Single-phase and boiling cooling of small pin fin arrays by multiple slot nozzle suction and impingement

Experimental measurements of forced convection single-phase and boiling heat transfer from pin fin arrays were made using fluorocarbon liquid FC-72. Liquid flow was directed to and from the pin fin arrays by multiple slot nozzles, alternately providing suction and impingement flow. Rectangular pin fin arrays having equal width and spacing of 0.1 and 0.2 mm and aspect ratios from 1 to 5 were machined from 1 cm square copper blocks. The multiple slot nozzles featured alternating inlet and outlet channels 1-mm wide on a 2-mm pitch. Flow rates of 1.25 to 10 cm ³/s (0.075 to 0.6 l/min) were tested, resulting in inlet and outlet velocities of 0.05 to 0.4 m/s and pin fin array velocities from 0.05 to 4.0 m/s. The range of flow rates and pin fin geometries provided a single-phase thermal conductance as high as 38.5 kW/m²·K and critical heat flux as high as 369 W/cm². At a fixed pin fin aspect ratio and liquid flow rate, reducing pin fin width from 0.2 mm to 0.1 mm increased single-phase heat transfer by an average of 7%, while critical heat flux remained constant. Correlations of the single-phase heat transfer coefficient and critical heat flux as functions of liquid flow rate, pin fin aspect ratio and width are provided