A heat pump is used to keep a house warm at 22∘C.
How much work is required of the pump to deliver 3000 J of heat into the house if the outdoor temperature is 0∘C. Assume a COP of 3.0
How much work is required of the pump to deliver 3000 J of heat into the house if the outdoor temperature is -15∘C? Assume a COP of 3.0
How much work is required of the pump to deliver 3000 J of heat into the house if the outdoor temperature is 0∘C. Assume an ideal (Carnot) coefficient of performance COP = TH/(TH−TL).
How much work is required of the pump to deliver 3000 J of heat into the house if the outdoor temperature is -15∘C. Assume an ideal (Carnot) coefficient of performance COP = TH/(TH−TL)
a )
given
Q = 3000 J , COP = 3
then W = Q / COP
W = 3000 / 3 = 1000 J
b )
given
Q = 3000 J , COP = 3
then W = Q / COP
W = 3000 / 3 = 1000 J
c )
given
Q = 3000 J ,
COP = TH / ( TH - TL )
= Q / W
TH = 273 + 22 = 295 K ,
TL = 273 + 0 = 273 K
TH - TL = 22 K
so COP = TH / ( TH - TL )
COP = 295 / 22 = 13.4
so W = Q / COP
W = 3000 / 13.4
W = 223.88 J
d )
given
Q = 3000 J ,
COP = TH / ( TH - TL )
= Q / W
TH = 273 + 22 = 295 K ,
TL = 273 - 15 = 258 K
TH - TL = 37 K
so COP = TH / ( TH - TL )
COP = 295 / 37 = 8
so W = Q / COP
W = 3000 / 8
W = 375 J
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