jec lecture 5 psychrometrics v2
TRANSCRIPT
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PSYCHROMETRIC
CONDUCTED BY:Engr. Rosendo C. Perez, J r. , P.M.E.
For
J ARDI NE ENERGY CONTROL CORPORATI ON
PSYCHROMETRI CS
RCPerez,Jr., PME
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DEFI NI TI ON
Psychrometrics is the science
of the study of air and its
properties
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PSYCHROMETRI C CHART
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PME
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DRY BULB
DRY BULB
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WET BULB
WET BULB
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ENTHALPY
AI R ENTHALPY
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RELATI VE HUMI DI TY
RELATIVE HUMIDITY
DRY BULB
WET BULB
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RELATIVE HUMIDITY DEFINITION
MOISTURE CONTENT
RELATI VE HUMIDI TY
I t is the ratio of the moisturecontent of the air to its
moisture content when fullysaturated at the same drybulb temperature
FULLY SATURATED AT
THE SAME DRY BULB
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DEW POI NT TEMPERATURE
AND SPECI FI C HUMI DI TY
DEW POI NT TEMPERATURE
MOI STURE CONTENT OR
SPECIFI C HUMI DITY ORHUMIDI TY RATI O
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PME
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Humidification Addition of moisture
Dehumidification Removal of moisture
PSYCHROMETI C DEFI NI TI ON
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HUMI DI FI CATI ON AND
DEHUMI DI FI CATI ON
Dehumidification
Humidification
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PME
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Cooling and Dehumidif ication &Heating and Humidif ication
Cooli
ng&De
humi
difica
tion
Heati
ng&Hum
idific
ation
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PME
COOLI NG & HUMI DI FI CATI ON
HEATI NG & DEHUMI DI FI CATI ON
Cooling&Humidification
Heating&Dehumidification
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PME
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COOLI NG & HUMI DI FI CATI ON
Cooling&
Hum
idification
Adiabatic Saturation
DB
WB
DP
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WATER SPRAY
Adiabatic Saturation
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PSYCHROMETRI C PROCESSES
Sensible cooling Sensible Heating
Dehumidification
Humidification
Cooli
ng&Deh
umidi
ficati
on
Heating
&Hum
idific
ation
Cooling&Humidification
Heating&Dehumidification
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PSYCHROMETRI C CHART Total,
Sensible and Latent Heat
Sensible
Heat
T1
2
Temperature
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PME
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PSYCHROMETRI C CHART Total,Sensible and Latent Heat
Latent
Heat
G
1
2
Moisture
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PME
PSYCHROMETRI C CHART Total,
Sensible and Latent Heat
Sensible
Heat
Late
nt
Heat
TotalH
eat
T
G(H
)
1
2
Temperature
Moisture
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PME
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AIR CONDITIONING PROCESS
AHU
Return Air
Supply Air
Outside Air
ROOM
Exfiltration air
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AI R CONDI TI ONI NG PROCESS
Coil Entering Air Temperature
Room and Outside air Mixture
Apparatus Dew Point
Coil Leaving Air Temperature
Outside Air Temperature
Room Air Temperature
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Entering and Leaving Conditionat the Apparatus
Supply Air Temperature
Coil Entering
Air Temperature
Apparatus Dew Point
Calculated Entering
Dry Bulb Temperature
Calculated Entering
Dry Bulb Temperature
EnteringWetBulb
Temperature
Leaving WetBulb
Temperature
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PME
Room Sensible Heat Factor
Alignment CircleRSHF
RSHF
Room Condition
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Grand Sensible Heat Factor
Coil Entering Air Temperature
Alignment Circle
GSHFApparatus
Dew Point
GSHF
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Ef f ective Sensible Heat Factor
Alignment Circle
ESHF
ESHF
ApparatusDew Point
Coil Entering Air Temperature
Room Condition
Supply air temperature
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By- pass Factor
Supply air temperature
Coil entering air temperature
BF
1-BF
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PME
No By- pass Factor
Supply air temperature
Coil entering air temperatureNo
coilb
y-pass
ADP
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Ef f ects of By- pass Factor
Supply air temperature
Coil entering air temperature
BF
1-BF
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Effects of By-pass Factor1) Smaller By-pass Factor
a) Higher ADP For DX and Chilled water equipment selected forhigher chilled water temperature
b) Coil will require less air
c) Coil will have more heat transfer area
d) Will require smaller pipe diameter for chilled water system, due toless flow requirement. Smaller pump-motor drive.
2) Larger by-pass factor
a) Lower ADP
b) Coil will require more air
c) Coil will have less heat transfer area
d) Will require larger pipe diameter for chilled water system, due tomore flow requirement. Bigger pump-motor drive.
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COOLING LOAD CASE STUDY
REFER TO THE SAMPLE COOLING LOAD
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AI R CONDI TI ONI NG PROCESS
Outside Air 95F / 82.2F
Room Air 75F / 55% RH
146 Gr.
71.5 Gr.
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EFFECTI VE SENSI BLE HEAT FACTOR
0.81
54.7 Adp
Alignment Circle
ESHF
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Entering Air Temperature
EAT =(CFMRM x TEMP.RM) + (CFMOA x TEMP.OA)
TOTAL CFM
17,355 (75) +2,025 (95)
19,380=
=77.1 F
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ENTERI NG AI R TEMPERATURE
54.7 Adp
EAT = 77.1 F DB / 66.2 F WB
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GRAND SENSI BLE HEAT FACTO
Alignment Circle
0.70
GSHF
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ROOM SENSI BLE HEAT FACTOR
Alignment Circle
RSHF
0.82
56.9 F DB / 56.0 F WB
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AI R CONDI TI ONI NG PROCESS
Coil Entering Air Temperature
Room and Outside air Mixture
Apparatus Dew Point
Coil Leaving Air Temperature
Outside Air 95F / 82.2F
Room Air 75F / 55% RH
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COOLING AND DEHUMIDIFICATION WITHHIGH LATENT LOAD
Supply air temperature
Coil entering air temperature
Leaving coil air temperature GSHF
RSHF
Reheat
ADP
Alignment Circle
ESHF
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PME
Hundred per cent Outside Air
Coil leaving air temperature
Coil entering air temperature
Room condition
Apparatus Dew Point
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Comparison of One Hundred per centOutside Air to Regular Air Conditioning
Coil leaving air temperature
Coil entering air
temperature
Room condition
Apparatus Dew Point
100%
OutsideAir
Reg
ular
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PME
Air Conditioning Process
Unit with a defined capacity
(CASE 1)
Alignment Circle
SHF
Supply air temperatureApparatus Dew Point
LH
SH
TH
T
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TLvg = Tadp + BF (TEnt. Air Tadp)
hLvg = hadp + BF (hEnt. Air hadp)
Psychrometric Formula
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Air Conditioning Process
Unit used with a SHF factorless than specified
(CASE 2)
Alignment Circle
SHF
Supply air temperatureApparatus Dew Point
LH
SH
TH
T
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Air Conditioning Process
Unit is used with a much
greater Latent load(CASE 3)
Supply air temperature
Alignment Circle
SHF
Apparatus Dew Point
LH
SH
TH
T
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Re- heatApplication
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Laboratory
Data:
Outside air condition: 95F DB / 82F WB
Inside condition: 75F DB / 55% RH
Room Sensible Heat: 160,000 Btu / Hr.
Room Latent Heat: 100,000 Btu / Hr.
Ventilation requirement: 2,500 CFM
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Find:1) Outside air total heat
2) Effective Sensible Heat Factor
3) Reheat required
4) Dehumidified CFM
5) Entering DB condition
6) Leaving Db condition7)Supply air temperature to the space
8) Grand total heat
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1) Outside Air Total Heat
OASH = 1.08 X CFM X (TOA TRm)
= 1.08 x 2,500 x (95 75)
= 54,000 Btu / Hr.
OALH = 0.68 X CFM X (WOA WRm)
= 0.68 x 2,500 x (146 71.5)
= 126,650 Btu / Hr.
OATH = 54,000 + 126,650 Btu / Hr.
= 180,650 Btu / Hr.
RCPerez,Jr., PME
2) Effective Sensible Heat Factor
ESHF =RSH +.05 (OASH)
RSH +.05 (OASH) +RLH + .05 (OALH)
ESHF =160,000 +.05 (54,000 Btu / Hr.)
160,000 +.05 (54,000 Btu / Hr.) +100,000 + .05 (126,650)
ESHF = 0.605
(ESHF is just too low on the psychrometric chart,therefore, re-heat will be required)
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3) Re-heat computation:
From apparatus due point table @ 75 F / 55 %,with ESHF = 0.69, select Adp = 50F
ESHF (0.69) =162,700 + Re-heat
162,700 + Re-heat + 106,330
Re-heat = 73,971 Btu / Hr.
RCPerez,Jr., PME
4) Dehumidified CFM Computation:
ERSH =1.08 X CFMDa X (1-BF) X (TRm TAdp.)
CFMDa =ERSH
1.08 X (1- BF) X (TRm TAdp.)
CFMDa =160,000 +.05 (54,000) +73,971
1.08 X (1- .05) X (75 50)
CFMDa = 9,227 use 9,230 CFM
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6) Leaving Dry Bulb (DB) Computation:
TLvg = Tadp + .05 (TEnt. Air Tadp)
TLvg = 50 + .05 (80.4 50)
TLvg = 51.52 F
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7) Supply air Temp. to Space Dry Bulb (DB)
TSa = TRm -RSH
1.08 CFMDa
TSa = 75 -160,000
1.08 X 9,230
TSa = 58.95 F
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7) Supply air Temp. to Space Dry Bulb (DB)(Alternate solution)
TSa = TAdp +Re-Heat
1.08 CFMDa
TSa = 51.52 +73,971
1.08 X 9,230
TSa = 58.94 F
RCPerez,Jr., PME
8) Grand Total Heat
GTH = 4.5 CFM X (heat hlat)
= 4.5 X 9,230 X (33.67 20.97)
= 527,495 Btu / Hr.
= 43.95 TR
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Air Conditioning Process
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Leaving air
temperature
Apparatus Dew Point
Alignment Circle
Reheat
Supply air
temperature
GSHF = 0.49
GSHF = 0.56
ESHF = 0.69
RSHF = 0.62GTH
33.67
20.97
ESHF = 0.61
Air Conditioning Process
Leaving air temperatureApparatus Dew Point
Alignment Circle
GSHF = 0.56
ESHF = 0.69
RSHF = 0.70
33.67
20.97
GTH
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100% OutdoorAir Application
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Application: Laboratory100% Outdoor Air
Data:
Outside air condition: 95F DB / 82F WB
Inside condition: 75F DB / 55% RH
Room Sensible Heat: 234,000 Btu / Hr.
Room Latent Heat: 100,000 Btu / Hr.
Ventilation requirement: 2,500 CFMRCPerez,Jr., PME
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Find:
1) Outside air total heat (OATH)
2) Effective Sensible Heat Factor (ESHF)
3) Apparatus Dew Point (Adp)
4) Dehumidified Air Quantity (CFM)
5) Recalculate Outdoor Air Total Heat (OATH)
6) Recalculate Effective Sensible Heat Factor (ESHF)
7) Final Apparatus Dew Point (Adp)
8) Recalculated Dehumidified Air Quantity (CFM)
RCPerez,Jr., PME
1) Outside Air Total Heat
OASH = 1.08 X CFM X (TOA TRm)
= 1.08 x 2,500 x (95 75)
= 54,000 Btu / Hr.
OALH = 0.68 X CFM X (WOA WRm)
= 0.68 x 2,500 x (146 71.5)
= 126,650 Btu / Hr.
OATH = 54,000 + 126,650 Btu / Hr.
= 180,650 Btu / Hr.
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2) Effective Sensible Heat Factor
ESHF =RSH +.05 (OASH)
RSH +.05 (OASH) +RLH + .05 (OALH)
ESHF =234,000 +.05 (54,000 Btu / Hr.)
234,000 +.05 (54,000 Btu / Hr.) +100,000 + .05 (126,650)
ESHF = 0.69 Adp = 50 F
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3) Apparatus Dew Point
ESHF = 0.69
Adp = 50 F
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4) Dehumidif ied CFM Computation:
ERSH =1.08 X CFMDa X (1-BF) X (TRm TAdp.)
CFMDa =ERSH
1.08 X (1- BF) X (TRm TAdp.)
CFMDa =234,000 +.05 (54,000)
1.08 X (1- .05) X (75 50)
CFMDa = 9,228 use 9,230 CFM
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5) Recalculate Outdoor Air Load
OASH = 1.08 X CFM X (TOA TRm)
= 1.08 x 9,230 x (95 75)
= 199,368 Btu / Hr.
OALH = 0.68 X CFM X (WOA WRm)
= 0.68 x 9,230 x (146 71.5)
= 467,592 Btu / Hr.
OATH = 199,368 + 467,592 Btu / Hr.
=666,960 Btu / Hr.
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6) Recalculate Effective Sensible Heat Factor
ESHF =RSH +.05 (OASH)
RSH +.05 (OASH) +RLH + .05 (OALH)
ESHF =234,000 +.05 (199,368 Btu / Hr.)
234,000 +.05 (199,368 Btu / Hr.) +100,000 + .05 (467,592)
ESHF = 0.664
RCPerez,Jr., PME
7) Recalculate Apparatus Dew Point
ESHF = 0.664
Adp = 49.10 F
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8) Recalculate Dehumidified CFM Computation:
ERSH =1.08 X CFMDa X (1-BF) X (TRm TAdp.)
CFMDa =ERSH
1.08 X (1- BF) X (TRm TAdp.)
CFMDa =234,000 +.05 (199,368)
1.08 X (1- .05) X (75 49.1)
CFMDa = 9,181 use 9,180 CFM
Original CFM =9,230
Recalculated CFM =9,180
Difference =50 CFM, Therefore, there is no need to recalculate CFMRCPerez,Jr., PME
100% Outside Air
Alignment circle
GTH
Rm
.Load
45.75
29.18
21.10
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Entering Dry Bulb (DB) Computation:
Tedb =(CFMOA X TOA) + (CFMRm X TRm)
CFMOA + CFMRm
Tedb =(2,500 X 95) + (6,680 X 75)
9,180
Tedb = 80.4 F
RCPerez,Jr., PME
hedb = 33.25
If condition is not 100% Outside Air
Comparison
Alignment circle
GTH
Rm
.Load
45.75
29.18
21.10
33.25
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Grand Total Heat Comparison Between
100% O.A. and Recirculated Air
GTH = 4.5 CFM X (heat hlat)
= 4.5 X 9,180 X (45.75 21.10)
= 1,688,274 Btu / Hr.
= 83.92 TR
GTH = 4.5 CFM X (heat hlat)
= 4.5 X 9,180 X (33.25 21.10)
= 496,339.7 Btu / Hr.
= 41.33 TR
THANK YOU
For
LI STENI NG
RCPerez,Jr., PME