Experiment on surface natural convection heat transfer of vertical plate under different pressures

When rising from the ground to space, aircraft will experience substantial changes in environmental parameters, which leads to the emergence of “super-hot”, “super-cold” and “thermal stratification” phenomenon of aircraft and airborne equipment. The objective of the present study is to obtain the key parameter-free convection heat transfer coefficient under different environmental pressures. In this study, experiments are carried out under different pressure conditions (0.000 1, 0.01,0.1, 0.2, 0.5, 1, 10, 50 kPa and atmospheric pressure) and different constant heat input (75,150, 300 W/m²) to measure the heat transfer of vertical plate. Then convection heat transfer coefficient can be obtained under different conditions by comparing heat loss between radiation and convection. The results indicate that: convection heat transfer coefficient is pretty low when absolute pressure is less than 1 kPa, which can be regarded as zero; when the absolute atmosphere is higher than 1 kPa, square relation is found between increasing convection heat transfer coefficient and increasing pressure; by processing environmental parameters with dimensionless method, the obtained criterion equation can be used between 1 kPa and 100 kPa.