Sunday
April 20, 2014

Homework Help: physics

Posted by Justin on Sunday, July 28, 2013 at 1:33am.

(a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of 50.0C and a cold reservoir temperature of -20.0C?

(b) How much heat in kilocalories would it pump into the warm environment if 3.60 multiplied by 107 J of work (10.0 kWh) is put into it?

(c) Assume the cost of this work input is 10¢/kWh. Also assume that the cost of direct production of heat by burning natural gas is 88.0¢ per therm (a common unit of energy for natural gas), where a therm equals 1.055 multiplied by 108 J. Compare the cost of producing the same amount of heat by each method. (cost of heat pump / cost of natural gas)

a. Tc=253.15k, Th=323.15
COP=1/(1-253.15/323.15)=4.62

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