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1.
Heat transfer characteristics for a falling turbulent liquid film flow over a fin are analyzed using the conjugate convection-conduction theory. Numerical results are obtained from a simultaneous solution of the energy equations of the fluid and the fin. Results are presented for the fin temperature distribution, dimensionless heat transfer coefficients, local heat fluxes, and fin efficiencies. 相似文献
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A detailed analysis of the effect of local heat transfer distributions, which were determined experimentally, on temperature distributions in the fins and in the fluid between two adjacent fins of finned tube heat exchangers is presented. The heat transfer distributions, obtained by a mass transfer technique, prove to be very inhomogeneous over the fin surface, leading to variable results for fin efficiency calculated by the conventional method. In addition, the effect of temperature variation in the fluid, which is usually neglected in fin analysis, is shown in many cases to exert a very strong influence on fin efficiency and total heat flux. For the optimization of fin designs, a combined analysis of local heat transfer, conduction resistance in the fin and temperature variation in the passage is indispensable. 相似文献
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Rong-Hua Yeh 《加拿大化工杂志》1995,73(2):181-189
Employing fin parameter and tip temperature, a new concept with Lagrange's multiplier method is proposed to obtain the optimum width, height, heat dissipation, and efficiency of longitudinal fins for boiling heat transfer. A power-law type heat transfer coefficient is assumed in this analysis. Longitudinal fins of rectangular, convex parabolic, triangular, and concave parabolic profiles are first investigated. It is found that the optimum dimensions of a fin depends upon fin profile area, heat transfer coefficient at the fin base, and the thermal conductivity of the fin. Then, the least material fin profile is derived for each single heat transfer mode. To facilitate the thermal design of heat transfer components, simple mathematical expressions for the optimum dimensions of fins are presented in this study. 相似文献
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Rong-Hua Yeh 《加拿大化工杂志》1996,74(1):144-151
Considering a temperature dependent heat transfer coefficient, the optimum dimensions of longitudinal rectangular fins and cylindrical pin fins have been investigated analytically. Employing the parameters of fin thickness or fin diameter and tip temperatures, the optimum dimensions, heat dissipation, and efficiency of fins are obtained by Lagrange's multiplier method. It is shown that the fin efficiency of an optimum cylindrical pin fin is higher than that of an optimum rectangular fin. To facilitate the thermal design of the heat transfer components, very simple mathematical expressions for the optimum dimensions of fins are presented in this study. 相似文献
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焊接型板式传热器的紧凑性好、质量轻、传热性能好、初始成本低等优越性已越来越被人们所认识,因此人们纷纷对板式传热器内流动状态和传热机理展开研究。鉴于此,本文运用数值模拟软件Fluent对全焊接翅片板式传热器双流道进行模拟,在此基础上又进行了实验研究及实验数据与数值模拟的对比分析,得出不同结构参数和操作参数下翅片的传热系数和压力降,并分析翅片高度和翅片间距对翅片传热性能与流动阻力的影响。结果表明:①固定冷侧的入口速度和温度,热侧的传热系数和压降随之热侧入口速度增加而增大;②板间距一定时,翅片高度并非越高传热性能越好;③翅片间距越小,传热性能越好。 相似文献
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高效热管理技术是大功率微电子设备安全运行的可靠保障。为进一步强化高功率电子器件的冷却效果,本文提出了一种新型泡沫铝-微柱群复合热沉结构。采用实验和数值模拟相结合的方法对新型水冷泡沫铝-微柱群复合热沉内的流场分布、壁面温度分布、阻力系数、换热性能及柱鳍与泡沫铝间的耦合传热规律等开展了深入分析。研究结果表明,与传统微柱群热沉相比,20PPI泡沫铝-微柱群复合热沉的壁面最高温度大幅降低,平均换热性能提升了33.9%~41.5%。然而,微柱群内填充泡沫铝却导致流动阻力增大,增加了7.9~10.5倍。泡沫铝-微柱群复合热沉的强化换热机理为:微柱群热沉内填充高热导率泡沫铝提升了热沉整体的有效导热性能,热量可通过金属泡沫固体骨架迅速传递,同时多孔界面较强的传热能力能够保证热量及时被冷却流体散除。本文相关研究成果可为高热流密度电子器件散热装置的研发提供理论指导。 相似文献
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A simpler numerical model for plate‐fin heat exchangers with plain fins and serrated fins is presented, which incorporates the characteristics of fluid flow and heat transfer. The numerical simulations for heat exchangers with two fins at low Reynolds numbers are carried out by employing the simplified model and using the CFD code FLUENT. The results of heat transfer rate and pressure drop in numerical simulations are compared with the experimental results from the literature. It is shown that the results are in good agreement and the numerical model is reasonable and appropriate. The characteristics of fluid flow and heat transfer are analyzed and compared based on the numerical results. It is concluded that by applying the average heat transfer coefficient in practice, the heat transfer rate of the primary surface is overestimated, and the heat transfer rate and efficiency of the secondary surface are underestimated. The numerical modeling and conclusions provide the method and theoretical basis for the selection, optimization and analysis of plate‐fin heat exchangers. 相似文献
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The analysis presented is for laminar film boiling on a vertical surface treating the test section as a fin with the heat leakage from its ends. The formulation of the problem is accomplished as a conjugate between the thermal conduction in the test section and the phenomenon of film boiling on its lateral face. This approach revealed that the film boiling heat transfer coefficients, both local and average values, are profoundly influenced by the fin parameter. An explicit form of the equation is provided from the computer results to evaluate the film boiling heat transfer coefficient. 相似文献
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应用热 -质比拟技术 ,对间断环面槽肋片管束进行了传质与流动阻力实验 ,根据热 -质比拟关系得出传热结果 .分析了该种换热芯子在不同板间距时的传热与阻力特性 .与光板肋片管换热芯子比较 ,该种换热元件的传热与阻力都有很大提高 ,而阻力增加幅度更大 .实验结果为运用单位选用肋片管式换热器提供了依据 . 相似文献
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In present work, a stepping optimization algorithm is proposed for the geometric optimization of conical fin, and the heat transfer rate of the fin is treated as the objective function in the optimization algorithm. The conical fin is divided into finite elements which have different generatrix slopes, and the geometry of the conical fin is finally determined by ensuring that every divided element can maintain the maximum heat transfer rate. Based on the actual condition of every element of the fin, the heat conduction equation is solved step by step. The present result shows that the optimized conical fin has more heat transfer quantity and higher fin efficiency compared with those of some typical fins. Furthermore, the theoretical feasibility and the error analysis of present optimization algorithm have been performed as well. 相似文献
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采用FLUENT数值模拟方法,研究了平直翅片、平直开缝翅片、正弦波纹翅片和均匀倾角波纹翅片4种形式的翅片管换热器的空气侧流动和传热特性。分析出2种不同的波纹形式以及翅片开缝对翅片管换热器换热特性的影响。改变进口风速,在不同雷诺数的工况下,得到4种换热器的换热量Q、努塞尔数Nu、压降△P以及阻力因子f等与进口风速u和雷诺数Re的关系。结果表明进口风速增大,雷诺数增加,可显著提高换热器换热量,然而同样带来更多的阻力损失。翅片开缝对传热能力有明显的提升作用,波纹翅片在提高换热效率的同时阻力损失增加较小。 相似文献
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提出了一种可改善换热效率的百叶窗式纵翅片换热管的结构模型,对其进行简化,采用Fluent软件对换热管烟气侧流动与传热过程进行数值模拟,对比了两种百叶窗纵翅片与普通纵翅片的换热效率与压降,结果发现:百叶窗式纵翅片传热效果比普通纵翅片高130%以上。模拟了6组不同流体入口速度下传热与压降的变化情况,分析了百叶窗翅片间距与倾斜角度对传热与压降的影响,结果表明:入口速度越大,进出口温差越小,压降越大;翅片间距越大,进出口温差和压降都越小;翅片倾斜角度越大,换热效果相差不大,压降越大。搭建了简易实验平台对模拟结果进行验证。 相似文献
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研究了在高壁温条件下,空气为自然对流时,水平基面上的竖直矩形散热片组的传热性能,探讨了散热片的几何参数对流动和传热的影响。通过因次分析的方法,建立了以散热片间距为特征尺寸的自然对流传热准数关系式:Nu=01314(Gr’sPr)037 相似文献
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试验研究了空气在5种管径相同、不同翅片高度和翅片间距的立式花瓣管外螺旋流动的传热和流阻性能,分析出在试验范围内:花瓣管翅片高度相同时存在一最适宜翅片间距,使其传热性能最优;花瓣管翅片间距相同,翅片越高,其传热性能越好,而流动阻力损失也越大;管外系统压力越高,换热效果越好,且不会增加其流动阻力,这可为设计高效立式螺旋隔板花瓣管换热器提供参考依据。 相似文献
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In this present study, attempts were made to investigate the flow and heat transfer characteristics of finned tube with internal fins and external fins by experiment and numerical simulation. The test finned tube was installed in a single smooth tube and formed a shell-and-tube heat exchanger. The experiments were conducted in heat transfer test system with hot air in the tube side and cold air in the shell side. Overall heat transfer coefficients were calculated and heat transfer coefficients in the tube side were determined. Three-dimension computation was performed to predict the flow and heat transfer performance in the finned tube. The effects of external fin height and pitch of the finned tube on shell-side flow and heat transfer were studied by numerical simulation. The numerical results agree well with the measurements. The maximum differences between the present numerical results and the experimental data are approximately 6.9% for heat transfer coefficient and 4.7% for friction factor, respectively. The velocity and temperature fields are obtained to discern the mechanisms of heat transfer enhancement. Numerical results indicate that the steady and spatially periodic growth and disruption of vortices occur in external fin to fin region. 相似文献