R134a闭式喷雾冷却传热性能实验研究

Experimental Study on Heat Transfer Performance of Closed-loop Spray Cooling Using R134a

本文搭建了以R134a为工质的闭式喷雾冷却系统实验台,通过实验分析了稳态下制冷剂流量、过冷度和充注量对传热性能的作用规律,其中制冷剂流量范围为0.20~0.25 L/min、过冷度范围为5~8℃、充注量范围为0.95~1.25 kg。研究表明:在制冷剂流量为0.184 L/min、充注量为0.95 kg条件下,实验获得最大热流密度为105.25 W/cm^(2)、最大表面传热系数为2.54 W/(cm^(2)·℃)。低热流密度(45.93~72.55 W/cm^(2))条件下,随着制冷剂流量、过冷度和充注量的增大,表面传热系数总体呈上升趋势;高热流密度(84.02~105.25 W/cm^(2))条件下,随着流量的增大,表面传热系数逐渐增大,而随着过冷度及充注量的增大,表面传热系数先增大再趋于稳定。雅各布数随着制冷剂充注量的增大逐渐减小,这对高热流密度下表面传热系数的提升不利,存在一个最佳充注量使得闭式喷雾冷却系统传热性能最佳。

In this study,a R134a closed-loop spray cooling system was built to investigate the effects of flow rate,subcooling degree,and refrigerant charge on the steady spray cooling heat transfer performance.The experimental flow rate ranged from 0.20 to 0.25 L/min,the subcooling degree ranged from 5 to 8℃,and the refrigerant charge ranged from 0.95 to 1.25 kg.Results show that at a flow rate of 0.184 L/min and refrigerant charge of 0.95 kg,the maximum heat flux and surface heat transfer coefficient were 105.25 W/cm^(2) and 2.54 W/(cm^(2)·℃),respectively.At low heat flux(45.93-72.55 W/cm^(2)),with the increase in flow rate,subcooling degree,and refrigerant charge,the surface heat transfer coefficient,overall,increased.Under higher heat flux(84.02-105.25 W/cm^(2)),the surface heat transfer coefficient increases gradually with the increase in flow rate.The surface heat transfer coefficient initially increased and then stabilized as the refrigerant charge increased.In addition,the Jacob number Ja decreases with an increase in charge,which is unfavorable for the improvement of the surface heat transfer coefficient at higher heat flux.There is an optimal refrigerant charge to maximize the heat transfer performance of the closed spray cooling system.