Convective Heat Transfer over a Flat Plate in Hypobaric Conditions

Abstract

Plants will likely be significant components of life support systems for future manned exploration missions to Mars. Design constraints make it necessary to maintain a greenhouse on Mars at pressures in the range of 0.1 to 0.25 of Earth standard pressure (101.3 kPa). The resistance to sensible and latent heat loss decreases with pressure, which may cause increased rates of plant evapotranspiration, leading to possible water stress of plants growing in hypobaric conditions. The objective of this research was to analyze the effect of pressure and air velocity on convective heat transfer from a flat plate in hypobaric conditions to simulate leaf convective heat transfer in a greenhouse on Mars. Convective heat transfer analysis was performed both theoretically and experimentally for a flat plate. A classical heat transfer model for both free and forced convection regimes was compared with data from controlled experiments. As predicted, external resistance was proportional to both pressure and air velocity. The thickness of the velocity boundary layer increased significantly at low pressures and air velocities less than 1 m s-1.