Experimental Investigation of Water–Alcohol Mixtures as Working Fluids in a Closed-Loop Two-Phase Thermosiphon

Abstract

Inverters are a crucial component in electric vehicle drivetrains, and this work attempts to develop and study a thermal management system for inverter cooling. This study aims to develop a low-cost, simple, closed-loop two-phase thermosiphon (CLTPT) to operate as a pumpless loop for power inverter applications. Some alcohols, when mixed with water, show self-rewetting behavior during boiling. Three 2-propanol–water mixtures and three 1-butanol–water mixtures have been studied as working fluids and compared against pure water to ascertain the benefits of alcoholic mixtures on heat transfer performance. The CLTPT was operated in two distinct regimes: (1) heat pipe mode and (2) mixed mode, using a ball valve positioning. Based on the valve position, a stable thermosiphon operation is demonstrated. Effects of operating conditions like condenser coolant inlet temperature and input power level to the thermosiphon have also been investigated. Regarding evaporator plate temperature and heat transfer coefficient, the 15-wt% 2-propanol–water solution outperforms pure water and butanol–water mixture as a working fluid for most test cases. If heat transfer performance is preferred, water outperforms in terms of heat transfer coefficient compared to other fluids tested.