Abstract:

The loop heat pipe, abbreviated as the LHP, is an enhanced heat transfer element using phase change of working fluid for heat transfer. It is widely used in the waste heat recovery, the solar collectors and heat dissipation of the electronic devices. The performance of the capillary wick in the LHP evaporator is always focused. The 3D printing wick overcomes the limitations of uneven pore size distribution and high randomness of the sintered wick. Based on the characteristics of the gas-liquid two-phase flow in the LHP evaporator, the upper layer of the wick as the liquid-absorbing layer and the lower layer as the evaporating layer were defined. It was found that when the pore diameters of the evaporation layer are constant, increasing the pore size of the liquid absorbing layer will reduce the superheat in the evaporation zone; reducing the pore size of the liquid absorbing layer will cause dry burning in the evaporation zone, both of them will limit the heat transfer performance of the LHP. In addition, while the pore diameters of the absorbing layer are constant, increasing the pore size of the liquid-absorbing layer will cause heat leakage; reducing the pore size of the evaporating layer can strengthen the heat transfer performance of LHP. The composite capillary wick with a pore size of 100μm for the evaporation layer and 200μm for the absorbing layer has the highest heat transfer coefficient and the highest heat capacity.

Key words: loop heat pipe, phase change, heat transfer, 3D printing, composite material

摘要：

环路热管（loop heat pipe，简称LHP）是一种利用工质相变进行热量传递的强化传热元件，广泛应用于余热回收、太阳能集热器以及电子器件散热等。而LHP蒸发器内毛细芯对其工作性能具有决定作用，3D打印毛细芯可克服烧结毛细芯孔径分布不均且随机性高的局限性。本文根据LHP蒸发器内气液两相的流动特点，将3D打印毛细芯的上层定义为吸液层，下层定义为蒸发层，并对其上下层孔径的配比进行研究后发现：在本文所研究的工况下，当蒸发层孔径一定时，增大吸液层孔径会使蒸发区内过热度降低；减小吸液层孔径会使蒸发区内出现干烧现象，二者皆会限制LHP的传热性能。此外，当吸液层孔径一定时，增大蒸发层孔径会造成热泄漏，减小蒸发层孔径可强化LHP在高负荷下的传热性能。蒸发层孔径为100μm、吸液层孔径为200μm的复合毛细芯具有更高的传热系数和热负荷。

关键词: 环路热管, 相变, 传热, 3D打印, 复合材料