Abstract:

The heat transfer performance of a compact three-dimensional oscillating heat pipe (3D-OHP) was investigated at vertical, horizontal and side orientation modes. The evaporator section of the 3D-OHP was fabricated by a 40 mm×40 mm×3.5 mm copper plate with nine parallel circular channels inside, and the condenser section was made of copper capillary tubes with inner and outer diameters of 2 and 3 mm, respectively. The capillary tubes were connected with the plate to form the 3D structure. Ethanol and deionized water were used as the working fluid with volumetric filling ratios from 20% to 70%. Two heat blocks were mounted on the copper flat evaporator to provide heating power inputs ranging from around 10 to 100 W. The results show that the 3DOHP could start-up and work well at the filling ratio range of 30% to 70% and had the best heat transfer performance at 30% filling ratio. In addition, the 3D-OHP had the lowest start-up temperature at the vertical orientation and the start-up temperature increased with the increase of filling ratio. The 3D-OHP still functioned at the horizontal orientation but had lower heat transfer performance than at the vertical orientation, and the reduction in filling ratio enhanced the performance. Compared with ethanol, the 3D-OHP charged with water had lower evaporation temperatures, higher evaporator temperature uniformity as well as heat transfer performance.

Key words: three-dimensional oscillating heat pipe, heat transfer performance, start-up, filling ratio

摘要：

设计制作了带平板蒸发器的紧凑型三维脉动热管，蒸发器的铜板尺寸为40 mm×40 mm×3.5 mm，内部含有平行圆通道，通道内径为2 mm；热管的冷凝段则由内、外径分别为2 mm和3 mm的铜毛细管构成。以乙醇和去离子水为工质，对该脉动热管在不同放置方式（竖直、水平和侧放）和体积充液率（20%～70%）下的启动和传热性能进行了比较研究。实验结果表明，充液率介于30%～70%之间时脉动热管大都能正常启动且稳定运行，表现出优异的传热性能。热管的启动温度随着充液率的提高而升高，启动温度由低到高排列顺序为竖直、侧躺和水平放置。竖直放置时该热管的传热性能优于水平放置，且两种放置情况下的传热性能总体上均随着充液率的减小而提高。相比于乙醇，使用去离子水时该脉动热管拥有更低的蒸发段平均温度，显示出更好的传热性能和均温性。

关键词: 三维脉动热管, 传热性能, 启动, 充液率