Analyses
Make a "First Law" analysis
of the heat transfers at the two heat exchangers and the work done on the
system to verify that energy is conserved in the system. Use your data and
the definitions of the COP for the refrigerator and the heat pump to verify that
the experimentally determined COPs are related such that:
COPHeat
Pump = (COPRefrigerator + 1)
Determine
the COPs from the Pressure/Enthalpy and
Temperature/Entropy
diagrams for the working fluid. Compare these values with
those obtained from the pragmatic definition of the COP using the electrical
work done and the heat transfers at the condenser and evaporator. Discuss
why these values differ. Which values are most useful in deciding if a heat
pump is a good alternative to electrical resistance heating or an oil or gas
furnace?
Determine the temperature dependence of the COP of each device
and use this to discuss the utility of each as the temperature difference
for "pumping heat" increases. |