Numerical study of the influence of the atmospheric pressure on the thermal environment in the passenger cabin

The cabin air pressure remains lower than the horizontal atmospheric pressure when the airplane is in flight. Air pressure is one of the parameters that must be taken into consideration while studying the thermal environment of an airplane cabin. There are still no reference values for aircraft cabins despite the fact that numerous studies on low pressure heat transfer have demonstrated the connection between convective heat transfer coefficient (CHTC) and air pressure. In this paper, a correction method for CHTC under low pressure conditions was established by using the dummy heat dissipation in the low-pressure cabin experiment. On this basis, a thermal environment simulation model was developed, then was applied to the simulation of a seven-row aircraft cabin containing 42 passengers, and the CHTC and heat loss of dummy surface in the cabin were obtained. Finally, the results of PMV calculated by using heat dissipation and air parameters at sampling points were compared. The results show that the modified CHTC can accurately reflect the cabin thermal environment under low pressure conditions, and the correction of CHTC can be realized by adjusting the turbulent Prandtl number, which is nonlinear correlated with the pressure. The simulation results of the thermal environment in the seven-row cabin show that the CHTC changes by about 42% before and after modification. The air pressure decreases during take-off, which reduces the average CHTC of the crew surface from 5.09 W/(m²·K) to 4.56 W/(m²·K), but the air temperature rises by about 0.2 °C as a whole. The deviation of PMV results calculated by using simulated heat loss data and using air parameters of measuring points in space is up to 0.5, but the latter is representative for calculating the thermal comfort level of the whole cabin.