Application and professional knowledge of semi closed compressors in cold storage1

1、 Basic definition and core principles of semi enclosed compressor

The semi enclosed compressor is the core power equipment of the refrigeration system in cold storage, which is between the fully enclosed compressor and the open compressor. It is the mainstream model for small and medium-sized commercial cold storage and industrial cold chain. Its core feature is the integrated packaging of the motor and compressor body, and the detachable maintenance of the shell, without the need for overall disassembly and scrapping. Only the replacement of valve plates, pistons, bearings and other accessories can be repaired, greatly reducing the long-term operation and maintenance costs of the cold storage.

The working principle follows the steam compression refrigeration cycle: the cylinder is driven by the crankshaft connecting rod or rotor structure to compress the low-temperature and low-pressure refrigerant vapor into high-temperature and high-pressure gas, providing power for the refrigerant to dissipate heat in the condenser and absorb heat in the evaporator, continuously taking away the heat inside the cold storage, achieving constant temperature refrigeration, preservation, and freezing effects inside the cold storage, and adapting to the long-term continuous operation requirements of the cold storage.

2、 Classification of mainstream models and characteristics of cold storage adaptation

The commonly used semi enclosed compressors in cold storage are mainly divided into two types: piston type and screw type, which are suitable for different storage capacities, temperatures, and working conditions, and are also the core basis for engineering selection:

（1） Semi closed piston compressor

This is the most mature and widely used model in cold storage applications, with mainstream brands including Bitzer, Gulun, Duling, etc. The power covers 2HP-50HP and the cooling capacity is 10-300kW.

1. Core advantages: simple structure, mature manufacturing process, fast start stop response, high temperature control accuracy, adaptable to frequent start stop working conditions; The single machine manufacturing cost is low, and the energy efficiency is stable during low load operation.

2. Adaptation scenarios: Small and medium-sized fruit and vegetable fresh-keeping warehouses, fresh refrigeration warehouses, pharmaceutical shade warehouses, and commercial supermarket small freezing warehouses, suitable for conventional cold storage conditions from 0 ℃ to -25 ℃, are the preferred models for small and medium-sized cold storage.

3. Structural features: 2-8 cylinders can be selected, driven by a four pole motor, running smoothly, modular assembly of air-cooled and water-cooled condensing units, saving installation space in cold storage.

（2） Semi closed screw compressor

Belonging to medium to large high-efficiency models, it adopts an asymmetric screw rotor design, which is wear-resistant and runs smoothly. The power coverage is over 50HP, and the cooling capacity is 30-600kW.