The difference between parallel compressor unit and single compressor unit
Merge the single compressor into a multi-compressor parallel system, that is, several compressors are connected in parallel on a common frame, and share suction/discharge pipes, air-cooled condensers, liquid receivers and other components, and provide refrigerant to all air coolers, so that the energy efficiency ratio of the system reaches the working state, so that the unit works stably, has low failure rate, and is economical and energy-saving.
Parallel units for cold storage can be widely used in different industries such as food processing, quick-freezing, medicine, chemical industry, and military scientific research. Generally, compressors can use various refrigerants such as R22, R404A, R507A, and 134a. Depending on the application, the evaporation temperature can vary from +10°C to -50°C.
Under the control of PLC or special controller, the parallel units match the changing cooling demand by adjusting the number of compressors started.
What are the advantages of a parallel compressor unit over a single compressor unit?
1) One of the most obvious advantages of parallel units is high reliability. When a compressor in the parallel compressor unit fails, other compressors can still continue to work normally. Even if a small problem causes a single compressor unit to fail, the cold storage will be in a state of paralysis and pose a threat to the quality of the goods stored in the warehouse. There is no other way but 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 selects the compressor according to the harsh working conditions, but in fact the refrigeration system operates under the half-load condition most of the time. Under this condition, the COP value of the parallel unit can be exactly the same as that at full load. At this time, the COP value of the single unit will be reduced by more than half. Comprehensive comparison, the parallel unit can save 30~50% of electricity than the single unit.
3) High efficiency and energy saving, capacity control can be carried out in stages, through the combination of multiple compressors, it can provide multi-level energy adjustment stages, and the cooling capacity output of the unit can match the actual load demand. Multiple compressors can be of different sizes to more smoothly and dynamically match the actual load, thus realizing energy regulation for load changes, improving efficiency and saving energy.
4) Parallel units have more comprehensive protection, and usually leave the factory with a complete set of safety protection including phase loss, reverse phase sequence, overvoltage, undervoltage, oil pressure, high voltage, low voltage, electronic low liquid level, and electronic motor overload module.
5) Provide multi-suction branch control. According to the needs, one unit can provide multiple evaporation temperatures, effectively use the cooling capacity of each evaporation temperature, and make the system operate in the most energy-saving working condition.
Compared with a single compressor unit, what should be paid attention to in parallel compressor units?
The parallel compressor unit is composed of multiple refrigeration compressors, and the refrigeration pipeline is more complicated than that of ordinary refrigeration units, so it is much more careful to balance the pipeline connection. When the pipeline of the unit is connected to a group of multiple compressors, in order to distribute the oil return to each compressor in a balanced manner, the main pipeline interface must be set in the middle of multiple machine heads, and then some branch pipes are arranged on both sides, so that the return oil flows into multiple compressor branch pipes in a balanced manner.
Moreover, valves should be added to each branch pipe to adjust the oil return volume. If this is not the case, but multiple downward branch pipes are sequentially drawn from different parts of the main pipeline to connect to multiple compressors of the parallel unit, there will be unbalanced oil return, the first oil return is always full, and the latter One in turn gradually reduces oil return. In this way, the first compressor may fail to operate, the vibration is huge, the oil pressure is too high, and the unit is overheated, so that accidents such as compressor blowing/locking occur, and the equipment is damaged. This is the problem caused by the unbalanced connection of the refrigeration pipelines of the parallel units.