Are the air compressor air production and exhaust volume the same? What is the difference?

The gas production and exhaust volume of air compressors have important differences in engineering applications. Understanding the essential differences between the two can help correct selection and optimize system efficiency. The following is a detailed comparison of the two:

1.Definition differences

• Displacement Volume：
  • The displacement is the gas displacement capacity of the air compressor under ideal conditions, which is the geometric volume swept by the piston or screw rotor per unit of time. It is the theoretical value when designing the air compressor and does not consider various losses in actual operation.
  • Calculation formula: Exhaust volume = cylinder volume × speed × number of cylinders
  • For example, the theoretical displacement of a 55kW screw air compressor is 10.5 m ³/min (regardless of efficiency losses).
• Gas production (Actual Gas Delivery)：
  • Gas production refers to the actual available compressed air output, which is the result of the exhaust volume after deducting various efficiency losses.
  • The main influencing factors include: volume efficiency loss, intake air temperature, filter pressure loss, etc.
  • For example, the measured gas production of an air compressor is 9.2 m ³/min. After taking into account the ambient temperature, the gas production converted into a standard state is 8.6 m ³/min.

2.standard state conversion

• according toISO 1217Standard, gas production usually needs to be converted to the value under standard conditions (1 bar, 20℃, 0% humidity), which helps to uniformly compare gas production under different working environments.
  • For example, the measured gas production of a certain machine under a 40℃ environment is 9.2 m ³/min, and the temperature correction factor is 0.94, which translates into a gas production of 8.6 m ³/min.

3.parameter comparison

4.Factors affecting gas production

• Mechanical efficiency limitations：
  • Leakage in the rotor clearance of screw machines can cause a flow loss of 8-12%.
  • The clearance volume of reciprocating air compressors can cause a 15-25% reduction in efficiency.
• Environmental factor correction：
  • For every 1000 meters increase in altitude, air density drops by 11%, requiring additional power compensation.
  • When the humidity is higher than 70%, condensed water separates out, resulting in a 3-5% reduction in effective air volume.
• system matching design：
  • Pressure drop in the pipeline: For every additional 50 meters of pipeline, the pressure drop increases by 0.1 bar, resulting in a flow loss of about 2%.
  • Insufficient capacity of the air storage tank will lead to frequent starts and stops, thereby increasing losses.

5.Cases in engineering applications

In practical applications, the nominal exhaust volume of air compressors and the actual gas production are often inconsistent. For example:

• a car factory: An air compressor with a nominal displacement of 20m³/min was purchased, and the actual gas production was only 16.8 m ³/min. Reasons include:
  • Intake pressure loss due to altitude of 1500 meters (correction factor 0.85).
  • Pressure loss in post-treatment equipment (dryer + filter) resulted in a flow attenuation of 6%.

6.Equipment selection and energy efficiency monitoring recommendations

• Precise selection: The actual air demand of the equipment should be equal to the theoretical exhaust volume of the equipment multiplied by the comprehensive efficiency coefficient (usually 0.7-0.85). For example, if the production line requires 12m³/min of air, a model with a nominal displacement of ≥15m³/min. should be selected.
• energy efficiency monitoring: Install a flow meter (accuracy ±1.5%) for real-time monitoring, which meets the requirements of GB/T 13466 standard.
• maintenance optimization: Clean the cooler every month to avoid dirt causing efficiency reduction; replace the intake filter every year to prevent excessive pressure loss.

7.Special considerations for high-end industries

In high-end fields such as pharmaceuticals and semiconductors, in addition to basic environmental factors, gas production also needs to consider special losses:

• Nitrogen purge loss: Clean system replacement gas consumption is 2-3%.
• Online monitoring system sampling flow: Each equipment may consume 0.1- 0.3 m ³/min. of air.

By accurately distinguishing these two parameters, waste and loss caused by wrong equipment selection can be avoided to ensure the performance of the equipment in practical applications.