A cold storage parallel unit refers to a refrigeration unit composed of two or more compressors that share a set of refrigeration circuits in parallel. Depending on the refrigeration temperature and cooling capacity and the combination of condensers, the parallel units can have various forms.
The same unit can be composed of compressors of the same type or different types of compressors. It can be composed of the same type of compressor (such as piston machine), or it can be composed of different types of compressor (such as piston machine + screw machine); It can load a single evaporation temperature or several different evaporation temperatures; it can be a single-stage system or a two-stage system; It can be a single-cycle system or a cascade system, etc. The common compressors are mostly single-cycle parallel systems of the same type.
For small and medium-sized cold storage, the scroll machine is too small, the screw machine is too expensive to connect in parallel, the piston formula is relatively moderate, and the cost is the highest.
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What are the advantages of parallel units?
1) One of the most obvious advantages of parallel units is high reliability. When a compressor in the unit fails, the other compressors can still continue to work normally. If a stand-alone unit fails, even a small pressure protection will protect it from shutdown. The cold storage is in a paralyzed state, posing a threat to the quality of the goods stored in the storage. There is no other way to go only to wait for repairs.
2) Another obvious advantage of parallel units is high efficiency and low operating costs. As we all know, the refrigeration system is equipped with compressors according to the worst conditions. In fact, the refrigeration system runs at half-load conditions most of the time. Under such conditions, the COP value of the parallel unit can be completely timed with the full-load condition. At the same time, the COP value of a single unit at this time will be reduced by more than half. In a comprehensive comparison, a parallel unit can save 30-50% of electricity than a single unit.
3) High efficiency and energy saving, capacity control can be carried out in stages, through the combination of multiple compressors, multi-stage energy adjustment stages can be provided, and the chiller output of the unit can match the actual load demand. Multiple compressors can be of different sizes to dynamically match the actual load more smoothly, thereby realizing the best energy adjustment for load changes, improving efficiency and saving energy.
4) Parallel units have more comprehensive protection, usually with a full set of safety protection modules including phase loss, reverse sequence, overvoltage, undervoltage, oil pressure, high voltage, low voltage, electronic low level, and electronic motor overload.
5) Provides multi-inspiration branch control. According to needs, one unit can provide multiple evaporating temperatures, effectively using the cooling capacity of each evaporating temperature, so that the system can run in the most energy-saving condition.
Post time: Dec-13-2021