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INTRODUCTIONHeating, Ventilation and Air Conditioning

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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

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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

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Air Conditioning?Removal of heat

Altering the properties of air

Setting the Human Comfort Zone

Maintain the air quality

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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

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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

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Human comfort

Human comfort zone in Psychometric chart

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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

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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

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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

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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

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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

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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

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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

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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.

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Geothermal Airconditioning

Energy conservation methods

Major power consumers

Improving fan efficiency

Heat recovery systems

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