连通微小通道环路热虹吸系统换热特性实验研究

Experimental study of heat transfer characteristics of loop thermosyphon with interconnected minichannel

针对芯片级散热场景,设计并搭建了两相环路热虹吸实验系统(TPLT),以R245fa作为工质,在冷凝器入口冷水温度为35℃、热流密度为10—162 W/cm2的工况下,研究了充液率对系统运行特性的影响,以及沟槽宽度为0.2—1.2 mm的连通平行微小通道(IPM)与平行微小通道(PPM)的沸腾换热性能。结果表明:40%是系统的合适充液率,过高的充液率导致冷凝器内部积液产生额外的蒸发器入口过冷度,过低的充液率则无法提供足够的循环流量;由于蒸发器水平放置时,TPLT系统流量启动存在滞后性,其瞬态启动特性会影响微小通道的稳态换热性能;0.2 mm槽宽的连通微小通道(IPM02,命名方式下同)具有较好的核态沸腾换热性能,因此启动阶段不存在温度过冲;最高测试热流密度下,IPM02和IPM07的传热系数相比于PPM分别提升约11%和5.7%,IPM12的传热系数则反而低于PPM。

For chip-level cooling scenarios,a two-phase loop thermosyphon system was designed and built using R245fa as the working fluid.Under the condition that the inlet cooling water temperature of the condenser was fixed at 35℃and heat flux ranged from 10 to 162 W/cm2,the influence of the filling ratio on system operating characteristics was first analyzed.Besides,the boiling heat transfer performance of interconnected parallel minichannels with slot width ranging from 0.2 to 1.2 mm as well as plain parallel minichannel(PPM)was investigated.The results indicate that the filling ratio 40%is a suitable filling ratio for the system,too high filling ratio causes internal liquid accumulation in the condenser and thereby additional subcooling at the evaporator inlet,while too low filling ratio is unable to provide enough circulation flow rate.Since there exists a delay in flow rate in a TPLT system when itsevaporator horizontally placed,the transient startup characteristics of the system will influence the steady heat transfer performance of minichannels.IPM02,who had relatively good nucleate boiling heat transfer performance,showed no temperature overshoot during the startup period.At the highest tested heat flux,IPM02 and IPM07 had an increase in boiling heat transfer coefficient of approximately 11%and 5.7%compared with PPM,however IPM12 had lower boiling heat transfer coefficient than PPM.The results of this paper provide guidance for the design of interconnected minichannels in TPLT systems.