微槽道脉动热管的启动及传热特性

Start-up and heat transfer performance of micro-grooved oscillating heat pipe

对竖直和水平放置情况下微槽道脉动热管（当量直径2.82 mm）的启动及传热性能进行了实验研究,并与内径分别为3.4 mm（1~#）、4.0 mm（2~#）和4.8 mm（3~#）的3个光管脉动热管进行了比较。实验工质为去离子水,充液率为50%。实验结果表明,竖直放置（底部加热）时,微槽道结构可以显著降低脉动热管的最小启动功率和启动温度,在约305 W的加热功率下其热阻分别比1#、2#和3#光管脉动热管下降41.7%、35.6%和30.9%,蒸发段壁面平均温度分别下降12.1、11.8和7.6℃;水平放置时,微槽道脉动热管在一定加热功率下能够正常启动,光管脉动热管难以有效运行。使用微槽道结构后,脉动热管显热和潜热传热能力的提高以及微槽道毛细作用利于冷凝液向蒸发段回流可认为是实现热管传热强化的主要原因。

The start-up and heat transfer performance of a micro-grooved tube oscillating heat pipe（OHP） and three other smooth tube OHPs were experimentally investigated and compared both at vertical and horizontal orientations. Deionized water was used as the working fluid with a volumetric filling ratio of 50%. The internal diameters（IDs） of three smooth tube OHPs were 3.4 mm（1~#）, 4.0 mm（2~#） and 4.8 mm（3~#）, respectively, and the internal hydraulic diameter of the micro-grooved OHP was about 2.82 mm. The results showed that at the vertical bottom heat mode, the micro-grooved OHP had lower heating power input and average evaporator temperature as compared to other smooth tube OHPs. At a heating power input of about 305 W, the reductions in the thermal resistance of the micro-grooved tube OHP were about 41.7%, 35.6% and 30.9% as compared to that of the 1#, 2#and 3# OHPs, and the corresponding reductions in the evaporator temperature were about 12.1℃,11.8℃ and 7.6℃, respectively. At the horizontal orientation, only the micro-grooved OHP could start up favorably at the relatively low heating power inputs within all these four tested OHPs and indicated better heat transfer performance. According to a qualitative analysis, the heat transfer enhancement of the micro-grooved OHP was mainly attributed to the sensible/latent heat transfer intensification as well as enhanced liquid backflow to the evaporator due to the microgroove-induced capillary action.