Daikin EWAH620TZ-XSB2 [6/102] General characteristics

6/100

GENERAL CHARACTERISTICS

During chiller operation the working parameters (condensing and evaporating pressure) are subjected to

sensible changes, due to the variations of the ambient temperature and energy demand from the plant, leading

to a variable pressure ratio (defined as condensing pressure on evaporating pressure).

An air cooled chiller equipped with a compressor characterized by high volume ratio will have good performances

at full load with high ambient temperatures, while in case of moderate ambient temperatures and during part

load operation, the actual pressure ratio for the chiller will be lower the compressor's characteristic. In this

situation the refrigerant will result more compressed than the actual needs.

This lead to a phenomenon named “over-compression”. The “extra-work” of the compressor result in an

unnecessary waste of energy.

On the other and, a chiller equipped with a compressor characterized by low volume ratio will have good

performance during part load operation and low ambient temperature, but it will be less efficient during full load

operation and with high ambient temperature.

In this case the actual pressure ratio for the chiller will be higher the compressor's characteristic, so at the

discharge of the compressor the gas will be at a lower pressure than the condensing pressure. Part of the

refrigerant will go from the condenser back to the compressor and the compressor will spend additional work

to re-send it to the condenser. This phenomenon is known as “under-compression”

In order to obtain the best efficiency possible at every working condition Daikin compressors can adjust their

own geometry according to the real operating conditions enhancing the efficiency. This is possible thanks to a

moving slide delay the discharge of the compression according to the actual operating conditions.