Heat Transfer: Volume 4最新文献

{"title":"Numerical Modeling of Heat Transfer and Water Shedding in Automotive Evaporator Louvered Fins","authors":"Deming Wang, Chao Zhang","doi":"10.1115/imece2000-1530","DOIUrl":"https://doi.org/10.1115/imece2000-1530","url":null,"abstract":"\u0000 A mathematical model has been developed to simulate mass and heat transfer of humid air flows at the airside of automobile air conditioning evaporators. The phenomenon of water condensation and water shedding in louvered fins are modeled based on extension of the existing Eulerian two-fluid method which treats water and air as two continuous media. A species transport equation for the mass fraction of water vapor in humid air is solved. The condensation of water from the air mixture translates into a sink term for the vapor transport equation and an equal source in the continuity equation for the volume fraction of liquid water in the two-fluid system of equations. A critical element in modeling the condensate transport in louvered fins calls for a surface tension force sub-model, since the surface tension force is the primary resistance against water shedding and draining. A formulation is proposed to evaluate the surface tension force based on searching for the most probable liquid-air interface where sharp gradient of water volume fraction exists. Numerical aspect of the implementation is discussed. In order to validate the model and demonstrate the applicability of the present methodology, a six-louver two-dimensional test case is established. The relative influence of the stopping force on liquid distribution pattern and flow was illustrated. The simulation is then carried out on a full-scale 2-D louvered fin design for different operating conditions. This study has demonstrated the feasibility of modeling “wet” heat transfer and water shedding in evaporator fins with an Eulerian two-fluid based method.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"179 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122565554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stacked Microchannel Heat Sinks for Liquid Cooling of Microelectronic Components","authors":"Xiaojin Wei, Y. Joshi","doi":"10.1115/1.1647124","DOIUrl":"https://doi.org/10.1115/1.1647124","url":null,"abstract":"\u0000 A novel heat sink based on a multi-layer stack of liquid cooled microchannels is investigated. For a given pumping power and heat removal capability for the heat sink, the flow rate across a stack of microchannels is lower compared to a single layer of microchannels. Numerical simulations using a computationally efficient multigrid method [1] were carried out to investigate the detailed conjugate transport within the heat sink. The effects of the microchannel aspect ratio and total number of layers on thermal performance were studied for water as coolant. A heat sink of base area 10 mm by 10 mm with a height in the range 1.8 to 4.5 mm (2–5 layers) was considered with water flow rate in the range 0.83×10−6 m3/s (50 ml/min) to 6.67×10−6 m3/s (400 ml/min). The results of the computational simulations were also compared with a simplified thermal resistance network analysis.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115214248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of RELAP5 Drift-Flux Model for Vertical Subcooled Boiling Flow at Low Pressure Conditions","authors":"B. Končar, I. Kljenak, B. Mavko","doi":"10.1115/imece2000-1535","DOIUrl":"https://doi.org/10.1115/imece2000-1535","url":null,"abstract":"\u0000 The RELAP5/MOD3.2.2 Gamma code was assessed against low pressure boiling flow experiments performed by Zeitoun and Shoukri (1997) in a vertical annulus. The predictions of subcooled boiling bubbly flow showed that the present version of the RELAP5 code underestimates the void fraction increase along the flow and strongly overestimates the vapor drift velocity. It is shown that in the calculations, a higher vapor drift velocity causes a lower interphase drag and may be a possible reason for underpredicted void fraction development. A modification is proposed, which introduces the replacement of the EPRI drift-flux formulation, which is currently incorporated in the RELAP5 code, with the Zuber-Findlay (1965) drift-flux model for the experimental low pressure conditions of the vertical bubbly flow regime. The improved experiment predictions with the modified RELAP5 code are presented and analysed.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116382699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Fully Eulerian Approach to Particle-Laden Compressible Flows","authors":"A. Dolatabadi, J. Mostaghimi, Mihajlo Ivanovic","doi":"10.1115/imece2000-1525","DOIUrl":"https://doi.org/10.1115/imece2000-1525","url":null,"abstract":"\u0000 Dense particles in highly compressible gas flows are analyzed using the Eulerian-Eulerian approach. Simulations are applied to a High Velocity Oxy-Fuel (HVOF) thermal spray torch. In this analysis, by using a fully Eulerian approach, the dispersed flow like the continuous flow is considered in the Eulerian frame whereby most of the physical aspects of the gas-particle flow in the HVOF process can be incorporated. These two phases are coupled through momentum and energy exchanges that are expressed in the form of source terms appearing in the governing equations. The numerical simulations show large variations in gas velocity and temperature both inside and outside the torch due to flow features such as mixing layers, shock waves, and expansion waves. The characteristics of the particles such as velocity and temperature are analyzed.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129674508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theoretically-Based Leidenfrost Point Model","authors":"J. Bernardin, I. Mudawar","doi":"10.1115/imece2000-1502","DOIUrl":"https://doi.org/10.1115/imece2000-1502","url":null,"abstract":"\u0000 This study presents a theoretically-based model of the Leidenfrost point (LFP); the minimum liquid/solid interface temperature required to support film boiling on a smooth surface. The model is structured around bubble nucleation, growth, and merging criteria, as well as surface cavity size characterization. It is postulated that for liquid/solid interface temperatures at and above the LFP, a sufficient number of cavities (about 20%) are activated and the bubble growth rates are sufficiently fast that a continuous vapor layer is established nearly instantaneously between the liquid and the solid. The model is applicable to both pools of liquid and sessile droplets. The effect of surface cavity distribution on the LFP predicted by the model is verified for boiling on aluminum, nickel and silver surfaces, as well as on a liquid gallium surface. The model exhibits good agreement with experimental sessile droplet data for water, FC-72, and acetone. While the model was developed for smooth surfaces on which the roughness asperities are of the same magnitude as the cavity radii (0.1–1.0 μm), it is capable of predicting the boundary or limiting Leidenfrost temperature for rougher surfaces with good accuracy.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124165699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transient Axial Free Jet Impinging Over a Flat Uniformly Heated Disk: Solid–Fluid Properties Effects","authors":"A. Bula, M. M. Rahman, J. Leland","doi":"10.1115/imece2000-1543","DOIUrl":"https://doi.org/10.1115/imece2000-1543","url":null,"abstract":"\u0000 Transient conjugate heat transfer process during axial free jet impingement on a solid disk of finite thickness was considered. As the fluid reached steady state, power was turned on and a uniform heat flux was imposed on the disk at its opposite surface. The numerical model considered both solid and fluid regions. Equations for conservation of mass, momentum, and energy were solved in the liquid region taking into account the transport processes at the inlet and exit boundaries, as well as at the solid-liquid and liquid-gas interfaces. Inside the solid, only the heat conduction equation was solved. The shape and location of the free surface (liquid-gas interface) was determined iteratively as a part of the solution process by satisfying the kinematic condition as well as the balance of normal and shear forces at this interface. A non-uniform grid distribution, captured from a systematic grid-independence study, was used to adequately accommodate large variations near the solid-fluid interface. Computed results include the simulation of six different substrate materials namely, aluminum, constantan, copper, diamond, silicon, and silver, and three different impinging liquids, FC - 77, Mil - 7808, and water. The solids and fluids selected covered a wide range of possibilities of conjugate heat transfer phenomena. The analysis performed showed that the thermal storage capacity, defined as density times specific heat, is an important factor defining which material will attain steady state faster during conjugate heat transfer process, like the thermal diffusivity does it for pure conduction heat transfer.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132509229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal Spreading Resistance of Eccentric Heat Sources on Rectangular Flux Channels","authors":"Y. Muzychka, J. Culham, M. Yovanovich","doi":"10.1115/1.1568125","DOIUrl":"https://doi.org/10.1115/1.1568125","url":null,"abstract":"\u0000 A general solution, based on separation of variables method for thermal spreading resistances of eccentric heat sources on a rectangular flux channel is presented. Solutions are obtained for both isotropic and compound flux channels. The general solution can also be used to model any number of discrete heat sources on a compound or isotropic flux channel using superposition. Several special cases involving a single and multiple heat sources are presented.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132649757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ATR Flow Blockage Tests and CFD Simulations","authors":"Chang H. Oh, S. A. Atkinson","doi":"10.1115/imece2000-1532","DOIUrl":"https://doi.org/10.1115/imece2000-1532","url":null,"abstract":"\u0000 Steady state flow channel blockage tests were conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) as part of the safety basis upgrade program for the Advanced Test Reactor (ATR). The tests were sponsored by the U.S. Department of Energy (DOE). This study was aimed at carrying out flow blockage tests, establishing a base case to compare test results with numerical results using a computational fluid dynamics code, calculating temperature profiles for blockage cases, and determining whether or not the ATR core would be exposed to core melting due to blockage of the inlet of a fuel cooling channel.\u0000 The test section consisted of three parallel channels and two side channels along the side plate. Three cases were selected to evaluate flow blockage events in the channels. A base case with all the channels open, Case 1 where the inlet of the middle channel is blocked, and Case 2 where both the middle channel and the side channel are blocked.\u0000 Laser Doppler anemometer (LDA) was used to measure velocities in the channel. Velocities were measured at 2.54-mm intervals in the channel width, and every 1.27-mm around side windows in the flow direction for three parallel channels.\u0000 LDA measured velocity profiles for the base case and Case 1 indicated good agreement with predicted velocity profiles from the CFD model. The channel velocity in the blocked channel is about 70% of the velocity in the unblocked, adjacent channel in between the top and second side channel vents. Additional flow redistribution occurs into the blocked channel at the second side channel vent.\u0000 Temperature calculations for the base case were made to compare with benchmark temperatures calculated with the ATR SINDA model and CFD calculations underpredicted benchmark plate temperatures by less than 10% while it predicted bulk temperatures very well. The same heat flux and boundary conditions were incorporated for Case 1 and Case 2. The results for both cases indicated that core melt would not occur in the postulated ATR flow channel blockage events simulated for this study. Peak fuel plate temperature is about 20% greater than the peak temperature for the unblocked case just upstream of the second side channel vent.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131757383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling and Simulation of Subcooled Turbulent Boiling Flow","authors":"J. A. Zarate, R. Roy, S. Kang, Andre Laporta","doi":"10.1115/imece2000-1531","DOIUrl":"https://doi.org/10.1115/imece2000-1531","url":null,"abstract":"\u0000 Modeling and numerical simulation of turbulent sub-cooled boiling flow of refrigerant-113 through a vertical concentric annular channel with its inner wall heated are reported. The two-fluid model conservation equations were solved. The Reynolds stresses in the liquid phase momentum equation were closed using the gradient transport approximation. The turbulent viscosity was considered to be comprised of shear-induced and bubble-induced components. Boiling at the inner wall was described by a wall heat transfer model which splits the wall heat flux into convective, quenching, and vaporization heat flux components. This model was modified to reflect our measurement of the radial turbulent heat flux in the liquid phase near the wall. In addition, new wall laws for the liquid phase mean temperature and axial velocity were used. The computational results are compared with our measurements wherever possible.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134475640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Steady-State Operation of a Loop Heat Pipe With Analytical Prediction","authors":"H. Watson, C. Gerhart, G. Mulholland, D. Gluck","doi":"10.1115/imece2000-1551","DOIUrl":"https://doi.org/10.1115/imece2000-1551","url":null,"abstract":"\u0000 The steady-state performance of an 800W, sintered nickel powder wick, loop heat pipe (LHP) has been analyzed using a modified Dynatherm LHP Thermal Model. Results from characterization tests of this LHP performed at the Air Force Research Laboratory in Albuquerque, NM are used as the basis for comparison and discussion of results for the analytical model. The analytical predictions gave excellent correlation to the measured data for power levels ranging from 50 to 1500W at condenser chiller settings between −40°C and 20°C, with the LHP in a horizontal orientation.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121226300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}