Description

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Heat pump systems can operate using different thermodynamic cycles.

List of thermodynamics cycles

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Here are the main thermodynamics cycles used by heat pump systems:

Most commun heat pump cycles

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• sub-critical cycle
• trans-critical cycle
• Reversed-brayton cycle also called Bell Coleman cycle or reversed Joule cycle
• Stirling Engine

The sub-critical cycle is a heat pump cycle which refrigerant changes phase during their exchange of heat with the source and the sink. It is only possible if the temperature of the heat sink is below the critical temperature of the refrigerant. The following graph shows an example of such cycle using a typical pressure enthalpy diagram.

The transcritical cycle is a heat pump cycle which refrigerant changes phase during their exchange of heat with the source but stay in the gaseous phase in the heat sink. It happens when the temperature delivered is higher than the critical temperature of the refrigerant. That implies a temperature glide in the sink heat exchanger. The following graph shows an example of such cycle using a typical pressure enthalpy diagram.

References

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