HowtoReadaPsychrometric Chart

Helping you make a better measurement.

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35 WET BULB TEM

PERATURE - °C

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10% RELATIVE HUMIDITY

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.76

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610 Meters above Sea LevelBAROMETRIC PRESSURE 707 mm of Mercury

Linric Company Psychrometric Chart, www.linric.com

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BruceMcDuffee MichaelBoetzkes

WebinarPresenters&HumidityExperts

Agenda&TakeawaysAgenda1. WhatisaPsychrometric

Chart?2. Whyshouldyoucare?3. Reviewthechartanatomy4. Exercise1– Wetbulb5. Exercise2– Warehouse6. Exercise3- Evaporative

Cooling

Takeaways• Avisualrepresentationcanhelpyoubetterunderstandtheparametersandhowtheyinteractwithtemperaturechanges.

• Usingachartcanbequickerthananonlinecalculatororapp.

WhatisaPsychrometric Chart?

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DRY BULB TEMPERATURE - °C

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35 WET BULB TEM

PERATURE - °C

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10% RELATIVE HUMIDITY

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90%

.76

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.94 S

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610 Meters above Sea LevelBAROMETRIC PRESSURE 707 mm of Mercury

Linric Company Psychrometric Chart, www.linric.com

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• Mollier Diagram• Psychrometric Chart• Visualrepresentationofpropertiesofamoistgas

WhyBotherwithaPsychrometricChart?

• Helpswithabetterunderstandingofthehumidityparameters

• Abetterunderstandinghelpsyoumakeabettermeasurement

• Visuallearningcanmeanbetterunderstanding

• Quickconversionsinthefield

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Parameter

Drybulbtemperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume(dryair)

Quiz

Exercise1:Wetbulb– Drybulbconversions

MeasuredParameters:Tdry =80FTwet =65F

Task:Determinetheotherparameters

Exercise#1Dry bulb 80FWetbulb 65FRH

Dewpoint

Vapor pressure

Humidity ratio

Enthalpy

Saturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH

Dewpoint

Vapor pressure

Humidity ratio

Enthalpy

Saturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint

Vapor pressure

Humidity ratio

Enthalpy

Saturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint

Vapor pressure

Humidity ratio

Enthalpy

Saturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 56.5FVapor pressure .47inHGHumidity ratio 69grainsEnthalpy

Saturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 56.5FVapor pressure .47inHgHumidity ratio 69grainsEnthalpy

Saturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 56.5FVapor pressure .47inHgHumidity ratio 69gr/lbEnthalpy 30BTU/lbSaturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 56.5FVapor pressure .47inHgHumidity ratio 69grainsEnthalpy 30BTU/lb

Saturationvaporpressure

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 56.5FVapor pressure .47inHgHumidity ratio 69grainsEnthalpy 30BTU/lb

Saturationvaporpressure 1.02inhg

Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 56.5FVapor pressure .47inHgHumidity ratio 69gr/lbEnthalpy 30btu/lbSaturationvaporpressure 1.02inHg

Comments&Questions

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Exercise2:ControlledEnvironments

MeasuredParameters:• Warehousemaintainedat40%RHat80°F• Outdoorairis60%RHat40°F

Questions:• Iftheoutdoorairinbroughtinsideandheatedto80°Fwillyouhavetohumidify,de-humidifyordonothing?

• Willtherebecondensationonthewindows?

Exercise#2 OutsideDry bulb 40°FWetbulb

RH 60%Dewpoint

Vapor pressure

Humidity ratio

Enthalpy

Saturationvaporpressure

Will you have to humidify, de-humidify or do nothing?

Exercise#2 Outside WarmedDry bulb 40°F 80°FRH 60%

Exercise#2 Outside WarmedDry bulb 40°F 80°FRH 60% 14%

Exercise#2 Ambient GlassDry bulb 80°F 40°FWetbulb

RH 40%Dewpoint

Vapor pressure

Humidity ratio

Enthalpy

Saturationvaporpressure

Will there be condensation on the windows?

Exercise#2 Ambient GlassDry bulb 80°F 40°FRH 40%Dewpoint

Exercise#2 Ambient GlassDry bulb 80°F 40°FRH 40%Dewpoint 53°F 53°F

Quiz

Exercise3:EvaporativeCoolingEfficiency

MeasuredParameters:Denver:90F,25%RHNYC: 90F,65%RH

Task:ProvewhyevaporativecoolingismoreefficientinDenvercomparedtoNYC

Howitworks

Exercise#3 NYCDry bulb 90FRH 65%

Exercise#3 NYCDry bulb 90FWetbulb 80FRH 65%

Exercise#3 NYC DENDry bulb 90F 90FWetbulb 80FRH 65% 25%

Exercise#3 NYC DENDry bulb 90F 90FWetbulb 80F 65FRH 65% 25%

Comments&Questions

Ifwedon’tgettoyourquestiontoday,we’llrespondviaemailafterthewebinar.

SummaryofthePsychrometric Chart

1. WhatisaPsychrometric Chart?2. Whybother?3. Reviewthechartanatomy4. Exercise1– Wetbulb5. Exercise2– Warehouse6. Exercise3- EvaporativeCooling

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35 WET BULB TEM

PERATURE - °C

35

10% RELATIVE HUMIDITY

20%

30%

40%

50%

60%

70%

80%

90%

.76

.78

.80

.82

.84

.86

.88

.90

.92

.94 S

PE

CIF

IC V

OLU

ME

m³/k

g O

F D

RY

AIR

.96

.98

1.0

0

1.0

2

HU

MID

ITY

RA

TIO

- G

RA

MS

OF

MO

IST

UR

E P

ER

KIL

OG

RA

M O

F D

RY

AIR

610 Meters above Sea LevelBAROMETRIC PRESSURE 707 mm of Mercury

Linric Company Psychrometric Chart, www.linric.com

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