A solid plate, with a thickness of 15 cm and a thermal conductivity of 80?W/m•K, is being cooled at the upper surface by air. The air temperature is 10°C, while the temperatures at the upper and lower surfaces of the plate are 50 and 60°C, respectively. Determine the convection heat transfer coefficient of air at the upper surface, and discuss whether the value is reasonable or not for forced convection of air.
The upper surface of a solid plate is being cooled by air. The air convection heat transfer coefficient at the upper plate surface is to be determined.
Assumptions 1 Steady operating conditions exist. 2 Thermal conductivity of the plate is constant. 3 Heat conduction in solid is one-dimensional. 4 Temperatures at the surfaces remained constant.
Properties The thermal conductivity of the solid plate is given as k = 80 W/m?K.
Analysis Applying energy balance on the upper surface of the solid plate
The convection heat transfer of the air is
Discussion A convection heat transfer coefficient of 133 W/m2?K for forced convection of gas is reasonable when compared with the values listed in Table 1-5.
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