Refrigeration - Vapor-Compression Cycle

Key Questions

The following key questions are answered in this module:

How does a refrigerant provide cooling in the vapor-compression refrigeration cycle?
In this cycle, a "refrigerant" alternately absorbs and rejects heat as it circulates through the piping and components of a "refrigeration unit." It absorbs heat as it passes through the space being refrigerated, and then rejects it as it travels through an outside space.

What is a "refrigeration unit"?
A refrigeration unit has four main components - an evaporator, compressor, condenser, and metering device. The refrigerant experiences two different pressures (and temperatures) as it circulates through the piping that connects the components.

When I hear my refrigerator "running," what am I hearing?
The compressor is an electrical component that increases the pressure and temperature of the refrigerant, and it is what you hear when the refrigerator is "running."

What makes a substance a good refrigerant?
Refrigerants are selected based on their boiling point-pressure characteristics, as it is critical that a refrigerant boil below the desired low temperature and condense at a sufficiently high temperature.

Are there other requirements for refrigerants?
Refrigerants must also be environmentally acceptable, chemically stable, and compatible with the materials present, and meet all applicable flammability and toxicity requirements.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

In the vapor-compression refrigeration cycle, a "refrigerant" alternately absorbs and rejects heat as it circulates through a refrigeration unit. The unit has four main components - an evaporator, compressor, condenser, and metering device - and the refrigerant experiences two different pressures as it circulates through the piping that connects the components. In the evaporator, a mixture of cool liquid and gas refrigerant flows through a set of coils while an external fluid (usually air) passes over and around the outside of the coils, which are in an enclosed space. The external fluid is warmer than the refrigerant, so it transfers some of its heat to the refrigerant. This movement of heat "refrigerates" the fluid- filled enclosed space and causes the refrigerant inside the evaporator coils to boil (or evaporate) and change into a gas (or vapor).

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