Jet impingement boiling of a dielectric coolant in narrow gaps

An experimental investigation into the effect of the chip-to-orifice gap was conducted for jet impingement boiling of FC-72 at the back surface of a 6.5 mm square thermal chip on a 28 mm square ceramic substrate. Four different types of jets were used, all of them employing a single 0.50 mm diameter orifice. A fixed position jet impingement pin with the orifice centered on a flat face measuring 7.62 mm on an edge was used as a base case. This jet supported a heat flux of about 120 W/cm² at a reasonable flowrate. Variable position jet impingement pistons were shown to perform as well as, but no better than the base case. Additional tests were conducted to investigate performance with variation in the chip-to-orifice gap. Thermal performance was found to be insensitive to the gap at large spacing, but below some specific gap it degraded with decreasing gap. A sudden jump in the chip temperature was discovered to occur at a specific gap. This gap length was found to vary with jet flowrate