Specific Power Consumption-Vapour Compression Systems
Cooling system efficiency depends on the working temperature and, accordingly, all quality indicators related to efficiency, specified at a certain temperature operation.
Well-designed, in good condition, water cooled vapour compression systems using reciprocating, screw, or scroll compressors, for chilled water about 8with COP 4 to 5.8, EER in the range from 14 to 20 Btu/hr/W or specific Consumption of electric Power in the range from 0.61 to 0.87 kW/TR.
Open-type compressors are more efficient than semi-hermetic compressors in semi-hermetic compressors, the motor is also cooled by the refrigerant.
Centrifugal compressors, which are normally used for cooling, about 150 PR may have an efficiency of about 6, EER more than 20 specific Electricity 0,59 kW/TR.
The COP systems with air cooled condensers, as a rule, from 20% to 40% higher. In places with dry weather, the COP much better if evaporatively cooled saturated air provided instead of ambient air dry.
The COP is well designed small cars like window air conditioners and split air conditioners, as a rule, in the region of 2.5.
The COP is poor due to the needed compactness of the machine, which limits the area of heat exchange and restrictions with air-cooled condenser.
It should be noted that the constitutional court is calculated taking into account only the compressor power consumption. Power consumption of the other parasitic loads, such as pumps, fans, etc. are not considered.
Factors that affect the COP
The COP is affected by the temperature of the evaporator and condenser temperature. The higher the temperature of the evaporator and reduce the temperature of the condenser, better COP.
1 C above the temperature of the refrigerant in the evaporator or 1 C below, condenser, improves the COP from 2% to 4%.
Evaporator temperature can be increased by:
- Change the adjustment process temperature.
- Installing evaporator higher the rating, i.e. more heat transfer area.
- Keeping the heat transfer surface, i.e. the net. pollution prevention, defrosting according to the requirement and other
Condenser temperature can be reduced by:
- Installation of condenser high rating, soe.. more heat transfer area.
- Condenser temperature is allowed to float down with ambient temperature
- Water-cooled or evaporatively cooled condensers are used instead of air cooled condensers
The COP also affect:
- The effectiveness of the type of compressor used.
- The amount of refrigerant charged into the system. The system with refrigerant leaks consume more energy.
- The physical properties of the refrigerant used.
COSP (the Performance Factor of the System is another option that has been used to assess the performance of the system, including power consumption parasitic load. This is a good indicator to bench mark the overall system efficiency at a certain place, but it does facilitate comparison with other similar machines and system configuration depends on the site...
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Chillers