Several key energy efficiency indicators about air compressor units

1) The specific power of the unit

Unit specific power: refers to the ratio of air compressor unit power to unit volume flow under specified operating conditions. The unit is: KW/m³/min

It can be easily understood that the specific power reflects the power of the unit required to generate the same amount of gas under the rated pressure of the unit. The smaller the reaction unit, the more energy-efficient it is.

Under the same pressure, for a fixed-speed air compressor unit, the specific power is directly an indicator of the energy efficiency at the rated point; for a variable-speed air compressor, the specific power reflects the weighted value of the specific power at different speeds, which is The energy efficiency response to the integrated operating conditions of the unit.

Generally, the specific power index is an important parameter considered by the customer when the customer selects the unit. Specific power is also an energy efficiency index clearly defined in "GB19153-2019 Energy Efficiency Limits and Energy Efficiency Grades of Positive Displacement Air Compressors". However, it must be understood that in actual use, it is not necessarily that a unit with superior power is more energy efficient than a unit with average power in the customer's use. This is mainly because the specific power is the feedback efficiency of the unit under the specified working conditions, but when the customer uses the air compressor, there is a factor that changes the actual working condition. At this time, the energy-saving performance of the unit is not only related to the specific power. It is also closely related to the control mode of the unit and the selection of the unit. So there is another concept of energy saving performance.

2) Unit energy consumption of the unit

The unit energy consumption of the unit is the measured value. The method is to install a flow meter at the exhaust port of the unit normally used by the customer to count the exhaust gas generated by the air compressor during the entire working cycle, and at the same time install an electric energy meter for the unit to count the power consumption during the entire working cycle. In the end, the unit energy consumption in this working cycle is = total power consumption ÷ total gas production unit: KWH/m³

It can be seen from the above definition that the unit energy consumption is not a fixed value, but a test value, which is not only related to the specific power of the unit, but also related to the actual operating conditions. For the same machine, the unit energy consumption is basically different under different working conditions.

Therefore, when choosing an air compressor, on the one hand, it is necessary to choose a unit with relatively good specific power. At the same time, the customer needs to fully communicate with the pre-sales engineer of the air compressor before selecting the model, and the air consumption and air pressure in use. The situation is fed back. For example, if the gas pressure and gas consumption are constant and continuous, the specific power of the unit has an important impact on energy saving, and the control method is not the main energy saving method. At this time, the power frequency unit with two-stage high-efficiency head can be selected as the selected unit; if the gas consumption fluctuates greatly at the customer, the control method of the unit becomes the main means of energy saving. At this time, the air compressor controlled by frequency conversion must be selected machine. Of course, the efficiency of the machine head also has an impact, but it is in a secondary position compared to the energy-saving contribution of the control method.

The above two indicators, we can make an analogy from the automobile industry that we are familiar with. The specific power of the unit is similar to the "Comprehensive fuel consumption of the Ministry of Industry and Information Technology (L/100km)" posted on the car. This fuel consumption is obtained by testing the specified working conditions and reflects the fuel consumption at the working point of the car. So as long as the model of the car is determined, this comprehensive fuel consumption is a fixed value. This comprehensive fuel consumption is similar to the unit specific power of our air compressor.

Another indicator of the car is the actual fuel consumption of the car. When we drive, we will use the odometer to record the total mileage and the actual total fuel volume at the same time, so that after the car has been running for a period of time, the actual fuel consumption can be calculated from the recorded actual mileage and the actual fuel volume. This fuel consumption is related to the driving conditions, the control method of the car (for example, the automatic start-stop function is similar to the automatic sleep wake-up of the air compressor), the transmission type, and the driver's driving habits. Therefore, the actual fuel consumption of the same car under different working conditions is also different. Therefore, before choosing a car, you should fully understand the working conditions of the car, such as whether it is used at low speed in the city or often at high speed, so as to choose a more energy-efficient car suitable for actual use. It is also the same for us to understand the working conditions before selecting an air compressor. The actual fuel consumption of the car is similar to the unit energy consumption of the air compressor unit.

Finally, briefly explain the mutual conversion of the following indicators:

1. Comprehensive specific power (KW/m³/min) = unit energy consumption (KWH/m³) × 60min

2. Integrated unit power (KW) = integrated specific power (KW/m³/min) × integrated gas volume (m³/min)

3. 24 hours a day comprehensive power consumption (KWH) = comprehensive unit power (KW) × 24H

These conversions can be understood and memorized by the unit of each indicator parameter.