AUTOMOBILE HVAC SYSTEM

ROLL NO :3448

What is HVAC What is HVAC ??H.V.A.C – Heating, Ventilation and Air Conditioning system

A HVAC System consists of a chain of components designed to heat, ventilate or cool a specific area while maintaining a defined environmental cleanliness level.

Need For HVAC

Easy climate controlIncreasing pollutionOzone layer depletion Greenhouse effect

Refrigeration Cycle

4 1

23

Enthalpy kJ/kg

Vapor compression

cycle

1-2 :Compression

2-3 : Condensation

3-4 : Expansion

4-1 : Evaporation

Construction & Working

WorkingThe system must be capable of keeping a

temperature of 22˚C inside a stationary black

vehicle with four occupants, with an outside

temperature of 40˚C.

Also, the system must be an efficient heating

system, keeping an internal temperature of 15˚C

with an outside temperature of 0˚C.

Sources of heat to systemFaster the car moves, the greater amount of infiltration into the car and

rate of heat transfer is more.

The sun baking down on the blank road will raise the temp. up 50to 60 C

and thus increases the amount of heat transferred into the car through

the floor.

Because of the relatively large glass areas, metal construction and the

flow of air around the moving vehicle(automobile) is very large ,so the air

conditioning capacity is also large in comparison with A. C. installed at

home.

Quantity of fresh air in.

Moisture movement through car.

Activity level, occupancy patterns, and make- up (male, female, child) of

people.

Quantity of heat directly rejected by sun on car.

Selection Basis• Scroll Compressors –

Compact design and High Volumetric Efficiency ( around 98% ).

• Refrigerant R134a –Minimized environmental impact.

• Plate-Fin Heat Exchanger-Compact size, Higher heat transfer

capability.• Simple design incorporated to minimize cost.

Compressor•Heart of the system, belt driven pump that fastened to engine.•Responsible for compressing and transferring refrigerant.

•Two interleaved scrolls with involute geometry.•One scroll fixed while the other orbits eccentrically to compress fluid

Advantage:

•Very high volumetric efficiency (almost 98%)

•Lesser Noise and lighter compared to rotary

compressor.

Condenser•Responsible for heat dissipation

•The condenser is designed to radiate heat.

•Located in front of the radiator

•Require good air flow when system is in operation

•Plate fin type heat exchanger with micro channels used.

•Very compact and better heat transfer capability.

•Hot compressed refrigerant vapour cools at constant pressure to liquid.

Overall Heat Transfer Coefficient = 92 W/m2K

Area = 6.87 m2

Accumulator

•Depending on the vehicle, the A/C system will either have a receiver dryer or an accumulator.

•Components contain a desiccant, chemical that attracts moisture.

•Prevents formation of corrosive acids on mixture of water and acid.

•Also act as temporary storage for refrigerant to prevent starving of evaporator

Evaporator•Heat absorption component.

•Used remove heat from the inside of vehicle.

•Secondary benefit - dehumidification.

•Unconditioned air passes through a filter before entering the evaporator.

•Plate-fin evaporator with micro channels used.

AdvantagesTravel with comfort for a long distance, In

any type of atmospheric conditions without tired.

Fuel Efficiency.

Reduction Greenhouse Gas Emission.

Reduction in ozone layer depletion.

Environment Friendly.

Disadvantages

Engine speed, average and power will reduce

Initial cost of unit

Complicated system

Future Aspects

Now a days automobile HVAC system are under

development and have used atmospheric carbon dioxide

( CO2 ) as a refrigerant which is compatible to R134a in

performances and efficiency. This system also has advantage

to reduce carbon emission which in turn results into reduce

green house effect.

Also in newer cars a “computer control system” is used to

control multi-zone HVAC system which can give comfort to a

individual occupant as per the occupant required.

Thank You !