Question

the examinatiU to Heat Transfer" by Frank P. Incropera and Bavid F. Air entering a circular stainless steel tube D 50 mm outside diameter by d 45 mm inside diameter by L 5 m long atTa 20 C is heated by saturated steam at T100 c through which the tube passes. The thermal conductivity of the stainless steel tube kss .. 16.3 w/m° ? and the heat transfer coefficient at the interface between the tube and the steam h. 5000 W/m2 "c. On the axes provided in the diagram below, sketch the way in which the temperatures of the air flowing through the tube, the wall of the tube separating the air from the steam and the steam in which the tube is immersed vary (a) along the axis of the tube and (b) in the radial direction midway between the inlet and outlet of the tube. Tat Temperature T. Axlal DIstance (c) If the air mass flowrate m 0.01 kg/s, find the temperature at which air exits the tube To and the rate of heat transfer q (d) Adjusting the pressure of the steam has the effect of changing the steam temperature which modifies the rate of heat transfer. What would the temperature of the steam T, have be to produce air at a mass flowrate m = 1 kg/s and an exit temperature Tao 90°C, assuming that the air inlet temperature T, the heat transfer coefficient h, and the tube dimensions d, D and L remain fixed. In order to simplify the analysis, disregard the thermal resistance of the tube wall and the steam in which the tube is immersed.

Answer 1

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