Abstract: A visual closed-loop spray cooling test system was established for high heat flux cooling,with which the experimental phenomena in the visual chamber could be directly observed.The steady-state characteristics of the spray cooling system were investigated.In the test,the spray cone,angle,atomization effect,liquid film on the heat rejecting surface,and vapor/liquid interface in the spray chamber could be observed through the visual shell of the spray chamber.The effects of the heat flux value,the spray distance,the sink temperature,the subcooling degree of the return liquid on the heat transfer performance and the evaporation efficiency of the spray liquid were analyzed.