An experimental investigation of pressure gradients due to temperature gradients in small diameter tubes

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstraact is included in .pdf document. Results of an experimental investigation of pressure gradients due to axial temperature gradients in small diameter tubes are presented. The tests, which covered the region of Knudsen numbers (based on tube inside radius) of 0.01 to 6, indicate good correlation with theory. It is of value to note that this correlation was obtained by using [Delta]T equal to the temperature difference between the hot and cold ends of the tubes and T[subscript ave] equal to the average of these two temperatures. In contrast, theory would dictate obtaining the temperature variation along the length of the tube and applying the formulas to small incremental [Delta]T's, then summing to get the total effect. Therefore, for normal laboratory conditions where pressure gradient corrections are to be computed, it is sufficient to record only the temperatures at the hot and cold ends rather than having to obtain a number of temperature readings along the tube. In order to apply pressure corrections easily and rapidly, a system of correction curves is given. To simplify the procedure, the tube cold end temperature was assumed to be 80[degrees]F, and the correction curves drawn accordingly. However, for different laboratory conditions a similar system of curves could be drawn and used.