申論題

6. A standard schedule 40, 2-in steel pipe (inside diameter 2.067 in and wall thickness 0.154 in) carrying steam is insulated with 2-in of 85% magnesia covered in turn with 2-in of cork. Estimate the heat loss per hour per foot of pipe if the inner surface of the pipe is at 250°F and the outer surface of the cork is at 90°F. The thermal conductivities ( in Btu/hr ㆍ ftㆍ°F) of the substances concerned are: steel, 26. 1； 85% magnesia, 0.04； cork, 0.03. (10%)