AIR CONDITIONING PSYCHROMETRYferdousalam.weebly.com/uploads/6/8/.../air-conditioning___psychrome… · CENTRALISED AIR-CONDITIONING SYSTEM Used for cooling big buildings, offices,

AIR-CONDITIONING &

PSYCHROMETRY

Md. Ferdous Alam, Lecturer, MEE, SUST

HELLO CLASS

Nice weather!

CLASSIFICATION OF REFRIGERATION

APPLICATION

Domestic refrigeration

Commercial refrigeration

Industrial refrigeration

Marine & transportation refrigeration

Comfort air-conditioning

Industrial air-conditioning

DEFINITION

A system for controlling the humidity ,ventilation

and temperature in a building or vehicle typically to

maintain comfortable conditions.

MAJOR PARTS OF THE AC

Evaporator

Compressor

Condenser

Expansion Valve

WINDOW AC

TYPES OF AC

Window AC

Split AC

Central AC plant

Packaged AC

CENTRALISED AIR-CONDITIONING SYSTEM

Used for cooling big buildings, offices, hotels,

movie theatre etc.

It consists of a huge compressor that has the

capacity to produce hundred of tons of air

conditioning.

PSYCHROMETRY

Psychrometry is that branch of engineering

science, which deals with the study of moist air

i.e. dry air mixed with water vapour or humidity.

It is also includes the study of behavior of dry air

and water vapour mixture under various sets of

conditions.

PSYCHROMETRIC TERMS

Dry air: The pure dry air is a mixture of a

number of gases such as nitrogen, oxygen, carbon

dioxide, hydrogen, argon, helium etc. but the

nitrogen and oxygen have the major portion of

the combination.

Moist air: it is a mixture of dry air and water

vapour. The amount of water vapour depends

upon the absolute pressure and temperature of

the mixture.

Saturated air: It is a mixture of dry air and water

vapour. When the air has diffused the maximum

amount of water vapour into it

Degree of saturation: It is the ratio of actual

mass of the water vapour in unit mass of dry air

to the mass of water vapour in the same mass of

dry air when it is saturated at the same

temperature.

Humidity: It is the mass of water vapour present

in 1 kg of dry air, and generally is expressed in

terms of gram per kg of dry air (g/kg dry air). It is

also called specific humidity or humidity ratio.

Absolute humidity: It is the mass of water vapour

present in 1 m3 of dry air, and is generally

expressed in terms of gram per cubic-meter of dry

air (g/m3 of dry air). It is also expressed in terms

of grains per cubic meter of dry air.

Relative humidity: It is the ratio of actual mass

of the water vapour in a given volume of moist

air to the mass of water vapour in the same

volume of saturated air at the same temperature

and pressure. It is briefly written as RH.

Dry bulb temperature:

Wet bulb temperature:

Dew point temperature: It is the temperature of

air recorded by thermometer, when the moisture

(water vapour) present in it begins to condense.

PSYCHROMETRY

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120

DRY BULB TEMPERATURE - °F

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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury

Linric Company Psychrometric Chart, www.linric.com

Staturation Line

Saturation Line

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Constant Dry Bulb Temperature

Constant Dry Bulb Temperature

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120


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Constant Humidity Ratio


0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120


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Dew point Temp

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120


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10% RELATIVE HUMIDITY

20%

30%

40%

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60%

70%

80%

90%

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Constant Relative Humidity

Constant Relative Humidity

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120


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12.5

13.0

13.5

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14.5 S

PE

CIF

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OLU

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ft³/lb O

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15.0

15.5

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Constant Specific Volume

Constant Specific Volume

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120


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0 5

510

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85 WET BULB TEMPERATURE - °F

85

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Constant Web Bulb Temperature

Constant Wet Bulb Temperature

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120


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Constant Enthalpy

Constant Enthalpy

TYPICAL CHART WITH ENTHALPY LINES

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120


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EN

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PY

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TU

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Y A

IR

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- °

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85 WET BULB TEM

PERATURE - °F

85

10% RELATIVE HUMIDITY

20%

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90%

12.5

13.0

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SP

EC

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ft³/lb O

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15.0

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.1

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VA

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IN

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OF

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RC

UR

Y

-20

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DE

W P

OIN

T -

°F

READ YOURSELF

Dry-bulb temperature = 70 F

Relative humidity = 60%

Sensible Cooling

SENSIBLE HEATING

NEXT CLASS & LAST CLASS FOR THIS TERM

Introduction to robotics

Thank you

AIR CONDITIONING PSYCHROMETRYferdousalam.weebly.com/uploads/6/8/.../air-conditioning___psychrome… · CENTRALISED AIR-CONDITIONING SYSTEM Used for cooling big buildings, offices,

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