喷雾腔压力及喷嘴孔径对相变喷雾冷却性能的影响

Influences of spray chamber pressure and nozzle bore diameter on spray cooling performance

为了满足大功率激光器件高热流密度及低表面温度的冷却需求，以R22为冷却工质，实验研究了在闭式系统中改变喷雾腔压力及喷嘴孔径对相变喷雾冷却中临界热流密度、冷却温度等冷却性能的影响，实验结果表明：在喷雾人口压力为0．8MPa，喷雾高度为22mm，人口温度为-3℃的实验条件下，当喷雾腔压力在0．2～0．4MPa范围内变化时，随着喷雾腔压力的升高，临界热流密度值（CHF）先增大后减小，存在最优的临界热流密度，冷却壁面温度随着喷雾腔压力的升高而上升；当改变喷嘴孔径时，CHF存在最优值，过小及过大的孔径均会影响喷雾冷却性能；当喷嘴孔径为0．4mm，喷雾腔压力为0．34MPa时，CHF值最高，为276．1W·cm-2，其对应的被冷却表面温度为26．8℃，表面换热系数为66640W·m-2·K-1。

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 in- crease of spray chamber pressure. The maximal CHF of 276, 1 W cm-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 coef- ficient was 66 640 W m-2 K-1. Bigger or smaller nozzle diameter would weaken the spray cooling performance.