Answer to Question #256764 in Mechanical Engineering for Jnl

Question

Determine net radiant-heat exchange between the closed ends of a hollow cylinder 12-in. in diameter and 4-in. long. The ends are of Cr-Ni alloy with one end heated electrically to a temperature of 1900 °F and the other end maintained at 125 °F. The side wall of the cylinder is substantially nonconducting and reradiating.

Answer 1

Heat transfer can be expressed with "Fourier's Law"

$q = \frac{k }{s} A dT $

Thermal conducitivity $k = 11.3 \frac{W}{m}$ ,s =1

Area $A= \pi DL =\pi \times0.3048\times0.1016 =0.09728 m^2$

$q = 11.3\times0.09728\times(1900-125) =1951.19W =1.95kW $