Construction and Experimental Analysis of Pump-Assisted and Capillary-Driven Single- and Dual- Evaporators Two-Phase Cooling Loops

Abstract

As electronics advance and require higher power densities, the demand for efficient cooling methods increases. Due to high heat flux capability, two-phase cooling systems may be applied to cool a wide variety of newly emergent technologies such as power electronics seen in electric-drive vehicles. This paper presents the experimental results of the cooling performance of a pump-assisted and capillary-driven two-phase loop, which utilizes a unique planar evaporator. Water was used as the working fluid. The evaporator is fed liquid by both mechanical and capillary pumping, while the vapor and liquid phases in the evaporator are separated by capillary force to prevent it from flooding. To reduce the heat leakage through the wall of the evaporator, stainless steel of a relatively low thermal conductivity was used as evaporator enclosure material, while copper was used as the heater body material. This paper discusses the effects of various operation variables of the two-phase cooling loop, such as dynamic and stepwise heat input, system pressure, liquid flow rate, and heat sink temperature on the cooling performance of the two-phase loop. Using a dual-evaporator setup in parallel and series was tested. The two-phase loop was tested up to 600 Watts (102 W/cm2) for a single evaporator and had a thermal resistance measured to be as low as 0.12 K-cm2/W. The dual-evaporator setup was tested up to 1200 Watts.