Thermodynamics HW Solutions 49

Thermodynamics HW Solutions 49 - Chapter 1 Basics of Heat...

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Unformatted text preview: Chapter 1 Basics of Heat Transfer Simultaneous Heat Transfer Mechanisms 1-96C All three modes of heat transfer can not occur simultaneously in a medium. A medium may involve two of them simultaneously. 1-97C ( a ) Conduction and convection: No. ( b ) Conduction and radiation: Yes. Example: A hot surface on the ceiling. ( c ) Convection and radiation: Yes. Example: Heat transfer from the human body. 1-98C The human body loses heat by convection, radiation, and evaporation in both summer and winter. In summer, we can keep cool by dressing lightly, staying in cooler environments, turning a fan on, avoiding humid places and direct exposure to the sun. In winter, we can keep warm by dressing heavily, staying in a warmer environment, and avoiding drafts. 1-99C The fan increases the air motion around the body and thus the convection heat transfer coefficient, which increases the rate of heat transfer from the body by convection and evaporation. In rooms with high ceilings, ceiling fans are used in winter to force the warm air at the top downward to increase the air...
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