JEC Lecture 5 Psychrometrics V2

8/12/2019 JEC Lecture 5 Psychrometrics V2

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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


Alignment Circle

GSHFApparatus

Dew Point

GSHF

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Ef f ective Sensible Heat Factor

Alignment Circle

ESHF

ESHF

ApparatusDew Point


Room Condition

Supply air temperature

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By- pass Factor


Coil entering air temperature

BF

1-BF

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PME

No By- pass Factor


Coil entering air temperatureNo

coilb

y-pass

ADP

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Ef f ects of By- pass Factor



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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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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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



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


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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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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Unit is used with a much

greater Latent load(CASE 3)


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

RCPerez,Jr., PME

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


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

RCPerez,Jr., PME


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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

RCPerez,Jr., PME


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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

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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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RCPerez,Jr., PME

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


Leaving air temperatureApparatus Dew Point

Alignment Circle

GSHF = 0.56

ESHF = 0.69

RSHF = 0.70

33.67

20.97

GTH

RCPerez,Jr., PME


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100% OutdoorAir Application

RCPerez,Jr., PME

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


= 1.08 x 2,500 x (95 75)

= 54,000 Btu / Hr.


= 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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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

RCPerez,Jr., PME

3) Apparatus Dew Point

ESHF = 0.69

Adp = 50 F

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4) Dehumidif ied CFM Computation:


CFMDa =ERSH

1.08 X (1- BF) X (TRm TAdp.)

CFMDa =234,000 +.05 (54,000)

1.08 X (1- .05) X (75 50)


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5) Recalculate Outdoor Air Load


= 1.08 x 9,230 x (95 75)

= 199,368 Btu / Hr.


= 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 =234,000 +.05 (199,368 Btu / Hr.)

234,000 +.05 (199,368 Btu / Hr.) +100,000 + .05 (467,592)

ESHF = 0.664

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7) Recalculate Apparatus Dew Point

ESHF = 0.664

Adp = 49.10 F

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8) Recalculate Dehumidified CFM Computation:


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)


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

RCPerez,Jr., PME


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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

RCPerez,Jr., PME


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Grand Total Heat Comparison Between

100% O.A. and Recirculated Air


= 4.5 X 9,180 X (45.75 21.10)

= 1,688,274 Btu / Hr.

= 83.92 TR


= 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

JEC Lecture 5 Psychrometrics V2

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Transcript of JEC Lecture 5 Psychrometrics V2