EXPERIMENTAL STUDY ON HEAT TRANSFER CHARACTERISTICS OF SPRAY COOLING OF LIQUID NITROGEN

In this paper, the spray zone characteristics of two types of full cone nozzles were studied by setting up a liquid-nitrogen-spray-cooling experimental platform. The relationship between the heat flux and the superheat, the heat transfer coefficient and the superheat, and the heat flux and the heat transfer coefficient was analyzed by controlling the liquid nitrogen flow, orifice of nozzle, and heat sink area. The results showed that owing to the influence of bubbles during nucleate boiling, the superheat of liquid nitrogen spray near the point of the maximum heat transfer coefficient was lower than that near the point of the critical heat flux. Near the critical heat flux, the superheat increased rapidly and the heat transfer coefficient decreased sharply. The maximum heat transfer coefficient which achieved the critical heat flux was 15.62 × 104 W·m-2·K-1. The smaller diameter of nozzle orifice made the heat transfer process smoother, increasing the superheat of the maximum heat transfer coefficient and the critical heat flux. In addition, the maximum heat transfer coefficient and the critical heat flux increased with increase of the flow and decreased with increase of the area.