EXPERIMENTAL AND THEORETICAL INVESTIGATION OF HEAT TRANSFER THROUGH GASES CONTAINED BETWEEN TWO VERTICAL COAXIAL CYLINDRICAL SURFACES AT DIFFERENT TEMPERATURES.

Heat transfer through gases enclosed between two vertical coaxial cylindrical surfaces maintained at different temperatures is examined experimentally. The inner surface is an electrically heated tungsten wire enclosed in an outer glass tube, and the temperature difference between the two surfaces is varied up to about 700 degree C. Argon and nitrogen are used as test gases at various pressures up to about one atmosphere in columns of different dimensions. It is found that almost radial heat flow conditions exist for most of the control region of the column and the end effects are confined only in the corner regions, and the depths to which these penetrate are approximately equal to the diameter of the outer tube as long as Rayleigh number ranges between 55 to 4,400. Based on this physical model for the heat transfer, an analytical treatment of the phenomenon is developed.