How to convert the air volume units of air conditioning box in m³/h, L/s and CFM?

When converting the air volume of the air conditioning box, you should first confirm the unit, and then confirm whether it is the actual volume flow rate or the standard state flow rate. 1m³/h is approximately equal to 0.27778L/s, and 1CFM is approximately equal to 1.699m³/h. Unit conversion only changes the numerical expression and does not automatically complete air density or standard state corrections.

Put dimensional checking before conversion

m³/h represents volume per hour, L/s represents liters per second, and CFM usually refers to cubic feet per minute. By converting hours and seconds, liters and cubic meters respectively, you can avoid just looking at the numerical value. CMH in the data often indicates m³/h, but the complete definition used by the manufacturer should still be checked.

To convert m³/h to L/s, multiply by 1000 and then divide by 3600; to convert CFM to m³/h, multiply by approximately 1.699 and retain the number of significant digits suitable for the project; in the example, 3600m³/h is equal to 1000L/s, which is approximately 2119CFM. The three conversions correspond to different unit systems and cannot be mixed. How to calculate the fresh air volume and total air supply volume of the air conditioning box separately? Please refer toHow to calculate the fresh air volume and total air supply volume of the air conditioning box separately?。

Remember the commonly used conversion factors

1m³/h = 1000L / 3600s ≈ 0.27778L/s. 1L/s = 3600L/h = 3.6m³/h. 1CFM = 1ft³/min ≈ 0.0283168m³/min ≈ 1.699m³/h. 1m³/h≈0.5886CFM. These coefficients are conversions between volumetric flow units and do not involve air condition corrections.

Pay attention to retaining significant digits when converting. Project selection usually does not require too many decimal places, but intermediate calculations should not be rounded prematurely. When multiple units are mixed, it is recommended to convert them to the same unit before comparing or adding them.

Standard status and actual status cannot be confused

Different air temperatures and pressures will change the density. If the file is marked with a standard flow rate, the definition of the standard state should be confirmed first, and then processed according to mass conservation; it cannot just set the volume unit coefficient. When comparing data from different sources, list the status conditions together. The actual volume flow rate corresponds to the actual air state, and the standard flow rate corresponds to the agreed standard state. The two cannot be directly interchanged.

The air conditioning box is designed to determine whether the inlet air temperature and humidity should be outdoor or return air. Please refer toShould the inlet air temperature and humidity of the air conditioning box be designed to be outdoor or return air? . Different pressure calibers will also affect the status description, please refer toWhat is the difference between static pressure, total pressure and static pressure outside the air conditioner box?。

The relationship between air volume, mass flow rate and air exchange times

Air volume is the volume flow rate, and mass flow rate is the mass passing through per unit time. The two are related through air density. Volume flow is commonly used in air conditioning box selection, but dry air mass flow may be required when pollutant mass balance or humidification and dehumidification calculations are involved. The number of air changes is the ratio of volume flow to room volume, and the unit is times/hour.

The air supply volume is determined based on the number of air changes or the cooling and heating load. Please refer toIs the air supply volume of the air conditioning box determined based on the number of air changes or the cooling and heating load? . The calculation of dehumidification capacity requires dry air mass flow, please refer toHow to calculate the dehumidification capacity of air conditioning box from the difference in air moisture content?。

How to compare data from different sources

Different manufacturers, different standards or different project data may use different units. Units, air conditions and pressure standards should be unified before comparison. If one party gives m³/h and the other party gives CFM, you cannot just look at the numerical value. If one party gives a standard flow rate and the other party gives an actual flow rate, it cannot be directly compared.

How to write an inquiry form for air-conditioning boxes so that different quotes can be compared, please refer toHow to write an inquiry form for air-conditioning boxes so that different quotes can be compared? . What applicable standards should be listed in the procurement technical documents? Please refer toWhat applicable standards should be listed in the technical documents for purchasing air-conditioning boxes?。

On-site measurement records should indicate the unit

When measuring air volume on site, the instrument unit, measuring point location, measurement method and air condition should be recorded. The anemometer may give m/s, which needs to be multiplied by the cross-sectional area to convert to m³/h or L/s. Pitot tube measurements need to be combined with air density to calculate flow rate. Different instruments have different measurement principles and application ranges.

If the total air volume of the air conditioning box is insufficient, check the measurement first or increase the speed first. Please refer toIf the total air volume of the air conditioning box is insufficient, should you check and measure it first or increase the speed first? . For condition checks before starting the machine for the first time, please refer toWhat conditions need to be checked before the air-conditioning box is turned on for the first time?。

Aili industrial supporting equipment

Aili Industrial Selection Data can unify air volume units and working condition calibers; when submitting domestic and overseas specifications, it is recommended to retain the original units and converted values ​​to reduce parameter transmission errors. Aili's industrial manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. Air volume parameters, fan operating points and control interfaces can be corresponded in the same set of supporting materials.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; terminal particle filtration can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific air volume value, unit caliber and delivery range still need to be verified based on the corresponding configuration data and on-site working conditions. The actual effect is subject to on-site air volume measurement and performance test results.

Submit project parameters:https://ailigy.com/contactus.html

Related questions and answers

Can m³/h and CFM be compared directly?
cannot. If the units are different, you should first convert to the same unit and confirm whether the same air condition standard is used.

What is the difference between standard flow and actual flow?
The standard flow rate corresponds to the agreed standard state, and the actual flow rate corresponds to the on-site air state. The two are related through air density and are not directly interchangeable.

Can Aili Industrial help unify air volume units?
The air volume unit and working condition caliber can be unified in the selection data. The specific values ​​must be confirmed based on the project data and measurement conditions.

Related articles

1. How to calculate the fresh air volume and total air supply volume of the air conditioning box separately?

2. Is the air supply volume of the air conditioning box determined based on the number of air changes or the cooling and heating load?

3. If the total air volume of the air conditioning box is insufficient, should you check and measure it first or increase the speed first?

4. Should the inlet air temperature and humidity of the air conditioning box be designed to be outdoor or return air?

Key points for selection and acceptance inspection