An Evaluation of Microtube Array Density for Liquid Delivery in Pump-Assisted Capillary Loop Coolers

Transportation electrification is accelerating the development of high-power-density electric drivetrain components. Such compact packages lead to a significant increase in the heat flux for power semiconductor devices and associated increases in thermal management costs. In this research, a flat plate pump-assisted capillary loop cooler (PACL) is investigated for power electronics device cooling applications. A porous wick at the heat source passively draws in liquid through a microtube array from a pumped parallel bypass flow through the compensation chamber. At high heat flux, the liquid evaporates at the wick surface, and vapor exits through the space between the microtube arrays. Coolers with two micro-tube array densities were fabricated, and their performance was experimentally measured using a flow loop. Cooler performance was found to be limited due to vapor flow resistance before reaching the wick’s capillary limit within experimental conditions. Nonetheless, a maximum heat flux of 650 W/cm² was achieved using water as a coolant with a 2 kPa pressure drop at a flow rate of 322 ml/min.