Daikin VRV – Concept of Basic Refrigeration Cycle

The refrigeration cycle is composed of repetition of the following process. “Compression ? Condensation ? Expansion ? Evaporation” The refrigerating machine conducts above cycle with compressor, condenser, expansion valve and evaporator.

Theoretic refrigeration cycle neglecting pressure loss, etc. drawn on P-H diagram is shown as above.
The difference between “temperature” and “pressure equivalent saturation temperature” is called superheated degree.
? The difference between discharging pipe temperature and condensation temperature is called discharging superheated degree(DSH).
? The difference between suction pipe temperature and evaporating temperature is called suction superheated degree (SH).

(Generally, superheated degree means suction superheated degree) The difference between “temperature” and “pressure equivalent saturation temperature” in subcooled liquid is called subcooled degree (SC).

In order to prevent wet operation (*), the superheated degree is made at evaporator outlet and refrigerant flow rate into evaporator is regulated with expansion valve, so that the superheated vapor can be sucked by compressor.
* Wet operation is a state of operation, where wet vapor due to the vapor not completely vaporized in the evaporator, wet vapor is sucked by compressor.
(Wet operation may cause damage of compressor due to liquid compression, dilution of refrigeration oil, etc..)

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