Electronic expansion valves
Electronic expansion valves replace mechanical expansion devices, improving control of refrigerant flow and consequently increasing unit efficiency by up to several percent.
Moreover, these also have statistical advantages again of several percent as the electronic system guarantees optimum calibration at all times, unlike mechanical devices that needs to be adjusted manually and periodically.
Lastly, yet no less significantly in quantitative terms, is the contribution that this technology makes to optimising refrigeration and air conditioning units, guaranteeing average annual savings that may exceed 30%!
Mechanical expansion devices in fact restrict the unit to operate in the same pressure conditions - around rated summer values - at all times, as these devices cannot adapt to different conditions without the risk of damaging the compressor.
In fact they require significant pressure differential to allow proper operation. Therefore condensing pressure is often maintained at artificially high levels, even at low outside temperatures.
Electronic expansion valves do not have this problem as they’re motor-driven and microprocessor-controlled and can consequently adapt refrigerant flow according to any conditions, including low pressure differential operation. They also have a range of movement that’s 10-15 times greater and a modulation capacity that’s 4-5 times higher than any mechanical device.
These aspects let designers and installers have the units operate in the best possible conditions according to the season, reducing pressure in the condenser when the outside temperature allows, and increasing the evaporator pressure as well, and thus obtaining considerable savings in running costs. Indeed, as already stressed, compressor efficiency increases as the compression ratio decreases.
|Electronic expansion valves - ExV