Question

What is the difference between a refrigerator and a heat pump? What is the difference between a refrigerator and an air conditioner? Define the coefficient of performance of a refrigerator in words. Can it be greater than unity? Check the specification of refrigerator or air-conditioner at your home. See if you can obtain COP of the machine. A heat pump that is used to heat a house has a COP of 2.5. That is, the heat pump delivers 2.5 kWh of energy to the house for each 1 kWh of electricity it consumes. Is this a violation of the first law of thermodynamics? Explain.

Answer 1

Difference between Refrigerator and Heat pumps

1) Transfer of heat: Both the refrigerator and the heat pumps carry the heat from low temperature reservoir or the sink to the high temperature reservoir or source. The main purpose of the refrigerator is to chill or cool or freeze the substance, by maintaining very low temperature in the freezer. It absorbs the heat from the freezer or evaporator and throws it to the atmosphere which is at high temperature.

The main purpose of the heat pump is to heat the room during winter seasons or when the atmospheric temperature is very low. It absorbs the heat from the atmosphere which is at low temperature and throws it to the room which is at high temperature and which is to be heated.

2) Location of the evaporator: In the refrigerator the evaporator is located in the freezer section. The evaporator absorbs the heat from the substance, which is to be cooled. In the heat pump the evaporator is located outside the room which is to be heated. The evaporator absorbs the heat, which is later thrown inside the room for heating it.

3) Location of the condenser: In the refrigerator the condenser is located outside the refrigerator and it is exposed to the atmosphere. It is through the condenser that the heat is thrown to the atmosphere. In the heat pump the condenser is located inside the room and it acts as the heating devise.

4) Working of evaporator and condenser: In the refrigerator the evaporator performs the main function of chilling or freezing, while the condenser performs the function of delivering the heat to the atmosphere. In the heat pump, it is the condenser that performs the main function of heating the room, while the evaporator performs the function of absorbing the heat from the atmosphere....

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COP of 2.5 doesn't violate first law of thermodynamics