CO2 transcritical cascading heat pump system and interstage compressor capacity matching method thereof

Abstract

The invention discloses a CO2 transcritical cascading heat pump system and an interstage compressor capacity matching method thereof. The matching scheme of gas displacement of a compressor in two-stage system design is optimized according to different work environments of CO2/ a CO2 cascading heat pump system, so that the cascading heat pump system runs under the condition of the highest energy efficiency ratio. The cascading heat pump system is a CO2 transcritical system at the high-temperature grade and is a CO2 subcritical system at the low-temperature grade, and the temperature of an outlet of a high-temperature-grade gas cooler, the heat exchange temperature difference in an intermediate heat exchanger and low-temperature-grade evaporating temperature serve as working condition temperature variables. High-temperature-grade evaporating temperature and high-temperature-grade exhaust pressure in the intermediate heat exchanger are controlled, and the optimal interstage compressor capacity matching method of the cascading heat pump system under different working condition temperature variables is provided.

Description

【Technical field】 [0001] The invention belongs to the technical field of mechanical engineering and relates to a CO 2 Transcritical cascade heat pump system compressor and its interstage capacity ratio method. 【Background technique】 [0002] With people's exploration of science and technology and social progress, heat pump systems in medical, chemical, residential and other fields need to operate at lower ambient temperatures. At present, the most widely used is the compressed steam heat pump cycle. The pressure ratio achieved by single-stage compression cannot be too large, and the physical properties of the refrigerant itself are limited. When the evaporation temperature is very low, it cannot be realized with only one refrigerant. The cascade system is used to divide the total temperature difference into multiple sections, and each section uses a suitable refrigerant to make the evaporation and condensation temperature difference larger. [0003] In recent years, natura...

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Problems solved by technology

The present invention is a CO 2 The capacity ratio method of inter-stage compressors in transcritical cascade heat pump systems solves the problem of temperature changes in working conditions during the design process of cascade heat pump systems, that is, the outlet temperature of the high-temperature stage gas cooler, the heat transfer temperature difference in the intermediate heat exchanger, and the evaporation of the low-temperature stage When the temperature changes, the capacity ratio of the high-temperature stage and low-temperature stage compressors in the system and the optimization of compressor selection

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