An experimental study on the effects of nozzle and surface geometry in fc-72 jet cooling

In this study, a spray cooling device for electronic components was investigated. Dielectric fuid (FC-72) was sprayed at 50°C through five nozzles (4.243mm spacing). The nozzles are of diameters 0.17, 0.23 or 0.41mm. Volume flow rate varied from 24.5 to 99.1ml/min. Two grooved surfaces and a smooth surface were tested, and the heated area was 12 - 12mm ². The larger nozzles yielded greater heat transfer coefficients at high heat fluxes (300 600kW/m ²). However, smaller nozzles result in greater dry-out heat fluxes and greater heat transfer coefficients at heat flux < 300kW/m ². The C4 surface, having parallel grooves of 0.4mm depth, improved the spray cooling performance by up to 80% as compared with the smooth suface. Its thermal resistance is 0.11 0.12K/W at 99.1ml/min flow rate, in the range of 85 130W heat input. A new correlation of spray cooling, accounting for the contributions of nucleate boiling and spray convection, is proposed. For data of FC-72 in the range of Re = 856 6188, Bo = 0.19 5.70, We = 25.2 3541.3, the predicted h-values agree with experimental data of the smooth surface within ±25%.