Refrigeration Systems

Working principle

Vapor compression system transports heat efficiently

In refrigeration systems, working fluid in gas state is brought from low to high temperatures and pressures using a compressor. It is then condensed by releasing heat to a moderate temperature source (for example the ambient environment). Pressure is then reduced in an expansion device turning the working fluid into a low temperature two phase mixture which evaporates in an evaporator by absorbing heat from a low temperature source (for example a refrigerator’s internal air, an electronics board, laser diode(s), pixel detector, etc.).

Similarly, the compressor can be replaced by a pump and the expansion device eliminated to achieve a pump-driven two-phase cooling system.

Refrigeration systems mechanically-driven cooling requires electrical input.

CONDENSER

Expansion device

Animation showing the working principle of refrigeration cooling systems.

Compressor

Evaporator

Components

Refrigeration systems consist of four main components, as describe below.

Evaporator

Here heat enters the system, where it is transferred from the heat source(s) into the working fluid, resulting in total evaporation. Compact air-cooled heat exchanger are typically used, depending on the target cooling capacity.

A schematic representation of an air-cooled condenser

A schematic representation of an evaporator with microchannels

Expansion Device

Here pressure (and temperature) is brought down from high to low. Capillary tubes are typically used. They can be coupled to an internal heat exchanger to optimize system design and ensure gas return to the compressor. Expansion valves can be used to control evaporator superheating by adjusting system mass flow rate.

Compressor

Here pressure (and temperature) is brought from low to high. Depending on the application, reciprocating, rotary or turbo-centrifugal compressors can be used.

Condenser

Here heat exits the system. It is removed by the coolant, resulting in total condensation of the working fluid. The condenser can be cooled by natural or forced convection with air, gas or liquid.

A schematic representation of a liquid-cooled condenser

Refrigeration systems

Working principle

Components

Applications

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