Improving the Vapor-Compression Refrigeration Cycle

Process flow diagram for a vapor-compression refrigeration cycle with the condenser and evaporator highlighted.
In the previous lesson, we discussed the importance of selecting the appropriate refrigerant. We stressed the importance of the P*-T relationship. This relationship determines the operating pressures of the condenser and the evaporator.
Recall from Lesson 10B:
The

vapor pressure

of the

refrigerant

at the temperature of the condenser should not be too high, P*(Tcond) < 2 MPa, to keep equipment costs low.
The

vapor pressure

of the

refrigerant

at the temperature of the evaporator should be greater than 1 atm, P*(Tevap) > 1atm, to prevent air leakage into the system.
The combination of these two constraints puts a firm limit on the range of temperatures between which a simple

vapor-compression refrigerator

can operate.
How can we make the cold space even colder (reduce TC) and reject heat at an even higher temperature (increase TH) without dramatically increasing the cost to build the refrigeration system ?
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Ch 10, Lesson C, Page 1 - Improving the Vapor-Compression Refrigeration Cycle