HEAT VENTILATION AND AIR

CONDITIONING (HVAC)

CONTENT

1. DEFINITION2. BASIC OPERATING CYCLE3. CLASSIFICATION OF AC SYSTEM4. COMPONENTS AND FUNCTIONS OF AHU5. DEHUMIDIFIER AND HUMIDIFICATION6. CHARACTERSTICS OF AIR HANDLING SYSTEM7. PRESSEURE CASCADES8. DUCTING9. HVAC VALIDATION10. MAINTAINENCE SPARES AND ITS APPR. COSTS

DEFINITION

An Air Handling Unit (AHU), or Air Handler, is a central air conditioner station that handles the air

that, usually, will be supplied into the buildings by the ventilation ductwork.

Handling the air means that the air will be delivered into the building spaces with thermo-

hygrometric and IAQ (Indoor Air Quality) treatment. The accuracy of the treatment will depend

from the specificity of each project (offices, schools, swimming-pools, laboratories, factories with

industrial processes, etc). This means, the Air Handling Unit treat the air by filtering, cooling and/or

heating, humidifying and/or dehumidifying.

There are several types of Air Handling Units: Compact, Modular, Residential, DX integrated, Low

Profile (ceiling), Packaged, Rooftop mounted (typically on the roofs of buildings, with special

weather protection), etc.

1 TR is amount of heat to be extracted from the atmosphere for melting 1 metric ton of ice in 24

hrs.

1 TR = 12000 BTU/Hr. or 3025 kcal/Hr.

BASIC OPERATING CYCLE

WORKING PRINCIPLE

CLASSIFICATION OF AC SYSTEM

TYPES OF AIR HANDLING UNITS (AHU)

a) SINGLE SKINNED AHU

b) DOUBLE SKINNED AHU

II) DEPENDING ON SPACE AVAILABILITY FOR AHU , THE AHUs ARE CLASSIFIED AS UNDER:-

a) HORIZONTAL TYPE FLOOR MOUNTED UNIT

b) VERTICAL TYPE FLOOR MOUNTED UNIT

c) CEILING SUSPENDED UNIT.

III) TYPE OF AHU DEPENDING UPON LOCATION OF FAN:-

a) DRAW THROUGH TYPE:- FAN IS LOCATED AFTER COOLING COIL

b) BLOW THROUGH TYPE:- FAN IS LOCATED BEFORE COOLING COIL

MOST COMMON CONFIGURATIONS

Inline - Supply 100% Outdoor >Double-Deck - Mixed Air

Inline - Supply Mixed Air

>Side by Side - 100% Outdoor Air

Inline - Double Flux (with Mixing Air)

Double-Deck - 100% Outdoor Air >Side by Side - Mixed Air

COMPONENTS AND FUNCTIONS OF AHU

FilterSilencer

Terminal filter

Weather louvre or Filter Control damper

FanFlow rate controller

Humidifier

Heating coil

Cooling coil with droplet separator

Production Room

Overview components

+Prefilter

COMPONENTS OF AHU

Fans (Plug Fans, Double Inlet, Single Inlet, Axial, Centrifugal flows etc)

Filters (Plate Filters, Bag Filters, Compact Filters, HEPA Filters, ULPA Filters, Carbon Filters)

Cooling/Heating Coils (water/steam/Direct Expansion DX/electric/gas fired)

Heat recovery systems (cross flow plate heat exchangers, heat wheel/rotating heat exchangers, run around coils and heat pipes, etc)

Humidifiers (Adiabatic/Evaporative Pad,

non-pressurized Steam, pressurized steam)

Dehumidifiers (DX coil, desiccant rotor)

AHU Chilled water Manifold

Sound attenuators

Mist/Droplet eliminators

Dampers & Plenum

FUNCTIONS OF AHU

Cooling unit /dehumidifier : To cool the air to the required temperature or to remove

moisture from the air

Heating unit To heat the air to the proper temperature

Humidifier :To bring the air to the proper humidity, if too low

Filters : To eliminate particles of pre-determined dimensions and/or micro-organisms

Ducts : To transport the air

Silencer : To reduce noise caused by air circulation

Weather louvre or Filter : To prevent insects, leaves, dirt and rain from entering

Flow rate controller : Automated adjustment of volume of air (night and day, pressure

control)

Control damper : Fixed adjustment of volume of air

FILTER CLASSES

Dust filters

Standard Aerosol

FineCoarse ULPAHEPA

10 µ m > Dp > 1 µ mDp > 10 µ m Dp < 1 µ m

F5 - F9G1 - G4 U 14- 17H 11 - 13

EN 1822 StandardEN 779 Standard

Primary panel filter

Secondary filter

HEPA or tertiaary filter

FILTERS

DEHUMIDIFIER AND HUMIDIFICATION

Humid room air

Air heater

Regeneration air

Humid room airAdsorber wheel

• Dehumidification is the removal of water vapor from air, definition, and sorption dehumidification equipment

• Dehumidifiers remove excess humidity by drawing moist room air over cold refrigerated coils. The moisture in the air condenses into droplets as it passes over the cold surfaces in the dehumidifier and into a container.

Uni-directional / laminardisplacement of dirty air

Turbulent dilution of dirty air

0,30 m/s

Air flow patterns

CHARACTERSTICS OF AIR HANDLING SYSTEM

CHARACTERSTICS OF AIR HANDLING SYSTEM

PrefilterAir flow patternsAHU

Main filter

Uni-directional TurbulentTurbulent

1 2 3

Positioning of filters

Filter in terminal position AHU mounted final filter

Production Room

+

Production Room

HEPA Filter

HEPA Filter

CHARACTERSTICS OF AIR HANDLING SYSTEM

Regulation of Room Pressure – Pressure Differentials Concept

Room pressure gauges

Room pressure indication panel

PRESSEURE CASCADES

Pressure cascade injectableProtection from micro-organisms and particles

N ote : D irection of door opening relative to room pressure

15 Pa

0 PaA irLock

30 Pa PassageD

C

A

B

D LF

A ir LockA ir Lock45 Pa

Room 3 Room 2 Room 1

45 Pa60 Pa30 Pa

PRESSEURE CASCADES

N ote : D irection of door opening relative to room pressure

15 Pa

15 Pa15 Pa

E30 PaPassage

0 Pa

A irLock

Room 3 Room 2 Room 115 Pa

A ir LockA ir Lock

Pressure cascade solidsProtection from cross-contamination

DUCTING

A Duct can be described as a device used to provide an isolation path to carry a medium from one place to other place without bringing the product in contact with the atmosphere before the delivery point.

DUCTING

Don’t Do’sNo Bracing and width of the duct is more than750mm.

Breathing of the Duct - Results in Noise No Breathing Noise

Bracing should be done all around the duct from outside when width of the duct is more than 750mmto provide strength to the duct.

4 Feet 4 Feet 8 Feet

MS Bracing

T

A

B

W id t h o f th e D u ct ( mm ) A (mm) B (mm) T (mm)

From 700 to 1200 25 25 3

Above 1200 40 40 3

DUCTING

TYPES OF PRESSURES IN A DUCT

• Total Pressure• Static Pressure• Velocity Pressure

TOTAL PRESSURE = STATIC PRESSURE + VELOCITY PRESSURE.

ASPECT RATIO OF DUCTING

Aspect Ratio = Long Side/Short Side = Width of the duct / Height of the duct Best Aspect Ratio is 1 : 1

Maximum permissible aspect ratio is 4 : 1 Effects of Aspect Ratio

ADVANTAGES AND DISADVANTAGES OF VARIOUS DUCTS

COMPONENTS OF DUCTING

HVAC VALIDATION

DOP/PAO (Poly Alpha Oli film)/Filter integrity test Air balancing Pressure balancing Particle count Air flow pattern Recovery test Fumigation Documents handover

Instrument used for air balancing : Supply diffusers.

Instrument used velocity measurement: Digital anemometer

Instrument used for pressure balancing: magnehulic gauge.

Instrument used for particle count: particle counter

Instrument used for Air flow pattern: Fogger m/c , Video

Instrument used for PAO test : Aerosol photometer.

AHU’S ANUALLY SPARES APPR. COSTSLNO COMPONENTS REQD. QTY. UOM UNIT COST TOTAL COST

(LAKHS) COST/ YEAR

1 TUBULER HEATERS 20 Set 10000.00 2.00 2.002 THERMOSTAT 10 NO. 2000.00 0.20 0.103 COOLING COIL 4 NO. 30000.00 1.204 HOT WATER COIL 2 NO. 15000.00 0.305 PRESSURE GUAGES 6 NO. 1500.00 0.096 MAGNELIC GUAGES 4 NO. 6000.00 0.247 TEMP. GUAGES 6 NO. 1500.00 0.098 AHU HARDWARE 1 Set 20000.00 0.20 0.209 CONTACTORS 6 NO. 1500.00 0.09

10 OVER LOAD RELAY 6 NO. 1000.00 0.0611 PUSH BOTTONS 15 NO. 50.00 0.0112 MOTOR 4 NO. 25000.00 1.0013 MPCB 6 NO. 3500.00 0.2114 COIL CLEANING CHEMICAL 200 Ltr. 150.00 0.30 0.3015 3 WAY VALVE WITH ACTUATOR 2 NO. 25000.00 0.5016 BALL VALVES 5 NO. 2500.00 0.1317 SYPHON TUBE 6 NO. 300.00 0.0218 DRAIN VLAVES 10 NO. 300.00 0.0319 TEMP. & RH SENSOR 3 NO. 3000.00 0.0920 TEMP. CONTROLLER 3 NO. 3000.00 0.0921 HYGROMETER 1 NO. 40000.00 0.40

7.24 2.60