Effect of electric field, mass flow rate, and subcooling degree on subcooled flow boiling in a micro-slit channel

Abstract

This study investigated the design and cooling performance of a micro-slit-channel heat sink for electrical device cooling. The subcooled flow-boiling performance of a dielectric liquid, HFE-7000, was experimentally characterized. A flat electrode made from stainless steel with 10 narrow slits, each 1 mm width and 17 mm long, was placed at 600 μm above the heated surface to generate a high electric field. The flow boiling heat transfer performance of an electroplated diamond surface was evaluated. Four electric field intensities from 0 to −5 kV/mm, three mass flow rates from 1.83 to 4.8 g/s, and four inlet subcooling from 5 to 25 K were tested at an atmospheric system pressure. Four flow boiling patterns were categorized using a high-speed camera: single-phase flow, subcooled nucleate boiling, saturated nucleate boiling, and local dry out boiling. The maximum critical heat flux (CHF) and heat transfer coefficient were 95 W/cm2 and 30 kW/m2K, respectively, for mass flow rate of 4.83 g/s, electric field of −5 kV/mm, subcooling degree of 9 K, and mass flow rate of 4.83 g/s. A semi-empirical prediction of the CHF exhibited good agreement with the experimental results within ±18 %.