This article is a guide on the maintenance and design optimization of refrigeration systems, aiming to improve system efficiency, reduce energy consumption, and extend equipment life through a series of measures. The following is a detailed explanation of each point in the paper.

1. Defrost promptly

Evaporators are key components in refrigeration systems that absorb heat to vaporize refrigerants. When frost forms on the outer surface of the evaporator, the frost layer forms an additional layer of insulation, significantly increasing the thermal resistance. Each 1.5 mm increase in frost layer leads to an increase in condensation temperature of about 2.8 degrees and an increase in energy consumption of about 10 percent. Therefore, regular defrosting is essential to keep the system running efficiently.

2. Remove scale regularly

The condenser is responsible for releasing the heat accumulated during the cooling process. When the surface of the scale, such as scale accumulation of 1.5 mm, will lead to condensation temperature rise of about 2.5 degrees, the system energy consumption increased by about 9.7%. Regular cleaning of the condenser can effectively avoid such efficiency losses.

3. Pipeline design and oil return are smooth

Piping should be designed to ensure smooth circulation of refrigerant and lubricating oil. The remaining oil film in the condenser or the increased oil film in the evaporator can significantly affect the efficiency, resulting in an increase in condensing temperature, a decrease in cooling capacity and an increase in energy consumption, respectively. Keeping the pipeline design reasonable helps to smooth oil return and reduce energy consumption.

4. Focus on non-condensing gases

The system is mixed with non-condensible gases such as air, which will occupy a certain volume fraction, and its partial pressure reaches 0.196MPa, increasing the compression work, resulting in an increase in energy consumption of about 18%, while the cooling capacity is reduced by about 8%. Regular emptying of non-condensing gases from the system is a necessary maintenance operation.

5. Influence of condensing pressure and evaporation pressure

The increase of condensing pressure or the decrease of evaporation pressure will directly affect the cooling efficiency. The former will reduce the freezing capacity by 7-10%, and the latter by about 4-5%. Maintaining appropriate pressure conditions is critical to system performance.

6. Simplify piping design

The use of linear piping reduces pressure loss and refrigerant leakage risk. The curvature radius of the bend should be large enough to reduce resistance. The curvature radius of the bend pipe should be more than 4 times the diameter of the pipe, and the pressure loss of the pipe interface, valve and straight pipe is greater than that of the pipe, and it is also easy to produce refrigerant leakage.

7. Nitrogen welding

The use of nitrogen protection during welding can avoid the formation of oxide, ensure welding quality and reduce subsequent maintenance costs. Blow with nitrogen (flow rate 0.05m3/h), otherwise impurities such as oxide are easy to appear.

8. Pipeline inclination and oil return

Ensure that the horizontal pipe has a certain inclination to help the oil return to the compressor smoothly and avoid oil retention affecting the efficiency. At least 1/200 ~ 1/250 inclination, so that the oil return is good. Do not set unnecessary U-shaped pipe or stop pipe in the refrigerant distribution pipe, and the refrigerant oil is easy to slip.

9. Design of suction pipe

Ensure that the refrigerant gas has a sufficient flow rate to carry the oil droplets back, while controlling noise and total pressure loss to keep the system efficient and stable. To ensure that the refrigerant gas flow rate, so that the mixed oil can really return to the compressor (horizontal pipe 3.8m/s above, vertical pipe 7.6m/s above). Limit the speed to a level that does not produce noise (generally below 20m/s). The total pressure loss generated by the suction tube does not exceed the pressure corresponding to 1 degree converted to the standard saturation temperature.

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