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Electric Drive Chillers

Chiller efficiency is usually defined in terms of its efficiency). COP-coefficient of Heat output divided by input Heat dissipation. If the nominal rating hmm 1 ton of refrigeration capacity equivalent to 12,000 Btu/hr output and input energy is equivalent to 1 kW, or 3,413 BTU/h, in result of which the COP is 12000/3,413, or 3.52.

Air-cooled piston compressor water chillers have a peak load power consumption of 1.0-1.3 kW/ton, depending on the power and ambient temperature. Thus, the peak load of the COP for these units will range from 3.52 $ 2.70. Typical rotary compressor water chillers with water cooled condenser have a peak load power consumption of 0.5-0.7kW/t, and therefore the COP 7.0-5.0.

Energy consumption by rotary compressor chiller decreases as planting cooling load is reduced, as shown in Fig. 1.7. These refrigerators operate efficiently on approximately between 30 and 90% of the load and the most effectively between 40 and 80% load. In these conditions the gas flow is reduced, however, the full heat transfer surface of the radiator and condenser are still available, as a consequence, improves heat transfer efficiency.

Below about 30% of the load refrigerant gas flow rate is reduced to the point where (1) heat pickup from the engine, and (2) mechanical inefficiency stabilized input energy needs.

The vast majority of electric drive of rotary compressor water chillers using one compressor. However, when subsequently cooling load profile indicates, there will be significant hmm use at or below 30% of the peak load, it may be beneficial to use dual chiller compressor or more single compressor chillers.

Double chiller compressor typically uses two compressors, each the size of 50% of the peak load. 50-100% of the rated load, as compressors work. However, if the load drops below 50% of project costs, one compressor is stopped and the rest of the compressor is used to meet the load. This setting has the advantage of reducing inefficient operating point of 15% of the full load (50% 30%), a significant reduction in operational penalties that will result from one compressor operation.

Negative-pressure chillers tend to be slightly more effective than positive-pressure chillers. Peak load 0,5 kW/ton or less available for negative-pressure chillers, while positive pressure hmm ratings below 0.55 kW/tonne is difficult to obtain.

Positive-pressure chillers, as a rule, smaller and lighter than the negative-pressure chillers, which can lead to a reduction hmm service and light construction. Negative-pressure chillers generally have a higher cost than positive pressure machines.

When buying a chiller, owners have to decide whether the increased efficiency of negative pressure coolers worth the additional first cost, environmental impact, releasing refrigerants, the higher the toxicity of R-123 and the impact of the replacement of HCFC...

 
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