Mechanical Refrigeration

The refrigeration effect is achieved by one of the following cycles:
• Vapor – compression – expansion.
• Absorption.
• Steam jet (water vapor compression).
These cycles can be further broken down into four distinct steps by means of the Pressure-Enthalpy (P-H) diagram as shown in Figure 17-4:
• Expansion.
• Evaporation.
• Compression.
• Condensation.

Expansion Step

This operation involves the proper functioning of an expansion valve or throttle valve. After condensation, the liquid refrigerant is stored in the liquid phase until needed. From liquid storage, liquid refrigerant enters the expansion valve where the pressure is required to be such to allow the liquid to vaporize at a temperature of about 10°C (263 K). The expansion ...

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