Thermodynamics HW Solutions 8

Thermodynamics HW Solutions 8 - Chapter 1 Basics of Heat...

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Chapter 1 Basics of Heat Transfer where kW 4.17 kJ/h 15,000 kW 4 kJ/h 400 , 14 kJ/h 360 40 kW 1 W 100 10 gain heat people lights = = = = × = = × = Q Q Q & & & Substituting, & . Q cooling 9.17 kW =++ = 144 1 7 Thus the number of air-conditioning units required is units 2 83 . 1 kW/unit 5 kW 9.17 ⎯→ = 1-27E The air in a rigid tank is heated until its pressure doubles. The volume of the tank and the amount of heat transfer are to be determined. Assumptions 1 Air is an ideal gas since it is at a high temperature and low pressure relative to its critical point values of -141 ° C and 3.77 MPa. 2 The kinetic and potential energy changes are negligible, . 3 Constant specific heats at room temperature can be used for air. This assumption results in negligible error in heating and air-conditioning applications. ΔΔ pe ke ≅≅ 0 Properties The gas constant of air is R = 0.3704 psia.ft 3 /lbm.R = 0.06855 Btu/lbm.R (Table A-1). Analysis ( a ) We take the air in the tank as our system. This is a
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This note was uploaded on 01/14/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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