Parametric optimization of ambient and cryogenic loop heat pipes using multiple linear regression method

Abstract

In the design and optimization of ambient and cryogenic loop heat pipes (ALHPs and CLHPs), the cost for optimizing every parameter may be very high. Additionally, in cryogenic spacecraft applications, the resources allocated to the thermal control system are very limited. Therefore, it is crucial to identify and optimize the parameters that have a greater impact on the overall performance. In this paper, a thermal resistance network model for LHP was established. The model was validated experimentally using an ethylene-CLHP and by using experimental data of an ammonia-ALHP and a nitrogen-CLHP reported in the literature. The model was then used to comprehensively investigate the impact of boundary and inherent parameters on the operational performance of nitrogen-CLHPs in the 70–110 K temperature range, ethylene-CLHPs in the 150–250 K temperature range, and ammonia-ALHPs in the 250–400 K temperature range. Standardized coefficients were obtained by multiple linear regression to compare the relative importance of the influence of each parameter on the evaporator temperature, serving as an optimization criterion for identifying the most significant parameters for LHP optimization with different working fluids. It was found that most parameters affect the operating performance in the same manner for ALHPs and CLHPs, while the length of wick and compensation chamber had opposite effects on ALHPs and CLHPs. Finally, modified strategies for parameter optimization and design of ALHP and CLHP were proposed and an optimization case for an ethylene-CLHP was presented.