Air flow calculation
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Gentlemen, I need help with converting the flow rate under operating conditions to the flow rate under standard conditions. Different manufacturers give me different values, which confuses me. The requirements at the point of use are as follows: air volume of 7000 m3/h, pressure of 0.25 MPa, operating temperature of 55°C, local atmospheric pressure of 83 kPa, humidity of 74%, and an average temperature of 28°C. What is the standard condition flow rate in Nm3 that the air compressor needs to produce in order to meet these requirements? The result I obtained is 19,155 Nm3/h. My calculation formula is as follows; I would appreciate it if experts could help me and correct any mistakes. :L
I understand the calculation process as follows: When the local atmospheric pressure is 83 KPa, the relative humidity is 0.74, and the temperature is 28°C, the saturated vapor pressure of water is 3.717 KPa. Therefore, the partial pressure of water in the air is 3.717 * 0.74 = 2.75 KPa. The molar ratio of water in the air is 2.75/83 = 0.03313; the remaining value represents the molar ratio of dry air, which is 0.96687. I’m not quite sure what 7000 m3 and 0.25 MPa refer to for now. If we calculate based on the required amount of 7000 cubic meters of dry air, then at 0.25 MPa and 55°C, 7000 m3 of dry air corresponds to 641.44 kmol. Then, the air at 28°C, 83 KPa, and 0.74 relative humidity has a volume of 663.4 koml. Converted to 14,460 Nm3 at standard conditions. The main question is that it’s not clear what exactly is meant by 7000 m3, 0.25 MPa, and 55°C.
This post was last edited by wdzs0312 on 2021-5-14 at 14:20 1
55℃ Explanation: The temperature at the outlet of the air compressor is higher than the local ambient temperature; therefore, the compressed air is first cooled below its dew point before water is removed from it, and then the temperature is raised to 55℃ to decompose any remaining water droplets. 0.25 MPA: The pressure in the pipeline between the outlet of the air compressor and the equipment in use is 0.25 MPA. 7000 cubic meters: Under conditions of 0.25 MPA and 55℃, the equipment requires 7000 m3/h of air