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Introduction to HVAC by Ajeen Surendran
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1
INTRODUCTIONHeating, Ventilation and Air Conditioning
Engineer’s Desk
ENGINEERING CONSULTANCY & MEP Training
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HVAC-What is it?Indoor & environmental
comfort.Cooling during SummerHeating during winterHeat transfer always
from hot cold
Engineer’s Desk
3
History
• Ancient Egyptian Houses
• Air shaft with water Spray• Reduce room temperature and humidity
• Aqueducts in Rome
• Water Channel cooled by air passing through•Piping through the walls of houses with this cold water
• Willis Haviland Carrier The inventor of modern air conditioners in 1911•The coolest invention
Engineer’s Desk
4
Air Conditioning?Removal of heat
Altering the properties of air
Setting the Human Comfort Zone
Maintain the air quality
Engineer’s Desk
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Removal of heat or Heat transferDifferent modes of heat transferConduction
•Direct contact with each other•Better the conductor, Faster the heat transfer•When molecules gain maximum energy the remaining is transferred to the nearby molecule
Convection•Transfer of heat from hot to cold places•Warmer area of liquid or gas will rise higher and is replaced by cooler particles• ex. Earths atmosphere, boiling water
Radiation•No contact with the heat source and heated object•Thermal radiation or infrared radiation•Electromagnetic radiation•Ex. Sun heating the earth, light bulb filaments
Engineer’s Desk
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Air properties
AIR
Temperature
Density
Specific heat capacity
Thermal conductivity
For HVAC Design
• Dry Bulb temperature (DBT)
• Wet bulb Temperature(WBT)
• Relative humidity (RH%)• Enthalpy
Psychometric chart
Engineer’s Desk
7
Human comfort
Human comfort zone in Psychometric chart
Engineer’s Desk
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Basics of Air conditionersHigh Pr & Temp
CompressorLowest Pr & temp
Condensor coil
High Pr & Temp High Pr & low Temp
Expansion valveHigh Pr & Low Temp
Low Pr & low Temp
Evaporator coilLow Pr & Low Temp
Lowest Pr & Temp
Engineer’s Desk
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Refrigerants• Fluorocarbons-CFC, HCFC, HFC• Excellent thermodynamic
properties• Liquid substance with Low Boiling
point• Non corrosive to mechanical
Machines• Non flammable and non toxic• Carries the heat from the
conditioned space to outdoor
Most commonly used Refrigerants
Type ASHRAE No Molecular Form
CFC R-12 CCL2F2HCFC R-22 CHClFHFC R-134a C2H2F4HFC R-143a C2H3F3HCFC R-401A 53±2% CHClF2 ·13+.5,-
1.5% C2H4F2 ·34±1% C2HF4Cl
HFC R-410A 50+.5,–1.5% CH2F2 ·50+1.5,–.5% C2HF5
Engineer’s Desk
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Downsides of refrigerantsInert nature of refrigerants leads to stability
in the atmosphere.Ozone Layer depletionR-12 being banned from most countriesNew refrigeration developments – R-401A, R-
410A etc
Engineer’s Desk
11
Types of ACsWindow or through wall
Split system
Central Air conditioning
• Fixed in a window or wall opening
• The whole cycle under one shell
Unitary
Packaged ductless
• Indoor(Fan & evaporator coil)
• Outdoor(Compressor & Condenser)
Wall mounted
Ducted split
VRF
Air cooled chillers
Water cooled chillers
District cooling
Engineer’s Desk
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Ventilation Systems
BUT WHY?• Remove unpleasant smell• Gets fresh air from outside to
maintain the air quality• Maintains Air quality
Process of changing or replacing the air
2 Different methods
• Mechanical Ventilation
• Natural Ventilation
Engineer’s Desk
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Ventilation System
Exhaust
Fresh Air
Extracts unpleasant smell from Kitchen, Bathroom, etc.
Using an Extract fan
Extracts Fresh air from outside
Fed to the FAHU to retreat it
Heat recovery unit to increase the efficiency
Engineer’s Desk
14
Heat Pumps
• Against the Laws of Thermodynamics
• Flow of heat from cold to hot
• Reverse process of cooling
• Mostly used for warming up the space
• Popular in cold countries
Engineer’s Desk
15
Latest Technologies & Energy Conservation methodsDistrict cooling
Radiant cooling
• Temperature controlled surface
• Heat transfer through radiation
• Can be installed on floor or ceiling
• Reduces space consumptions for ducts, Indoors etc.
Engineer’s Desk
16
Geothermal Airconditioning
Energy conservation methods
Major power consumers
Improving fan efficiency
Heat recovery systems
Engineer’s Desk
17
Engineer’s Desk