A heat pump collects thermal energy from outside air at 5C and delivers it into
ID: 1591961 • Letter: A
Question
A heat pump collects thermal energy from outside air at 5C and delivers it into a house at 40C. 1. Determine the maximum coefficient of performance (the maximum coefficient is determined in the same way as for a thermodynamic engine).
2. If the motor of the heating pump uses 1000 J of electrical energy to do work during a certain time interval, how much thermal energy is delivered into the house through heating, assuming the heating pump works at the maximum coefficient of performance? 3. If the motor of the heating pump uses 1000 J of electrical energy to do work during a certain time interval, how much thermal energy is delivered into the house through heating, assuming the heating pump works at a coefficient of performance of 2.0.
Explanation / Answer
1)
From the given data
Temperature of cold reservoir,
Tc = 5 + 273
= 278 k
Temperature of hot reservoir,
Th = 40 + 273
= 313 k
COP = Th/(Th - Tc)
= 313/(313 - 278)
= 8.94
2)
COP = QC/Workdone (here Qc is the heat extrcted from cold reservoir)
QC = COP*workdone
= 8.94*1000
= 8940 J
so, heat given to the room, Qh = Workdone + Qc
= 8940 + 1000
= 9940 J <<<<<<<<----------------------Answer
3) COP = QC/Workdone (here Qc is the heat extrcted from cold reservoir)
QC = COP*workdone
= 2*1000
= 2000 J
so, heat given to the room, Qh = Workdone + Qc
= 2000 + 1000
= 3000 J <<<<<<<<----------------------Answer