Do you know these major problems quietly affect the cooling capacity and energy consumption?

There is a close and direct relationship between the cooling capacity of refrigeration equipment and the operating conditions of the system. The cooling capacity and energy consumption are not static, but will change significantly with the changes in operating conditions and differences in operation and management methods. This article explains in detail.

1. Effect of evaporation temperature
Evaporation temperature is a key parameter in the refrigeration system. As the evaporation temperature decreases, the compressor needs to overcome a larger pressure difference to complete the compression process, which leads to an increase in the compression ratio. The increase in compression ratio means that the compressor needs to consume more energy when compressing the refrigerant gas, which in turn increases the energy consumption per unit of cooling capacity. When the evaporation temperature decreases by 1°C, the power consumption of the compressor will increase by 3% - 4%.

Therefore, from the perspective of energy saving and improving the environmental quality of the cold room, the evaporation temperature difference should be reduced as much as possible in actual operation and the evaporation temperature should be appropriately increased. This can not only save electricity, but also increase the relative humidity of the cold room, creating a more suitable environment for storing items.

2. The influence of condensation temperature
The condensation temperature also has an important impact on the performance of the refrigeration system. The increase in the condensation temperature will increase the compression ratio of the compressor, similar to the situation where the evaporation temperature is reduced, which will also increase the energy consumption per unit of cooling capacity. Within the condensation temperature range of 25℃ - 40℃, the power consumption of the compressor will increase by about 3.2% for every 1℃ increase. Therefore, controlling the condensation temperature within a reasonable range is crucial to reducing energy consumption and improving refrigeration efficiency.

3. The influence of the oil layer on the heat exchange surface
During the operation of the refrigeration system, the heat exchange surfaces of the condenser and evaporator may be covered with an oil layer. The presence of the oil layer will greatly affect the heat exchange effect, causing an increase in the condensation temperature and a decrease in the evaporation temperature. This will result in a decrease in the cooling capacity of the refrigeration system and an increase in power consumption.

For example, when the inner surface area of ​​the condenser has an oil layer of 0.1mm thick, the compressor's cooling capacity will decrease by 16.6%, while the power consumption will increase by 12.4%. Similarly, if the inner surface area of ​​the evaporator has an oil layer of 0.1mm thick, in order to maintain the established low temperature requirements, the evaporation temperature will decrease by 2.5℃ and the power consumption will increase by 9.7%. Therefore, regularly cleaning the oil layer on the surface of the condenser and evaporator is an important measure to ensure the efficient operation of the refrigeration system.

4. The influence of air
If air accumulates in the condenser, it will cause an increase in the condensation pressure. The increase in the condensation pressure will increase the working load of the compressor, thereby increasing the power consumption. When the non-condensed gas partial pressure reaches 1.96×10^5Pa, the power consumption of the compressor will increase by 18%. Therefore, during the installation and maintenance of the refrigeration system, it is necessary to ensure the sealing of the system to prevent air from entering the condenser, and at the same time, the system is regularly exhausted to ensure the normal operation of the condenser.

The effect of frost layer
In a refrigeration system operating in a low temperature environment, the surface of the evaporator is easily covered with a layer of frost. The presence of the frost layer will reduce the heat transfer coefficient of the evaporator and reduce its heat transfer efficiency. Especially when the outer surface of the fin tube is frosted, it not only increases the heat transfer resistance, but also hinders the air flow between the fins, further reducing the heat transfer coefficient and heat dissipation area of ​​the surface.

When the indoor temperature is lower than 0℃ and the temperature difference between the two sides of the evaporator tube group is 10℃, after one month of operation of the evaporator, its heat transfer coefficient will drop to about 70% before frosting. Therefore, it is necessary to regularly defrost the evaporator to ensure its normal heat exchange performance.

Shanghai KUB Refrigeration Equipment Co., Ltd.

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