Influences of spray chamber pressure and nozzle bore diameteron spray cooling performance

In order to meet the cooling requirements of high-power laser devices, the influences of spray chamber pressure and nozzle bore diameter on the spray cooling performance were experimentally studied in a closed spray cooling system with R22 as refrigerant. When the inlet pressure was 0.8 MPa, the spray height was 22 mm and inlet temperature was -3 ℃, the critical heat flux (CHF) increased firstly and then decreased with the increase of spray chamber pressure form 0.2 MPa to 0.4 MPa. In addition, there existed a maximal CHF value with the change of nozzle bore diameter which indicated the spray cooling effect would deteriorate with undersize or oversize nozzle bore diameters. And the cooling surface temperature increased with the increase of spray chamber pressure. The maximal CHF of 276.1 Wcm-2 was obtained with the nozzle diameter of 0.4 mm and the spray chamber pressure of 0.34 MPa, the corresponding cooling surface temperature was 26.8 ℃ and the heat exchange coefficient was 66 640 Wm-2K-1. Bigger or smaller nozzle diameter would weaken the spray cooling performance.