Thermodynamics HW Solutions 965

Thermodynamics HW Solutions 965 - Chapter 12 Radiation Heat...

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Chapter 12 Radiation Heat Transfer 12-81 A man wearing summer clothes feels comfortable in a room at 22 ° C. The room temperature at which this man would feel thermally comfortable when unclothed is to be determined. Assumptions 1 Steady conditions exist. 2 The latent heat loss from the person remains the same. 3 The heat transfer coefficients remain the same. 4 The air in the room is still (there are no winds or running fans). 5 The surface areas of the clothed and unclothed person are the same. Analysis At low air velocities, the convection heat transfer coefficient for a standing man is given in Table 12-3 to be 4.0 W/m 2 . ° C. The radiation heat transfer coefficient at typical indoor conditions is 4.7 W/m 2 . ° C. Therefore, the heat transfer coefficient for a standing person for combined convection and radiation is T room = 20°C Clothed person T skin = 33°C hh h combined conv rad 2 W/m . C =+ = + = ° 40 47 87 ... The thermal resistance of the clothing is given to be R cloth 22 clo m . C / W = 0.109 m . C / W == × ° ° 07 07 0155 ..
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This note was uploaded on 01/24/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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