HEAT-TRANSFER FROM RADIATIVELY HEATED MATERIAL IN A LOW-REYNOLDS-NUMBER MICROGRAVITY ENVIRONMENT

A mathematical model of the transient three-dimensional heat transfer between a slowly moving ambient gas stream and a thermally thick or th in flat surface heated by external radiation in a microgravity environ ment is presented. The problem is motivated in part by fire safety iss ues in spacecraft. The gas phase is represented by variable property c onvection-diffusion energy and mass conservation equations valid at lo w Reynolds numbers. The absence of gravity and low Reynolds number tog ether permit the flow to be represented by a self-consistent velocity potential determined by the ambient velocity and the thermal expansion in the gas. The solid exchanges energy with the gas by conduction/con vection and with the surroundings by surface absorption and re-emissio n of radiation. Heat conduction in the solid is assumed to be one dime nsional at each point on the surface as a consequence of the limited t imes (of order of 10 seconds) of interest in these simulations. Despit e the apparent simplicity of the model, the results show a complex the rmally induced flow near the heated surface. The thermal exchange betw een the gas and solid produces an outward sourcelike flow upstream of the center of the irradiated area and a sinklike flow downstream. The responses of the temperature fields and the associated flows to change s in the intensity of the external radiation and the ambient velocity are discussed.