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11 Mechanical Ventilation

Measurements of Airflow

Air flow can be measured in terms of:

  1. Volumetric flow
  2. Mass airflow

Units of volumetric airflow rates are generally expressed in:

  1. 1. Litres per seond (1/s)
  2. Cubic metres per second (m3/s)
  3. Litres per hour(I/h)
  4. Cubic metres per hour (md/h).

NOTE: 1000 litres —— 1m*.

Mass airflow rates are frequently used for air conditioning calculations, but are rarely used for general mechanical ventilation calculations.

Mass airflow rates are generally expressed in kilograms per second (kg/s).

Where a mass airflow rate is used, it can be converted to volumetric airflow by multiplying the value, by the density of the air being considered. For general ventilation calculations, the density of air can be assumed at 1.2m3/kg.

Compiled and published by: The Institute of Plumbing
  Last revision: 2002
  Edition: 1
  Number of pages: 8
  Format: PDF