Ventilation
Topic -Ventilation
It is a process in which air is replaced or exchanged for a particular area to control moisture, odours, smoke, heat, dust airborne bacteria,
carbon-di-oxide and maintaining oxygen level.
It has two types first one is
1)natural ventilation in which air is exchanged naturally, no external machine is used
2) the second one is forced Ventilation (Mechanical Ventilation)
in which air is exchanged forcefully by means of fans.
Ex. Kitchens exhaust, Basement (car park) exhaust.
Types of
ventilation Fan mostly used
1) Wall Mounted
Propeller fan
In this type of fan air
flows in parallel to the shaft.
A wall-mounted fan is a
machine used to create flow within a system, typically a gas like air.
It consists of a rotating arrangement of vanes
or blade which act on the fluid. Usually, it is contained within some form of
housing or case. This may direct the airflow or increase safety by preventing the object from contacting the fan blades.
Mostly these types of
fan use in toilet, pantry for exhaust and fresh air purpose.
2) Inline
Centrifugal fan
A centrifugal fan is a fan in which air flows in a radial or perpendicular direction relative to
the fan shaft. This fan is specially designed to be connected to ductwork
in direct line with discharge from housing.
These fans contain scroll-shaped fan housing.
it is available in circular and cabinet. It is mostly used for because it offers to speed controllable, maintenance-free, can be installed outside.
3) Axial Fan
It is mostly used for
commercial application. It uses axial forces to achieve movement of air or gas,
spinning a central hub with the blade extending radially from its outer diameter.
The fluid moves parallel to the fan wheels shaft or its axis of rotation.
An axial fan consists
of much fewer blades i.e., two to six, as compared to the ducted fan.
Axial fans operate at
high specific speed i.e., high flow rate and low head and hence
adding more blades will restrict the high flow rate required for its operation.
The axial fan wheel is
often contained within a short section of cylindrical ductwork, to which inlet
and outlet ducting can be connected.
Axial fan available of
two type
Vane axial
These axial flow fans have a higher-pressure capability due to the
presence of static vanes.
These fans highly
efficient as compared to tube axial fan.
Tube axial
These are axial
fan units with fan wheels located in cylindrical tubes, without inlet or outlet dampers. It has medium pressure,
high flow capability.
4) Roof Mounted fan
Roof exhaust fan
generally exhausts the air out of the building. It mostly called Roof Extractor.
It has a simple design
and suitable for fixing on the inclined roof. The equipment contains one M.S.
cowl for rain protection, Axial Flow Fan having cast aluminium alloy impeller of
aerofoil design fitted on motor's shaft. It is better suited for relatively
clean air systems, Roof exhaust fan suitable for commercial application like
warehouses, hospitals, retails stores.
5) Jet fan
This type of fan develops
for ventilation in tunnels and now it is widely used in basement car parking
areas also. It works by propelling. A small jet of air at extremely high
velocity which causes surrounding air to be entrained and in a confined space
like a tunnel or car park. It is used to reduce ductwork and to drive the smoke
toward extract fan to keep pollution within the acceptable limit.
Ventilation air quantity the calculation for fresh /Exhaust air
Fresh air
Formula(Q) - N x
V
N-Air change rate
V-Volume of room (m³)
Q-Fresh air quantity (CMH)
Air change Rate(N)
1.General space - 4ACPH
2.Auditorium - 8 to15
ACPH
3.Bakeries/Bars- 20 to
30 ACPH
4. Class Room-6 to 20
ACPH
5. Pump rooms-5 ACPH
6.Residential toilet-8
ACPH
7.Commercial kitchen
& toilet-12 to 15 ACPH
8.Office-3 to 4 ACPH
9.Computer Room-15 to
20 ACPH
10. Warehouses-6 to 30
ACPH
11. Theaters- 8 to 15
ACPH
12.Substation, electric-5
to 10 ACPH
13. Museums-12 to 15
ACPH
14. Cafeterias-12 to 15
ACPH
Exhaust air
Formula(Q) - (N x
A x H)/60
N-Air change rate
A-Area of room (SQFT)
Q-Exhaust air quantity
(CMF)
H-Height of room (Ft)
Air change Rate(N)
1.Basement parking-15
to 30 ACPH
2.Commercial Kitchen
& toilet-15 to 30 ACPH
3.Lab-6 to 12 ACHP
4.Warehouse-1 to 2 ACPH
5.Smoking room-10 to 15
ACPH
6.Residential toilet-10
to 15 ACPH
7.Classroom-3 to 4 ACPH
8.Smoke exhaust
Basement -30 ACPH &
Above Gr. Floor ACPH
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