Air Conditioning systems use an air distribution network by ducts to circulate conditioned air to all the conditioned spaces in retail, office or residential buildings. To maintain uniform temperature throughout the space efficiently, the system should be designed properly.
Ducts can be classified by its applications and pressure.
Applications
Residential, Commercial and Industrial Applications
Pressure
Low Pressure (Velocity ≤ 10m/s & Static Pressure ≤ 50mm Wg)
Medium Pressure (Velocity ≤ 10m/s & Static Pressure ≤ 150mm Wg)
High Pressure (Velocity ≥ 10m/s & Static Pressure 150mm ≤ Ps ≤ 250mm wg)
Air Velocities should be within the acceptable range to reduce noise.
Recommended air velocities mainly depend on the areas to be served and noise criteria.
Acceptable range of air velocities are
Residence Application 3m/sec to 5 m/sec
Theaters 4m/sec to 6.5 m/sec
Hotels 7.5m/sec to 10m/sec
Normally 8 to 10 m/sec is used for Main ducts flow and 4 to 6 m/sec is used in branch ducts. The maximum of 30 m/sec is used in ships and aircrafts to reduce the requirement of space.
Ducts are commonly fabricated from galvanized steel in rectangular and circular shapes. In air conditioned application, it will be insulated with insulation materials such as nitrile rubber, fibre glass etc. In external areas, insulation will be covered with aluminum cladding to prevent it from damage.
Galvanised sheet of various thicknesses has been used for duct construction. It depends on duct width. Recommended thicknesses are
Upto 300mm 0.55 to 0.7 mm (26G & 24 G)
300mm to 1500mm 0.85 mm (22 G)
1500mm to 2250mm 1.066mm (20 G)
2250mm and above 1.3mm (18 G)
In some applications, aluminium, stainless steel fabricated ducts will be used such as kitchen extraction ducts etc.
Now a day, polyurethane and phenolic panels are used as pre insulated ducts. 80 microns thickness is considered for internal use and 200 microns thickness is considered for some external use.
6 comments:
I thought it was 250 microns???
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Most homes today contain heating, ventilating and air conditioning systems. These systems need to be clean in order to be at their utmost best as far as efficiency is concerned.
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This is really proved worthwhile for my Air business. It controls the indoor air quality by reducing pollutants.
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