Chapter 1 Basics of Heat Transfer1-105A 1000-W iron is left on the iron board with its base exposed to the air at 20°C. The temperature of the base of the iron is to be determined in steady operation. Assumptions1Steady operating conditions exist.2The thermal properties of the iron base and the convection heat transfer coefficient are constant and uniform. 3 The temperature of the surrounding surfaces is the same as the temperature of the surrounding air. PropertiesThe emissivity of the base surface is given to be ε= 0.6. AnalysisAt steady conditions, the 1000 W energy supplied to the iron will be dissipated to the surroundings by convection and radiation heat transfer. Therefore, &&&QQQtotalconvrad1000 W=+=where WK)293(0.7K)293()mK)(0.02W/m(3522conv−=−⋅=Δ=sssTTThAQ&and W]K)(293[100.06804]K)(293)[TKW/m10)(5.67m0.6(0.02)(44844s428244rad−×=−⋅×=−=−−sossTTTAQεσ&Iron 1000 W Substituting, ]K)(293[1006804.0)K293(7.0W1000448−×+−=−ssTTSolving by trial and error gives C674K947
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