature survey of film flow characteristics and heat transfer is presented. An experimental apparatus designed and built for studying falling film evaporation is described. The first experiments were made with smooth Cu tube 25/22 mm and refrigerant R114 as evaporating liquid. A significant amount of droplet entrainment was observed during the tests. The measured average heat transfer coefficient varied from 1000 to 1800 W/m K when Re=1300 to 11000 respectively and when the transfer mode is surface evaporation. This could be predicted accurately with the experimental correlation of Chun and Seban. When nucleate boiling is dominant the heat transfer could be predicted well with pool boiling correlation of VDI-84.

  20. A review of NASA combustor and turbine heat transfer research

    NASA Technical Reports Server (NTRS)

    Rudey, R. A.; Graham, R. W.

    1984-01-01

    The thermal design of the combustor and turbine of a gas turbine engine poses a number of difficult heat transfer problems. The importance of improved prediction techniques becomes more critical in anticipation of future generations of gas turbine engines which will operate at higher cycle pressure and temperatures. Research which addresses many of the complex heat transfer processes holds promise for yielding significant improvements in prediction of metal temperatures. Such research involves several kinds of program including: (1) basic experiments which delineate the fundamental flow and heat transfer phenomena that occur in the hot sections of the gas turbine but at low enthalpy conditions; (2) analytical modeling of these flow and heat transfer phenomena which results from the physical insights gained in experimental research; and (3) verification of advanced prediction techniques in facilities which operate near the real engine thermodynamic conditions. In this paper, key elements of the NASA program which involves turbine and combustor heat transfer research will be described and discussed.

  1. Heat transfer between elastic solids with randomly rough surfaces.

    PubMed

    Volokitin, A I; Lorenz, B; Persson, B N J

    2010-01-01

    We study the heat transfer between elastic solids with randomly rough surfaces.We include both the heat transfer from the area of real contact, and the heat transfer between the surfaces in the non-contact regions.We apply a recently developed contact mechanics theory, which accounts for the hierarchical nature of the contact between solids with roughness on many different length scales. For elastic contact, at the highest (atomic) resolution the area of real contact typically consists of atomic (nanometer) sized regions, and we discuss the implications of this for the heat transfer. For solids with very smooth surfaces, as is typical in many modern engineering applications, the interfacial separation in the non-contact regions will be very small, and for this case we show the importance of the radiative heat transfer associated with the evanescent electromagnetic waves which exist outside of all bodies.

  2. Improved superconducting properties of melt-textured Nd123 by additional heat treatment

    NASA Astrophysics Data System (ADS)

    Chikumoto, N.; Yoshioka, J.; Murakami, M.

    1997-02-01

    We have investigated the effect of additional heat-treatment on the superconducting transition and the flux pinning properties of NdBaCuO melt-textured in air. After the heat-treatment at high temperatures, >900°C, under low oxygen partial pressure, P(O 2) = 0.001 atm, the superconducting transition became sharper accompanied by an increase of Jc. However, the increase of Jc was very small and the secondary peak effect commonly observed in NdBaCuO melt textured in low P(O 2) could not be observed. Transmission electron microscopic observations and energy dispersive X-ray analyses show that the spatial variation of the Nd/Ba ratio is reduced after high-temperature heat-treatment, which indicates that an improvement in Tc and Jc is attributed to a suppression of Nd substitution on the Ba site.

  3. Heat transfer in a longitudinal glow discharge

    NASA Astrophysics Data System (ADS)

    Yunusov, R. F.

    2017-01-01

    This article is devoted to the experimental study of heat transfer in a longitudinal glow discharge. The discharge was ignited in the discharge chamber (DC), consisting of a glass tube 10 mm in diameter and two electrodes. Copper electrodes were placed in the side branches, so that the average distance between them was 9 cm. The discharge pressure was varied in the range of P = (2.5 – 8.5) kPa. The air flow rate was varied from zero to G = 0.06 g / s. Current was varied in the range of I = (30-80) mA. Current-voltage characteristics of the discharge had falling form, and the voltage was varied in the range of U = (1-2) kV. The temperature of neutral particles in the plasma glow discharge was measured by six thermocouples, which were insertedon radius of DC. The aim of the article was to compare achieved experiment data with theoretical studies: recombination and diffusion plasma models.

  4. Dual circuit embossed sheet heat transfer panel

    DOEpatents

    Morgan, G.D.

    1984-02-21

    A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet. 6 figs.

  5. Dual circuit embossed sheet heat transfer panel

    DOEpatents

    Morgan, Grover D.

    1984-01-01

    A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet.

  6. Melting and crystallization of nanocrystalline silicon microwires through rapid self-heating

    NASA Astrophysics Data System (ADS)

    Bakan, G.; Cywar, A.; Silva, H.; Gokirmak, A.

    2009-06-01

    Nanocrystalline silicon microwires are self-heated through single, large amplitude, and microsecond voltage pulses. Scanning electron micrographs show very smooth wire surfaces after the voltage pulse compared to as-fabricated nanocrystalline texture. Voltage-pulse induced self-heating leads to significant conductance improvement, suggesting crystallization of the wires. The minimum resistivity during the pulse is extracted from wires of different dimensions as 75.0±4.6 μΩ cm, matching previously reported values for liquid silicon. Hence, nanocrystalline silicon microwires melt through self-heating during the voltage pulse and resolidify upon termination of the pulse, resulting in very smooth and less-resistive crystalline structures.

  7. Conjugate heat transfer with the entropic lattice Boltzmann method.

    PubMed

    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.

  8. Lava-substrate heat transfer: Laboratory experiments and thermodynamic modeling

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We have performed laboratory experiments and numerical modeling to investigate the heat transfer from a lava flow into various substrate materials, focusing on the effects of the differing thermophysical properties of substrate materials. Initial motivation for this project developed from the desire to understand the loss of solar wind volatiles embedded in lunar regolith deposits that were subsequently covered by a lava flow. The Moon lacks a significant atmosphere and magnetosphere, leaving the surface regolith exposed to bombardment by solar flare and solar wind particles, and by the cosmogenic products of galactic cosmic rays. Preservation of particle-rich regolith deposits may have occurred by the emplacement of an active lava flow on top of the regolith layer, provided the embedded particles survive heating by the lava. During future expeditions to the lunar surface, ancient regolith deposits could be sampled through surface drilling to extract the extra-lunar particles, revealing a history of the solar activity and galactic events not available on the Earth. This project also has important implications for terrestrial lava flows, particularly in the prediction of lava flow hazards. Lava erupted on Earth may be emplaced on various substrates, including solid lava rock, volcanic tephra, sands, soils, etc. The composition, grain size, consolidation, moisture content, etc. of these materials will vary greatly and have different effects on the cooling of the flow. Accounting for specific properties of the substrate could be an important improvement in lava flow models We have performed laboratory experiments in collaboration with the Department of Art and Art History at the University of Hawaii at Manoa in which ~5-6 kg of basalt, collected at Kilauea Volcano, Hawaii, is melted to ~1200 °C. The lava is poured into a device constructed of calcium silicate sheeting that has been filled with a solid or particulate substrate material and embedded with thermocouples

  9. Amplification of the snow melting effect on the heat wave over the Eurasia by absorbing aerosols

    NASA Astrophysics Data System (ADS)

    Kim, M. K.; Kim, K. M.; Lau, W. K. M.; Sang, J.; Yasunari, T. J.

    2015-12-01

    In this study, we present the potential impact of snow darkening effect on the Eurasian heat wave by absorbing aerosols using the NASA GEOS-5 Model experiments with aerosol tracers and a state-of-the-art snow darkening module for the land surface. Results show that snow darkening effect (SDE) can have a significant influence on not only the intensity but also the duration of heatwave during snow melting season, i.e., late spring season over the mid-western Eurasia and early summer season over the central northern Eurasia. During the early snow melting season surface air temperature is significantly increased by 3-6K due to early snow melting and enhanced solar radiation. Moreover enhanced evaporation induced by surface energy surplus during the early melting season leads to the new equilibrium level with lower soil moisture over the Eurasia since snow melting season, and thereby provide favorable condition for severe droughts and heat wave over the large parts of the Eurasia. This finding suggests that the SDE may play an important role in amplifying the snow melting effect on large-scale heat wave over the Eurasia. Energy and water balance at the surface supporting this findings are also discussed from evaporation-precipitation recycling point of view.

  10. Consistent melting behavior induced by Joule heating between Ag microwire and nanowire meshes

    PubMed Central

    2014-01-01

    The melting behavior of an Ag microwire mesh induced by Joule heating was numerically investigated and compared with that of the corresponding Ag nanowire mesh with the same structure but different geometrical and physical properties of the wire itself. According to the relationship of melting current and melting voltage during the melting process, a similar repetitive zigzag pattern in melting behavior was discovered in both meshes. On this basis, a dimensionless parameter defined as figure of merit was proposed to characterize the current-carrying ability of the mesh. The consistent feature of figure of merit in both meshes indicates that the melting behavior of the Ag nanowire mesh can be predicted from the present results of the corresponding Ag microwire mesh with the same structure but made from a different wire (e.g., different size, different material) through simple conversion. The present findings can provide fundamental insight into the reliability analysis on the metallic nanowire mesh-based transparent conductive electrode. PMID:24910578

  11. Evaporation and Accompanying Isotopic Fractionation of Sulfur from FE-S Melt During Shock Wave Heating

    NASA Technical Reports Server (NTRS)

    Tachibana, S.; Huss, G. R.; Miura, H.; Nakamoto, T.

    2004-01-01

    Chondrules probably formed by melting and subsequent cooling of solid precursors. Evaporation during chondrule melting may have resulted in depletion of volatile elements in chondrules. It is known that kinetic evaporation, especially evaporation from a melt, often leads to enrichment of heavy isotopes in an evaporation residue. However, no evidence for a large degree of heavy-isotope enrichment has been reported in chondrules for K, Mg, Si, and Fe (as FeO). The lack of isotopic fractionation has also been found for sulfur in troilites (FeS) within Bishunpur (LL3.1) and Semarkona (LL3.0) chondrules by an ion microprobe study. The largest fractionation, found in only one grain, was 2.7 +/- 1.4 %/amu, while all other troilite grains showed isotopic fractionations of <1 %/amu. The suppressed isotopic fractionation has been interpreted as results of (i) rapid heating of precursors at temperatures below the silicate solidus and (ii) diffusion-controlled evaporation through a surrounding silicate melt at temperatures above the silicate solidus. The kinetic evaporation model suggests that a rapid heating rate of >10(exp 4)-10(exp 6) K/h for a temperature range of 1000-1300 C is required to explain observed isotopic fractionations. Such a rapid heating rate seems to be difficult to be achieved in the X-wind model, but can be achieved in shock wave heating models. In this study, we have applied the sulfur evaporation model to the shock wave heating conditions of to evaluate evaporation of sulfur and accompanying isotopic fractionation during shock wave heating at temperatures below the silicate solidus.

  12. Evaporation and Accompanying Isotopic Fractionation of Sulfur from FE-S Melt During Shock Wave Heating

    NASA Technical Reports Server (NTRS)

    Tachibana, S.; Huss, G. R.; Miura, H.; Nakamoto, T.

    2004-01-01

    Chondrules probably formed by melting and subsequent cooling of solid precursors. Evaporation during chondrule melting may have resulted in depletion of volatile elements in chondrules. It is known that kinetic evaporation, especially evaporation from a melt, often leads to enrichment of heavy isotopes in an evaporation residue. However, no evidence for a large degree of heavy-isotope enrichment has been reported in chondrules for K, Mg, Si, and Fe (as FeO). The lack of isotopic fractionation has also been found for sulfur in troilites (FeS) within Bishunpur (LL3.1) and Semarkona (LL3.0) chondrules by an ion microprobe study. The largest fractionation, found in only one grain, was 2.7 +/- 1.4 %/amu, while all other troilite grains showed isotopic fractionations of <1 %/amu. The suppressed isotopic fractionation has been interpreted as results of (i) rapid heating of precursors at temperatures below the silicate solidus and (ii) diffusion-controlled evaporation through a surrounding silicate melt at temperatures above the silicate solidus. The kinetic evaporation model suggests that a rapid heating rate of >10(exp 4)-10(exp 6) K/h for a temperature range of 1000-1300 C is required to explain observed isotopic fractionations. Such a rapid heating rate seems to be difficult to be achieved in the X-wind model, but can be achieved in shock wave heating models. In this study, we have applied the sulfur evaporation model to the shock wave heating conditions of to evaluate evaporation of sulfur and accompanying isotopic fractionation during shock wave heating at temperatures below the silicate solidus.

  13. Heat transfer during quenching of modified and unmodified gravity die-cast A357 cylindrical bars

    NASA Astrophysics Data System (ADS)

    Prabhu, K. N.; Hemanna, P.

    2006-06-01

    Heat transfer during quenching of chill-cast modified and unmodified A357 Al-Si alloy was examined using a computer-aided cooling curve analysis. Water at 60 °C and a vegetable oil (palm oil) were used as quench media. The measured temperatures inside cylindrical probes of the A357 alloy were used as inputs in an inverse heat-conduction model to estimate heat flux transients at the probe/quenchant interface and the surface temperature of the probe in contact with the quench medium. It was observed that modified alloy probes yielded higher cooling rates and heat flux transients. The investigation clearly showed that the heat transfer during quenching depends on the casting history. The increase in the cooling rate and peak heat flux was attributed to the increase in the thermal conductivity of the material on modification melt treatment owing to the change in silicon morphology. Fine and fibrous silicon particles in modified A357 probes increase the conductance of the probe resulting in higher heat transfer rates. This was confirmed by measuring the electrical conductivity of modified samples, which were found to be higher than those of unmodified samples. The ultrasound velocity in the probes decreased on modification.

  14. Promotion of melt-assisted growth in Bi-2223 tapes utilizing rapid heating rates

    NASA Astrophysics Data System (ADS)

    Avgeros, S.; Al-Mosawi, M.; Young, E. A.; Yang, Y.

    2005-04-01

    Recent differential thermal analysis studies on green Bi-2223 tapes showed two phase transitions, with onset temperatures 800 and 820 °C. From microstructural examination of the long-term phase formation in the tapes the higher temperature endotherm was associated with a partial melt. In this study it is demonstrated how control of the heating rate can promote the partial melt (characterized by DTA), and thereby improve the transport current, Ic. XRD, SEM and transport measurements in field show microstructure features typical of an increased volume of liquid phase: a reduction in secondary phase volume and pores with a corresponding increase in c-plane texture.

  15. Melting of nanocrystals embedded in a crystal matrix heated by nanosecond laser pulses

    SciTech Connect

    Zinoviev, V. A. Dvurechenskii, A. V.; Smagina, Zh. V.; Ivlev, G. D.; Gatskevich, E. I.; Malevich, V. L.

    2012-09-15

    The kinetics of phase transformations of nanocrystals in a crystal matrix is considered upon non-stationary heating by laser pulses. The melting and crystallization kinetics of nanocrystals is described taking into account their size, shape, elemental composition, and elastic deformations appearing due to the mismatch of the lattice constants for nanocrystals and the matrix. The possibility of decreasing the dispersion of nanocrystals over their size in heterostructures with quantum dots is predicted. As an example, melting of Ge nanocrystals in a Si matrix is considered.

  16. Heat Transfer Analysis of the NAHBE Piston Cap,

    DTIC Science & Technology

    1977-09-01

    r~~~ U____________ ____s HEAT TRANSFER ANALYSIS :~ OF THE NAHBE PISTON CAP* Engineering and Wea pons Report EW-l1—77...transfer variations in thecap of a nodified piston engine (NN~BE) was made. The objective was to estimatethe regenerative heating effect d~e to the cap...ABSTRACT The piston modification for the NAHBE (Naval Academy Heat Bal ance Engine ) consists of a cap which extends above the standard piston used

  17. Applications of Infrared Thermography in Convective Heat Transfer.

    DTIC Science & Technology

    1986-03-01

    INFRARED THERMOGRAPHY IN CONVECTIVE HEAT TRANSFER by Timothy M. SpenceVX March 1986 Thesis Advisor: R.H. Nunn Approved for public release...Include Security Classfication) APPLICATIONS OF INFRARED THERMOGRAPHY IN CONVECTIVE HEAT TRANSFER !2 PERSONAL AUTHOR(S) Spence, Timothy M. 𔃽a TYPE...I18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number) P:ELD GROUP SUB-GROUP Infrared Thermography ; TVC Convective Heat

  18. Laser Measurement Of Convective-Heat-Transfer Coefficient

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

    1994-01-01

    Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

  19. Heat transfer from aluminum surfaces to pool boiling He I

    SciTech Connect

    Huang, Y.; Van Sciver, S.W.

    1996-12-31

    Heat transfer measurements between different aluminum surfaces and pool boiling He I at 4.21 K are reported. The samples are contained in a channel configuration similar to what might be found in a large bath cooled superconducting magnet. Results include heat transfer coefficients in the nucleate and film boiling regimes as well as values for the peak nucleate and minimum film boiling heat flux. The effects of sample orientation and surface condition are also studied.

  20. Predicting spacecraft multilayer insulation performance from heat transfer measurements

    NASA Technical Reports Server (NTRS)

    Stimpson, L. D.; Hagemeyer, W. A.

    1974-01-01

    Multilayer insulation (MLI) ideally consists of a series of radiation shields with low-conductivity spacers. When MLI blankets were installed on cryogenic tanks or spacecraft, a large discrepancy between the calorimeter measurements and the performance of the installed blankets was discovered. It was found that discontinuities such as exposed edges coupled with high lateral heat transfer created 'heat leaks' which overshadowed the basic heat transfer of the insulation. Approaches leading to improved performance predictions of MLI units are discussed.

  1. Laser Measurement Of Convective-Heat-Transfer Coefficient

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

    1994-01-01

    Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

  2. 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.

  3. Three-Dimensional Modelling of Heat Transfer from Slab Floors

    DTIC Science & Technology

    1989-07-01

    a general change in heat transfer rate. Effects of thermal diffusivity, and lower boundary condition variation were small (on the order of 10%) for...ground surface conditions, foundation design, and floor shape/size are esseatial elcmnts rf a general change in heat transfer rate. N.Effec es of...11 5 111-12. Change in floor heat loss due to substitution of zero flux lower boundary for fixed temperature lower

  4. Enhanced two phase flow in heat transfer systems

    DOEpatents

    Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D

    2013-12-03

    A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.

  5. Some observations on the historical development of conduction heat transfer

    NASA Astrophysics Data System (ADS)

    Cheng, Kwo Chang

    An attempt is made to obtain historical perspectives on the development of the mathematical theory of heat conduction considering Newton's law of cooling (1701) and its close connection with Fourier's work from 1807 to 1822 resulting in his epoch-making treatise on "The Analytical Theory of Heat". Fourier was the principal architect of the heat conduction theory. Fourier's work established a new methodology for the formulation and solution of physical problems, based on partial differential equations and marked a major turning point in the history of physics. The developments in the periods 1822 to 1900 and 1900 to 1950 are also briefly reviewed as are the classical (analytical) and numerical methods of solution for heat conduction problems. The analogy in heat, momentum, and mass transfer for transport phenomena is discussed. A list of recent conduction heat transfer books is presented to show the scope of recent developments. Some observations on conduction heat transfer are noted.

  6. Heat transfer to the adsorbent in solar adsorption cooling device

    NASA Astrophysics Data System (ADS)

    Pilat, Peter; Patsch, Marek; Papucik, Stefan; Vantuch, Martin

    2014-08-01

    The article deals with design and construction of solar adsorption cooling device and with heat transfer problem in adsorber. The most important part of adsorption cooling system is adsorber/desorber containing adsorbent. Zeolith (adsorbent) type was chosen for its high adsorption capacity, like a coolant was used water. In adsorber/desorber occur, at heating of adsorbent, to heat transfer from heat change medium to the adsorbent. The time required for heating of adsorber filling is very important, because on it depend flexibility of cooling system. Zeolith has a large thermal resistance, therefore it had to be adapted the design and construction of adsorber. As the best shows the tube type of adsorber with double coat construction. By this construction is ensured thin layer of adsorbent and heating is quick in all volume of adsorbent. The process of heat transfer was experimentally measured, but for comparison simulated in ANSYS, too.

  7. The numerical simulation of heat transfer during a hybrid laser-MIG welding using equivalent heat source approach

    NASA Astrophysics Data System (ADS)

    Bendaoud, Issam; Matteï, Simone; Cicala, Eugen; Tomashchuk, Iryna; Andrzejewski, Henri; Sallamand, Pierre; Mathieu, Alexandre; Bouchaud, Fréderic

    2014-03-01

    The present study is dedicated to the numerical simulation of an industrial case of hybrid laser-MIG welding of high thickness duplex steel UR2507Cu with Y-shaped chamfer geometry. It consists in simulation of heat transfer phenomena using heat equivalent source approach and implementing in finite element software COMSOL Multiphysics. A numerical exploratory designs method is used to identify the heat sources parameters in order to obtain a minimal required difference between the numerical results and the experiment which are the shape of the welded zone and the temperature evolution in different locations. The obtained results were found in good correspondence with experiment, both for melted zone shape and thermal history.

  8. Anode heat transfer in a constricted tube arc.

    NASA Technical Reports Server (NTRS)

    Lukens, L. A.; Incropera, F. P.

    1971-01-01

    The complex energy exchange mechanisms occurring on the most severely heated component of an arc constrictor, the anode, have been investigated. Measurements performed to determine the anode heat flux for a cascade, atmospheric argon arc of the Maecker type are described. The results are used to check the validity of an existing anode heat transfer model.

  9. Two-Dimensional Heat Transfer in a Heterogeneous Fracture Network

    NASA Astrophysics Data System (ADS)

    Gisladottir, V. R.; Roubinet, D.; Tartakovsky, D. M.

    2015-12-01

    Geothermal energy harvesting requires extraction and injection of geothermal fluid. Doing so in an optimal way requires a quantitative understanding of site-specific heat transfer between geothermal fluid and the ambient rock. We develop a heat transfer particle-tracking approach to model that interaction. Fracture-network models of heat transfer in fractured rock explicitly account for the presence of individual fractures, ambient rock matrix, and fracture-matrix interfaces. Computational domains of such models span the meter scale, whereas fracture apertures are on the millimeter scale. The computations needed to model these multi-scale phenomenon can be prohibitively expensive, even for methods using nonuniform meshes. Our approach appreciably decreases the computational costs. Current particle-tracking methods usually assume both infinite matrix and one-dimensional (1D) heat transfer in the matrix blocks. They rely on 1D analytical solutions for heat transfer in a single fracture, which can lead to large predictive errors. Our two-dimensional (2D) heat transfer simulation algorithm is mesh-free and takes into account both longitudinal and transversal heat conduction in the matrix. It uses a probabilistic model to transfer particle to the appropriate neighboring fracture unless it returns to the fracture of origin or remains in the matrix. We use this approach to look at the impact of a fracture-network topology (e.g. the importance of smaller scale fractures), as well as the matrix block distribution on the heat transport in heterogeneous fractured rocks.

  10. Enhanced heat transfer in the entrance region of microchannels

    SciTech Connect

    Gui, F.; Scaringe, R.P.

    1995-12-31

    A detailed heat transfer analysis has been performed on the data from previously-reported experiments (Rahman and Gui 1993) to investigate the characteristics of high-heat-flux (10{sup 6} W/m{sup 2}) microchannel cooling in electronic chips. The use of microchannel directly etched into a silicon wafer has shortened the cooling path and improved the performance by significantly minimizing the thickness of the heat transfer layer. Experimental convective heat transfer coefficients (up to 45 kW/m{sup 2} K) for low temperature single-phase flow was an order of magnitude higher than conventional heat transfer coefficients; and reached the level of two-phase boiling heat transfer. The flow and heat transfer modes and their transitions in the experiments were investigated. The influence of the microchannel passage geometry, fluid property variation, and the fluid flow mode on the local Nusselt number in the entrance region of the microchannel has been analyzed. The analysis indicates that the significant enhancement obtained in microchannel cooling results from four key aspects: a thinner thermal boundary layer, entry effects, the roughness of the channel, and strong pre-existing turbulence at the inlet. The preexisting turbulence delayed the formation of the thermal boundaries, thereby increasing the entry effects on heat transfer. The critical Re shifted from 2,300 to 1,400 in microchannels, possibly due to the wall roughness which does not affect the Re{sub c} otherwise in normal size tubes.

  11. CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

    NASA Technical Reports Server (NTRS)

    Yang, H. Q.; West, Jeff

    2015-01-01

    Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

  12. Efficient Heat and Mass Transfer Formulations for Oil Shale Retorting

    NASA Astrophysics Data System (ADS)

    Parker, J. C.; Zhang, F.

    2007-12-01

    A mathematical model for oil shale retorting is described that considers kerogen pyrolysis, oil coking, residual carbon gasification, carbonate mineral decomposition, water-gas shift, and phase equilibria reaction. Reaction rate temperature-dependence is described by Arrhenius kinetics. Fractured rock is modeled as a bi-continuum consisting of fracture porosity in which advective and dispersive gas and heat transport occur, and rock matrix in which diffusive mass transport and thermal conduction occur. Heat transfer between fracture and matrix regions is modeled either by a partial differential equation for spherical conduction or by a linear first-order heat transfer formulation. Mass transfer is modeled in an analogous manner or assuming local equilibrium. First-order mass and heat transfer coefficients are computed by a theoretical model from fundamental rock matrix properties. The governing equations are solved using a 3-D finite element formulation. Simulations of laboratory retort experiments and hypothetical problems indicated thermal disequilibrium to be the dominant factor controlling retort reactions. Simulation accuracy was unaffected by choice of mass transfer formulation. However, computational effort to explicitly simulate diffusive mass transfer in the rock matrix increased computational effort by more than an order of magnitude compared with first-order mass transfer or equilibrium analyses. A first-order heat transfer approximation of thermal conduction can be used without significant loss of accuracy if the block size and/or heating rate are not too large, as quantified by a proposed dimensionless heating rate.

  13. Simulation of Heat Transfer of Heating-System and Water Pipelines Under Northern Conditions

    NASA Astrophysics Data System (ADS)

    Stepanov, A. V.; Egorova, G. N.

    2016-09-01

    A mathematical model of joint laying of water pipelines and of city-block heating-system pipelines is considered. The effect of radiation on the process of combined heat transfer in the heat insulation jacket between the construction elements is investigated. The results of mathematical simulation of heat losses with account of the radiant component are given.

  14. Experimental and numerical investigation of heat transfer in a miniature heat sink utilizing silica nanofluid

    NASA Astrophysics Data System (ADS)

    Fazeli, Seyyed Abdolreza; Hosseini Hashemi, Seyyed Mohammad; Zirakzadeh, Hootan; Ashjaee, Mehdi

    2012-02-01

    In this paper, heat transfer characteristics of a miniature heat sink cooled by SiO 2-water nanofluids were investigated both experimentally and numerically. The heat sink was fabricated from aluminum and insulated by plexiglass cover plates. The heat sink consisted of an array of 4 mm diameter circular channels with a length of 40 mm. Tests were performed while inserting a 180 W/cm 2 heat flux to the bottom of heat sink and Reynolds numbers ranged from 400 to 2000. The three-dimensional heat transfer characteristics of the heat sink were analyzed numerically by solving conjugate heat transfer problem of thermally and hydrodynamically developing fluid flow. Experimental results showed that dispersing SiO 2 nanoparticles in water significantly increased the overall heat transfer coefficient while thermal resistance of heat sink was decreased up to 10%. Numerical results revealed that channel diameter, as well as heat sink height and number of channels in a heat sink have significant effects on the maximum temperature of heat sink. Finally, an artificial neural network (ANN) was used to simulate the heat sink performance based on these parameters. It was found that the results of ANN are in excellent agreement with the mathematical simulation and cover a wider range for evaluation of heat sink performance.

  15. Control of melt-crystal interface shape during sapphire crystal growth by heat exchanger method

    NASA Astrophysics Data System (ADS)

    Wu, Ming; Liu, Lijun; Ma, Wencheng

    2017-09-01

    We numerically investigate the melt-crystal interface shape during the early stage of the solidification process when the crystal diameter increases. The contact angle between the melt-crystal interface and the crucible bottom wall is found obtuse during this stage, which is unfavorable for the crystal quality. We found that the obtuse contact angle is caused by the thermal resistance difference between the sapphire crystal and melt as well as the insufficient cooling effect of the crucible bottom. Two approaches are proposed to suppress the obtuse contact angle. The first approach is to increase the emissivity of the outer surface of crucible bottom. The second approach is to install a heat shield near the crucible bottom. The reduction of the emissivity of the heat shield is also favorable for the suppression of the obtuse contact angle. Compared with the increase of the emissivity of the crucible bottom, the installation of a heat shield is a more effective approach to prevent the appearance of an obtuse contact angle for the sake of reliability since a molybdenum heat shield can be reused and will not induce other impurities.

  16. Effect of Melt Superheating Treatment on the Latent Heat Release of Sn

    NASA Astrophysics Data System (ADS)

    Xu, Junfeng; Dang, Bo; Fan, Dandan; Jian, Zengyun

    2017-03-01

    The accuracy of the baseline evaluation is of importance for calculating the transition enthalpy such as the latent heat of the crystallization. This study demonstrates the modified method of the equivalent non-latent heat baseline, by which the transition enthalpy can be measured accurately according to the transition peak in differential scanning calorimetric curve. With this method, the effect of melt superheating treatment time on the latent heat release upon the solidification of tin is investigated. The results show that the latent heat increases by increasing the treatment time, and is close to a constant when the treatment time is large enough, indicating the homogeneous system. And then, a simple model is established to describe the changes of the crystallization latent heat with the treatment time, which is confirmed by the experimental data of Sn.

  17. Effect of Melt Superheating Treatment on the Latent Heat Release of Sn

    NASA Astrophysics Data System (ADS)

    Xu, Junfeng; Dang, Bo; Fan, Dandan; Jian, Zengyun

    2016-12-01

    The accuracy of the baseline evaluation is of importance for calculating the transition enthalpy such as the latent heat of the crystallization. This study demonstrates the modified method of the equivalent non-latent heat baseline, by which the transition enthalpy can be measured accurately according to the transition peak in differential scanning calorimetric curve. With this method, the effect of melt superheating treatment time on the latent heat release upon the solidification of tin is investigated. The results show that the latent heat increases by increasing the treatment time, and is close to a constant when the treatment time is large enough, indicating the homogeneous system. And then, a simple model is established to describe the changes of the crystallization latent heat with the treatment time, which is confirmed by the experimental data of Sn.

  18. Incorporation and distribution of rhenium in a borosilicate glass melt heat treated in a sealed ampoule

    SciTech Connect

    Kim, Dong-Sang; Schweiger, Michael J.

    2013-07-25

    We investigated a mass balance of rhenium (used as a surrogate for technetium-99) in a borosilicate glass that was mixed with excess Re source (KReO4) beyond its solubility and heat treated in a vacuum-sealed fused silica ampoule. Distribution of Re in the bulk of the glass, in a salt phase formed on the melt surface, and in condensate material deposited on the ampoule wall was evaluated to understand the Re migration into different phases during the reaction between the molten glass and KReO4. The information gained from this study will contribute to an effort to understand the mechanism of technetium retention in or escape from glass melt during early stages of glass batch melting, which is a goal of the present series of studies.

  19. Air-side flow and heat transfer in compact heat exchangers: A discussion of enhancement mechanisms

    SciTech Connect

    Jacobi, A.M.; Shah, R.K.

    1998-10-01

    The behavior of air flows in complex heat exchanger passages is reviewed with a focus on the heat transfer effects of boundary-layer development, turbulence, spanwise and streamwise vortices, and wake management. Each of these flow features is discussed for the plain, wavy, and interrupted passages found in contemporary compact heat exchanger designs. Results from the literature are used to help explain the role of these mechanisms in heat transfer enhancement strategies.

  20. Heat transfer during heat sterilization and cooling processes of canned products

    NASA Astrophysics Data System (ADS)

    Dincer, I.

    In this paper, an analysis of transient heat transfer during heat sterilization and cooling processes of a cylindrical canned product is presented. In the analysis, most practical case including the boundary condition of third kind (i.e., convection boundary condition, leading to 0.1 <= Bi <= 100) was employed. A simple analytical model for determining effective heat transfer coefficients for such products is developed. For the heat sterilization process, heating coefficient is incorporated into heat transfer coefficient model. An experimental study was performed to measure the thermal center temperatures of the short-cylindrical canned products (i.e., Tuna fish) during heat sterilization at the retort medium temperatures of 115∘C and 121∘C, and during cooling process at 16∘C. The effective heat transfer coefficient model used the experimental temperature data. Using these effective heat transfer coefficients the center temperature distributions were calculated and compared with the experimental temperature distributions. Agreement was found considerably high. The results of the present study indicate that the heat-transfer analysis technique and heat-transfer coefficient model are reliable, and can provide accurate results for such problems.

  1. Heat transfer during the boiling of liquids in heat pipe wicks

    NASA Technical Reports Server (NTRS)

    Gontarev, Yu. K.; Navruzov, Yu. V.; Prisnyakov, V. F.; Serebryanskiy, N.

    1987-01-01

    Data in the literature on heat transfer in the case of nucleate boiling of various liquids in the wicks of heat pipes are reviewed. It is shown that none of the known analytical relationships can be used to generalize, with sufficient accuracy, the experimental data found in the literature. It is further shown that the exponent of the specific heat flux in the heat transfer law changes as a function of the liquid and wick properties. A relationship is obtained which generalizes experimental data for heat transfer agents of moderate temperatures (water, acetone, ethanol, and R-11 and R-113 coolants) and ammonia.

  2. A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.

    PubMed

    de Jong, J A; Wijnant, Y H; de Boer, A

    2014-03-01

    A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.

  3. Numerical Modeling of Freezing and Melting Processes around a Borehole Heat Exchanger

    NASA Astrophysics Data System (ADS)

    Shao, Haibing; Zheng, Tianyuan; Nagel, Thomas; Kolditz, Olaf

    2015-04-01

    In ground sourced heat pump (GSHP) systems, heat energy stored in the shallow subsurface is extracted through borehole heat exchangers (BHE) and then utilized for domestic heating. In cold regions, the continuous heat deficit in the vicinity of the BHE can cause freezing of the surrounding soil. Its material properties, such as permeability and heat conductivity, will then significantly change and lead to a series of coupled thermal, hydraulic, and mechanical processes. In particular, the heat exchange performance of the BHE will be altered, and the frozen soil may also induce ground lift or subsidence in the vicinity of the building. As the first step of modelling this coupled system, we followed the approach proposed by Al-Khoury et al (2010) and Diersch et al (2011), where the BHE has been fully integrated into the numerical model in a dual-continuum way. Additionally, we extended the existing heat transport module in the numerical simulator OpenGeoSys to include the freezing and melting processes, whereas the ice volume fraction in the soil is non-linearly dependent on the temperature, and the soil properties were determined based on the degree of freezing/melting. The non-linearity of the coupled model was numerically solved by a Newton scheme. The extended model has been verified by comparing numerical results against analytical solutions and also findings from other numerical codes. Moreover, we proposed and simulated a hypothetical scenario, where ice is gradually forming around a BHE in response to the continuous operation of a heat pump. The model is capable of reproducing the thermodynamic freezing process as well as the heat transport affected by it. Future work will be focused on the integration of deformation processes into the model.

  4. Radiative heat transfer in low-dimensional systems -- microscopic mode

    NASA Astrophysics Data System (ADS)

    Woods, Lilia; Phan, Anh; Drosdoff, David

    2013-03-01

    Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Financial support from the Department of Energy under Contract No. DE-FG02-06ER46297 is acknowledged.

  5. Heat transfer and flow characteristics on a gas turbine shroud.

    PubMed

    Obata, M; Kumada, M; Ijichi, N

    2001-05-01

    The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions.

  6. Heat Transfer For Subcooled Flow Boiling In Hypervapotron Configuration

    SciTech Connect

    Chena, Peipei; Wua, Wen; Jonesa, Barclay G.; Newell, Ty A

    2006-07-01

    This work reports on experimental studies that examine subcooled boiling on the enhanced heat transfer surface of hypervapotron structures. The use of simulant fluid (refrigerant R134a) instead of prototypic water allows examination of a full range of subcooled boiling, including up to critical heat flux (CHF). The experimental results are compared to Bjorge's model and Kandlikar's heat transfer correlation in the subcooled boiling region. It is found that the fully developed boiling curve has a slope of about 2.96 (q{sup {approx}} {delta}{sub sat} {sup 2}.{sup 96}), which shows good agreement with Bjorge's recognition for flat surface channels. In addition, Kandlikar's correlation is also able to predict the heat transfer coefficient for the range from net vapor generation (NVG) to the fully developed boiling region with acceptable accuracy. However, the heat transfer curve shows a significant deviation when subcooled boiling approaches CHF. (authors)

  7. Analysis of snowpack accumulation and the melting process of wet snow using a heat balance approach that emphasizes the role of underground heat flux

    NASA Astrophysics Data System (ADS)

    Maruyama, Toshisuke; Takimoto, Hiroshi; Ogura, Akira; Yoshida, Masashi

    2015-03-01

    Snowpack accumulation and melting, including the role of the heat flux underground, were investigated by employing the bulk transfer method and setting roughness lengths of ZO = ZT = 0.005 m and ZT = 0.007 m. Heat balance data were recorded for a period of 4 years, from the fall of 2009 to the spring of 2013, at a forest experiment station in the Hokuriku region, which lies along the Japan Sea. The findings of the research are as follows: (1) The observed temporal changes in the snowpack depth were well reproduced by our model using observed and estimated densities. (2) The importance and roles of the heat balance components were clarified. The total heat input during the 4 years was 252.2 MJ/m2 on average; 41.4% was provided by net radiation (Rn), 37.8% by sensible heat flux (H), and 13.2% by underground heat flux (G). The total output was 120.7 MJ/m2, of which 56.2% was accounted for by Rn and 31.1% by latent heat flux (lE). (3) Of the total heat input, 45.2% was released as freezing energy from the surface side and 2.6% was released from the bottom. (4) In the very cold season (December-February), the total input energy was 115.8 MJ/m2 on average; 75.0% was supplied by the surface and the remaining 25.0% from underground. In an anomalous year, 40.8% of the energy was supplied from underground.

  8. Origin of Self-preservation Effect for Hydrate Decomposition: Coupling of Mass and Heat Transfer Resistances

    NASA Astrophysics Data System (ADS)

    Bai, Dongsheng; Zhang, Diwei; Zhang, Xianren; Chen, Guangjin

    2015-10-01

    Gas hydrates could show an unexpected high stability at conditions out of thermodynamic equilibrium, which is called the self-preservation effect. The mechanism of the effect for methane hydrates is here investigated via molecular dynamics simulations, in which an NVT/E method is introduced to represent different levels of heat transfer resistance. Our simulations suggest a coupling between the mass transfer resistance and heat transfer resistance as the driving mechanism for self-preservation effect. We found that the hydrate is initially melted from the interface, and then a solid-like water layer with temperature-dependent structures is formed next to the hydrate interface that exhibits fractal feature, followed by an increase of mass transfer resistance for the diffusion of methane from hydrate region. Furthermore, our results indicate that heat transfer resistance is a more fundamental factor, since it facilitates the formation of the solid-like layer and hence inhibits the further dissociation of the hydrates. The self-preservation effect is found to be enhanced with the increase of pressure and particularly the decrease of temperature. Kinetic equations based on heat balance calculations is also developed to describe the self-preservation effect, which reproduces our simulation results well and provides an association between microscopic and macroscopic properties.

  9. Origin of Self-preservation Effect for Hydrate Decomposition: Coupling of Mass and Heat Transfer Resistances

    PubMed Central

    Bai, Dongsheng; Zhang, Diwei; Zhang, Xianren; Chen, Guangjin

    2015-01-01

    Gas hydrates could show an unexpected high stability at conditions out of thermodynamic equilibrium, which is called the self-preservation effect. The mechanism of the effect for methane hydrates is here investigated via molecular dynamics simulations, in which an NVT/E method is introduced to represent different levels of heat transfer resistance. Our simulations suggest a coupling between the mass transfer resistance and heat transfer resistance as the driving mechanism for self-preservation effect. We found that the hydrate is initially melted from the interface, and then a solid-like water layer with temperature-dependent structures is formed next to the hydrate interface that exhibits fractal feature, followed by an increase of mass transfer resistance for the diffusion of methane from hydrate region. Furthermore, our results indicate that heat transfer resistance is a more fundamental factor, since it facilitates the formation of the solid-like layer and hence inhibits the further dissociation of the hydrates. The self-preservation effect is found to be enhanced with the increase of pressure and particularly the decrease of temperature. Kinetic equations based on heat balance calculations is also developed to describe the self-preservation effect, which reproduces our simulation results well and provides an association between microscopic and macroscopic properties. PMID:26423519

  10. Heat transfer near spacer grids in rod bundles

    SciTech Connect

    Yoder, G.L.

    1985-01-01

    Heat transfer data from several sources have been assembled which show the effect of spacer grids on local heat transfer within a rod bundle. Both single phase (air and steam) data and two phase (steam/water) data show heat transfer augmentation in the grid region. Heat transfer improvement immediately beyond the grid ranges from a few percent to over fifty percent in these experiments, depending on flow conditions. The data are examined using several nondimensional parameters which relate the above effects to known quantities. The relative effect of the grid on local heat transfer is altered by both the Reynolds number and blockage ratio. Twenty to thirty hydraulic diameters are required before the local effect of the grid dissipates. Locally, both the single phase and two phase data show the same trends. Comparison of the single and two phase data also shown some differences. Some film boiling data indicate that an altered heat transfer regime may exist near the grid. High rod heat transfer coefficients at the grid locations indicate either a rewet of the rods or at least a change from film boiling to transition boiling near the spacer. The comparison also indicates that the film boiling data is affected on a global as well as local basis. This is due to the effect of the grid on the liquid distribution.

  11. Boiling and quenching heat transfer advancement by nanoscale surface modification.

    PubMed

    Hu, Hong; Xu, Cheng; Zhao, Yang; Ziegler, Kirk J; Chung, J N

    2017-07-21

    All power production, refrigeration, and advanced electronic systems depend on efficient heat transfer mechanisms for achieving high power density and best system efficiency. Breakthrough advancement in boiling and quenching phase-change heat transfer processes by nanoscale surface texturing can lead to higher energy transfer efficiencies, substantial energy savings, and global reduction in greenhouse gas emissions. This paper reports breakthrough advancements on both fronts of boiling and quenching. The critical heat flux (CHF) in boiling and the Leidenfrost point temperature (LPT) in quenching are the bottlenecks to the heat transfer advancements. As compared to a conventional aluminum surface, the current research reports a substantial enhancement of the CHF by 112% and an increase of the LPT by 40 K using an aluminum surface with anodized aluminum oxide (AAO) nanoporous texture finish. These heat transfer enhancements imply that the power density would increase by more than 100% and the quenching efficiency would be raised by 33%. A theory that links the nucleation potential of the surface to heat transfer rates has been developed and it successfully explains the current finding by revealing that the heat transfer modification and enhancement are mainly attributed to the superhydrophilic surface property and excessive nanoscale nucleation sites created by the nanoporous surface.

  12. Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

    NASA Technical Reports Server (NTRS)

    Cross, M. F.

    2011-01-01

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

  13. Radiation Heat Transfer Procedures for Space-Related Applications

    NASA Technical Reports Server (NTRS)

    Chai, John C.

    2000-01-01

    Over the last contract year, a numerical procedure for combined conduction-radiation heat transfer using unstructured grids has been developed. As a result of this research, one paper has been published in the Numerical Heat Transfer Journal. One paper has been accepted for presentation at the International Center for Heat and Mass Transfer's International Symposium on Computational Heat Transfer to be held in Australia next year. A journal paper is under review by my NASA's contact. A conference paper for the ASME National Heat Transfer conference is under preparation. In summary, a total of four (4) papers (two journal and two conference) have been published, accepted or are under preparation. There are two (2) to three (3) more papers to be written for the project. In addition to the above publications, one book chapter, one journal paper and six conference papers have been published as a result of this project. Over the last contract year, the research project resulted in one Ph.D. thesis and partially supported another Ph.D. student. My NASA contact and myself have formulated radiation heat transfer procedures for materials with different indices of refraction and for combined conduction-radiation heat transfer. We are trying to find other applications for the procedures developed under this grant.

  14. Radiative heat transfer in the extreme near field

    NASA Astrophysics Data System (ADS)

    Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M. T. Homer; García-Vidal, Francisco J.; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

    2015-12-01

    Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4, 5, 6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.

  15. Cryogenic apparatus for study of near-field heat transfer

    SciTech Connect

    Kralik, T.; Hanzelka, P.; Musilova, V.; Srnka, A.; Zobac, M.

    2011-05-15

    For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heat transfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heat transfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heat transfer over microscopic distances between metallic and non-metallic surfaces. Using a mechanical positioning system, a planeparallel gap between the samples, concentric disks, each 35 mm in diameter, is set and varied from 10{sup 0} to 10{sup 3} {mu}m. The heat transferred from the hot (10 - 100 K) to the cold sample ({approx}5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within {approx}2 nW/cm{sup 2} and {approx}30 {mu}W/cm{sup 2} is derived from the temperature drop along the thermal resistor. For tungsten samples, the distance of the near-field effect onset was inversely proportional to temperature and the heat power increase was observed up to three orders of magnitude greater than the power of far-field radiative heat transfer.

  16. Nanoscale heat transfer in the head-disk interface for heat assisted magnetic recording

    NASA Astrophysics Data System (ADS)

    Wu, Haoyu; Xiong, Shaomin; Canchi, Sripathi; Schreck, Erhard; Bogy, David

    2016-02-01

    Laser heating has been introduced in heat-assisted magnetic recording in order to reduce the magnetic coercivity and enable data writing. However, the heat flow inside a couple of nanometers head-disk gap is still not well understood. An experimental stage was built for studying heat transfer in the head-disk interface (HDI) and the heat-induced instability of the HDI. A laser heating system is included to produce a heated spot on the disk at the position of the slider. A floating air bearing slider is implemented in the stage for sensing the temperature change of the slider due to the heat transfer from the disk by the use of an embedded contact sensor, and the gap between the two surfaces is controlled by the use of a thermal fly-height control actuator. By using this system, we explore the dependency of the heat transfer on the gap spacing as well as the disk temperature.

  17. Wall-to-suspension heat transfer in circulating fluidized beds

    SciTech Connect

    Wirth, K.E.

    1995-12-31

    The wall-to-suspension heat transfer in circulating fluidized beds depends on the fluid mechanics immediately near the wall and on the thermal properties of the gas used. Experimental investigations of circulating fluidized beds of low dimensionless pressure gradients with different solid particles like bronze, glass and polystyrene at ambient temperatures showed no influence of the conductivity and the heat capacity of the solids on the heat transfer coefficient. Consequently the heat transfer coefficient in the form of the dimensionless Nusselt number can be described by the dimensionless numbers which characterize the gas-solid-flow near the wall. These numbers are the Archimedes number and the pressure drop-number. The last number relates the cross-sectional average solids concentration to the solids concentration at minimum fluidization condition. With the aid of a model of segregated vertical gas-solid flow, the flow pattern in the wall region can be calculated and thus the wall heat transfer which depends only on heat conduction in the gas and on the convective heat transfer by the gas. With elevated suspension temperatures, radiation contributes additionally to the heat transfer. When the solids concentration is low, the effect of the radiation on the heat transfer is high. Increasing solids concentration results in a decrease of the radiation effect due to the wall being shielded from the radiation of the hot particles in the core region by the cold solids clusters moving down the wall. A simple correlation is presented for calculating the wall-to-suspension heat transfer in circulating fluidized beds.

  18. 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.

  19. A review on boiling heat transfer enhancement with nanofluids

    PubMed Central

    2011-01-01

    There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement. PMID:21711794

  20. Determination of the heat transfer coefficients in porous media

    SciTech Connect

    Kim, L.V.

    1994-06-01

    The process of transpiration cooling is considered. Methods are suggested for estimating the volumetric coefficient of heat transfer with the use of a two-temperature model and the surface heat transfer coefficient at entry into a porous wall. The development of new technology under conditions of increasing heat loads puts the search for effective methods of heat transfer enhancement in the forefront of theoretical investigations. One of the promising trends in the solution of this problem is the use of porous materials (PM) in the elements of power units. For thermal protection against convective or radiative heat fluxes, the method of transpiration cooling is successfully used. The mechanism operative in the thermal protection involves the injection of a coolant through a porous medium to produce a screen over the contour of a body in a flow for removing heat energy from the skeleton of the porous material.