Cooperative heat transfer and ground coupled storage system
Metz, P.D.
A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.
International Nuclear Information System (INIS)
Zhang Tao; Liu Xiaohua; Zhang Lun; Jiang Yi
2012-01-01
Highlights: ► Investigates match properties of heat or mass transfer processes in HVAC system. ► Losses are caused by limited transfer ability, flow and parameter mismatching. ► Condition of flow matching is the same heat capacity of the fluids. ► Parameter matching is only reached along the saturation line in air–water system. ► Analytical solutions of heat and mass transfer resistance are derived. - Abstract: Sensible heat exchangers and coupled heat and mass transfer devices between humid air and water/desiccant are commonly used devices in air-conditioning systems. This paper focuses on the match properties of sensible heat transfer processes and coupled heat and mass transfer processes in an effort to understand the reasons for performance limitations in order to optimize system performance. Limited heat transfer capability and flow mismatching resulted in heat resistance of the sensible heat transfer process. Losses occurred during the heat and mass transfer processes due to limited transfer capability, flow mismatching, and parameter mismatching. Flow matching was achieved when the heat capacities of the fluids were identical, and parameter matching could only be reached along the saturation line in air–water systems or the iso-concentration line in air–desiccant systems. Analytical solutions of heat transfer resistance and mass transfer resistance were then derived. The heat and mass transfer process close to the saturation line is recommended, and heating sprayed water resulted in better humidification performance than heating inlet air in the air humidifier.
Modelling of complex heat transfer systems by the coupling method
Energy Technology Data Exchange (ETDEWEB)
Bacot, P.; Bonfils, R.; Neveu, A.; Ribuot, J. (Centre d' Energetique de l' Ecole des Mines de Paris, 75 (France))
1985-04-01
The coupling method proposed here is designed to reduce the size of matrices which appear in the modelling of heat transfer systems. It consists in isolating the elements that can be modelled separately, and among the input variables of a component, identifying those which will couple it to another component. By grouping these types of variable, one can thus identify a so-called coupling matrix of reduced size, and relate it to the overall system. This matrix allows the calculation of the coupling temperatures as a function of external stresses, and of the state of the overall system at the previous instant. The internal temperatures of the components are determined from for previous ones. Two examples of applications are presented, one concerning a dwelling unit, and the second a solar water heater.
Study of coupled heat and mass transfer during absorption of ...
Indian Academy of Sciences (India)
(iii) The gas phase is ideal from thermodynamic point of view. (iv) Only mass transfer and no heat transfer takes place through the porous filter. (v) The thermal conductivity and specific heat of the hydride bed are assumed to be constant. This assumption underestimates the bed performance slightly, because in actual case ...
Study of coupled heat and mass transfer during absorption of ...
Indian Academy of Sciences (India)
2.3 Hydrogen mass balance ε. ∂ρg. ∂t. + div(ρgVg) ... staggered grids to catch the heat transfer across the control volume by convection effectively. .... temperature decreases due to fall in the reaction rate and increase in heat transfer from the.
Indian Academy of Sciences (India)
First page Back Continue Last page Overview Graphics. Heat transfer. Heat conduction in solid slab. Convective heat transfer. Non-linear temperature. variation due to flow. HEAT FLUX AT SURFACE. conduction/diffusion.
Finite element procedures for coupled linear analysis of heat transfer, fluid and solid mechanics
Sutjahjo, Edhi; Chamis, Christos C.
1993-01-01
Coupled finite element formulations for fluid mechanics, heat transfer, and solid mechanics are derived from the conservation laws for energy, mass, and momentum. To model the physics of interactions among the participating disciplines, the linearized equations are coupled by combining domain and boundary coupling procedures. Iterative numerical solution strategy is presented to solve the equations, with the partitioning of temporal discretization implemented.
International Nuclear Information System (INIS)
2003-08-01
This book deals with analysis of heat transfer which includes nonlinear analysis examples, radiation heat transfer, analysis of heat transfer in ANSYS, verification of analysis result, analysis of heat transfer of transition with automatic time stepping and open control, analysis of heat transfer using arrangement of ANSYS, resistance of thermal contact, coupled field analysis such as of thermal-structural interaction, cases of coupled field analysis, and phase change.
Heat transfer and thermal stress analysis in fluid-structure coupled field
International Nuclear Information System (INIS)
Li, Ming-Jian; Pan, Jun-Hua; Ni, Ming-Jiu; Zhang, Nian-Mei
2015-01-01
In this work, three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out. The structure considered is from the dual-coolant lithium-lead (DCLL) blanket, which is the key technology of International Thermo-nuclear Experimental Reactor (ITER). The model was developed based on finite element-finite volume method and was employed to investigate mechanical behaviours of Flow Channel Insert (FCI) and heat transfer in the blanket under nuclear reaction. Temperature distribution, thermal deformation and thermal stresses were calculated in this work, and the effects of thermal conductivity, convection heat transfer coefficient and flow velocity were analyzed. Results show that temperature gradients and thermal stresses of FCI decrease when FCI has better heat conductivity. Higher convection heat transfer coefficient will result in lower temperature, thermal deformations and stresses in FCI. Analysis in this work could be a theoretical basis of blanket optimization. - Highlights: • We use FVM and FEM to investigate FCI structural safety considering heat transfer and FSI effects. • Higher convective heat transfer coefficient is beneficial for the FCI structural safety without much affect to bulk flow temperature. • Smaller FCI thermal conductivity can better prevent heat leakage into helium, yet will increase FCI temperature gradient and thermal stress. • Three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out
Coupled heat transfer in high temperature transporting system with semitransparent/opaque material
International Nuclear Information System (INIS)
Du Shenghua; Xia Xinjin
2010-01-01
The heat transfer model of the aerodynamic heating coupled with radiative cooling was developed. The thermal protect system includes the higher heat flux region with high temperature semitransparent material, the heat transporting channel and the lower heat flux region with metal. The control volume method was combined with the Monte Carlo method to calculate the coupled heat transfer of the transporting system, and the thermal equilibrium equation for the transporting channel was solved simultaneously. The effect of the aeroheating flux radio, the area ratio of radiative surfaces, the convective heat transfer coefficient of the heat transporting channel on the radiative surface temperature and the fluid temperature in the heat transporting channel were analyzed. The effect of radiation and conduction in the semitransparent material was discussed. The result shows that to increase the convective heat transfer coefficient in heat flux channel can enhance the heat transporting ability of the system, but the main parameter to effect on the temperature of the heat transporting system is the area ratio of radiative surfaces. (authors)
3D modelling of coupled mass and heat transfer of a convection-oven roasting process
DEFF Research Database (Denmark)
Feyissa, Aberham Hailu; Adler-Nissen, Jens; Gernaey, Krist
2013-01-01
A 3D mathematical model of coupled heat and mass transfer describing oven roasting of meat has been developed from first principles. The proposed mechanism for the mass transfer of water is modified and based on a critical literature review of the effect of heat on meat. The model equations...... are based on a conservation of mass and energy, coupled through Darcy's equations of porous media - the water flow is mainly pressure-driven. The developed model together with theoretical and experimental assessments were used to explain the heat and water transport and the effect of the change...
International Nuclear Information System (INIS)
Saad, M.A.
1985-01-01
Heat transfer takes place between material systems as a result of a temperature difference. The transmission process involves energy conversions governed by the first and second laws of thermodynamics. The heat transfer proceeds from a high-temperature region to a low-temperature region, and because of the finite thermal potential, there is an increase in entropy. Thermodynamics, however, is concerned with equilibrium states, which includes thermal equilibrium, irrespective of the time necessary to attain these equilibrium states. But heat transfer is a result of thermal nonequilibrium conditions, therefore, the laws of thermodynamics alone cannot describe completely the heat transfer process. In practice, most engineering problems are concerned with the rate of heat transfer rather than the quantity of heat being transferred. Resort then is directed to the particular laws governing the transfer of heat. There are three distinct modes of heat transfer: conduction, convection, and radiation. Although these modes are discussed separately, all three types may occur simultaneously
Wildemeersch, S; Jamin, P; Orban, P; Hermans, T; Klepikova, M; Nguyen, F; Brouyère, S; Dassargues, A
2014-11-15
Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54MJ/m(3)/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for
Impact of coupled heat and moisture transfer effects on buildings energy consuption
Directory of Open Access Journals (Sweden)
Ferroukhi Mohammed Yacine
2017-01-01
Full Text Available Coupled heat, air, and moisture transfers through building envelope have an important effect on prediction of building energy requirements. Several works were conducted in order to integrate hygrothermal transfers in dynamic buildings simulations codes. However, the incorporation of multidirectional hygrothermal transfer analysis in the envelope into building simulation tools is rarely considered. In this work, coupled heat, air, and moisture (HAM transfer model in multilayer walls was established. Thereafter, the HAM model is coupled dynamically to a building behavior code (BES.The coupling concerns a co-simulation between COMSOL Multiphysics and TRNSYS software. Afterward, the HAM-BES co-simulation accuracy was verified. Then, HAM-BES co-simulation platform was applied to a case study with various types of climates (temperate, hot and humid, cold and humid. Three simulations cases were carried out. The first simulation case consists of the TRNSYS model without HAM transfer model. The second simulation case, 1-D HAM model for the envelope was integrated in TRNSYS code. For the third one, 1-D HAM model for the wall and 2-D HAM model for thermal bridges were coupled to the thermal building model of TRNSYS. Analysis of the results confirms the significant impact of 2-D envelope hygrothermal transfers on the indoor thermal and moisture behavior of building as well as on the energy building assessment. These conclusions are shown for different studied climates.
DEFF Research Database (Denmark)
Jabbari, Masoud; Hosseinzadeh, Azin
2013-01-01
In the present study the numerical model in 2D is used to study the solidification bahavior of the gray cast iron. The conventional heat transfer is coupled with the proposed micro-model to predict the amount of different phases, i.e. total austenite (c) phase, graphite (G) and cementite (C...
Exact solutions for MHD flow of couple stress fluid with heat transfer
Directory of Open Access Journals (Sweden)
Najeeb Alam Khan
2016-01-01
Full Text Available This paper aims at presenting exact solutions for MHD flow of couple stress fluid with heat transfer. The governing partial differential equations (PDEs for an incompressible MHD flow of couple stress fluid are reduced to ordinary differential equations by employing wave parameter. The methodology is implemented for linearizing the flow equations without extra transformation and restrictive assumptions. Comparison is made with the result obtained previously.
Analysis of heat and mass transfers in two-phase flow by coupling optical diagnostic techniques
International Nuclear Information System (INIS)
Lemaitre, P.; Porcheron, E.
2008-01-01
During the course of a hypothetical accident in a nuclear power plant, spraying might be actuated to reduce static pressure in the containment. To acquire a better understanding of the heat and mass transfers between a spray and the surrounding confined gas, non-intrusive optical measurements have to be carried out simultaneously on both phases. The coupling of global rainbow refractometry with out-of-focus imaging and spontaneous Raman scattering spectroscopy allows us to calculate the local Spalding parameter B M , which is useful in describing heat transfer associated with two-phase flow. (orig.)
Analysis of heat and mass transfers in two-phase flow by coupling optical diagnostic techniques
Energy Technology Data Exchange (ETDEWEB)
Lemaitre, P.; Porcheron, E. [Institut de Radioprotection et de Surete Nucleaire, Saclay (France)
2008-08-15
During the course of a hypothetical accident in a nuclear power plant, spraying might be actuated to reduce static pressure in the containment. To acquire a better understanding of the heat and mass transfers between a spray and the surrounding confined gas, non-intrusive optical measurements have to be carried out simultaneously on both phases. The coupling of global rainbow refractometry with out-of-focus imaging and spontaneous Raman scattering spectroscopy allows us to calculate the local Spalding parameter B{sub M}, which is useful in describing heat transfer associated with two-phase flow. (orig.)
Wang, Da-Lin; Qi, Hong
Semi-transparent materials (such as IR optical windows) are widely used for heat protection or transfer, temperature and image measurement, and safety in energy , space, military, and information technology applications. They are used, for instance, ceramic coatings for thermal barriers of spacecrafts or gas turbine blades, and thermal image observation under extreme or some dangerous environments. In this paper, the coupled conduction and radiation heat transfer model is established to describe temperature distribution of semitransparent thermal barrier medium within the aerothermal environment. In order to investigate this numerical model, one semi-transparent sample with black coating was considered, and photothermal properties were measured. At last, Finite Volume Method (FVM) was used to solve the coupled model, and the temperature responses from the sample surfaces were obtained. In addition, experiment study was also taken into account. In the present experiment, aerodynamic heat flux was simulated by one electrical heater, and two experiment cases were designed in terms of the duration of aerodynamic heating. One case is that the heater irradiates one surface of the sample continually until the other surface temperature up to constant, and the other case is that the heater works only 130 s. The surface temperature responses of these two cases were recorded. Finally, FVM model of the coupling conduction-radiation heat transfer was validated based on the experiment study with relative error less than 5%.
Thermoplasticity of coupled bodies in the case of stress-dependent heat transfer
Kilikovskaya, O. A.
1987-01-01
The problem of the thermal stresses in coupled deformable bodies is formulated for the case where the heat-transfer coefficient at the common boundary depends on the stress-strain state of the bodies (e.g., is a function of the normal pressure at the common boundary). Several one-dimensional problems are solved in this formulation. Among these problems is the determination of the thermal stresses in an n-layer plate and in a two-layer cylinder.
Mountain scale modeling of transient, coupled gas flow, heat transfer and carbon-14 migration
International Nuclear Information System (INIS)
Lu, Ning; Ross, B.
1993-01-01
We simulate mountain-scale coupled heat transfer and gas flow at Yucca Mountain. A coupled rock-gas flow and heat transfer model, TGIF2, is used to simulate mountain-scale two-dimensional transient heat transfer and gas flow. The model is first verified against an analytical solution for the problem of an infinite horizontal layer of fluid heated from below. Our numerical results match very well with the analytical solution. Then, we obtain transient temperature and gas flow distributions inside the mountain. These distributions are used by a transient semianalytical particle tracker to obtain carbon-14 travel times for particles starting at different locations within the repository. Assuming that the repository is filled with 30-year-old waste at an initial areal power density of 57 kw/acre, we find that repository temperatures remain above 60 degrees C for more than 10,000 years. Carbon-14 travel times to the surface are mostly less than 1000 years, for particles starting at any time within the first 10,000 years
International Nuclear Information System (INIS)
Dauvois, Yann
2016-01-01
In the present work, the effective heat transfer properties of fibrous medium are determined by taking into account a coupling of heat conduction and radiation. A virtual, statistically homogeneous, two-phase fibrous sample has been built by stacking finite absorbing cylinders in vacuum. These cylinders are dispersed according to prescribed distribution functions defining the cylinder positions and orientations. Cylinder overlappings are allowed. Extinction, absorption and scattering are characterised by radiative statistical functions which allow the Beerian behaviour of a medium to be assessed (or not). They are accurately determined with a Monte Carlo method. Whereas the gaseous phase exhibits a Beerian behaviour, the fibre phase is strongly non Beerian. The radiative power field deposited within the fibrous material is calculated by resolving a model which couples a Generalized Radiative Transfer Equation (GRTE) and a classic Radiative Transfer Equation (RTE). The model of conduction transfer is based on a random walk method without meshing. The simulation of Brownian motion of walkers in fibres allows the energy equation to be solved. The idea of the method is to characterize the temperature in an elementary volume by the density of walkers, which roam the medium. The problem is governed by boundary conditions; A constant concentration of walkers (or a constant flux) is associated with a fixed temperature (or flux). (author) [fr
Overview of ground coupled heat pump research and technology transfer activities
Baxter, V. D.; Mei, V. C.
Highlights of DOE-sponsored ground coupled heat pump (GCHP) research at Oak Ridge National Laboratory (ORNL) are presented. ORNL, in cooperation with Niagara Mohawk Power Company, Climate Master, Inc., and Brookhaven National Laboratory developed and demonstrated an advanced GCHP design concept with shorter ground coils that can reduce installed costs for northern climates. In these areas it can also enhance the competitiveness of GCHP systems versus air-source heat pumps by lowering their payback from 6 to 7 years to 3 to 5 years. Ground coil heat exchanger models (based primarily on first principles) have been developed and used by others to generate less conservative ground coil sizing methods. An aggressive technology transfer initiative was undertaken to publicize results of this research and make it available to the industry. Included in this effort were an international workshop, trade press releases and articles, and participation in a live teleconference on GCHP technology.
Directory of Open Access Journals (Sweden)
Kohei Mizuno
2015-10-01
Full Text Available Since 2007, resonant coupling wireless power transfer (WPT technology has been attracting attention and has been widely researched for practical use. Moreover, dosimetric evaluation has also been discussed to evaluate the potential health risks of the electromagnetic field from this WPT technology based on the International Commission on Non-Ionizing Radiation Protection (ICNIRP guidelines. However, there has not been much experimental evaluation of the potential health risks of this WPT technology. In this study, to evaluate whether magnetic resonant coupling WPT induces cellular stress, we focused on heat shock proteins (Hsps and determined the expression level of Hsps 27, 70 and 90 in WI38VA13 subcloned 2RA human fibroblast cells using a western blotting method. The expression level of Hsps under conditions of magnetic resonant coupling WPT for 24 h was not significantly different compared with control cells, although the expression level of Hsps for cells exposed to heat stress conditions was significantly increased. These results suggested that exposure to magnetic resonant coupling WPT did not cause detectable cell stress.
Multiregional coupled conduction--convection model for heat transfer in an HTGR core
International Nuclear Information System (INIS)
Giles, G.E. Jr.; Childs, K.W.; Sanders, J.P.
1978-01-01
HEXEREI is a three-dimensional, coupled conduction-convection heat transfer and multichannel fluid dynamic analysis computer code with both steady-state and transient capabilities. The program was developed to provide thermal-fluid dynamic analysis of a core following the general design for high-temperature gas-cooled reactors (HTGRs); its purpose was to provide licensing evaluations for the U.S. Nuclear Regulatory Commission. In order to efficiently model the HTGR core, the nodal geometry of HEXEREI was chosen as a regular hexagonal array perpendicular to the axis of and bounded by a right circular cylinder. The cylindrical nodal geometry surrounds the hexagonal center portion of the mesh; these two different types of nodal geometries must be connected by interface nodes to complete the accurate modeling of the HTGR core. HEXEREI will automatically generate a nodal geometry that will accurately model a complex assembly of hexagonal and irregular prisms. The accuracy of the model was proven by a comparison of computed values with analytical results for steady-state and transient heat transfer problems. HEXEREI incorporates convective heat transfer to the coolant in many parallel axial flow channels. Forced and natural convection (which permits different flow directions in parallel channels) is included in the heat transfer and fluid dynamic models. HEXEREI incorporates a variety of steady-state and transient solution techniques that can be matched with a particular problem to minimize the computational time. HEXEREI was compared with a code of similar capabilities that was based on a Cartesian mesh. This code modeled only one specific core design, and the mesh spacing was closer than that generated by HEXEREI. Good agreement was obtained with the detail provided by the representations
International Nuclear Information System (INIS)
Conklin, J.C.
1986-08-01
The differential equations representing the coupled heat transfer from the solid nuclear core components to the helium in the coolant channels are scaled in terms of representative quantities. This scaling process identifies the relative importance of the various terms of the coupled differential equations. The relative importance of these terms is then used to simplify the numerical solution of the coupled heat transfer for two bounding cases of full-power operation and depressurization from full-system operating pressure for the Fort St. Vrain High-Temperature Gas-Cooled Reactor. This analysis rigorously justifies the simplified system of equations used in the nuclear safety analysis effort at Oak Ridge National Laboratory
Kinetic Monte Carlo modeling of chemical reactions coupled with heat transfer.
Castonguay, Thomas C; Wang, Feng
2008-03-28
In this paper, we describe two types of effective events for describing heat transfer in a kinetic Monte Carlo (KMC) simulation that may involve stochastic chemical reactions. Simulations employing these events are referred to as KMC-TBT and KMC-PHE. In KMC-TBT, heat transfer is modeled as the stochastic transfer of "thermal bits" between adjacent grid points. In KMC-PHE, heat transfer is modeled by integrating the Poisson heat equation for a short time. Either approach is capable of capturing the time dependent system behavior exactly. Both KMC-PHE and KMC-TBT are validated by simulating pure heat transfer in a rod and a square and modeling a heated desorption problem where exact numerical results are available. KMC-PHE is much faster than KMC-TBT and is used to study the endothermic desorption of a lattice gas. Interesting findings from this study are reported.
Cumulant generating function formula of heat transfer in ballistic systems with lead-lead coupling
Li, Huanan; Agarwalla, Bijay Kumar; Wang, Jian-Sheng
2012-10-01
Based on a two-time observation protocol, we consider heat transfer in a given time interval tM in a lead-junction-lead system taking coupling between the leads into account. In view of the two-time observation, consistency conditions are carefully verified in our specific family of quantum histories. Furthermore, its implication is briefly explored. Then using the nonequilibrium Green's function method, we obtain an exact formula for the cumulant generating function for heat transfer between the two leads, valid in both transient and steady-state regimes. Also, a compact formula for the cumulant generating function in the long-time limit is derived, for which the Gallavotti-Cohen fluctuation symmetry is explicitly verified. In addition, we briefly discuss Di Ventra's repartitioning trick regarding whether the repartitioning procedure of the total Hamiltonian affects the nonequilibrium steady-state current fluctuation. All kinds of properties of nonequilibrium current fluctuations, such as the fluctuation theorem in different time regimes, could be readily given according to these exact formulas.
A solution of coupled heat-moisture transfer in saturated-unsaturated media
International Nuclear Information System (INIS)
Geraminegad, M.; Saxena, S.K.
1985-01-01
Two formulations of coupled heat and mass flow in the porous media are presented and solved numerically using finite element method. This paper concludes that the formulation based on Phillip and de Vries better estimates heat flow, and, the non-linear behavior of soil parameters significantly affects heat and mass flow in the porous media
On Entropy Generation and the Effect of Heat and Mass Transfer Coupling in a Distillation Process
Burgos-Madrigal, Paulina; Mendoza, Diego F.; López de Haro, Mariano
2018-01-01
The entropy production rates as obtained from the exergy analysis, entropy balance and the nonequilibrium thermodynamics approach are compared for two distillation columns. The first case is a depropanizer column involving a mixture of ethane, propane, n-butane and n-pentane. The other is a weighed sample of Mexican crude oil distilled with a pilot scale fractionating column. The composition, temperature and flow profiles, for a given duty and operating conditions in each column, are obtained with the Aspen Plus V8.4 software by using the RateFrac model with a rate-based nonequilibrium column. For the depropanizer column the highest entropy production rate is found in the central trays where most of the mass transfer occurs, while in the second column the highest values correspond to the first three stages (where the vapor mixture is in contact with the cold liquid reflux), and to the last three stages (where the highest temperatures take place). The importance of the explicit inclusion of thermal diffusion in these processes is evaluated. In the depropanizer column, the effect of the coupling between heat and mass transfer is found to be negligible, while for the fractionating column it becomes appreciable.
Second law analysis of coupled conduction-radiation heat transfer with phase change
International Nuclear Information System (INIS)
Makhanlall, D.; Liu, L.H.
2010-01-01
This work considers an exergy-based analysis of two-dimensional solid-liquid phase change processes in a square cavity enclosure. The phase change material (PCM) concerns a semi-transparent absorbing, emitting and anisotropically scattering medium with constant thermodynamic properties. The enthalpy-based energy equation is solved numerically using computational fluid dynamics. Once the energy equation is solved, local exergy loss due to heat conduction and radiative heat transfer during the phase change process is calculated by post processing procedures. In this work, the radiation exergy loss in the medium and at the enclosure boundary is taken into consideration. It is found that radiation exergy loss is significant in the high-temperature phase change process. Parametric investigation is also carried out to study the effects of Stefan number, Biot number, Planck number, single scattering albedo and wall emissivity on exergy loss. The results show that the total exergy loss increases with Biot number, single scattering albedo and wall emissivity. The second law effects of the conduction-radiation coupling in the energy equation are also shown in this work. (authors)
Heat transfer: Pittsburgh 1987
International Nuclear Information System (INIS)
Lyczkowski, R.W.
1987-01-01
This book contains papers divided among the following sections: Process Heat Transfer; Thermal Hydraulics and Phase Change Phenomena; Analysis of Multicomponent Multiphase Flow and Heat Transfer; Heat Transfer in Advanced Reactors; General Heat Transfer in Solar Energy; Numerical Simulation of Multiphase Flow and Heat Transfer; High Temperature Heat Transfer; Heat Transfer Aspects of Severe Reactor Accidents; Hazardous Waste On-Site Disposal; and General Papers
Out-of-plane heat transfer in van der Waals stacks through electron-hyperbolic phonon coupling
Tielrooij, Klaas-Jan; Hesp, Niels C. H.; Principi, Alessandro; Lundeberg, Mark B.; Pogna, Eva A. A.; Banszerus, Luca; Mics, Zoltán; Massicotte, Mathieu; Schmidt, Peter; Davydovskaya, Diana; Purdie, David G.; Goykhman, Ilya; Soavi, Giancarlo; Lombardo, Antonio; Watanabe, Kenji; Taniguchi, Takashi; Bonn, Mischa; Turchinovich, Dmitry; Stampfer, Christoph; Ferrari, Andrea C.; Cerullo, Giulio; Polini, Marco; Koppens, Frank H. L.
2018-01-01
Van der Waals heterostructures have emerged as promising building blocks that offer access to new physics, novel device functionalities and superior electrical and optoelectronic properties1-7. Applications such as thermal management, photodetection, light emission, data communication, high-speed electronics and light harvesting8-16 require a thorough understanding of (nanoscale) heat flow. Here, using time-resolved photocurrent measurements, we identify an efficient out-of-plane energy transfer channel, where charge carriers in graphene couple to hyperbolic phonon polaritons17-19 in the encapsulating layered material. This hyperbolic cooling is particularly efficient, giving picosecond cooling times for hexagonal BN, where the high-momentum hyperbolic phonon polaritons enable efficient near-field energy transfer. We study this heat transfer mechanism using distinct control knobs to vary carrier density and lattice temperature, and find excellent agreement with theory without any adjustable parameters. These insights may lead to the ability to control heat flow in van der Waals heterostructures.
Barron, Randall F
2016-01-01
Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.
Energy Technology Data Exchange (ETDEWEB)
Chen, Fei, E-mail: chenfei@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); North China University of Water Resources and Electric Power, 36 Beihuan Road, Zhengzhou, Henan 450011 (China); Cai, Jun, E-mail: caijun@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Li, Xunfeng, E-mail: lixunfeng@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Huai, Xiulan, E-mail: hxl@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China); Wang, Yongwei, E-mail: wangyongwei@iet.cn [Institute of Engineering Thermophysics, Chinese Academy of Sciences, 11 Beisihuanxi Road, Beijing 100190 (China)
2014-07-01
Highlights: • Heat transfer in heat exchanger can be improved by increasing helium's flow rate. • The outlet temperature of helium decreases with increasing helium's flow rate. • Balance is necessary between good heat transfer and high helium outlet temperature. - Abstract: LBE-helium experimental loop of ADS (LELA) and LBE-helium heat exchanger have been designed and constructed with the supporting of the “ADS Transmutation System” project of Chinese Academy of Sciences. In order to investigate the flow and heat transfer characteristics between LBE and helium, 3D numerical simulation of fluid–solid coupled heat transfer with variable property in the LBE-helium heat exchanger is conducted in the present study. The effects of mass-flow-rates of helium and LBE in the shell-side and tube-side on the heat transfer performance are addressed. It is found that the heat transfer performance can be significantly improved by increasing helium mass-flow-rate in the shell-side. In order to easily and quickly obtain the outlet temperatures of helium and LBE, a concept of modified effectiveness is introduced and correlated as the function of tube-side to shell-side heat capacity rate ratio. The results show that the outlet temperature of helium decreases with increasing helium mass-flow-rate. Therefore, considering the utilization of high-temperature helium in the future, for example power generation, there should be a tradeoff between good heat transfer performance and high outlet helium temperature when confirming helium mass-flow-rate.
International Nuclear Information System (INIS)
Wang, Lang Chen.
1990-01-01
A semi-implicit coupling technique (treating only the fluid temperature in the energy source term implicitly) of fluid heat-transfer to conduction slabs is presently used in TRAC-PF1. In this study, a fully implicit coupling scheme between the flow field and conduction slab for the one-dimensional capability of TRAC-PF1 has been developed. The new methods treat the heat-transfer coefficient and wall temperature in the energy source term of both the convection and the conduction equation implicitly. In order to test the accuracy of the standard TRAC coupling method and the new methods used in TRAC-PF1, a series of simple tube experiments were modeled with TRAC-PF1 version 3.9B. Additional studies showed the current TRAC-PF1 convergence variables (pressure fraction change and temperature change) and the current convergence criteria are not appropriate for obtaining an accurate result. Use of these values would produce non-physical double values or would adversely affect results in the reflood calculation. Another study also had been done to determine the importance of each HTC variable on computational accuracy and speed by using the non-linear oterative method. It is found that the heat-transfer correlations have a strong dependency on the local void fraction rather than on fluid velocity, fluid temperature, and wall surface temperature in the film boiling heat-transfer regime. At the beginning of a cooldown transient, the old time void fraction is always higher than the new time void fraction in the same time step. The old time void fraction evaluates a lower heat-transfer coefficient for that cell and initiates cooldown later and more slowly. This then leads to a longer quench time and lowers the fluid temperature and the wall temperature plateau for the downstream control volumes
A coupled model on fluid flow, heat transfer and solidification in continuous casting mold
Directory of Open Access Journals (Sweden)
Xu-bin Zhang
2017-11-01
Full Text Available Fluid flow, heat transfer and solidification of steel in the mold are so complex but crucial, determining the surface quality of the continuous casting slab. In the current study, a 2D numerical model was established by Fluent software to simulate the fluid flow, heat transfer and solidification of the steel in the mold. The VOF model and k-ε model were applied to simulate the flow field of the three phases (steel, slag and air, and solidification model was used to simulate the solidification process. The phenomena at the meniscus were also explored through interfacial tension between the liquid steel and slag as well as the mold oscillation. The model included a 20 mm thick mold to clarify the heat transfer and the temperature distribution of the mold. The simulation results show that the liquid steel flows as upper backflow and lower backflow in the mold, and that a small circulation forms at the meniscus. The liquid slag flows away from the corner at the meniscus or infiltrates into the gap between the mold and the shell with the mold oscillating at the negative strip stage or at the positive strip stage. The simulated pitch and the depth of oscillation marks approximate to the theoretical pitch and measured depth on the slab.
SUNDÉN, B
2012-01-01
Presenting the basic mechanisms for transfer of heat, Introduction to Heat Transfer gives a deeper and more comprehensive view than existing titles on the subject. Derivation and presentation of analytical and empirical methods are provided for calculation of heat transfer rates and temperature fields as well as pressure drop. The book covers thermal conduction, forced and natural laminar and turbulent convective heat transfer, thermal radiation including participating media, condensation, evaporation and heat exchangers.
International Nuclear Information System (INIS)
Selvakumar, P.; Somasundaram, P.; Thangavel, P.
2014-01-01
Highlights: • Instant hot water at temperatures between 40 °C and 68 °C in the low solar radiation range of 240–540 W/m 2 . • Usage of therminol D-12 and parabolic trough in low temperature application. • Stability of thermal and flow properties of therminol D-12 are studied. - Abstract: Fossil fuels and electrical energy are widely used for instant hot water generation in rural and urban areas. Also, conventional solar water heaters do not support instant hot water generation because of various problems. A new system with evacuated tube collector using synthetic oil as heat transfer fluid coupled with parabolic trough is developed and studied experimentally for instant hot water generation in the presence of low solar irradiance. Among the different grades of therminol, therminol D-12 is chosen for the study because of its thermal stability. Parabolic trough is coupled to evacuated tube to enhance the flow as well as heating characteristics of therminol. Heating efficiency and temperature characteristics are determined for the newly developed system under low solar irradiance conditions. Instant hot water can be produced by the new system at a temperature of 60 °C in the presence of low solar radiation. This newly developed system has the ability to check the fossil fuel consumption and electrical energy consumption for instant hot water generation in household applications. The stability of the heat transfer fluid is also ensured by repeated experiments
International Nuclear Information System (INIS)
Amaya, J.; Cabrit, O.; Poitou, D.; Cuenot, B.; El Hafi, M.
2010-01-01
Direct numerical simulations (DNS) of an anisothermal reacting turbulent channel flow with and without radiative source terms have been performed to study the influence of the radiative heat transfer on the optically non-homogeneous boundary layer structure. A methodology for the study of the emitting/absorbing turbulent boundary layer (TBL) is presented. Details on the coupling strategy and the parallelization techniques are exposed. An analysis of the first order statistics is then carried out. It is shown that, in the studied configuration, the global structure of the thermal boundary layer is not significantly modified by radiation. However, the radiative transfer mechanism is not negligible and contributes to the heat losses at the walls. The classical law-of-the-wall for temperature can thus be improved for RANS/LES simulations taking into account the radiative contribution.
Kovtanyuk, Andrey E.; Botkin, Nikolai D.; Hoffmann, Karl-Heinz
2012-01-01
Radiative-conductive heat transfer in a medium bounded by two reflecting and radiating plane surfaces is considered. This process is described by a nonlinear system of two differential equations: an equation of the radiative heat transfer
Kakac, Sadik; Pramuanjaroenkij, Anchasa
2014-01-01
Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....
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.
Finite element simulation of heat transfer
Bergheau, Jean-Michel
2010-01-01
This book introduces the finite element method applied to the resolution of industrial heat transfer problems. Starting from steady conduction, the method is gradually extended to transient regimes, to traditional non-linearities, and to convective phenomena. Coupled problems involving heat transfer are then presented. Three types of couplings are discussed: coupling through boundary conditions (such as radiative heat transfer in cavities), addition of state variables (such as metallurgical phase change), and coupling through partial differential equations (such as electrical phenomena).? A re
International Nuclear Information System (INIS)
Hasatani, Masanobu; Itaya, Yoshinori
1985-01-01
In order to develop energy-saving techniques and new energy techniques, and also most advanced techniques by making industrial equipment with high performance, heat transfer performance frequently becomes an important problem. In addition, the improvement of conventional heat transfer techniques and the device of new heat transfer techniques are often required. It is most proper that chemical engineers engage in the research and development for enhancing heat transfer. The research and development for enhancing heat transfer are important to heighten heat exchange efficiency or to cool equipment for preventing overheat in high temperature heat transfer system. In this paper, the techniques of enhancing radiative heat transfer and the improvement of radiative heat transfer characteristics are reported. Radiative heat transfer is proportional to fourth power of absolute temperature, and it does not require any heat transfer medium, but efficient heat-radiation converters are necessary. As the techniques of enhancing radiative heat transfer, the increase of emission and absorption areas, the installation of emissive structures and the improvement of radiative characteristics are discussed. (Kako, I.)
Li, Huanan
2013-03-01
Based on a two-time observation protocol, we consider heat transfer in a given time interval tM in a lead-junction-lead system taking coupling between the leads into account. In view of the two-time observation, consistency conditions are carefully verified in our specific family of quantum histories. Furthermore, its implication is briefly explored. Then using the nonequilibrium Green's function method, we obtain an exact formula for the cumulant generating function for heat transfer between the two leads, valid in both transient and steady-state regimes. Also, a compact formula for the cumulant generating function in the long-time limit is derived, for which the Gallavotti-Cohen fluctuation symmetry is explicitly verified. In addition, we briefly discuss Di Ventra's repartitioning trick regarding whether the repartitioning procedure of the total Hamiltonian affects the nonequilibrium steady-state current fluctuation. All kinds of properties of nonequilibrium current fluctuations, such as the fluctuation theorem in different time regimes, could be readily given according to these exact formulas. Finally a practical formalism dealing with cumulants of heat transfer across general nonlinear quantum systems is established based on field theoretical/algebraic method.
Tian, C.; Weng, J.; Liu, Y.
2017-11-01
The convection heat transfer coefficient is one of the evaluation indexes of the brake disc performance. The method used in this paper to calculate the convection heat transfer coefficient is a fluid-solid coupling simulation method, because the calculation results through the empirical formula method have great differences. The model, including a brake disc, a car body, a bogie and flow field, was built, meshed and simulated in the software FLUENT. The calculation models were K-epsilon Standard model and Energy model. The working condition of the brake disc was considered. The coefficient of various parts can be obtained through the method in this paper. The simulation result shows that, under 160 km/h speed, the radiating ribs have the maximum convection heat transfer coefficient and the value is 129.6W/(m2·K), the average coefficient of the whole disc is 100.4W/(m2·K), the windward of ribs is positive-pressure area and the leeward of ribs is negative-pressure area, the maximum pressure is 2663.53Pa.
Energy Technology Data Exchange (ETDEWEB)
Golbahar Haghighi, M.R.; Eghtesad, M. [Department of Mechanical Engineering, School of Engineering, Shiraz University, Shiraz 71348-51154 (Iran, Islamic Republic of); Malekzadeh, P. [Department of Mechanical Engineering, School of Engineering, Persian Gulf University, Boushehr 75169-13798 (Iran, Islamic Republic of)], E-mail: malekzadeh@pgu.ac.ir
2008-05-15
In this paper, a mixed finite element (FE) and differential quadrature (DQ) method as a simple, accurate and computationally efficient numerical tool for two dimensional transient heat transfer analysis of functionally graded materials (FGMs) is developed. The method benefits from the high accuracy, fast convergence behavior and low computational efforts of the DQ in conjunction with the advantages of the FE method in general geometry, loading and systematic boundary treatment. Also, the boundary conditions at the top and bottom surfaces of the domain can be implemented more precisely and in strong form. The temporal derivatives are discretized using an incremental DQ method (IDQM), whose numerical stability is not sensitive to time step size. The effects of non-uniform convective-radiative conditions on the boundaries are investigated. The accuracy of the proposed method is demonstrated by comparing its results with those available in the literature. It is shown that using few grid points, highly accurate results can be obtained.
MODELING COUPLED PROCESSES OF MULTIPHASE FLOW AND HEAT TRANSFER IN UNSATURATED FRACTURED ROCK
International Nuclear Information System (INIS)
Y. Wu; S. Mukhopadhyay; K. Zhang; G.S. Bodvarsson
2006-01-01
A mountain-scale, thermal-hydrologic (TH) numerical model is developed for investigating unsaturated flow behavior in response to decay heat from the radioactive waste repository at Yucca Mountain, Nevada, USA. The TH model, consisting of three-dimensional (3-D) representations of the unsaturated zone, is based on the current repository design, drift layout, and thermal loading scenario under estimated current and future climate conditions. More specifically, the TH model implements the current geological framework and hydrogeological conceptual models, and incorporates the most updated, best-estimated input parameters. This mountain-scale TH model simulates the coupled TH processes related to mountain-scale multiphase fluid flow, and evaluates the impact of radioactive waste heat on the hydrogeological system, including thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. For a better description of the ambient geothermal condition of the unsaturated zone system, the TH model is first calibrated against measured borehole temperature data. The ambient temperature calibration provides the necessary surface and water table boundary as well as initial conditions. Then, the TH model is used to obtain scientific understanding of TH processes in the Yucca Mountain unsaturated zone under the designed schedule of repository thermal load
3D coupled heat and mass transfer processes at the scale of sedimentary basisn
Cacace, M.; Scheck-Wenderoth, M.; Kaiser, B. O.
2014-12-01
We use coupled 3D simulations of fluid, heat, and transport based on a 3D structural model of a complex geological setting, the Northeast German Basin (NEGB). The geological structure of the NEGB is characterized by a relatively thick layer of Permian Zechstein salt, structured in differnet diapirs (up to 5000 m thick) and pillows locally reaching nearly the surface. Salt is thermally more conductive than other sediments, hydraulically impervious but highly solvable. Thus salt structures have first order influence on the temperature distribution, the deep flow regime and the salinity of groundawater bearing aquifers. In addition, the post-Permian sedimentary sequence is vertically subdivided into several aquifers and aquitards. The shallow Quaternary to late Tertiary freshwater aquifer is separated from the underlying Mesozoic saline aquifers by an embedded Tertiary clay enriched aquitard (Rupelian Aquitard). An important feature of this aquitard is that hydraulic connections between the upper and lower aquifers exist in areas where the Rupelian Aquitard is missing (hydrogeological windows). By means of 3D numerical simulations we explore the role of heat conduction, pressure, and density driven groundwater flow as well as fluid viscosity-related and salinity-dependent effects on the resulting flow and temperature fields. Our results suggest that the regional temperature distribution within the basin results from interactions between regional pressure forces and thermal diffusion locally enhanced by thermal conductivity contrasts between the different sedimentary rocks with the highly conductive salt. Buoyancy forces triggered by temperature-dependent fluid density variations affect only locally the internal thermal configuration. Locations, geometry, and wavelengths of convective thermal anomalies are mainly controlled by the permeability field and thickness values of the respective geological layers. Numerical results from 3D thermo-haline numerical simulations
Bacon, D H
2013-01-01
Basic Heat Transfer aims to help readers use a computer to solve heat transfer problems and to promote greater understanding by changing data values and observing the effects, which are necessary in design and optimization calculations.The book is concerned with applications including insulation and heating in buildings and pipes, temperature distributions in solids for steady state and transient conditions, the determination of surface heat transfer coefficients for convection in various situations, radiation heat transfer in grey body problems, the use of finned surfaces, and simple heat exc
Energy Technology Data Exchange (ETDEWEB)
Lee, Jung Eui; Yeo, Tae Jung; Oh, Kyu Hwan; Yoon, Jong Kyu [School of Materials Science and Engineering, Seoul Nat` l Univ., Seoul (Korea, Republic of); Han, Heung Nam [Oxford Center for Advanced Materials and Composites, Department of Materials, Univ. of Oxford (United Kingdom)
1998-12-31
A mathematical model for a coupled analysis of fluid flow, heat transfer and deformation behavior in the continuously cast beam blank has been developed. The fluid flow, heat transfer and solidification in the mold region were analyzed with 3-dimensional finite difference method (FDM) based on control volume method. A body fitted coordinate system was introduced for the complex geometry of the beam blank. The effects of turbulence and natural convection of molten steel were taken into account in determining the fluid flow in the strand. The thermo-elasto-plastic deformation behavior in the cast strand and the formation of air gap between the solidifying shell and the mold were analyzed by the finite element method (FEM) using the 2-dimensional slice temperature profile calculated by the FDM. The heat flow between the strand and the mold was evaluated by the coupled analysis between the fluid flow-heat transfer analysis and the thermo-elasto-plastic stress analysis. In order to determine the solid fraction in the mushy zone, the microsegregation of solute element was assessed. The effects of fluid flow on the heat transfer, the solidification of steel and the distribution of shell thickness during the casting of the beam blank were simulated. The deformation behavior of the solidifying shell and the possibility of cracking of the strand were also investigated. The recirculating flows were developed in the regions of the web and the flange tip. The impinging of the inlet flow from the nozzle retarded the growing of solidifying shell in the regions of the fillet and the flange. The air gap between the strand and the mold was formed near the region of the corner of the flange tip. At the initial stage of casting, the probability of the surface cracking was high in the regions of the fillet and the flange tip. After the middle stage of casting, the internal cracking was predicted in the regions of the flange tip, and between the fillet and the flange tip. (author) 38
Energy Technology Data Exchange (ETDEWEB)
Lee, Jung Eui; Yeo, Tae Jung; Oh, Kyu Hwan; Yoon, Jong Kyu [School of Materials Science and Engineering, Seoul Nat`l Univ., Seoul (Korea, Republic of); Han, Heung Nam [Oxford Center for Advanced Materials and Composites, Department of Materials, Univ. of Oxford (United Kingdom)
1997-12-31
A mathematical model for a coupled analysis of fluid flow, heat transfer and deformation behavior in the continuously cast beam blank has been developed. The fluid flow, heat transfer and solidification in the mold region were analyzed with 3-dimensional finite difference method (FDM) based on control volume method. A body fitted coordinate system was introduced for the complex geometry of the beam blank. The effects of turbulence and natural convection of molten steel were taken into account in determining the fluid flow in the strand. The thermo-elasto-plastic deformation behavior in the cast strand and the formation of air gap between the solidifying shell and the mold were analyzed by the finite element method (FEM) using the 2-dimensional slice temperature profile calculated by the FDM. The heat flow between the strand and the mold was evaluated by the coupled analysis between the fluid flow-heat transfer analysis and the thermo-elasto-plastic stress analysis. In order to determine the solid fraction in the mushy zone, the microsegregation of solute element was assessed. The effects of fluid flow on the heat transfer, the solidification of steel and the distribution of shell thickness during the casting of the beam blank were simulated. The deformation behavior of the solidifying shell and the possibility of cracking of the strand were also investigated. The recirculating flows were developed in the regions of the web and the flange tip. The impinging of the inlet flow from the nozzle retarded the growing of solidifying shell in the regions of the fillet and the flange. The air gap between the strand and the mold was formed near the region of the corner of the flange tip. At the initial stage of casting, the probability of the surface cracking was high in the regions of the fillet and the flange tip. After the middle stage of casting, the internal cracking was predicted in the regions of the flange tip, and between the fillet and the flange tip. (author) 38
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.
Directory of Open Access Journals (Sweden)
WANG Fang
2017-04-01
Full Text Available Aimed to insufficient heat transfer of heat exchanger, research the influence on the heat transfer coefficient impacted by velocity and heat transfer temperature difference of tube heat exchanger. According to the different heat transfer temperature difference and gas velocity，the experimental data were divided into group. Using the control variable method，the above two factors were analyzed separately. K一△T and k一:fitting curve were clone to obtain empirical function. The entire heat exchanger is as the study object，using numerical simulation methods，porous media，k一￡model，second order upwind mode，and pressure一velocity coupling with SIMPLE algorithm，the entire heat exchanger temperature field and the heat transfer coefficient distribution were given. Finally the trend of the heat transfer coefficient effected by the above two factors was gotten.
Heat Transfer in a Thermoacoustic Process
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…
Yeckel, Andrew; Lun, Lisa; Derby, Jeffrey J.
2009-12-01
A new, approximate block Newton (ABN) method is derived and tested for the coupled solution of nonlinear models, each of which is treated as a modular, black box. Such an approach is motivated by a desire to maintain software flexibility without sacrificing solution efficiency or robustness. Though block Newton methods of similar type have been proposed and studied, we present a unique derivation and use it to sort out some of the more confusing points in the literature. In particular, we show that our ABN method behaves like a Newton iteration preconditioned by an inexact Newton solver derived from subproblem Jacobians. The method is demonstrated on several conjugate heat transfer problems modeled after melt crystal growth processes. These problems are represented by partitioned spatial regions, each modeled by independent heat transfer codes and linked by temperature and flux matching conditions at the boundaries common to the partitions. Whereas a typical block Gauss-Seidel iteration fails about half the time for the model problem, quadratic convergence is achieved by the ABN method under all conditions studied here. Additional performance advantages over existing methods are demonstrated and discussed.
Directory of Open Access Journals (Sweden)
Vasyl Chekurin
2017-01-01
Full Text Available The mathematical model for describing combined conductive-radiative heat transfer in a dielectric layer, which emits, absorbs, and scatters IR radiation both in its volume and on the boundary, has been considered. A nonlinear stationary boundary-value problem for coupled heat and radiation transfer equations for the layer, which exchanges by energy with external medium by convection and radiation, has been formulated. In the case of optically thick layer, when its thickness is much more of photon-free path, the problem becomes a singularly perturbed one. In the inverse case of optically thin layer, the problem is regularly perturbed, and it becomes a regular (unperturbed one, when the layer’s thickness is of order of several photon-free paths. An iterative method for solving of the unperturbed problem has been developed and its convergence has been tested numerically. With the use of the method, the temperature field and radiation fluxes have been studied. The model and method can be used for development of noncontact methods for temperature testing in dielectrics and for nondestructive determination of its radiation properties on the base of the data obtained by remote measuring of IR radiation emitted by the layer.
Feng, S; Ng, C W W; Leung, A K; Liu, H W
2017-10-01
Microbial aerobic methane oxidation in unsaturated landfill cover involves coupled water, gas and heat reactive transfer. The coupled process is complex and its influence on methane oxidation efficiency is not clear, especially in steep covers where spatial variations of water, gas and heat are significant. In this study, two-dimensional finite element numerical simulations were carried out to evaluate the performance of unsaturated sloping cover. The numerical model was calibrated using a set of flume model test data, and was then subsequently used for parametric study. A new method that considers transient changes of methane concentration during the estimation of the methane oxidation efficiency was proposed and compared against existing methods. It was found that a steeper cover had a lower oxidation efficiency due to enhanced downslope water flow, during which desaturation of soil promoted gas transport and hence landfill gas emission. This effect was magnified as the cover angle and landfill gas generation rate at the bottom of the cover increased. Assuming the steady-state methane concentration in a cover would result in a non-conservative overestimation of oxidation efficiency, especially when a steep cover was subjected to rainfall infiltration. By considering the transient methane concentration, the newly-modified method can give a more accurate oxidation efficiency. Copyright © 2017. Published by Elsevier Ltd.
Directory of Open Access Journals (Sweden)
Mehrdad Shahmohammadi Beni
2017-06-01
Full Text Available Cold plasmas were proposed for treatment of leukemia. In the present work, conceptual designs of mixing chambers that increased the contact between the two fluids (plasma and blood through addition of obstacles within rectangular-block-shaped chambers were proposed and the dynamic mixing between the plasma and blood were studied using the level set method coupled with heat transfer. Enhancement of mixing between blood and plasma in the presence of obstacles was demonstrated. Continuous tracking of fluid mixing with determination of temperature distributions was enabled by the present model, which would be a useful tool for future development of cold plasma devices for treatment of blood-related diseases such as leukemia.
International Nuclear Information System (INIS)
Cheng, Z.D.; He, Y.L.; Cui, F.Q.
2013-01-01
This paper presents an axisymmetric steady-state computational fluid dynamics model and further studies on the complex coupled heat transfer combined radiation–convection–conduction in the pressurized volumetric receiver (PVR), by combining the Finite Volume Method (FVM) and the Monte Carlo Ray-Trace (MCRT) method. Based on this, effects of geometric parameters of the compound parabolic concentrator (CPC) and properties of the porous absorber on synthetical characteristics and performance of the photo-thermal conversion process in the PVR are further analyzed and discussed detailedly. It is found that the solar flux density distributions are always very heterogeneous with large nonuniformities, and the variation trends of the corresponding temperature distributions are very similar to these but with much lower order of magnitude. The CPC shape determined by the CPC exit aperture has much larger effects on synthetical characteristics and performance of the PVR than that of the CPC entry aperture with a constant acceptance angle. And a suitable or optimal thickness of the porous absorber could be determined by examining where the drastic decreasing trends occur at the curves of variations of synthetical characteristics and performance with the porosity. - Highlights: ► An axisymmetric steady-state CFD model of PVR is presented with MCRT–FVM method. ► The complex coupled heat transfer and synthetical performance of the PVR are studied. ► The effects of geometric parameters and porous properties are analyzed and discussed. ► Solar flux and temperature in PVR are very heterogeneous with large nonuniformities. ► An optimal absorber thickness can be determined by examining the effects of porosity.
Containment condensing heat transfer
International Nuclear Information System (INIS)
Gido, R.G.; Koestel, A.
1983-01-01
This report presents a mechanistic heat-transfer model that is valid for large scale containment heat sinks. The model development is based on the determination that the condensation is controlled by mass diffusion through the vapor-air boundary layer, and the application of the classic Reynolds' analogy to formulate expressions for the transfer of heat and mass based on hydrodynamic measurements of the momentum transfer. As a result, the analysis depends on the quantification of the shear stress (momentum transfer) at the interface between the condensate film and the vapor-air boundary layer. In addition, the currently used Tagami and Uchida test observations and their range of applicability are explained
Bejan, Adrian
2013-01-01
Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.
REA, The Editors of
1988-01-01
REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Heat Transfer II reviews correlations for forced convection, free convection, heat exchangers, radiation heat transfer, and boiling and condensation.
Hartnett, James P; Cho, Young I; Greene, George A
2001-01-01
Heat transfer is the exchange of heat energy between a system and its surrounding environment, which results from a temperature difference and takes place by means of a process of thermal conduction, mechanical convection, or electromagnetic radiation. Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university-level textbooks by providing in-depth review articles over a broader scope than is allowable in either journals or texts.
Modest, Michael F
2013-01-01
The third edition of Radiative Heat Transfer describes the basic physics of radiation heat transfer. The book provides models, methodologies, and calculations essential in solving research problems in a variety of industries, including solar and nuclear energy, nanotechnology, biomedical, and environmental. Every chapter of Radiative Heat Transfer offers uncluttered nomenclature, numerous worked examples, and a large number of problems-many based on real world situations-making it ideal for classroom use as well as for self-study. The book's 24 chapters cover the four major areas in the field: surface properties; surface transport; properties of participating media; and transfer through participating media. Within each chapter, all analytical methods are developed in substantial detail, and a number of examples show how the developed relations may be applied to practical problems. It is an extensive solution manual for adopting instructors. Features: most complete text in the field of radiative heat transfer;...
Directory of Open Access Journals (Sweden)
Anastasios Georgoulas
2017-02-01
Full Text Available The present numerical investigation identifies quantitative effects of fundamental controlling parameters on the detachment characteristics of isolated bubbles in cases of pool boiling in the nucleate boiling regime. For this purpose, an improved Volume of Fluid (VOF approach, developed previously in the general framework of OpenFOAM Computational Fluid Dynamics (CFD Toolbox, is further coupled with heat transfer and phase change. The predictions of the model are quantitatively verified against an existing analytical solution and experimental data in the literature. Following the model validation, four different series of parametric numerical experiments are performed, exploring the effect of the initial thermal boundary layer (ITBL thickness for the case of saturated pool boiling of R113 as well as the effects of the surface wettability, wall superheat and gravity level for the cases of R113, R22 and R134a refrigerants. It is confirmed that the ITBL is a very important parameter in the bubble growth and detachment process. Furthermore, for all of the examined working fluids the bubble detachment characteristics seem to be significantly affected by the triple-line contact angle (i.e., the wettability of the heated plate for equilibrium contact angles higher than 45°. As expected, the simulations revealed that the heated wall superheat is very influential on the bubble growth and detachment process. Finally, besides the novelty of the numerical approach, a last finding is the fact that the effect of the gravity level variation in the bubble detachment time and the volume diminishes with the increase of the ambient pressure.
Han, Je-Chin
2012-01-01
… it will complete my library … [and] complement the existing literature on heat transfer. It will be of value for both graduate students and faculty members.-Bengt Sunden, Lund University, Sweden
DEFF Research Database (Denmark)
Feyissa, Aberham Hailu; Gernaey, Krist; Adler-Nissen, Jens
2012-01-01
to uncertainty in the model predictions. The aim of the current paper is to address this uncertainty challenge in the modelling of food production processes using a combination of uncertainty and sensitivity analysis, where the uncertainty analysis and global sensitivity analysis were applied to a heat and mass......Similar to other processes, the modelling of heat and mass transfer during food processing involves uncertainty in the values of input parameters (heat and mass transfer coefficients, evaporation rate parameters, thermo-physical properties, initial and boundary conditions) which leads...
International Nuclear Information System (INIS)
Weisman, J.
1983-01-01
Heat may be defined as that form of energy which spontaneously flows between two bodies, or two regions of a body, by virtue of a temperature difference. The second law of thermodynamics tells us that we cannot have heat flow from a low temperature to high temperature without doing work. Heat flows spontaneously from a high temperature to a low temperature region. Thermodynamics, which is concerned with equilibrium states, cannot tell us anything about the rate of heat flow in the presence of a finite temperature difference. It is to the discipline of heat transfer to which we must turn for this answer
Lienhard, John H
2011-01-01
This introduction to heat transfer offers advanced undergraduate and graduate engineering students a solid foundation in the subjects of conduction, convection, radiation, and phase-change, in addition to the related topic of mass transfer. A staple of engineering courses around the world for more than three decades, it has been revised and updated regularly by the authors, a pair of recognized experts in the field. The text addresses the implications, limitations, and meanings of many aspects of heat transfer, connecting the subject to its real-world applications and developing students' ins
Elementary heat transfer analysis
Whitaker, Stephen; Hartnett, James P
1976-01-01
Elementary Heat Transfer Analysis provides information pertinent to the fundamental aspects of the nature of transient heat conduction. This book presents a thorough understanding of the thermal energy equation and its application to boundary layer flows and confined and unconfined turbulent flows. Organized into nine chapters, this book begins with an overview of the use of heat transfer coefficients in formulating the flux condition at phase interface. This text then explains the specification as well as application of flux boundary conditions. Other chapters consider a derivation of the tra
Karwa, Rajendra
2017-01-01
This textbook presents the classical treatment of the problems of heat transfer in an exhaustive manner with due emphasis on understanding of the physics of the problems. This emphasis is especially visible in the chapters on convective heat transfer. Emphasis is laid on the solution of steady and unsteady two-dimensional heat conduction problems. Another special feature of the book is a chapter on introduction to design of heat exchangers and their illustrative design problems. A simple and understandable treatment of gaseous radiation has been presented. A special chapter on flat plate solar air heater has been incorporated that covers thermo-hydraulic modeling and simulation. The chapter on mass transfer has been written looking specifically at the needs of the students of mechanical engineering. The book includes a large number and variety of solved problems with supporting line diagrams. The author has avoided duplicating similar problems, while incorporating more application-based examples. All the end-...
Energy Technology Data Exchange (ETDEWEB)
Piro, M.H.A., E-mail: markuspiro@gmail.com [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Banfield, J. [Nuclear Engineering Department, University of Tennessee, Knoxville, TN (United States); Clarno, K.T., E-mail: clarnokt@ornl.gov [Reactor and Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Simunovic, S. [Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Besmann, T.M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Lewis, B.J.; Thompson, W.T. [Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON (Canada)
2013-10-15
Predictive capabilities for simulating irradiated nuclear fuel behavior are enhanced in the current work by coupling thermochemistry, isotopic evolution and heat transfer. Thermodynamic models that are incorporated into this framework not only predict the departure from stoichiometry of UO{sub 2}, but also consider dissolved fission and activation products in the fluorite oxide phase, noble metal inclusions, secondary oxides including uranates, zirconates, molybdates and the gas phase. Thermochemical computations utilize the spatial and temporal evolution of the fission and activation product inventory in the pellet, which is typically neglected in nuclear fuel performance simulations. Isotopic computations encompass the depletion, decay and transmutation of more than 2000 isotopes that are calculated at every point in space and time. These computations take into consideration neutron flux depression and the increased production of fissile plutonium near the fuel pellet periphery (i.e., the so-called “rim effect”). Thermochemical and isotopic predictions are in very good agreement with reported experimental measurements of highly irradiated UO{sub 2} fuel with an average burnup of 102 GW d t(U){sup −1}. Simulation results demonstrate that predictions are considerably enhanced when coupling thermochemical and isotopic computations in comparison to empirical correlations. Notice: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.
Kovtanyuk, Andrey E.
2012-01-01
Radiative-conductive heat transfer in a medium bounded by two reflecting and radiating plane surfaces is considered. This process is described by a nonlinear system of two differential equations: an equation of the radiative heat transfer and an equation of the conductive heat exchange. The problem is characterized by anisotropic scattering of the medium and by specularly and diffusely reflecting boundaries. For the computation of solutions of this problem, two approaches based on iterative techniques are considered. First, a recursive algorithm based on some modification of the Monte Carlo method is proposed. Second, the diffusion approximation of the radiative transfer equation is utilized. Numerical comparisons of the approaches proposed are given in the case of isotropic scattering. © 2011 Elsevier Ltd. All rights reserved.
Thermal radiation heat transfer
Howell, John R; Mengüç, M Pinar
2011-01-01
Providing a comprehensive overview of the radiative behavior and properties of materials, the fifth edition of this classic textbook describes the physics of radiative heat transfer, development of relevant analysis methods, and associated mathematical and numerical techniques. Retaining the salient features and fundamental coverage that have made it popular, Thermal Radiation Heat Transfer, Fifth Edition has been carefully streamlined to omit superfluous material, yet enhanced to update information with extensive references. Includes four new chapters on Inverse Methods, Electromagnetic Theory, Scattering and Absorption by Particles, and Near-Field Radiative Transfer Keeping pace with significant developments, this book begins by addressing the radiative properties of blackbody and opaque materials, and how they are predicted using electromagnetic theory and obtained through measurements. It discusses radiative exchange in enclosures without any radiating medium between the surfaces-and where heat conduction...
Heat transfer fluids containing nanoparticles
Singh, Dileep; Routbort, Jules; Routbort, A.J.; Yu, Wenhua; Timofeeva, Elena; Smith, David S.; France, David M.
2016-05-17
A nanofluid of a base heat transfer fluid and a plurality of ceramic nanoparticles suspended throughout the base heat transfer fluid applicable to commercial and industrial heat transfer applications. The nanofluid is stable, non-reactive and exhibits enhanced heat transfer properties relative to the base heat transfer fluid, with only minimal increases in pumping power required relative to the base heat transfer fluid. In a particular embodiment, the plurality of ceramic nanoparticles comprise silicon carbide and the base heat transfer fluid comprises water and water and ethylene glycol mixtures.
International Nuclear Information System (INIS)
Welty, J.R.
1974-01-01
The basic concepts of heat transfer are covered with special emphasis on up-to-date techniques for formulating and solving problems in the field. The discussion progresses logically from phenomenology to problem solving, and treats numerical, integral, and graphical methods as well as traditional analytical ones. The book is unique in its thorough coverage of the fundamentals of numerical analysis appropriate to solving heat transfer problems. This coverage includes several complete and readable examples of numerical solutions, with discussions and interpretations of results. The book also contains an appendix that provides students with physical data for often-encountered materials. An index is included. (U.S.)
International Nuclear Information System (INIS)
1992-01-01
This volume contains the 4 key-note lectures and 83 of the 148 papers presented at the 3rd UK National Conference on Heat Transfer. The papers are grouped under the following broad headings: boiling and condensation; heat exchangers; refrigeration and air-conditioning; natural convection; process safety and nuclear reactors; two-phase flow; post dry-out; combustion, radiation and chemical reaction. Separate abstracts have been prepared for 13 papers of relevance to nuclear reactors. (UK)
Enhanced Condensation Heat Transfer
Rose, John Winston
The paper gives some personal observations on various aspects of enhanced condensation heat transfer. The topics discussed are external condensation (horizontal low-finned tubes and wire-wrapped tubes), internal condensation (microfin tubes and microchannels) and Marangoni condensation of binary mixtures.
International Nuclear Information System (INIS)
Muresan, Cristian; Vaillon, Rodolphe; Menezo, Christophe; Morlot, Rodolphe
2004-01-01
The coupled conductive radiative heat transfer in a two-layer slab with Fresnel interfaces subject to diffuse and obliquely collimated irradiation is solved. The collimated and diffuse components problems are treated separately. The solution for diffuse radiation is obtained by using a composite discrete ordinates method and includes the development of adaptive directional quadratures to overcome the difficulties usually encountered at the interfaces. The complete radiation numerical model is validated against the predictions obtained by using the Monte Carlo method
International Nuclear Information System (INIS)
Thomas, A; Maranzana, G; Didierjean, S; Dillet, J; Lottin, O
2012-01-01
Measurements of electrode temperatures within a proton exchange membrane fuel cell were performed using platinum wires. A temperature difference of 7°C between the electrodes and the bipolar plates was observed for a cell operating at a current density of 1.5 A.cm −2 . These measurements show a strong non-uniformity of the temperature profile through membrane electrode assembly (MEA) that future phenomenological models must take into account. In addition, the simultaneous measurements of heat and water flux through the MEA leads to the conclusion that produced water crosses the diffusion layer in vapor phase. A very simple heat transfer model is proposed.
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.
Kilic, V. T.; Unal, E.; Demir, H. V.
2017-07-01
We propose and demonstrate a highly effective method of enhancing coupling and power transfer efficiency in inductive heating systems composed of planar coils. The proposed method is based on locating ring-shaped ferrites in the inner side of the coils in the same plane. Measurement results of simple inductive heating systems constructed with either a single or a pair of conventional circular coils show that, with the in-plane inner ferrites, the total dissipated power of the system is increased by over 65%. Also, with three-dimensional full electromagnetic solutions, it is found that power transfer efficiency of the system is increased up to 92% with the inner ferrite placement. The proposed method is promising to be used for efficiency enhancement in inductive heating applications, especially in all-surface induction hobs.
Energy Technology Data Exchange (ETDEWEB)
Bhattacharyya, A
1965-11-15
This report contains descriptions of various analogues utilised to study different steady-state and unsteady-state heat transfer problems. The analogues covered are as follows: 1 . Hydraulic: a) water flow b) air flow 2. Membrane 3. Geometric Electrical: a) Electrolytic-tank b) Conducting sheet 4. Network; a) Resistance b) R-C A comparison of the different analogues is presented in the form of a table.
International Nuclear Information System (INIS)
Bhattacharyya, A.
1965-11-01
This report contains descriptions of various analogues utilised to study different steady-state and unsteady-state heat transfer problems. The analogues covered are as follows: 1 . Hydraulic: a) water flow b) air flow 2. Membrane 3. Geometric Electrical: a) Electrolytic-tank b) Conducting sheet 4. Network; a) Resistance b) R-C A comparison of the different analogues is presented in the form of a table
Nucleate boiling heat transfer
Energy Technology Data Exchange (ETDEWEB)
Saiz Jabardo, J.M. [Universidade da Coruna (Spain). Escola Politecnica Superior], e-mail: mjabardo@cdf.udc.es
2009-07-01
Nucleate boiling heat transfer has been intensely studied during the last 70 years. However boiling remains a science to be understood and equated. In other words, using the definition given by Boulding, it is an 'insecure science'. It would be pretentious of the part of the author to explore all the nuances that the title of the paper suggests in a single conference paper. Instead the paper will focus on one interesting aspect such as the effect of the surface microstructure on nucleate boiling heat transfer. A summary of a chronological literature survey is done followed by an analysis of the results of an experimental investigation of boiling on tubes of different materials and surface roughness. The effect of the surface roughness is performed through data from the boiling of refrigerants R-134a and R-123, medium and low pressure refrigerants, respectively. In order to investigate the extent to which the surface roughness affects boiling heat transfer, very rough surfaces (4.6 {mu}m and 10.5 {mu}m ) have been tested. Though most of the data confirm previous literature trends, the very rough surfaces present a peculiar behaviour with respect to that of the smoother surfaces (Ra<3.0 {mu}m). (author)
Nucleate boiling heat transfer
International Nuclear Information System (INIS)
Saiz Jabardo, J.M.
2009-01-01
Nucleate boiling heat transfer has been intensely studied during the last 70 years. However boiling remains a science to be understood and equated. In other words, using the definition given by Boulding, it is an 'insecure science'. It would be pretentious of the part of the author to explore all the nuances that the title of the paper suggests in a single conference paper. Instead the paper will focus on one interesting aspect such as the effect of the surface microstructure on nucleate boiling heat transfer. A summary of a chronological literature survey is done followed by an analysis of the results of an experimental investigation of boiling on tubes of different materials and surface roughness. The effect of the surface roughness is performed through data from the boiling of refrigerants R-134a and R-123, medium and low pressure refrigerants, respectively. In order to investigate the extent to which the surface roughness affects boiling heat transfer, very rough surfaces (4.6 μm and 10.5 μm ) have been tested. Though most of the data confirm previous literature trends, the very rough surfaces present a peculiar behaviour with respect to that of the smoother surfaces (Ra<3.0 μm). (author)
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Koplow, Jeffrey P.
2016-02-16
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
Conjugate Heat Transfer Study in Hypersonic Flows
Sahoo, Niranjan; Kulkarni, Vinayak; Peetala, Ravi Kumar
2018-04-01
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.
Directory of Open Access Journals (Sweden)
Yunlu Pan
2018-05-01
Full Text Available As a significant interfacial property for micro/nano fluidic system, the effective boundary slip can be induced by the surface roughness. However, the effect of surface roughness on the effective slip is still not clear, both increased and decreased effective boundary slip were found with increased roughness. The present work develops a simplified model to study the effect of surface roughness on the effective boundary slip. In the created rough models, the reference position of the rough surfaces to determinate effective boundary slip was set based on ISO/ASME standard and the surface roughness parameters including Ra (arithmetical mean deviation of the assessed profile, Rsm (mean width of the assessed profile elements and shape of the texture varied to form different surface roughness. Then, the effective boundary slip of fluid flow through the rough surface was analyzed by using COMSOL 5.3. The results show that the effective boundary slip induced by surface roughness of fully wetted rough surface keeps negative and further decreases with increasing Ra or decreasing Rsm. Different shape of roughness texture also results in different effective slip. A simplified corrected method for the measured effective boundary slip was developed and proved to be efficient when the Rsm is no larger than 200 nm. Another important finding in the present work is that the convective heat transfer firstly increases followed by an unobvious change with increasing Ra, while the effective boundary slip keeps decreasing. It is believed that the increasing Ra enlarges the area of solid-liquid interface for convective heat transfer, however, when Ra is large enough, the decreasing roughness-induced effective boundary slip counteracts the enhancement effect of roughness itself on the convective heat transfer.
Heat transfer bibliography: russian works
Energy Technology Data Exchange (ETDEWEB)
Luikov, A V
1965-02-01
This bibliography of recent Russian publications in heat transfer is divided into the following categories: (1) books; (2) general; (3) experimental methods; (4) analytical calculation methods; (5) thermodynamics; (6) transfer processes involving phase conversions; ((7) transfer processes involving chemical conversions; (8) transfer processes involving very high velocities; (9) drying processes; (10) thermal properties of various materials, heat transfer agents and their determination methods; (11) high temperature physics and magneto- hydrodynamics; and (12) transfer processes in technological apparatuses. (357 refs.)
Liquid metal heat transfer issues
International Nuclear Information System (INIS)
Hoffman, H.W.; Yoder, G.L.
1984-01-01
An alkali liquid metal cooled nuclear reactor coupled with an alkali metal Rankine cycle provides a practicable option for space systems/missions requiring power in the 1 to 100 MW(e) range. Thermal issues relative to the use of alkali liquid metals for this purpose are identified as these result from the nature of the alkali metal fluid itself, from uncertainties in the available heat transfer correlations, and from design and performance requirements for system components operating in the earth orbital microgravity environment. It is noted that, while these issues require further attention to achieve optimum system performance, none are of such magnitude as to invalidate this particular space power concept
Measuring of heat transfer coefficient
DEFF Research Database (Denmark)
Henningsen, Poul; Lindegren, Maria
Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...
Heat transfer between adsorbate and laser-heated hot electrons
International Nuclear Information System (INIS)
Ueba, H; Persson, B N J
2008-01-01
Strong short laser pulses can give rise to a strong increase in the electronic temperature at metal surfaces. Energy transfer from the hot electrons to adsorbed molecules may result in adsorbate reactions, e.g. desorption or diffusion. We point out the limitations of an often used equation to describe the heat transfer process in terms of a friction coupling. We propose a simple theory for the energy transfer between the adsorbate and hot electrons using a newly introduced heat transfer coefficient, which depends on the adsorbate temperature. We calculate the transient adsorbate temperature and the reaction yield for a Morse potential as a function of the laser fluency. The results are compared to those obtained using a conventional heat transfer equation with temperature-independent friction. It is found that our equation of energy (heat) transfer gives a significantly lower adsorbate peak temperature, which results in a large modification of the reaction yield. We also consider the heat transfer between different vibrational modes excited by hot electrons. This mode coupling provides indirect heating of the vibrational temperature in addition to the direct heating by hot electrons. The formula of heat transfer through linear mode-mode coupling of two harmonic oscillators is applied to the recent time-resolved study of carbon monoxide and atomic oxygen hopping on an ultrafast laser-heated Pt(111) surface. It is found that the maximum temperature of the frustrated translation mode can reach high temperatures for hopping, even when direct friction coupling to the hot electrons is not strong enough
aerodynamics and heat transfer
Directory of Open Access Journals (Sweden)
J. N. Rajadas
1998-01-01
Full Text Available A multidisciplinary optimization procedure, with the integration of aerodynamic and heat transfer criteria, has been developed for the design of gas turbine blades. Two different optimization formulations have been used. In the first formulation, the maximum temperature in the blade section is chosen as the objective function to be minimized. An upper bound constraint is imposed on the blade average temperature and a lower bound constraint is imposed on the blade tangential force coefficient. In the second formulation, the blade average and maximum temperatures are chosen as objective functions. In both formulations, bounds are imposed on the velocity gradients at several points along the surface of the airfoil to eliminate leading edge velocity spikes which deteriorate aerodynamic performance. Shape optimization is performed using the blade external and coolant path geometric parameters as design variables. Aerodynamic analysis is performed using a panel code. Heat transfer analysis is performed using the finite element method. A gradient based procedure in conjunction with an approximate analysis technique is used for optimization. The results obtained using both optimization techniques are compared with a reference geometry. Both techniques yield significant improvements with the multiobjective formulation resulting in slightly superior design.
Heat transfer from internally heated hemispherical pools
International Nuclear Information System (INIS)
Gabor, J.D.; Ellsion, P.G.; Cassulo, J.C.
1980-01-01
Experiments were conducted on heat transfer from internally heated ZnSO 4 -H 2 O pools to the walls of hemispherical containers. This experimental technique provides data for a heat transfer system that has to date been only theoretically treated. Three different sizes of copper hemispherical containers were used: 240, 280, 320 mm in diameter. The pool container served both as a heat transfer surface and as an electrode. The opposing electrode was a copper disk, 50 mm in diameter located at the top of the pool in the center. The top surface of the pool was open to the atmosphere
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...
Institute of Scientific and Technical Information of China (English)
LI Xiao-Yan; YANG Yan-Hua; XU Ji-Jun
2003-01-01
Extremely rapid evaporation could occur when high-temperature particles contact withlow-temperature liquid. This kind of phenomenon is associated with the engineering safety and the problems inhigh-transient multi-phase fluid and heat transfer. The aim of our study was to design and build an observable ex-periment facility. The first series of experiments were performed by pouring one or six high-temperature particles intoa low saturated temperature liquid pool. The particle's falling-down speed was recorded by a high-speed camera, thuswe can find the special resistant feature of the moving high-temperature particles, which is induced by the high-speedevaporation surrounding the particles. The study has experimentally verified the theory of evaporation drag model.
Directory of Open Access Journals (Sweden)
Wei Cai
2014-06-01
Full Text Available The convective drying kinetics of porous medium was investigated numerically. A mathematical model for forced convective drying was established to estimate the evolution of moisture content and temperature inside multilayered porous medium. The set of coupled partial differential equations with the specified boundary and initial conditions were solved numerically using a MATLAB code. An experimental setup of convective drying had been constructed and validated the theoretical model. The temperature and moisture content of the potato samples were dynamically measured and recorded during the drying process. Results indicate that thermal diffusion coefficient has significant positive impact on temperature distribution and mass diffusion coefficient might directly affect the moisture content distribution. Soret effect has a significant impact on heat flux and temperature distribution in the presence of large temperature gradient.
International Nuclear Information System (INIS)
Mukhopadhyay, Sumit; Sonnenthal, Eric L.; Spycher, Nicolas
2007-01-01
When hot radioactive waste is placed in subsurface tunnels, a series of complex changes occurs in the surrounding medium. The water in the pore space of the medium undergoes vaporization and boiling. Subsequently, vapor migrates out of the matrix pore space, moving away from the tunnel through the permeable fracture network. This migration is propelled by buoyancy, by the increased vapor pressure caused by heating and boiling, and through local convection. In cooler regions, the vapor condenses on fracture walls, where it drains through the fracture network. Slow imbibition of water thereafter leads to gradual rewetting of the rock matrix. These thermal and hydrological processes also bring about chemical changes in the medium. Amorphous silica precipitates from boiling and evaporation, and calcite from heating and CO2 volatilization. The precipitation of amorphous silica, and to a much lesser extent calcite, results in long-term permeability reduction. Evaporative concentration also results in the precipitation of gypsum (or anhydrite), halite, fluorite and other salts. These evaporative minerals eventually redissolve after the boiling period is over, however, their precipitation results in a significant temporary decrease in permeability. Reduction of permeability is also associated with changes in fracture capillary characteristics. In short, the coupled thermal-hydrological-chemical (THC) processes dynamically alter the hydrological properties of the rock. A model based on the TOUGHREACT reactive transport software is presented here to investigate the impact of THC processes on flow near an emplacement tunnel at Yucca Mountain, Nevada. We show how transient changes in hydrological properties caused by THC processes often lead to local flow channeling and saturation increases above the tunnel. For models that include only permeability changes to fractures, such local flow channeling may lead to seepage relative to models where THC effects are ignored. However
International Nuclear Information System (INIS)
Mukhopadhyay, S.; Sonnenthal, E.L.; Spycher, N.
2007-01-01
When hot radioactive waste is placed in subsurface tunnels, a series of complex changes occurs in the surrounding medium. The water in the pore space of the medium undergoes vaporization and boiling. Subsequently, vapor migrates out of the matrix pore space, moving away from the tunnel through the permeable fracture network. This migration is propelled by buoyancy, by the increased vapor pressure caused by heating and boiling, and through local convection. In cooler regions, the vapor condenses on fracture walls, where it drains through the fracture network. Slow imbibition of water thereafter leads to gradual rewetting of the rock matrix. These thermal and hydrological processes also bring about chemical changes in the medium. Amorphous silica precipitates from boiling and evaporation, and calcite from heating and CO 2 volatilization. The precipitation of amorphous silica, and to a much lesser extent calcite, results in long-term permeability reduction. Evaporative concentration also results in the precipitation of gypsum (or anhydrite), halite, fluorite and other salts. These evaporative minerals eventually redissolve after the boiling period is over, however, their precipitation results in a significant temporary decrease in permeability. Reduction of permeability is also associated with changes in fracture capillary characteristics. In short, the coupled thermal-hydrological-chemical (THC) processes dynamically alter the hydrological properties of the rock. A model based on the TOUGHREACT reactive transport software is presented here to investigate the impact of THC processes on flow near an emplacement tunnel at Yucca Mountain, Nevada. We show how transient changes in hydrological properties caused by THC processes often lead to local flow channeling and saturation increases above the tunnel. For models that include only permeability changes to fractures, such local flow channeling may lead to seepage relative to models where THC effects are ignored. However
International Nuclear Information System (INIS)
Cleveland, J.C.
1977-01-01
CORTAP (Core Transient Analysis Program) was developed to predict the dynamic behavior of the High Temperature Gas Cooled Reactor (HTGR) core under normal operational transients and postulated accident conditions. CORTAP is used both as a stand-alone component simulation and as part of the HTGR nuclear steam supply (NSS) system simulation code ORTAP. The core thermal neutronic response is determined by solving the heat transfer equations for the fuel, moderator and coolant in an average powered region of the reactor core. The space independent neutron kinetics equations are coupled to the heat transfer equations through a rapidly converging iterative technique. The code has the capability to determine conservative fuel, moderator, and coolant temperatures in the ''hot'' fuel region. For transients involving a reactor trip, the core heat generation rate is determined from an expression for decay heat following a scram. Nonlinear effects introduced by temperature dependent fuel, moderator, and coolant properties are included in the model. CORTAP predictions will be compared with dynamic test results obtained from the Fort St. Vrain reactor owned by Public Service of Colorado, and, based on these comparisons, appropriate improvements will be made in CORTAP
International Nuclear Information System (INIS)
Yamamoto, Takahisa; Mitachi, Koshi
2004-01-01
This paper performed the transient core analysis of a small Molten Salt Reactor (MSR). The emphasis is that the numerical model employed in this paper takes into account the interaction among fuel salt flow, nuclear reaction and heat transfer. The model consists of two group diffusion equations for fast and thermal neutron fluexs, balance equations for six-group delayed neutron precursors and energy conservation equations for fuel salt and graphite moderator. The results of transient analysis are that (1) fission reaction (heat generation) rate significantly increases soon after step reactivity insertion, e.g., the peak of fission reaction rate achieves about 2.7 times larger than the rated power 350 MW when the reactivity of 0.15% Δk/k 0 is inserted to the rated state, and (2) the self-control performance of the small MSR effectively works under the step reactivity insertion of 0.56% Δk/k 0 , putting the fission reaction rate back on the rated state. (author)
Energy Technology Data Exchange (ETDEWEB)
Ramousse, J
2005-11-15
Understanding and modelling of coupled mass, charges and heat transfers phenomena are fundamental to analyze the electrical behaviour of the system. The aim of the present model is to describe electrical performances of a PEFMC according to the fluidic and thermal operating conditions. The water content of the membrane and the water distribution in the single cell are estimated according to the coupled simulations of mass transport in the thickness of the single cell and in the feeding channels of the bipolar plates. A microscopic model of a Gas Diffusion Electrode is built up to describe charges transfer phenomena occurring at the electrodes. Completed by a study of heat transfer in the Membrane Electrode Assembly, conditions and preferential sites of water vapor condensation can be highlighted. A set of measurements of the effective thermal conductivity of carbon felts used in fuel cells as porous backing layers have also been performed. Although the value of this parameter is essential for the study of heat transfer, it is still under investigation because of the strong thermal anisotropy of the medium. (author)
Kaviany, Massoud
2014-01-01
This graduate textbook describes atomic-level kinetics (mechanisms and rates) of thermal energy storage, transport (conduction, convection, and radiation), and transformation (various energy conversions) by principal energy carriers. The approach combines the fundamentals of molecular orbitals-potentials, statistical thermodynamics, computational molecular dynamics, quantum energy states, transport theories, solid-state and fluid-state physics, and quantum optics. The textbook presents a unified theory, over fine-structure/molecular-dynamics/Boltzmann/macroscopic length and time scales, of heat transfer kinetics in terms of transition rates and relaxation times, and its modern applications, including nano- and microscale size effects. Numerous examples, illustrations, and homework problems with answers that enhance learning are included. This new edition includes applications in energy conversion (including chemical bond, nuclear, and solar), expanded examples of size effects, inclusion of junction quantum tr...
Energy Technology Data Exchange (ETDEWEB)
Muller, J [IRSID, Institut de Recherches Siderurgie, 57 - Maizieres-les-Metz (France)
1997-12-31
Radiant heat transfer is the main solution retained in many iron and steel metallurgy installations (re-heating and annealing furnaces etc..). Today, it has become important to dispose of performing radiant heat transfer models in heat transfer and fluid mechanics simulation softwares, and well adapted to multidimensional industrial problems. This work presents the discrete ordinate radiant heat transfer model developed at the IRSID (the French institute of research in iron and steel metallurgy) and coupled with the PHOENICS heat transfer-fluid mechanics software. Three modeling approaches are presented concerning the radiative properties of gases (H{sub 2}O-CO{sub 2}). A ``weighted grey gases sum`` model gives satisfactory results for several 1-D validation cases. (J.S.) 20 refs.
Energy Technology Data Exchange (ETDEWEB)
Muller, J. [IRSID, Institut de Recherches Siderurgie, 57 - Maizieres-les-Metz (France)
1996-12-31
Radiant heat transfer is the main solution retained in many iron and steel metallurgy installations (re-heating and annealing furnaces etc..). Today, it has become important to dispose of performing radiant heat transfer models in heat transfer and fluid mechanics simulation softwares, and well adapted to multidimensional industrial problems. This work presents the discrete ordinate radiant heat transfer model developed at the IRSID (the French institute of research in iron and steel metallurgy) and coupled with the PHOENICS heat transfer-fluid mechanics software. Three modeling approaches are presented concerning the radiative properties of gases (H{sub 2}O-CO{sub 2}). A ``weighted grey gases sum`` model gives satisfactory results for several 1-D validation cases. (J.S.) 20 refs.
Heat Transfer Basics and Practice
Böckh, Peter
2012-01-01
The book provides an easy way to understand the fundamentals of heat transfer. The reader will acquire the ability to design and analyze heat exchangers. Without extensive derivation of the fundamentals, the latest correlations for heat transfer coefficients and their application are discussed. The following topics are presented - Steady state and transient heat conduction - Free and forced convection - Finned surfaces - Condensation and boiling - Radiation - Heat exchanger design - Problem-solving After introducing the basic terminology, the reader is made familiar with the different mechanisms of heat transfer. Their practical application is demonstrated in examples, which are available in the Internet as MathCad files for further use. Tables of material properties and formulas for their use in programs are included in the appendix. This book will serve as a valuable resource for both students and engineers in the industry. The author’s experience indicates that students, after 40 lectures and exercises ...
Heat transfer direction dependence of heat transfer coefficients in annuli
Prinsloo, Francois P. A.; Dirker, Jaco; Meyer, Josua P.
2018-04-01
In this experimental study the heat transfer phenomena in concentric annuli in tube-in-tube heat exchangers at different annular Reynolds numbers, annular diameter ratios, and inlet fluid temperatures using water were considered. Turbulent flow with Reynolds numbers ranging from 15,000 to 45,000, based on the average bulk fluid temperature was tested at annular diameter ratios of 0.327, 0.386, 0.409 and 0.483 with hydraulic diameters of 17.00, 22.98, 20.20 and 26.18 mm respectively. Both heated and cooled annuli were investigated by conducting tests at a range of inlet temperatures between 10 °C to 30 °C for heating cases, and 30 °C to 50 °C for cooling cases. Of special interest was the direct measurement of local wall temperatures on the heat transfer surface, which is often difficult to obtain and evasive in data-sets. Continuous verification and re-evaluation of temperatures measurements were performed via in-situ calibration. It is shown that inlet fluid temperature and the heat transfer direction play significant roles on the magnitude of the heat transfer coefficient. A new adjusted Colburn j-factor definition is presented to describe the heating and cooling cases and is used to correlate the 894 test cases considered in this study.
Heat transfer in a thermoacoustic process
International Nuclear Information System (INIS)
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 aimed at determining the stability–instability border of the thermoacoustic system. In this paper, we present a project type of physical examination and modelling task. We employed an electrically heated Rijke tube in our thermoacoustic project work. The aim of our project is to help our students enlarge their knowledge about thermodynamics, mainly about thermoacoustics, and develop their applied information technology and mathematical skills. (paper)
Condensation heat transfer in plate heat exchangers
International Nuclear Information System (INIS)
Panchal, C.B.
1985-01-01
An Alfa-Laval plate heat exchanger, previously tested as an evaporator, was retested as a condenser. Two series of tests with different chevron-angle plates were carried out using ammonia as a working fluid. The overall heat-transfer coefficient and pressure drop were measured, and the effects of operating parameters were determined. The experimental data were compared with theoretical predictions. In the analysis, a gravity-controlled condensation process was modeled theoretically, and the overall performance was calculated. The analysis shows that the overall heat-transfer coefficient can be predicted with an average uncertainty of about 10%. It is, however, important to consider the interfacial shear stress, because the effective friction factor is high for flow in plate heat exchangers
Radiation and combined heat transfer in channels
International Nuclear Information System (INIS)
Tamonis, M.
1986-01-01
This book presents numerical methods of calculation of radiative and combined heat transfer in channel flows of radiating as well as nonradiating media. Results obtained in calculations for flow conditions of combustion products from organic fuel products are given and methods used in determining the spectral optical properties of molecular gases are analyzed. The book presents applications of heat transfer in solving problems. Topic covered are as follows: optical properties of molecular gases; transfer equations for combined heat transfer; experimental technique; convective heat transfer in heated gas flows; radiative heat transfer in gaseous media; combined heat transfer; and radiative and combined heat transfer in applied problems
Heat Transfer in Complex Fluids
Energy Technology Data Exchange (ETDEWEB)
Mehrdad Massoudi
2012-01-01
fluids show Newtonian (linear) behavior for a given range of parameters or geometries; there are many empirical or semi-empirical constitutive equations suggested for these fluids. There have also been many non-linear constitutive relations which have been derived based on the techniques of continuum mechanics. The non-linearities oftentimes appear due to higher gradient terms or time derivatives. When thermal and or chemical effects are also important, the (coupled) momentum and energy equations can give rise to a variety of interesting problems, such as instability, for example the phenomenon of double-diffusive convection in a fluid layer. In Conclusion, we have studied the flow of a compressible (density gradient type) non-linear fluid down an inclined plane, subject to radiation boundary condition. The heat transfer is also considered where a source term, similar to the Arrhenius type reaction, is included. The non-dimensional forms of the equations are solved numerically and the competing effects of conduction, dissipation, heat generation and radiation are discussed. It is observed that the velocity increases rapidly in the region near the inclined surface and is slower in the region near the free surface. Since R{sub 7} is a measure of the heat generation due to chemical reaction, when the reaction is frozen (R{sub 7}=0.0) the temperature distributions would depend only on R{sub 1}, and R{sub 2}, representing the effects of the pressure force developed in the material due to the distribution, R{sub 3} and R{sub 4} viscous dissipation, R{sub 5} the normal stress coefficient, R{sub 6} the measure of the emissivity of the particles to the thermal conductivity, etc. When the flow is not frozen (RP{sub 7} > 0) the temperature inside the flow domain is much higher than those at the inclined and free surfaces. As a result, heat is transferred away from the flow toward both the inclined surface and the free surface with a rate that increases as R{sub 7} increases. For a
Advances in heat transfer enhancement
Saha, Sujoy Kumar; Sundén, Bengt; Wu, Zan
2016-01-01
This Brief addresses the phenomena of heat transfer enhancement. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to three other monographs including “Critical Heat Flux in Flow Boiling in Microchannels,” this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.
Energy Technology Data Exchange (ETDEWEB)
Heselhaus, A.
1997-05-01
In this work a hybrid program system consisting of a 3D finite-volume Navier-Stokes flow solver and a 3D finite-element heat conduction solver has been developed. It enables the coupled calculation of structure temperatures in diabatic solid/fluid configurations. The grids of both the finite element and the finite volume computational domain may be completely independent. The coupled program fully resolves the thermal interaction between heat transfer and the resulting material temperatures. The developed coupling algorithm is numerically stable, conservative and works without the need to define ambient temperatures in the flowfield. This allows for the simulation of any solid/fluid configuration. When simulating combined blade/endwall cooling or filmcooling, only a coupled procedure is capable to completely account for the interaction between all relevant thermal parameters. It is found that the coupled calculation of convective cooling in a realistic guide vane leads locally to 45 K higher and 107 K lower blade temperatures than the uncoupled calculation. This shows that accounting for the thermal interaction between the flow and the structure offers both potential to save cooling air and a lower margin of safety when designing cooling systems close to the thermal limits of the blade material. (orig.) [Deutsch] Im Rahmen der vorliegenden Arbeit wurde ein Verfahren zur Berechnung der Temperaturverteilung in diabat umstroemten Koerpern entwickelt, bei dem ein 3D-Finite Volumen Navier-Stokes Stroemungsloeser und ein 3D-Finite Elemente Waermeleitungsloeser zu einem hybriden Programmsystem gekoppelt werden. Dabei besteht die Moeglichkeit, voellig unabhaengige Rechennetze fuer Stroemung und Struktur zu verwenden. Mit dem gekoppelten Verfahren kann die Wechselwirkung zwischen resultierenden Materialtemperaturen und dem davon rueck-beeinflussten Waermeuebergang beruecksichtigt werden. Weiterhin ist der hier entwickelte, stabile und konservative Kopplungsalgorithmus nicht
Fundamental principles of heat transfer
Whitaker, Stephen
1977-01-01
Fundamental Principles of Heat Transfer introduces the fundamental concepts of heat transfer: conduction, convection, and radiation. It presents theoretical developments and example and design problems and illustrates the practical applications of fundamental principles. The chapters in this book cover various topics such as one-dimensional and transient heat conduction, energy and turbulent transport, forced convection, thermal radiation, and radiant energy exchange. There are example problems and solutions at the end of every chapter dealing with design problems. This book is a valuable int
Heat transfer enhancement with nanofluids
Bianco, Vincenzo; Nardini, Sergio; Vafai, Kambiz
2015-01-01
Properties of NanofluidSamuel Paolucci and Gianluca PolitiExact Solutions and Their Implications in Anomalous Heat TransferWenhao Li, Chen Yang and Akira NakayamaMechanisms and Models of Thermal Conductivity in NanofluidsSeung-Hyun Lee and Seok Pil JangExperimental Methods for the Characterization of Thermophysical Properties of NanofluidsSergio Bobbo and Laura FedeleNanofluid Forced ConvectionGilles RoyExperimental Study of Convective Heat Transfer in NanofluidsEhsan B. Haghighi, Adi T. Utomo, Andrzej W. Pacek and Björn E. PalmPerformance of Heat Exchangers Using NanofluidsBengt Sundén and Za
DEFF Research Database (Denmark)
Jabbari, Masoud; Hattel, Jesper
2016-01-01
process of thin sheets produced by the tape casting process. The rate of mass loss in the drying process is a key factor that often is of interest, as it affects the final properties of the tapes. The 1D heat conduction equation is solved numerically to obtain the temperature field in a ceramic sheet...... dominant since the fraction of water approaches zero. The developed model is used to simulate a simple test for the drying process. The drying rate is simply calculated by examining the water content in each time step. It is found that the mass loss due to the evaporation is increasing close to linearly...
Annaratone, Donatello
2010-01-01
This book is a generalist textbook; it is designed for anybody interested in heat transmission, including scholars, designers and students. Two criteria constitute the foundation of Annaratone's books, including the present one. The first one consists of indispensable scientific rigor without theoretical exasperation. The inclusion in the book of some theoretical studies, even if admirable for their scientific rigor, would have strengthened the scientific foundation of this publication, yet without providing the reader with further applicable know-how. The second criterion is to deliver practi
Heat transfer from rough surfaces
International Nuclear Information System (INIS)
Dalle Donne, M.
1977-01-01
Artificial roughness is often used in nuclear reactors to improve the thermal performance of the fuel elements. Although these are made up of clusters of rods, the experiments to measure the heat transfer and friction coefficients of roughness are performed with single rods contained in smooth tubes. This work illustrated a new transformation method to obtain data applicable to reactor fuel elements from these annulus experiments. New experimental friction data are presented for ten rods, each with a different artificial roughness made up of two-dimensional rectangular ribs. For each rod four tests have been performed, each in a different outer smooth tube. For two of these rods, each for two different outer tubes, heat transfer data are also given. The friction and heat transfer data, transformed with the present method, are correlated by simple equations. In the paper, these equations are applied to a case typical for a Gas Cooled Fast Reactor fuel element. (orig.) [de
Essentials of radiation heat transfer
Balaji
2014-01-01
Essentials of Radiation Heat Transfer is a textbook presenting the essential, fundamental information required to gain an understanding of radiation heat transfer and equips the reader with enough knowledge to be able to tackle more challenging problems. All concepts are reinforced by carefully chosen and fully worked examples, and exercise problems are provided at the end of every chapter. In a significant departure from other books on this subject, this book completely dispenses with the network method to solve problems of radiation heat transfer in surfaces. It instead presents the powerful radiosity-irradiation method and shows how this technique can be used to solve problems of radiation in enclosures made of one to any number of surfaces. The network method is not easily scalable. Secondly, the book introduces atmospheric radiation, which is now being considered as a potentially important area, in which engineers can contribute to the technology of remote sensing and atmospheric sciences in general, b...
Mills, A F
1999-01-01
The Second Edition offers complete coverage of heat transfer with broad up-to-date coverage that includes an emphasis on engineering relevance and on problem solving. Integrates software to assist the reader in efficiently calculations. Carefully orders material to make book more reader-friendly and accessible. Offers an extensive introduction to heat exchange design to enhance the engineering and design content of course to satisfy ABET requirements. For professionals in engineering fields.
Heat transfer characteristics of a direct contact heat exchanger
International Nuclear Information System (INIS)
Kinoshita, I.; Nishi, Y.
1993-01-01
As a first step for development of a direct contact steam generator for FBRs, fundamental heat transfer characteristics of a liquid-liquid contact heat exchanger were evaluated by heat transfer experiment with low melting point alloy and water. Distinctive characteristics of direct contact heat transfer with liquid metal and water was obtained. (author)
Heat transfer study under supercritical pressure conditions
International Nuclear Information System (INIS)
Yamashita, Tohru; Yoshida, Suguru; Mori, Hideo; Morooka, Shinichi; Komita, Hideo; Nishida, Kouji
2003-01-01
Experiments were performed on heat transfer and pressure drop of a supercritical pressure fluid flowing upward in a uniformly heated vertical tube of a small diameter, using HCFC22 as a test fluid. Following results were obtained. (1) Characteristics of the heat transfer are similar to those for the tubes of large diameter. (2) The effect of tube diameter on the heat transfer was seen for a 'normal heat transfer, but not for a 'deteriorated' heat transfer. (3) The limit heat flux for the occurrence of deterioration in heat transfer becomes larger with smaller diameter tube. (4) The Watts and Chou correlation has the best prediction performance for the present data in the 'normal' heat transfer region. (5) Frictional pressure drop becomes smaller than that for an isothermal flow in the region near the pseudocritical point, and this reduction was more remarkable for the deteriorated' heat transfer. (author)
Visualisation of heat transfer in laminar flows
Speetjens, M.F.M.; Steenhoven, van A.A.
2009-01-01
Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients at non-adiabatic walls. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the
RELAP4/MOD6 reflood heat transfer and data comparison
International Nuclear Information System (INIS)
Nelson, R.A.; Sullivan, L.H.
1981-01-01
This discussion of RELAP4/MOD6 will be limited to the reflood heat transfer models and evaluation of these models by comparison of calculation with results from three reflood experiments. The discussion of the model includes the heat transfer surface concept, the heat transfer correlations, the superheat model and the entrainment model which presents both the two-phase heat transfer and hydraulic models. In the discussion of the reflood heat transfer, the mathematical concept of a multidimensional surface is used to represent the heat flux of a given heat transfer correlation or correlations dependent upon such variables as quality, wall superheat and flux. This concept has been used to investigate the characteristics of the correlations, which are discusssed in detail, and the way they are applied to the two-phase mixture. Of primary importance in the reflood core heat transfer is the consideration of thermal nonequilibrium between the phases and the liquid entrainment, and its distribution up the core. Results obtained to date show the heat transfer and hydraulics to be closely coupled. Comparison of the RELAP4/MOD6 reflood calculations with the data from the forced feed FLECHT and gravity feed FLECHT-SET and Semiscale reflood experiments indicates that the heat transfer and hydraulic models are operational and yield good results
MHTGR inherent heat transfer capability
International Nuclear Information System (INIS)
Berkoe, J.M.
1992-01-01
This paper reports on the Commercial Modular High Temperature Gas-Cooled Reactor (MHTGR) which achieves improved reactor safety performance and reliability by utilizing a completely passive natural convection cooling system called the RCCS to remove decay heat in the event that all active cooling systems fail to operate. For the highly improbable condition that the RCCS were to become non-functional following a reactor depressurization event, the plant would be forced to rely upon its inherent thermo-physical characteristics to reject decay heat to the surrounding earth and ambient environment. A computational heat transfer model was created to simulate such a scenario. Plant component temperature histories were computed over a period of 20 days into the event. The results clearly demonstrate the capability of the MHTGR to maintain core integrity and provide substantial lead time for taking corrective measures
Heat and mass transfer in buildings
International Nuclear Information System (INIS)
Kristoffersen, Astrid Rusaas
2005-01-01
This thesis has presented four journal papers about ventilation and heat transfer in buildings. Ventilation and heat transfer in buildings are elements that decide our indoor air quality, thermal comfort and energy use in buildings. Models and experiments are tools to understand the complex physics of heat and air transfer in buildings. As computers are, getting cheaper and more powerful, there is a need to develop reliable models that can predict heat and air transfer in buildings. The first paper in this thesis addressed the widely used multizone model. This model is mainly used to find the airflows between zones in a building. A multizone model is often coupled to an energy analysis program, and affects therefore the calculated energy use in a building. The first paper in this thesis, titled ''Effect of room air recirculation delay on the decay rate of tracer gas concentration'' discussed the impact of a recirculating ventilation system on the decay of the tracer gas concentration in the room. The delay of the tracer gas through the ventilation system affects the concentration in the room, and must be accounted for when calculating the amount of fresh air that the ventilation system supplies. The second paper titled ''CFD Investigation of Room Ventilation for Improved Operation of a Downdraft Table: Novel Concepts'' investigated the performance of a downdraft table by changing the ventilation configuration in the room by use of Computational Fluid Dynamics (CFD). CFD can provide a microscopic description of the airflow and the behavior of pollutants and temperature distribution in a room. This paper calculated the airflow pattern in the room without influence of thermal effects, and demonstrated the usage of CFD. It was found that the total airflow could be reduced compared to an existing configuration (and hence reduce energy costs), and at the same time increasing the performance of the downdraft table (increasing the indoor air quality). A room with a
Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants
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.
Radiation effects on heat transfer in heat exchangers, (2)
International Nuclear Information System (INIS)
Mori, Yasuo; Watanabe, Kenji; Taira, Tatsuji.
1980-01-01
In a high temperature gas-cooled reactor system, in which the working fluid exchanges heat at high temperature near 1000 deg C, the heat transfer acceleration by positively utilizing the radiation heat transfer between solid surfaces should be considered. This paper reports on the results of experiment and analysis for the effects of radiant heat on the heat transfer performance at elevated temperature by applying the heat transfer-accelerating method using radiators to the heat exchanger with tube bundle composed of two channels of heating and heated sides. As the test heat exchangers, a parallel counter flow exchanger and the cross flow exchanger simulating helical tubes were employed, and the results studied on the characteristics of each heat exchanger are described. The plates placed in parallel to flow in every space of the tube bundle arranged in a matrix were used as the heat transfer accelerator. The effects of acceleration with the plates were the increase of heat transmission from 12 to 24% and 12 to 38% in the parallel flow and cross flow heat exchangers, respectively. Also, it was clarified that the theoretical analysis, in which it was assumed that the region within pitch S and two radiator plates, with a heat-transferring tube placed at the center, is the minimum domain for calculation, and that the heat exchange by radiation occurs only between the domain and the adjacent domains, can estimate the heat transfer-accelerating effect and the temperature distribution in a heat exchanger with sufficient accuracy. (Wakatsuki, Y.)
Heat transfer--Orlando (Symposium), 1980
International Nuclear Information System (INIS)
Stein, R.P.
1980-01-01
This conference proceedings contains 36 papers of which 3 appear as abstracts. 23 papers are indexed separately. Topics covered include: thermodynamics of PWR and LMFBR Steam Generators; two-phase flow in parallel channels; geothermal heat transfer; natural circulation in complex geometries; heat transfer in non-Newtonian systems; and process heat transfer
Research progress on microgravity boiling heat transfer
International Nuclear Information System (INIS)
Xiao Zejun; Chen Bingde
2003-01-01
Microgravity boiling heat transfer is one of the most basic research topics in aerospace technology, which is important for both scientific research and engineering application. Research progress on microgravity boiling heat transfer is presented, including terrestrial simulation technique, terrestrial simulation experiment, microgravity experiment, and flow boiling heat transfer
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2013-12-10
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Transient heat transfer characteristics of liquid helium
International Nuclear Information System (INIS)
Tsukamoto, Osami
1976-01-01
The transient heat transfer characteristics of liquid helium are investigated. The critical burnout heat fluxes for pulsive heating are measured, and empirical relations between the critical burnout heat flux and the length of the heat pulse are given. The burnout is detected by observing the super-to-normal transition of the temperature sensor which is a thin lead film prepared on the heated surface by vacuum evaporation. The mechanism of boiling heat transfer for pulsive heating is discussed, and theoretical relations between the critical burnout heat flux and the length of the heat pulse are derived. The empirical data satisfy the theoretical relations fairly well. (auth.)
International Nuclear Information System (INIS)
Guangming, Xiao; Yanxia, Du; Yewei, Gui; Lei, Liu; Xiaofeng, Yang; Dong, Wei
2014-01-01
The theories of heat transfer, thermodynamics and fluid dynamics are employed to develop the coupled heat transfer analytical methods for the heat-pipe-cooled thermal protection structure (HPC TPS), and a three-dimensional numerical method considering the sonic limit of heat pipe is proposed. To verify the calculation correctness, computations are carried out for a typical heat pipe and the results agree well with experimental data. Then, the heat transfer characteristics and limitations of HPC TPS are mainly studied. The studies indicate that the use of heat pipe can reduce the temperature at high heat flux region of structure efficiently. However, there is a frozen startup period before the heat pipe reaching a steady operating state, and the sonic limit will be a restriction on the heat transfer capability. Thus, the effects of frozen startup must be considered for the design of HPC TPS. The simulation model and numerical method proposed in this paper can predict the heat transfer characteristics of HPC TPS quickly and exactly, and the results will provide important references for the design or performance evaluation of HPC TPS. - Highlights: • Numerical methods for the heat-pipe-cooled thermal protection structure are studied. • Three-dimensional simulation model considering sonic limit of heat pipe is proposed. • The frozen startup process of the embedded heat pipe can be predicted exactly. • Heat transfer characteristics of TPS and limitations of heat pipe are discussed
Porous media heat transfer for injection molding
Beer, Neil Reginald
2016-05-31
The cooling of injection molded plastic is targeted. Coolant flows into a porous medium disposed within an injection molding component via a porous medium inlet. The porous medium is thermally coupled to a mold cavity configured to receive injected liquid plastic. The porous medium beneficially allows for an increased rate of heat transfer from the injected liquid plastic to the coolant and provides additional structural support over a hollow cooling well. When the temperature of the injected liquid plastic falls below a solidifying temperature threshold, the molded component is ejected and collected.
Blowdown heat transfer experiment, (1)
International Nuclear Information System (INIS)
Soda, Kunihisa; Yamamoto, Nobuo; Osaki, Hideki; Shiba, Masayoshi
1976-09-01
Blowdown heat transfer experiment has been carried out with a transparent test section to observe phenomena in coolant behavior during blowdown process. Experimental parameters are discharge position, initial system pressure, initial coolant temperature, power supply to heater rods and number of heater rods. At initial pressure 7-12 ata and initial power 6-50 kw per one heater rod, the flow condition in the test section is a major factor in determining time of DNB occurrence and physical process to DNB during blowdown. (auth.)
Evaluation of heat transfer correlations for HCCI engine modeling
Soyhan, H.S.; Yasar, H.; Walmsley, H.; Head, B.; Kalghatgi, G.T.; Sorusbay, C.
2009-01-01
Combustion in HCCI engines is a controlled auto-ignition of well-mixed fuel, air and residual gas. The thermal conditions of the combustion chamber are governed by chemical kinetics strongly coupled with heat transfer from the hot gas to the walls. The heat losses have a critical effect on HCCI
Tunable heat transfer with smart nanofluids.
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.
Heat transfer coeffcient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1997-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The pipe is heated by condensing R22 outside the pipe. The heat input is supplied by an electrical heater wich evaporates the R22. With the heat flux assumed constant over...... the whole surface and with measured temperature difference between the inner surface and the evaporation temperature a mean heat transfer coefficient is calculated. The calculated heat transfer coefficient has been compared with the Chart Correlation of Shah. The Chart Correlation predicts too low heat...... transfer coefficient but the ratio between the measured and the calculated heat transfer coefficient is nearly constant and equal 1.9. With this factor the correlation predicts the measured data within 14% (RMS). The pressure drop is of the same order as the measuring uncertainty and the pressure drop has...
Boiling heat transfer on horizontal tube bundles
International Nuclear Information System (INIS)
Anon.
1987-01-01
Nucleate boiling heat transfer characteristics for a tube in a bundle differ from that for a single tube in a pool and this difference is known as 'tube bundle effect.' There exist two bundle effects, positive and negative. The positive bundle effect enhances heat transfer due to convective flow induced by rising bubbles generated from the lower tubes, while the negative bundle effect deteriorates heat transfer due to vapor blanketing caused by accumulation of bubbles. Staggered tube bundles tested and found that the upper tubes in bundles have higher heat transfer coefficients than the lower tubes. The effects of various parameters such as pressure, tube geometry and oil contamination on heat transfer have been examined. Some workers attempted to clarify the mechanism of occurrence of 'bundle effect' by testing tube arrangements of small scale. All reported only enhancement in heat transfer but results showed the symptom of heat transfer deterioration at higher heat fluxes. As mentioned above, it has not been clarified so far even whether the 'tube bundle effect' should serve as enhancement or deterioration of heat transfer in nucleate boiling. In this study, experiments are performed in detail by using bundles of small scale, and effects of heat flux distribution, pressure and tube location are clarified. Furthermore, some consideration on the mechanisms of occurrence of 'tube bundle effect' is made and a method for prediction of heat transfer rate is proposed
Engineering calculations in radiative heat transfer
Gray, W A; Hopkins, D W
1974-01-01
Engineering Calculations in Radiative Heat Transfer is a six-chapter book that first explains the basic principles of thermal radiation and direct radiative transfer. Total exchange of radiation within an enclosure containing an absorbing or non-absorbing medium is then described. Subsequent chapters detail the radiative heat transfer applications and measurement of radiation and temperature.
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.
Directory of Open Access Journals (Sweden)
N. Amanifard
2007-06-01
Full Text Available In this work, the effects of electrical double layer (EDL near the solid/ liquid interface, on three dimensional heat transfer characteristic and pressure drop of water flow through a rectangular microchannel numerically are investigated. An additional body force originating from the existence of EDL is considered to modify the conventional Navier-stokes and energy equations. These modified equations are solved numerically for steady laminar flow on the basis of control volume approaches. Fluid velocity distribution and temperature with presence and absence of EDL effects are presented for various geometric cases and different boundary conditions. The results illustrate that, the liquid flow in rectangular microchannels is influenced significantly by the EDL, particularly in the high electric potentials, and hence deviates from flow characteristics described by classical fluid mechanics.
Heat and mass transfer in particulate suspensions
Michaelides, Efstathios E (Stathis)
2013-01-01
Heat and Mass Transfer in Particulate Suspensions is a critical review of the subject of heat and mass transfer related to particulate Suspensions, which include both fluid-particles and fluid-droplet Suspensions. Fundamentals, recent advances and industrial applications are examined. The subject of particulate heat and mass transfer is currently driven by two significant applications: energy transformations –primarily combustion – and heat transfer equipment. The first includes particle and droplet combustion processes in engineering Suspensions as diverse as the Fluidized Bed Reactors (FBR’s) and Internal Combustion Engines (ICE’s). On the heat transfer side, cooling with nanofluids, which include nanoparticles, has attracted a great deal of attention in the last decade both from the fundamental and the applied side and has produced several scientific publications. A monograph that combines the fundamentals of heat transfer with particulates as well as the modern applications of the subject would be...
Industrial furnace with improved heat transfer
Energy Technology Data Exchange (ETDEWEB)
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.
Effect of different heat transfer models on HCCI engine simulation
International Nuclear Information System (INIS)
Neshat, Elaheh; Saray, Rahim Khoshbakhti
2014-01-01
Highlights: • A new multi zone model is developed for HCCI combustion modeling. • New heat transfer model is used for prediction of heat transfer in HCCI engines. • Model can predict engine combustion, performance and emission characteristics well. • Appropriate mass and heat transfer models cause to accurate prediction of CO, UHC and NOx. - Abstract: Heat transfer from engine walls has an important role on engine combustion, performance and emission characteristics. The main focus of this study is offering a new relation for calculation of convective heat transfer from in-cylinder charge to combustion chamber walls of HCCI engines and providing the ability of new model in comparison with the previous models. Therefore, a multi zone model is developed for homogeneous charge compression ignition engine simulation. Model consists of four different types of zones including core zone, boundary layer zone, outer zones, which are between core and boundary layer, and crevice zone. Conductive heat transfer and mass transfer are considered between neighboring zones. For accurate calculation of initial conditions at inlet valve closing, multi zone model is coupled with a single zone model, which simulates gas exchange process. Various correlations are used as convective heat transfer correlations. Woschni, modified Woschni, Hohenberg and Annand correlations are used as convective heat transfer models. The new convection model, developed by authors, is used, too. Comparative analyses are done to recognize the accurate correlation for prediction of engine combustion, performance and emission characteristics in a wide range of operating conditions. The results indicate that utilization of various heat transfer models, except for new convective heat transfer model, leads to significant differences in prediction of in-cylinder pressure and exhaust emissions. Using Woschni, Chang and new model, convective heat transfer coefficient increases near top dead center, sharply
Selection of Rational Heat Transfer Intensifiers in the Heat Exchanger
Directory of Open Access Journals (Sweden)
S. A. Burtsev
2016-01-01
Full Text Available The paper considers the applicability of different types of heat transfer intensifiers in the heat exchange equipment. A review of the experimental and numerical works devoted to the intensification of the dimpled surface, surfaces with pins and internally ribbed surface were presented and data on the thermal-hydraulic characteristics of these surfaces were given. We obtained variation of thermal-hydraulic efficiency criteria for 4 different objective functions and 15 options for the intensification of heat transfer. This makes it possible to evaluate the advantages of the various heat transfer intensifiers. These equations show influence of thermal and hydraulic characteristics of the heat transfer intensifiers (the values of the relative heat transfer and drag coefficients on the basic parameters of the shell-and-tube heat exchanger: the number and length of the tubes, the volume of the heat exchanger matrix, the coolant velocity in the heat exchanger matrix, coolant flow rate, power to pump coolant (or pressure drop, the amount of heat transferred, as well as the average logarithmic temperature difference. The paper gives an example to compare two promising heat transfer intensifiers in the tubes and shows that choosing the required efficiency criterion to search for optimal heat exchanger geometry is of importance. Analysis is performed to show that a dimpled surface will improve the effectiveness of the heat exchanger despite the relatively small value of the heat transfer intensification, while a significant increase in drag of other heat transfer enhancers negatively affects their thermalhydraulic efficiency. For example, when comparing the target functions of reducing the heat exchanger volume, the data suggest that application of dimpled surfaces in various fields of technology is possible. But there are also certain surfaces that can reduce the parameters of a heat exchanger. It is shown that further work development should be aimed at
A literature survey on numerical heat transfer
Shih, T. M.
1982-12-01
Technical papers in the area of numerical heat transfer published from 1977 through 1981 are reviewed. The journals surveyed include: (1) ASME Journal of Heat Transfer, (2) International Journal of Heat and Mass Transfer, (3) AIAA Journal, (4) Numerical Heat Transfer, (5) Computers and Fluids, (6) International Journal for Numerical Methods in Engineering, (7) SIAM Journal of Numerical Analysis, and (8) Journal of Computational Physics. This survey excludes experimental work in heat transfer and numerical schemes that are not applied to equations governing heat transfer phenomena. The research work is categorized into the following areas: (A) conduction, (B) boundary-layer flows, (C) momentum and heat transfer in cavities, (D) turbulent flows, (E) convection around cylinders and spheres or within annuli, (F) numerical convective instability, (G) radiation, (H) combustion, (I) plumes, jets, and wakes, (J) heat transfer in porous media, (K) boiling, condensation, and two-phase flows, (L) developing and fully developed channel flows, (M) combined heat and mass transfer, (N) applications, (O) comparison and properties of numerical schemes, and (P) body-fitted coordinates and nonuniform grids.
Heat transfer coefficient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1998-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio...... between the measured and the calculated heat transfer coefficient is nearly constant and equal 1.9. With this factor the correlation predicts the measured data within 14% (RMS). The pressure drop is of the same order as the measuring uncertainty and the pressure drop has not been compared with correlation's....
Supercritical heat transfer phenomena in nuclear system
International Nuclear Information System (INIS)
Seo, Kyoung Woo; Kim, Moo Hwan; Anderson, Mark H.; Corradini, Michael L.
2005-01-01
A supercritical water (SCW) power cycle has been considered as one of the viable candidates for advanced fission reactor designs. However, the dramatic variation of thermo-physical properties with a modest change of temperature near the pseudo-critical point make existing heat transfer correlations such as the Dittus-Boelter correlation not suitably accurate to calculate the heat transfer in supercritical fluid. Several other correlations have also been suggested but none of them are able to predict the heat transfer over a parameter range, needed for reactor thermal-hydraulics simulation and design. This has prompted additional research to understand the characteristic of supercritical fluid heat transfer
Heat transfer correlations in mantle tanks
DEFF Research Database (Denmark)
Furbo, Simon; Knudsen, Søren
2005-01-01
on calculations with a CFD-model, which has earlier been validated by means of experiments. The CFD-model is used to determine the heat transfer between the solar collector fluid in the mantle and the walls surrounding the mantle in all levels of the mantle as well as the heat transfer between the wall...... transfer correlations are suitable as input for a detailed simulation model for mantle tanks. The heat transfer correlations determined in this study are somewhat different from previous reported heat transfer correlations. The reason is that this study includes more mantle tank designs and operation......Small solar domestic hot water systems are best designed as low flow systems based on vertical mantle tanks. Theoretical investigations of the heat transfer in differently designed vertical mantle tanks during different operation conditions have been carried out. The investigations are based...
Conjugate heat and mass transfer in heat mass exchanger ducts
Zhang, Li-Zhi
2013-01-01
Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi
Experimental and analytical study of natural-convection heat transfer of internally heated liquids
International Nuclear Information System (INIS)
Green, G.A.
1982-08-01
Boundary heat transfer from a liquid pool with a uniform internal heat source to a vertical or inclined boundary was investigated. The experiments were performed in an open rectangular liquid pool in which the internal heat source was generated by electrical heating. The local heat flux was measured to a boron nitride test wall which was able to be continuously inclined from vertical. Gold plated microthermocouples of 0.01 inch outside diameter were developed to measure the local surface temperature, both front and back, of the boron nitride. The local heat flux and, thus, the local heat transfer coefficient was measured at nineteen locations along the vertical axis of the test plate. A theoretical analysis of the coupled nonlinear boundary layer equations was performed. The parametric effect of the Prandtl number and the dimensionless wall temperature on the boundary heat transfer were investigated When the analytical model was used to calculate the boundary heat transfer data, agreement was achieved with the experimental data within 3% for the local heat transfer and within 2% for the average heat transfer
Heat transfer in heterogeneous propellant combustion systems
International Nuclear Information System (INIS)
Brewster, M.Q.
1992-01-01
This paper reports that heat transfer plays an important role in several critical areas of heterogeneous, solid-propellant combustion systems. These areas include heat feedback to the propellant surface, heat transfer between burning aluminum droplets and their surroundings, heat transfer to internal insulation systems, and heat transfer to aft-end equipment. Gas conduction dominates heat feedback to the propellant surface in conventional ammonium perchlorate (AP) composite propellants, although particle radiative feedback also plays a significant role in combustion of metalized propellants. Particle radiation plays a dominant role in heat transfer to internal insulation, compared with that of convection. However, conduction by impingement of burning aluminum particles, which has not been extensively studied, may also be significant. Radiative heat loss plays an important role in determining the burning rate of molten aluminum particles due to a highly luminous, oxide particle-laden, detached flame envelope. Radiation by aluminum oxide smoke particles also plays a dominant role in heat transfer from the exhaust plume to aft-end equipment. Uncertainties in aluminum oxide particle-size distribution and optical properties still make it difficult to predict radiative plume heat transfer accurately from first principles
Heat transfer capability analysis of heat pipe for space reactor
International Nuclear Information System (INIS)
Li Huaqi; Jiang Xinbiao; Chen Lixin; Yang Ning; Hu Pan; Ma Tengyue; Zhang Liang
2015-01-01
To insure the safety of space reactor power system with no single point failures, the reactor heat pipes must work below its heat transfer limits, thus when some pipes fail, the reactor could still be adequately cooled by neighbor heat pipes. Methods to analyze the reactor heat pipe's heat transfer limits were presented, and that for the prevailing capillary limit analysis was improved. The calculation was made on the lithium heat pipe in core of heat pipes segmented thermoelectric module converter (HP-STMC) space reactor power system (SRPS), potassium heat pipe as radiator of HP-STMC SRPS, and sodium heat pipe in core of scalable AMTEC integrated reactor space power system (SAIRS). It is shown that the prevailing capillary limits of the reactor lithium heat pipe and sodium heat pipe is 25.21 kW and 14.69 kW, providing a design margin >19.4% and >23.6%, respectively. The sonic limit of the reactor radiator potassium heat pipe is 7.88 kW, providing a design margin >43.2%. As the result of calculation, it is concluded that the main heat transfer limit of HP-STMC SRPS lithium heat pipe and SARIS sodium heat pipe is prevailing capillary limit, but the sonic limit for HP-STMC SRPS radiator potassium heat pipe. (authors)
Supercritical water gasification with decoupled pressure and heat transfer modules
Dibble, Robert
2017-09-14
The present invention discloses a system and method for supercritical water gasification (SCWG) of biomass materials wherein the system includes a SCWG reactor and a plurality of heat exchangers located within a shared pressurized vessel, which decouples the function of containing high pressure from the high temperature function. The present invention allows the heat transfer function to be conducted independently from the pressure transfer function such that the system equipment can be designed and fabricated in manner that would support commercial scaled-up SCWG operations. By using heat exchangers coupled to the reactor in a series configuration, significant efficiencies are achieved by the present invention SCWG system over prior known SCWG systems.
Heat transfer from humans wearing clothing
Lotens, W.A.
1993-01-01
In this monograph the effects of clothing on human heat transfer are described. The description is based on the physics of heat and mass transfer, depending on the design of the clothing, the climate, and the activity of the wearer. The resulting model has been stepwise implemented in computer
Boiling heat transfer modern developments and advances
Lahey, Jr, RT
2013-01-01
This volume covers the modern developments in boiling heat transfer and two-phase flow, and is intended to provide industrial, government and academic researchers with state-of-the-art research findings in the area of multiphase flow and heat transfer technology. Special attention is given to technology transfer, indicating how recent significant results may be used for practical applications. The chapters give detailed technical material that will be useful to engineers and scientists who work in the field of multiphase flow and heat transfer. The authors of all chapters are members of the
Heat transfer coefficient of cryotop during freezing.
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).
"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"
Energy Technology Data Exchange (ETDEWEB)
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
Phase change heat transfer device for process heat applications
International Nuclear Information System (INIS)
Sabharwall, Piyush; Patterson, Mike; Utgikar, Vivek; Gunnerson, Fred
2010-01-01
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 ∼1300 K) and industrial scale power transport (≥50 MW), 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.
Heat transfer from internally-heated molten UO2 pools
International Nuclear Information System (INIS)
Stein, R.P.; Baker, L. Jr.; Gunther, W.H.; Cook, C.
1978-01-01
Experimental measurements of heat transfer from internally heated pools of molten UO 2 have been obtained for two cell sizes: 10 cm x 10 cm and 20 cm x 20 cm. The experiments with the large cell have supported a previous conclusion from early small data that the measured downward heat fluxes are higher than would be expected on the basis of considerations of thermal convection. A convective model underpredicts the downward heat fluxes by a factor of 2.5 to 4.5 for all but one early experiment. Arbitrary assumptions of increased thermal conductivity do not account for the discrepancy. A single model based on internal thermal radiation heat transfer is able to account for the high values. The model uses the optically thick Rosseland approximation. Because of this, it is tentatively concluded that thermal radiation plays a dominant role in controlling the heat transfer from internally heated molted fuel
Droplet heat transfer and chemical reactions during direct containment heating
International Nuclear Information System (INIS)
Baker, L. Jr.
1986-01-01
A simplified model of heat transfer and chemical reaction has been adapted to evaluate the expected behavior of droplets containing unreacted Zircaloy and stainless steel moving through the containment atmosphere during postulated accidents involving direct containment heating. The model includes internal and external diffusive resistances to reaction. The results indicate that reactions will be incomplete for many conditions characteristic of direct containment heating sequences
Stokes flow heat transfer in an annular, rotating heat exchanger
International Nuclear Information System (INIS)
Saatdjian, E.; Rodrigo, A.J.S.; Mota, J.P.B.
2011-01-01
The heat transfer rate into highly viscous, low thermal-conductivity fluids can be enhanced significantly by chaotic advection in three-dimensional flows dominated by viscous forces. The physical effect of chaotic advection is to render the cross-sectional temperature field uniform, thus increasing both the wall temperature gradient and the heat flux into the fluid. A method of analysis for one such flow-the flow in the eccentric, annular, rotating heat exchanger-and a procedure to determine the best heat transfer conditions, namely the optimal values of the eccentricity ratio and time-periodic rotating protocol, are discussed. It is shown that in continuous flows, such as the one under consideration, there exists an optimum frequency of the rotation protocol for which the heat transfer rate is a maximum. - Highlights: → The eccentric, annular, rotating heat exchanger is studied for periodic Stokes flow. → Counter-rotating the inner tube with a periodic velocity enhances the heat transfer. → The heat-transfer enhancement under such conditions is due to chaotic advection. → For a given axial flow rate there is a frequency that maximizes the heat transfer. → There is also an optimum value of the eccentricity ratio.
Analysis of natural convection heat transfer and flows in internally heated stratified liquid pools
International Nuclear Information System (INIS)
Gubaidullin, A.A. Jr.; Dinh, T.N.; Sehgal, B.R.
1999-01-01
In this paper, natural convection flows and heat transfer in a liquid pool, with two superposed immiscible fluid layers, are analyzed. The objective of the study is to examine the effect of interfacial hydrodynamics and to develop a method which enables energy splitting to be evaluated in a stratified liquid pool. The thermal convection, with and without an internal heat source, in a rectangular cavity with different pairs of fluids was numerically simulated by a CFD code FLOW-3D. It was found that the code performs very well for prediction of heat transfer coefficients for different conditions. The hydrodynamic coupling between immiscible layers was found to have minor, if any, impact on the natural convection heat transfer for the conditions examined. Calculated results were used to develop, and validate, a new correlation for energy splitting and for heat transfer in stratified liquid pools
The magnetic fluid for heat transfer applications
International Nuclear Information System (INIS)
Nakatsuka, K.; Jeyadevan, B.; Neveu, S.; Koganezawa, H.
2002-01-01
Real-time visual observation of boiling water-based and ionic magnetic fluids (MFs) and heat transfer characteristics in heat pipe using ionic MF stabilized by citrate ions (JC-1) as working liquid are reported. Irrespective of the presence or absence of magnetic field water-based MF degraded during boiling. However, the degradation of JC-1 was avoided by heating the fluid in magnetic field. Furthermore, the heat transfer capacity of JC-1 heat pipe under applied magnetic field was enhanced over the no field case
Natural convection heat transfer in SIGMA experiment
International Nuclear Information System (INIS)
Lee, Seung Dong; Lee, Gang Hee; Suh, Kune Yull
2004-01-01
A loss-of-coolant accident (LOCA) results in core melt formation and relocation at various locations within the reactor core over a considerable period of time. If there is no effective cooling mechanism, the core debris may heat up and commence natural circulation. The high temperature pool of molten core material will threaten the structural integrity of the reactor vessel. The extent and urgency of this threat depend primarily upon the intensity of the internal heat sources and upon the consequent distribution of the heat fluxes on the vessel walls in contact with the molten core material pools. In such a steady molten pool convection state, the thermal loads against the vessel would be determined by the in-vessel heat transfer distribution involving convective and conductive heat transfer from the decay-heated core material pool to the lower head wall in contact with the core material. In this study, upward and downward heat transfer fraction ratio is focused on
Component Cooling Heat Exchanger Heat Transfer Capability Operability Monitoring
International Nuclear Information System (INIS)
Mihalina, M.; Djetelic, N.
2010-01-01
The ultimate heat sink (UHS) is of highest importance for nuclear power plant safe and reliable operation. The most important component in line from safety-related heat sources to the ultimate heat sink water body is a component cooling heat exchanger (CC Heat Exchanger). The Component Cooling Heat Exchanger has a safety-related function to transfer the heat from the Component Cooling (CC) water system to the Service Water (SW) system. SW systems throughout the world have been the root of many plant problems because the water source, usually river, lake, sea or cooling pond, are conductive to corrosion, erosion, biofouling, debris intrusion, silt, sediment deposits, etc. At Krsko NPP, these problems usually cumulate in the summer period from July to August, with higher Sava River (service water system) temperatures. Therefore it was necessary to continuously evaluate the CC Heat Exchanger operation and confirm that the system would perform its intended function in accordance with the plant's design basis, given as a minimum heat transfer rate in the heat exchanger design specification sheet. The Essential Service Water system at Krsko NPP is an open cycle cooling system which transfers heat from safety and non-safety-related systems and components to the ultimate heat sink the Sava River. The system is continuously in operation in all modes of plant operation, including plant shutdown and refueling. However, due to the Sava River impurities and our limited abilities of the water treatment, the system is subject to fouling, sedimentation buildup, corrosion and scale formation, which could negatively impact its performance being unable to satisfy its safety related post accident heat removal function. Low temperature difference and high fluid flows make it difficult to evaluate the CC Heat Exchanger due to its specific design. The important effects noted are measurement uncertainties, nonspecific construction, high heat transfer capacity, and operational specifics (e
Heat Transfer in Metal Foam Heat Exchangers at High Temperature
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.
National Research Council Canada - National Science Library
Chow, L
1998-01-01
.... The heat generated from a 9x9-heater array was removed by liquid nitrogen pool boiling. The orientation and space limitation of the array were varied to explore their effects on the critical heat flux (CHF) value...
Heat exchanger network retrofit optimization involving heat transfer enhancement
International Nuclear Information System (INIS)
Wang Yufei; Smith, Robin; Kim, Jin-Kuk
2012-01-01
Heat exchanger network retrofit plays an important role in energy saving in process industry. Many design methods for the retrofit of heat exchanger networks have been proposed during the last three decades. Conventional retrofit methods rely heavily on topology modifications which often result in a long retrofit duration and high initial costs. Moreover, the addition of extra surface area to the heat exchanger can prove difficult due to topology, safety and downtime constraints. Both of these problems can be avoided through the use of heat transfer enhancement in heat exchanger network retrofit. This paper presents a novel design approach to solve heat exchanger network retrofit problems based on heat transfer enhancement. An optimisation method based on simulated annealing has been developed to find the appropriate heat exchangers to be enhanced and to calculate the level of enhancement required. The physical insight of enhanced exchangers is also analysed. The new methodology allows several possible retrofit strategies using different retrofit methods be determined. Comparison of these retrofit strategies demonstrates that retrofit modification duration and payback time are reduced when heat transfer enhancement is utilised. Heat transfer enhancement can be also used as a substitute for increased heat exchanger network surface area to reduce retrofit investment costs.
Heat and mass transfer in the unsteady hydromagnetic free ...
African Journals Online (AJOL)
Heat and mass transfer in the unsteady hydromagnetic free-convection flow in a rotating binary fluid I. ... By imposing a time dependent perturbation on the constant plate temperature and concentration and assuming a differential approximation for the radiative flux, the coupled non linear problem is solved for the ...
Endwall convective heat transfer for bluff bodies
DEFF Research Database (Denmark)
Wang, Lei; Salewski, Mirko; Sundén, Bengt
2012-01-01
The endwall heat transfer characteristics of forced flow past bluff bodies have been investigated using liquid crystal thermography (LCT). The bluff body is placed in a rectangular channel with both its ends attached to the endwalls. The Reynolds number varies from 50,000 to 100,000. In this study......, a single bluff body and two bluff bodies arranged in tandem are considered. Due to the formation of horseshoe vortices, the heat transfer is enhanced appreciably for both cases. However, for the case of two bluff bodies in tandem, it is found that the presence of the second bluff body decreases the heat...... transfer as compared to the case of a single bluff body. In addition, the results show that the heat transfer exhibits Reynolds number similarity. For a single bluff body, the Nusselt number profiles collapse well when the data are scaled by Re0.55; for two bluff bodies arranged in tandem, the heat...
Supercritical heat transfer in an annular channel with external heating
International Nuclear Information System (INIS)
Remizov, O.V.; Gal'chenko, Eh.F.; Shurkin, N.G.; Sergeev, V.V.
1980-01-01
Results are presented of experimental studies of the burnout heat transfer in a 32x28x3000 mm annular channel with a uniform distribution of a heat flow at pressures of 6.9-19.6 MPa and mass rates of 350-1000 kg/m 2 xs. The heating is electrical, external, one-sided. It is shown that dependencies of the heat-transfer coefficient on rated parameters in the annular channel and tube are similar. An empirical equation has been obtained for the calculation of the burnout heat transfer in the annual channels with external heating in the following range: pressure, 6.9 -13.7 MPa; mass rate 350-700 kg/m 2 xs, and steam content ranging from Xsub(crit) to 1
Pumped two-phase heat transfer loop
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.
Forced convection heat transfer in He II
International Nuclear Information System (INIS)
Kashani, A.
1986-01-01
An investigation of forced convection heat transfer in He II is conducted. The study includes both experimental and theoretical treatments of the problem. The experiment consists of a hydraulic pump and a copper flow tube, 3 mm in ID and 2m long. The system allows measurements of one-dimensional heat and mass transfer in He II. The heat transfer experiments are performed by applying heat at the midpoint along the length of the flow tube. Two modes of heat input are employed, i.e., step function heat input and square pulse heat input. The heat transfer results are discussed in terms of temperature distribution in the tube. The experimental temperature profiles are compared with numerical solutions of an analytical model developed from the He II energy equation. The bath temperature is set at three different values of 1.65, 1.80, and 1.95 K. The He II flow velocity is varied up to 90 cm/s. Pressure is monitored at each end of the flow tube, and the He II pressure drop is obtained for different flow velocities. Results indicate that He II heat transfer by forced convention is considerably higher than that by internal convection. The theoretical model is in close agreement with the experiment. He II pressure drop and friction factor are very similar to those of an ordinary fluid
Heat transfer from two-side heated helical channels
International Nuclear Information System (INIS)
Shimonis, V.; Ragaishis, V.; Poshkas, P.
1995-01-01
Experimental results are presented on the heat transfer from two-side heated helical channels to gas (air) flows. The study covered six configurations and wide ranges of geometrical (D/h=5.5 to 84.2) and performance (Re=10 3 to 2*10 5 ) parameters. Under the influence of Re and of the channel curvature, the heat transfer from both the convex and the concave surfaces for two-side heating (q w1 ≅ q w2 ) is augmented by 20-30% over one-side heating. Improved relations to predict the critical values of Reynolds Re cr1 and Re cr2 are suggested. They enable more exact predictions of the heat transfer from convex surface in transient flows for one-side heating. The relation for annular channels is suggested for the turbulent heat transfer from the convex and concave surfaces of two-side heated helical channels. It can be adapted by introducing earlier expresions for one-side heated helical channels. (author). 6 refs., 2 tabs., 3 figs
Interfacial stability with mass and heat transfer
International Nuclear Information System (INIS)
Hsieh, D.Y.
1977-07-01
A simplified formulation is presented to deal with interfacial stability problems with mass and heat transfer. For Rayleigh-Taylor stability problems of a liquid-vapor system, it was found that the effect of mass and heat transfer tends to enhance the stability of the system when the vapor is hotter than the liquid, although the classical stability criterion is still valid. For Kelvin-Holmholtz stability problems, however, the classical stability criterion was found to be modified substantially due to the effect of mass and heat transfer
Boundary control of nonlinear coupled heat systems using backstepping
Bendevis, Paul
2016-10-20
A state feedback boundary controller is designed for a 2D coupled PDE system modelling heat transfer in a membrane distillation system for water desalination. Fluid is separated into two compartments with nonlinear coupling at a membrane boundary. The controller sets the temperature on one boundary in order to track a temperature difference across the membrane boundary. The control objective is achieved by an extension of backstepping methods to these coupled equations. Stability of the target system via Lyapunov like methods, and the invertibility of the integral transformation are used to show the stability of the tracking error.
Coupled qubits as a quantum heat switch
Karimi, B.; Pekola, J. P.; Campisi, M.; Fazio, R.
2017-12-01
We present a quantum heat switch based on coupled superconducting qubits, connected to two LC resonators that are terminated by resistors providing two heat baths. To describe the system, we use a standard second order master equation with respect to coupling to the baths. We find that this system can act as an efficient heat switch controlled by the applied magnetic flux. The flux influences the energy level separations of the system, and under some conditions, the finite coupling of the qubits enhances the transmitted power between the two baths, by an order of magnitude under realistic conditions. At the same time, the bandwidth at maximum power of the switch formed of the coupled qubits is narrowed.
Heat transfer enhancement using 2MHz ultrasound.
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.
Numerical Modeling of Conjugate Heat Transfer in Fluid Network
Majumdar, Alok
2004-01-01
Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.
Heat transfer in an asymmetrically heated duct, 2
International Nuclear Information System (INIS)
Satoh, Isao; Kurosaki, Yasuo
1986-01-01
The objective of this article is to study theoretically and experimentally the effects of nonuniform heating on turbulent heat transfer characteristics for flow in a horizontal rectangular duct ; a vertical side wall was uniformly heated, and the other wall were insulated. In our theoretical approach, the zero-equation model for turbulent eddy viscosity was employed. The effects of mesh size of finite difference on the calculation results were examined, and some refined compensation for wall temperatures and wall shear stresses by no use of fine mesh were proposed to reduce the calculation time. The heat transfer coefficients in thermally developing region for a nonuniformly heated duct obtained from numerical solutions are larger than the one for uniformly heated case. The buoyancy effects on heat transfer were evaluated. However, it was seen that the secondary flow due to buoyancy force was hardly expected to enhance heat transfer in a turbulent duct flow. Experiments were performed to measure the velocity and temperature profiles in a turbulent duct flow with a nonuniform heated wall. The experimental results were in good agreement with the theoretical ones. (author)
Modeling of heat transfer into a heat pipe for a localized heat input zone
International Nuclear Information System (INIS)
Rosenfeld, J.H.
1987-01-01
A general model is presented for heat transfer into a heat pipe using a localized heat input. Conduction in the wall of the heat pipe and boiling in the interior structure are treated simultaneously. The model is derived from circumferential heat transfer in a cylindrical heat pipe evaporator and for radial heat transfer in a circular disk with boiling from the interior surface. A comparison is made with data for a localized heat input zone. Agreement between the theory and the model is good. This model can be used for design purposes if a boiling correlation is available. The model can be extended to provide improved predictions of heat pipe performance
Heat transfer characteristics of the two-phase closed thermosyphon (wickless heat pipe)
International Nuclear Information System (INIS)
Andros, F.E.; Florschuetz, L.W.
1982-01-01
Steady-state heat transfer characteristics and heat transfer limits (dry-out) for a vertical stainless steel tubular two-phase closed thermosyphon with Freon-113 working fluid are reported as a function of certain geometric parameters and liquid fill quantity. Condenser section heat transfer characteristics agreed reasonably well with existing laminar film condensation correlations and were found to be independent of the evaporator section, except for larger liquid fills. Evaporator characteristics were quite complex and appeared, under some conditions, to be coupled to condenser characteristics through effects of system pressure and/or surface wave as present on the descending condensate film. A laminar thin film evaporation model was found to give reasonable agreement with local evaporator temperature measurements in those regions of the evaporator where a continuous film apparently persisted. The measured heat transfer characteristics are interpreted relative to an earlier investigation by the authors in which flow characteristics in a similar device were visually and photographically observed. 10 references
Internally Heated Screw Pyrolysis Reactor (IHSPR) heat transfer performance study
Teo, S. H.; Gan, H. L.; Alias, A.; Gan, L. M.
2018-04-01
1.5 billion end-of-life tyres (ELT) were discarded globally each year and pyrolysis is considered the best solution to convert the ELT into valuable high energy-density products. Among all pyrolysis technologies, screw reactor is favourable. However, conventional screw reactor risks plugging issue due to its lacklustre heat transfer performance. An internally heated screw pyrolysis reactor (IHSPR) was developed by local renewable energy industry, which serves as the research subject for heat transfer performance study of this particular paper. Zero-load heating test (ZLHT) was first carried out to obtain the operational parameters of the reactor, followed by the one dimensional steady-state heat transfer analysis carried out using SolidWorks Flow Simulation 2016. Experiments with feed rate manipulations and pyrolysis products analyses were conducted last to conclude the study.
Heat Transfer Phenomena of Supercritical Fluids
Energy Technology Data Exchange (ETDEWEB)
Krau, Carmen Isabella; Kuhn, Dietmar; Schulenberg, Thomas [Forschungszentrum Karlsruhe, Institute for Nuclear and Energy Technologies, 76021 Karlsruhe (Germany)
2008-07-01
In concepts for supercritical water cooled reactors, the reactor core is cooled and moderated by water at supercritical pressures. The significant temperature dependence of the fluid properties of water requires an exact knowledge of the heat transfer mechanism to avoid fuel pin damages. Near the pseudo-critical point a deterioration of heat transfer might happen. Processes, that take place in this case, are not fully understood and are due to be examined systematically. In this paper a general overview on the properties of supercritical water is given, experimental observations of different authors will be reviewed in order to identify heat transfer phenomena and onset of occurrence. The conceptional design of a test rig to investigate heat transfer in the boundary layer will be discussed. Both, water and carbon dioxide, may serve as operating fluids. The loop, including instrumentation and safety devices, is shown and suitable measuring methods are described. (authors)
Heat transfer studies in pool fire environment
International Nuclear Information System (INIS)
Nitsche, F.
1993-01-01
A Type B package has to withstand severe thermal accident conditions. To calculate the temperature behaviour of such a package in a real fire environment, heat transfer parameters simulating the effect of the fire are needed. For studying such heat transfer parameters, a systematic programme of experimental and theoretical investigations was performed which was part of the IAEA Coordinated Research Programme (Nitsche and Weib 1990). The studies were done by means of small, unfinned and finned, steel model containers of simplified design in hydrocarbon fuel open fire tests. By using various methods, flame and container temperatures were measured and also container surface absorptivity before and after the test to study the effect of sooting and surface painting on heat transfer. Based on all these experimental data and comparative calculations, simplified, effective heat transfer parameters could be derived, simulating the effect of the real fire on the model containers. (J.P.N.)
Transient heat transfer in liquid helium
International Nuclear Information System (INIS)
Shiotsu, Masahiro
1991-01-01
Detailed knowledge on the steady-state and transient heat transfer from solid surfaces in He I and He II is important as a database for the analysis of the influence of local thermal disturbances on the stability of He I or He II cooled large superconducting magnets. In this paper, an overview of the transient heat transfer characteristics on solid surfaces in He I and He II caused by various large stepwise heat inputs, such as the quasi-steady nucleate boiling with a certain lifetime in He I and the quasi-steady Kapitza conductance heat flux with a certain lifetime in He II, are presented in comparison with their steady-state heat transfer characteristics. (author)
Nanoparticle enhanced ionic liquid heat transfer fluids
Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.
2014-08-12
A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.
Heat transfer analysis of short helical borehole heat exchangers
International Nuclear Information System (INIS)
Zarrella, Angelo; De Carli, Michele
2013-01-01
Highlights: ► Vertical ground heat exchanger with a helical shaped pipe is analyzed. ► The model considers the interaction between the ground and the environment. ► The results of the model are in good agreement with the experimental values. ► The weather conditions considerably affect the fluid heat carrier temperature. ► The pitch between the turns does not affect the behaviour of the heat exchanger. -- Abstract: In this paper a numerical model to analyze the thermal behaviour of vertical ground heat exchangers with a helical shaped pipe is presented. This type of configuration can be a suitable alternative to conventional ground heat exchangers, especially when the heating and cooling loads of the building are very low. The model describes the heat transfer problem by means of a network of interconnected thermal resistances and capacitances. Moreover, as the investigated ground heat exchanger is usually installed in shallow depth, the model takes into account the interaction between the ground and the ambient environment which affects the fluid heat carrier temperature into the heat exchanger and, as a consequence, the energy efficiency of the heat pump. After a sensitivity analysis on the mesh parameters, the presented model is compared with experimental data and the simulation results show good agreement with the measurements. Finally, analyses to investigate the influence of the weather conditions, of the axial heat transfer and of the pitch between the turns of the helical pipe for two types of ground are carried out.
Heat transfer enhancement on nucleate boiling
International Nuclear Information System (INIS)
Zhuang, M.; Guibai, L.
1990-01-01
This paper reports on enhancement of nucleate boiling heat transfer with additives that was investigated experimentally. More than fifteen kinds of additives were chosen and tested. Eight kinds of effective additives which can enhance nucleate boiling heat transfer were selected. Experimental results showed that boiling heat transfer coefficient of water was increased by 1 to 5 times and that of R-113 was increased by 1 to 4 times when trace amount additives were put in the two boiling liquids. There exist optimum concentrations for the additives, respectively, which can enhance nucleate boiling heat transfer rate best. In order to analyze the mechanism of the enhancement of boiling heat transfer with additives, the surface tension and the bubble departure diameter were measured. The nucleation sites were investigated by use of high-speed photograph. Experimental results showed that nucleation sites increase with additive amount increasing and get maximum. Increasing nucleation sites is one of the most important reason why nucleate boiling heat transfer can be enhanced with additives
Theory of Periodic Conjugate Heat Transfer
Zudin, Yuri B
2012-01-01
This book presents the theory of periodic conjugate heat transfer in a detailed way. The effects of thermophysical properties and geometry of a solid body on the commonly used and experimentally determined heat transfer coefficient are analytically presented from a general point of view. The main objective of the book is a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body. At the body surface, the true heat transfer coefficient is composed of two parts: the true mean value resulting from the solution of the steady state heat transfer problem and a periodically variable part, the periodic time and length to describe the oscillatory hydrodynamic effects. The second edition is extended by (i) the analysis of stability boundaries in helium flow at supercritical conditions in a heated channel with respect to the interaction between a solid body and a fluid; (ii) a periodic model and a method of heat transfer sim...
Nonlocal heat transfer in nanostructures
International Nuclear Information System (INIS)
Kanavin, A.P.; Uryupin, S.A.
2008-01-01
Kinetics of electrons in a degenerate conductor heated up by absorption of a high-frequency field localized in a region of about hundred nanometers has been studied. A new law for nonlocal electron thermal flux has been predicted
Theory of periodic conjugate heat transfer
Zudin, Yuri B
2016-01-01
This book presents the theory of periodic conjugate heat transfer in detail. It offers a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body.
Cornish heat transfer experiment - final report
International Nuclear Information System (INIS)
Bourke, P.J.; Hodgkinson, D.P.
1985-01-01
The transfer of heat released in an in-site heating experiment simulating high level radioactive waste packages in granite in Cornwall has been found to be mainly by conduction but some appreciable convection does occur. Interim analysis of the data suggests that the latter may account for about 20% of the total. (author)
Interactive Heat Transfer Simulations for Everyone
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,…
Industrial furnace with improved heat transfer
Energy Technology Data Exchange (ETDEWEB)
Hoetzl, M.; Lingle, T.M.
1993-07-20
A method is described for effecting improved heat transfer with in an industrial furnace having a cylindrical furnace section, a door at one end of the furnace section, an end plate at the opposite end of the section a circular fan plate concentrically positioned within the furnace section to define a cylindrical fan chamber between the plate and the end section with a fan there between and a heat treat chamber between the plate and the door, the fan plate defining a non-orificing annular space extending between the interior of the cylindrical furnace section and the outer edge of the plate, the plate having a centrally located under-pressure opening extending there through and a plurality of circumferentially spaced tubular heating elements extending through the annular space into the heat treating chamber, the method comprising the steps of: (a) heating the heating elements to a temperature which is hotter that the temperature of the work within the heat treating chamber; (b) rotating the fan at a speed sufficient to form a portion of the furnace atmosphere as a wind mass swirling about the fan chamber; (c) propagating the wind mass through the annular space into the heat treating chamber as a swirling wind mass in the form of an annulus, the wind mass impinging the heating elements to establish heat transfer contact therewith while the mass retains its annulus shape until contacting the door and without any significant movement of the wind mass into the center of the heat treating chamber; (d) drawing the wind mass through the under-pressure zone after the wind mass comes into heat transfer contact with the work in the heat treating chamber; and (e) thereafter heating the work by radiation from the beating elements at high furnace temperatures in excess of about 1,600 F.
Numerical study on boiling heat transfer enhancement in a microchannel heat exchanger
International Nuclear Information System (INIS)
Jeon, Jin Ho; Suh, Young Ho; Son, Gi Hun
2008-01-01
Flow boiling in a microchannel heat exchanger has received attention as an effective heat removal mechanism for high power-density microelectronics. Despite extensive experimental studied, the bubble dynamics coupled with boiling heat transfer in a microchannel heat exchanger is still not well understood due to the technological difficulties in obtaining detailed measurements of microscale two-phase flows. In this study, complete numerical simulations are performed to further clarify the dynamics of flow boiling in a microchannel heat exchanger. The level set method for tracking the liquid-vapor interface is modified to include the effects of phase change and contact angle and to treat an immersed solid surface. Based on the numerical results, the effects of modified channel shape on the bubble growth and heat transfer are quantified
Heat transfer enhancement in heat exchangers by longitudinal vortex generators
International Nuclear Information System (INIS)
Guntermann, T.; Fiebig, M.; Mitra, N.K.
1990-01-01
In this paper heat transfer enhancement and flow losses are computed for the interaction of a laminar channel flow with a pair of counterrotating longitudinal vortices generated by a pair of delta-winglets punched out of the channel wall. The geometry simulates an element of a fin-plate or fin-tube heat exchanger. The structure of the vortex flow and temperature distribution, the local heat transfer coefficients and the local flow losses are discussed for a sample case. For a Reynolds number of Re d = 1000 and a vortex generator angle of attack of β = 25 degrees heat transfer is enhanced locally by more than 300% and in the mean by 50%. These values increase further with Re and β
Heat transfer with freezing and thawing
Lunardini, VJ
1991-01-01
This volume provides a comprehensive overview on the vast amount of literature on solidification heat transfer. Chapter one develops important basic equations and discusses the validity of considering only conductive heat transfer, while ignoring convection, in the large class of materials which make up the porous media. Chapters 2 to 4 deal with problems that can be expressed in plane (Cartesian) coordinates. These problems are further divided into boundary conditions of temperature, prescribed heat flux, and surface convection. Chapter 5 examines some plane geometries involving three-dime
International Nuclear Information System (INIS)
Sircilli Neto, F.; Passaro, A.; Borges, E.M.
1991-01-01
The cooling systems of nuclear reactors for spacial applications include direct current electromagnetic pumps, which are used to circulate the coolant fluid thru the reactor core. In this work, the transfer of the heat generated by the electrical current in a magnet C excitation coils, which is used in a prototype pump, was evaluated. Considering the processes of heat transfer by conduction, natural convection and radiation, the results of simulation with the codes HEATING5 and AUTHEATS indicate the utilization of the 180 sup(0)C thermal class conductor for a working Joule power of 4 10 sup(4) W/m sup(3) in each magnet coil. (author)
Fem Formulation of Heat Transfer in Cylindrical Porous Medium
Azeem; Khaleed, H. M. T.; Soudagar, Manzoor Elahi M.
2017-08-01
Heat transfer in porous medium can be derived from the fundamental laws of flow in porous region ass given by Henry Darcy. The fluid flow and energy transport inside the porous medium can be described with the help of momentum and energy equations. The heat transfer in cylindrical porous medium differs from its counterpart in radial and axial coordinates. The present work is focused to discuss the finite element formulation of heat transfer in cylindrical porous medium. The basic partial differential equations are derived using Darcy law which is the converted into a set of algebraic equations with the help of finite element method. The resulting equations are solved by matrix method for two solution variables involved in the coupled equations.
Density based topology optimization of turbulent flow heat transfer systems
DEFF Research Database (Denmark)
Dilgen, Sümer Bartug; Dilgen, Cetin Batur; Fuhrman, David R.
2018-01-01
The focus of this article is on topology optimization of heat sinks with turbulent forced convection. The goal is to demonstrate the extendibility, and the scalability of a previously developed fluid solver to coupled multi-physics and large 3D problems. The gradients of the objective and the con...... in the optimization process, while also demonstrating extension of the methodology to include coupling of heat transfer with turbulent flows.......The focus of this article is on topology optimization of heat sinks with turbulent forced convection. The goal is to demonstrate the extendibility, and the scalability of a previously developed fluid solver to coupled multi-physics and large 3D problems. The gradients of the objective...
Capillary-Condenser-Pumped Heat-Transfer Loop
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.
Postaccident heat removal. II. Heat transfer from an internally heated liquid to a melting solid
International Nuclear Information System (INIS)
Faw, R.E.; Baker, L. Jr.
1976-01-01
Microwave heating has been used in studies of heat transfer from a horizontal layer of internally heated liquid to a melting solid. Experiments were designed to simulate heat transfer and meltthrough processes of importance in the analysis of postaccident heat removal capabilities of nuclear reactors. Glycerin, heated by 2.45-GHz microwave radiation, was used to simulate molten fuel. Paraffin wax was used to simulate a melting barrier confining the fuel. Experimentally measured heat fluxes and melting rates were consistent with a model based on downward heat transfer by conduction through a stagnant liquid layer and upward heat transfer augmented by natural convection. Melting and displacement of the barrier material occurred by upward-moving droplets randomly distributed across the melting surface. Results indicated that the melting and displacement process had no effect on the heat transfer process
Experimental study on transient boiling heat transfer
International Nuclear Information System (INIS)
Visentini, R.
2012-01-01
well. A flexible power supply that can generate a free-shape signal, allows to get to a wall-temperature increase rate up to 2500 K/s but also to obtain lower rates, which permits to study weaker transients and steady state conditions. The thermal measurements are realised by means of an infra-red camera and a high-speed camera is employed in order to see the boiling phenomena at the same time. From the voltage and current measurements the heat flux that is passed to the fluid is known. It is possible to underline some of the main results of this work. We found that, even when the boiling onset occurs soon because of the high power, transient conduction is always coupled with transient convection. The boiling onset occurs when the wall superheat is between 10 K et 30 K. This value corresponds to the activation of the smallest nucleation sites at the wall. The literature correlations well fit the nucleate boiling data in steady-state conditions. When the wall-temperature increase rate leads to transient boiling, the heat flux is higher than in steady state. This is consistent with what was found in previous studies. The nucleate boiling phase may last only a few milliseconds when the power is really high and the wall temperature increases really rapidly (500-2000 K/s). The experiments in transient boiling also point out that the heat flux is larger than in steady state conditions for the other regimes: Critical heat flux and also film boiling. The experimental set-up allows to investigate a large range of parameters (wall-temperature increase rate, flow rate, fluid temperature) by means of accurate temperature measurements and visualisations. Some modeling of the heat transfer are also proposed. (author)
Indirect evaporative coolers with enhanced heat transfer
Kozubal, Eric; Woods, Jason; Judkoff, Ron
2015-09-22
A separator plate assembly for use in an indirect evaporative cooler (IEC) with an air-to-air heat exchanger. The assembly includes a separator plate with a first surface defining a dry channel and a second surface defining a wet channel. The assembly includes heat transfer enhancements provided on the first surface for increasing heat transfer rates. The heat transfer enhancements may include slit fins with bodies extending outward from the first surface of separator plate or may take other forms including vortex generators, offset strip fins, and wavy fins. In slit fin implementations, the separator plate has holes proximate to each of the slit fins, and the separator plate assembly may include a sealing layer applied to the second surface of the separator plate to block air flow through the holes. The sealing layer can be a thickness of adhesive, and a layer of wicking material is applied to the adhesive.
Heat transfer in the atmosphere
Oerlemans, J.
1982-01-01
The atmosphere is almost transparent to solar radiation and almost opaque to terrestrial radiation. This implies that in the mean the atmosphere cools while the earth's surface is heated. Convection in the lower atmosphere must therefore occur. The upward flux of energy associated with it
Modeling microscale heat transfer using Calore.
Energy Technology Data Exchange (ETDEWEB)
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.
Heat transfer characteristics of a helical heat exchanger
International Nuclear Information System (INIS)
San, Jung-Yang; Hsu, Chih-Hsiang; Chen, Shih-Hao
2012-01-01
Heat transfer performance of a helical heat exchanger was investigated. The heat exchanger is composed of a helical tube with rectangular cross section and two cover plates. The ε–Ntu relation of the heat exchanger was obtained using a numerical method. In the analysis, the flow in the tube (helical flow) was considered to be mixed and the flow outside the tube (radial flow) was unmixed. In the experiment, the Darcy friction factor (f) and convective heat transfer coefficient (h) of the radial flow were measured. The radial flow was air and the helical flow was water. Four different channel spacing (0.5, 0.8, 1.2 and 1.6 mm) were individually considered. The Reynolds numbers were in the range 307–2547. Two correlations, one for the Darcy friction factor and the other for the Nusselt number, were proposed. - Highlights: ► We analyze the heat transfer characteristics of a helical heat exchanger and examine the effectiveness–Ntu relation. ► Increasing number of turns of the heat exchanger would slightly increase the effectiveness. ► There is an optimum Ntu value corresponding to a maximum effectiveness. ► We measure the Darcy friction factor and Nusselt number of the radial flow and examine the correlations.
Lunar ash flow with heat transfer.
Pai, S. I.; Hsieh, T.; O'Keefe, J. A.
1972-01-01
The most important heat-transfer process in the ash flow under consideration is heat convection. Besides the four important nondimensional parameters of isothermal ash flow (Pai et al., 1972), we have three additional important nondimensional parameters: the ratio of the specific heat of the gas, the ratio of the specific heat of the solid particles to that of gas, and the Prandtl number. We reexamine the one dimensional steady ash flow discussed by Pai et al. (1972) by including the effects of heat transfer. Numerical results for the pressure, temperature, density of the gas, velocities of gas and solid particles, and volume fraction of solid particles as function of altitude for various values of the Jeffreys number, initial velocity ratio, and two different gas species (steam and hydrogen) are presented.
Transfer coefficients in ultracold strongly coupled plasma
Bobrov, A. A.; Vorob'ev, V. S.; Zelener, B. V.
2018-03-01
We use both analytical and molecular dynamic methods for electron transfer coefficients in an ultracold plasma when its temperature is small and the coupling parameter characterizing the interaction of electrons and ions exceeds unity. For these conditions, we use the approach of nearest neighbor to determine the average electron (ion) diffusion coefficient and to calculate other electron transfer coefficients (viscosity and electrical and thermal conductivities). Molecular dynamics simulations produce electronic and ionic diffusion coefficients, confirming the reliability of these results. The results compare favorably with experimental and numerical data from earlier studies.
Heat transfer from thermal effluent
International Nuclear Information System (INIS)
Czapski, U.H.; Mumford, W.
1975-01-01
Measurements of the turbulent fluxes of sensible heat and momentum, together with profiles of horizontal wind, temperature, and humidity (wet bulb) have been conducted above the thermal plume of the Nine Mile Point Nuclear plant near Oswego, New York on Lake Ontario. The spectral analysis of the data, obtained with sonic anemometer and ultrafast thermocouples, reveals the importance of microthermals and similar features for the transport of heat. Temperature variance spectra and the cospectra wT and uw show distinct deviations from the -5/3 Kolmogorov law in the inertial subrange, suggesting a high input of energy in the eddy frequency range between 0.01 and 1 Hz. It is shown that microthermals in this frequency range are also responsible for a large portion of the momentum transport. 46 refs
Heat Transfer Model for Hot Air Balloons
Lladó Gambín, Adriana
2016-01-01
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 mod...
Evaluation of heat transfer enhancement in air-heating collectors
Energy Technology Data Exchange (ETDEWEB)
Mattox, D. L.
1979-06-01
The present research effort was initiated for the purpose of increasing the thermal efficiency of air heating solar collectors through identification and development of optimum design and operation criteria for solar absorber-to-air heat exchangers. Initially this effort took the form of a solar collector systems analysis to evaluate the impact of various techniques for enhancing the heat transfer between the absorber and air stream on overall thermal performance of the entire solar collector. This systems analysis resulted in the selection of solar collector designs providing ducted cooling air on the absorber shaded side as a base line. A transient heat transfer analysis of a complete solar air heating collector was used to demonstrate that an optimum absorber-to-air heat exchanger design could be provided with several interrupted fin configurations. Additional analyses were performed to establish that the maximum solar collector thermal performance to required pumping power was realized for a Reynolds number range of 1000 to 2000. This Reynolds number range was used to establish a theoretical design limit curve for maximum thermal performance versus required pumping power for all interrupted fin designs as published in the open literature. Heat and momentum transfer empirical relationships were defined for scaling the state-of-the-art high conductance fin designs identified from a compact configuration to the less compact designs needed for solar collectors.
Energy Technology Data Exchange (ETDEWEB)
Dyrboel, Susanne
1998-05-01
Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the
Heat transfer 1990. Proceedings of the ninth international heat transfer conference
International Nuclear Information System (INIS)
Hetsroni, G.
1990-01-01
This book contains the proceedings of the Ninth International Heat Transfer Conference. Included in Volume 3 are the following chapters: Refrigerant vapor condensation on a horizontal tube bundle. Local heat transfer in a reflux condensation inside a closed two-phase thermosyphon and surface temperature by means of a pulsed photothermal effects
Chen, H.; Hu, C.; Chen, G.; Zhang, Q.
2017-12-01
Geothermal heat is a viable source of energy and its environmental impact in terms of CO2 emissions is significantly lower than conventional fossil fuels. it is vital that engineers acquire a proper understanding about the Ground Source Heat Pump (GSHP). In this study, the model of the borehole exchanger under conduction manners and heat infiltrates coupling manners was established with FEFLOW. The energy efficiency, heat transfer endurance and heat transfer in the unit depth were introduced to quantify the energy efficient and the endurance period. The performance of a the Borehole Exchanger (BHE) in soil with and without groundwater seepage was analyzed of heat transfer process between the soil and the working fluid. Basing on the model, the varied regularity of energy efficiency performance an heat transfer endurance with the conditions including the different configuration of the BHE, the soil properties, thermal load characteristic were discussed. Focus on the heat transfer process in multi-layer soil which one layer exist groundwater flow. And an investigation about thermal dispersivity was also analyzed its influence on heat transfer performance. The final result proves that the model of heat infiltrates coupling model established in this context is reasonable, which can be applied to engineering design.
Heat transfer pipe shielding device for heat exchanger
International Nuclear Information System (INIS)
Hanawa, Jun.
1991-01-01
The front face and the rear face of a frame that surrounds the circumference of the water chamber body of a multi-tube heat exchanger are covered by a rotational shielding plate. A slit is radially formed to the shielding plate for the insertion of a probe or cleaner to the heat transfer pipe and a deflector is disposed on the side opposite to the slit. The end of the heat transfer pipe to be inspected is exposed to the outer side by way of the slit by the rotation of the shielding plate, and the probe or cleaner is inserted in the heat transfer pipe to conduct an eddy current injury monitoring test or cleaning. The inside of the water chamber and the heat transfer pipe is exhausted by a ventilation nozzle disposed to the frame. Accordingly, a shielding effect upon inspection and cleaning can be obtained and, in addition, inspection and exhaustion at the cleaning position can be conducted easily. Since the operation for attachment and detachment is easy, the effect of reducing radiation dose per unit can be obtained by the shortening of the operation time. (N.H.)
Heat transfer with a split water channel
International Nuclear Information System (INIS)
Krinsky, S.
1978-01-01
The heat transfer problem associated with the incidence of synchrotron radiation upon a vacuum chamber wall cooled by a single water channel was previously studied, and a numerical solution to the potential problem was found using the two-dimensional magnet program POISSON. Calculations were extended to consider the case of a split water channel using POISSON to solve the potential problem for a given choice of parameters. By optimizing the dimensions, boiling of the water can be avoided. A copper chamber is a viable solution to the heat transfer problem at a beam port
Natural Convective Heat Transfer from Narrow Plates
Oosthuizen, Patrick H
2013-01-01
Natural Convective Heat Transfer from Narrow Plates deals with a heat transfer situation that is of significant practical importance but which is not adequately dealt with in any existing textbooks or in any widely available review papers. The aim of the book is to introduce the reader to recent studies of natural convection from narrow plates including the effects of plate edge conditions, plate inclination, thermal conditions at the plate surface and interaction of the flows over adjacent plates. Both numerical and experimental studies are discussed and correlation equations based on the results of these studies are reviewed.
Heat transfer applications for the practicing engineer
Theodore, Louis
2011-01-01
This book serves as a training tool for individuals in industry and academia involved with heat transfer applications. Although the literature is inundated with texts emphasizing theory and theoretical derivations, the goal of this book is to present the subject of heat transfer from a strictly pragmatic point of view. The book is divided into four Parts: Introduction, Principles, Equipment Design Procedures and Applications, and ABET-related Topics. The first Part provides a series of chapters concerned with introductory topics that are required when solving most engineering problems, inclu
Heat transfer phenomena revelant to severe accidents
International Nuclear Information System (INIS)
Dallman, R.J.; Duffey, R.B.
1990-01-01
A number of aspects of severe accidents have been reviewed, particularly in relation to the heat transfer characteristics and the important phenomena. It is shown that natural circulation, forced convection, and entrainment phenomena are important for both the reactor system and ex-vessel events. It is also shown that the phenomena related to two component enhanced heat transfer is important in the pool of molten core debris, in relation to the potential for attack of the liner structure and the concrete. These mechanisms are discussed within the general context of severe accident progression
Heat transfer phenomena relevant to severe accidents
International Nuclear Information System (INIS)
Dallman, R.J.; Duffey, R.B.
1990-01-01
A number of aspects of severe accidents have been reviewed, particularly in relation to the heat transfer characteristics and the important phenomena. It is shown that natural circulation, forced convection, and entrainment phenomena are important for both the reactor system and ex-vessel events. It is also shown that the phenomena related to two component enhanced heat transfer is important in the pool of molten core debris, in relation to the potential for attack of the liner structure and the concrete. These mechanisms are discussed within the general context of severe accident progression. 26 refs
Heat transfer for plasma facing components
International Nuclear Information System (INIS)
Boyd, R.D.; Meng, X.; Maughan, H.
1995-01-01
Although the high heat flux requirements for plasma-facing components have been reduced drastically from 40.0 MW/m 2 to near 10.0 MW/m 2 , there are still some refinements needed. This paper highlights: (1) recent accomplishments and pinpoints new thermal solutions and problem areas of immediate concern to the development of plasma-facing components, and (2) next generation thermal hydraulic problems which must be addressed to insure safety and reliability in component operation. More specifically the near-term thermal hydraulic problems entail: (1) generating an appropriate data base to insure the development of single-side heat flux correlations; and (2) adapting the existing vast uniform heat flux literature to the case of non-uniform heat flux distributions found in plasma facing components in fusion reactors. Results are presented for the latter task which includes: (a) an accurate subcooled flow boiling curve correlation for the partial nucleate boiling regime which can be adapted using previously proposed correlations relating single-side boundary heat flux to heat transfer, in uniformly heated channels, (b) the evaluation of the possibility of using the existing literature directly with redefined parameters, and (c) an estimation of circumferential variations in the heat transfer coefficient
Microscale surface modifications for heat transfer enhancement.
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.
Turbulent Heat Transfer in Curved Pipe Flow
Kang, Changwoo; Yang, Kyung-Soo
2013-11-01
In the present investigation, turbulent heat transfer in fully-developed curved pipe flow with axially uniform wall heat flux has been numerically studied. The Reynolds numbers under consideration are Reτ = 210 (DNS) and 1,000 (LES) based on the mean friction velocity and the pipe radius, and the Prandtl number (Pr) is 0.71. For Reτ = 210 , the pipe curvature (κ) was fixed as 1/18.2, whereas three cases of κ (0.01, 0.05, 0.1) were computed in the case of Reτ = 1,000. The mean velocity, turbulent intensities and heat transfer rates obtained from the present calculations are in good agreement with the previous numerical and experimental results. To elucidate the secondary flow structures due to the pipe curvature, the mean quantities and rms fluctuations of the flow and temperature fields are presented on the pipe cross-sections, and compared with those of the straight pipe flow. To study turbulence structures and their influence on turbulent heat transfer, turbulence statistics including but not limited to skewness and flatness of velocity fluctuations, cross-correlation coefficients, an Octant analysis, and turbulence budgets are presented and discussed. Based on our results, we attempt to clarify the effects of Reynolds number and the pipe curvature on turbulent heat transfer. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0008457).
Natural convective heat transfer from square cylinder
Energy Technology Data Exchange (ETDEWEB)
Novomestský, Marcel, E-mail: marcel.novomestsky@fstroj.uniza.sk; Smatanová, Helena, E-mail: helena.smatanova@fstroj.uniza.sk; Kapjor, Andrej, E-mail: andrej.kapjor@fstroj.uniza.sk [University of Žilina, Faculty of Mechanical Engineering, Department of Power Engineering, Univerzitná 1, 010 26 Žilina (Slovakia)
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.
Heat Transfer in Directional Water Transport Fabrics
Directory of Open Access Journals (Sweden)
Chao Zeng
2016-10-01
Full Text Available Directional water transport fabrics can proactively transfer moisture from the body. They show great potential in making sportswear and summer clothing. While moisture transfer has been previously reported, heat transfer in directional water transport fabrics has been little reported in research literature. In this study, a directional water transport fabric was prepared using an electrospraying technique and its heat transfer properties under dry and wet states were evaluated, and compared with untreated control fabric and the one pre-treated with NaOH. All the fabric samples showed similar heat transfer features in the dry state, and the equilibrium temperature in the dry state was higher than for the wet state. Wetting considerably enhanced the thermal conductivity of the fabrics. Our studies indicate that directional water transport treatment assists in moving water toward one side of the fabric, but has little effect on thermal transfer performance. This study may be useful for development of “smart” textiles for various applications.
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-01-01
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758
Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer
Directory of Open Access Journals (Sweden)
Giovanni Maria Carlomagno
2014-11-01
Full Text Available 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.
Heat transfer corrected isothermal model for devolatilization of thermally-thick biomass particles
DEFF Research Database (Denmark)
Luo, Hao; Wu, Hao; Lin, Weigang
Isothermal model used in current computational fluid dynamic (CFD) model neglect the internal heat transfer during biomass devolatilization. This assumption is not reasonable for thermally-thick particles. To solve this issue, a heat transfer corrected isothermal model is introduced. In this model......, two heat transfer corrected coefficients: HT-correction of heat transfer and HR-correction of reaction, are defined to cover the effects of internal heat transfer. A series of single biomass devitalization case have been modeled to validate this model, the results show that devolatilization behaviors...... of both thermally-thick and thermally-thin particles are predicted reasonable by using heat transfer corrected model, while, isothermal model overestimate devolatilization rate and heating rate for thermlly-thick particle.This model probably has better performance than isothermal model when it is coupled...
Conjugate heat transfer simulations of advanced research reactor fuel
Energy Technology Data Exchange (ETDEWEB)
Piro, M.H.A., E-mail: pirom@aecl.ca; Leitch, B.W.
2014-07-01
Highlights: • Temperature predictions are enhanced by coupling heat transfer in solid and fluid zones. • Seven different cases are considered to observe trends in predicted temperature and pressure. • The seven cases consider high/medium/low power, flow, burnup, fuel material and geometry. • Simulations provide temperature predictions for performance/safety. Boiling is unlikely. • Simulations demonstrate that a candidate geometry can enhance performance/safety. - Abstract: The current work presents numerical simulations of coupled fluid flow and heat transfer of advanced U–Mo/Al and U–Mo/Mg research reactor fuels in support of performance and safety analyses. The objective of this study is to enhance predictions of the flow regime and fuel temperatures through high fidelity simulations that better capture various heat transfer pathways and with a more realistic geometric representation of the fuel assembly in comparison to previous efforts. Specifically, thermal conduction, convection and radiation mechanisms are conjugated between the solid and fluid regions. Also, a complete fuel element assembly is represented in three dimensional space, permitting fluid flow and heat transfer to be simulated across the entire domain. Seven case studies are examined that vary the coolant inlet conditions, specific power, and burnup to investigate the predicted changes in the pressure drop in the coolant and the fuel, clad and coolant temperatures. In addition, an alternate fuel geometry is considered with helical fins (replacing straight fins in the existing design) to investigate the relative changes in predicted fluid and solid temperatures. Numerical simulations predict that the clad temperature is sensitive to changes in the thermal boundary layer in the coolant, particularly in simultaneously developing flow regions, while the temperature in the fuel is anticipated to be unaffected. Finally, heat transfer between fluid and solid regions is enhanced with
The log mean heat transfer rate method of heat exchanger considering the influence of heat radiation
International Nuclear Information System (INIS)
Wong, K.-L.; Ke, M.-T.; Ku, S.-S.
2009-01-01
The log mean temperature difference (LMTD) method is conventionally used to calculate the total heat transfer rate of heat exchangers. Because the heat radiation equation contains the 4th order exponential of temperature which is very complicate in calculations, thus LMTD method neglects the influence of heat radiation. From the recent investigation of a circular duct in some practical situations, it is found that even in the situation of the temperature difference between outer duct surface and surrounding is low to 1 deg. C, the heat radiation effect can not be ignored in the situations of lower ambient convective heat coefficient and greater surface emissivities. In this investigation, the log mean heat transfer rate (LMHTR) method which considering the influence of heat radiation, is developed to calculate the total heat transfer rate of heat exchangers.
Numerical simulation of heat transfer process in automotive brakes
Gonzalo Voltas, David
2013-01-01
This master thesis concerns the theoretical investigations of the heat transfer process in automotive brakes. The process of heat generation and heat transfer to ambient air in automotive brake was presented. The two–dimensional, axi-symmetrical model of transient heat conduction for the brake was applied. The relevant boundary conditions, that describe the heat generated in the brake and the heat transferred to ambient air, were used. The unsteady heat conduction problem was solved by the...
Heat transfer in two-phase flow of helium
International Nuclear Information System (INIS)
Subbotin, V.I.; Deev, V.I.; Solodovnikov, V.V.; Arkhipov, V.V.
1986-01-01
The results of experimental study of heat transfer in two-phase helium flow are presented. The effect of operating parameters (pressure, mass velocity, heat flux and quality) on boiling heat transfer intensity was investigated. A significant influence of boiling process prehistory on heat transfer coefficients was demonstrated. On the basis of experimental data obtained three typical regimes of flow boiling heat transfer were found. Analogy of heat transfer in flow boiling and pool boiling of helium and noncryogenic liquids was established. Correlations were developed which are in close agreement with available heat transfer data
Directory of Open Access Journals (Sweden)
Milan Đorđević
2017-12-01
Full Text Available The Archimedean spiral coil made of a transversely corrugated tube was exposed to radiant heating in order to represent a heat absorber of the parabolic dish solar concentrator. The main advantage of the considered innovative design solution is a coupling effect of the two passive methods for heat transfer enhancement - coiling of the flow channel and changes in surface roughness. The curvature ratio of the spiral coil varies from 0.029 to 0.234, while water and a mixture of propylene glycol and water are used as heat transfer fluids. The unique focus of this study is on specific boundary conditions since the heat flux upon the tube external surfaces varies not only in the circumferential direction, but in the axial direction as well. Instrumentation of the laboratory model of the heat absorber mounted in the radiation field includes measurement of inlet fluid flow rate, pressure drop, inlet and outlet fluid temperature and 35 type K thermocouples welded to the coil surface. A thermal analysis of the experimentally obtained data implies taking into consideration the externally applied radiation field, convective and radiative heat losses, conduction through the tube wall and convection to the internal fluid. The experimental results have shown significant enhancement of the heat transfer rate compared to spirally coiled smooth tubes, up to 240% in the turbulent flow regime.
Ribeiro, Carla
2017-01-01
The double-wall paper cup is an everyday object that can be used in the laboratory to study heat transfer. The experiment described here has been done by physics students aged 12-13 years; it can also be used in a different context to prompt debate about environmental issues.
Free convection film flows and heat transfer
Shang, Deyi
2010-01-01
Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.
Conjugate problems in convective heat transfer
Dorfman, Abram S
2009-01-01
The conjugate heat transfer (CHT) problem takes into account the thermal interaction between a body and fluid flowing over or through it, a key consideration in both mechanical and aerospace engineering. Presenting more than 100 solutions of non-isothermal and CHT problems, this title considers the approximate solutions of CHT problems.
CENTRIFUGAL COMPRESSOR EFFICIENCY CALCULATION WITH HEAT TRANSFER
Directory of Open Access Journals (Sweden)
Valeriu Dragan
2017-12-01
and manner under which the efficiency itself is calculated. The paper presents a more robust approach to measuring efficiency, regardless of the heat transfer within the turbomachinery itself. Possible applications of the study may range from cold-start regime simulation to the optimization of inter-cooling setup or even flow angle control without mechanically actuated OGV
Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor
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.
Quantum heat engine with coupled superconducting resonators
DEFF Research Database (Denmark)
Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.
2017-01-01
We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....
Numerical Modeling of Ablation Heat Transfer
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.
On the thermoeconomics of heat transfer
International Nuclear Information System (INIS)
El-Sayed, Y.M.
1991-01-01
The cost effectiveness of improving the thermodynamics of heat transfer in an energy system is investigated by considering steam power systems bottoming a given gas turbine. Higher efficiencies are basically achieved by improving the temperature match of the heat addition process using both structural and parametric modes of change. The heat transfer surfaces, when expressed solely in terms of efficiency, indicate the existence of an envelope bounding them. The envelope can be approximated by a simple continuous function. Minimum surface for a given efficiency is on or closest to the envelope. Similar features apply to capital cost and to the cost objective function. In this paper the generalization and the limitations of the envelopment concept are discussed as well as the relevance to artificial intelligence
Transfers among divorced couples: evidence and interpretation.
Weiss, Y; Willis, R J
1993-10-01
An analysis of the economic impact of divorce settlements in the United States is presented using data for a white cohort taken from the National Longitudinal Study of the High School Class of 1972. "The effects of spouses' incomes on the divorce transfer are estimated and used to simulate the welfare effects of divorce on husbands, wives, and children under alternative assumptions about marriage contracts and the ability of a couple to continue coordinating resources in the aftermath of divorce. We find a positive (negative) relationship between divorce transfers and the growth of husband's (wife's) earnings during marriage. The estimated expenditure on children in the divorce state is only half the accustomed level during marriage." excerpt
Quantum state transfer with untunable couplings
International Nuclear Information System (INIS)
Gagnebin, P. K.; Skinner, S. R.; Behrman, E. C.; Steck, J. E.
2007-01-01
We present a general scheme for implementing bidirectional quantum state transfer in a quantum swapping channel. Unlike many other schemes for quantum computation and communication, our method does not require qubit couplings to be switched on and off. The only control variable is the bias acting on individual qubits. We show how to derive the parameters of the system (fixed and variable) such that perfect state transfer can be achieved. Since these parameters vary linearly with the pulse width, our scheme allows flexibility in the time scales under which qubits evolve. Unlike quantum spin networks, our scheme allows the transmission of several quantum states at a time, requiring only a two qubit separation between quantum states. By pulsing the biases of several qubits at the same time, we show that only eight bias control lines are required to achieve state transfer along a channel of arbitrary length. Furthermore, when the information to be transferred is purely classical in nature, only three bias control lines are required, greatly simplifying the circuit complexity
Problems of power-heat-coupling in industry
Energy Technology Data Exchange (ETDEWEB)
1977-03-01
The coupled heat and electric power supply from counter-pressure and partly also from extraction-condensing plants theoretically offers the best possibilities for saving energy in comparison to other measures which reduce the primary energy employed at equal useful energy. A basic requirement for the use of this principle of power-heat coupling is a somewhat simultaneous need of heat and electrical energy as well as a relatively short distance between production point and consumption point, since the transfer ability of the heat is limited due to the considerable cost of the transportation system. Numerous industrial enterprises offer favorable conditions for the use of power-heat coupling. Because of the existing legal and contract rights restraints, the incentive for a free development of industrial power-heat coupling with the aim of saving energy is strongly weakened. Therefore a new order to road rights is nececessary, which would make possible the construction and operation of common plants for several industrial operations and which would insure the right to lay industrial energy lines in public roads where reasonably possible. It has been proven necessary to make it the duty of the cartel authorities to orient their examinations of price regulations for auxiliary and reserve electric power supply solely on the objective electricity economy facts, but not on so-called advantageous points of view. Ultimately the regulation for common use of the utilities own piping system for the purpose of saving and piping free energy and free power from its own plants can be reasonably necessary in the utilities realm, if free agreements between the utility and the industry are not enough in this question.
Numerical study of heat transfer characteristics in BOG heat exchanger
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.
Visualisation of heat transfer in unsteady laminar flows
Speetjens, M.F.M.; Steenhoven, van A.A.
2011-01-01
Heat transfer in fluid flows traditionally is examined in terms of temperature fields and heat-transfer coefficients. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the transport of fluid by
Heat transfer coefficient as parameter describing ability of insulating liquid to heat transfer
Nadolny, Zbigniew; Gościński, Przemysław; Bródka, Bolesław
2017-10-01
The paper presents the results of the measurements of heat transfer coefficient of insulating liquids used in transformers. The coefficient describes an ability of the liquid to heat transport. On the basis of the coefficient, effectiveness of cooling system of electric power devices can be estimated. Following liquids were used for the measurements: mineral oil, synthetic ester and natural ester. It was assumed that surface heat load is about 2500 W·m-2, which is equal the load of transformer windings. A height of heat element was 1.6 m, because it makes possible steady distribution of temperature on its surface. The measurements of heat transfer coefficient was made as a function of various position of heat element (vertical, horizontal). In frame of horizontal position of heat element, three suppositions were analysed: top, bottom, and side.
Heat transfer coefficient as parameter describing ability of insulating liquid to heat transfer
Directory of Open Access Journals (Sweden)
Nadolny Zbigniew
2017-01-01
Full Text Available The paper presents the results of the measurements of heat transfer coefficient of insulating liquids used in transformers. The coefficient describes an ability of the liquid to heat transport. On the basis of the coefficient, effectiveness of cooling system of electric power devices can be estimated. Following liquids were used for the measurements: mineral oil, synthetic ester and natural ester. It was assumed that surface heat load is about 2500 W·m-2, which is equal the load of transformer windings. A height of heat element was 1.6 m, because it makes possible steady distribution of temperature on its surface. The measurements of heat transfer coefficient was made as a function of various position of heat element (vertical, horizontal. In frame of horizontal position of heat element, three suppositions were analysed: top, bottom, and side.
Experimental study on convective heat transfer with thin porous bodies
International Nuclear Information System (INIS)
Nishi, Yoshihisa; Kinoshita, Izumi; Furuya, Masahiro
2001-01-01
Experimental studies are made on the convective heat transfer of three types of thin porous bodies. Heat transfer performances, flow patterns and temperature profiles near the porous bodies are compared with each other. The heat transfer performance of porous bodies with the largest pore diameter is large. It became clear that the high heat transfer performance depends on an excellent heat transportation ability inside the pore and near the surface of the porous bodies. (author)
Topology optimization for transient heat transfer problems
DEFF Research Database (Denmark)
Zeidan, Said; Sigmund, Ole; Lazarov, Boyan Stefanov
The focus of this work is on passive control of transient heat transfer problems using the topology optimization (TopOpt) method [1]. The goal is to find distributions of a limited amount of phase change material (PCM), within a given design domain, which optimizes the heat energy storage [2]. Our......, TopOpt has later been extended to transient problems in mechanics and photonics (e.g. [5], [6] and [7]). In the presented approach, the optimization is gradient-based, where in each iteration the non-steady heat conduction equation is solved,using the finite element method and an appropriate time......-stepping scheme. A PCM can efficiently absorb heat while keeping its temperature nearly unchanged [8]. The use of PCM ine.g. electronics [9] and mechanics [10], yields improved performance and lower costs depending on a.o., the spatial distribution of PCM.The considered problem consists in optimizing...
Heat Transfer in Health and Healing.
Diller, Kenneth R
2015-10-01
Our bodies depend on an exquisitely sensitive and refined temperature control system to maintain a state of health and homeostasis. The exceptionally broad range of physical activities that humans engage in and the diverse array of environmental conditions we face require remarkable strategies and mechanisms for regulating internal and external heat transfer processes. On the occasions for which the body suffers trauma, therapeutic temperature modulation is often the approach of choice for reversing injury and inflammation and launching a cascade of healing. The focus of human thermoregulation is maintenance of the body core temperature within a tight range of values, even as internal rates of energy generation may vary over an order of magnitude, environmental convection, and radiation heat loads may undergo large changes in the absence of any significant personal control, surface insulation may be added or removed, all occurring while the body's internal thermostat follows a diurnal circadian cycle that may be altered by illness and anesthetic agents. An advanced level of understanding of the complex physiological function and control of the human body may be combined with skill in heat transfer analysis and design to develop life-saving and injury-healing medical devices. This paper will describe some of the challenges and conquests the author has experienced related to the practice of heat transfer for maintenance of health and enhancement of healing processes.
Wireless Energy Transfer Through Magnetic Reluctance Coupling
International Nuclear Information System (INIS)
Pillatsch, P
2014-01-01
Energy harvesting from human motion for body worn or implanted devices faces the problem of the wearer being still, e.g. while asleep. Especially for medical devices this can become an issue if a patient is bed-bound for prolonged periods of time and the internal battery of a harvesting system is not recharged. This article introduces a mechanism for wireless energy transfer based on a previously presented energy harvesting device. The internal rotor of the energy harvester is made of mild steel and can be actuated through a magnetic reluctance coupling to an external motor. The internal piezoelectric transducer is consequently actuated and generates electricity. This paper successfully demonstrates energy transfer over a distance of 16 mm in air and an achieved power output of 85 μW at 25 Hz. The device functional volume is 1.85 cm 3 . Furthermore, it was demonstrated that increasing the driving frequency beyond 25 Hz did not yield a further increase in power output. Future research will focus on improving the reluctance coupling, e.g. by investigating the use of multiple or stronger magnets, in order to increase transmission distance
Heat transfer with geometric shape of micro-fin tubes (I) - Condensing heat transfer
Energy Technology Data Exchange (ETDEWEB)
Kwak, K M; Chang, J S; Bai, C H; Chung, M [Yeungnam University, Kyungsan (Korea)
1999-11-01
To examine the enhancement mechanism of condensing heat transfer through microfin tube, the condensation experiments with refrigerant HCFC 22 are performed using 4 and 6 kinds of microfin tubes with outer diameter of 9.52 mm and 7.0 mm, respectively. Used microfin tubes have different shape and number of fins with each other. The main heat transfer enhancement mechanism is known to be the enlargement of heat transfer area and turbulence promotion. Together with these main factors, we can find other enhancement factors by the experimental data, which are the overflow of the refrigerant over the microfin and microfin arrangement. The overflow of the refrigerant over the microfin can be analyzed by the geometric shape of the microfin. microfin tubes having a shape which can give much overflow over the microfin show large condensing heat transfer coefficients. The effect of microfin arrangement is related to the heat transfer resistance of liquid film of refrigerant. The condensing heat transfer coefficients are high for the microfin tube with even distribution of liquid film. 17 refs., 14 figs., 3 tabs.
Film boiling heat transfer in liquid helium
International Nuclear Information System (INIS)
Inai, Nobuhiko
1979-01-01
The experimental data on the film boiling heat transfer in liquid helium are required for investigating the stability of superconducting wires. On the other hand, liquid helium has the extremely different physical properties as compared with the liquids at normal temperature such as water. In this study, the experiments on pool boiling were carried out, using the horizontal top surface of a 20 mm diameter copper cylinder in liquid helium. For observing individual bubbles, the experiments on film boiling from a horizontal platinum wire were performed separately in liquid nitrogen and liquid helium, and photographs of floating-away bubbles were taken. The author pointed out the considerable upward shift of the boiling curve near the least heat flux point in film boiling from the one given by the Berenson's equation which has been said to agree comparatively well with the data on the film boiling of the liquids at normal temperature, and the reason was investigated. Consequently, a model for film boiling heat transfer was presented. Also one equation expressing the film boiling at low heat flux for low temperature liquids was proposed. It represents well the tendency to shift from Berenson's equation of the experimental data on film boiling at the least heat flux point for liquid helium, liquid nitrogen and water having extremely different physical properties. Some discussions are added at the end of the paper. (Wakatsuki, Y.)
Foundation heat transfer analysis for buildings with thermal piles
International Nuclear Information System (INIS)
Almanza Huerta, Luis Enrique; Krarti, Moncef
2015-01-01
Highlights: • A numerical transient thermal model for thermo-active foundations is developed. • Thermal interactions between thermal piles and building foundations are evaluated. • A simplified analysis method of thermal interactions between thermal piles and building foundations is developed. - Abstract: Thermal piles or thermo-active foundations utilize heat exchangers embedded within foundation footings to heat and/or cool buildings. In this paper, the impact of thermal piles on building foundation heat transfer is investigated. In particular, a simplified analysis method is developed to estimate the annual ground-coupled foundation heat transfer when buildings are equipped with thermal piles. First, a numerical analysis of the thermal performance of thermo-active building foundations is developed and used to assess the interactions between thermal piles and slab-on-grade building foundations. The impact of various design parameters and operating conditions is evaluated including foundation pile depth, building slab width, foundation insulation configuration, and soil thermal properties. Based on the results of a series of parametric analyses, a simplified analysis method is presented to assess the impact of the thermal piles on the annual heat fluxes toward or from the building foundations. A comparative evaluation of the predictions of the simplified analysis method and those obtained from the detailed numerical analysis indicated good agreement with prediction accuracy lower than 5%. Moreover, it is found that thermal piles can affect annual building foundation heat loss/gain by up to 30% depending on foundation size and insulation level
Heat and mass transfer from the mantle: heat flow and He-isotope constraints
Directory of Open Access Journals (Sweden)
B. G. Polyak
2005-06-01
Full Text Available Terrestrial heat flow density, q, is inversely correlated with the age, t, of tectono-magmatic activity in the Earth's crust (Polyak and Smirnov, 1966; etc.. «Heat flow-age dependence» indicates unknown temporal heat sources in the interior considered a priori as the mantle-derived diapirs. The validity of this hypothesis is demonstrated by studying the helium isotope ratio, 3He/4He = R, in subsurface fluids. This study discovered the positive correlation between the regionally averaged (background estimations of R- and q-values (Polyak et al., 1979a. Such a correlation manifests itself in both pan-regional scales (Norhtern Eurasia and separate regions, e.g., Japan (Sano et al., 1982, Eger Graben (Polyak et al., 1985 Eastern China rifts (Du, 1992, Southern Italy (Italiano et al., 2000, and elsewhere. The R-q relation indicates a coupled heat and mass transfer from the mantle into the crust. From considerations of heat-mass budget this transfer can be provided by the flux consisting of silicate matter rather than He or other volatiles. This conclusion is confirmed by the correlation between 3He/ 4He and 87Sr/86Sr ratios in the products of the volcanic and hydrothermal activity in Italy (Polyak et al., 1979b; Parello et al., 2000 and other places. Migration of any substance through geotemperature field transports thermal energy accumulated within this substance, i.e. represents heat and mass transfer. Therefore, only the coupled analysis of both material and energy aspects of this transfer makes it possible to characterise the process adequately and to decipher an origin of terrestrial heat flow observed in upper parts of the earth crust. An attempt of such kind is made in this paper.
Simulation of coupled electromagnetic and heat dissipation problems
Janssen, H.H.J.M.; Maten, ter E.J.W.; Houwelingen, van D.
1994-01-01
A description is given of an integrated simulation environment for the solution of coupled electromagnetic and heat dissipation problems in two dimensions, in particular for the field of induction heating, dielectric heating, and hysteresis heating. The equations are coupled because the most
Heat transfer studies in waste repository design
International Nuclear Information System (INIS)
Boehm, R.F.; Chen, Y.T.; Izzeldin, A.; Kuharic, W.; Sudan, N.
1994-01-01
The main task of this project is the development of visualization methods in heat transfer through porous media. Experiments have been performed related to the determination of the wavelength that gives equality of the refractive indices of the porous material and the liquid. The work has been accomplished using the calibration setup consisting of a 2-in. long test cell filled with 2-mm diameter soda-lime glass beads. A supplemental task is an unsaturated flow experiment with heat transfer in porous media. For this work the medium of interest in quartz beads. Essentially two-dimensional flows of admitted water are able to be examined. During this quarter, the setup and calibration of the experimental instrumentation was done. Also the modification of the main experimental tank and the inflow system was carried out. Initial testing was done
Double diffusive conjugate heat transfer: Part I
Azeem, Soudagar, Manzoor Elahi M.
2018-05-01
The present work is undertaken to investigate the effect of solid wall being placed at left of square cavity filled with porous medium. The presence of a solid wall in the porous medium turns the situation into a conjugate heat transfer problem. The boundary conditions are such that the left vertical surface is maintained at highest temperature and concentration whereas right vertical surface at lowest temperature and concentration in the medium. The top and bottom surfaces are adiabatic. The additional conduction equation along with the regular momentum and energy equations of porous medium are solved in an iterative manner with the help of finite element method. It is seen that the heat and mass transfer rate is lesser due to smaller thermal and concentration gradients.
Heat transfer modeling an inductive approach
Sidebotham, George
2015-01-01
This innovative text emphasizes a "less-is-more" approach to modeling complicated systems such as heat transfer by treating them first as "1-node lumped models" that yield simple closed-form solutions. The author develops numerical techniques for students to obtain more detail, but also trains them to use the techniques only when simpler approaches fail. Covering all essential methods offered in traditional texts, but with a different order, Professor Sidebotham stresses inductive thinking and problem solving as well as a constructive understanding of modern, computer-based practice. Readers learn to develop their own code in the context of the material, rather than just how to use packaged software, offering a deeper, intrinsic grasp behind models of heat transfer. Developed from over twenty-five years of lecture notes to teach students of mechanical and chemical engineering at The Cooper Union for the Advancement of Science and Art, the book is ideal for students and practitioners across engineering discipl...
Fem Formulation for Heat and Mass Transfer in Porous Medium
Azeem; Soudagar, Manzoor Elahi M.; Salman Ahmed, N. J.; Anjum Badruddin, Irfan
2017-08-01
Heat and mass transfer in porous medium can be modelled using three partial differential equations namely, momentum equation, energy equation and mass diffusion. These three equations are coupled to each other by some common terms that turn the whole phenomenon into a complex problem with inter-dependable variables. The current article describes the finite element formulation of heat and mass transfer in porous medium with respect to Cartesian coordinates. The problem under study is formulated into algebraic form of equations by using Galerkin's method with the help of two-node linear triangular element having three nodes. The domain is meshed with smaller sized elements near the wall region and bigger size away from walls.
Low-melting point heat transfer fluid
Cordaro, Joseph Gabriel; Bradshaw, Robert W.
2010-11-09
A low-melting point, heat transfer fluid made of a mixture of five inorganic salts including about 29.1-33.5 mol % LiNO.sub.3, 0-3.9 mol % NaNO.sub.3, 2.4-8.2 mol % KNO.sub.3, 18.6-19.9 mol % NaNO.sub.2, and 40-45.6 mol % KNO.sub.2. These compositions can have liquidus temperatures below 80.degree. C. for some compositions.
Computer graphics in heat-transfer simulations
International Nuclear Information System (INIS)
Hamlin, G.A. Jr.
1980-01-01
Computer graphics can be very useful in the setup of heat transfer simulations and in the display of the results of such simulations. The potential use of recently available low-cost graphics devices in the setup of such simulations has not been fully exploited. Several types of graphics devices and their potential usefulness are discussed, and some configurations of graphics equipment are presented in the low-, medium-, and high-price ranges
The Winfrith 9MW heat transfer rig
International Nuclear Information System (INIS)
Obertelli, J.D.
1976-01-01
The Winfrith 9MW Rig is used for studying heat transfer and flow resistance in a variety of test sections at system pressures up to 68 bar. The basic rig and its instrumentation are discussed together with the characteristics of the test section design. The rig has been used in studies involving the full scale simulation of Steam Generating Heavy Water (SGHW) fuel assemblies and the paper discusses the measurements made in this type of study. (author)
Principles of heat and mass transfer
Incropera, Frank P; Bergman, Theodore L; Lavine, Adrienne S
2013-01-01
Completely updated, the seventh edition provides engineers with an in-depth look at the key concepts in the field. It incorporates new discussions on emerging areas of heat transfer, discussing technologies that are related to nanotechnology, biomedical engineering and alternative energy. The example problems are also updated to better show how to apply the material. And as engineers follow the rigorous and systematic problem-solving methodology, they'll gain an appreciation for the richness and beauty of the discipline.
Heat transfer in multi-phase materials
Öchsner, Andreas
2011-01-01
This book provides a profound understanding, which physical processes and mechanisms cause the heat transfer in composite and cellular materials. It shows models for all important classes of composite materials and introduces into the latest advances. In three parts, the book covers Composite Materials (Part A), Porous and Cellular Materials (Part B) and the appearance of a conjoint solid phase and fluid aggregate (Part C).
Heat transfer studies on spiral plate heat exchanger
Directory of Open Access Journals (Sweden)
Rajavel Rangasamy
2008-01-01
Full Text Available In this paper, the heat transfer coefficients in a spiral plate heat exchanger are investigated. The test section consists of a plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot water (hot fluid is varying from 0.5 to 0.8 kg/s and the mass flow rate of cold water (cold fluid varies from 0.4 to 0.7 kg/s. Experiments have been conducted by varying the mass flow rate, temperature, and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the Nusselt number which can be used for practical applications is proposed.
Heat transfer to accelerating gas flows
International Nuclear Information System (INIS)
Kennedy, T.D.A.
1978-01-01
The development of fuels for gas-cooled reactors has resulted in a number of 'gas loop' experiments in materials-testing research reactors. In these experiments, efforts are made to reproduce the conditions expected in gas-cooled power reactors. Constant surface temperatures are sought over a short (300 mm) fuelled length, and because of entrance effects, an accelerating flow is required to increase the heat transfer down-stream from the entrance. Strong acceleration of a gas stream will laminarise the flow even at Reynolds Numbers up to 50000, far above values normally associated with laminar flow. A method of predicting heat transfer in this situation is presented here. An integral method is used to find the velocity profile; this profile is then used in an explicit finite-difference solution of the energy equation to give a temperature profile and resultant heat-transfer coefficient values. The Kline criterion, which compares viscous and disruptive forces, is used to predict whether the flow will be laminar. Experimental results are compared with predictions, and good agreement is found to exist. (author)
Conjugate Problems in Convective Heat Transfer: Review
Directory of Open Access Journals (Sweden)
Abram Dorfman
2009-01-01
Full Text Available A review of conjugate convective heat transfer problems solved during the early and current time of development of this modern approach is presented. The discussion is based on analytical solutions of selected typical relatively simple conjugate problems including steady-state and transient processes, thermal material treatment, and heat and mass transfer in drying. This brief survey is accompanied by the list of almost two hundred publications considering application of different more and less complex analytical and numerical conjugate models for simulating technology processes and industrial devices from aerospace systems to food production. The references are combined in the groups of works studying similar problems so that each of the groups corresponds to one of selected analytical solutions considered in detail. Such structure of review gives the reader the understanding of early and current situation in conjugate convective heat transfer modeling and makes possible to use the information presented as an introduction to this area on the one hand, and to find more complicated publications of interest on the other hand.
Experimental heat transfer in tube bundle
International Nuclear Information System (INIS)
Khattab, M.; Mariy, A.; Habib, M.
1983-01-01
Previous work has looked for the problem of heat transfer with flow parallel to rod bundle either by treating each rod individually as a separate channel or by treating the bundle as one unit. The present work will consider the existence of both the central and corner rods simultaneously inside the cluster itself under the same working conditions. The test section is geometrically similar to the fuel assembly of the Egyptian Research Reactor-1. The hydro-thermal performance of bundle having 16 - stainless steel tubes arranged in square array of 1.5 pitch to diameter ratio is investigated. Surface temperature and pressure distributions are determined. Average heat transfer coefficient for both central and corner tubes are correlated. Also, pressure drop and friction factor correlations are predicted. The maximum experimental range of the measured parameters are determined in the nonboiling region at 1400 Reynolds number and 3.64 W/cm 2 . It is found that the average heat transfer coefficient of the central tube is higher than that of the corner tube by 27%. Comparison with the previous work shows satisfactory agreement particularly with the circular tubes correlation - Dittus et al. - at 104 Reynolds number
Numerical Analysis of Heat Transfer During Quenching Process
Madireddi, Sowjanya; Krishnan, Krishnan Nambudiripad; Reddy, Ammana Satyanarayana
2018-04-01
A numerical model is developed to simulate the immersion quenching process of metals. The time of quench plays an important role if the process involves a defined step quenching schedule to obtain the desired characteristics. Lumped heat capacity analysis used for this purpose requires the value of heat transfer coefficient, whose evaluation requires large experimental data. Experimentation on a sample work piece may not represent the actual component which may vary in dimension. A Fluid-Structure interaction technique with a coupled interface between the solid (metal) and liquid (quenchant) is used for the simulations. Initial times of quenching shows boiling heat transfer phenomenon with high values of heat transfer coefficients (5000-2.5 × 105 W/m2K). Shape of the work piece with equal dimension shows less influence on the cooling rate Non-uniformity in hardness at the sharp corners can be reduced by rounding off the edges. For a square piece of 20 mm thickness, with 3 mm fillet radius, this difference is reduced by 73 %. The model can be used for any metal-quenchant combination to obtain time-temperature data without the necessity of experimentation.
Heat transfer and performance analysis of thermoelectric stoves
International Nuclear Information System (INIS)
Najjar, Yousef S.H.; Kseibi, Musaab M.
2016-01-01
Highlights: • Design and testing of a thermo electric stove. • Three biofuels namely: wood, peat and manure are used. • Heat transfer analysis is detailed. • Resulting thermoelectric energy for vital purposes in remote poor regions. • Evaluation of performance of the stove subcomponents. - Abstract: Access to electricity is one of the important challenges for remote poor regions of the world. Adding TEG (thermoelectric generators) to stoves can provide electricity for the basic benefits such as: operating radio, light, phones, medical instruments and other small electronic devices. Heat transfer analysis of a multi-purpose stove coupled with 12 TEG modules is presented. This analysis comprises a well aerodynamically designed combustor, finned TEG base plate, cooker and water heater beside the outer surface for space heating. Heat transfer analysis was also carried out for all the subcomponents of the stove, and performance predicted against the experimental results. It was found that the maximum power obtained is about 7.88 W using wood, manure or peat with an average overall efficiency of the stove about 60%.
An introduction to heat transfer. 2. rev. ed.
International Nuclear Information System (INIS)
Hell, F.
1979-01-01
This book represents a fundamental introduction to heat transfer. Practical problems and tables make the book useful for engeneers and students. The chapters include detailed informations together with exercises of convection, radiat heat transfer, thermal conduction and condensation. (CDS)
Refrigeration. Heat Transfer. Part I: Evaporators and Condensers
DEFF Research Database (Denmark)
Knudsen, Hans-Jørgen Høgaard
2002-01-01
The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation.......The note gives an introduction to heat transfer with phase shift. Pool Boiling, Flow Boiling, Condensation....
Heat transfer coefficients during quenching of steels
Energy Technology Data Exchange (ETDEWEB)
Hasan, H.S.; Jalil, J.M. [University of Technology, Department of Electromechanical Engineering, Baghdad (Iraq); Peet, M.J.; Bhadeshia, H.K.D.H. [University of Cambridge, Department of Materials Science and Metallurgy, Cambridge (United Kingdom)
2011-03-15
Heat transfer coefficients for quenching in water have been measured as a function of temperature using steel probes for a variety of iron alloys. The coefficients were derived from measured cooling curves combined with calculated heat-capacities. The resulting data were then used to calculate cooling curves using the finite volume method for a large steel sample and these curves have been demonstrated to be consistent with measured values for the large sample. Furthermore, by combining the estimated cooling curves with time-temperature-transformation (TTT) diagrams it has been possible to predict the variation of hardness as a function of distance via the quench factor analysis. The work should prove useful in the heat treatment of the steels studied, some of which are in the development stage. (orig.)
Heat transfer at a beam port corner
International Nuclear Information System (INIS)
Krinsky, S.
Along the general run of the vacuum chamber synchrotron radiation strikes the wall at a glancing angle of about 5.6 0 . The heat source is well-approximated by a ribbon of uniform power density having a small vertical height and an infinite azimuthal length. The heat transfer problem reduces to one in two-dimensions and it has been considered in a previous note. At the corner of a beam port the angle of incidence becomes 90 0 , so the temperature rises much higher than elsewhere. Since the power density at the corner is not uniform in its azimuthal dependence, but is strongly peaked at the point of normal incidence, two-dimensional heat flow is not a good approximation. The rectangular 3d problem is considered. This is easily solved and yields a good first estimate of the temperature rise at the corner
Heat transfer operators associated with quantum operations
International Nuclear Information System (INIS)
Aksak, C; Turgut, S
2011-01-01
Any quantum operation applied on a physical system is performed as a unitary transformation on a larger extended system. If the extension used is a heat bath in thermal equilibrium, the concomitant change in the state of the bath necessarily implies a heat exchange with it. The dependence of the average heat transferred to the bath on the initial state of the system can then be found from the expectation value of a Hermitian operator, which is named as the heat transfer operator (HTO). The purpose of this paper is to investigate the relation between the HTOs and the associated quantum operations. Since any given quantum operation on a system can be realized by different baths and unitaries, many different HTOs are possible for each quantum operation. On the other hand, there are also strong restrictions on the HTOs which arise from the unitarity of the transformations. The most important of these is the Landauer erasure principle. This paper is concerned with the question of finding a complete set of restrictions on the HTOs that are associated with a given quantum operation. An answer to this question has been found only for a subset of quantum operations. For erasure operations, these characterizations are equivalent to the generalized Landauer erasure principle. For the case of generic quantum operations, however, it appears that the HTOs obey further restrictions which cannot be obtained from the entropic restrictions of the generalized Landauer erasure principle.
Heat transfer characteristics of induced mixed convection
International Nuclear Information System (INIS)
Weiss, Y.; Lahav, C.; Szanto, M.; Shai, I.
1996-01-01
In the present work we focus our attention on the opposed Induced Mixed Convection case, i.e. the flow field structure in a vertical cylinder, closed at its bottom, opens at the top, and being heated circumferentially. The paper reports an experimental study of this complex heat transfer process. For a better understanding of the flow field and the related heat transfer process, two different experimental systems were built. The first was a flow visualization system, with water as the working fluid, while the second system enabled quantitative measurements of the temperature field in air. All the experiments were performed in the turbulent flow regime. In order to learn about all possible flow regimes, the visualization tests were conducted in three different length-to-diameter ratios (1/d=1,5,10). Quantitative measurements of the cylindrical wall temperature, as well as the radial and axial temperature profiles in the flow field, were taken in the air system. Based on the visualization observation and the measured wall temperature profile, it was found that the OIMC can be characterized by three main regimes: a mixing regime at the top, a central turbulent core and a boundary layer type of flow adjacent to the heated wall. (authors)
High performance passive solar heating system with heat pipe energy transfer and latent heat storage
Dijk, van H.A.L.; Galen, van E; Hensen, J.L.M.; Wit, de M.H.
1983-01-01
Preliminar results are reported from a current project on the development of a high performance passive solar heating system. Two special components are introduced: a. A heat pipe as a thermal diode tube for the efficient transfer of collected solar heat from the absorber plate to behind an
A Review of Wettability Effect on Boiling Heat Transfer Enhancement
International Nuclear Information System (INIS)
Seo, Gwang Hyeok; Jeun, Gyoo Dong; Kim, Sung Joong
2012-01-01
Critical heat flux (CHF) and nucleate boiling heat transfer coefficient (NBHTC) are the key parameters characterizing pool boiling heat transfer. These variables are complicatedly related to thermal-hydraulic parameters of surface wettability, nucleation site density, bubble departure diameter and frequency, to mention a few. In essence, wettability effect on pool boiling heat transfer has been a major fuel to enhance the CHF. Often, however, the improved wettability effect hinders the nucleate boiling. Thus a comprehensive review of such wettability effect may enlighten a further study in this boiling heat transfer area. Phan et al. described surface wettability effects on boiling heat transfer
Subcooled boiling heat transfer on a finned surface
International Nuclear Information System (INIS)
Kowalski, J.E.; Tran, V.T.; Mills, P.J.
1992-01-01
Experimental and numerical studies have been performed to determine the heat transfer coefficients from a finned cylindrical surface to subcooled boiling water. The heat transfer rates were measured in an annular test section consisting of an electrically heated fuel element simulator (FES) with eight longitudinal, rectangular fins enclosed in a glass tube. A two-dimensional finite-element heat transfer model using the Galerkin method was employed to determine the heat transfer coefficients along the periphery of the FES surface. An empirical correlation was developed to predict the heat transfer coefficients during subcooled boiling. The correlation agrees well with the measured data. (6 figures) (Author)
International Nuclear Information System (INIS)
Xu, Weiguo; Ren, Depeng; Ye, Qing; Liu, Guodong; Lu, Huilin; Wang, Shuai
2016-01-01
Graphical abstract: Predicted laminar Nusselt number using regression correlation of Therminol-55 heat transfer fluid is in agreement with experiments in the rifled tube. - Highlights: • Heat transfer coefficient and friction factor are measured and predicted in the rifled tube. • Correlations for Nusselt number and friction factor are proposed. • The roughness height of 0.425 mm in transition SST model is suggested as an input parameter. • k–kl–ω transition and transition SST models are recommended for laminar–turbulent transition. • Thermal enhancement factor and synergy angle are predicted in the rifled tube. - Abstract: Simulations and experiments of flow and heat transfer behavior of Therminol-55 heat transfer fluid have been conducted in a horizontal rifled tube with outer diameter and inner diameter 25.0 and 20.0 mm, pitch and rib height of 12.0 and 1.0 mm, respectively. Numerical simulations of three-dimensional flow behavior of Therminol-55 heat transfer fluid are carried out using FLUENT code in the rifled tube. Experimental results show that the heat transfer and thermal performance of Therminol-55 heat transfer fluid in the rifled tube are considerably improved compared to those of the smooth tube. The Nusselt number increases with the increase of Reynolds number, and is from 3.5 to 5.1 times over the smooth tube. Also, the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.2 and 4.2 times over the smooth tube. Predictive Nusselt number and friction factor correlations have been presented. The numerical results show that the laminar flow model is valid only at lower Reynolds number in the developed laminar flow of rifled tube. The k–kl–ω transition model and transition SST model with roughness of 0.425 mm are recommended for the predictions of transition process from laminar to turbulent flow in the rifled tube.
Study on hybrid ground-coupled heat pump systems
Energy Technology Data Exchange (ETDEWEB)
Yi, Man; Hongxing, Yang [Renewable Energy Research Group, The Hong Kong Polytechnic University, Hong Kong (China); Zhaohong, Fang [School of Thermal Energy Engineering, Shandong Architecture University, Jinan (China)
2008-07-01
Although ground-coupled heat pump (GCHP) systems are becoming attractive air-conditioning systems in some regions, the significant drawback for their wider application is the high initial cost. Besides, more energy is rejected into ground by the GCHP system installed in cooling-dominated buildings than the energy extracted from ground on an annual basis and this imbalance can result in the degradation of system performance. One of the available options that can resolve these problems is to apply the hybrid ground-coupled heat pump (HGCHP) systems, with supplemental heat rejecters for rejecting extra thermal energy when they are installed in cooling-dominated buildings. This paper presents a practical hourly simulation model of the HGCHP system by modeling the heat transfer of its main components. The computer program developed on this hourly simulation model can be used to calculate the operating data of the HGCHP system according to the building load. The design methods and running control strategies of the HGCHP system for a sample building are investigated. The simulation results show that proper HGCHP system can effectively reduce both the initial cost and the operating cost of an air-conditioning system compared with the traditional GCHP system used in cooling-dominated buildings. (author)
POST CRITICAL HEAT TRANSFER AND FUEL CLADDING OXIDATION
Directory of Open Access Journals (Sweden)
Vojtěch Caha
2016-12-01
Full Text Available The knowledge of heat transfer coefficient in the post critical heat flux region in nuclear reactor safety is very important. Although the nuclear reactors normally operate at conditions where critical heat flux (CHF is not reached, accidents where dryout occur are possible. Most serious postulated accidents are a loss of coolant accident or reactivity initiated accident which can lead to CHF or post CHF conditions and possible disruption of core integrity. Moreover, this is also influenced by an oxide layer on the cladding surface. The paper deals with the study of mathematical models and correlations used for heat transfer calculation, especially in post dryout region, and fuel cladding oxidation kinetics of currently operated nuclear reactors. The study is focused on increasing of accuracy and reliability of safety limit calculations (e.g. DNBR or fuel cladding temperature. The paper presents coupled code which was developed for the solution of forced convection flow in heated channel and oxidation of fuel cladding. The code is capable of calculating temperature distribution in the coolant, cladding and fuel and also the thickness of an oxide layer.
Enhancement of heat and mass transfer by cavitation
International Nuclear Information System (INIS)
Zhang, Y N; Du, X Z; Xian, H Z; Zhang, Y N
2015-01-01
In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment
Active control of near-field radiative heat transfer between graphene-covered metamaterials
Zhao, Qimei; Zhou, Ting; Wang, Tongbiao; Liu, Wenxing; Liu, Jiangtao; Yu, Tianbao; Liao, Qinghua; Liu, Nianhua
2017-04-01
In this study, the near-field radiative heat transfer between graphene-covered metamaterials is investigated. The electric surface plasmons (SPs) supported by metamaterials can be coupled with the SPs supported by graphene. The near-field heat transfer between the graphene-covered metamaterials is significantly larger than that between metamaterials because of the strong coupling in our studied frequency range. The relationship between heat flux and chemical potential is studied for different vacuum gaps. Given that the chemical potential of graphene can be tuned by the external electric field, heat transfer can be actively controlled by modulating the chemical potential. The heat flux for certain vacuum gaps can reach a maximum value when the chemical potential is at a particular value. The results of this study are beneficial for actively controlling energy transfer.
Active control of near-field radiative heat transfer between graphene-covered metamaterials
International Nuclear Information System (INIS)
Zhao, Qimei; Zhou, Ting; Wang, Tongbiao; Liu, Wenxing; Liu, Jiangtao; Yu, Tianbao; Liao, Qinghua; Liu, Nianhua
2017-01-01
In this study, the near-field radiative heat transfer between graphene-covered metamaterials is investigated. The electric surface plasmons (SPs) supported by metamaterials can be coupled with the SPs supported by graphene. The near-field heat transfer between the graphene-covered metamaterials is significantly larger than that between metamaterials because of the strong coupling in our studied frequency range. The relationship between heat flux and chemical potential is studied for different vacuum gaps. Given that the chemical potential of graphene can be tuned by the external electric field, heat transfer can be actively controlled by modulating the chemical potential. The heat flux for certain vacuum gaps can reach a maximum value when the chemical potential is at a particular value. The results of this study are beneficial for actively controlling energy transfer. (paper)
Low-Flow Film Boiling Heat Transfer on Vertical Surfaces
DEFF Research Database (Denmark)
Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.
1976-01-01
The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer...... length, an average film boiling heat transfer coefficient is obtained....
Unravelling convective heat transfer in the Rotated Arc Mixer
Speetjens, M.F.M.; Baskan, O.; Metcalfe, G.; Clercx, H.J.H.
2014-01-01
Thermal homogenization is essentially a transient problem and convective heat transfer by (chaotic) advection is known to accelerate this process. Convective heat transfer traditionally is examined in terms of heat-transfer coefficients at domain walls and characterised by Nusselt relations.
Visualisation of heat transfer in 3D unsteady flows
Speetjens, M.F.M.; Steenhoven, van A.A.
2010-01-01
Heat transfer in fluid flows traditionally is examined in terms oftemperature field and heat-transfer coefficients at non-adiabaticwalls. However, heat transfer may alternatively be considered asthe transport of thermal energy by the total convective-conductiveheat flux in a way analogous to the
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
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…
SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris
International Nuclear Information System (INIS)
Coryell, E.W.; Siefken, L.J.; Paik, S.
1998-01-01
Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and non-porous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of non-porous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. A design is also described for implementing a model of heat transfer by radiation from debris to the interstitial fluid. A design is described for implementation of models for flow losses and interphase drag in porous debris. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region
Heat transfer and critical heat flux in a spiral flow in an asymmetrical heated tube
International Nuclear Information System (INIS)
Boscary, J.; Association Euratom-CEA, Centre d'Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance
1997-03-01
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author)
Heat transfer and critical heat flux in a asymmetrically heated tube helicoidal flow
International Nuclear Information System (INIS)
Boscary, J.
1995-10-01
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs
Modelling of heat transfer to fluids at a supercritical pressure
International Nuclear Information System (INIS)
Shuisheng, He
2014-01-01
A key feature of Supercritical Water-cooled Reactor (SCWR) is that, by raising the pressure of the reactor coolant fluid above the critical value, a phase change crisis is avoided. However, the changes in water density as it flows through the core of an SCWR are actually much higher than in the current water-cooled reactors. In a typical design, the ratio of the density of water at the core inlet to that at exit is as high as 7:1. Other fluid properties also vary significantly, especially around the pseudo-critical temperature (at which the specific heat capacity peaks). As a result, turbulent flow and heat transfer behaviour in the core is extremely complex and under certain conditions, significant heat transfer deterioration can potentially occur. Consequently, understanding and being able to predict flow and heat transfer phenomena under normal steady operation conditions and in start-up and hypothetical fault conditions are fundamental to the design of SCWR. There have been intensive studies on flow and heat transfer to fluids at supercritical pressure recently and several excellent review papers have been published. In the talk, we will focus on some turbulence modelling issues encountered in CFD simulations. The talk will first discuss some flow and heat transfer issues related to fluids at supercritical pressures and their potential implications in SCWR, and some recent developments in the understanding and modelling techniques of such problems, which will be followed by an outlook for some future developments.Factors which have a major influence on the flow and will be discussed are buoyancy and flow acceleration due to thermal expansion (both are due to density variations but involve different mechanisms) and the nonuniformity of other fluid properties. In addition, laminar-turbulent flow transition coupled with buoyancy and flow acceleration plays an important role in heat transfer effectiveness and wall temperature in the entrance region but such
Transfer coefficients in elliptical tubes and plate fin heat exchangers
International Nuclear Information System (INIS)
Saboya, S.M.
1979-09-01
Mean transfer coefficients in elliptical tubes and plate fin heat exchangers were determined by application of heat and mass transfer analogy in conjunction with the naphthalene sublimation technique. The transfer coefficients are presented in a dimensionless form as functions of the Reynolds number. By using the least squares method analytical expressions for the transfer coefficients were determined with low scattering. (E.G.) [pt
46 CFR 153.430 - Heat transfer systems; general.
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 heat...
Modeling of heat and mass transfer in lateritic building envelopes
International Nuclear Information System (INIS)
Meukam, Pierre
2004-10-01
The aim of the present work is to investigate the behavior of building envelopes made of local lateritic soil bricks subjected to different climatic conditions. The analysis is developed for the prediction of the temperature, relative humidity and water content behavior within the walls. The building envelopes studied in this work consist of lateritic soil bricks with incorporation of natural pozzolan or sawdust in order to obtain small thermal conductivity and low-density materials, and limit the heat transfer between the atmospheric climate and the inside environment. In order to describe coupled heat and moisture transfer in wet porous materials, the coupled equations were solved by the introduction of diffusion coefficients. A numerical model HMtrans, developed for prediction of beat and moisture transfer in multi-layered building components, was used to simulate the temperature, water content and relative humidity profiles within the building envelopes. The results allow the prediction of the duration of the exposed building walls to the local weather conditions. They show that for any of three climatic conditions considered, relative humidity and water content do not exceed 87% and 5% respectively. There is therefore minimum possibility of water condensation in the materials studied. The durability of building envelopes made of lateritic soil bricks with incorporation of natural pozzolan or sawdust is not strongly affected by the climatic conditions in tropical and equatorial regions. (author)
Transfer of heat to fluidized-solids beds
Energy Technology Data Exchange (ETDEWEB)
1952-10-16
The improvement in the method described and claimed in patent application 14,363/47 (136,186) for supplying heat to a dense turbulent mass of solid fluidized by a gas flowing upwardly therethrough and subjected to a high temperature in a treating zone, by heat transfer through heat-transfer surfaces of heat-transfer elements in contact with the said turbulent mass of finely divided solid and heated by means of a fluid heating medium, including burning fuels comprising contacting the said heat-transfer surfaces with a fuel and a combustion supporting gas under such conditions that the combustion of the fuel is localized in the heat-transfer element near the point of entry of the fuel and combustion-supporting gas and a substantial temperature gradient is maintained along the path of said fuel combustion-supporting gas and combustion products through the said heat-transfer element.
Analysis of Heat Transfer in Cooling of a Hot Plate by Planar Impingement Jet
International Nuclear Information System (INIS)
Ahn, Dae Hwan; Kim, Dong Sik
2009-01-01
Water jet impingement cooling is used to remove heat from high-temperature surfaces such as hot steel plates in the steel manufacturing process (thermo-mechanical cooling process; TMCP). In those processes, uniform cooling is the most critical factor to ensure high strength steel and good quality. In this study, experiments are performed to measure the heat transfer coefficient together with the inverse heat conduction problem (IHCP) analysis for a plate cooled by planar water jet. In the inverse heat transfer analysis, spatial and temporal variations of heat transfer coefficient, with no information regarding its functional form, are determined by employing the conjugate gradient method with an adjoint problem. To estimate the two dimensional distribution of heat transfer coefficient and heat flux for planar waterjet cooling, eight thermo-couple are installed inside the plate. The results show that heat transfer coefficient is approximately uniform in the span-wise direction in the early stage of cooling. In the later stage where the forced-convection effect is important, the heat transfer coefficient becomes larger in the edge region. The surface temperature vs. heat flux characteristics are also investigated for the entire boiling regimes. In addition, the heat transfer rate for the two different plate geometries are compared at the same Reynolds number
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
Brouwers, H.J.H.
1996-01-01
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall
Heat transfer model for quenching by submerging
International Nuclear Information System (INIS)
Passarella, D N; Varas, F; MartIn, E B
2011-01-01
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Heat transfer model for quenching by submerging
Energy Technology Data Exchange (ETDEWEB)
Passarella, D N; Varas, F [Departamento de Matematica Aplicada II, E.T.S. de Ing. de Telecomunicacion, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain); MartIn, E B, E-mail: diego@dma.uvigo.es, E-mail: fvaras@uvigo.es, E-mail: emortega@uvigo.es [Area de Mecanica de Fluidos, E.T.S. de Ing. Industriales, Universidad de Vigo, Campus Marcosende, 36310 Vigo (Spain)
2011-05-01
In quenching by submerging the workpiece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamics of these phenomena is very complex and the corresponding heat fluxes are strongly dependent on local flow variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses. In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer is presented here. The model is based on the drift-flux mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface of the piece. The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed. To test the model, a simple flow condition was analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and its effect on the cooling rates on different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.
Han, Chang-Liang; Ren, Jing-Jie; Dong, Wen-Ping; Bi, Ming-Shu
2016-09-01
The submerged combustion vaporizer (SCV) is indispensable general equipment for liquefied natural gas (LNG) receiving terminals. In this paper, numerical simulation was conducted to get insight into the flow and heat transfer characteristics of supercritical LNG on the tube-side of SCV. The SST model with enhanced wall treatment method was utilized to handle the coupled wall-to-LNG heat transfer. The thermal-physical properties of LNG under supercritical pressure were used for this study. After the validation of model and method, the effects of mass flux, outer wall temperature and inlet pressure on the heat transfer behaviors were discussed in detail. Then the non-uniformity heat transfer mechanism of supercritical LNG and effect of natural convection due to buoyancy change in the tube was discussed based on the numerical results. Moreover, different flow and heat transfer characteristics inside the bend tube sections were also analyzed. The obtained numerical results showed that the local surface heat transfer coefficient attained its peak value when the bulk LNG temperature approached the so-called pseudo-critical temperature. Higher mass flux could eliminate the heat transfer deteriorations due to the increase of turbulent diffusion. An increase of outer wall temperature had a significant influence on diminishing heat transfer ability of LNG. The maximum surface heat transfer coefficient strongly depended on inlet pressure. Bend tube sections could enhance the heat transfer due to secondary flow phenomenon. Furthermore, based on the current simulation results, a new dimensionless, semi-theoretical empirical correlation was developed for supercritical LNG convective heat transfer in a horizontal serpentine tube. The paper provided the mechanism of heat transfer for the design of high-efficiency SCV.
International Nuclear Information System (INIS)
Son, Hyung M.; Suh, Kune Y.
2012-01-01
Highlights: ► Performed experiment for the upward SCO 2 flow surrounded by highly conducting metal. ► Selected dimensionless groups representing the property variations and buoyancy. ► Developed the heat transfer correlation for the mixed thermal boundary condition. ► Wrote a finite element heat transfer code to find the appropriate correlation. ► Coupled the 1D convection and 2D heat conduction via heat transfer coefficient. - Abstract: This paper presents heat transfer characteristics of supercritical carbon dioxide flow inside vertical circular pipe surrounded by highly conducting material, and develops an adequate tool to test the performance of available heat transfer correlations with. The possible situations are illustrated for the nuclear power plant to which the above-mentioned geometric configuration might be applicable. An experimental loop with vertical circular geometry is designed and constructed to test the upward flow in supercritical state when the axial heat transfer is enhanced by the surrounding metals, resulting in a wall boundary condition between the constant heat flux and temperature. The set of correlations and important findings are critically reviewed from extensive literature survey. Incorporating nondimensional groups resorting to past insights from the available literature, a convective heat transfer correlation is proposed. The optimization procedure is described which utilizes a random walk method along with the in-house finite element heat transfer code to determine the coefficients of the proposed heat transfer correlation. The proposed methodology can be applied to evaluation of heat transfer when the heat transfer coefficient data cannot directly be determined from the experiment.
Heat transfer unit and method for prefabricated vessel
Tamburello, David A.; Kesterson, Matthew R; Hardy, Bruce J.
2017-11-07
Vessel assemblies, heat transfer units for prefabricated vessels, and methods for heat transfer prefabricated vessel are provided. A heat transfer unit includes a central rod, and a plurality of peripheral rods surrounding the central rod and connected to the central rod. The plurality of peripheral rods are movable between a first collapsed position and a second bowed position, wherein in the second bowed position a midpoint of each of the plurality of peripheral rods is spaced from the central rod relative to in the first position. The heat transfer unit further includes a heat transfer element connected to one of the plurality of peripheral rods.
Ground source heat pump performance in case of high humidity soil and yearly balanced heat transfer
International Nuclear Information System (INIS)
Schibuola, Luigi; Tambani, Chiara; Zarrella, Angelo; Scarpa, Massimiliano
2013-01-01
Highlights: • GSHPs are simulated in case of humid soil and yearly balanced heat transfer. • Humid soil and yearly balanced heat transfer imply higher compactness of GSHPs. • Resulting GSHPs are compared with other traditional and innovative HVAC systems. • GSHPs score best, especially in case of inverter-driven compressors. - Abstract: Ground source heat pump (GSHP) systems are spreading also in Southern Europe, due to their high energy efficiency both in heating and in cooling mode. Moreover, they are particularly suitable in historical cities because of difficulties in the integration of heating/cooling systems into buildings subjected to historical preservation regulations. In these cases, GSHP systems, especially the ones provided with borehole heat exchangers, are a suitable solution instead of gas boilers, air-cooled chillers or cooling towers. In humid soils, GSHP systems are even more interesting because of their enhanced performance due to higher values of soil thermal conductivity and capacity. In this paper, GSHP systems operating under these boundary conditions are analyzed through a specific case study set in Venice and related to the restoration of an historical building. With this analysis the relevant influences of soil thermal conductivity and yearly balanced heat transfer in the design of the borehole field are shown. In particular, the paper shows the possibility to achieve higher compactness of the borehole field footprint area when yearly balanced heat transfer in the borehole field is expected. Then, the second set of results contained in the paper shows how GSHP systems designed for high humidity soils and yearly balanced heat loads at the ground side, even if characterized by a compact footprint area, may still ensure better performance than other available and more common technologies such as boilers, air-cooled chillers, chillers coupled with cooling towers and heat pumps and chillers coupled with lagoon water. As a consequence
Lattice Boltzmann heat transfer model for permeable voxels
Pereira, Gerald G.; Wu, Bisheng; Ahmed, Shakil
2017-12-01
We develop a gray-scale lattice Boltzmann (LB) model to study fluid flow combined with heat transfer for flow through porous media where voxels may be partially solid (or void). Heat transfer in rocks may lead to deformation, which in turn can modulate the fluid flow and so has significant contribution to rock permeability. The LB temperature field is compared to a finite difference solution of the continuum partial differential equations for fluid flow in a channel. Excellent quantitative agreement is found for both Poiseuille channel flow and Brinkman flow. The LB model is then applied to sample porous media such as packed beds and also more realistic sandstone rock sample, and both the convective and diffusive regimes are recovered when varying the thermal diffusivity. It is found that while the rock permeability can be comparatively small (order milli-Darcy), the temperature field can show significant variation depending on the thermal convection of the fluid. This LB method has significant advantages over other numerical methods such as finite and boundary element methods in dealing with coupled fluid flow and heat transfer in rocks which have irregular and nonsmooth pore spaces.
Flow and heat transfer in a curved channel
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.
Convective heat transfer and infrared thermography.
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.
Computer aided heat transfer analysis in a laboratory scaled heat exchanger unit
International Nuclear Information System (INIS)
Gunes, M.
1998-01-01
In this study. an explanation of a laboratory scaled heat exchanger unit and a software which is developed to analyze heat transfer. especially to use it in heat transfer courses, are represented. Analyses carried out in the software through sample values measured in the heat exchanger are: (l) Determination of heat transfer rate, logarithmic mean temperature difference and overall heat transfer coefficient; (2)Determination of convection heat transfer coefficient inside and outside the tube and the effect of fluid velocity on these; (3)Investigation of the relationship between Nusselt Number. Reynolds Number and Prandtl Number by using multiple non-linear regression analysis. Results are displayed on the screen graphically
Development and application of soil coupled heat pump
Liu, Lu
2017-05-01
Soil coupled heat pump technology is a new clean heating mode, is the world's most energy efficient heating one of the ways. And because of the use of renewable geothermal resources with high heating performance so more and more people's attention. Although the use of soil-coupled heat pumps has been in use for more than 50 years (the first application in the United States), the market penetration of this technology is still in its infancy. This paper will focus on the development, characteristics and application of the coupled heat pump.
Computational fluid mechanics and heat transfer
Pletcher, Richard H; Anderson, Dale
2012-01-01
""I have always considered this book the best gift from one generation to the next in computational fluid dynamics. I earnestly recommend this book to graduate students and practicing engineers for the pleasure of learning and a handy reference. The description of the basic concepts and fundamentals is thorough and is crystal clear for understanding. And since 1984, two newer editions have kept abreast to the new, relevant, and fully verified advancements in CFD.""-Joseph J.S. Shang, Wright State University""Computational Fluid Mechanics and Heat Transfer is very well written to be used as a t
Thermal conductivity and heat transfer in superlattices
Energy Technology Data Exchange (ETDEWEB)
Chen, G; Neagu, M; Borca-Tasciuc, T
1997-07-01
Understanding the thermal conductivity and heat transfer processes in superlattice structures is critical for the development of thermoelectric materials and devices based on quantum structures. This work reports progress on the modeling of thermal conductivity of superlattice structures. Results from the models established based on the Boltzmann transport equation could explain existing experimental results on the thermal conductivity of semiconductor superlattices in both in plane and cross-plane directions. These results suggest the possibility of engineering the interfaces to further reduce thermal conductivity of superlattice structures.
Heat Transfer Model for Hot Air Balloons
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.
Experimental study on external condensation heat transfer characteristics of bellows
International Nuclear Information System (INIS)
Feng Dianyi; Hu Jiansheng
2008-01-01
Flow model and heat transfer of condensation flow outside of bellows have been theoretically and experimentally studied. The formula for calculation of condensation heat transfer coefficient was deduced, and corrected through experiment. The calculation results are accordant with the experimental ones, and the errors is less than 10%. The effect of bellows structure parameters and pipe diameter on the enhancement heat transfer has been investigated. It is found that in the steady flow region, the average condensation heat transfer coefficient in a bellows is 3 ∼ 5 times than that in a straight tube under the same conditions, and when considering the increasing in heat transfer area, the effectiveness of enhancement heat transfer is 5 ∼ 7 times than that in a straight tube. To facilitate the engineering design and application of bellows, the formula for the calculation of the average heat transfer coefficient of a fluid in a bellows was also given. (authors)
Simultaneous Heat and Mass Transfer Model for Convective Drying of Building Material
Upadhyay, Ashwani; Chandramohan, V. P.
2018-04-01
A mathematical model of simultaneous heat and moisture transfer is developed for convective drying of building material. A rectangular brick is considered for sample object. Finite-difference method with semi-implicit scheme is used for solving the transient governing heat and mass transfer equation. Convective boundary condition is used, as the product is exposed in hot air. The heat and mass transfer equations are coupled through diffusion coefficient which is assumed as the function of temperature of the product. Set of algebraic equations are generated through space and time discretization. The discretized algebraic equations are solved by Gauss-Siedel method via iteration. Grid and time independent studies are performed for finding the optimum number of nodal points and time steps respectively. A MATLAB computer code is developed to solve the heat and mass transfer equations simultaneously. Transient heat and mass transfer simulations are performed to find the temperature and moisture distribution inside the brick.
Heat Transfer Characteristics of SiC-coated Heat Pipe for Passive Decay Heat Removal
International Nuclear Information System (INIS)
Kim, Kyung Mo; Kim, In Guk; Jeong, Yeong Shin; Bang, In Cheol
2014-01-01
The main concern with the Fukushima accident was the failure of active and passive core cooling systems. The main function of existing passive decay heat removal systems is feeding additional coolant to the reactor core. Thus, an established emergency core cooling system (ECCS) cannot operate properly because of impossible depressurization under the station blackout (SBO) condition. Therefore, a new concept for passive decay heat removal system is required. In this study, an innovative hybrid control rod concept is considered for passive in-core decay heat removal that differs from the existing direct vessel injection core cooling system and passive auxiliary feedwater system (PAFS). The heat transfer between the evaporator and condenser sections occurs by phase change of the working fluid and capillary action induced by wick structures installed on the inner wall of the heat pipe. In this study, a hybrid control rod is developed to take the roles of both neutron absorption and heat removal by combining the functions of a heat pipe and control rod. Previous studies on enhancing the heat removal capacity of heat pipes used nanofluids, self-rewetting fluids, various wick structures and condensers. Many studies have examined the thermal performances of heat pipes using various nanofluids. They concluded that the enhanced thermal performance of the heat pipe using nanofluids is due to nanoparticle deposition on the wick structures. Thus, the wick structure of heat pipes has been modified by nanoparticle deposition to enhance the heat removal capacity. However, previous studies used relatively small heat pipes and narrow ranges of heat loads. The environment of a nuclear reactor is very specific, and the decay heat produced by fission products after shutdown is relatively large. Thus, this study tested a large-scale heat pipe over a wide range of power. The concept of a hybrid heat pipe for an advanced in-core decay heat removal system was introduced for complete
Heat Transfer Characteristics of SiC-coated Heat Pipe for Passive Decay Heat Removal
Energy Technology Data Exchange (ETDEWEB)
Kim, Kyung Mo; Kim, In Guk; Jeong, Yeong Shin; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)
2014-10-15
The main concern with the Fukushima accident was the failure of active and passive core cooling systems. The main function of existing passive decay heat removal systems is feeding additional coolant to the reactor core. Thus, an established emergency core cooling system (ECCS) cannot operate properly because of impossible depressurization under the station blackout (SBO) condition. Therefore, a new concept for passive decay heat removal system is required. In this study, an innovative hybrid control rod concept is considered for passive in-core decay heat removal that differs from the existing direct vessel injection core cooling system and passive auxiliary feedwater system (PAFS). The heat transfer between the evaporator and condenser sections occurs by phase change of the working fluid and capillary action induced by wick structures installed on the inner wall of the heat pipe. In this study, a hybrid control rod is developed to take the roles of both neutron absorption and heat removal by combining the functions of a heat pipe and control rod. Previous studies on enhancing the heat removal capacity of heat pipes used nanofluids, self-rewetting fluids, various wick structures and condensers. Many studies have examined the thermal performances of heat pipes using various nanofluids. They concluded that the enhanced thermal performance of the heat pipe using nanofluids is due to nanoparticle deposition on the wick structures. Thus, the wick structure of heat pipes has been modified by nanoparticle deposition to enhance the heat removal capacity. However, previous studies used relatively small heat pipes and narrow ranges of heat loads. The environment of a nuclear reactor is very specific, and the decay heat produced by fission products after shutdown is relatively large. Thus, this study tested a large-scale heat pipe over a wide range of power. The concept of a hybrid heat pipe for an advanced in-core decay heat removal system was introduced for complete
Parametric study of boiling heat transfer in porous media
International Nuclear Information System (INIS)
Shi, B.; Jones, B.G.; Pan, C.
1996-01-01
Detailed numerical modeling and parametric variation studies were conducted on boiling heat transfer processes in porous deposits with emphasis on applications associated with light water nuclear power reactor systems. The processes of boiling heat transfer in the porous corrosion deposits typically involve phase changes in finite volumetric regions in the porous media. The study examined such processes in two porous media configurations, without chimneys (homogeneous porous structures) and with chimneys (heterogeneous porous structures). A 1-D model and a 2-D model were developed to simulate two-phase flows with phase changes, without dry-out, inside the porous media for both structural configurations. For closure of the governing equations, an empirical correlation of the evaporation rate for phase changes inside the porous media was introduced. In addition, numerical algorithms were developed to solve the coupled nonlinear equations of mass, momentum, energy, capillary pressure, and evaporation rate. The distributions of temperature, thermodynamic saturation, liquid pressure, vapor pressure, liquid velocity, and vapor velocity were predicted. Furthermore, the effects of heat flux, system pressure, porosity, particle diameter, chimney population density, chimney radius, and crud thickness on the all superheat, critical heat flux, and minimum saturation were examined. The predictions were found to be in good agreement with the available experimental results
Quantum heat engine with coupled superconducting resonators
DEFF Research Database (Denmark)
Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.
2017-01-01
the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal......We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....
Simulation of whole building coupled hygrothermal-airflow transfer in different climates
International Nuclear Information System (INIS)
Qin Menghao; Walton, George; Belarbi, Rafik; Allard, Francis
2011-01-01
The coupled heat, air and moisture transfer between building envelopes and indoor air is complicated, and has a significant influence on the indoor environment and the energy performance of buildings. In the paper, a model for predicting coupled multi-zone hygrothermal-airflow transfer is presented. Both heat and moisture transfer in the building envelope and multi-zone indoor airflow are simultaneously considered; their interactions are modeled. The coupled system model is implemented into Matlab-Simulink, and is validated by using a series of testing tools and experiments. The new program is applied to investigate the moisture transfer effect on indoor air humidity and building energy consumption in different climates (hot-humid, temperate and hot-dry climates). The results show that not accounting for hygrothermal effects in modeling will result in overestimation of energy costs for hot and humid climate situations and possible over sizing of plant leading to inefficient operation.
International Nuclear Information System (INIS)
Sarkar, J.; Bhattacharyya, Souvik
2007-01-01
In the present study, the overall conductance and the overall heat transfer area per unit capacity of refrigeration and heat pump systems have been minimized analytically considering both internal and external irreversibilities with variable temperature (finite capacity) heat reservoirs. Hot and cold side refrigerant temperatures, conductance and heat transfer area ratios have been optimized to attain this goal. The results have been verified with the more elaborate numerical optimization results obtained for ammonia based vapour compression refrigeration and heat pump systems working with variable temperature reservoirs. It is observed that the analytical results for optimum refrigerant temperatures, minimum overall conductance and heat transfer area deviate marginally from the numerically optimized results (within 1%), if one assumes a constant heat rejection temperature. The deviation of minimum overall conductance and heat transfer area is more (about 20%), if one considers both the desuperheating and condensation regions separately. However, in the absence of complex and elaborate numerical models, the simple analytical results obtained here can be used as reasonably accurate preliminary guidelines for optimization of refrigeration and heat pump systems
The influence of soil moisture transfer on building heat loss via the ground
Janssen, H.M.; Carmeliet, J.; Hens, H.
2004-01-01
In this paper, the influence of soil moisture transfer on building heat loss via the ground is investigated by comparing fully coupled simulations with linear thermal simulations. The observed influences of coupling are (1) the larger amplitude of surface temperature, (2) the variation of thermal
Directory of Open Access Journals (Sweden)
I-Chung Liu
2012-01-01
Full Text Available We have analyzed the effects of variable heat flux and internal heat generation on the flow and heat transfer in a thin film on a horizontal sheet in the presence of thermal radiation. Similarity transformations are used to transform the governing equations to a set of coupled nonlinear ordinary differential equations. The obtained differential equations are solved approximately by the homotopy perturbation method (HPM. The effects of various parameters governing the flow and heat transfer in this study are discussed and presented graphically. Comparison of numerical results is made with the earlier published results under limiting cases.
Method of calculating heat transfer in furnaces of small power
Directory of Open Access Journals (Sweden)
Khavanov Pavel
2016-01-01
Full Text Available This publication presents the experiences and results of generalization criterion equation of importance in the analysis of the processes of heat transfer and thermal calculations of low-power heat generators cooled combustion chambers. With generalizing depending estimated contribution of radiation and convective heat transfer component in the complex for the combustion chambers of small capacity boilers. Determined qualitative and quantitative dependence of the integrated radiative-convective heat transfer from the main factors working combustion chambers of small volume.
Heat and mass transfer in building services design
Moss, Keith
1998-01-01
Building design is increasingly geared towards low energy consumption. Understanding the fundamentals of heat transfer and the behaviour of air and water movements is more important than ever before. Heat and Mass Transfer in Building Services Design provides an essential underpinning knowledge for the technology subjects of space heating, water services, ventilation and air conditioning. This new text: *provides core understanding of heat transfer and fluid flow from a building services perspective *complements a range of courses in building services engineering *
Research on Marine Boiler's Pressurized Combustion and Heat Transfer
Institute of Scientific and Technical Information of China (English)
Pingjian MING; Renqiu JIANG; Yanjun LI; Baozhi SUN
2005-01-01
The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
International Nuclear Information System (INIS)
Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht
2007-01-01
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in a circular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mass 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
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
Energy Technology Data Exchange (ETDEWEB)
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.
Simultaneous heat and moisture transfer in porous elements: transfer function method
International Nuclear Information System (INIS)
Souza, H.A. de.
1985-01-01
The presence of moisture in a porous element may strongly affect the transfer of heat through this element due to the processes which occur associated with the phase changes at the boundary surfaces and internally in the wall body. In addition, the structural properties of the element may also be meaningfully affected. The formulation of mathematical models for the simultaneous heat and mass transfer in porous elements results in a pair of nonlinear coupled equations for the temperature and moisture content distributions, in the material. It is supposed, in this work, that the actual variation of the properties of the porous medium is small in the range of variables which describe the specific problem to be analyzed. This enables us to work with linearized equations, making possible the use of linear solution methods. In this context, the present work deals with a linear procedure for the solution of simultaneous heat and moisture transfer problems in porous elements, sujected to arbitrary boundary conditions. This results in a linear relation between the heat and mass flux densities through the boundary surfaces of the elements and their associated potentials. It is shown that the model is consistent in asymptotical limiting cases; the model is then used for analyzing the drying process of a porous element, subjected to ambient actual conditions. (Author) [pt
Quantum heat engine with coupled superconducting resonators
Hardal, Ali Ü. C.; Aslan, Nur; Wilson, C. M.; Müstecaplıoǧlu, Özgür E.
2017-12-01
We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case. We explore the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures.
SCDAP/RELAP5 Modeling of Heat Transfer and Flow Losses in Lower Head Porous Debris
International Nuclear Information System (INIS)
Siefken, Larry James; Coryell, Eric Wesley; Paik, Seungho; Kuo, Han Hsiung
1999-01-01
Designs are described for implementing models for calculating the heat transfer and flow losses in porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head. Currently, the COUPLE model has the capability to model convective and radiative heat transfer from the surfaces of nonporous debris in a detailed manner and to model only in a simplistic manner the heat transfer from porous debris. In order to advance beyond the simplistic modeling for porous debris, designs are developed for detailed calculations of heat transfer and flow losses in porous debris. Correlations are identified for convective heat transfer in porous debris for the following modes of heat transfer; (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, and (5) film boiling. Interphase heat transfer is modeled in an approximate manner. Designs are described for models to calculate the flow losses and interphase drag of fluid flowing through the interstices of the porous debris, and to apply these variables in the momentum equations in the RELAP5 part of the code. Since the models for heat transfer and flow losses in porous debris in the lower head are designed for general application, a design is also described for implementation of these models to the analysis of porous debris in the core region. A test matrix is proposed for assessing the capability of the implemented models to calculate the heat transfer and flow losses in porous debris. The implementation of the models described in this report is expected to improve the COUPLE code calculation of the temperature distribution in porous debris and in the lower head that supports the debris. The implementation of these models is also expected to improve the calculation of the temperature and flow distribution in porous debris in the core region
Conjugate heat transfer for turbulent flow in a thick walled plain pipe
Directory of Open Access Journals (Sweden)
Canli Eyub
2018-01-01
Full Text Available Laminar and turbulent flow have their own characteristics in respect of heat transfer in pipes. While conjugate heat transfer is a major concern for a thick walled pipe with laminar flow inside it, there are limited studies about a turbulent flow in a thick walled plain pipe considering the conjugate heat transfer. In order to conduct such a work by means of in-house developed code, it was desired to make a preliminary investigation with commercially available CFD codes. ANSYS CFD was selected as the tool since it has a positive reputation in the literature for reliability. Defined heat transfer problem was solved with SIMPLE and Coupled Schemes for pressure velocity coupling and results are presented accordingly.
Heat and mass transfer during baking: product quality aspects
Asselman, A.; Straten, van G.; Hadiyanto, H.; Boom, R.M.; Esveld, D.C.; Boxtel, van A.J.B.
2005-01-01
Abstract Most food product qualities are developed during heating processes. Therefore the internal heating and mass transfer of water are important aspects in food processing. Heating of food products is mostly induced by convection heating. However, the number applications of convective heating in
EFLOD code for reflood heat transfer
International Nuclear Information System (INIS)
Gay, R.R.
1979-01-01
A computer code called EFLOD has been developed for simulation of the heat transfer and hydrodynamics of a nuclear power reactor during the reflood phase of a loss-of-coolant accident. EFLOD models the downcomer, lower plenum, core, and upper plenum of a nuclear reactor vessel using seven control volumes assuming either homogeneous or unequal-velocity, unequal-temperature (UVUT) models of two-phase flow, depending on location within the vessel. The moving control volume concept in which a single control volume models the quench region in the core and moves with the core liquid level was developed and implemented in EFLOD so that three control volumes suffice to model the core region. A simplified UVUT model that assumes saturated liquid above the quench front was developed to handle the nonhomogeneous flow situation above the quench region. An explicit finite difference routine is used to model conduction heat transfer in the fuel, gap, and cladding regions of the fuel rod. In simulation of a selected FLECHT-SET experimental run, EFLOD successfully predicted the midplane maximum temperature and turnaround time as well as the time-dependent advance of the core liquid level. However, the rate of advancement of the quench level and the ensuing liquid entrainment were overpredicted during the early part of the transient
Post CHF heat transfer and quenching
International Nuclear Information System (INIS)
Nelson, R.A.; Condie, K.G.
1980-01-01
This paper describes quantitatively new mechanisms in the post-CHF regime which provide understanding and predictive capability for several current two-phase forced convective heat transfer problems. These mechanisms are important in predicting rod temperature turnaround and quenching during the reflood phase of either a hypothetical loss-of-coolant accident (LOCA) or the FLECHT and Semiscale experiments. The mechanisms are also important to the blowdown phase of a LOCA or the recent Loss-of-Fluid Test (LOFT) experiments L2-2 and L2-3, which were 200% cold leg break transients. These LOFT experiments experienced total core quenching in the early part of the blowdown phase at high (1000 psia) pressures. The mechanisms are also important to certain pressurized water reactor (PWR) operational transients where the reactor may operate in the post-CHF regime for short periods of time. Accurate prediction of the post-CHF heat transfer including core quench during these transients is of prime importance to limit maximum cladding temperatures and prevent cladding deformation
Annual review of numerical fluid mechanics and heat transfer. Volume 1
International Nuclear Information System (INIS)
Chawla, T.C.
1987-01-01
Numerical techniqes for the analysis of problems in fluid mechanics and heat transfer are discussed, reviewing the results of recent investigations. Topics addressed include thermal radiation in particulate media with dependent and independent scattering, pressure-velocity coupling in incompressiblefluid flow, new explicit methods for diffusion problems, and one-dimensional reaction-diffusion equations in combustion theory. Consideration is given to buckling flows, multidimensional radiative-transfer analysis in participating media, freezing and melting problems, and complex heat-transfer processes in heat-generating horizontal fluid layers
Application of artificial neural network for heat transfer in porous cone
Athani, Abdulgaphur; Ahamad, N. Ameer; Badruddin, Irfan Anjum
2018-05-01
Heat transfer in porous medium is one of the classical areas of research that has been active for many decades. The heat transfer in porous medium is generally studied by using numerical methods such as finite element method; finite difference method etc. that solves coupled partial differential equations by converting them into simpler forms. The current work utilizes an alternate method known as artificial neural network that mimics the learning characteristics of neurons. The heat transfer in porous medium fixed in a cone is predicted using backpropagation neural network. The artificial neural network is able to predict this behavior quite accurately.
Fluid dynamics and heat transfer methods for the TRAC code
International Nuclear Information System (INIS)
Reed, W.H.; Kirchner, W.L.
1977-01-01
A computer code called TRAC is being developed for analysis of loss-of-coolant accidents and other transients in light water reactors. This code involves a detailed, multidimensional description of two-phase flow coupled implicitly through appropriate heat transfer coefficients with a simulation of the temperature field in fuel and structural material. Because TRAC utilizes about 1000 fluid mesh cells to describe an LWR system, whereas existing lumped parameter codes typically involve fewer than 100 fluid cells, we have developed new highly implicit difference techniques that yield acceptable computing times on modern computers. Several test problems for which experimental data are available, including blowdown of single pipe and loop configurations with and without heated walls, have been computed with TRAC. Excellent agreement with experimental results has been obtained. (author)
Fluid dynamics and heat transfer methods for the TRAC code
International Nuclear Information System (INIS)
Reed, W.H.; Kirchner, W.L.
1977-01-01
A computer code called TRAC is being developed for analysis of loss-of-coolant accidents and other transients in light water reactors. This code involves a detailed, multidimensional description of two-phase flow coupled implicitly through appropriate heat transfer coefficients with a simulation of the temperature field in fuel and structural material. Because TRAC utilizes about 1000 fluid mesh cells to describe an LWR system, whereas existing lumped parameter codes typically involve fewer than 100 fluid cells, new highly implicit difference techniques are developed that yield acceptable computing times on modern computers. Several test problems for which experimental data are available, including blowdown of single pipe and loop configurations with and without heated walls, have been computed with TRAC. Excellent agreement with experimental results has been obtained
DEFF Research Database (Denmark)
Feyissa, Aberham Hailu; Bøknæs, Niels; Nielsen, P.L.
factors leading to variations and uncertainties in prediction of the right process parameters. The current work is focused on modelling of OH of solid food pieces of varying sizes cooked in one batch. A 3D mathematical model of coupled heat transfer and electric field during OH of shrimps has been...
Ultrafast modulation of near-field heat transfer with tunable metamaterials
Cui, Longji; Huang, Yong; Wang, Ju; Zhu, Ke-Yong
2012-01-01
We propose a mechanism of active near-field heat transfer modulation relying on externally tunable metamaterials. A large modulation effect is observed and can be explained by the coupling of surface modes, which is dramatically varied in the presence of controllable magnetoelectric coupling in metamaterials. We finally discuss how a practical picosecond-scale thermal modulator can be made. This modulator allows manipulating nanoscale heat flux in an ultrafast and noncontact (by optical means...
Study on enhancement of heat transfer of RVACS
International Nuclear Information System (INIS)
Nishi, Yoshihisa; Kinoshita, Izumi
1989-01-01
As for the enhancement of heat transfer on Reactor Vessel Auxiliary Cooling System (RVACS), utilization of high porosity porous bodies have been proposed by the last report. This report describe the experimental results to evaluate heat transfer performance of the porous bodies and to estimate the extrapolation to long heat transfer surface such as reactor scale. Following are typical results. (1) Usually the Heat Transfer coefficient at the lower reaches is smoller than that of the upper reaches. But Using with the high porosity porous bodies, the Heat Transfer coefficient at the lower reaches remains a constant value against distance from entrance point or a increase slightly compared to that of the upper reaches because of the effect of thermal radiation. (2) From the results of Heat Transfer coefficients against distance from the entrance point, the increasing ratio of enhancement of heat removal in the case of reactor scale is about 1.3. (author)
Nucleate boiling heat transfer on horizontal tubes in bundles
International Nuclear Information System (INIS)
Fujital, Y.; Ohta, H.; Hidaka, S.; Nishikawa, K.
1986-01-01
In order to clarify the heat transfer mechanisms of the flooded type horizontal tube bundle evaporator, heat transfer characteristics of tube bundles of experimental scale which consist both of smooth and enhanced tubes were investigated in detail. The experiments of saturated nucleate boiling were performed by using Freon 113 under pressures 0.1 to 1 MPa, and the effects of various parameters, for example, bundle arrangement, heat flux, pressure on the characteristics of an individual tube are clarified. Experimental data is reproduced well by a proposed heat transfer model in which convective heat transfer coefficients due to rising bubbles are estimated as a function of their volumetric flow rate
Heat transfer assembly for a fluorescent lamp and fixture
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.
International Nuclear Information System (INIS)
Sheng, Shiqi; Tu, Z C
2013-01-01
A unified χ-criterion for heat devices (including heat engines and refrigerators), which is defined as the product of the energy conversion efficiency and the heat absorbed per unit time by the working substance (de Tomás et al 2012 Phys. Rev. E 85 010104), is optimized for tight-coupling heat engines and refrigerators operating between two heat baths at temperatures T c and T h ( > T c ). By taking a new convention on the thermodynamic flux related to the heat transfer between two baths, we find that for a refrigerator tightly and symmetrically coupled with two heat baths, the coefficient of performance (i.e., the energy conversion efficiency of refrigerators) at maximum χ asymptotically approaches √(ε C ) when the relative temperature difference between two heat baths ε C -1 ≡(T h -T c )/T c is sufficiently small. Correspondingly, the efficiency at maximum χ (equivalent to maximum power) for a heat engine tightly and symmetrically coupled with two heat baths is proved to be η C /2+η C 2 /8 up to the second order term of η C ≡ (T h − T c )/T h , which reverts to the universal efficiency at maximum power for tight-coupling heat engines operating between two heat baths at small temperature difference in the presence of left–right symmetry (Esposito et al 2009 Phys. Rev. Lett. 102 130602). (fast track communication)
Numerical simulation of fluid flow and heat transfer in a concentric tube heat exchanger
International Nuclear Information System (INIS)
Mokamati, S.V.; Prasad, R.C.
2003-01-01
In this paper, numerical simulation of a concentric tube heat exchanger is presented to determine the convective heat transfer coefficient and friction factor in a smooth tube. Increasing the convective heat transfer coefficient can increase heat transfer rate in a concentric tube heat exchanger from a given tubular surface area. This can be achieved by using heat transfer augmentation devices. This work constitutes the initial phase of the numerical simulation of heat transfer from tubes employing augmentation devices, such as twisted tapes, wire-coil inserts, for heat transfer enhancement. A computational fluid dynamics (CFD) simulation tool was developed with CFX software and the results obtained from the simulations are validated with the empirical correlations for a smooth tube heat exchanger. The difficulties associated with the simulation of a heat exchanger augmented with wire-coil inserts are discussed. (author)
On the heat transfer correlation for membrane distillation
International Nuclear Information System (INIS)
Wang, Chi-Chuan
2011-01-01
Research highlights: → Heat transfer coefficients applicable for membrane distillation. → Data reduction for heat transfer coefficient for membrane distillation method. → Uncertainty of permeate side due to large magnitude of membrane resistance. → Increase accuracy of heat transfer coefficient by modified Wilson plot technique. -- Abstract: The present study examines the heat transfer coefficients applicable for membrane distillation. In the available literatures, researchers often adopt some existing correlations and claim the suitability of these correlations to their test data or models. Unfortunately this approach is quite limited and questionable. This is subject to the influences of boundary conditions, geometrical configurations, entry flow conditions, as well as some influences from spacer or support. The simple way is to obtain the heat transfer coefficients from experimentation. However there is no direct experimental data for heat transfer coefficients being reported directly from the measurements. The main reasons are from the uncertainty of permeate side and of the comparatively large magnitude of membrane resistance. Additional minor influence is the effect of mass transfer on the heat transfer performance. In practice, the mass transfer effect is negligible provided the feed side temperature is low. To increase the accuracy of the measured feed side heat transfer coefficient, it is proposed in this study to exploit a modified Wilson plot technique. Through this approach, one can eliminate the uncertainty from permeate side and reduce the uncertainty in membrane to obtain a more reliable heat transfer coefficients at feed side from the experimentation.
Review of PCMS and heat transfer enhancement methods applied ...
African Journals Online (AJOL)
Most available PCMs have low thermal conductivity making heat transfer enhancement necessary for power applications. The various methods of heat transfer enhancement in latent heat storage systems were also reviewed systematically. The review showed that three commercially - available PCMs are suitable in the ...
Measurement of heat transfer coefficient using termoanemometry methods
Dančová, P.; Sitek, P.; Vít, T.
2014-03-01
This work deals with a measurement of heat transfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heat transfer coefficient (HTC) is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.
Measurement of heat transfer coefficient using termoanemometry methods
Directory of Open Access Journals (Sweden)
Dančová P.
2014-03-01
Full Text Available This work deals with a measurement of heat transfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heat transfer coefficient (HTC is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.
Heat or mass transfer from an open cavity
Kuiken, H.K.
1978-01-01
This paper presents a mathematical model for heat or mass transfer from an open cavity. It is assumed that the Péclet number, based on conditions at the cavity, and the Prandtl number are both large. The model assumes heat- or mass-transfer boundary layers at the rim of the cavity vortex flow. Heat
Heat transfer enhancement with condensation by surface rotation
Energy Technology Data Exchange (ETDEWEB)
Vasiliev, L L; Khrolenok, V V [A.V. Luikov Heat and Mass Transfer Inst., Minsk (Belarus)
1993-11-01
Process intensification relies on many unit operations on enhanced heat transfer. One technique for the enhancement of condensation heat transfer is the use of surface rotation. This is particularly effective in reducing the condensate film thickness. The formulae and relationships given in this paper are concerned with rotating discs and tubes, and can be used for developing advanced heat exchanger concepts. (Author)
Heat transfer enhancement for fin-tube heat exchanger using vortex generators
International Nuclear Information System (INIS)
Yoo, Seong Yeon; Park, Dong Seong; Chung, Min Ho; Lee, Sang Yun
2002-01-01
Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin-circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of fin-flat tube heat exchanger without vortex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger. At the same time, pressure losses for four types of heat exchanger is measured and compared
34th UIT Heat Transfer Conference 2016
International Nuclear Information System (INIS)
2017-01-01
The annual UIT Heat Transfer Conference of the “Unione Italiana di Termofluidodinamica” aims at promoting cooperation in the field of heat transfer and thermal sciences, by bringing together scientists and engineers working in related areas. Several issues of interest are addressed, namely natural, forced and mixed convection, conduction, radiation, multi-phase fluid dynamics and interface phenomena, computational fluid dynamics, micro- and nano-scales, efficiency in energy systems, environmental technologies and buildings, heat transfer in fire engineering. The 34th UIT Conference was held in Ferrara (FE), Italy, 4–6 July, 2015 in the spaces of the Scientific and Technological Center of The University of Ferrara. The response has been enthusiastic: 61 abstracts, 36 oral and 18 poster presentations, 48 papers published on the Proceedings To encourage the debate, the Conference Program has scheduled ample poster sessions and invited lectures from the best experts in the field along with a few of the most talented researchers. Keynote Lectures were given by Professor Giovanni S. Barozzi (University of Modena), Professor Paolo Di Marco (University of Pisa) and Professor Nicola Bianco (University of Napoli Federico II). This special volume collects a selection of the scientific contributions discussed during this conference; these works give a good overview of the state-of-the art Italian research in the field of Heat Transfer related topics. I would like to thank sincerely the authors for presenting their works at the conference and in this special issue. I would also like to extend my thanks to the Scientific Committee and the authors for their accurate review process of each paper for this special issue. Special thanks go to the organizing committee. Professor Stefano Piva (president of The Organizing Committee) About UIT (Unione Italiana Termofluidodinamica) The Italian Union of Thermal-Fluid Dynamics (UIT) was founded in Bologna on December 19, 1984
Loop heat pipes - highly efficient heat-transfer devices for systems of sun heat supply
Energy Technology Data Exchange (ETDEWEB)
Maydanik, Yu. [Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Thermophysics
2004-07-01
Loop heat pipes (LHPs) are hermetic heat-transfer devices operating on a closed evaporation-condensation cycle with the use of capillary pressure for pumping the working fluid [1]. In accordance with this, they possess all the main advantages of conventional heat pipes, but, as distinct from the latter, have a considerably higher heat-transfer capacity, especially when operating in the ''antigravity'' regime, when heat is transferred from above downwards. Besides, LHPs possess a higher functional versatility, are adaptable to different operating conditions and provide great scope for various design embodiments. This is achieved at the expense of both the original design of the device and the properties of the wick - a special capillary structure used for the creation of capillary pressure. The LHP schematic diagram is given in Fig. 1. The device contains an evaporator and a condenser - heat exchanger connected by means of smooth-walled pipe-lines with a relatively small diameter intended for separate motion of vapor and liquid. At present loop heat pipes are most extensively employed in thermoregulation systems of spacecrafts. Miniature LHPs are used for cooling electronics and computers. At the same time there exists a considerable potential of using these devices for the recovery of low-grade (waste) heat from different sources, and also in systems of sun heat supply. In the latter case LHPs may serve as an efficient heat-transfer link between a sun collector and a heat accumulator, which has a low thermal resistance and does not consume any additional energy for pumping the working fluid between them. (orig.)
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers
de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries
2014-01-01
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
Interfacial heat transfer - State of the art
International Nuclear Information System (INIS)
Yadigaroglu, G.
1987-01-01
Interfacial heat exchanges control the interfacial mass exchange rate, depend on the interfacial area, and are tied to the prediction of thermal nonequilibrium. The nature of the problem usually requires the formulation of mechanistic laws and precludes the general use of universal correlations. This is partly due to the fact that the length scale controlling the interfacial exchanges varies widely from one situation to another and has a strong influence on the exchange coefficients. Within the framework of the ''two-fluid models'', the exchanges occurring at the interfaces are explicitly taken into consideration by the jump condition linking the volumetric mass exchange (evaporation) rate between the phases, to the interfacial energy transfer rates
FILM-30: A Heat Transfer Properties Code for Water Coolant
International Nuclear Information System (INIS)
MARSHALL, THERON D.
2001-01-01
A FORTRAN computer code has been written to calculate the heat transfer properties at the wetted perimeter of a coolant channel when provided the bulk water conditions. This computer code is titled FILM-30 and the code calculates its heat transfer properties by using the following correlations: (1) Sieder-Tate: forced convection, (2) Bergles-Rohsenow: onset to nucleate boiling, (3) Bergles-Rohsenow: partially developed nucleate boiling, (4) Araki: fully developed nucleate boiling, (5) Tong-75: critical heat flux (CHF), and (6) Marshall-98: transition boiling. FILM-30 produces output files that provide the heat flux and heat transfer coefficient at the wetted perimeter as a function of temperature. To validate FILM-30, the calculated heat transfer properties were used in finite element analyses to predict internal temperatures for a water-cooled copper mockup under one-sided heating from a rastered electron beam. These predicted temperatures were compared with the measured temperatures from the author's 1994 and 1998 heat transfer experiments. There was excellent agreement between the predicted and experimentally measured temperatures, which confirmed the accuracy of FILM-30 within the experimental range of the tests. FILM-30 can accurately predict the CHF and transition boiling regimes, which is an important advantage over current heat transfer codes. Consequently, FILM-30 is ideal for predicting heat transfer properties for applications that feature high heat fluxes produced by one-sided heating
Separate effects tests for GOTHIC condensation and evaporative heat transfer models
International Nuclear Information System (INIS)
George, T.L.; Singh, A.
1994-01-01
The GOTHIC computer program, under development at EPRI/NAI, is a general purpose thermal hydraulics computer program for design, licensing, safety and operating analysis of nuclear containments and other confinement buildings. The code solves a nine equation model for three dimensional multiphase flow with separate mass, momentum and energy equations for vapor, liquid and drop phases. The vapor phase can be a gas mixture of steam and non-condensing gases. The phase balance equations are coupled by mechanistic and empirical models for interface mass, energy and momentum transfer that cover the entire flow regime from bubbly flow to film/drop flow. A variety of heat transfer correlations are available to model the fluid coupling to active and passive solid conductors. This paper focuses on the application of GOTHIC to two separate effects tests; condensation heat transfer on a vertical flat plate with varying bulk velocity, steam concentration and temperature, and evaporative heat transfer from a hot pool to a dry (superheated) atmosphere. Comparisons with experimental data is included for both tests. Results show the validity of two condensation heat transfer correlations as incorporated into GOTHIC and the interfacial heat and mass transfer models for the range of the experimental test conditions. Comparisons are also made for lumped versus multidimensional modeling for buoyancy controlled flow with evaporative heat transfer. (author). 13 refs., 1 tab., 10 figs
Separate effects tests for GOTHIC condensation and evaporative heat transfer models
International Nuclear Information System (INIS)
George, T.L.; Singh, A.
1996-01-01
The GOTHIC computer program, under development at NAI for EPRI, is a general purpose thermal hydraulics computer program for design, licensing, safety and operating analysis of nuclear containments and other confinement buildings. The code solves a nine-equation model for three-dimensional multiphase flow with separate mass, momentum and energy equations for vapor, liquid and drop phases. The vapor phase can be a gas mixture of steam and non-condensing gases. The phase balance equations are coupled by mechanistic and empirical models for interface mass, energy and momentum transfer that cover the entire flow regime from bubbly flow to film-drop flow. A variety of heat transfer correlations are available to model the fluid coupling to active and passive solid conductors. This paper focuses on the application of GOTHIC to two separate effects tests: condensation heat transfer on a vertical flat plate with varying bulk velocity, steam concentration and temperature, and evaporative heat transfer from a hot pool to a dry (superheated) atmosphere. Comparisons with experimental data are included for both tests. Results show the validity of two condensation heat transfer correlations as incorporated into GOTHIC and the interfacial heat and mass transfer models for the range of the experimental test conditions. Comparisons are also made for lumped vs. multidimensional modeling for buoyancy-controlled flow with evaporative heat transfer. (orig.)
Corrosion of heat exchanger materials under heat transfer conditions
International Nuclear Information System (INIS)
Tapping, R.L.; Lavoie, P.A.; Disney, D.J.
1987-01-01
Severe pitting has occurred in moderator heat exchangers tubed with Incoloy-800 in Pickering Nuclear Generating Station. The pitting originated on the cooling side (outside) of the tubes and perforation occurred in less than two years. It was known from corrosion testing at CRNL that Incoloy-800 was not susceptible to pitting in Lake Ontario water under isothermal conditions. Corrosion testing with heat transfer across the tube wall was carried out, and it was noted that severe pitting could occur under deposits formed on the tubes in silty Lake Ontario water. Subsequent testing, carried out in co-operation with Ontario Hydro Research Division, investigated the pitting resistance of other candidate tubing alloys: Incoloy-825, 904 L stainless steel, AL-6X, Inconel-625, 70:30 Cu:Ni, titanium, Sanicro-30 and Sanicro-28 1 . Of these, only titanium and Sanicro-28 have not suffered some degree of pitting attack in silt-containing Lake Ontario Water. In the absence of silt, and hence deposits, no pitting took place on any of the alloys tested
A Heat Transfer Model for a Stratified Corium-Metal Pool in the Lower Plenum of a Nuclear Reactor
International Nuclear Information System (INIS)
Sohal, M.S.; Siefken, L.J.
1999-01-01
This preliminary design report describes a model for heat transfer in a corium-metal stratified pool. It was decided to make use of the existing COUPLE model. Currently available correlations for natural convection heat transfer in a pool with and without internal heat generation were obtained. The appropriate correlations will be incorporated in the existing COUPLE model. Heat conduction and solidification modeling will be done with existing algorithms in the COUPLE. Assessment of the new model will be done by simple energy conservation problems
Influence of short heat pulses on the helium boiling heat transfer rate
International Nuclear Information System (INIS)
Andreev, V.K.; Deev, V.I.; Savin, A.N.; Kutsenko, K.V.
1987-01-01
Investigation results on heat transfer in the process of helium boiling on a heated wall under conditions of pulsed heat effect are described. Results of the given study point to one of possible ways of heat exchange intensification in boiling helium by supplying short heat pulse to the heater. Even short-time noncontrolled or incidental increase in the heater capacity during experiment with boiling helium can result in a considerable disagreement of experimental data on heat transfer
Personalized recommendation based on heat bidirectional transfer
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.
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.
On the heat transfer in packed beds
International Nuclear Information System (INIS)
Sordon, G.
1988-09-01
The design of a fusion reactor blanket concept based on a bed of lithium containing ceramic pebbles or a mixture of ceramic and beryllium pebbles demands the knowledge of the effective thermal conductivity of pebble beds, including beds formed by a binary mixture of high conducting metallic pebbles and poorly conducting pebbles. In this work, binary mixtures of spheres of same diameter and different conductivities as well as beds formed by one type of spheres were investigated. The experimental apparatus consists of a stainless steel cylinder with a heating rod along the symmetry axis. Experiments with stagnant and flowing gas were performed. The pebbles were of Al 2 O 3 (diameter = 1, 2, 4 mm), of Li 4 SO 4 (diameter = 0.5 mm) of Al (diameter = 2 mm) and of steel (diameter = 2, 4 mm). Experimental values of the thermal conductivity and of the wall heat transfer coefficient are compared with the predicted ones. Modifications of already existing models were suggested. (orig.) [de
TACO: a finite element heat transfer code
International Nuclear Information System (INIS)
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
Supercritical water gasification with decoupled pressure and heat transfer modules
Dibble, Robert W.; Ng, Kim Choon; Sarathy, Mani
2017-01-01
decouples the function of containing high pressure from the high temperature function. The present invention allows the heat transfer function to be conducted independently from the pressure transfer function such that the system equipment can be designed
Analysis of heat transfer in plain carbon steels
International Nuclear Information System (INIS)
Han, Heung Nam; Lee, Kyung Jong
1999-01-01
During cooling of steels, the heat transfer was controlled by radiation, convection, conduction and heat evolution from phase transformation. To analyze the heat transfer during cooling precisely, the material constants such as density, heat capacity and the heat evolved during transformation were obtained as functions of temperature and chemical composition for each phase observed in plain carbon steel using a thermodynamic analysis based on the sublattice model of Fe-C-Mn system. The results were applied to 0.049 wt% and 0.155 wt% carbon steels with an austenitic stainless steel as reference by developing a proper heat transfer governing equation. The equation was solved using the lumped system method. In addition, using a transformation dilatometer with adequate experimental conditions to clarify the individual heat transfer effect, the transformation heat evolved during cooling and the transformation behavior as well as the temperature change were observed. The predicted temperature profiles during cooling were well agreed with the measured ones
Analysis of the heat transfer in double and triple concentric tube heat exchangers
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.
Influence of radiation heat transfer during a severe accident
Energy Technology Data Exchange (ETDEWEB)
Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Ciudad de Mexico (Mexico); Polo L, M. A., E-mail: ricardo-cazares@hotmail.com [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Barragan No. 779, Col. Narvarte, 03020 Ciudad de Mexico (Mexico)
2016-09-15
The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)
Heat Transfer Modelling of Glass Media within TPV Systems
Bauer, Thomas; Forbes, Ian; Penlington, Roger; Pearsall, Nicola
2004-11-01
Understanding and optimisation of heat transfer, and in particular radiative heat transfer in terms of spectral, angular and spatial radiation distributions is important to achieve high system efficiencies and high electrical power densities for thermophtovoltaics (TPV). This work reviews heat transfer models and uses the Discrete Ordinates method. Firstly one-dimensional heat transfer in fused silica (quartz glass) shields was examined for the common arrangement, radiator-air-glass-air-PV cell. It has been concluded that an alternative arrangement radiator-glass-air-PV cell with increased thickness of fused silica should have advantages in terms of improved transmission of convertible radiation and enhanced suppression of non-convertible radiation.
Influence of radiation heat transfer during a severe accident
International Nuclear Information System (INIS)
Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A.; Polo L, M. A.
2016-09-01
The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)
An introduction to heat transfer principles and calculations
Ede, A J; Ower, E
1967-01-01
An Introduction to Heat Transfer Principles and Calculations is an introductory text to the principles and calculations of heat transfer. The theory underlying heat transfer is described, and the principal results and formulae are presented. Available techniques for obtaining rapid, approximate solutions to complicated problems are also considered. This book is comprised of 12 chapters and begins with a brief account of some of the concepts, methods, nomenclature, and other relevant information about heat transfer. The reader is then introduced to radiation, conduction, convection, and boiling
A study on the heat transfer characteristics of a self-oscillating heat pipe
International Nuclear Information System (INIS)
Yoon, Seok Hun; Oh, Cheol; Choi, Jae Hyuk
2002-01-01
In this paper, the heat transfer characteristics of a self-oscillating heat pipe are experimentally investigated for the effect of various working fluid fill charge ratios and heat loads. The characteristics of temperature oscillations of the working fluid are also analysed based on chaotic dynamics. The heat pipe is composed of a heating section, a cooling section and an adiabatic section, and has a 0.002m internal diameter, a 0.34m length in each turn and consists of 19 turns. The heating and the cooling portion of each turn has a length of 70mm. A series of experiments was carried out to measure the temperature distributions and the pressure variations of the heat pipe. Furthermore, heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients are calculated for various operating conditions. Experimental results show the efficacy of this type of heat pipe
Neutron behavior, reactor control, and reactor heat transfer. Volume four
International Nuclear Information System (INIS)
Anon.
1986-01-01
Volume four covers neutron behavior (neutron absorption, how big are nuclei, neutron slowing down, neutron losses, the self-sustaining reactor), reactor control (what is controlled in a reactor, controlling neutron population, is it easy to control a reactor, range of reactor control, what happens when the fuel burns up, controlling a PWR, controlling a BWR, inherent safety of reactors), and reactor heat transfer (heat generation in a nuclear reactor, how is heat removed from a reactor core, heat transfer rate, heat transfer properties of the reactor coolant)
INTENSIFICATION OF HEAT- AND MASS TRANSFER IN EVAPORATION - CONDENSATION DEVICES
Directory of Open Access Journals (Sweden)
A. G. Kulakov
2005-01-01
Full Text Available Results of investigation of capillary structure properties used in evaporation – condensation devices are presented.Constructive solutions for intensification of heat transfer in evaporation and condensation heat exchangers are offered. The obtained heat transfer experimental data at film-type vapor conden-sation are generalized in criterion form.Description of general rule of heat and mass transfer processes in miniature heat pipes with three various capillary structures at wide range of operating parameters is given in the paper.
International Nuclear Information System (INIS)
Banerjee, S.; Hassan, Y.A.
1995-01-01
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
Energy Technology Data Exchange (ETDEWEB)
Banerjee, S.; Hassan, Y.A. [Texas A& M Univ., College Station, TX (United States)
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.
Non intrusive measurement of the convective heat transfer coefficient
Energy Technology Data Exchange (ETDEWEB)
Rebay, M.; Mebarki, G.; Padet, J. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Arfaoui, A. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM; Maad, B.R. [Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM
2010-07-01
The efficiency of cooling methods in thermal systems such as radiators and heat exchangers must be improved in order to enhance performance. The evaluation of the heat transfer coefficients between a solid and a fluid is necessary for the control and the dimensioning of thermal systems. In this study, the pulsed photothermal method was used to measure the convective heat transfer coefficient on a solid-fluid interface, notably between an air flow and a heated slab mounted on a PVC flat plate. This configuration simulated the electronic air-cooling inside enclosures and racks. The influence of the deflector's inclination angle on the enhancement of heat transfer was investigated using 2 newly developed identification models. The first model was based on a constant heat transfer coefficient during the pulsed experiment, while the second, improved model was based on a variable heat transfer coefficient. The heat transfer coefficient was deduced from the evolution of the transient temperature induced by a sudden deposit of a luminous energy on the front face of the slab. Temperature evolutions were derived by infrared thermography, a camera for cartography and a detector for precise measurement in specific locations. The results show the improvement of measurement accuracies when using a model that considers the temporal evolution of the convective heat transfer coefficient. The deflection of air flow on the upper surface of the heated slab demonstrated better cooling of the slab by the deflection of air flow. 11 refs., 1 tab., 8 figs.
Surface wettability and subcooling on nucleate pool boiling heat transfer
Suroto, Bambang Joko; Kohno, Masamichi; Takata, Yasuyuki
2018-02-01
The effect of varying surface wettabilities and subcooling on nucleate pool boiling heat transfer at intermediate heat flux has been examined and investigated. The experiments were performed using pure water as the working fluid and subcooling ranging from 0, 5 and 10 K, respectively. The three types of heat transfer block were used that are bare surface/hydrophilic (polished copper), superhydrophilic/TiO2-coated on copper and hydrophobic/PTFE surface. The experimental results will be examined by the existing model. The results show that the heat transfer performance of surfaces with PTFE coating is better at low heat flux. While for an intermediate heat flux, superhydrophilic surface (TiO2) is superior compared to hydrophilic and hydrophobic surfaces. It is observed that the heat transfer performance is decreasing when the sub cooling degree is increased.
Transfer coefficients for plate fin and elliptical tube heat exchangers
International Nuclear Information System (INIS)
Saboya, S.M.; Saboya, F.E.M.
1981-01-01
In order to determine transfer coefficients for plate fin and elliptical tube exchangers, mass transfer experiments have been performed using the naphthalene sublimation technique. By means of the heat-mass transfer analogy, the results can be converted to heat transfer results. The transfer coefficients were compared with those for circular tube exchangers and the comparison revealed no major differences. This is a positive outcome, since the use of elliptical tubes may reduce substantially the pressure drop, without affecting the transfer characteristics.(Author) [pt
Schuller, G.; Vázquez, F. Vidal; Waiblinger, W.; Auvinen, S.; Ribeirinha, P.
2017-04-01
In this work a methanol steam reforming (MSR) reactor has been operated thermally coupled to a high temperature polymer electrolyte fuel cell stack (HT-PEMFC) utilizing its waste heat. The operating temperature of the coupled system was 180 °C which is significantly lower than the conventional operating temperature of the MSR process which is around 250 °C. A newly designed heat exchanger reformer has been developed by VTT (Technical Research Center of Finland LTD) and was equipped with commercially available CuO/ZnO/Al2O3 (BASF RP-60) catalyst. The liquid cooled, 165 cm2, 12-cell stack used for the measurements was supplied by Serenergy A/S. The off-heat from the electrochemical fuel cell reaction was transferred to the reforming reactor using triethylene glycol (TEG) as heat transfer fluid. The system was operated up to 0.4 A cm-2 generating an electrical power output of 427 Wel. A total stack waste heat utilization of 86.4% was achieved. It has been shown that it is possible to transfer sufficient heat from the fuel cell stack to the liquid circuit in order to provide the needed amount for vaporizing and reforming of the methanol-water-mixture. Furthermore a set of recommendations is given for future system design considerations.
Experimental analysis of direct-expansion ground-coupled heat pump systems
Mei, V. C.; Baxter, V. D.
1991-09-01
Direct-expansion ground-coil-coupled (DXGC) heat pump systems have certain energy efficiency advantages over conventional ground-coupled heat pump (GCHP) systems. Principal among these advantages are that the secondary heat transfer fluid heat exchanger and circulating pump are eliminated. While the DXGC concept can produce higher efficiencies, it also produces more system design and environmental problems (e.g., compressor starting, oil return, possible ground pollution, and more refrigerant charging). Furthermore, general design guidelines for DXGC systems are not well documented. A two-pronged approach was adopted for this study: (1) a literature survey, and (2) a laboratory study of a DXGC heat pump system with R-22 as the refrigerant, for both heating and cooling mode tests done in parallel and series tube connections. The results of each task are described in this paper. A set of general design guidelines was derived from the test results and is also presented.
An analytical solution to the heat transfer problem in thick-walled hunt flow
International Nuclear Information System (INIS)
Bluck, Michael J; Wolfendale, Michael J
2017-01-01
Highlights: • Convective heat transfer in Hunt type flow of a liquid metal in a rectangular duct. • Analytical solution to the H1 constant peripheral temperature in a rectangular duct. • New H1 result demonstrating the enhancement of heat transfer due to flow distortion by the applied magnetic field. • Analytical solution to the H2 constant peripheral heat flux in a rectangular duct. • New H2 result demonstrating the reduction of heat transfer due to flow distortion by the applied magnetic field. • Results are important for validation of CFD in magnetohydrodynamics and for implementation of systems code approaches. - Abstract: The flow of a liquid metal in a rectangular duct, subject to a strong transverse magnetic field is of interest in a number of applications. An important application of such flows is in the context of coolants in fusion reactors, where heat is transferred to a lead-lithium eutectic. It is vital, therefore, that the heat transfer mechanisms are understood. Forced convection heat transfer is strongly dependent on the flow profile. In the hydrodynamic case, Nusselt numbers and the like, have long been well characterised in duct geometries. In the case of liquid metals in strong magnetic fields (magnetohydrodynamics), the flow profiles are very different and one can expect a concomitant effect on convective heat transfer. For fully developed laminar flows, the magnetohydrodynamic problem can be characterised in terms of two coupled partial differential equations. The problem of heat transfer for perfectly electrically insulating boundaries (Shercliff case) has been studied previously (Bluck et al., 2015). In this paper, we demonstrate corresponding analytical solutions for the case of conducting hartmann walls of arbitrary thickness. The flow is very different from the Shercliff case, exhibiting jets near the side walls and core flow suppression which have profound effects on heat transfer.
Capillary Pumped Heat Transfer (CHT) Experiment
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.
International Nuclear Information System (INIS)
Cheng, XueTao; Liang, XinGang
2013-01-01
The entropy generation minimization method is often used to analyze heat transfer processes from the thermodynamic viewpoint. In this paper, we analyze common heat transfer processes with the concept of entropy generation, and propose the concept of heat transfer entropy resistance. It is found that smaller heat transfer entropy resistance leads to smaller equivalent thermodynamic force difference with prescribed heat transfer rate and larger heat transfer rate with prescribed equivalent thermodynamic force difference. With the concept of heat transfer entropy resistance, the performance of two-stream heat exchangers (THEs) and two-stream heat exchanger networks (THENs) is analyzed. For the cases discussed in this paper, it is found that smaller heat transfer entropy resistance always leads to better heat transfer performance for THEs and THENs, while smaller values of the entropy generation, entropy generation numbers and revised entropy generation number do not always. -- Highlights: • The concept of entropy resistance is defined. • The minimum entropy resistance principle is developed. • Smaller entropy resistance leads to better heat transfer
Fluid flow and heat transfer modeling for castings
International Nuclear Information System (INIS)
Domanus, H.M.; Liu, Y.Y.; Sha, W.T.
1986-01-01
Casting is fundamental to manufacturing of many types of equipment and products. Although casting is a very old technology that has been in existence for hundreds of years, it remains a highly empirical technology, and production of new castings requires an expensive and time-consuming trial-and-error approach. In recent years, mathematical modeling of casting has received increasing attention; however, a majority of the modeling work has been in the area of heat transfer and solidification. Very little work has been done in modeling fluid flow of the liquid melt. This paper presents a model of fluid flow coupled with heat transfer of a liquid melt for casting processes. The model to be described in this paper is an extension of the COMMIX code and is capable of handling castings with any shape, size, and material. A feature of this model is the ability to track the liquid/gas interface and liquid/solid interface. The flow of liquid melt through the sprue and runners and into the mold cavity is calculated as well as three-dimensional temperature and velocity distributions of the liquid melt throughout the casting process. 14 refs., 13 figs
Heat transfer analysis of parabolic trough solar receiver
International Nuclear Information System (INIS)
Padilla, Ricardo Vasquez; Demirkaya, Gokmen; Goswami, D. Yogi; Stefanakos, Elias; Rahman, Muhammad M.
2011-01-01
Highlights: → In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. → The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. → Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented. → The proposed heat transfer model was validated with experimental data obtained from Sandia National Laboratory. → Our results showed a better agreement with experimental data compared to other models. -- Abstract: Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures. A heat transfer fluid circulates through a metal tube (receiver) with an external selective surface that absorbs solar radiation reflected from the mirror surfaces of the PTC. In order to reduce the heat losses, the receiver is covered by an envelope and the enclosure is usually kept under vacuum pressure. The heat transfer and optical analysis of the PTC is essential to optimize and understand its performance under different operating conditions. In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented as well. The partial differential equations were discretized and the nonlinear algebraic equations were solved simultaneously. Finally, to validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL) and other one dimensional heat transfer models. Our results showed a better agreement with experimental data compared to other models.
Heat transfer in a one-dimensional mixed convection loop
International Nuclear Information System (INIS)
Kim, Min Joon; Lee, Yong Bum; Kim, Yong Kyun; Kim, Jong Man; Nam, Ho Yun
1999-01-01
Effects of non-uniform heating in the core and additional forced circulation during decay heat removal operation are studied with a simplified mixed convection loop. The heat transfer coefficient is calculated analytically and measured experimentally. The analytic solution obtained from a one-dimensional heat equation is found to agree well with the experimental results. The effects of the non-uniform heating and the forced circulation are discussed
Improving Heat Transfer Performance of Printed Circuit Boards
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.
An inverse heat transfer problem for optimization of the thermal ...
Indian Academy of Sciences (India)
This paper takes a different approach towards identiﬁcation of the thermal process in machining, using inverse heat transfer problem. Inverse heat transfer method allows the closest possible experimental and analytical approximation of thermal state for a machining process. Based on a temperature measured at any point ...
Transient heat transfer in longitudinal fins of various profiles with ...
Indian Academy of Sciences (India)
Transient heat transfer through a longitudinal ﬁn of various proﬁles is studied. The thermal conductivity and heat transfer coefficients are assumed to be temperature dependent. The resulting partial differential equation is highly nonlinear. Classical Lie point symmetry methods are employed and some reductions are ...
Heat transfer and thermal stress analysis in grooved tubes
Indian Academy of Sciences (India)
Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was ...
Analytical Evalution of Heat Transfer Conductivity with Variable Properties
DEFF Research Database (Denmark)
Rahimi, Masoume; Hosseini, Mohammad Javad; Barari, Amin
2011-01-01
The homotopy analysis method (HAM) as a new technique which is powerful and easy-to-use, is applied to solve heat transfer problems. In this paper, we use HAM for heat transfer conductivity equation with variable properties which may contain highly nonlinear terms. The obtained results are also...
Two dimensional finite element heat transfer models for softwood
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...
Heat transfer in high-level waste management
International Nuclear Information System (INIS)
Dickey, B.R.; Hogg, G.W.
1979-01-01
Heat transfer in the storage of high-level liquid wastes, calcining of radioactive wastes, and storage of solidified wastes are discussed. Processing and storage experience at the Idaho Chemical Processing Plant are summarized for defense high-level wastes; heat transfer in power reactor high-level waste processing and storage is also discussed
Enhancement of heat transfer using varying width twisted tape inserts
African Journals Online (AJOL)
user
enhancement of heat transfer with twisted tape inserts as compared to plain ... studies for heat transfer and pressure drop of laminar flow in horizontal tubes ... flow in rectangular and square plain ducts and ducts with twisted-tape inserts .... presence of the insert in the pipe causes resistance to flow and increases turbulence.
Analysis of heat transfer in a centrifugal film evaporator
Bruin, S.
1970-01-01
Heat transfer in a centrifugal film evaporator with a conical heating surface is analyzed. Two regions of transfer can be distinguished: an entrance region, where the temp. profile in the film develops, and an evapn. region, where \\"surface evapn.\\" takes place. Relations are derived for liq.-film
A modified stanton number for heat transfer through fabric surface
Directory of Open Access Journals (Sweden)
Zhang Shen-Zhong
2015-01-01
Full Text Available The Stanton number was originally proposed for describing heat transfer through a smooth surface. A modified one is suggested in this paper to take into account non-smooth surface or fractal surface. The emphasis is put on the heat transfer through fabrics.
THE ELECTRONIC COURSE OF HEAT AND MASS TRANSFER
Directory of Open Access Journals (Sweden)
Alexander P. Solodov
2013-01-01
Full Text Available The Electronic course of heat and mass transfer in power engineering is presented containing the full Electronic book as the structured hypertext document, the full set of Mathcad-documents with the whole set of educative computer models of heat and mass transfer, the computer labs, and selected educational presentations.
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
1996-12-31
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J I; Rodriques, R Jr [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
1997-12-31
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
Effect of surface etching on condensing heat transfer
Energy Technology Data Exchange (ETDEWEB)
Seok, Sung Chul; Park, Jae Won; Jung, Jiyeon; Choi, Chonggun; Choi, Gyu Hong; Hwang, Seung Sik; Chung, Tae Yong; Shin, Donghoon [Kookmin University, Seoul (Korea, Republic of); Kim, Jin Jun [Hoseo University, Asan (Korea, Republic of)
2016-02-15
This study conducted experiments on humid air condensation during heat transfer in an air preheating exchanger attached to a home condensing boiler to improve thermal efficiency. An etchant composed of sulfuric acid and sodium nitrate was used to create roughness on the heat exchanger surface made from STS430J1L. A counter flow heat exchanger was fabricated to test the performance of heat transfer. Results showed that the overall heat transfer coefficients of all specimens treated with etchant improved with respect to the original specimens (not treated with etchant), and the overall heat transfer coefficient of the 60 s etching specimen increased by up to 15%. However, the increasing rate of the heat transfer coefficient was disproportional to the etching time. When the etching time specifically increased above 60 s, the heat transfer coefficient decreased. This effect was assumed to be caused by surface characteristics such as contact angle. Furthermore, a smaller contact angle or higher hydrophilicity leads to higher heat transfer coefficient.
Proceedings of the 33rd national heat transfer conference NHTC'99
International Nuclear Information System (INIS)
Jensen, M.K.; Di Marzo, M.
1999-01-01
The papers in this conference were divided into the following sections: Radiation Heat Transfer in Fires; Computational Fluid Dynamics Methods in Two-Phase Flow; Heat Transfer in Microchannels; Thin Film Heat Transfer; Thermal Design of Electronics; Enhanced Heat Transfer I; Porous Media Convection; Contact Resistance Heat Transfer; Materials Processing in Solidification and Crystal Growth; Fundamentals of Combustion; Challenging Modeling Aspects of Radiative Transfer; Fundamentals of Microscale Transport; Laser Processing and Diagnostics for Manufacturing and Materials Processing; Experimental Studies of Multiphase Flow; Enhanced Heat Transfer II; Heat and Mass Transfer in Porous Media; Heat Transfer in Turbomachinery and Gas Turbine Systems; Conduction Heat Transfer; General Papers; Open Forum on Combustion; Combustion and Instrumentation and Diagnostics I; Radiative Heat Transfer and Interactions in Participating and Nonparticipating Media; Applications of Computational Heat Transfer; Heat Transfer and Fluid Aspects of Heat Exchangers; Two-Phase Flow and Heat Transfer Phenomena; Fundamentals of Natural and Mixed Convection Heat Transfer I; Fundamental of Natural and Mixed Convection Heat Transfer II; Combustion and Instrumentation and Diagnostics II; Computational Methods for Multidimensional Radiative Transfer; Process Heat Transfer; Advances in Computational Heat and Mass Transfer; Numerical Methods for Porous Media; Transport Phenomena in Manufacturing and Materials Processing; Practical Combustion; Melting and Solidification Heat Transfer; Transients in Dynamics of Two-Phase Flow; Basic Aspects of Two-Phase Flow; Turbulent Heat Transfer; Convective Heat Transfer in Electronics; Thermal Problems in Radioactive and Mixed Waste Management; and Transport Phenomena in Oscillatory Flows. Separate abstracts were prepared for most papers in this conference
Burnout detector design for heat transfer experiments
International Nuclear Information System (INIS)
Dias, H.F.
1992-01-01
This paper describes the design of an burnout detector for heat transfer experiments, applied during tests for optimization of fuel elements for PWR reactors. The burnout detector avoids the fuel rods destruction during the experiments at the Centro de Desenvolvimento da Tecnologia Nuclear. The detector evaluates the temperature changes over the fuel rods in the temperature changes over the fuel rods in the area where the burnout phenomenon could be anticipated. As soon as the phenomenon appears, the system power supply is turned off. The thermal Circuit No. 1, during the experiments, had been composed by nine fuel rods feed parallelly by the same power supply. Fine copper wires had been attached at the centre and at the ends of the fuel rod to take two Wheat stone bridge arms. The detector had been applied across the bridge diagonals, which must be balanced the burnout excursion can be detected as a small but fast increase of the signal over the detector. Large scale experiments had been carried out to compare the resistance bridge performance against a thermocouple attached through the fuel rod wall. These experiments had been showed us the advantages of the first method over the last, because the bridge evaluates the whole fuel rod, while the thermocouple evaluates only the area where it had been attached. (author)
Heat loss prediction of a confined premixed jet flame using a conjugate heat transfer approach
Gövert, S.; Mira, D.; Zavala-Ake, M.; Kok, J.B.W.; Vázquez, M.; Houzeaux, G.
2017-01-01
The presented work addresses the investigation of the heat loss of a confined turbulent jet flame in a lab-scale combustor using a conjugate-heat transfer approach and large-eddy simulation. The analysis includes the assessment of the principal mechanisms of heat transfer in this combustion chamber:
Heat transfer in the thermal entrance region of a circular tube with axial heat conduction
International Nuclear Information System (INIS)
Zhang Changquan.
1985-01-01
This paper recounts the effects of axial heat conduction and convective boundary conditions on the heat transfer in the thermal entrance region of a circular tube under uniform flow, and the corresponding calculation is made. It will be profitable for the heat transfer studies on the pipe entrance region of low Prandtl number (liquid metal), or flow of low Peclet number. (author)
2016-05-01
AFRL-RQ-WP-TR-2016-0108 SILICON CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled...CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled Heat Input to an Acceleration Field 5a...Shukla, K., “Thermo-fluid dynamics of Loop Heat Pipe Operation,” International Communications in Heat and Mass Transfer , Vol. 35, No. 8, 2008, pp
On Two-Scale Modelling of Heat and Mass Transfer
International Nuclear Information System (INIS)
Vala, J.; Stastnik, S.
2008-01-01
Modelling of macroscopic behaviour of materials, consisting of several layers or components, whose microscopic (at least stochastic) analysis is available, as well as (more general) simulation of non-local phenomena, complicated coupled processes, etc., requires both deeper understanding of physical principles and development of mathematical theories and software algorithms. Starting from the (relatively simple) example of phase transformation in substitutional alloys, this paper sketches the general formulation of a nonlinear system of partial differential equations of evolution for the heat and mass transfer (useful in mechanical and civil engineering, etc.), corresponding to conservation principles of thermodynamics, both at the micro- and at the macroscopic level, and suggests an algorithm for scale-bridging, based on the robust finite element techniques. Some existence and convergence questions, namely those based on the construction of sequences of Rothe and on the mathematical theory of two-scale convergence, are discussed together with references to useful generalizations, required by new technologies.
On Two-Scale Modelling of Heat and Mass Transfer
Vala, J.; Št'astník, S.
2008-09-01
Modelling of macroscopic behaviour of materials, consisting of several layers or components, whose microscopic (at least stochastic) analysis is available, as well as (more general) simulation of non-local phenomena, complicated coupled processes, etc., requires both deeper understanding of physical principles and development of mathematical theories and software algorithms. Starting from the (relatively simple) example of phase transformation in substitutional alloys, this paper sketches the general formulation of a nonlinear system of partial differential equations of evolution for the heat and mass transfer (useful in mechanical and civil engineering, etc.), corresponding to conservation principles of thermodynamics, both at the micro- and at the macroscopic level, and suggests an algorithm for scale-bridging, based on the robust finite element techniques. Some existence and convergence questions, namely those based on the construction of sequences of Rothe and on the mathematical theory of two-scale convergence, are discussed together with references to useful generalizations, required by new technologies.
Second Law Analysis in Convective Heat and Mass Transfer
Directory of Open Access Journals (Sweden)
A. Ben Brahim
2006-02-01
Full Text Available This paper reports the numerical determination of the entropy generation due to heat transfer, mass transfer and fluid friction in steady state for laminar double diffusive convection, in an inclined enclosure with heat and mass diffusive walls, by solving numerically the mass, momentum, species conservation and energy balance equations, using a Control Volume Finite-Element Method. The influences of the inclination angle, the thermal Grashof number and the buoyancy ratio on total entropy generation were investigated. The irreversibilities localization due to heat transfer, mass transfer and fluid friction is discussed for three inclination angles at a fixed thermal Grashof number.
Blowdown heat transfer surface in RELAP4/MOD6
International Nuclear Information System (INIS)
Nelson, R.A.; Sullivan, L.H.
1978-01-01
New heat transfer correlations for both PWR and BWR blowdowns have been implemented in the RELAP4/MOD6 program. The concept of a multidimensional surface is introduced with the heat flux from a given heat transfer correlation or correlations depicted as a mathematical surface that is dependent upon quality, wall superheat, mass flow and pressure. The heat transfer logic has been modularized to facilitate replacing boiling curves for future correlation data comparisons and investigations. To determine the validity of the blowdown surface, comparison has been performed using data from the Semiscale experimental facility. (author)
International Nuclear Information System (INIS)
Boyer, B.D.; Parlatan, Y.; Slovik, G.C.
1995-01-01
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 ±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
Energy Technology Data Exchange (ETDEWEB)
Boyer, B.D.; Parlatan, Y.; Slovik, G.C. [and others
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.
Wireless energy transfer through non-resonant magnetic coupling
DEFF Research Database (Denmark)
Peng, Liang; Breinbjerg, Olav; Mortensen, Asger
2010-01-01
could be properly designed to minimize undesired energy dissipation in the source coil when the power receiver is out of the range. Our basic observation paves the way for more flexible design and fabrication of non-resonant mid-range wireless energy transfer systems, thus potentially impacting......We demonstrate by theoretical analysis and experimental verification that mid-range wireless energy transfer systems may take advantage of de-tuned coupling devices, without jeopardizing the energy transfer efficiency. Allowing for a modest de-tuning of the source coil, energy transfer systems...... practical implementations of wireless energy transfer....
Heat transfer analysis of liquid piston compressor for hydrogen applications
DEFF Research Database (Denmark)
Kermani, Nasrin Arjomand; Rokni, Masoud
2015-01-01
A hydrogen compression technology using liquid as the compression piston is investigated from heat transfer point of view. A thermodynamic model, simulating a single compression stroke, is developed to investigate the heat transfer phenomena inside the compression chamber. The model is developed...... and through the walls, is investigated and compared with the adiabatic case. The results show that depending on heat transfer correlation, the hydrogen temperature reduces slightly between 0.2% and 0.4% compared to the adiabatic case, at 500bar, due to the large wall resistance and small contact area...... at the interface. Moreover, the results of the sensitivity analysis illustrates that increasing the total heat transfer coefficients at the interface and the wall, together with compression time, play key roles in reducing the hydrogen temperature. Increasing the total heat transfer coefficient at the interface...
Comparison of heat transfer models for reciprocating compressor
International Nuclear Information System (INIS)
Tuhovcak, J.; Hejcik, J.; Jicha, M.
2016-01-01
Highlights: • Comparison of integral heat transfer models. • Influence of heat transfer model on volumetric and isentropic efficiency. • Various gases used as working fluid. - Abstract: One of the main factors affecting the efficiency of reciprocating compressor is heat transfer inside the cylinder. An analysis of heat transfer could be done using numerical models or integral correlations developed mainly from approaches used in combustion engines; however their accuracy is not completely verified due to the complicated experimental set up. The goal of this paper is to analyse the effect of heat transfer on compressor efficiency. Various integral correlations were compared for different compressor settings and fluids. CoolProp library was used in the code to obtain the properties of common coolants and gases. A comparison was done using the in-house code developed in Matlab, based on 1st Law of Thermodynamics.
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo;
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.
Natural convection heat transfer from a vertical circular tube sheet
International Nuclear Information System (INIS)
Dharne, S.P.; Gaitonde, U.N.
1996-01-01
Experiments were conducted to determine natural convection heat transfer coefficients (a) on a plain vertical circular plate, and (b) on a similar plate with a square array of non-conducting tubes fixed in it. The experiments were carried out using air as the heat transfer medium. The diameter of the brass plates used was 350 mm. The diameter of the bakelite tubes used was 19.2 mm. The range of Rayleigh numbers was from 1.06x10 8 to 1.66x10 8 . The results show that the heat transfer coefficients in case (a) are very close to those obtained using standard correlations for vertical flat plates, whereas for case (b) the heat transfer coefficients are at least 50 percent higher than those predicted by the Churchill-Chu correlation. It is hence concluded that the disturbance to boundary layer caused by the presence of tubes enhances the heat transfer coefficient significantly. (author). 4 refs., 3 figs
Sensible Heat Transfer during Droplet Cooling: Experimental and Numerical Analysis
Directory of Open Access Journals (Sweden)
Emanuele Teodori
2017-06-01
Full Text Available This study presents the numerical reproduction of the entire surface temperature field resulting from a water droplet spreading on a heated surface, which is compared with experimental data. High-speed infrared thermography of the back side of the surface and high-speed images of the side view of the impinging droplet were used to infer on the solid surface temperature field and on droplet dynamics. Numerical reproduction of the phenomena was performed using OpenFOAM CFD toolbox. An enhanced volume of fluid (VOF model was further modified for this purpose. The proposed modifications include the coupling of temperature fields between the fluid and the solid regions, to account for transient heat conduction within the solid. The results evidence an extremely good agreement between the temporal evolution of the measured and simulated spreading factors of the considered droplet impacts. The numerical and experimental dimensionless surface temperature profiles within the solid surface and along the droplet radius, were also in good agreement. Most of the differences were within the experimental measurements uncertainty. The numerical results allowed relating the solid surface temperature profiles with the fluid flow. During spreading, liquid recirculation within the rim, leads to the appearance of different regions of heat transfer that can be correlated with the vorticity field within the droplet.
Non-Uniform Heat Transfer in Thermal Regenerators
DEFF Research Database (Denmark)
Jensen, Jesper Buch
, a numerical model, which simulates a single-blow operation in a parallel-plate regenerator, was developed and used to model the heat transfer under various conditions. In addition to the modeling of the heat transfer, a series of experiments on passive regenerators with non-uniform, but precisely controlled....... Additionally, the experiments gave real comparative results, whereas the model to a certain degree more served to provide insight to the heat transfer processes taking place inside the regenera- tors, something that would be - if not impossible - then highly impractical to do experimentally. It has been found......This thesis presents investigations on the heat transfer in complex heat ex- changers in general and in regenerative heat exchangers (regenerators) in par- ticular. The motivation for this work is a result of inconsistencies obeserved in the results from a series of experiments on active magnetic...
Direct contact heat transfer characteristics between melting alloy and water
International Nuclear Information System (INIS)
Kinoshita, Izumi; Nishi, Yoshihisa; Furuya, Masahiro
1995-01-01
As a candidate for an innovative steam generator for fast breeder reactors, a heat exchanger with direct contact heat transfer between melting alloy and water was proposed. The evaluation of heat transfer characteristics of this heat exchanger is one of the research subjects for the design and development of the steam generator. In this study, the effect of the pressure on heat transfer characteristics and the required degree of superheating of melting alloy above water saturation temperature are evaluated during the direct contact heat transfer experiment by injecting water into Wood's alloy. In the experiment, the pressure, the temperature of the Wood's alloy, the flow rate of feed water, and the depth of the feed water injection point are varied as parameters. As a result of the experiment, the product of the degree of Wood's alloy superheating above water saturation temperature and the depth of the feed water injection point is constant for each pressure. This constant increases as the pressure rises. (author)
Numerical investigation of heat transfer effects in small wave rotor
International Nuclear Information System (INIS)
Deng, Shi; Okamoto, Koji; Teramoto, Susumu
2015-01-01
Although a wave rotor is expected to enhance the performance of the ultra-micro gas turbine, the device itself may be affected by downsizing. Apart from the immediate effect of viscosity on flow dynamics when downscaled, the effects of heat transfer on flow field increase at such small scales. To gain an insight into the effects of heat transfer on the internal flow dynamics, numerical investigations were carried out with adiabatic, isothermal and conjugate heat transfer boundary treatments at the wall, and the results compared and discussed in the present study. With the light shed by the discussion of adiabatic and conjugate heat transfer boundary treatments, this work presents investigations of the heat flux distributions, as well as the effects of heat transfer on the internal flow dynamics and the consequent charging and discharging processes for various sizes. When heat transfer is taken into account, states of fluid in the cell before compression process varies, shock waves in compression process are found to be weaker, and changes in the charging and discharging processes are observed. Heat transfer differences between conjugate heat transfer boundary treatment and isothermal boundary treatment are addressed through comparisons of local wall temperature and heat flux. As a result, the difference in discharging temperature of high pressure fluid is noticeable in all sizes investigated, and the rapid increase of differences between results of isothermal and conjugate heat transfer boundary treatment in small size reveals that for certain small sizes (length of cell < 23 mm) the thermal boundary treatment should be taken care of.
Heat transfer and mechanical interactions in fusion nuclear systems
International Nuclear Information System (INIS)
Nygren, R.E.
1984-01-01
This general review of design issues in heat transfer and mechanical interactions of the first wall, blanket and shield systems of tokamak and mirror fusion reactors begins with a brief introduction to fusion nuclear systems. The design issues are summarized in tables and the following examples are described to illustrate these concerns: the surface heating of limiters, heat transfer from solid breeders, MHD effects in liquid metal blankets, mechanical loads from electromagnetic transients and remote maintenance
Energy Technology Data Exchange (ETDEWEB)
Dyrboel, Susanne
1998-05-01
Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For large thickness dimensions the resulting heat transfer through the
International symposium on radiative heat transfer: Book of abstracts
International Nuclear Information System (INIS)
1995-01-01
The international symposium on radiative heat transfer was held on 14-18 August 1995 Turkey. The specialists discussed radiation transfer in materials processing and manufacturing, solution of radiative heat transfer equation, transient radiation problem and radiation-turbulence interactions, raditive properties of gases, atmospheric and stellar radiative transfer , radiative transfer and its applications, optical and radiative properties of soot particles, inverse radiation problems, partticles, fibres,thermophoresis and waves and modelling of comprehensive systems at the meeting. Almost 79 papers were presented in the meeting
Taha, T.J.; Lefferts, Leonardus; van der Meer, Theodorus H.
2013-01-01
In this work, an experimental heat transfer investigation was carried out to investigate the combined influence of both amorphous carbon (a-C) layer thickness and carbon nanofibers (CNFs) on the convective heat transfer behavior. Synthesis of these carbon nano structures was achieved using catalytic
International Nuclear Information System (INIS)
Jung, B. R.; Park, H. S.; Chung, D. M.; Baik, S. J.
1999-01-01
The computer program SAFE has been used to size and analyze the performance of a steam generator which has two types of heat transfer regions in Korean Standard Nuclear Power Plants (KSNP) and Korean Next Generation Reactor (KNGR) design. The SAFE code calculates the analytical boiling heat transfer area using the modified form of the saturated nucleate pool boiling correlation suggested by Rohsenow. The predicted heat transfer area in the boiling region is multiplied by a constant to obtain a final analytical heat transfer area. The inclusion of the multiplier in the analytical calculation has some disadvantage of loss of complete correlation by the governing heat transfer equation. Several comparative analyses have been performed quantitatively to evaluate the possibility of removing the multiplier in the analytical calculation in the SAFE code. The evaluation shows that the boiling correlation and multiplier used in predicting the boiling region heat transfer area can be replaced with other correlations predicting nearly the same heat transfer area. The removal of multiplier included in the analytical calculation will facilitate a direct use of a set of concerned analytical sizing values that can be exactly correlated by the governing heat transfer equation. In addition this will provide more reasonable basis for the steam generator thermal sizing calculation and enhance the code usability without loss of any validity of the current sizing procedure. (author)
Enhanced two phase flow in heat transfer systems
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.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
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.
The heat transfer mechanisms in fluidized beds; Laemmoensiirtomekanismit leijukerroksessa
Energy Technology Data Exchange (ETDEWEB)
Fogelholm, C.J.; Blomster, A.M.; Kojola, H. [Helsinki Univ. of Technology, Espoo (Finland)
1996-12-01
The goal of the research project is to improve the accuracy of the heat transfer correlation in circulating fluidized beds and to define how the heat transfer is distributed in radiation and convection in the different parts of the fluidized bed. This will be carried out by studying the behaviour and heat transfer of the fluidized bed in the boundary layer near the wall. The total and radiative heat transfer as well as the particle concentration will be measured. Based on the data a correlation will be created. Two different measurement systems are used. The particle concentration is measured by a image-analysis system. A video camera and a Super VHS recorder are used to capture live images from the bed. The images are digitized and stored on a PC. The system has been used in previous research projects at our laboratory. In earlier projects all measurements have been carried out in cold environments. In this project the system will be modified for hot environments. The radiative heat transfer is measured by a radiative heat transfer probe connected to a PC via an A/D converter. The probe consists of a heat flow detector which is isolated from the bed by a sapphire window so that only the radiative part of the heat transfer is detected. The probe will be calibrated in a black body oven so that the effect of the conduction and the sapphire window can be separated. (author)
Validation of heat transfer models for gap cooling
International Nuclear Information System (INIS)
Okano, Yukimitsu; Nagae, Takashi; Murase, Michio
2004-01-01
For severe accident assessment of a light water reactor, models of heat transfer in a narrow annular gap between overheated core debris and a reactor pressure vessel are important for evaluating vessel integrity and accident management. The authors developed and improved the models of heat transfer. However, validation was not sufficient for applicability of the gap heat flux correlation to the debris cooling in the vessel lower head and applicability of the local boiling heat flux correlations to the high-pressure conditions. Therefore, in this paper, we evaluated the validity of the heat transfer models and correlations by analyses for ALPHA and LAVA experiments where molten aluminum oxide (Al 2 O 3 ) at about 2700 K was poured into the high pressure water pool in a small-scale simulated vessel lower head. In the heating process of the vessel wall, the calculated heating rate and peak temperature agreed well with the measured values, and the validity of the heat transfer models and gap heat flux correlation was confirmed. In the cooling process of the vessel wall, the calculated cooling rate was compared with the measured value, and the validity of the nucleate boiling heat flux correlation was confirmed. The peak temperatures of the vessel wall in ALPHA and LAVA experiments were lower than the temperature at the minimum heat flux point between film boiling and transition boiling, so the minimum heat flux correlation could not be validated. (author)
International Nuclear Information System (INIS)
2015-01-01
The conference covered various aspects of heat and mass transfer like Aero-thermodynamics, Atmospheric flows, Biological heat and mass transfer, Combustion and reactive flows, Cryogenics, Electronic and photonic cooling, Energy engineering, Environmental engineering, Experimental techniques, Heat transfer enhancement, Heat transfer equipment's, Heat transfer in nuclear applications, Mass transfer, Materials processing and manufacturing, Microscale and nanoscale transport, Multiphase transport and phase change, Multi mode heat transfer, Numerical methods, Refrigeration and air conditioning, Space heat transfer, Transport phenomena in porous media, and Turbulent transport. Papers relevant to INIS are indexed separately
International Nuclear Information System (INIS)
Stafford, Jason; Walsh, Ed; Egan, Vanessa
2009-01-01
Convective heat transfer, due to axial flow fans impinging air onto a heated flat plate, is investigated with infrared thermography to assess the heated-thin-foil technique commonly used to quantify two-dimensional heat transfer performance. Flow conditions generating complex thermal profiles have been considered in the analysis to account for dominant sources of error in the technique. Uncertainties were obtained in the measured variables and the influences on the resultant heat transfer data are outlined. Correction methods to accurately account for secondary heat transfer mechanisms were developed and results show that as convective heat transfer coefficients and length scales decrease, the importance of accounting for errors increases. Combined with flow patterns that produce large temperature gradients, the influence of heat flow within the foil on the resultant heat transfer becomes significant. Substantial errors in the heat transfer coefficient are apparent by neglecting corrections to the measured data for the cases examined. Methods to account for these errors are presented here, and demonstrated to result in an accurate measurement of the local heat transfer map on the surface
Investigations on post-dryout heat transfer in bilaterally heated annular channels
International Nuclear Information System (INIS)
Tian, W.X.; Qiu, S.Z.; Jia, D.N.
2006-01-01
Post-dryout heat transfer in bilaterally heated vertical narrow annular channels with 1.0, 1.5 and 2.0 mm gap size has been experimentally investigated with deionized water under the condition of pressure ranging from 1.38 to 5.9 MPa and low mass flow rate from 42.9 to 150.2 kg/m 2 s. The experimental data was compared with well known empirical correlations including Groeneveld, Mattson, etc., and none of them gave an ideal prediction. Theoretical investigations were also carried out on post-dryout heat transfer in annular channels. Based on analysis of heat exchange processes arising among the droplets, the vapor and two tube walls of annular channel, a non-equilibrium mechanistic heat transfer model was developed. Comparison indicated that the present model prediction showed a good agreement with our experimental data. Theoretical calculation result showed that the forced convective heat transfer between the heated wall and vapor dominate the overall heat transfer. The heat transfer caused by the droplets direct contact to the wall and the interfacial convection/evaporation of droplets in superheated vapors also had an indispensable contribution. The radiation heat transfer would be neglected because of its small contribution (less than 0.11%) to the total heat transfer
Study on boiling heat transfer of high temperature liquid sodium
International Nuclear Information System (INIS)
Sakurai, Akira
1978-01-01
In the Intitute of Atomic Energy, Kyoto University, fundamental studies on steady state and non-steady state heat flow are underway in connection with reactor design and the safety in a critical accident in a sodium-cooled fast breeder reactor. First, the experimental apparatus for sodium heat transfer and the testing system are described in detail. The apparatus is composed of sodium-purifying section including the plugging meter for measuring purity and cold trap, the pool boiling test section for experimenting natural convection boiling heat transfer, the forced convection boiling test section for experimenting forced convection boiling heat transfer, and gas system. Next, the experimental results by the author and the data obtained so far are compared regarding heat transfer in sodium natural convection and stable nucleating boiling and critical heat flux. The effect of liquid head on a heater on boiling heat transfer coefficient and critical heat flux under the condition of low system pressure in most fundamental pool boiling was elucidated quantitatively, which has been overlooked in previous studies. It was clarified that this is the essentially important problem that can not be overlooked. From this point of view, expressions on heat transfer were also re-investigated. (Wakatsuki, Y.)
Experimental investigation on Heat Transfer Performance of Annular Flow Path Heat Pipe
International Nuclear Information System (INIS)
Kim, In Guk; Kim, Kyung Mo; Jeong, Yeong Shin; Bang, In Cheol
2015-01-01
Mochizuki et al. was suggested the passive cooling system to spent nuclear fuel pool. Detail analysis of various heat pipe design cases was studied to determine the heat pipes cooling performance. Wang et al. suggested the concept PRHRS of MSR using sodium heat pipes, and the transient performance of high temperature sodium heat pipe was numerically simulated in the case of MSR accident. The meltdown at the Fukushima Daiichi nuclear power plants alarmed to the dangers of station blackout (SBO) accident. After the SBO accident, passive decay heat removal systems have been investigated to prevent the severe accidents. Mochizuki et al. suggested the heat pipes cooling system using loop heat pipes for decay heat removal cooling and analysis of heat pipe thermal resistance for boiling water reactor (BWR). The decay heat removal systems for pressurized water reactor (PWR) were suggested using natural convection mechanisms and modification of PWR design. Our group suggested the concept of a hybrid heat pipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. Hybrid heat pipe is the combination of the heat pipe and control rod. In the present research, the main objective is to investigate the effect of the inner structure to the heat transfer performance of heat pipe containing neutron absorber material, B 4 C. The main objective is to investigate the effect of the inner structure in heat pipe to the heat transfer performance with annular flow path. ABS pellet was used instead of B 4 C pellet as cylindrical structures. The thermal performances of each heat pipes were measured experimentally. Among them, concentric heat pipe showed the best performance compared with others. 1. Annular evaporation section heat pipe and annular flow path heat pipe showed heat transfer degradation. 2. AHP also had annular vapor space and contact cooling surface per unit volume of vapor was increased. Heat transfer coefficient of
Directory of Open Access Journals (Sweden)
Luanfang Duan
2018-03-01
Full Text Available In the present work, the contact heat transfer between the granular materials and heating plates inside plate rotary heat exchanger (PRHE was investigated. The heat transfer coefficient is dominated by the contact heat transfer coefficient at hot wall surface of the heating plates and the heat penetration inside the solid bed. A plot scale PRHE with a diameter of Do = 273 mm and a length of L = 1000 mm has been established. Quartz sand with dp = 2 mm was employed as the experimental material. The operational parameters were in the range of ω = 1 – 8 rpm, and F = 15, 20, 25, 30%, and the effect of these parameters on the time-average contact heat transfer coefficient was analyzed. The time-average contact heat transfer coefficient increases with the increase of rotary speed, but decreases with the increase of the filling degree. The measured data of time-average heat transfer coefficients were compared with theoretical calculations from Schlünder’s model, a good agreement between the measurements and the model could be achieved, especially at a lower rotary speed and filling degree level. The maximum deviation between the calculated data and the experimental data is approximate 10%. Keywords: Rotary heat exchanger, Contact heat transfer, Granular material, Heating plate, Overloaded
Heat transfer in flow past a continuously moving porous flat plate with heat flux
Digital Repository Service at National Institute of Oceanography (India)
Murty, T.V.R.; Sarma, Y.V.B.
The analysis of the heat transfer in flow past a continuously moving semi-infinite plate in the presence of suction/ injection with heat flux has been presented. Similarity solutions have been derived and the resulting equations are integrated...
Generalized irreversible heat-engine experiencing a complex heat-transfer law
International Nuclear Information System (INIS)
Chen Lingen; Li Jun; Sun Fengrui
2008-01-01
The fundamental optimal relation between optimal power-output and efficiency of a generalized irreversible Carnot heat-engine is derived based on a generalized heat-transfer law, including a generalized convective heat-transfer law and a generalized radiative heat-transfer law, q ∝ (ΔT n ) m . The generalized irreversible Carnot-engine model incorporates several internal and external irreversibilities, such as heat resistance, bypass heat-leak, friction, turbulence and other undesirable irreversibility factors. The added irreversibilities, besides heat resistance, are characterized by a constant parameter and a constant coefficient. The effects of heat-transfer laws and various loss terms are analyzed. The results obtained corroborate those in the literature
Coupled DM Heating in SCDEW Cosmologies
Directory of Open Access Journals (Sweden)
Silvio Bonometto
2017-08-01
Full Text Available Strongly-Coupled Dark Energy plus Warm dark matter (SCDEW cosmologies admit the stationary presence of ∼1% of coupled-DM and DE, since inflationary reheating. Coupled-DM fluctuations therefore grow up to non-linearity even in the early radiative expansion. Such early non-linear stages are modelized here through the evolution of a top-hat density enhancement, reaching an early virial balance when the coupled-DM density contrast is just 25–26, and the DM density enhancement is ∼10 % of the total density. During the time needed to settle in virial equilibrium, the virial balance conditions, however, continue to modify, so that “virialized” lumps undergo a complete evaporation. Here, we outline that DM particles processed by overdensities preserve a fraction of their virial momentum. Although fully non-relativistic, the resulting velocities (moderately affect the fluctuation dynamics over greater scales, entering the horizon later on.
Khayrullina, A.; Hooff, van T.A.J.; Blocken, B.J.E.; van Heijst, G.J.F.; Sun, Y.; Pei, J.; Zhao, X
This study presents results of coupled 3D steady Reynolds-averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) simulations of an isolated naturally-ventilated building with the application of an air curtain to prevent heat transfer across a doorway. The considered parameters include air
Mixed convection flow and heat transfer in a vertical wavy channel ...
African Journals Online (AJOL)
Mixed convection flow and heat transfer in a vertical wavy channel filled with porous and fluid layers is studied analytically. The flow in the porous medium is modeled using Darcy-Brinkman equation. The coupled non-linear partial differential equations describing the conservation of mass, momentum and energy are solved ...
Handbook of heat and mass transfer. Volume 2
International Nuclear Information System (INIS)
Cheremisinoff, N.P.
1986-01-01
This two-volume series, the work of more than 100 contributors, presents advanced topics in industrial heat and mass transfer operations and reactor design technology. Volume 2 emphasizes mass transfer and reactor design. Some of the contents discussed are: MASS TRANSFER PRINCIPLES - Effect of turbulence promoters on mass transfer. Mass transfer principles with homogeneous and heterogeneous reactions. Convective diffusion with reactions in a tube. Transient mass transfer onto small particles and drops. Modeling heat and mass transport in falling liquid films. Heat and mass transfer in film absorption. Multicomponent mass transfer: theory and applications. Diffusion limitation for reaction in porous catalysts. Kinetics and mechanisms of catalytic deactivation. DISTILLATION AND EXTRACTION - Generalized equations of state for process design. Mixture boiling. Estimating vapor pressure from normal boiling points of hydrocarbons. Estimating liquid and vapor molar fractions in distillation columns. Principles of multicomponent distillation. Generalized design methods for multicomponent distillation. Interfacial films in inorganic substances extraction. Liquid-liquid extraction in suspended slugs. MULTIPHASE REACTOR SYSTEMS - Reaction and mass transport in two-phase reactors. Mass transfer and kinetics in three-phase reactors. Estimating liquid film mass transfer coefficients in randomly packed columns. Designing packed tower wet scrubbers - emphasis on nitrogen oxides. Gas absorption in aerated mixers. Axial dispersion and heat transfer in gas-liquid bubble columns. Operation and design of trickle-bed reactors
A simplified approach for the coupling of excitation energy transfer
Energy Technology Data Exchange (ETDEWEB)
Shi Bo [Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei 230026 (China); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Gao Fang, E-mail: gaofang@iim.ac.cn [Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031 (China); State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); Liang Wanzhen [Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei 230026 (China); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China)
2012-02-06
Highlights: Black-Right-Pointing-Pointer We propose a simple method to calculate the coupling of singlet-to-singlet and triplet-to-triplet energy transfer. Black-Right-Pointing-Pointer Coulomb term are the major contribution to the coupling of singlet-to-singlet energy transfer. Black-Right-Pointing-Pointer Effect from the intermolecular charge-transfer states dorminates in triplet-to-triplet energy transfer. Black-Right-Pointing-Pointer This method can be expanded by including correlated wavefunctions. - Abstract: A simplified approach for computing the electronic coupling of nonradiative excitation-energy transfer is proposed by following Scholes et al.'s construction on the initial and final states [G.D. Scholes, R.D. Harcourt, K.P. Ghiggino, J. Chem. Phys. 102 (1995) 9574]. The simplification is realized through defining a set of orthogonalized localized MOs, which include the polarization effect of the charge densities. The method allows calculating the coupling of both the singlet-to-singlet and triplet-to-triplet energy transfer. Numerical tests are performed for a few of dimers with different intermolecular orientations, and the results demonstrate that Coulomb term are the major contribution to the coupling of singlet-to-singlet energy transfer whereas in the case of triplet-to-triplet energy transfer, the dominant effect is arisen from the intermolecular charge-transfer states. The present application is on the Hartree-Fock level. However, the correlated wavefunctions which are normally expanded in terms of the determinant wavefunctions can be employed in the similar way.
Curry, D. M.; Cox, J. E.
1972-01-01
Coupled nonlinear partial differential equations describing heat and mass transfer in a porous matrix are solved in finite difference form with the aid of a new iterative technique (the strongly implicit procedure). Example numerical results demonstrate the characteristics of heat and mass transport in a porous matrix such as a charring ablator. It is emphasized that multidimensional flow must be considered when predicting the thermal response of a porous material subjected to nonuniform boundary conditions.
Radiative heat transfer in low-dimensional systems -- microscopic mode
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.
Heat transfer and flow characteristics on a gas turbine shroud.
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.
Measurement of heat transfers in cryogenic tank with several configurations
International Nuclear Information System (INIS)
Khemis, O.; Bessaieh, R.; Ait Ali, M.; Francois, M.X.
2004-01-01
The work presented here concerns the measurement of heat transfer in a cryogenic tank with several configurations. The experimental test incorporates the conductive heat in the neck, the convection heat transfers between the inner wall of the neck and the ascending vapor resulting from boiling, and the radiation heat transfers between the external envelope and the tank through a vacuum of 10 -8 mm Hg. An experimental prototype was produced in collaboration with the nuclear center of Orsay in France according to a didactic design, which takes into account the Wexler effect and the importance of the radiation compared to the conduction-convection heat transfer. The addition of a screen radiative ventilated with variable position on the neck (which can effectively replace several tens of floating screens), in order to find the optimal position, which minimizes the radiation flux, is presented in this paper
Transient heat transfer for forced convection flow of helium gas
International Nuclear Information System (INIS)
Liu, Qiusheng; Fukuda, Katsuya; Sasaki, Kenji; Yamamoto, Manabu
1999-01-01
Transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder were measured using a forced convection test loop. The platinum heater with a diameter of 1.0 mm was heated by electric current with an exponential increase of Q 0 exp(t/τ). It was clarified that the heat transfer coefficient approaches the steady-state one for the period τ over 1 s, and it becomes higher for the period of τ shorter than 1 s. The transient heat transfer shows less dependent on the gas flowing velocity when the period becomes very shorter. Semi-empirical correlations for steady-state and transient heat transfer were developed based on the experimental data. (author)
Experimental investigation of heat transfer performance for a novel microchannel heat sink
International Nuclear Information System (INIS)
Wang, Y; Ding, G-F
2008-01-01
We demonstrated a novel microchannel heat sink with a high local heat transfer efficiency contributed by a complicated microchannel system, which comprises parallel longitudinal microchannels etched in a silicon substrate and transverse microchannels electroplated on a copper heat spreader. The thermal boundary layer develops in transverse microchannels. Meanwhile, the heat transfer area is increased compared with the conventional microchannel heat sink only having parallel longitudinal microchannels. Both benefits yield high local heat transfer efficiency and enhance the overall heat transfer, which is attractive for the cooling of high heat flux electronic devices. Infrared tests show the temperature distribution in the test objects. The effects of flow rate and heat flux levels on heat transfer characteristics are presented. A uniform temperature distribution is obtained through the heating area. The reference temperatures decrease with the increasing flow rate from 0.64 ml min −1 to 6.79 ml min −1 for a constant heat flux of 10.4 W cm −2 . A heat flux of 18.9 W cm −2 is attained at a flow rate of 6.79 ml min −1 for assuring the maximum temperature of the microchannel heat sink less than the maximum working temperature of electronic devices
International Nuclear Information System (INIS)
French, R.T.
1975-08-01
Selected experimental data pertinent to piping heat transfer, transient fluid flow regimes, and steam generator heat transfer obtained during the Semiscale Mod-1 isothermal blowdown test series (Test Series 1) are analyzed. The tests in this first test series were designed to provide counterparts to the LOFT nonnuclear experiments. The data from the Semiscale Mod-1 intact and broken loop piping are evaluated to determine the surface heat flux and average heat transfer coefficients effective during the blowdown transient and compared with well known heat transfer correlations used in the RELAP4 computer program. Flow regimes in horizontal pipe sections are calculated and compared with data obtained from horizontal and vertical densitometers and with an existing steady state flow map. Effects of steam generator heat transfer are evaluated quantitatively and qualitatively. The Semiscale Mod-1 data and the analysis presented in this report are valuable for evaluating the adequacy and improving the predictive capability of analytical models developed to predict system response to piping heat transfer, piping flow regimes, and steam generator heat transfer during a postulated loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR). 16 references. (auth)
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
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.
Heat transfer between immiscible liquids enhanced by gas bubbling
International Nuclear Information System (INIS)
Greene, G.A.; Schwarz, C.E.; Klages, J.; Klein, J.
1982-08-01
The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments have been performed with non-reactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies have been performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non-entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model. However heat transfer data for fluid pairs which are found to entrain (water-oil), believed to be characteristic of molten reactor core-concrete conditions, were measured to be up to two orders of magnitude greater than surface renewal predictions and are calculated by a simple entrainment heat transfer model
Radiative heat transfer in the extreme near field.
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
2015-12-17
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 4-6), 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.
Boiling and quenching heat transfer advancement by nanoscale surface modification.
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.
Radiative heat transfer in a heat generating and turbulently convecting fluid layer
International Nuclear Information System (INIS)
Cheung, F.B.; Chan, S.H.; Chawla, T.C.; Cho, D.H.
1980-01-01
The coupled problem of radiative transport and turbulent natural convection in a volumetrically heated, horizontal gray fluid medium, bounded from above by a rigid, isothermal wall and below by a rigid, adiabatic wall, is investigated analytically. An approximate method based upon the boundary layer approach is employed to obtain the dependence of heat transfer at the upper wall on the principal parameters of the problem, which, for moderate Prandtl number, are the Rayleigh number, Ra, the optical thickness, KL, and the conduction-radiation coupling parameter, N. Also obtained in this study is the behaviour of the thermal boundary layer at the upper wall. At large kL, the contribution of thermal radiation to heat transfer in the layer is found to be negligible for N > 10, moderate for N approximately 1, and overwhelming for N < 0.1. However, at small kL, thermal radiation is found to be important only for N < 0.01. While a higher level of turbulence results in a thinner boundary layer, a larger effect of radiation is found to result in a thicker one. Thus, in the presence of strong thermal radiation, a much larger value of Ra is required for the boundary layer approach to remain valid. Under severe radiation conditions, no boundary layer flow regime is found to exist even at very high Rayleigh numbers. Accordingly, the ranges of applicability of the present results are determined and the approximate method justified. In particular, the validity of the present analysis is tested in three limiting cases, ie those of kL → infinity, N → infinity, and Ra → infinity, and is further confirmed by comparison with the numerical solution (author)
Experimental study of heat transfer performance in a flattened AGHP
International Nuclear Information System (INIS)
Tao Hanzhong; Zhang Hong; Zhuang Jun; Jerry Bowman, W.
2008-01-01
Round mini-axial grooved heat pipes (AGHP) with a diameter of 6 mm and a length of 210 mm were pressed into flattened heat pipes with a thickness of 3.5 mm, 3 mm, 2.5 mm and 2 mm, respectively. The article measured the heat transfer limit, thermal resistance and evaporation heat transfer coefficient of the said AGHPs and analyzed and studied the result. The result indicates: the heat transfer limit decreased with the increase of flattening degree. The heat transfer limit of the 2 mm thick flattened AGHP was only 1/4 of that of the φ 6 mm round AGHP. The thermal resistance of the 3.5-2.5 mm thick AGHPs basically maintained stable at around 0.08 deg. C/W, while the thermal resistance of the 2 mm thick flattened AGHP increased obviously. The variation of the heat transfer coefficient in evaporator section with the change of flattening degree follows a similar rule to the variation of thermal resistance. This article serves as a reference to understanding the heat transfer performance of mini AGHP and to electronic cooling design of AGHP
Analysis of a double-pipe heat exchanger performance using heat structure coupling of MARS and CUPID
International Nuclear Information System (INIS)
Amidua, M.; Kim, H.; Cho, H. K.
2015-01-01
Thermal hydraulic phenomena in the inner tube of the double-pipe heat exchanger are expected to be reproducible by one-dimensional system analysis codes (MARS) if a proper condensation heat transfer coefficient is applied. Jeon et al (2013) and Cho et al (2013) conducted comprehensive reviews of the predictive capability of the condensation heat transfer models for the steam-water stratified flow. On the contrary, in the outer tube, a multidimensional analysis tool is required to incorporate the influence of azimuthal angle on the heat transfer rate from the inner tube outer wall to the outer tube fluid. Therefore, a coupled calculation between one dimensional system analysis code and a multidimensional computational fluid dynamics code is an attainable way to predict this effect with a reliable accuracy. CUPID is a three-dimensional computational multiphase fluid dynamics code developed by KAERI (Korea Atomic Energy Research Institute). According to Jeong et al (2010), the objective of the development is to support a resolution for the thermal hydraulic issues regarding the transient multi-dimensional twophase phenomena which can arise in an advanced light water reactor. It uses two-fluid model for the governing equations, which uses two sets of Navier-Stokes' equations for two phases. It can be used as either a typical CFD code or a component code (porous CFD code) depending on the length scale of the phenomena that need to be resolved. On the other hand, MARS is a best estimate thermalhydraulic system code and it was developed at KAERI by consolidating and restructuring the RELAP5/MOD3.2 code and COBRA-TF code (Cho et al., 2014). The MARS code has the capability to analyze best-estimated thermal hydraulic system. In this study, the coupled CUPID-MARS code was used for the simulation of a double-pipe heat exchanger. This paper presents the description of the heat exchanger, the coupling method, and the simulation results using the coupled code. The coupling
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.
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.
An analytical model for annular flow boiling heat transfer in microchannel heat sinks
International Nuclear Information System (INIS)
Megahed, A.; Hassan, I.
2009-01-01
An analytical model has been developed to predict flow boiling heat transfer coefficient in microchannel heat sinks. The new analytical model is proposed to predict the two-phase heat transfer coefficient during annular flow regime based on the separated model. Opposing to the majority of annular flow heat transfer models, the model is based on fundamental conservation principles. The model considers the characteristics of microchannel heat sink during annular flow and eliminates using any empirical closure relations. Comparison with limited experimental data was found to validate the usefulness of this analytical model. The model predicts the experimental data with a mean absolute error 8%. (author)
Conjugate heat transfer analysis for in-vessel retention with external reactor vessel cooling
International Nuclear Information System (INIS)
Park, Jong-Woon; Bae, Jae-ho; Song, Hyuk-Jin
2016-01-01
Highlights: • A conjugate heat transfer analysis method is applied for in-vessel corium retention. • 3D heat diffusion has a formidable effect in alleviating focusing heat load from metallic layer. • The focusing heat load is decreased by about 2.5 times on the external surface. - Abstract: A conjugate heat transfer analysis method for the thermal integrity of a reactor vessel under external reactor vessel cooling conditions is developed to resolve light metal layer focusing effect issue for in-vessel retention. The method calculates steady-state three-dimensional temperature distribution of a reactor vessel using coupled conjugate heat transfer between in-vessel three-layered stratified corium (metallic pool, oxide pool and heavy metal and polar-angle dependent boiling heat transfer at the outer surface of a reactor vessel). The three-layer corium heat transfer model is utilizing lumped-parameter thermal-resistance circuit method. For the ex-vessel boiling boundary conditions, nucleate, transition and film boiling are considered. The thermal integrity of a reactor vessel is addressed in terms of heat flux at the outer-most nodes of the vessel and remaining thickness profile. The vessel three-dimensional heat conduction is validated against a commercial code. It is found that even though the internal heat flux from the metal layer goes far beyond critical heat flux (CHF) the heat flux from the outermost nodes of the vessel may be maintained below CHF due to massive vessel heat diffusion. The heat diffusion throughout the vessel is more pronounced for relatively low heat generation rate in an oxide pool. Parametric calculations are performed considering thermal conditions such as peak heat flux from a light metal layer, heat generation in an oxide pool and external boiling conditions. The major finding is that the most crucial factor for success of in-vessel retention is not the mass of the molten light metal above the oxide pool but the heat generation rate
Enhancing Convective Heat Transfer over a Surrogate Photovoltaic Panel
Fouladi, Fama
This research is particularly focused on studying heat transfer enhancement of a photovoltaic (PV) panel by putting an obstacle at the panel's windward edge. The heat transfer enhancement is performed by disturbing the airflow over the surface and increasing the heat and momentum transfer. Different objects such as triangular, square, rectangular, and discrete rectangular ribs and partial grids were applied at the leading edge of a surrogate PV panel and flow and the heat transfer of the panel are investigated experimentally. This approach was selected to expand understanding of effect of these different objects on the flow and turbulence structures over a flat surface by analyzing the flow comprehensively. It is observed that, a transverse object at the plate's leading edge would cause some flow blockage in the streamwise direction, but at the same time creates some velocity in the normal and cross stream directions. In addition to that, the obstacle generates some turbulence over the surface which persists for a long downstream distance. Also, among all studied objects, discrete rectangular ribs demonstrate the highest heat transfer rate enhancement (maximum Nu/Nu0 of 1.5). However, ribs with larger gap ratios are observed to be more effective at enhancing the heat transfer augmentation at closer distances to the rib, while at larger downstream distances from the rib, discrete ribs with smaller gap ratios are more effective. Furthermore, this work attempted to recognize the most influential flow parameters on the heat transfer enhancement of the surface. It is seen that the flow structure over a surface downstream of an object (flow separation-reattachment behaviour) has a significant effect on the heat transfer enhancement trend. Also, turbulence intensities are the most dominant parameters in enhancing the heat transfer rate from the surface; however, flow velocity (mostly normal velocity) is also an important factor.
Research progresses and future directions on pool boiling heat transfer
M. Kumar; V. Bhutani; P. Khatak
2015-01-01
This paper reviews the previous work carried on pool boiling heat transfer during heating of various liquids and commodities categorized as refrigerants and dielectric fluids, pure liquids, nanofluids, hydrocarbons and additive mixtures, as well as natural and synthetic colloidal solutions. Nucleate pool boiling is an efficient and effective method of boiling because high heat fluxes are possible with moderate temperature differences. It is characterized by the growth of bubbles on a heated s...
Ultrahigh Flux Thin Film Boiling Heat Transfer Through Nanoporous Membranes.
Wang, Qingyang; Chen, Renkun
2018-05-09
Phase change heat transfer is fundamentally important for thermal energy conversion and management, such as in electronics with power density over 1 kW/cm 2 . The critical heat flux (CHF) of phase change heat transfer, either evaporation or boiling, is limited by vapor flux from the liquid-vapor interface, known as the upper limit of heat flux. This limit could in theory be greater than 1 kW/cm 2 on a planar surface, but its experimental realization has remained elusive. Here, we utilized nanoporous membranes to realize a new "thin film boiling" regime that resulted in an unprecedentedly high CHF of over 1.2 kW/cm 2 on a planar surface, which is within a factor of 4 of the theoretical limit, and can be increased to a higher value if mechanical strength of the membranes can be improved (demonstrated with 1.85 kW/cm 2 CHF in this work). The liquid supply is achieved through a simple nanoporous membrane that supports the liquid film where its thickness automatically decreases as heat flux increases. The thin film configuration reduces the conductive thermal resistance, leads to high frequency bubble departure, and provides separate liquid-vapor pathways, therefore significantly enhances the heat transfer. Our work provides a new nanostructuring approach to achieve ultrahigh heat flux in phase change heat transfer and will benefit both theoretical understanding and application in thermal management of high power devices of boiling heat transfer.
Molecular engineering problems in heat and mass transfer
International Nuclear Information System (INIS)
Kotake, S.
1991-01-01
As for developing, manufacturing and applying new materials of advanced functions such as high-performance devices and high-temperature materials, fundamental understanding of the phenomena from the standpoint of molecular and atomic levels has been required. In these problems, the processes of heat and mass transfer play an important role, being one of the rate-controlling factors. But the energy levels associated with heat and mass transfer are of the orders much less than those of chemical reaction, and it is not easy to understand the thermal problems on the molecular and atomic basis. This paper views the processes of heat and mass transfer from the dynamical motions of atom and molecule for thermal engineering problems. Especially, problems are considered of heat conduction in fine-ceramics, sintered materials of high heat conductivity or high heat-insulation, phase change of condensation in vapor deposition processes such as CVD and PVD, and radiation in laser processing
Robust Modelling of Heat and Mass Transfer in Processing of Solid Foods
DEFF Research Database (Denmark)
Feyissa, Aberham Hailu
The study is focused on combined heat and mass transfer during processing of solid foods such as baking and frying processes. Modelling of heat and mass transfer during baking and frying is a significant scientific challenge. During baking and frying, the food undergoes several changes...... in microstructure and other physical properties of the food matrix. The heat and water transport inside the food is coupled in a complex way, which for some food systems it is not yet fully understood. A typical example of the latter is roasting of meat in convection oven, where the mechanism of water transport...... is unclear. Establishing the robust mathematical models describing the main mechanisms reliably is of great concern. A quantitative description of the heat and mass transfer during the solid food processing, in the form of mathematical equations, implementation of the solution techniques, and the value...
International Nuclear Information System (INIS)
Liu, Qiusheng; Fukuda, Katsuya
2003-01-01
The transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder were measured under wide experimental conditions. The platinum cylinder with a diameter of 1.0 mm was used as test heater and heated by electric current with an exponentially increasing heat input of Q 0 exp(t/τ). The gas flow velocities ranged from 5 to 35 m/s, the gas temperatures ranged from 25 to 80degC, and the periods of heat generation rate, τ, ranged from 40 ms to 20 s. The surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The transient heat transfer shows less dependence on the gas flowing velocity when the period becomes very shorter. The gas temperature in this study shows little influence on the heat transfer coefficient. Semi-empirical correlation for quasi-steady-state heat transfer was obtained based on the experimental data. The ratios of transient Nusselt number Nu tr to quasi-steady-state Nusselt number Nu st at various periods, flow velocities, and gas temperatures were obtained. The heat transfer shifts to the quasi-steady-state heat transfer for longer periods and shifts to the transient heat transfer for shorter periods at the same flow velocity. It also approaches the quasi-steady-state one for higher flow velocity at the same period. Empirical correlation for transient heat transfer was also obtained based on the experimental data. (author)
Numerical simulation of gas-liquid two-phase flow behavior with condensation heat transfer
International Nuclear Information System (INIS)
Takamori, Kazuhide; Murase, Michio; Baba, Yoshikazu; Aihara, Tsuyoshi.
1995-01-01
In this study, condensation heat transfer experiments were performed in order to verify a condensation heat transfer model coupled with a three-dimensional two-phase flow analysis. In the heat transfer model, the liquid film flow rate on the heat transfer tubes was calculated by a mass balance equation and the liquid film thickness was calculated from the liquid film flow rate using Nusselt's laminar flow model and Fujii's equation for steam velocity effect. In the experiments, 112 horizontal staggered tubes with an outer diameter of 16 mm and length of 0.55 m were used. Steam and spray water were supplied to the test section, and inlet quality was controlled by the spray water flow rate. The temperature was 100degC and the pressure was 0.1 MPa. The overall heat transfer coefficients were measured for inlet quality of 13-100%. From parameter calculations for the falling liquid film ratio from the upper tubes to the lower tubes, the calculated overall heat transfer coefficients agreed with the data to within ±5% at the falling liquid film ratio of 0.7. (author)
Enhancement of heat transfer using nanofluids - An overview
Energy Technology Data Exchange (ETDEWEB)
Godson, Lazarus; Mohan Lal, D. [Refrigeration and Air-Conditioning Division, Department of Mechanical Engineering., College of Engineering, Anna University, Chennai 600 025, Tamil Nadu (India); Raja, B. [Indian Institute of Information Technology, Design and Manufacturing-Kancheepuram Indian Institute of Technology-Madras, Chennai 600 036, Tamil Nadu (India); Wongwises, S. [Fluid Mechanics, Thermal Engineering and Multiphase Flow (FUTURE), Dept. of Mechanical Engineering, King Mongkut' s University of Technology Thonburi, Bangmod, Bangkok 10140 (Thailand)
2010-02-15
A colloidal mixture of nano-sized particles in a base fluid, called nanofluids, tremendously enhances the heat transfer characteristics of the original fluid, and is ideally suited for practical applications due to its marvelous characteristics. This article addresses the unique features of nanofluids, such as enhancement of heat transfer, improvement in thermal conductivity, increase in surface volume ratio, Brownian motion, thermophoresis, etc. In addition, the article summarizes the recent research in experimental and theoretical studies on forced and free convective heat transfer in nanofluids, their thermo-physical properties and their applications, and identifies the challenges and opportunities for future research. (author)
Heat Transfer and Cooling Techniques at Low Temperature
Baudouy, B
2014-07-17
The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.
Heat transfer modelling in thermophotovoltaic cavities using glass media
Energy Technology Data Exchange (ETDEWEB)
Bauer, T.; Forbes, I.; Penlington, R.; Pearsall, N. [Northumbria University, Newcastle upon Tyne (United Kingdom). School of Engineering and Technology
2005-08-15
Optimisation of heat transfer, and in particular radiative heat transfer in terms of the spectral, angular and spatial radiation distributions, is required to achieve high efficiencies and high electrical power densities for thermophotovoltaic (TPV) conversion. This work examines heat transfer from the radiator to the PV cell in an infinite plate arrangement using three different arrangements of participating dielectric media. The modelling applies the Discrete Ordinates method and assumes fused silica (quartz glass) as the dielectric medium. The arrangement radiator-glass-PV cell (also termed dielectric photon concentration) was found to be superior in terms of efficiency and power density. (author)
Heat Transfer and Cooling Techniques at Low Temperature
Energy Technology Data Exchange (ETDEWEB)
Baudouy, B [Saclay (France)
2014-07-01
The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.
Effect of proton transfer on the electronic coupling in DNA
International Nuclear Information System (INIS)
Rak, Janusz; Makowska, Joanna; Voityuk, Alexander A.
2006-01-01
The effects of single and double proton transfer within Watson-Crick base pairs on donor-acceptor electronic couplings, V da , in DNA are studied on the bases of quantum chemical calculations. Four dimers [AT,AT], [GC,GC], [GC,AT] and [GC,TA)] are considered. Three techniques - the generalized Mulliken-Hush scheme, the fragment charge method and the diabatic states method - are employed to estimate V da for hole transfer between base pairs. We show that both single- and double proton transfer (PT) reactions may substantially affect the electronic coupling in DNA. The electronic coupling in [AT,AT] is predicted to be most sensitive to PT. Single PT within the first base pair in the dimer leads to increase in the hole transfer efficiency by a factor of 4, while proton transfer within the second pair should substantially, by 2.7 times, decrease the rate of charge transfer. Thus, directional asymmetry of the PT effects on the electronic coupling is predicted. The changes in the V da matrix elements correlate with the topological properties of orbitals of donor and acceptor and can be qualitatively rationalized in terms of resonance structures of donor and acceptor. Atomic pair contributions to the V da matrix elements are also analyzed
Process heat transfer principles, applications and rules of thumb
Serth, Robert W
2014-01-01
Process Heat Transfer is a reference on the design and implementation of industrial heat exchangers. It provides the background needed to understand and master the commercial software packages used by professional engineers in the design and analysis of heat exchangers. This book focuses on types of heat exchangers most widely used by industry: shell-and-tube exchangers (including condensers, reboilers and vaporizers), air-cooled heat exchangers and double-pipe (hairpin) exchangers. It provides a substantial introduction to the design of heat exchanger networks using pinch technology, the mos
Unifying quantum heat transfer in a nonequilibrium spin-boson model with full counting statistics
Wang, Chen; Ren, Jie; Cao, Jianshu
2017-02-01
To study the full counting statistics of quantum heat transfer in a driven nonequilibrium spin-boson model, we develop a generalized nonequilibrium polaron-transformed Redfield equation with an auxiliary counting field. This enables us to study the impact of qubit-bath coupling ranging from weak to strong regimes. Without external modulations, we observe maximal values of both steady-state heat flux and noise power in moderate coupling regimes, below which we find that these two transport quantities are enhanced by the finite-qubit-energy bias. With external modulations, the geometric-phase-induced heat flux shows a monotonic decrease upon increasing the qubit-bath coupling at zero qubit energy bias (without bias). While under the finite-qubit-energy bias (with bias), the geometric-phase-induced heat flux exhibits an interesting reversal behavior in the strong coupling regime. Our results unify the seemingly contradictory results in weak and strong qubit-bath coupling regimes and provide detailed dissections for the quantum fluctuation of nonequilibrium heat transfer.
Experimental study on local heat transfer characteristics of porous media with internal heat source
International Nuclear Information System (INIS)
Zan Yuanfeng; Wang Taotao; Xiao Zejun; Wang Fei; Huang Yanping
2008-01-01
Model of porous media with internal heat source is established. The model uses water as flowing media, and the stainless steel test section is packed with steel spheres in manner of regular triangle, respectively. The armoured resistance wire is inserted inside the steel sphere. On the basis of the experimental model, many parameters of the local heat transfer characteristics including current velocity and wall temperature of steel sphere are measured. The experimental results show that the coefficient of heat transfer scarcely changes with pressure. The coefficient of heat transfer increases with the surface heat flux of steel sphere. When raising the inlet temperature of the cooling water, the coefficient of heat transfer presents the descending trend. In addition, the influence of entrance effect on heat transfer is discovered in the experiment, which is much less than the liquid flow in the light tube. After experiment data are analyzed and processed, the relation model of heat transfer on local heat transfer characteristic of porous media with internal heat source was described with a power-law-equation. The deviations between calculation and experimental values are within ±10%. (authors)
Analysis of radiative heat transfer impact in cross-flow tube and fin heat exchangers
Directory of Open Access Journals (Sweden)
Hanuszkiewicz-Drapała Małgorzata
2016-03-01
Full Text Available A cross-flow, tube and fin heat exchanger of the water – air type is the subject of the analysis. The analysis had experimental and computational form and was aimed for evaluation of radiative heat transfer impact on the heat exchanger performance. The main element of the test facility was an enlarged recurrent segment of the heat exchanger under consideration. The main results of measurements are heat transfer rates, as well as temperature distributions on the surface of the first fin obtained by using the infrared camera. The experimental results have been next compared to computational ones coming from a numerical model of the test station. The model has been elaborated using computational fluid dynamics software. The computations have been accomplished for two cases: without radiative heat transfer and taking this phenomenon into account. Evaluation of the radiative heat transfer impact in considered system has been done by comparing all the received results.
An ecofriendly graphene-based nanofluid for heat transfer applications
DEFF Research Database (Denmark)
Mehrali, Mohammad; Sadeghinezhad, Emad; Akhiani, Amir Reza
2016-01-01
including chemical stability, viscosity, wettability, electrical conductivity and thermal conductivity were investigated in a comprehensive manner. A significant thermal conductivity enhancement amounting to 45.1% was obtained for a volume fraction of 4%. In addition, the convective heat transfer...... that the generated nanofluid will open a new avenue in the pursuit of ecofriendly thermal conductors for heat transfer applications....... coefficient of the nanofluid in a laminar flow regime with uniform wall heat flux was investigated to estimate its cooling capabilities. These results, firmly confirm that the generated graphene-based nanofluid is a formidable transporter of heat and yet ecofriendly. Therefore, it's anticipate...
Heat transfer characteristics of alkali metals flowing across tube banks
International Nuclear Information System (INIS)
Sugiyama, K.; Ishiguro, R.; Kojima, Y.; Kanaoka, H.
2004-01-01
For the purpose of getting heat transfer coefficients of alkali metals flowing across tube banks at an acceptable level, we propose to use an inviscid-irrotational flow model, which is based on our flow visualization experiment. We show that the heat transfer coefficients obtained for the condition where only the test rod is heated in tube banks considerably differ from those obtained for the condition where all the rods are heated, because of interference between thick thermal boundary layers of alkali metals. We also confirm that the analytical values obtained by this flow model are in a reasonable agreement with experimental values. (author)
Identification of the Heat Transfer Coefficient at the Charge Surface Heated on the Chamber Furnace
Directory of Open Access Journals (Sweden)
Gołdasz A.
2017-06-01
Full Text Available The inverse method was applied to determine the heat flux reaching the charge surface. The inverse solution was based upon finding the minimum of the error norm between the measured and calculated temperatures. The charge temperature field was calculated with the finite element method by solving the heat transfer equation for a square charge made of 15HM steel heated on all its surfaces. On the basis of the mean value of heat flux, the value of the heat transfer coefficient at each surface was determined depending on the surface temperature of the material heated.
Heat transfer characteristics of building walls using phase change material
Irsyad, M.; Pasek, A. D.; Indartono, Y. S.; Pratomo, A. W.
2017-03-01
Minimizing energy consumption in air conditioning system can be done with reducing the cooling load in a room. Heat from solar radiation which passes through the wall increases the cooling load. Utilization of phase change material on walls is expected to decrease the heat rate by storing energy when the phase change process takes place. The stored energy is released when the ambient temperature is low. Temperature differences at noon and evening can be utilized as discharging and charging cycles. This study examines the characteristics of heat transfer in walls using phase change material (PCM) in the form of encapsulation and using the sleeve as well. Heat transfer of bricks containing encapsulated PCM, tested the storage and released the heat on the walls of the building models were evaluated in this study. Experiments of heat transfer on brick consist of time that is needed for heat transfer and thermal conductivity test as well. Experiments were conducted on a wall coated by PCM which was exposed on a day and night cycle to analyze the heat storage and heat release. PCM used in these experiments was coconut oil. The measured parameter is the temperature at some points in the brick, walls and ambient temperature as well. The results showed that the use of encapsulation on an empty brick can increase the time for thermal heat transfer. Thermal conductivity values of a brick containing encapsulated PCM was lower than hollow bricks, where each value was 1.3 W/m.K and 1.6 W/m.K. While the process of heat absorption takes place from 7:00 am to 06:00 pm, and the release of heat runs from 10:00 pm to 7:00 am. The use of this PCM layer can reduce the surface temperature of the walls of an average of 2°C and slows the heat into the room.
Radiative heat transfer and water content in atmosphere of Venus
International Nuclear Information System (INIS)
Yarov, M.Y.; Gal'stev, A.P.; Shari, V.P.
1985-01-01
The authors present the procedure for calculating optical characteristics of the main components and the effective fluxes in the atmosphere of Venus, and concrete results of the calculations. They are compared to the results of other authors and to the experimantal data. Integration was carried out by the Simpson method with automatic selection of the step or interval for a given relative integrating accuracy delta. The calculations were done with a BESM-6 computer. Using this procedure and data on absorbtion coefficients, calculations of the spectrum of effective flux were carried out for a pure carbon dioxide atmosphere and for an atmosphere containing water vapor at various relative admixtures, for different altitude profiles of temperature and cloudiness albedo. Thus, the comparisons made, enable the authors to judge about the degree of agreement of the F(z) altitude profile, in some regions of the planet where measurements have been made, rather than about the absolute values of the heat fluxes. In conclusion, the authors point out that the task of calculating in detail the radiation balance in Venus' lower atmosphere, as also the problem of a more reliable interpretation of the experimantal data, is coupled with the necessity of elaborating reliable models of the atmospheric components' optical characteristics, which determine the radiative transfer of heat
Numerical simulation of heat transfer in metal foams
Gangapatnam, Priyatham; Kurian, Renju; Venkateshan, S. P.
2018-02-01
This paper reports a numerical study of forced convection heat transfer in high porosity aluminum foams. Numerical modeling is done considering both local thermal equilibrium and non local thermal equilibrium conditions in ANSYS-Fluent. The results of the numerical model were validated with experimental results, where air was forced through aluminum foams in a vertical duct at different heat fluxes and velocities. It is observed that while the LTE model highly under predicts the heat transfer in these foams, LTNE model predicts the Nusselt number accurately. The novelty of this study is that once hydrodynamic experiments are conducted the permeability and porosity values obtained experimentally can be used to numerically simulate heat transfer in metal foams. The simulation of heat transfer in foams is further extended to find the effect of foam thickness on heat transfer in metal foams. The numerical results indicate that though larger foam thicknesses resulted in higher heat transfer coefficient, this effect weakens with thickness and is negligible in thick foams.
Fourier analysis of conductive heat transfer for glazed roofing materials
Energy Technology Data Exchange (ETDEWEB)
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah [Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Zakaria, Nor Zaini [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)
2014-07-10
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Evaporation heat transfer of hot water from horizontal free service
International Nuclear Information System (INIS)
Koizumi, Y.; Ebihara, Y.; Hirota, T.; Murase, M.
2011-01-01
Evaporation heat transfer from the hot water flow to the cold air flow in a horizontal duct was examined. Hot water was in the range of 35 o C ~ 65 o C. Cold air was approximately 25 o C. The air velocity was varied from 0.0656 m/s ~ 1.41 m/s. The heat transfer rate from the water flow to the air flow became large with an increase in the air velocity. The higher the water temperature was, the larger the heat transfer rate was. When the total heat flux from water to the air flow is divided into two terms; the evaporation term and the forced flow convection term, the evaporation term dominate main part and that is about 90 ~ 80 % of the total heat flux. The measured values of the evaporation term and the forced flow convection term were larger than the predicted because of the effect of the diffusion of evaporated vapor. The correlation to predict the heat transfer from the hot water flow to the cold air flow with the evaporation was developed by modifying the laminar flow mass transfer correlation and the laminar forced convection heat transfer correlation. Good results were obtained. (author)
Evaporation heat transfer of hot water from horizontal free service
Energy Technology Data Exchange (ETDEWEB)
Koizumi, Y.; Ebihara, Y.; Hirota, T. [Shinshu Univ., Ueda, Nagano (Japan); Murase, M. [INSS, Mihama-cho, Fukui (Japan)
2011-07-01
Evaporation heat transfer from the hot water flow to the cold air flow in a horizontal duct was examined. Hot water was in the range of 35{sup o}C ~ 65{sup o}C. Cold air was approximately 25{sup o}C. The air velocity was varied from 0.0656 m/s ~ 1.41 m/s. The heat transfer rate from the water flow to the air flow became large with an increase in the air velocity. The higher the water temperature was, the larger the heat transfer rate was. When the total heat flux from water to the air flow is divided into two terms; the evaporation term and the forced flow convection term, the evaporation term dominate main part and that is about 90 ~ 80 % of the total heat flux. The measured values of the evaporation term and the forced flow convection term were larger than the predicted because of the effect of the diffusion of evaporated vapor. The correlation to predict the heat transfer from the hot water flow to the cold air flow with the evaporation was developed by modifying the laminar flow mass transfer correlation and the laminar forced convection heat transfer correlation. Good results were obtained. (author)
Numerical simulation of shell-side heat transfer and flow of natural circulation heat exchanger
International Nuclear Information System (INIS)
Xue Ruojun; Deng Chengcheng; Li Chaojun; Wang Mingyuan
2012-01-01
In order to analyze the influence on the heat transfer and flow characteristics of the heat exchanger model of different solving models and structures, a variety of transformation to the model equivalent for the heat exchanger was studied. In this paper, Fluent software was used to simulate the temperature-field and flow-field of the equivalent model, and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distribution of temperature-field and flow-field for different models, the heat-transferring process and natural convection situation of heat exchanger were deeply understood. The results show that the temperature difference between the inside and outside of the natural circulation heat exchanger tubes is larger and the flow is more complex, so the turbulence model is the more reasonable choice. Asymmetry of tubes position makes the flow and heat transfer of the fluid on both sides to be dissymmetrical and makes the fluid interaction, and increases the role of natural convection. The complex structure of heat exchanger makes the flow and heat transfer of the fluid on both sides to be irregular to some extent when straight tubes into C-bent are transformed, and all these make the turbulence intensity increase and improve the effect of heat transfer. (authors)
Heat transfer and thermoregulation in the largemouth blackbass, Micropterus salmoides
Energy Technology Data Exchange (ETDEWEB)
Erskine, D. J.
1976-01-01
An energy budget equation, based on energy budget theory for terrestrial organisms, was developed to describe the heat energy exchange between a largemouth bass (Micropterus salmoides) and its aquatic environment. The energy budget equation indicated that convection and a combined conduction-convection process were major avenues of heat exchange for a fish. Solid aluminum castings were used to experimentally determine heat transfer coefficients for the largemouth bass at water velocities covering the free and forced convection ranges. Heat energy budget theory was applied to the casting data and the derived coefficients were used to characterize heat exchange between the bass and its aquatic habitat. The results indicate that direct transfer of heat from the body surface is the major mechanism of heat exchange for a fish.
Single-phase convective heat transfer in rod bundles
International Nuclear Information System (INIS)
Holloway, Mary V.; Beasley, Donald E.; Conner, Michael E.
2008-01-01
The convective heat transfer for turbulent flow through rod bundles representative of nuclear fuel rods used in pressurized water reactors is examined. The rod bundles consist of a square array of parallel rods that are held on a constant pitch by support grids spaced axially along the rod bundle. Split-vane pair support grids, which create swirling flow in the rod bundle, as well as disc and standard support grids are investigated. Single-phase convective heat transfer coefficients are measured for flow downstream of support grids in a rod bundle. The rods are heated using direct resistance heating, and a bulk axial flow of air is used to cool the rods in the rod bundle. Air is used as the working fluid instead of water to reduce the power required to heat the rod bundle. Results indicate heat transfer enhancement for up to 10 hydraulic diameters downstream of the support grids. A general correlation is developed to predict the heat transfer development downstream of support grids. In addition, circumferential variations in heat transfer coefficients result in hot streaks that develop on the rods downstream of split-vane pair support grids