What is a Heat Pump?
Below diagram shows working of a heat pump
Th: Temperature of source
Tc: Temperature of sink
Qh: Heat rejected by the heat pump
Qc: Heat extracted by the heat pump
W: Work input to the heat pump
Given: Th > Tc
Coefficient of performance (COP)
Coefficient of performance (COP) is the ratio of desired effect (either heating or cooling) to the work input.
Since a heat pump is used for both cooling and cooling purpose hence it has two COPs.
COPHeating = (Qc+ W)/ W
COPCooling = Qc/ W
Clausius statement of second law
It is impossible to construct a device which, operating in a cycle, will produce no effect other than the transfer of heat from a cooler to a hotter body.
If we analyze heat engine and heat pump together then we will find two very important results regarding the inter-conversion of heat and work.
- Even in the ideal case all the heat can never be converted fully into the work
- Work can be fully converted to heat