Thermodynamics HW Solutions 967

Thermodynamics HW Solutions 967 - The rate of sensible heat...

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Chapter 12 Radiation Heat Transfer 12-84 Chilled air is to cool a room by removing the heat generated in a large insulated classroom by lights and students. The required flow rate of air that needs to be supplied to the room is to be determined. Assumptions 1 The moisture produced by the bodies leave the room as vapor without any condensing, and thus the classroom has no latent heat load. 2 Heat gain through the walls and the roof is negligible. Properties The specific heat of air at room temperature is 1.00 kJ/kg ⋅° C (Table A-15). The average rate of metabolic heat generation by a person sitting or doing light work is 115 W (70 W sensible, and 45 W latent). Analysis
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Unformatted text preview: The rate of sensible heat generation by the people in the room and the total rate of sensible internal heat generation are Chilled air Return air 15°C 25°C 150 Students Lights 4 kW W 500 , 14 4000 500 , 10 W 10,500 = persons) 150 W/person)( 70 ( people) of (No. lighting sensible gen, sensible total, sensible gen, sensible gen, = + = + = = = Q Q Q q Q & & & & & Then the required mass flow rate of chilled air becomes kg/s 1.45 = ° − ° ⋅ = Δ = C 15) C)(25 kJ/kg (1.0 kJ/s 5 . 14 sensible total, air T C Q m p & & Discussion The latent heat will be removed by the air-conditioning system as the moisture condenses outside the cooling coils. 12-64...
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