Thermodynamics HW Solutions 25

Thermodynamics HW Solutions 25 - constant at the specified...

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Chapter 1 Basics of Heat Transfer Assumptions 1 Steady operating conditions exist since the surface temperatures of the wall remain constant at the specified values. 2 Thermal properties of the wall are constant. Properties The thermal conductivity of the wall is given to be k = 0.69 W/m ⋅° C. Analysis Under steady conditions, the rate of heat transfer through the wall is 30 cm 20 ° C 5 ° C Brick wall 0.3 m W 1035 = ° × ° = Δ = m 0.3 C 5) (20 ) m 6 C)(5 W/m (0.69 2 L T kA Q cond 1-63 The inner and outer surfaces of a window glass are maintained at specified temperatures. The amount of heat transfer through the glass in 5 h is to be determined. Assumptions 1 Steady operating conditions exist since the surface temperatures of the glass remain
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Unformatted text preview: constant at the specified values. 2 Thermal properties of the glass are constant. Properties The thermal conductivity of the glass is given to be k = 0.78 W/m ⋅° C. Analysis Under steady conditions, the rate of heat transfer through the glass by conduction is W 4368 m 0.005 C 3) (10 ) m 2 C)(2 W/m (0.78 2 = ° − × ° ⋅ = Δ = L T kA Q cond & Glass 3 ° C 10 ° C 0.5 cm Then the amount of heat transfer over a period of 5 h becomes kJ 78,620 = × = Δ = s) 3600 kJ/s)(5 (4.368 t Q Q cond & If the thickness of the glass doubled to 1 cm, then the amount of heat transfer will go down by half to 39,310 kJ . 1-25...
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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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