Numerical and experimental study on heat transfer performance and surface temperature non-uniformity improvement in liquid nitrogen spray cooling

This study combines numerical simulations and experimental investigations to analyze the heat transfer characteristics of a liquid nitrogen (LN2) spray cooling system. The factors affecting system performance, including nozzle outlet diameter, spray cone angle, and spray height, were analyzed in relation to surface temperature distributions. The simulated results closely align with experimental data, showing a maximum deviation of 2.7%, which validates the numerical reliability of the two-phase flow model based on the Euler-Lagrange method. Experimental findings indicate that the spray cone angle of subcooled LN2 closely resembles that of kerosene under identical operating conditions. Our previous study found that a larger spray cone angle reduces temperature non-uniformity. Consequently, a wide-angle nozzle was designed to achieve a maximum spray cone angle of 128° at 5 MPa pressure by converting axial momentum into tangential momentum via the use of three tangential holes. As a result, the surface temperature non-uniformity (STNU) decreased by approximately 50 °C when the spray cone angle increased from 20° to 120° for a nozzle with a 4 mm outlet diameter. The study also demonstrates that heat transfer performance worsens as spray height increases, but STNU improves, indicating that heat transfer enhancement and STNU improvement cannot be achieved simultaneously. Increasing the spray height from 93 mm to 186 mm reduced heat transfer intensity, while the decrease in STNU enabled the identification of optimal spray heights that minimized STNU by over 16.8% and enhanced thermal uniformity.