Thermodynamics HW Solutions 6

# Thermodynamics HW Solutions 6 - Chapter 1 Basics of Heat...

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Chapter 1 Basics of Heat Transfer 1-20 A house is heated from 10 ° C to 22 ° C by an electric heater, and some air escapes through the cracks as the heated air in the house expands at constant pressure. The amount of heat transfer to the air and its cost are to be determined. Assumptions 1 Air as an ideal gas with a constant specific heats at room temperature. 2 The volume occupied by the furniture and other belongings is negligible. 3 The pressure in the house remains constant at all times. 4 Heat loss from the house to the outdoors is negligible during heating. 5 The air leaks out at 22 ° C. 22 ° C 10 ° C AIR Properties The specific heat of air at room temperature is C = 1.007 kJ/kg. ° C (Table A-15). p Analysis The volume and mass of the air in the house are V == (( floor space)(height) m )(3 m) m 23 200 600 = m PV RT = (. . 1013 0 287 747 9 kPa)(600 m ) kPa.m / kg.K)(10 + 273.15 K) kg 3 3 Noting that the pressure in the house remains constant during heating, the amount of heat that must be
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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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