Practical Psychrometrics

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2010 HVACR/Plumbing
Instructors Workshop
Practical Psychrometrics
Presented by Richard Wirtz,
Associate Director of Education
Heating, Air conditioning & Refrigeration
Distributors International
(HARDI)
Thank you for being here today.
For Everyone’s Consideration
What seems to be the problem?
Who teaches psychrometrics on a normal basis?
Why is this area not taught more?
Confusion?
Misunderstanding?
Intimidation?
Let’s eliminate the confusion –
Right Now.
Air properties:
Composition
Weight
Wet or Dry
Specific Heat
Pressure
Volume
The Chart
Willis Carrier December 3, 1911
“Rational Psychrometric Formulae”
ASME
Psychro = cold
Metrics = measure of
Different temperature ranges
Different elevations
“Points on a Map”
North
H
West
East
South
Points on the “Map”
Dry Bulb
Wet Bulb
Enthalpy
Dew Point
Relative Humidity
Specific Volume
Specific Density
Specific Humidity (Grains of Moisture)
Sensible Heat Dot
Sensible Heat Factor
Where’s Waldo???
North
West
East
South
Process line shows grains
of moisture change as well
as temperature change.
Heating &
Humidification
Sensible
Heating Only
Cooling &
Dehumidification
Dry Bulb
Enthalpy
Wet
Bulb
Grains of
Moisture
Dew
Point
Relative
Humidity
Specific
Volume
Sensible heating only
No change in the dew
point or the grains of
moisture.
Let’s Do Some Quick Math
Qs = Quantity of Sensible Heat
64,000 Net Output = 1.08 x CFM x ▲T
64,000 = 1.08 x CFM x 40
1481 CFM
64,000 = 1.08 x 1,481 x 40
Continuing
QL = Quantity of Latent Heat
QL = .68 x CFM x ▲Grains of Moisture
QL = .68 x CFM x 0
QL = 0
QT = 4.5 x CFM x ▲Enthalpy
QT = 4.5 x CFM x (31.62 – 21.79)
QT = 4.5 x 1,481 x 9.83
QT = 65,911
64,000/65,512 = 97.69% or 2.31% difference
Let’s Do Some More Quick Math
Qs = Quantity of Sensible Heat
23,680 = 1.08 x CFM x ▲T
23,680 = 1.08 x 1,096 x 20
1.08 x 20 = 21.6
23,680/21.6 = 1,096 CFM
Continuing
QL = Quantity of Latent Heat
QL = .68 x CFM x ▲Grains of Moisture
QL = .68 x 1,096 x 8
QL = 5,962 Btu
QT = 4.5 x CFM x ▲Enthalpy
QT = 4.5 x 1,096 x (26.80 – 20.58)
QT = 4.5 x 1,096 x 6.22
QT = 30,677
29,600/30,677 = 96.49% or 3.51% difference
“Created Equal”
does not mean
“Equal Outcome”
Additional Information
Free software @ handsdownsoftware.com or
from a manufacturer or wholesaler or someone
here. Just ask someone.
Carrier SST-03
“Air Properties and Measurement”
Questions??
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