Date post: | 10-Jan-2017 |
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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