多壳体凝汽器在非对称传热工况下的背压计算方法研究

基于凝汽器的传热原理和蒸汽流动的阻力特性,建立了求解多壳体凝汽器在非对称传热工况下的背压计算方法,以某核电机组三壳体凝汽器为例,计算了无连通管和有连通管两种情况下的各台凝汽器的背压,并详细讨论了连通管直径、海水温度以及热负荷对背压差的影响。

热超构材料的时间相关非互易传热性能

针对具有广泛应用前景的人工设计的非互易性热传递超构材料,本文利用参数失配准则,开展了瞬态条件下热超构材料的非互易性热传递研究,推导出了时间相关非互易性热传递超材料存在的充分必要条件,并进行了模拟验证。研究表明:热导率恒定、密度比热容梯度分布的系统存在非互易热传递现象,这将为宏观热二极管、热管理及热计算等领域的发展提供动力。

风冷热泵用新型干式蒸发器的实验研究

针对传统折流板管壳干式蒸发器存在换热性能不佳和阻力大的问题,基于非对称空间传热理念,提出一种新型顺紊流自支撑型干式蒸发器,并将其装配在风冷热泵上进行实验测试研究。测试结果表明:风冷热泵的制冷量为52.33k W,制冷性能系数为2.47,制热量为63.32 k W,制热性能系数为3.0。实验对比配置传统折流板管壳干式蒸发器的同型号风冷热泵,其干式蒸发器的换热面积减少33.3%,制冷性能系数提高6.0%,制热性能系数提高15.8%,制冷剂充注量减少7.1%。

Heat transfer analysis and experimental study of unequal diameter twin-roll casting process for fabricating Cu/Al clad strips

Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the asymmetric heat transfer characteristics of Cu/Al clad strips fabricated by UDTRC.The effects of roller velocity ratio,Cu strip thickness,and inclination angle on the kissing point position,as well as the entire temperature distribution are obtained.The heat transfer model is established,and the mechanism is discussed.The Cu strip and rollers are found to be the main causes of asymmetric heat transfer,indicating that the roller velocity ratio changes the liquid zone proportion in the molten pool.The Cu strip thickness determines the heat absorption capacity and the variations in thermal resistance between the molten Al and the big roller.The inclination angle of the small roller changes the cooling time of big roller to molten Al.Moreover,the microstructure of Al cladding under different roller velocity ratios is examined.The results show significant grain refinement caused by the shear strain along the thickness direction of Al cladding and the intense heat transfer at the moment of contact between the metal Al cladding and Cu strip.

Peristaltic transport of MHD Williamson fluid in an inclined asymmetric channel through porous medium with heat transfer

The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.

Peristaltic transport of hydromagnetic Jeffrey fluid with temperature-dependent viscosity and thermal conductivity

In this paper, we investigate the effects of variable viscosity and thermal conductivity on peristaltic flow of Jeffrey fluid in an asymmetric channel. The inclined magnetic field, viscous dissipation and Joule heating are also considered. Wave frame and long wave-length approximations are made to formulate the problem. Pressure gradient, pressure drop per wavelength, velocity and temperature profiles are calculated analytically and discussed graphically. Comparison is made with the previous work for reliability.