Post on 15-Jan-2016
PsychrometricChart
Basics
PsychrometricChart
Basics
Basic Concepts
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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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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
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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 Humidity Ratio
Constant Humidity Ratio
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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 Humidity Ratio
Constant Humidity Ratio
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DRY BULB TEMPERATURE - °F
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10% RELATIVE HUMIDITY
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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
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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 Specific Volume
Constant Specific Volume
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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 Web Bulb Temperature
Constant Wet Bulb Temperature
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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 Enthalpy
Constant Enthalpy
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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 Enthalpyand
Constant Web Bulb
Constant Enthalpy and Web Bulb
Typical Chart With Enthalpy LinesTypical Chart With Enthalpy Lines
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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Typical Chart Without Enthalpy LinesTypical Chart Without Enthalpy Lines
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
State Point
State PointState Point
Reading a Psychrometric Chart Practice
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
State PointState Point
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Linric Company Psychrometric Chart, www.linric.com
Constant Dry Bulb Temperature
70Dry Bulb
State Point 70 FState Point 70 F
State Point 60%State Point 60%
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Wet-bulb temperature = ? F
Wet-bulbWet-bulb
Wet-bulbWet-bulb
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Wet-bulb temperature = 61 F
Wet-bulbWet-bulb
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Dew point = ?
Dew PointDew Point
Dew PointDew Point
Dew PointDew Point
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Dew point = 55.5 F
Dew PointDew Point
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Specific volume = ?
Specific VolumeSpecific Volume
Specific VolumeSpecific Volume
Sea Level ChartDry-bulb temperature = 70 F
Relative Humidity = 60%
Specific volume = 13.6 ft3 / lb dry air
Specific VolumeSpecific Volume
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Humidity ratio = ?
Humidity RatioHumidity Ratio
Humidity RatioHumidity Ratio
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Humidity ratio = 0.0094 lb water / lb dry airor
7000 grains = 1 lb water7000 x 0.0094 = 65.8
Humidity RatioHumidity Ratio
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Enthalpy = ?
EnthalpyEnthalpy
EnthalpyEnthalpy
Sea Level ChartDry-bulb temperature = 70 F
Relative humidity = 60%
Enthalpy = 27.0 Btu / lb dry air
EnthalpyEnthalpy
http://linricsoftw.web127.discountasp.net/webpsycalc.aspx
Calculating Air Property ValuesCalculating Air Property Values
Sensible HeatingSensible Heating
Raise Room Temperature 1 degree FConstant Humidity Ratio
27.31 Btu/lb27.06 Btu/lb00.25 Btu/lb
Length (ft) x Width (ft) x Height (ft) = Volume (ft3)
Volume (ft3) / Specific Volume (ft3/lb) = Mass of Air (lb)
Mass of Air (lb) x Enthalpy Change (Btu/lb) = Heat Input (Btu)
Bedroom
12 x 12 x 8 = 1152 ft3
1152 / 14.02 = 82.17 lb
82.17 x 0.25 = 20.54 Btu
Raise Room Temperature 1 degree FConstant Humidity Ratio
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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FurnaceExpected
Result
Heating System Example
supply air from furnace
return air to furnace
1) Return Air 65 F and 60%2) Supply Air 95 F and 22%
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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1) Return 65 F and 60%2) Supply 95 F and 18%
1 2
Measured Values
How is this possible?
supply air from furnacereturn air to furnace
Heating System Example
Mixing Air Streams
ma1
h1
w1
ma2
h2
w2
ma3
h3
w3
Energy Balance
ma1 h1 + ma2 h2 = ma3 h3
Mass Balance
ma1 w1 + ma2 w2 = ma3 w3
By Algebra
h2 – h3 = w2 – w3 = ma1
h3 – h1 w3 – w1 ma2
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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Resulting mixture lies on the line between the two state points.
Mixing Two Equal Air Streams = the center of the line
Mixing Air Streams
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
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1) Return 65 F and 60%2) Supply 95 F and 18%
1 2
Measured Values
How is this possible?
supply air from furnacereturn air to furnace
Heating System Example
Heating System Example
Heating System Example
Cooling
Cooling Systems
Cooling Systems
Total Heat
q = (cfm) (4.5) (∆h)
q = Btuh
h = enthalpy, Btu per lb dry air
Sensible Heat
q = (cfm) (1.08) (∆t)
t = temperature F
Latent Heat
q = (cfm) (4840) (∆w)
w = humidity ratio, lb water per lb dry air
Solving the General Equations for Air Conditioning
Sensible Heat
q (Btuh) = (cfm) (1.08) (∆t)
(∆t) = q (Btuh) (cfm) (1.08)
cfm lower - (∆t) higher
cfm higher - (∆t) lower
q lower - (∆t) lower
q higher - (∆t) higher
Solving the General Equations for Air Conditioning - Sources of Error
12,000 Btuh / ton
400 cfm /ton
Sensible heat fraction = 0.70
Latent heat fraction = 0.30
Standard Operation of an Air Conditioner
Total Heat
q = (cfm) (4.5) (∆h)
12,000 = (400) (4.5) (∆h)
(∆h) = 27.3 Btu / lb dry air
Sensible Heat
q = (cfm) (1.08) (∆t)
12,000 (0.7) = (400) (1.08) (∆t)
(∆t) = 19 F
Latent Heat
q = (cfm) (4840) (∆w)
12,000 (.3) = (400) (4840) (∆w)
(∆w) = 0.002 lb water / lb dry air
Standard Operation of an Air Conditioner
Standard Operation of an Air Conditioner
What if humidity ratio of return air equals the humidity ratio of the
supply air?
Operation of an Air Conditioner
Air Conditioner ExampleAir Conditioner Example
Air Conditioner ExampleAir Conditioner Example
0.002
0.002
Air Conditioner ExampleAir Conditioner Example
Air Conditioner ExampleAir Conditioner Example
0.002
19 F
Evaporative Cooling
Annual Hourly Outside Air Conditions – Lexington KY
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PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
Human Comfort Zones
Annual Hourly Outside Air Conditions – Phoenix, AZ
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PSYCHROMETRIC CHARTSea LevelBAROMETRIC PRESSURE 29.921 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com
Crawl Space Conditions Example
Annual Hourly Outside Air Conditions – Lexington KY
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12.5
13.0
13.5
14.0
14.5 SP
EC
IFIC
VO
LUM
E ft³/lb O
F D
RY
AIR
15.0
HU
MID
ITY
RA
TIO
- G
RA
INS
OF
MO
IST
UR
E P
ER
PO
UN
D O
F D
RY
AIR
PSYCHROMETRIC CHARTLexington, Kentucky USABAROMETRIC PRESSURE 28.874 inches of Mercury
Linric Company Psychrometric Chart, www.linric.com