Experimental research on heat transfer characteristics of spray cooling under swing excitation

For the application of spray cooling in aircraft, it is necessary to further scientifically demonstrate whether high-intensity external excitation adversely affects the heat transfer characteristics. In this paper, a swing spray cooling experimental device is established to systematically study the heat transfer stability of spray cooling under different swing excitation conditions. The experimental results show that swing excitation leads to fluid accumulation in the spray chamber, which intensifies unsteady flow and significantly deteriorates heat transfer stability. The amount of fluid accumulation is positively correlated with swing amplitude(θ = 0° to ± 135°) and negatively correlated with swing frequency(f = 0 Hz to 1.67 Hz), in the case of θ = 135° and f = 0.5 Hz, the maximum fluid accumulation depth reaches 9.50 cm. Fluid accumulation causes continuous fluctuations in wall temperature and heat flux during the swing process. The stronger the swing excitation, the more significant the fluctuations, in the case of θ = 135° and f = 0.5 Hz, the wall temperature of SSCF is 15.86 % higher than that of CSSC. Particularly, when the swing of the spray chamber stops, two significant abrupt heat transfer events occur, accompanied by a large spray height(h = 34.7 mm to 44.7 mm). These events are attributed to a sudden increase in accumulated fluid inertial force and the synergistic effect of droplet impact heat transfer and convective heat transfer of the accumulated fluid, respectively. Among all the spray methods, inverted spray cooling not only ensures cooling capacity equivalent to that of vertical downward spray but also significantly mitigates the impact of fluid accumulation on heat transfer stability.