Experimental correlation investigation of liquid nitrogen spray cooling

In this study, influence factors of liquid nitrogen spray cooling, including the parameters of the nozzle, the area of the heat sink, and the flow rate of liquid nitrogen, were investigated experimentally. On the basis of experimental data, experimental dimensionless correlations were obtained. It was shown that the error of correlation with only the Reynolds number (Re) and Prandtl number (Pr) was too low to predict the Nusselt number (Nu). With Re, Pr, the boiling number (Bg), and the Jacob number (Ja), while the error of correlation decreased, the experimental data deviated considerably from the fitting line by the correlation, which was still not suitable for prediction. The reasons for the experimental data’s deviation were that the uniformity of the droplet distribution varied with the nozzle aperture, a change in the heat exchange area resulted in the formation of a local gas film, the droplet splash caused by a change in the flow rate influenced the heat exchange. The correlation obtained with Re, Pr, Bg, Ja, and the effective of spray mass flow flux η which was determined as the ratio of the liquid nitrogen mass flow rate involved in heat transfer to the uniform mass flow on the heat surface could be used to accurately predict Nu.