How to Calculate Suction Volume by Compressor Discharge Volume

The calculation of suction volume by compressor displacement should be combined with thermodynamic principles and compressor performance parameters, the specific steps are as follows:

1. Core Formula Derivation

according to the law of conservation of mass:

q_{suction} = Q_{row} times frac{P_{row }}{ P_{suction}} times frac{T_{suction }}{ T_{row}} times frac{eta_{ capacity} times eta_{ temperature rise}}

among them:

• Q suction: suction volume (m & sup3;/min)
• Q exhaust: exhaust volume (m & sup3;/min, need to be converted to the standard value of the same temperature and pressure)
• P row/P suction: compression ratio
• T suction/T row: temperature correction coefficient (polytropic process shall be considered in actual calculation)
• & eta; capacity: volumetric efficiency (typical 0.85-0.95)
• & eta; Temperature rise: temperature efficiency correction factor (1 for isothermal compression, <1 for adiabatic compression)

2. simplified calculation model (taking piston compressor as an example)

1. assumption condition:

   • adiabatic compression (& kappa;= 1.4 to air)
   • exhaust temperature T row = T suction ×(P row/P suction)(& kappa;& minus;1)/& kappa;

2. inspiratory volume formula:

Q suction = P suction × T row × & eta; Total Q row × P row × T suction

where & eta; total = & eta; capacity × & eta; machinery, the total efficiency is typically 0.7-0.85.

3. practical calculation example

known conditions:

• displacement Q = 10 m & sup3;/min (standard condition, 1 atm, 20 ℃)
• compression ratio P row/P suction = 7 (from 1 atm to 7 atm)
• suction temperature T suction = 293 K
• total Efficiency & eta; Total = 0.8

calculation process:

1. exhaust temperature:

T row = 293 × 70.286 & asymp;416 k

2. inspiratory volume:

Q suction = 1 × 416 × 0.810 × 7 × 293 & asymp;61.8 m & sup3;/min

4. key correction factor

Factors	correction direction	typical Value Range
clearance volume	decrease inspiratory volume	2%-5%
air valve resistance	decrease inspiratory volume	3%-8%
leakage loss	decrease inspiratory volume	1%-3%
suction gas preheating	increase inspiratory capacity	1%-4%

recommendations for 5. industrial applications

1. direct measurement method: Obtain real-time data through the flowmeter installed in the suction pipe
2. performance curve method: Check the compressor performance curve provided by the manufacturer to match the relationship between compression ratio and suction volume.
3. online monitoring: Deploy IoT sensors to dynamically calculate suction volume in combination with compressor operating parameters

in practical engineering, it is recommended to accurately calculate the parameters such as isentropic efficiency and volumetric efficiency in the original technical manual of the compressor, and to verify the theoretical model by regularly detecting the temperature field distribution through the thermal imager.