COMBINED RADIATION AND FREE CONVECTION HEAT TRANSFER IN A VERTICAL CHANNEL WITH ARBITRARY WALL EMISSIVITIES.

ANALYTICAL AND EXPERIMENTAL STUDIES OF COMBINED RADIATION AND FREE CONVECTION HEAT TRANSFER IN A VERTICAL CHANNEL IN AN ABSORBING AND EMITTING MEDIUM ARE CONDUCTED. A CHANNEL CONSISTING OF PARALLEL PLATES IS HEATED ASYMMETRICALLY, RENDERING BOTH THE WALL AND GAS RADIATION IMPORTANT. A SET OF FUNDAMENTAL EQUATIONS IS ESTABLISHED USING THE EXPONENTIAL WIDE-BAND MODEL AND THE GRAY-GAS MODEL WITH ARBITRARY WALL EMISSIVITIES. NUMERICAL RESULTS ARE COMPARED WITH EXPERIMENTAL ONES. WALL EMISSIVITIES ARE FOUND TO HAVE A MAJOR EFFECT ON THE COMBINED HEAT TRANSFER IN THIS STUDY. THE GRAY-GAS MODEL IS SHOWN TO FAIL TO PREDICT THE NEGATIVE NET ABSORPTION IN A GAS LAYER NEXT TO AN INSULATED WALL.