Trane TRG-TRC003-EN "

18 TRG-TRC003-EN

notes

period three

Refrigeration Cycle

liquid refrigerant to the coil so that all the refrigerant evaporates before it

reaches the end of the coil.

One disadvantage of this system is that after the liquid refrigerant passes

through the coil and collects in the drum as a vapor, it cannot be reused. The

cost and environmental impacts of chemical refrigerants require the

refrigeration process to continue without loss of refrigerant.

Additionally, the boiling temperature of R-22 at atmospheric pressure is -41.4°F

[-40.8°C]. At this unnecessarily low temperature, the moisture contained in the

air passing through the coil freezes on the coil surface, ultimately blocking it

completely.

To solve the first problem, a system is needed to collect this used refrigerant

and return it to the liquid phase. Then the refrigerant can be passed through the

coil again.

This is exactly what happens in a typical mechanical refrigeration system.

Liquid refrigerant absorbs heat and evaporates within a device called an

evaporator. In this example system, air is cooled when it passes through the

evaporator, while the heat is transferred to the refrigerant, causing it to boil and

change into a vapor. As discussed in the previous period, a refrigerant can

absorb a large amount of heat when it changes phase. Because of the

refrigerant changing phase, the system requires far less refrigerant than if the

refrigerant was just increasing in temperature.

The refrigerant vapor must then be transformed back into a liquid in order to

return to the evaporator and repeat the process.

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Figure 29