Refrigeration CH. 1-2

What can a 3rd class license operate?

Entitles the holder to operate a refrigeration plant of any capacity

What can a 4th class license operate?

Entitles the holder to operate a refrigeration plant with a capacity no more than 500 tonnes

What is refrigeration?

HOT TO COLD. Lowering the temperature of a substance below the temperature of its surroundings and maintaining the substance at the lower temperature using the circulating refrigerant.

What must a substance do in order to change state?

It must absorb latent heat. When latent heat is added to a liquid, it evaporates. When latent heat is removed from a gas it condenses.

What affects the temperature at which the liquid boils?

The pressure exerted on the surface of a boiling liquid

For every________ , the is one corresponding __________

Saturation pressure, saturation temperature

What are the 5 mandatory components in refrigeration?

Refrigerant, evaporator, expansion valve, condenser and compressor

What’s a closed cycle system?

Vapor from the evaporator is collected continuously and is used over and over again in the system.

What does the evaporator do?

Brings heat in from inside fridge and evaporates refrigerant. It is a heat exchanger where everything happens.

What does a condenser do?

Vapor goes through condenser and heat goes away and gets rid of the heat and turns it back into a liquid. It has to get rid of the additional heat/work the evaporator and compressor have done. Another kind of heat exchanger where everything happens.

What is a compressor?

Compresses the vapour from evaporator and increases the temperature to go to the condenser

What is an expansion valve?

Lowers the pressure/temperature from the condenser to go back to the evaporator.

What is low pressure?

Goes from metering device to the evaporator and up to the compressor before increasing in pressure again.

What is high pressure?

Comes out of compressor, then goes into condenser before going back through the expansion valve to low the pressure again.

How do the compressor and expansion valve work together?

Everything the compressor increases in pressure, the expansion valve has to decrease in pressure the same amount

Where is pressure on low side determined by?

Evaporation temperature required for desired refrigeration effect

Where is pressure on high side determined by?

Required condensing temperature which depends on type/temperature of condensing medium