Thermodynamics HW Solutions 891

Thermodynamics HW Solutions 891 - Chapter 11 Fundamentals...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 11 Fundamentals of Thermal Radiation 11-63 The absorber surface of a solar collector is exposed to solar and sky radiation. The equilibrium temperature of the absorber surface is to be determined if the backside of the plate is insulated. Insulation Air T = 25 ° C T sky = 15 ° C Absorber plate T s = ? α s = 0.87 ε = 0.09 600 W/m 2 Properties The solar absorptivity and emissivity of the surface are given to α s = 0.87 and ε = 0.09. Analysis The backside of the absorbing plate is insulated (instead of being attached to water tubes), and thus & q net = 0 αε σ s solar s sky s air GT T h T =− + () ( 44 T ) [ ] K 346 = + × = s s s T T T K) 298 )( K W/m 10 ( K) 288 ( ) ( ) K W/m 10 67 . 5 )( 09 . 0 ( ) W/m 600 )( 87 . 0 ( 2 4 4 4 2 8 2 Special Topic: Solar Heat Gain Through Windows 11-64C ( a ) The spectral distribution of solar radiation beyond the earth’s atmosphere resembles the energy emitted by a black body at 5982 ° C, with about 39 percent in the visible region (0.4 to 0.7 μ m), and the 52 percent in the near infrared region (0.7 to 3.5 μ m). ( b ) At a solar altitude of 41.8 °
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.
Ask a homework question - tutors are online