heat is transferred from a stream of water to the refrigeran

heat is transferred from a stream of water to the refrigerant in the evaporator, and from the refrigerant to another stream of water in the condenser. In a household refrigerator, from what substance or space does the refrigerant absorb heat in the evaporator? To what substance or space does the refrigerant reject heat in the condenser? What are the corresponding substances or spaces for an air-conditioner?

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Solution

In case of a house hold refrigerator, cooling is done by means of heat removal. Heat, being a form of energy cannot be destroyed and hence has to be transferred from one place to another. In this case, it should be transferred from the system( refrigerator) to the surroundings.

A refrigerator has 4 components namely Compressor, Condenser, Evaporator and a metering device. Refrigerants like HFC-134a is made to flow through these components for the heat removal process.

Air is drawn across the evaporator inside the refrigerator, as the refrigerant flows, heat is transferred along with it because it has the property of heat absorption. As a result of this, heat from the substances placed in refrigerator is transferred to the evaporator causing a decrease in temperature . This heated refrigerant flows to the condenser where the heat is rejected to the atmosphere. Hence the condenser is called air cooled condenser. The purpose of compressor is to provide sufficient pressure for the flow of refrigerant. This process repeats itself, first to evaporator and then to condenser, providing refrigeration.

In case of an air conditioner, Freon and Puron are used as refrigerants.The coolant is made to flow through the following 4 components: Evaporator, Compressor, Condenser, Expansion valve.

In this case, the condenser is an outdoor unit and evaporator is an indoor unit. Expansion valve reduces pressure on coolant which is in liquid phase, the evaporator converts the coolant fron liquid to gaseous form which absorbs heat from surrounding air. This heated refrigerant then flows to outer condenser unit where it is again converted into liquid state and the heat is let out into the atmosphere. Compressor provides necessary pressure for flow of refrigerant to condenser and evaporator. This process repeats itself.

Hence , The refrigerator absorbs heat in the evaporator from the surrounding air thus prviding cooling effect and rejects the heat in condenser to the atmosphere , keeping the system cool.