AIR Flow Studies (MODEL ME-FM-1231E-R)

The ARL’s 1231E Air Flow Studies Unit has been designed to demonstrate how to measure the important characteristics of industrial air-distribution systems. It also shows how certain basic principles of fluid mechanics are applied to analyse flow in ducts and jets.

  • The 1231E unit is self-contained and only requires connection to a single-phase mains electrical supply
  • Turbulence in the 80mm diameter test pipe is minimised by locating the pipe at the inlet of the centrifugal fan
  • A profiled bell-mouth inlet prevents air separation from the wall of the pipe at the entrance and straightening vanes suppress the formation of vortices
  • Tappings along the test pipe enable the pressure gradient to be measured with air velocity variable up to a maximum of 35 m/s
  • A Pitot tube can be traversed across the pipe at five locations to enable boundary layer growth/development of velocity profiles to be determined
  • Air flow rate is determined from differential pressure measurements across an orifice plate or two different inlet nozzles
  • Different bends and elbows can be fitted to enable frictional losses in fittings to be compared
  • Air-jet dispersion experiments are carried out on the discharge side of the fan
  • A Pitot tube can be traversed laterally (across) and longitudinally (along) the jet to measure the changes in velocity as the jet disperses
  • All pressure measurements are performed using a bank of 14 manometer tubes that can be inclined to increase sensitivity
  • An instruction manual is supplied that describes how to perform the air flow experiments and interpret the results, as well as how to install, commission and maintain the equipment
  • Practical demonstration of the quantitative flows in geometries as described in the laws of conservation of mass and momentum
  • Using manometers to measure pressure drop
  • Using a Pitot-static tube to measure flow
  • Employing nozzles and orifices to measure flow
  • Understanding and measuring velocity profiles
  • Relating pressure loss in a duct to flow rate
  • Measuring the flow resistance of duct fittings
  • Understanding the use of Reynolds’ numbers
  • Measuring the dispersion of a jet

The 1231E equipment comprises a long smooth walled pipe connected to the suction side of an electrically driven centrifugal fan. The fan discharge pipe terminates in a flow-control damper for closed-conduit work, or a plate containing a small aperture for jet-dispersion measurements.

Air enters the smooth walled pipe through one of the two flow-measurement nozzles provided. Pressure tappings along the length of the pipe permit the pressure gradient to be determined.

A bend or mitred cascade elbow may be fitted midway along the smooth wall pipe for comparison of pressure losses.

Boundary layer growth is determined by the measurement of the velocity profile at five stations along the pipe using a traversing Pitot tube.

A conventional flow-measuring orifice plate is supplied for installing in the pipe upstream of the fan for additional demonstrations of pressure loss and recovery.

Air-jet studies are carried out on the discharge side of the fan. A Pitot tube is traversed vertically and horizontally at different distances from the discharge orifice to investigate the dispersion properties.

The equipment is mounted on a floor-standing steel frame with an adjacent support for the extended suction pipe.

Pressure measurements are made on a multi-tube inclinable manometer mounted on the support frame.

An electronic manometer bank with data logging software is available as an accessory.

Centrifugal fan capacity:218 l/s at STP
Pipe velocity range:0-35 m/s
Inlet pipe:Diameter: 80mm
Length: 2.75m
Interchangeable nozzles:Diameter: 50mm and 80mm
Internal pipe orifice:Diameter: 50mm
Jet discharge pipe orifice:Diameter: 30mm
Jet traverse range
(downstream length x width):
600mm x 140mm
Manometer range:0-283mm H2O
Manometer fluid:Kerosene (sg 0.78)
Electrical supply:


Gross weight:220kg
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