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The compressor is the core of the chiller unit, and the performance it can provide directly affects the performance of the entire unit. Moreover, the performance indicators of the compressor directly determine and limit the performance of the chiller unit. The evaporator and condenser inside an industrial chiller directly affect the performance of the compressor, such as changes in evaporation temperature, condensation temperature, superheat, and subcooling. The screw chiller uses a shell and tube evaporator and condenser, which affect the performance of the evaporator and condenser. There are generally the following factors:
1. Equalizer and inner cover profile
The reasonable structure of the homogenizer can greatly distribute the refrigerant at the inlet of the evaporator evenly between the heat exchange tubes, alleviating the phenomenon of gas-liquid separation. The inner cover profile of different process transitions should be as smooth as possible to reduce resistance, avoid gas-liquid separation, and ensure even distribution of refrigerant between the heat exchange tubes in the next process.
2 Heat exchange tubes
The reasonable allocation of heat exchange tubes in different processes, as well as the structure and length of heat exchange tubes, have a significant impact on their performance. The allocation ratio of heat exchange tubes between different processes can be optimized to obtain a ratio with better heat exchange efficiency. You can also choose high-performance corrugated inner finned tubes, which not only enhance heat transfer on the fluorine side, but also on the water side.
3. Water flow between baffle and shell
Although the heat transfer coefficient on the water side is higher than that on the fluorine side, if there is water leakage between the baffle and the shell, it seriously affects the heat transfer on the water side. In order to reduce the adverse effects of water seepage, in addition to taking measures on the baffle structure, the water velocity on the shell side can also be optimized to obtain a relatively reasonable water velocity, such as 1.2-2.0m/s.
4. Mass flow rate inside the pipe
It can be found from the equation of heat transfer through evaporation inside the tube that evaporation inside the tube is significantly affected by the mass flow rate of the refrigerant inside the tube; Moreover, as the length of the evaporative heat exchange tube changes, the mass flow rate of the refrigerant gradually decreases. As a result, the heat release coefficient of refrigerant evaporation gradually decreases along the length of the heat exchange tube, and the heat release coefficient of the latter process is much lower than that of the previous process. Therefore, calculations and optimizations are carried out for different ranges of refrigerant flow rates to obtain a reasonable range of refrigerant flow rates with higher evaporation heat transfer coefficients.
5 subcoolers
The use of a subcooler in the condenser can effectively improve the subcooling of the refrigerant, which can reach 7-8 ℃, effectively reducing the supply temperature of the evaporator and thereby increasing the cooling capacity of the chiller.
