Dielectric Flow Boiling in Meso-scale Pin-Fin-Enhanced Channels

Abstract This study investigates flow boiling in pin-fin heat sinks, aiming to bridge the gap in the literature between micro-scale and macro-scale geometries. The focus is on hydraulic diameters ranging from 880 micro-meter to 4.25 mm. Experiments were conducted on seven distinct pin-fin coldplate configurations, covering a wide range of mass fluxes from 70 kg/m2s to 2500 kg/m2s. The dielectric fluid HFE-7200 was used, with uniform heat fluxes applied up to 185 W/cm2, corresponding to a total heat dissipation of 1.85 kW. The thermal-hydraulic performance of the coldplates was characterized, and high-speed flow visualization was employed to identify flow regimes and elucidate the mechanisms underlying critical heat flux (CHF). Over 540 data points and 840 flow visualization videos were analyzed. The results led to the development of new empirical correlations for two-phase pressure drop, heat transfer coefficients, and CHF specific to dielectric flow boiling in meso-scale pin-fin coldplates.