Coefficient of Performance of the Heat Pumps

Written by: Haresh Khemani • Edited by: Lamar Stonecypher
Published Nov 24, 2008

The coefficient of performance, also called as the COP, of the heat pump is defined as the ratio of the desired effect from the heat pump to the power consumed by the heat pump.

The coefficient of performance, also called as the COP, of the heat pump is defined as the ratio of the desired effect from the heat pump to the power consumed by the heat pump. The desired effect from the heat pump is producing the heat inside the room and the power consumed by the heat pump is the power consumed by the compressor, hence COP is also defined as the ratio of heat produced inside the room to the power consumed by the compressor.

Let us suppose:

H1 – enthalpy of the refrigerant leaving the evaporator and entering the compressor

H2- Enthalpy of refrigerant leaving the compressor and entering the condenser

H3- Enthalpy of refrigerant leaving the condenser and entering the expansion valve

H4 – Enthalpy of the refrigerant leaving the expansion valve and entering the evaporator

During the expansion of the refrigerant in the expansion valve, its enthalpy remains constant, hence H3 = H4.

Coefficient of Performance or COP = Heat produced inside the room / Power consumed by the compressor

Heat produced inside the room is the heat absorbed from the condenser = H2 – H3, since the enthalpy of the refrigerant entering the condenser is more than the enthalpy of refrigerant leaving the condenser.

The power consumed by the compressor = H2 – H1

Hence COP of the Heat Pump = H2 – H3 / H2 – H1

Relation between COP of Heat Pump and Refrigerator

The main purpose of the refrigerator is to produce the cooling effect and it consumes power for this. The main purpose of the heat pump is to cool the room and it consumes power for it. From the above formula of the COP you will find that:

COP of Heat Pump = 1 + COP of the Refrigerator

The COP of the refrigerator and air-conditioner can be less than one or greater than one. The above formula also shows that the COP of the heat pump can never be less than one; it is always more than one.

It is worth mentioning here that efficiency of the engine can never be more than one, but the COP of the heat pump is always more than one. You should know that the terms efficiency and the COP are entirely different terms. The efficiency describes the capacity of the engine to produce power from the fuel, while the COP indicates how effectively the energy is used to produce the desired effect which is producing heat in case of the heat pump and coolness in case of the refrigerator.

ashok Feb 5, 2011 5:03 AM

cop of solar refrigerator

i am doing a solar ammonia absorption ice maker how can i measure the cop for that

Ron Jul 27, 2010 5:28 PM

Small is Big

Why do small heat pumps (usually) have bigger COPs?

harpreet Apr 30, 2010 11:04 AM

refrigerator

why cop of refrigerator greater than 1? can c.o.p of refrigerator be less than 1 in any case?

nagarajan Mar 13, 2010 2:09 AM

is it possible that a refrigerator to have COP lesser than one. eg. 0.78 or 0.35

Haresh Khemani Dec 18, 2009 9:49 AM

COP

COP means coefficient of performance. Its says how effectively the refrigerator or air conditioner is working. The function of the refrigerator and AC is to move the heat from the low temperature reservoir to the high temperature reservoir (against the law of thermodynamics that says that heat flows from high temp. to low temp.). The COP says how effectively the refrigerator or AC performs this function. It says the amount of power required by the machine to move certain quantity of heat from low temp. to high temp.

The efficiency is related with automobile engines, boilers etc that produce power from the fuel. They convert energy from one form to the other, while refrigerator moves the energy from low temp. to high temp. So the efficiency says how effectively the machine is converting the energy from fuel to the power.

The COP can be more that one since the heat transferred can be more than power required by the refrigerator but the efficiency can never be more than one since the power generated by engine cannot be more than the total heat content of the fuel.

ALI Dec 18, 2009 8:15 AM

Cop

what is the difference between cop and efficiency ???

Rai Sep 7, 2009 3:07 PM

on the heat pump

Can u plz show me the mathematical model of the compressor and the expansion valve. I would like to knoe they thermodynamics, mass flow rate and heat exchanger rate in this two devices of a heat pump

Haresh Khemani Aug 23, 2009 9:30 AM

I don't think this is relevant questions here. There central air conditioning systems of hundreds of tonnage. Haresh

shree Aug 23, 2009 6:02 AM

wheres the Biggest central air conditioning system in india ? not its factory sir, I want the place where this system runs. just like rajmandir multiplex in jaipur in 2005.

SHREE PATIL Aug 23, 2009 5:51 AM

HEAT PUMP AND REFRIGERATOR

SIR ! Can I know why the value of heat pump is greater than 1 and why the value of refrigerator is near about 1 ?

Haresh Khemani Aug 22, 2009 2:16 AM

Heat pump

The COP of heat pump is also called as Effective Performance Ratio (EPR). When operating between the same temperatures, the relation between the COP of the refrigerator and that of the heat pump is given in the above article. For justification, you can refer any reference book on Refrigeration and Air Conditioning and go through the analysis of the vapor compression cycle.

Haresh

imran Aug 21, 2009 9:51 AM

heat pump

wheather the cop of heat pump and refrigerator should be highor low?justify?

Coefficient of Performance of the Heat Pumps

Relation between COP of Heat Pump and Refrigerator

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