Armfield Engineering Education
FLUID MECHANICS
F6 Air Flow Studies - Issue 8
The Armfield Air Flow Unit has been designed to demonstrate how to measure the important characteristics of industrial air distribution systems,as well as to show how certain basic principles of fluid mechanics are applied to analyse flow in ducts and jets.
ORDERING SPECIFICATION
• The unit is self-contained and only requires connection to a single-phase electrical supply.
• Turbulence in the 80mm diameter test pipe is minimised by locating the pipe at the inlet of the centrifugal fan.
• A profiled bellmouth 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 allow the pressure gradient to be measured with air velocity variable up to a maximum of 35m/s.
• A Pitot tube can be traversed across the pipe at five locations to allow boundary layer growth/development of velocity profile to be examined.
• Air flowrate is determined from differential pressure measurements across an orifice plate or two different inlet nozzles.
• Different bends and elboes can be fitted to allow 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 fourteen 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.
TOPDemonstration Capabilities
> using the laws of conservation of mass and momentum to describe quantitatively flow in geometries of practical importance
> 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
TOPDescription
The 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 mid way along the smooth wall pipe for comparison of pressure losses.
Boundary layer growth is determined by the measurement of the velocity profile at four 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.
TOPTechnical details
| Item | Value |
|---|---|
| Centrifugal fan capacity: |
218 l/s at STP |
| Pipe velocity range: |
0-35m/s |
| Inlet pipe: |
dia.80mm length 2.75m |
| Interchangeable nozzles: |
dia.50mm and 80mm |
| Internal pipe orifice: |
dia.50mm |
| Jet discharge pipe orifice: | dia.30mm |
| Jet traverse range (downstream lengthxwidth): |
600mm x 140mm |
| Manometer range: | 0 - 283mm H2O |
| Manometer fluid: | Kerosene (s.g.0.78) |
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TOPComplementary Products
F1: Hydraulics Bench and Accessories
F1-301: Computer Aided Learning Programs (PC: WindowsTM)
F5: Osborne Reynolds' Demonstration
F9092: Fluid Properties & Hydrostatics Bench
F1-28: Cavitation Demonstration
F12: Particle Drag Coefficients
F14MKII: Hydrogen Bubble Flow Visualisation System
Requirements
Electrical supply:
F6-A:220-240V/1ph/50Hz
F6-B:120V/1ph/60Hz
Shipping specification
Gross weight:220kg
Volume 2.3m3
Overall dimensions
Height:0.7m
Width:3.8m
Depth:1.9m
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