The document discusses different types of ventilation systems. Natural ventilation uses natural forces like wind and stack effect to circulate air without mechanical systems. Forced ventilation uses fans and blowers to provide ventilation when natural forces are insufficient. Hybrid ventilation relies primarily on natural ventilation but uses mechanical systems to supplement airflow when needed. Evaporative cooling is also discussed, which uses the evaporation of water to lower air temperature in a cost-effective way. Different fans and their applications are outlined. Two-stage evaporative cooling units that provide initial indirect evaporative cooling before direct cooling are described.

1. “VENTILATION
SYSTEM”
PREPARED BY
JITENDRA JHA

2. What is HVAC….???
• H
• V
• AC

3. Ventilation :-
Ventilation moves outdoor air into a building
or a room, and distributes the air within the
building or room. The general purpose of
ventilation in buildings is to provide healthy
air for breathing by both diluting the
pollutants originating in the building and
removing the pollutants from it.

4. Purpose of
Ventilation
• Maximum indoor air quality to control temperature,
• Remove odours,
• Replenish oxygen,
• Remove moisture, smoke, heat, dust, carbon dioxide and
airborne bacteria from the indoor space.

5. Types of Ventilation System:
NATURAL
VENTILATION
• Natural ventilation is the process
of supplying air to and removing
air from an indoor space without
using mechanical system
• It refers to the flow of external air
to an indoor space as a result of
pressure differences arising
from natural forces.
FORCED
VENTILATION
• A building ventilation system that
uses powered fans or blowers to
provide fresh air to rooms when
the natural forces of air pressure
and gravity are not enough to
circulate air through a building.
HYBRID
VENTILATION
• Hybrid (mixed-mode) ventilation
relies on natural driving forces to
provide the desired (design) flow
rate. It uses mechanical ventilation
when the natural ventilation flow
rate is too low

6. Selection Parameters
• Calculation of Ventilation capacity.
• Selection of techno-economical system.
• Equipment selection.
• Designing Air distribution system.
• Evaluation of system to be used.
• Need/Requirement of client
• Use of Space
• Outside condition
• Aesthetic
• Floor layout
• Location and dimension of beam/Column
• Power availability
• Water availability
• Space availability
• And many more…

7. Natural ventilation:
DESIGN ASPECTS :
 Building orientation and
location.
 Building form and dimensions.
 Window typologies and
operations.
 Types, shapes and size of
openings
 Construction methods and
detailing.
PRINCIPLE :
STACK EFFECT:
Internal and solar heat gain results in a higher temperature inside the
building. This causes an updraft. If a opening, which is the constriction in
the inlet-exhaust system, is located at the highest point of the roof, a
plenum of air with a positive pressure is built up below the constriction
and an assured exhaust through this opening is obtained.
ASPIRATING EFFECT DUE TO THE WIND:
The difference in wind velocities between the outside and inside of the
buildings causes a pressure differential. Since the velocity outside is
much higher than that of the internal air movement, a negative pressure
zone results at certain locations on the external face of the building
envelope.

9. Advantage :
Improved Indoor air quality (IAQ)
Energy Shavings
Reduction of greenhouse gas
emissions
Occupant control
Reduction in occupant illness
associated with Sick building
syndrome(SBS)
Increased worker productivity
Dis-advantage :
Lack of Control
Building Location & Orientation
Difficult to correct problems
Dependency on ambient
condition i.e. Geography

10. Forced ventilation:
FORCED VENTILATION SYSTEMS :
 Evaporative Cooling Unit(ECU)
 Fresh Air Fan unit
 Exhaust Unit
 Exhaust Fans
 And many more….
A building ventilation system that uses
powered fans or blowers to provide fresh
air to rooms when the natural forces of air
pressure and gravity are not enough to
circulate air through a building.

11. Advantage :
Improved Indoor air quality (IAQ)
Control on ventilation capacity
Reduction of greenhouse gas
emissions
Occupant control
Reduction in occupant illness
associated with Sick building
syndrome(SBS)
Increased worker productivity
Dis-advantage :
Capital cost and Operating Cost is
high.
Power consumption is more.

12. Evaporative cooling :
1
2
• Evaporative cooling works by employing water's large
enthalpy of vaporization.
• The temperature of dry air can be dropped significantly
through the phase transition of liquid water to water vapor
(evaporation), which can cool air using much less energy
than refrigeration.

13. Generally lower initial purchase &
Operating costs
It cools up to 15 ºC lower than ambient
temperature based on efficiency of Cooling
pad.
Lower peak energy usage
Zero greenhouse gas production.
Allows flow through ventilation, with
plenty of fresh air
In dry areas, the higher humidity is
beneficial (Refrigerated systems dehydrate
the air too much on a dry day)
Some people prone to allergens find the
wet air less irritating
There is not necessary to have isolated
area, door or window to be closed etc.
Evaporative system depends on ambient
condition i.e. dry bulb and wet bulb.
It does not have control on humidity.
In monsoon season it does not work
properly as air conditioning does.
Temperature and humidity is not that
much achievable as compare to air
conditioning system
ADVANTAGE
DISADVANTAGE

14. Water evaporates directly into the air stream, thus
reducing the air temperature while humidifying the air.
DIRECT EVAPORATIVE COOLING (DEC)
Primary air is cooled sensibly with a heat
exchanger, while the secondary air
carries away the heat energy from the
primary air as generated vapor.
INDIRECT EVAPORATIVE COOLING (IEC)
There are two approaches to evaporative cooling
1
4

15. Two stage ECU(IDEC):
• In two stage cooling (also referred to as indirect / direct evaporative cooling), the primary air stream is
first pre-cooled sensibly by indirect evaporative cooling. Since this pre-cooling adds no humidity to the
air, it can still be subsequently direct evaporative cooled, which is carried out in a direct evaporative
section with a rigid pad. However, since the pre-cooled air can hold less moisture, the final relative
humidity is lower (about 60% to 65%) than that reached with direct evaporative cooling.
• In the first stage, hot outside air passes
inside a heat exchanger that is cooled by
evaporation on the outside. During this
initial cooling phase, the incoming air
stream doesn't pick up any extra
moisture. In the second stage, the same
air stream passes through a water-soaked
pad where the additional cooling takes
place and the air picks up some
additional humidity.

16. :
Working of Two Stage ECU system

17. Types of Fans:
Centrifugal fans use the kinetic energy of
the impeller to increase the volume of the air stream,
which in turn moves them against the resistance
caused by ducts, dampers and other components.
Centrifugal fans displace air radially, changing the
direction (typically by 90°) of the airflow. They are
sturdy, quiet, reliable, and capable of operating over a
wide range of conditions.
Axial fans The blades of the fan force air to
move parallel to the shaft about which the
blades rotate.
Axial fans are typically used for exhausting
dirty air or fumes from processes (such as
paint spray booths), supplying fresh air, and
general spot cooling of people, rooms or
machinery.

18. HVLS Fans
(High Volume low speed fan)
• An HVLS fan is a large ceiling fan
that moves a High Volume of air at
a Low Speed. The low speed
delivers gentle air movement rather
than disruptive wind, and
circulating a high volume of air
effectively distributes airflow over a
large area.
Fan Size(Dia.) Area Coverage
10-feet 5000 Sqft
12-feet 7200 Sqft
16-feet 14400 Sqft
20-feet 25000 Sqft
24-feet 39500 Sqft

19. HVLS Fans(as per Interior)

20. HVLS Fans Working:

21. Hybrid ventilation:
Hybrid (mixed-mode) ventilation relies on natural driving
forces to provide the desired (design) flow rate. It uses
mechanical ventilation when the natural ventilation flow
rate is too low
Hybrid ventilation solutions will use a mixture of both
natural and mechanical ventilation, but should utilise the
natural ventilation as much as possible, as this is based on
the principle of providing healthy indoor climates and
comfort, delivered with minimal energy consumption and
therefore at minimal cost.
For example, in periods of low wind, mechanical
ventilation systems will take over in order to
maintain the internal thermal temperatures and
to ventilate the spaces.

22. Jitendra Jha