Air handling unit

1. AIR HANDLING UNIT
PRARTHNA*
26/MPH/DPSRU/2018
INDUSTRIAL PHARMACY
PRESENTED TO : DR. KEERTI

2. CONTENTS
• Introduction
• Importance
• Air handling unit
• Types of AHU systems
• Component
• Working
• Efficiency
• Reference

3. INTRODUCTION
• "A factory-made encased assembly consisting of a fan or fans
and other necessary equipment to perform one or more of the
functions of circulating, cleaning, heating, cooling,
humidifying, dehumidifying and mixing of air....“
The AHU is used to control the following parameters of the
space.
• Temperature
• Humidity
• Air Movement
• Air Cleanliness

4. HVAC - HEATING, VENTILATION, AIR-
CONDITIONING
• Temperature 68º F (20º C) and 75º F (25º C)
• Humidity 30% relative humidity & 60% RH
• Pressure A slight positive pressure to
reduce outside air filtration
• Ventilation Rooms typically have several complete
air changes per hour

5. IMPORTANCE
• Ensures that a building has proper climate control with heating
and cooling along with the necessary air pressure
and air quality
• Used to make sure that there is no negative indoor air pressure
in a building
• Removes dirt, dust and other unwanted particles from the air
• In dryer environments, humidifier component which adds in
more moisture to the air..
• Some air handling units have dehumidifier components which
are essential for keeping excess moisture out of environments
where it could cause problems with mold, odors or machinery

6. AIR HANDLING UNIT
An air handling unit where (1) is the supply air, (2) fan section, (3) vibration
isolator, (4) cooling coil, (5) filter and (6) mixed air duct

7. AIR HANDLING SYSTEM
• Air handling unit, or AHU, is a piece of HVAC equipment that is designed
to regulate and circulate air throughout a space
• Air handlers typically connect to a ductwork ventilation system that
distributes the conditioned air throughout the building and returns it
back to the unit

8. Warm outdoor and cool indoor air are mixed, cooled by the evaporator, and
circulated using ducts.

9. HVAC SYSTEMS PERFORMS FOUR BASIC
FUNCTIONS:
1. Control air-borne particles, dust and microorganisms.
2. Maintain room pressure (delta P).
3. Maintain Space moisture (Relative humidity)
4. Maintain space temperature.

10. TYPES OF AHU SYSTEM
•"Draw-Through"
• "Blow-Through"

11. DRAW - THROUGH
• In the Draw-Through type
The design can be vertical or horizontal. In this case, the section
before the fan has negative pressure.
fan pulls the air through the
mixing box
filter and cool
discharging it from the fan outlet
to the space to be conditioned

12. BLOW - THROUGH
• In the Blow-Through type , the section after the fan has
positive pressure.
fan blows the air
through the mixing
box
filter and cool
discharging them
to the space being
conditioned or the
ducting system

13. COMPONENTS
Housing
• The housing that contains all the other components of an AHU
is usually make of metal, some are painted to prevent
corrosion.
• In sections where the fans and the coil are located, 1-2 inches
of polyurethane foam or PU is used to insulate them to prevent
the condensation on the panel. Drain pan is also used as a
precaution in the event of condensation of water

14. Fan
• Centrifugal fan is used to circulate the air to the various parts
of the sections in the building. The typical types of fan available
are Backward Inclined, Backward Curved, Forward Curved and
Airfoil.

15. Cooling Coil
• Cooling Coil is used to cool and dehumidify the air. Both DX
(direct expansion) cooling and CW (chilled water) cooling coils
are available for use depending on the system design.
• These coils are arranged in rows with different fin spacing.
Aluminium fins and copper tubes are used in the design of the
coils.

16. Filters
• Filters are to remove particles and contaminants of various sizes
from the air. The type of air filter being used will very much depend
on the application of the system.
• Panel Filter is a flat and rectangular in shape and provides a
minimum low efficiency filtration which is acceptable to the air
conditioning industry.
• HEPA Filter is very efficient and is able to achieve efficiencies up to
99.97%, removing minute particles and airborne bacteria from the
air.
• Electrostatic Filter is used to remove particles from the air by using
highly charged electrodes that ionized the air. Bag Filter is able to
remove dust particles and is thrown away after use.

17. Humidifiers
During winter, the humidity level of the air can be low hence causing
discomfort to the occupants. The humidity of the air is increased by
using the humidifiers. Here are the commonly used humidifiers:
• Spray Type has a header and spray nozzles that spray water with a
pressure of 15 psi or more.
• Steam Pan Type has a pan and a heating coil to heat up the water of
the pan. The evaporation of water caused by the heating will
increase the humidity level of the surrounding air.
• Steam Grid Type has tiny holes on the pipe to distribute the steam
that flows through it.

18. Mixing Box
• This box has air inlets that is attached to the dampers. This is
the place where the outside air and the return air are mixed to
provide the correct proportion of air to be distributed to the
space that is to be conditioned.

19. WORKING
• First, the air returns from the space,
passing back through a duct to the air
handling unit.
• From here, the return air may move into
a mixing box and blend with warmer
outdoor air that is vented in.
(However, not all air handlers use fresh
outdoor air — many simply recirculate the
cool air present in the space.)
• .

20. • The air continues through a rack of air filters and moves across
the evaporator’s cooling coil, which contains cold water or
refrigerant to condition the air.
• Finally, the blower pushes it through the ductwork — and
effectively — throughout the space. Sometimes small heating
element is present just after the evaporator coil to better
control the humidity of the air before it enters the space

21. EFFICENCY
• The capacity of an air handler is most commonly measured by
the amount of air it conditions and distributes. This
measurement is calculated in volumetric units known as CFM
(cubic feet per minute).
• This means if you have a space that is (10ft x 10ft x 10ft =
1000ft³) and a 500 CFM air handler, it would take two minutes
for the old air in the room to be entirely replaced by fresh,
conditioned air from the air handler.

22. REFERENCE
• https://blog.ravti.com/equipment-air-handling-units-ahu-
4900e8b85f83
• https://www.airconditioning-systems.com/air-handling-
unit.html