thermodynamics

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A body at

1100°C

in black surroundings at

550°C

has an emissivity of 0.4 at

1100°C

and 0.7 at

550°C

. Calculate the rate of heat loss by radiation per square metre.

a) when the body is assumed gray

b) w

hen the body is not gray

c) What is the error in assuming a gray body? Assuming that the absorptivity is independent of the

surface temperature.