BASIC MECHANICAL ENGINEERING. REFRIGERATION AND AIR CONDITIONING

BASIC MECHANICAL BASIC MECHANICAL ENGINEERINGENGINEERING

REFRIGERATION REFRIGERATION AND AIR AND AIR

CONDITIONINGCONDITIONING

Vapour Compression Vapour Compression Refrigeration SystemRefrigeration System

• Basic ComponentsBasic Components

– CompressorCompressor

– CondenserCondenser

– Expansion ValveExpansion Valve

– EvaporatorEvaporator

RefrigeratorRefrigerator

ProcessesProcesses

• 1. Low temp., Low pr., Vapour enters 1. Low temp., Low pr., Vapour enters

CompressorCompressor

• 2. High temp., High Pr., Vapour enters 2. High temp., High Pr., Vapour enters

CondenserCondenser

• 4. High pr. Saturated Liquid enters 4. High pr. Saturated Liquid enters

Expansion Valve (Throttle Valve)Expansion Valve (Throttle Valve)

• 5. Low temp., wet Vapour enters 5. Low temp., wet Vapour enters

EvaporatorEvaporator

Vapour Compression Vapour Compression Refrigeration SystemRefrigeration System

Vapour Absorption Vapour Absorption Refrigeration SystemRefrigeration System

• Difference in method of converting the Difference in method of converting the

refrigerant vapour back into liquid. refrigerant vapour back into liquid.

• Compressor replaced by combination of Compressor replaced by combination of

Absorber and Generator.Absorber and Generator.

• Vapour from evaporator is dissolved in Vapour from evaporator is dissolved in

the cold water in the absorber which thus the cold water in the absorber which thus

turns into a warm strong solution.turns into a warm strong solution.

• The strong solution is heated in generator The strong solution is heated in generator

to separate refrigerant vapour.to separate refrigerant vapour.

• Remaining weak solution is sent back to Remaining weak solution is sent back to

absorber to be used as solventabsorber to be used as solvent

Vapour Absorption Vapour Absorption Refrigeration SystemRefrigeration System

Comparison – Advantages of Comparison – Advantages of Absorption SystemAbsorption System

• Heat is used as major source of Heat is used as major source of

energyenergy

• No moving partsNo moving parts

• Performance is not affected by load Performance is not affected by load

on compressionon compression

• No danger of liquid traces in suction No danger of liquid traces in suction

lineline

• Works on low evaporator pressureWorks on low evaporator pressure

• Automatic operation is easyAutomatic operation is easy

COPCOP

Coefficient of Performance, COP Coefficient of Performance, COP

= Heat extracted / Work by Compressor= Heat extracted / Work by Compressor

Unit & PropertiesUnit & Properties

The rate of heat absorbed by the system The rate of heat absorbed by the system

from the body to be cooled, equivalent from the body to be cooled, equivalent

to the latent heat of fusion of 1 ton of to the latent heat of fusion of 1 ton of

ice from and at 0ice from and at 000C in 24 hours is called C in 24 hours is called

one ton of refrigeration.one ton of refrigeration.

1 ton of refrigeration = 3,5167kJ of heat 1 ton of refrigeration = 3,5167kJ of heat

removal / secondremoval / second

PropertiesProperties

Condensing & evaporation pressures Condensing & evaporation pressures

higher than atmospheric pr., critical higher than atmospheric pr., critical

temp high, low freezing temp., low temp high, low freezing temp., low

sp.heat, high L.H., low sp.volume, low sp.heat, high L.H., low sp.volume, low

viscosity, high thermal conductivity, viscosity, high thermal conductivity,

stability, inflammability….stability, inflammability….

Air ConditioningAir Conditioning

Air ConditioningAir Conditioning

• TerminologyTerminology

– Dry air, Moist airDry air, Moist air

– Specific humiditySpecific humidity

– Relative humidityRelative humidity

– Dry bulb temperatureDry bulb temperature

– Wet bulb temperatureWet bulb temperature

– Dew point temperatureDew point temperature

– Sensible heatSensible heat

– Total heatTotal heat

Physical ProcessesPhysical Processes

• Air PurificationAir Purification

– Air filtration, Air sterilization, Air Air filtration, Air sterilization, Air

ionisation, Odour suppressionionisation, Odour suppression

• Temperature ControlTemperature Control

– Indirect, DirectIndirect, Direct

• Humidity ControlHumidity Control

– Dehumidification, HumidificationDehumidification, Humidification

• Air DistributionAir Distribution

Comfort Air conditioningComfort Air conditioning

• Combination of Dry bulb temp., Combination of Dry bulb temp.,

Relative humidity and Air velocityRelative humidity and Air velocity

• Effective TemperatureEffective Temperature

It is the dbt of a sample of It is the dbt of a sample of

saturated air which will give a saturated air which will give a

particular feeling of comfort to particular feeling of comfort to

the same percentage of people as the same percentage of people as

any other combination of dbt and any other combination of dbt and

RH. RH.

Window Air conditioningWindow Air conditioning

Winter Air conditioningWinter Air conditioning

Summer Air conditioningSummer Air conditioning

Viscous FilterViscous Filter

Wet FilterWet Filter

Air Cooling - IndirectAir Cooling - Indirect

Air Cooling - DirectAir Cooling - Direct

DehumidifierDehumidifier

Atomisation HumidifierAtomisation Humidifier

Forced Evaporation Forced Evaporation HumidifierHumidifier

Air DistributionAir Distribution

Air DistributionAir Distribution