W v ] }v}v^ HVAC: Heating Ventilation Air Conditioninghsciet.weebly.com/uploads/2/9/8/4/2984625/lecture_3_hvac.pdf · 2018. 10. 12. · HVAC Heating, Ventilation and Air Conditioning

Presentation on HVAC: Heating

Ventilation Air Conditioning

CHITKARA UNIVERSITY CHITKARA SCHOOL OF

MECHANICAL ENGINEERING

;HARVINDER SINGH

HVAC

• Heating, Ventilation and Air

Conditioning

• Provides comfort for people

• Allows humans to exist under

adverse conditions.

Load Calculations

• Heating and Cooling

• Accuracy important!

• Design conditions

• Building shell load

• Internal load

• Ventilation load

• Infiltration

• Occupancy schedules

Refrigeration

• It is defined as the process of providing and

maintaining a temperature well below that of

surrounding atmosphere.

• In other words refrigeration is the process of

cooling substance.

Air-Conditioning Principles

• Must be a transfer

of heat for

refrigerant to

change state

– Liquid absorbs

heat as changes to

gas

– Vapor releases

heat as changes to

liquid

Heat Transfer

• Heat flows to anything with less heat

– Convection

• Heat rises

• Heat always flows from hot to cold

– Radiation

• Example: heat from the sun

– Evaporation

• Moisture absorbs heat as it is vaporized

• Example: perspiration

Refrigerators and heat pumps

• If the main purpose of the machine is to

cool some object the machine is named as

refrigerator

• If the main purpose of machine to heat a

medium warmer than the surroundings,

the machine is termed as heat pump.

Refrigerator and Heat pump

QR

Work Input

QR

Work Input

Heat

Pump

Warm Space

Cold Space

Refrig

erator

Types of Refrigerators

• Ice Refrigerators : Ice is kept in the cabinet of

refrigerators and this acts as the refrigerating

means.

• Air Refrigerators : Air is used as working agent

in these types of refrigerators.

• Vapour Refrigerators: The working agents

employed in this type of refrigerators are

ammonia, CO2, SO2, freons etc.,

Applications of Refrigeration • In chemical industries, for separating and liquefying the

gases.

• In manufacturing and storing ice.

• For the preservation of perishable food items in cold

storages.

• For cooling water.

• For controlling humidity of air manufacture and heat

treatment of steels.

• For the preservation of tablets and medicines in

pharmaceutical industries.

• For the preservation of blood tissues etc.,

• For comfort air conditioning the hospitals, theatres, etc.,

Vapour Compression Refrigeration

System

Vapour Compression Refrigeration System -

Construction

• This system consists of a compressor, condenser, a receiver tank, an expansion valve and an evaporator.

• Compressor : Reciprocating

compressors generally used.

For very big plants centrifugal

compressors directly coupled

with high speed rotating

engines (gas turbine) are used.

Vapour Compression Refrigeration System -

Construction

Compressor: For very big plants

Centrifugal compressors

directly coupled with high

speed rotating engines

(gas turbine) are used

Vapour Compression Refrigeration System -

Construction

• Condenser : It is a coil of tubes made of copper.

• Receiver tank: It is the reservoir of liquid refrigerant.

• Expansion Valve: This is a throttle valve. High pressure refrigerant is made to flow at a controlled rate through this valve.

• Evaporator : It is the actual cooler and kept in the space to be cooled. The evaporator is a coil of tubes made of copper

EVAPORATOR TUBING

Vapour Compression Refrigeration System -

Working

Working :

1. The low pressure refrigerant vapour coming out of the

evaporator flows into the compressor.

2. The compressor is driven by a prime mover.

3. In the compressor the refrigerant vapour is compressed.

4. The high pressure refrigerant vapour from the compressor is

then passed through the condenser.

5. The refrigerant gives out the heat it had taken in the

evaporator

Vapour Compression Refrigeration System -

Working

Working :

6. The heat equivalent of work done on it (w) on the compressor.

7. This heat is carried by condenser medium which may be air or

water.

8. The high pressure liquid refrigerant then enters the expansion

valve.

9. This valve allows the high pressure liquid refrigerant to flow at a

controlled rate into the evaporator.

10. While passing though this valve the liquid partially

evaporates.

Vapour Compression Refrigeration System -

Working

Working :

11.Most of the refrigerant is vapourised only in the evaporator, at a low pressure.

12. In the evaporator the liquid refrigerant absorbs its latent heat of vapourisation from the material which is to be cooled.

13. Thus the refrigerating effect is obtained.

14. Then the low pressure refrigerant enters the compressor and the cycle is repeated.

Layout of Domestic Refrigerator

Window Type Air Conditioner

Window Type Air Conditioner - Construction

• This is also called room air conditioner.

• This unit consists of the following.

1. A cooling system to cool and dehumidify the air involves a condenser, a compressor and a refrigerant coil.

2. A filter to any impurities in the air. The filter is made of mesh, glass wool or fibre.

3. A fan and adjustable grills to circulate the air.

4. Controls to regulate the equipment operation.

Humidity

• Low humidity

– Permits heat to be taken away from the human

body

• Evaporation and perspiration

• High humidity

– Makes evaporation difficult

• People feel as comfortable at 79°F with 30% humidity

as at 72°F at 90% humidity

AIR FILTERS

• Air filters

– Air cleaning and filtration

– Operating performance:

• Efficiency or effectiveness of dust removal

• Dust holding capacity

• Service life

– Types: low-, medium-, and high-efficiency filters

CLEAN ROOM CLASSIFICATION (ISO 14644)

THANKS