Airedale DeltaChill FreeCool 110kW - 1080kW - Manual (Page 21)

Chillers DELTACHILL
™
Chillers
21
Technical Manual :7022932_V1.9_11/2013
Design Features & Information
Energy saving features
Electronic Expansion
Valves (EEV) Using an EEV allows for good refrigeration control whilst operating at part load
and lower ambient conditions with a reduced condensing pressure. By fitting an
EEV and adjusting the head pressure control setting an increase in the system
EER (Energy Efficiency Ratio) can typically be seen at lower ambient conditions.
The Mollier diagram shown below helps to illustrate how this increase in
efficiency is achieved.
Electronic expansion valves differ to normal thermostatic expansion valves in
their ability to maintain control of refrigerant flow and the suction superheat at
reduced head pressures. The turn-down rate of a typical EEV is superior to that
of its thermostatic equivalent, such that a reduced optimum condensing
pressure can be maintained at low compressor load. However low the load is on
the compressor, from zero to 100%, there will not be a problem with turn down,
even down to 30% of the valves rated capacity.
1
2
3
4
A
B
X
Y
Bubble Dew
1
2
3
4
Thermostatic
Expansion Valve
Electronic Expansion
Valve
1
Compression
2 Condensation
3 Expansion
4 Evaporation
Reduced Condensing
Pressure
Pres
s
ure
(ba
ra)
Evaporating Pressure
1
2
3
4
Enthalpy
(kJ/kg)
1
2
3
4
Increase in
Cooling Duty
Reduction in
Input Power
Key: Cooling cycle @ 22°C ambient with a conventional TEV fitted.
Cooling cycle @ 22°C ambient, demonstrating a typical EEV condensing temperature taking full
advantage of lower ambient air temperatures (below 30°C).