Passive control and enhancement of low Reynolds number slot jets through the use of tabs and chevrons

Liquid micro-jets are emerging as candidate primary or secondary heat exchangers for the thermal management of next generation photonic integrated circuits (PICs). However, the thermal and hydrodynamic behavior of confined, low Reynolds number liquid slot jets is not yet comprehensively understood. This investigation experimentally examined jet outlet modifications, in the form of tabs and chevrons, as techniques for passive control and enhancement of single- phase convective heat transfer. The investigation was carried out for slot jets in the laminar flow regime, with a Reynolds number range, based on the slot jet hydraulic diameter, of 100 to 500. A slot jet with an aspect ratio of 4, and a fixed confinement height to hydraulic diameter ratio (H/Dh) of 1 was considered. Local surface heat transfer and veloc- ity field characteristics were measured using infrared ther- mography and particle image velocimetry techniques. It was found that increases in area-averaged Nusselt number of up to 31 percent compared to the baseline case, could be achieved without incurring additional hydrodynamic losses. It was also determined that the location and magnitude of Nusselt number and velocity peaks within the slot jet stagnation region, could be passively controlled and enhanced through the application of outlet tabs of varying geometry and location.