A large number of long tubes, each of diameter D, are placed parallel to each other and at...

A large number of long tubes, each of diameter D, are placed parallel to each other and at a center-to-center distance of s. Since all of the tubes are geometrically similar and at the same temperature, these could be treated collectively as one surface (Aj) for radiation heat transfer calculations. As shown in Fig. P13–108, the tube-bank (Aj) is placed opposite a large flat wall (Ai) such that the tube-bank is parallel to the wall. The radiation view factor, Fij, for this arrangement is given by

(a) Calculate the view factors Fij and Fji for s = 3.0 cm and D = 1.5 cm.

(b) Calculate the net rate of radiation heat transfer between the wall and the tube-bank per unit area of the wall when Ti = 900°C, Tj = 60°C, εi = 0.8 and εj = 0.9.

(c) A fluid flows through the tubes at an average temperature of 40°C, resulting in a heat transfer coefficient of 2.0 kW/m2·K. Assuming Ti, = 900°C, εi = 0.8 and εj = 0.9 (as above) and neglecting the tube wall thickness and convection from the outer surface, calculate the temperature of the tube surface in steady operation.