A long cylindrical rod with a diameter of 3.0 cm is placed in the air. The rod is heated by an electrical current so that the surface temperature is maintained at 200°C. The air temperature is 21°C. Air flows over the rod with a convective heat transfer coefficient of 5.0 W/m2-K. Consider the emissivity of the rod to be 0.92. Ignoring the end effects of the rod, determine the heat transfer rate per unit length of the rod (a) via convection and (b) via radiation.
Given: Ts = 200°C = 473 K; Tf = Tsurr = 21°C = 294 K; h = 5.0 W/m2-K; ? =0.92; D = 3.0
cm = 0.03 m
What will be an ideal response?
The surface area of the cylinder is A = ?DL = 0.09425L m2 , where L is the length of the
rod.
Convection:
Radiation:
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