 #1
bardia sepehrnia
 28
 4
 Homework Statement:

A refrigeration system is used to cool down water from 15 C temperature and 150 kPa pressure to 5 C at a rate of 0.25 kg/s. Assume the refrigeration system works in a Carnot cycle between 0 C and 40C.
Determine:
a) The required rate of heat absorbed from the water
b) The maximum possible refrigeration system COP
c) The amount of power input that a refrigeration system required
d) The rate of heat rejected to the atmosphere
 Relevant Equations:

Q=m*c*deltaT
Carnot efficiency = 1(T_L/T_H)
COP=Q_L/W_net,in
I think I calculated part a correctly by extracting the cp (specific heat) of water from the table which is 4.188
Then calculated Q_dot by simply using the equation Q=m*c*deltaT=10.47kW
But I am stuck at part b, I know that the heat extracted from the water is the same as Q_L (rate of heat absorption from low temp reservoir). But how can I calculate the coefficient of performance (COP) if I don't have Q_H (rate of heat rejection to the high temp reservoir) or W_in (work input)
Then calculated Q_dot by simply using the equation Q=m*c*deltaT=10.47kW
But I am stuck at part b, I know that the heat extracted from the water is the same as Q_L (rate of heat absorption from low temp reservoir). But how can I calculate the coefficient of performance (COP) if I don't have Q_H (rate of heat rejection to the high temp reservoir) or W_in (work input)