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基于方形锂离子电池生热特点,设计了一款新型仿生翅脉流道冷板。在数值传热学理论基础上,建立了仿生翅脉流道冷板的电池组液冷冷却散热模型,对仿生翅脉流道冷板和进出口位置不同的两种并行流道冷板的锂离子电池组冷却散热分别进行了数值模拟计算,并分析了电池组相邻冷板冷却液流向和流道槽深等参数对仿生翅脉流道冷板散热的影响。结果表明:与并行流道冷板相比,仿生翅脉流道冷板冷却不仅能够进一步降低电池组最高温度和温差,提升温度分布均匀性,还可以减小流道压力损失,降低能量消耗。电池组相邻冷板冷却液交错流比同向流电池组的表面最高温度降低了0.62 K,温差减小了1.13 K,平均温度变化相差不大,温度场分布均匀性得到进一步提升;冷却液质量流量不变,随着流道槽深的增大,电池组的最高温度、平均温度和温差均出现先增大后减小的现象,但随着流道槽深的增加,电池组的重量和所占空间也会增加,当流道槽深为2 mm时冷板冷却效果最优。研究结果可为探索散热性能更好、能耗更低的电池组热管理系统提供参考。 相似文献
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液冷板冷却技术是解决高功率芯片热管理问题最有前途的技术之一,带翅片结构的液冷板具有低流阻、低热阻的优势,因而受到广泛关注。目前翅片结构多以实心为主,空心交错翅片对液冷板散热能力和压降等冷却特性的影响尚未得到系统的研究。对此,设计了空心交错翅片液冷板,采用数值模拟的方法研究进口温度和流量对液冷板流动换热特性的影响。模拟结果表明,空心翅片式液冷板具有良好的散热性能,随着进口温度的升高,液冷板温度不均匀性逐渐降低,但降低趋势有所减缓,而流量的增大对降低平均热阻有显著的作用,当进口流量超过1.2 L/min时,液冷板的平均热阻可低于0.04℃/W;然而,流量的增大也提高了流动阻力,当流量增大至1.7 L/min时,流体出口区域形成涡旋,产生回流区,不利于液冷板的散热效果,且流动阻力增大。 相似文献
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为研究蛇形流道结构燃料电池流道宽度和脊宽度对燃料电池极板流道流通特性的影响,运用多物理场仿真软件Comsol对不同流道宽度和脊宽度的蛇型流道结构进行仿真,分析流道宽度和脊宽度对流道压降和流道内流体质量流量的影响。结果表明:脊宽度对流道压降和流体质量流量分布的影响小于流道宽度的影响;增大流道宽度可以降低流道压降,增大流道内流体的质量流量;增大脊宽度可以使质量流量小幅减小。综合考虑流道宽度和脊宽度对压降和流体质量流量分布的影响,应在合理范围内尽量增大流道宽度,且脊宽度不应过小。 相似文献
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随着对强化传热的广泛重视与研究,利用混沌对流来强化传热的新技术得到了关注.利用CFD软件Fluent对C型混沌结构内的流体流动与传热进行数值模拟,对比了C型混沌结构与普通平直结构在流体流动场、温度场分布和传热特性等细观信息,分析了C型混沌结构的强化传热性能及特点.分析结果表明,C型混沌结构使流体在较小速度下产生混沌对流,这种流态增加了流体的扰动与湍动,增大主流区或近壁处流动的混合,强化了流道内的传热,使流道横截面上的温度分布均匀化;混沌对流内的传热Nu数和Po数(即fRe值)不再象普通层流为一定值,而随Re数的增大而增大. 相似文献
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为分析平面S型轴伸贯流泵装置泵内流动特性,采用软件CFX对平面S型泵装置开展三维全流道数值模拟,并采用能量梯度理论分析不同工况下泵装置内的流动特性。结果表明,不同流量工况下平面S型轴伸贯流泵装置进水流道内的水流均非常平顺,整体差异较小。出水流道内的水流流态差别较大,流量越小出水流道内流态越差。小流量工况下平面S型轴伸贯流泵装置内相同位置的压力脉动最大。小流量工况下出水流道内能量梯度差异最大,说明此工况下出水流道内会产生较大的能量损失。平面S型轴伸贯流泵装置出水流道设计时应尽量增加出水流道的平顺段长度,保证能量梯度分布均匀。研究结果为深入了解平面S型轴伸泵装置和优化设计提供了理论指导。 相似文献
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《International Journal of Heat and Mass Transfer》1987,30(7):1359-1369
Irreversible entropy generation for combined forced convection heat and mass transfer in a twodimensional channel is investigated. The heat and mass transfer rates are assumed to be constant on both channel walls. For the case of laminar flow, the entropy generation is obtained as a function of velocity, temperature, concentration gradients and the physical properties of the fluid. The analogy between heat and mass transfer is used to obtain the concentration profile for the diffusing species. The optimum plate spacing is determined, considering that either the mass flow rate or the channel length are fixed. For the turbulent flow regime, a control volume approach that uses heat and mass transfer correlations is developed to obtain the entropy generation and optimum plate spacing. 相似文献
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In this paper a second law analysis of a cross-flow heat exchanger (HX) is studied in the presence of a balance between the entropy generation due to heat transfer and fluid friction. The entropy generation in a cross-flow HX with a new winglet-type convergent–divergent longitudinal vortex generator (CDLVG) is investigated. Optimization of HX channel geometry and effect of design parameters regarding the overall system performance are presented. For the HX flow lengths and CDLVGs the optimization model was developed on the basis of the entropy generation minimization (EGM). It was found that increasing the cross-flow fluid velocity enhances the heat transfer rate and reduces the heat transfer irreversibility. The test results demonstrate that the CDLVGs are potential candidate procedure to improve the disorderly mixing in channel flows of the cross-flow type HX for large values of the Reynolds number. 相似文献
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First and Second Law Analysis for the MHD Flow of Two Immiscible Couple Stress Fluids between Two Parallel Plates
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This paper aims to analyze the heat transfer by the first and second laws of thermodynamics for the flow of two immiscible couple stress fluids inside a horizontal channel under the action of an imposed transverse magnetic field. The plates of the channel are maintained at constant and different temperatures higher than that of the fluid. The flow region consists of two zones, the flow of the heavier fluid taking place in the lower zone. No slip condition is taken on the plates and continuity of velocity, vorticity, shear stress, couple stress, temperature, and heat flux are imposed at the interface. The velocity and temperature distributions are derived analytically and these are used to compute the dimensionless expressions for the entropy generation number and Bejan number. The results are presented graphically. It is observed that the imposed magnetic field reduces the entropy production rate near the plates. 相似文献
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A fluid–solid conjugate heat transfer model is developed to analyze the characteristics of entropy generation for forced convective steady hydrodynamically fully developed laminar flow of a Newtonian fluid through a parallel plate channel filled with porous material by modulating the following parameters: substrate thickness, the ratio of thermal conductivity of wall to fluid, Biot number, the axial temperature gradient in the fluid, and Peclet number. The exteriors of both the walls are subjected to the thermal boundary conditions of the third kind. The mass and Brinkman momentum conservation equations in the fluidic domain and the coupled energy conservation in both the solid and fluidic domain are solved analytically using the local thermodynamic equilibrium model, so as to derive closed-form expressions for the velocity in the fluid and the temperature both in the fluid and solid walls in terms of relevant parameters. Suitable combinations of influencing factors, namely the geometric parameters of the system, fluid, flow, and substrate properties are identified for which global entropy generation rate is minimized. The findings may be helpful in the design of thermal systems frequently used in diverse engineering applications having heat transfer in the solid wall being a crucial parameter. 相似文献
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Todd A. Jankowski 《International Journal of Heat and Mass Transfer》2009,52(15-16):3439-3445
Entropy generation in fully-developed flow through a duct with heat transfer is discussed. Methods are presented to minimize entropy generation by adjusting the shape of the duct’s cross-section. Choosing a different cross-sectional shape allows for control of the competing fluid flow and heat transfer irreversibilities. By controlling the competing irreversibilities, the total entropy generation rate can be minimized. Given the flow rate, heat transfer rate, available cross-sectional area, and the fluid properties, a general design correlation is presented that allows for a determination of the optimal shape of a duct. 相似文献
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Cooling of a bluff body is a topic of interest for many engineers and scientists. Forced convection over the bluff body generates flow separation, which in turn affects the heat transfer characteristics and increases the irreversibilities involved in the system. In the present study, flow over a rectangular solid body with constant heat flux is considered. The governing flow and energy equations are solved in two‐dimensional space numerically using a control volume approach. In order to investigate the effect of the fluid properties on the heating process, three different fluids are taken into account. These are air, ethylene glycol and therminol. To determine the irreversibilities involved in the system, entropy analysis is carried out. It is found that fluid properties have considerable effect on the entropy generation. The entropy generation due to heat transfer well exceeds the entropy generation due to fluid friction. The surface temperature of the solid body highly depends on the cooling fluid employed. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Exergy loss measures ineffectiveness of a heat exchanger. Hence, it was experimentally found in a three-channel 1-1 pass plate heat exchanger (PHE). Air was made to flow in the central channel to get heated by water in the outer channels under conditions of counter and parallel flows. The plates had sinusoidal wavy surfaces having corrugation angle of 30°. Reynolds numbers were in the range of 650-2600 for air and 400-1650 for water. Bulk temperature of air was in the range from 46 °C to 63 °C and that of water in the range 70-75 °C. To avoid entropy generation paradox, two methods have been proposed. In the first method exergy loss is scaled on product of heat capacity rate of cold fluid and its inlet temperature, and in the other on maximum heat transfer rate. The second method helps in arriving at the conclusions more precisely. The experimental results have been compared with the results available in the literature for corrugated water-water PHE. The exergy loss in the sinusoidal PHE is found less than that in the rectangular wavy PHE for given flow conditions and may be attributed to less turbulence and better solid-fluid contact. 相似文献
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Xinhai Xu Penghua Guo Wenrui Liu Weikun Yang 《International Journal of Hydrogen Energy》2017,42(31):20316-20323
Heat transfer fluid is a critical component in a concentrating solar power plant. A large quantity of heat transfer fluid is required to transfer heat between the solar collector and the power block, thus it is crucial to select the most appropriate heat transfer fluid in order to maximize the system performance. The present study compared the performances of five molten-salt eutectic mixtures in regarding with the entropy generation rate and the Carnot efficiency of using them as heat transfer fluids. All the five molten-salt eutectic mixtures have thermal stability temperatures above 600 °C. Effects of the tube lengths in the steam generation heat exchanger and the receiver heat exchanger as well as the heat transfer fluid flow rate on both the entropy generation rate and the Carnot cycle efficiency were investigated. The results indicate that the carbonate salts has the worst performances compared to the other eutectic mixtures. The three chloride salts have slightly higher entropy generation rate and 5% higher Carnot efficiency than the Solar Salt. Therefore the three chloride salts are suggested to be used in advanced concentrating solar power tower plants as potential high temperature heat transfer fluids. 相似文献
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《International Journal of Thermal Sciences》2003,42(2):177-186
Second law characteristics of heat transfer and fluid flow due to forced convection of steady-laminar flow of incompressible fluid inside channel with circular cross-section and channel made of two parallel plates is analyzed. Different problems are discussed with their entropy generation profiles and heat transfer irreversibility characteristics. In each case, analytical expression for entropy generation number (NS) and Bejan number (Be) are derived in dimensionless form using velocity and temperature profiles. 相似文献
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The effect of local thermal nonequilibrium (LTNE) on the entropy generation and heat transfer characteristics in the magnetohydrodynamic flow of a couple-stress fluid through a high-porosity vertical channel is studied numerically using the higher-order Galerkin technique. The Boussinesq approximation is assumed to be valid and the porous medium is considered to be isotropic and homogeneous. Two energy equations are considered one each for solid and fluid phases. The term involving the heat transfer coefficient in both equations renders them mutually coupled. Thermal radiation and an internal heat source are considered only in the fluid phase. The influence of inverse Darcy number, Hartmann number, couple-stress fluid parameter, Grashof number, thermal radiation parameter, and interphase heat transfer coefficient on velocity and temperature profiles is depicted graphically and discussed. The entropy generation, friction factor, and Nusselt number are determined, and outcomes are presented via plots. The effect of LTNE on the temperature profile is found to cease when the value of the interphase heat transfer coefficient is high, and in this case, we get the temperature profiles of fluid and solid phases are uniform. The physical significance of LTNE is discussed in detail for different parameters' values. It is found that heat transport and friction drag are maximum in the case of LTNE and minimum in the case of local thermal equilibrium. We observe that LTNE opposes the irreversibility of the system. The corresponding results of a fluid-saturated densely packed porous medium can be obtained as a limiting case of the current study. 相似文献