Chapter 12 Radiation Heat Transfer12-86The average mean radiation temperature during a cold day drops to 12°C. The required rise in the indoor air temperature to maintain the same level of comfort in the same clothing is to be determined. Assumptions1 Air motion in the room is negligible. 2 The average clothing and exposed skin temperature remains the same. 3 The latent heat loss from the body remains constant. 4 Heat transfer through the lungs remain constant. PropertiesThe emissivity of the person is 0.95 (from Appendix tables). The convection heat transfer coefficient from the body in still air or air moving with a velocity under 0.2 m/s is hconv= 3.1 W/m2⋅°C (Table 12-3). AnalysisThe total rate of heat transfer from the body is the sum of the rates of heat loss by convection, radiation, and evaporation, &&&&(&)QQQQQQQQbody, totalsensiblelatentlungsconvradlatentlungs=++=+++Noting that heat transfer from the skin by evaporation and from the lungs remains constant, the sum of the
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