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A Trane Air Conditioning Clinic
Psychrometry
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Psychrometry
period one
The Psychrometric Chart
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
PsychrometricChart
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Properties Of Air
Dry-bulb temperature Wet-bulb temperature Dew-point temperature Relative humidity Humidity ratio
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Dry-Bulb Thermometer
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Wet-Bulb Thermometer
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Condensation Occurs At Dew PointCondensation Occurs At Dew Point
Air Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Fog Occurs When Air Is Saturated
Air Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Relative Humidity…describes the degree of saturation
RelativeHumidity
Amount of moisture that a given
amount of air is holding=
Amount of moisture that a given
amount of air can hold
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
50% 100%(saturated)
Relative Humidity…compares moisture content to saturation
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Humidity Ratio…compares water vapor to dry air, by weight
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Knowing Two Properties…lets you determine the remaining three
Dry-bulb temperature Wet-bulb temperature Dew-point temperature Relative humidity Humidity ratio
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
EXAMPLESummer Design Conditions
95°F DB (dry bulb) 78°F WB (wet bulb)
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
“X Marks The Spot”…
95°F95°F
78°F78°F
50%
50%
40%
40%
72°F72°F
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
25°F
30°F
35°F
40°F
45°F
50°F
55°F
19.14
24.19
29.94
36.51
44.34
53.63
64.63
60°F
65°F
70°F
75°F
80°F
85°F
90°F
77.61
92.89
110.82
131.83
156.38
185.03
218.42
DBTemp.
HumidityRatio
DBTemp.
HumidityRatio
Saturated Air…grains of moisture per pound of dry air
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
Plotting Saturation Points218.42
185.03
156.38
131.83
110.82
92.89
77.61
64.63
53.6344.34
36.5129.94
24.1919.14
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
Saturation Curve
100% Relative Humidity Curve
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
relationship between…
Dry Bulb, Wet Bulb And Dew Point
60°FDew Point
60°FWet Bulb
A B C D Dry Bulb 60°F 62°F 75°F 90°F
Wet Bulb 60°F 60.8°F 65.2°F 70°F
Dew Point 60°F 60°F 60°F 60°F
Rel Humidity 100% 92% 60% 37%
DDCCBB
AA
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
moisture content doesn’t change by…
Adding Sensible Heat
100% Saturation
60°FDew Point
60°FWet Bulb
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
Relative Humidity Curves
Relative Humidity
0%
10%
20%
30%
40%50%
60%70%80%90
%100%
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
intersection represents…
Three Air Properties
Humidity RatioHumidity Ratio
Dry BulbDry BulbRelative HumidityRelative Humidity
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
Determining Wet-Bulb Lines
AA
BIBICICI
DIDI
BB CC DDAIAI
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
intersection of two known air properties…
Determines The Remaining Three
Humidity RatioHumidity Ratio
Dry BulbDry BulbRelative HumidityRelative Humidity
Wet BulbWet Bulb
Dew PointDew Point
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
A Final Property…Specific Volume
14.014.013.0
13.0
13.513.5
14.514.5
Specific Volume Lines (cubic feet / pound of dry air)Specific Volume Lines (cubic feet / pound of dry air)
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Adding Sensible Heat
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Removing Sensible Heat
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Adding Moisture
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Removing Moisture
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
effect of changing…
Sensible Heat And Moisture Content
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
effect of changing…
Sensible Heat And Moisture Content
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Psychrometry
period two
Air Mixtures
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air ConditionerAir Conditioner
Supply FanSupply Fan
MixtureMixture OutdoorOutdoorAir (OA)Air (OA)
Recirculated Air Recirculated Air (RA)(RA)
AA
CC
BB
Cooling CoilCooling Coil
Determining Entering Air Conditions
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
80°F80°F95°F95°F
Determining Entering Air Conditions
BB
AA
Outdoor Air
Outdoor Air
Recirculated Air
Recirculated Air
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
1,000 cfm4,000 cfm
= 0.25
OARAMixture
===
25%75%
100%
AA
CC BB4,000 cfm4,000 cfmMixed AirMixed Air4,000 cfm4,000 cfmMixed AirMixed Air
1,000 cfm1,000 cfmOAOA
3,000 cfm3,000 cfmRARA
Determining Entering Air Conditions
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
95°F × 0.25 = 23.75°F 80°F × 0.75 = 60.00°F
Mixture = 83.75°F
Mixed Air Temperature
Determining Entering Air Conditions
83.75°F83.75°F
70°F70°F
Determining Entering Air Conditions
BB
80°F80°F
95°F95°F
CC
AA
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Psychrometry
period three
Sensible Heat Ratio
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Removing Sensible Heat
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Removing Latent Heat
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
effect of…
Removing Sensible And Latent Heat
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Supply AirSupply Air
Sensible HeatSensible Heat
Latent HeatLatent Heat
Return AirReturn Air
supply air conditions determine…
Heat And Moisture Transfer
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
sensible and latent heat…
Effects Of Improper Removal
Cooler& DamperCooler& Damper
Warmer& DrierWarmer& Drier
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
A Look At “Heat Gain” . . .
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
SHR Sensible Heat Gain
Sensible Heat Gain + Latent Heat Gain=
determining the…
Sensible Heat Ratio (SHR)
78°F DB65°F WB78°F DB65°F WB
Index PointIndex Point
Sensible Heat Ratio Scale
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
0.80 SHR Line0.80 SHR Line
Drawing An SHR Line
AAIndex PointIndex Point
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Sensible Heat Ratio LineSensible Heat Ratio Line
Room SHR dictates…
Supply Air Conditions
AA
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
CC
DDBB
80°F80°F
drawing an SHR line for…
Other Room Conditions
0.60 SHR Line0.60 SHR Line
Index PointIndex Point
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Psychrometry
period four
Air Quantity
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Coil CurvesCoil Curves
Coil Curves…show changes in air properties through a cooling coil
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
80,000 Btu/hr sensible heat gain
20,000 Btu/hr latent heat gain
= 0.80
STEP 1: Calculate the sensible heat ratio (SHR)
80,000 Btu/hr100,000 Btu/hrSHR =
Determining Supply Airflow
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Room — 78°F DB, 50% RH
OA — 95°F DB, 78°F WB
Ventilation — 25% OA
Determining Supply Airflow
Design Conditions:
95°F × 0.25 = 23.75°F78°F × 0.75 = 58.50°F
Mixture = 82.25°F
Determining Supply AirflowSTEP 2: Plot room, outdoor, and entering conditions
0.80 SHR0.80 SHRAA
CC
BB
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
56.5°F56.5°F 78°F78°F
STEP 3: Identify supply air conditions
0.80 SHR0.80 SHRAA
CC
BB
DD
Determining Supply Airflow
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Sensible Heat Gain
1.085 × (Room DB – Supply DB)
SupplyAirflow=
STEP 4: Solve the supply airflow equation
Determining Supply Airflow
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
80,000 Btu/hr
1.085 × (78°F – 56.5°F)3,430 cfm=
STEP 4: Solve the supply airflow equation
Determining Supply Airflow
D
A
C B3,430 cfm
56.5°F DB55.2°F WB
RA
OA82.2°F DB68.6°F WB
Mixture
Determining Supply Airflow
SA
56.5°F56.5°F
DD AA
CCBB
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
effect of…
Arbitrarily Using 55°F Supply Air
47,000 Btu/hr sensible heat gain
20,000 Btu/hr latent heat gain
= 0.7047,000 Btu/hr67,000 Btu/hrSHR =
AA
CC
BB
DD
55°F55°F
DIDIAIAI
effect of…
Arbitrarily Using 55°F Supply Air
0.70 SHR0.70 SHR
51°F51°F
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Psychrometry
period five
Tons Of Refrigeration
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
What is Enthalpy?
Enthalpy (h) = Sensible Heat + Latent Heat
The total heat energy in onepound of air (Btu/lb) at its presentcondition:
Determining Tons Of RefrigerationSTEP 1: Find enthalpiesentering andleaving coil
AA
BB
CC
DD32.732.7
23.523.5
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Determining Tons Of Refrigeration
STEP 2: Solve the total refrigeration load equation
4.5 × Supply Airflow × (h1 – h2)Refrigeration Load (Btu/hr)=
where:h1 = enthalpy of air entering coil (Btu/lb)h2 = enthalpy of air leaving coil (Btu/lb)
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
= 11.8 tons of refrigeration
Determining Tons Of Refrigeration
STEP 2: Solve the total refrigeration load equation
4.5 × 3,430 cfm × (32.7 – 23.5) = 142,000 Btu/hr
142,000 Btu/hr12,000 Btu/hr/ton
determining cooling coil…
Sensible And Latent Loads
AA
BB
CC
DD
Sensible LoadSensible Load
Latent LoadLatent Load
32.732.7
23.523.5
29.629.6
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Sensible Coil Load:
4.5 × 3,430 cfm × (29.6 – 23.5) = 94,150 Btu/hr
7.8 tons of refrigeration (sensible)
determining cooling coil…
Sensible And Latent Loads
Latent Coil Load:
4.5 × 3,430 cfm × (32.7 – 29.6) = 47,850 Btu/hr
4.0 tons of refrigeration (latent)
Psychrometry
period six
Psychrometric Analyses
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
SHR Changes Throughout The Day
Full-load conditions
56.5°F56.5°F 78°F78°F
DDAA
BB
CC
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Full Load:
80,000 Btu/hr80,000 Btu/hr + 20,000 Btu/hr SHR =
Part Load:
= 0.80
47,000 Btu/hr47,000 Btu/hr + 20,000 Btu/hr SHR = = 0.70
SHR Changes With Room Load
DD
AA
BB
CC
New SHR Requires New SA Condition
0.80 SHR0.80 SHR
0.70 SHR0.70 SHR
Part-load conditions
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
DD
AA
BB
CC
at part-load, with constant supply airflow …
Raising SA Temp. Increases Room RH
0.80 SHR0.80 SHR
0.70 SHR0.70 SHRAIAI
DIDI
50%
50%
50%
50%60
%60
%60
%60
%
47,000 Btu/hr
1.085 × (78°F – Supply DB)= 3,430 cfm
Supply DB = 65.4°F
65.4°F65.4°F
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
constant quantity of variable-temperature airconstant quantity of variable-temperature air
OA
RA
SA
Constant-Volume System
BBDD CC
AAModulatingModulatingCooling CoilCooling Coil
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Reheat Reheat CoilCoil
CoolingCoolingCoilCoil
RoomRoomThermostatThermostat
adding reheat improves adding reheat improves humidity controlhumidity control
BB
EE
DD CC
AA
Constant-Volume With Reheat
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
DD AA
C
BB
47,000 Btu/hr
1.085 × (78°F – Supply DB)= 3,430 cfm
Supply DB = 65.4°F
Effect Of Adding Reheat…
EE
0.80 SHR0.80 SHR
65.4°F65.4°F56.5°F56.5°F
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Adding Reheat…
DDAA
CC
BB
EE
0.80 SHR0.80 SHR
65.4°F65.4°F56.5°F56.5°F
0.70 SHR0.70 SHR
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
mixed air bypass improves humidity controlmixed air bypass improves humidity control
Mixed Air Bypass
OA
RASA
BB
DDCC
AA
Face-and-Face-and-BypassBypassDampersDampers
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Mixed Air Bypass…
DDAA
CC
BB
EE
82.25°F × 0.455 = 37.4°F51.40°F × 0.545 = 28.0°F
Mixture = 65.4°F
65.4°F65.4°F51.4°F51.4°F
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Effect Of Mixed Air Bypass…
0.70 SHR0.70 SHR
AA
CC
BB
AIAI
65.4°F65.4°F51.4°F51.4°F
DDEE
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Variable-Air-Volume (VAV) System
OA
RA
SA
BBDD
AA
CC
variable quantity of constant-temperature airvariable quantity of constant-temperature air
VSDVSD
DD AA
CC
BB
Calculating Part-Load Airflow
47,000 Btu/hr
1.085 × (78°F – 56.5°F)= 2,015 cfm
0.80 SHR0.80 SHR
0.70 SHR0.70 SHRAIAI
55.5°F55.5°F
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
PC-based software tools…
Simplify Psychrometric Analysis
Psychrometry
period seven
Review
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
30
Dry-Bulb Temperature (°F)
Gra
ins
Of
Mo
istu
re P
er
Po
un
d O
f D
ry A
irW
he
n S
atu
rate
d (
gra
ins/
lb o
f d
ry a
ir)
25 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
20
0
40
60
80
100
120
140
160
180
200
220
review…
Five Properties Of Air
Humidity RatioHumidity Ratio
Dry BulbDry BulbRelative HumidityRelative Humidity
Wet BulbWet Bulb
Dew PointDew Point
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
80°F80°F
95°F95°F
83.75°F83.75°F
70°F70°F
CC
BB
AA
review…
Determining Mixed Air Conditions
95°F × 0.25 = 23.75°F80°F × 0.75 = 60.00°F
Mixture = 83.75°F
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
AA
Sensible Heat Ratio LineSensible Heat Ratio Line
review…
Determining Sensible Heat Ratio
SHR = Sensible Heat Gain
Sensible Heat Gain + Latent Heat Gain
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
AA
CC
BB
DD
Coil Curve
Sensible Heat Gain
1.085 × (Room DB – Supply DB)SupplyAirflow
review…
Determining Coil Leaving Conditions
SHR LineSHR LineSHR LineSHR Line
=
Supply DBSupply DB
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
AA
CC
BB
DD
review…
Determining Tons Of Refrigeration4.5 × Supply Airflow × (h1 – h2) = Refrigeration Load
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
CC
OA
RA
BB
AADD
SA
review…
PsychrometricAnalysis
SHR LineSHR Line
AA
BBCCDD
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
Air Conditioning Clinic TRG-TRC001-ENAir Conditioning Clinic TRG-TRC001-EN© American Standard Inc. 1999
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