Experimental investigation of convective heat transfer in the aircraft cabin environment at low air pressure

Abstract

The heat transfer capacity of the cabin environment under low air pressure is significantly different from that under normal pressure. The existing research on the low-pressure environment of aircraft cabins has not provided a reliable convective heat transfer correlation to guide the design of the cabin thermal environment. This investigation evaluated the heat transfer in an actual aircraft cabin under different pressures. A laboratory test was designed in a cabin mockup with controllable boundary conditions for air temperature and pressure. Based on the measurement results, the quantitative effects of low pressure on the convective heat transfer coefficient (CHTC) of the heating surface were analyzed. According to the experimental results, the CHTC of the horizontal surface in natural convection increased from 3.26 W/(m2·K) to 5.10 W/(m2·K) when the heat flux increased from 100 W/m2 to 400 W/m2, and the CHTC dropped by 23–30% when the pressure dropped from 101 kPa to 61 kPa. With the same heat flux, the average CHTC value for the vertical plate was slightly lower than that for the horizontal heating plate under normal pressure, and the trend became significant as the air pressure decreased. In general, the average CHTC for forced convection was substantially higher than that for natural convection. Consequently, correlation equations for calculating natural and forced convection on horizontal and vertical plates under low air pressure were proposed, which will aid the design of the cabin thermal environment.