(1) Basic information

Screw compressors are also called screw compressors. In the 1950s, oil-injected screw compressors were used in refrigeration devices. Due to their simple structure and few wearing parts, they can have low exhaust temperatures under large pressure differences or pressure ratios. Refrigerant contains a large amount of lubricating oil (often called wet stroke) and is insensitive and has good air transmission adjustability. It quickly occupied the range of use of large-capacity reciprocating compressors, and continuously extended to medium capacity range, widely used in refrigeration, refrigeration, Air conditioning and chemical technology and other refrigeration equipment. The screw heat pump based on it has been used in heating and air conditioning since the early 1970s. It includes air heat source type, water heat pump type, heat recovery type, ice cold storage type, etc. In industry, in order to save energy, screw heat pumps are also used for heat recovery.

(2) Product introduction

Common products for screw compressors include screw air compressors commonly known as screw air compressors, screw refrigeration compressors and screw process compressors. Screw compressors are used more and more widely. Various open and semi-enclosed screw compressors have formed a series, and later a fully enclosed series of screw compressors appeared. Twin screw compressors are referred to as screw compressors, which consist of two rotors, while single screw compressors consist of one rotor and two star wheels. Their input power range for refrigeration and heating has been developed to 10-1000KW. Based on a series of advantages of screw and single screw compressors, their research and development fields are very extensive, and their performance optimization potential is great.

The advantages of screw compressors are as follows:

1) High reliability. The screw compressor has few parts and no wearing parts, so it operates reliably and has a long life. The overhaul interval can reach 40,000 - 80,000 hours.

2)Convenient operation and maintenance.

3) Good power balance. It is especially suitable for use as a mobile compressor, with small size, light weight and small footprint.

4) Strong adaptability. Screw compressors have the characteristics of forced gas transmission. The volumetric flow rate is almost unaffected by the exhaust pressure. They can maintain high efficiency over a wide range. They are suitable for a variety of working fluids without any changes in the compressor structure.

5) Multi-phase mixed transmission. There is actually a gap left between the rotor tooth surfaces of the screw compressor, so it can withstand liquid impact and can transport liquid-containing gases, dust-containing gases, easily polymerized gases, etc.

(3) Product application areas

Air conditioning and refrigeration cycle systems in various industries.

(4) Application cases

Electricity saving renovation project of lithium bromide unit of Shanghai General Pharmaceutical Co., Ltd. Before the transformation of Shanghai General Pharmaceutical Co., Ltd., the original lithium bromide refrigeration system was aging, and the refrigeration efficiency was low, which could not meet the production requirements.

b) Implementation content and cycle: Shanghai General Pharmaceutical Co., Ltd. transformed two lithium bromide units and replaced the original two lithium bromide units with two water-cooled screw compressor chillers. The original lithium bromide refrigeration system used steam, but now the screw chiller uses electricity. The project started in January 2018 and was completed in December 2018.

c) Energy conservation and emission reduction effects and investment payback period: The total fare for energy-saving renovation of the central air-conditioning system of two water-cooled screw compressors and chillers within the boundary of this project is 1.335 million yuan, mainly for equipment purchase costs. This project replaces steam with electricity. The price of electricity is 0.75 yuan/kWh, and the price of steam is 298 yuan/ton (refer to the 2019 heat supply and use contract). The annual cost savings calculated based on the output before transformation are 1.4244 million yuan. Therefore, the static investment payback period is approximately 133.5 / 142.44×12 = 11.25 (months), that is, the investment payback period is approximately 11 months.