Abstract:

In order to deal with heat dissipation problems, such as high power, long-distance complex space layout and relative movement of heat sources, a high-performance flexible loop heat pipe (LHP) was designed and manufactured. With ammonia as the working fluid and polytetrafluoroethylene (PTFE) as the capillary wick of LHP, braided stainless steel metal hoses lined with smooth PTFE were coupled in the vapor and liquid lines, respectively. Using a thin film heater as the simulated heat source and the cooling circulating water as the heat sink, the thermal performance of LHP was experimentally tested and evaluated, including the startup, the power increment test, the system thermal resistance and the heat transport capability. The results showed that the LHP exhibited excellent startup characteristics and heat transfer performance, and the response to variable heat load was fast and stable. The LHP could achieve a maximum heat transfer capacity greater than 700W. The system thermal resistance was less than 0.01K/W, and the operating temperature was less than 35℃ under the effective transmission distance of more than 3.97m. To better assess the rationality of the LHP design, the pressure drop of each LHP component during steady state operation was calculated and compared. It was found that the diameter of the vapor line was the main influencing factor, and the reasonable selection of the PTFE hoses caused no significant increase in the system fluid flow resistance virtually, but could provide a good mechanical flexibility.

Key words: loop heat pipe, condensation, flexible, heat transfer, evaporation, two-phase flow

摘要：

面向大功率、远距离复杂空间布局和相对移动等散热问题，设计制作了一种高性能柔性环路热管。以氨为工质，采用聚四氟乙烯（PTFE）材料作为毛细芯，在气液传输管线中耦合了不锈钢编织内衬平滑型PTFE金属软管。以薄膜加热器作为模拟热源，冷却循环水作为冷源，实验测试和评估了热管的传热性能，主要包括启动、加热功率增量测试、热阻和传热量。结果表明，样机具有良好的启动特性和传热性能，对功率的切换响应迅速平稳。能够在超过3.97m有效传输距离下实现最大传热量大于700W，系统热阻小于0.01K/W，工作温度小于35℃。为了更好地评估环路热管（loop heat pipe, LHP）设计的合理性，对稳态运行时环路各部件流动压降进行了计算比较。分析发现气体管线管径是主要影响因素，软管的应用不会显著增加系统流动阻力，相对于其提供的柔性是占优的。

关键词: 环路热管, 冷凝, 柔性, 传热, 蒸发, 两相流