Variable-volume two-stage compression system and control method thereof

Abstract

The invention provides a variable-volume two-stage compression system which comprises a compressor (1). The compressor (1) comprises a low pressure cylinder and a high pressure cylinder which are connected in series. The low pressure cylinder comprises at least two air cylinders connected in parallel. The compression system further comprises a control mechanism which can control at least one of the air cylinders connected in parallel to perform full-load operation and / or non-load operation. Variable high and low pressure level displacement ratios can be achieved on the compressor, the energy efficiency changes are small compared with a system with two compressors connected in series, the requirement for refrigeration and heating energy efficiency can be met at the same time, and the system economy is greatly improved; the structure is simpler, the cost is lower, and the problem that balancing oil of the two compressors is not balanced is solved; and in addition, the operation temperature range of the system can be enlarged, the operation efficiency of the system can be improved, the reliability of the two-stage compression system is improved, and therefore the economy of the two-stage compression system is greatly improved. The invention further relates to a variable-volume two-stage compression control method.

Description

technical field [0001] The invention belongs to the technical field of air conditioning, and in particular relates to a variable capacity two-stage compression system and a control method thereof. Background technique [0002] The lower the ambient temperature, the greater the demand for the heating capacity of the air conditioner. However, the current single-stage compression heat pump can only start and run normally above minus 20 degrees (outdoor ambient temperature), and the heating capacity is severely attenuated, and the heating effect cannot be guaranteed. Unit reliability has also been severely tested. [0003] Compared with single-stage compression heat pumps, the two-stage compression system with air injection enthalpy increases the heating capacity at low temperatures and has higher energy efficiency. And the two-stage compression system can reduce the pressure ratio of the single-stage compressor, lower the exhaust temperature, and at the same time improve the s...

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Problems solved by technology

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the defects that the two-stage compression system in the prior art has a large change in energy efficiency, a fixed compression ratio cannot meet the energy efficiency requirements of refrigeration and heating at the same time, and the economy is not ideal. Provide a variable capacity two-stage compression system and its control method

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