CAJ | 학술논문

为了研究不同雷诺数下，工质的热物理性质对矩形微通道热沉内工质流动与换热的影响，该文建立了三维共轭传热模型，对微通道内单相层流的换热和流动特性进行了数值模拟研究，分析结果表明：当雷诺数为16时，与常物性工质相比，变物性工质具有较佳的换热性能以及更低的摩阻系数，此时基于工质常物性的数值假设会与实际情况偏离，而当雷诺数增加至333时，常物性工质与变物性工质的流动和换热性能具有较好的吻合，这在一定程度上解释了现有研究成果中矩形微通道热沉内工质流动与换热特性方面的试验结果与数值模拟之间存在偏差的现象。该研究为进一步改进数值模型精度提供了参考。
위료연구불동뢰낙수하，공질적열물이성질대구형미통도열침내공질류동여환열적영향，해문건립료삼유공액전열모형，대미통도내단상층류적환열화류동특성진행료수치모의연구，분석결과표명：당뢰낙수위16시，여상물성공질상비，변물성공질구유교가적환열성능이급경저적마조계수，차시기우공질상물성적수치가설회여실제정황편리，이당뢰낙수증가지333시，상물성공질여변물성공질적류동화환열성능구유교호적문합，저재일정정도상해석료현유연구성과중구형미통도열침내공질류동여환열특성방면적시험결과여수치모의지간존재편차적현상。해연구위진일보개진수치모형정도제공료삼고。
In order to study the impact of coolant with variable thermal property on the flow and heat transfer characteristics under different Reynolds numbers in rectangular microchannel heat sink, a three-dimensional conjugate heat transfer in a rectangular microchannel heat sink were analyzed numerically. Firstly, in general, a numerical model was established on the conditions that: 1) the microchannel heat sink was made by silicon, deionized water was applied as coolant fluid; 2) fluid was incompressible laminar steady flow; 3) the values of thermal conductivity coefficient and dynamic viscosity of the fluid varied with temperature, specific heat capacity at constant pressure was given; 4) the effect of radiation and natural convection heat transfer were ignored; and 5) in the control unit, constant heat flux at 70W/cm2 was applied in the heat sink surface, inlet fluid temperature was specified at 20oC, and Reynolds numbers were from16 to 333. Secondly, according to different thermal and physical properties, the average heat transfer coefficient of the channel wall was applied to compare the different heat transfer characteristics, and the surface friction coefficient was used to describe the variation of flow characteristics in microchannel, respectively. Finally, Fluent 6.3.26 was applied based on finite volume method for discrete equations, pressure-velocity coupling method used SIMPLE algorithms, and momentum and energy equations used second-order upwind scheme, respectively. In order to avoid errors caused by entrance effect, a ratio of 1.01 continuous grid was performed along the long side of the flow direction of the z axis. To verify the reliability of the established numerical model, the experimental data of resistance characteristics under intraductal laminar flow conditions performed using Shah and London was used to compare with this paper’s numerical calculation results. A good agreement was found. The simulation results indicated that: 1) When Reynolds number was 16, compared with coolant with constant thermal property, coolant with variable thermal property had better average convective heat transfer coefficient and average Nusselt number, which was particularly evident on the side wall of the micro channel. While, with the increase of Reynolds number, the gap between average convective heat transfer coefficient and average Nusselt number of the both coolants was significantly reduced. When Reynolds number increased to 333, the heat transfer characteristics of coolant with variable thermal property and coolant with constant thermal property were approximate. 2) For flow characteristics, when Reynolds number was 16, compared with coolant with constant thermal property, coolant with variable thermal property had significantly lower surface friction coefficient. When Reynolds number increased to 70, the gap between friction coefficients of the both coolants was reduced dramatically. However, coolant with variable thermal property still had obvious advantages. When Reynolds number increased to 333, with the approximate flow characteristics, the friction coefficient of coolant with variable thermal property was only slightly lower than that of the coolant with constant thermal property. 3) At low Reynolds number, the coolant numerical assumption based on the constant thermal property deviated from the actual situation, which explained the reason of the deviation of the experimental data and the simulation results to a certain extent.