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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
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
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
DRY BULB TEMPERATURE - °F
10
20
30
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
Constant Humidity Ratio
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
DRY BULB TEMPERATURE - °F
10
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
Constant Humidity Ratio
Constant Humidity Ratio
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
DRY BULB TEMPERATURE - °F
10
20
30
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50
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90
100
110
120
130
140
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200
210
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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
DRY BULB TEMPERATURE - °F
10
20
30
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60
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90
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110
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130
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12.5
13.0
13.5
14.0
14.5 S
PE
CIF
IC V
OLU
ME
ft³/lb O
F D
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AIR
15.0
15.5
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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
DRY BULB TEMPERATURE - °F
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30
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120
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210
0 5
510
1015
1520
2025
2530
3035
3540
4045
45 50
50 55
5560
6065
65
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80
80
85 WET BULB TEMPERATURE - °F
85
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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
DRY BULB TEMPERATURE - °F
10
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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
DRY BULB TEMPERATURE - °F
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EN
TH
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PY
- B
TU
PE
R P
OU
ND
OF
DR
Y A
IR
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EN
TH
ALP
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TU
PE
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OF D
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SA
TU
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N T
EM
PE
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TU
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- °
F
0 5
510
1015
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2025
2530
3035
3540
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45 50
50 55
5560
6065
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85 WET BULB TEM
PERATURE - °F
85
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
12.5
13.0
13.5
14.0
14.5
SP
EC
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VO
LU
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ft³/lb O
F D
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AIR
15.0
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
.1
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1.0
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1.3
VA
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UR
E -
IN
CH
ES
OF
ME
RC
UR
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-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
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