Air compressor inlet flow and exhaust flow

Regarding the intake flow and exhaust flow of the air compressor, the following are explained from four aspects: technical definition, working principle, influencing factors and conversion standards:

1. Core definitions and concepts

1. intake air flow rate
   Refers to the volume of air entering the air compressor per unit of time, usually incubic meters per minute (m³/min)for units. There are two types of measurement standards:
   • Intake position volumetric flow: Air flow (ICFM) measured at the compressor’s first stage inlet flange under local intake conditions.
   • Volume flow rate in intake state: Convert the exhaust flow to the intake state volumetric flow (ACFM) at the first stage inlet flange, also called the actual intake flow.
2. exhaust flow
   Refers to the volume of compressed air discharged by the air compressor per unit of time, usually incubic meters per minute (m³/min)orLiters per minute (L/min)for units. According to industry standards, exhaust volume needs to be converted tostandard conditionsFlow rate (Nm³/min) at (0℃, 1 standard atmosphere pressure, dry air).

2. Working principle and flow changes

Taking screw air compressors as an example, the work process is divided into three stages:

1. inspiration phase: The rotation of the rotor increases the suction volume, and external air enters the compression chamber through the intake filter.
2. compression stage: As the rotor rotates, the suction volume decreases, the air is compressed, and the temperature increases simultaneously.
3. exhaust phase: The compressed air is exhausted through the exhaust port and enters the air storage tank or direct gas consumption equipment.

Flow change law：

• The intake air flow rate is affected by ambient temperature, pressure, and humidity, and the actual value needs to be corrected by a formula.
• The exhaust flow is affected by the compression ratio. The larger the compression ratio (the higher the exhaust pressure), the smaller the exhaust flow.

3. Key influencing factors

1. device type：
   • The exhaust flow of the screw air compressor is stable, and the flow of the piston air compressor fluctuates greatly.
2. Compression ratio and speed：
   • Compression ratio ↑ → exhaust flow ↓; speed ↑ → both intake and exhaust flow ↑.
3. inlet conditions：
   • Intake pressure ↓ (such as high altitude areas) → intake air flow ↓; intake air temperature ↑ → air density ↓ → intake air flow ↓.
4. System leaks and cooling efficiency：
   • Poor seals or clogged coolers can reduce exhaust flow.

4. Industry conversion standards and cases

1. Standard flow conversion formula：
   According to the gas equation of state PV/T=constant, convert actual flow to standard flow:

Vactual​=Pactual​×Tstandard​Pstandard​×Vstandard​×Tactual​​

Among them:

• Pstandard​=101.33kPa, Tstandard​=273.15K（0℃）。
• Pactual​、Tactual​ It is the local atmospheric pressure and intake air temperature.

2. actual case：
   If the standard flow is required to be 300Nm3/min, the actual local conditions are:
   • atmospheric pressure 99.12kPa, temperature 35℃, relative humidity 85%。
     The actual intake air flow after conversion is approximately 371.4m3/min。

5. Selection and use suggestions

1. selection principle：
   • High temperature or high altitude areas need to choose an air compressor with a larger nominal volume flow.
2. maintenance points：
   • Regularly clean the intake filter and check the efficiency of the cooler to ensure stable flow.
3. monitoring indicators：
   • Monitor standard flow in real time through a flow meter to avoid insufficient pressure or energy waste.

summary: The intake flow and exhaust flow of the air compressor are affected by many factors such as equipment type, working conditions, and compression ratio. The actual selection needs to be combined with comprehensive calculation of standard flow conversion and local environmental parameters.