The cooling capacity of refrigeration equipment is directly related to the operating conditions of the system. For compressors whose structure, speed, and refrigerant type have been determined, their cooling output and energy consumption will undergo significant changes with changes in operating conditions and operational management.
1, The relationship between cooling capacity and energy consumption
The influence of evaporation temperature: As the evaporation temperature decreases, the compression ratio of the compressor will increase, leading to an increase in energy consumption per unit of cooling output. Specifically, for every 1 ℃ decrease in evaporation temperature, power consumption increases by 3% -4%. Therefore, in order to save electricity and increase the relative humidity of the cold room, the evaporation temperature difference should be minimized as much as possible and the evaporation temperature should be increased.
The impact of condensation temperature: An increase in condensation temperature also leads to an increase in the compression ratio of the compressor, thereby increasing the energy consumption per unit of cooling output. Within the condensation temperature range of 25 ℃ -40 ℃, for every 1 ℃ increase, the power consumption will increase by about 3.2%.
The influence of oil layer on the heat exchange surface: When the heat exchange surfaces of the condenser and evaporator are covered by oil layer, it will cause an increase in condensation temperature and a decrease in evaporation temperature, thereby reducing the cooling capacity and increasing power consumption. For example, if there is a 0.1mm thick oil layer on the inner surface of the condenser, it will cause a 16.6% decrease in compressor cooling capacity and a 12.4% increase in power consumption; Similarly, if there is a 0.1mm thick oil layer on the inner surface of the evaporator, in order to maintain the predetermined low temperature requirements, the evaporation temperature will decrease by 2.5 ℃ and the power consumption will increase by 9.7%.
The impact of air accumulation: Air accumulation in the condenser can cause an increase in condensation pressure, thereby increasing power consumption. When the partial pressure of non condensable gas reaches 1.96 × 10 ^ 5Pa, the power consumption of the compressor will increase by 18%.
The impact of scale: If there is a 1.5mm thick scale on the condenser tube wall, it will cause the condensation temperature to rise by 2.8 ℃ and the power consumption to increase by 9.7%.
The influence of frost layer: If the evaporator surface is covered with a layer of frost layer, its heat transfer coefficient will be reduced. Especially when frost forms on the outer surface of finned tubes, it not only increases the heat transfer resistance, but also makes it difficult for air flow between fins, thereby reducing the heat transfer coefficient and heat dissipation area on the surface. When the indoor temperature is below 0 ℃ and the temperature difference on both sides of the evaporator tube group is 10 ℃, the heat transfer coefficient of the evaporator will decrease to about 70% of before frosting after one month of operation.
The impact of superheat: The gas sucked in by the compressor is allowed to have a certain degree of superheat, but when the superheat is too high, the specific volume of the sucked gas will increase, resulting in a decrease in cooling capacity and an increase in power consumption.
Compressor defrosting treatment: When the compressor defrosts, if the suction valve is quickly turned down to reduce low cooling capacity, it will relatively increase power consumption.
2, Energy saving measures for refrigeration operation
In order to improve the economic efficiency of refrigeration systems, it is necessary to strengthen the operation and management of refrigeration equipment and take effective energy-saving measures.
Strengthen equipment operation management: Establish a system for electricity management and unit consumption statistics to facilitate the assessment of electricity and material consumption quotas. At the same time, necessary measuring instruments and devices should be added to carry out energy-saving and technological transformation work.
Correctly control and regulate the system's liquid supply: avoid the occurrence of excessive humidity and overheating in the compressor's suction to ensure stable system operation and reduce energy consumption.
Reasonably select the number of compressors in operation: match the corresponding cooling capacity according to the system's thermal load to reduce unnecessary energy consumption.
Adjust the number of operating fans and water pumps: Adjust the number of operating fans and water pumps appropriately according to process requirements and changes in external temperature to optimize energy consumption.
Regular maintenance of equipment: Regularly drain oil, air, defrost, and remove scale to maintain good heat transfer efficiency of the equipment and avoid increased energy consumption caused by high condensation pressure and low evaporation pressure.
Improving water quality: By improving water quality to slow down scaling and enhance the condensation efficiency of the condenser, the condensation temperature and energy consumption can be reduced.
Optimize motor load factor: When the load factor of the refrigeration equipment motor is below 0.4, the motor can be changed from △ to Y connection to improve power factor, and it is required that △ and Y connections can automatically switch to adapt to different load conditions.
Adopt automatic control operation: Try to use automatic control operation instead of manual operation to achieve optimal operation of the refrigeration system. This can not only improve the stability and reliability of the system, but also save electricity.
In summary, by strengthening the operation management of refrigeration equipment, adopting effective energy-saving measures, and improving the working conditions of equipment, the economic benefits of refrigeration systems can be significantly improved and energy consumption can be reduced
