Air at 20°C with a convection heat transfer coefficient of 25?W/m2•K blows over a horizontal steel hot plate (k = 43 W/m•K). The surface area of the plate is 0.38 m2 with a thickness of 2 cm. The plate surface is maintained at a constant temperature of Ts = 250°C, and the plate loses 300 W from its surface by radiation. Calculate the inside plate temperature (Ti).
What will be an ideal response?
Air is blown over a hot horizontal plate which is maintained at a constant temperature. The surface also loses heat by radiation. The inside plate temperature is to be determined.
Assumptions 1 Steady operating conditions exist. 2 Heat transfer through the steel plate is one dimensional. 3 Thermal conductivity of the steel plate is constant.
Analysis The heat transfer by conduction through the plate is equal to the sum of convection and radiation heat loses:
Discussion Heat loss by convection is much more dominant than heat loss by radiation. If we had not accounted for the heat loss by radiation in our calculation, the inside plate temperature would be 252.7ºC, which is only 0.3ºC less than the actual value. In this case we could have neglected the heat loss by radiation.
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