Thermodynamics HW Solutions 979

Thermodynamics HW Solutions 979 - Chapter 12 Radiation Heat...

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Chapter 12 Radiation Heat Transfer 12-96 A simple solar collector is built by placing a clear plastic tube around a garden hose. The rate of heat loss from the water in the hose by natural convection and radiation is to be determined. Assumptions 1 Steady operating conditions exist 2 The surfaces are opaque, diffuse, and gray. 3 Air is an ideal gas with constant specific heats. Properties The emissivities of surfaces are given to be ε 1 = ε 2 = 0.9. The properties of air are at 1 atm and the film temperature of ( T s + T )/2 = (40+25)/2 = 32.5 ° C are (Table A-15) 1 - 2 5 K 003273 . 0 K ) 273 5 . 32 ( 1 7275 . 0 Pr /s m 10 632 . 1 C W/m. 02607 . 0 = + = = × = ° = β υ k D 2 =6 cm Garden hose D 1 =2 cm, T 1 ε 1 = 0.9 Air space Plastic cover, ε 2 = 0.9, T 2 =40 ° C Water T = 25 ° C T sky = 15 ° C Analysis Under steady conditions, the heat transfer rate from the water in the hose equals to the rate of heat loss from the clear plastic tube to the surroundings by natural convection and radiation. The characteristic length in this
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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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