how to read a psychrometric chart - rotronic...how to read a psychrometric chart helping you make a...

HowtoReadaPsychrometric Chart

Helping you make a better measurement.

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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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Download theexercisechart:bit.ly/1QiA5zb

BruceMcDuffee MichaelBoetzkes

WebinarPresenters&HumidityExperts

Agenda&TakeawaysAgenda1. WhatisaPsychrometric

Chart?2. Whyshouldyoucare?3. Reviewthechartanatomy4. Exercise1– Wetbulb5. Exercise2– GrowingPlants6. Exercise3- Evaporative

Cooling

Takeaways• Avisualrepresentationcanhelpyoubetterunderstandtheparametersandhowtheyinteractwithtemperaturechanges.

• Usingachartcanbequickerthananonlinecalculatororapp.

WhatisaPsychrometric Chart?

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• Mollier Diagram• Psychrometric Chart• Visualrepresentationofpropertiesofamoistgas

Whyshouldyoucare?

• Helpswithabetterunderstandingofthehumidityparameters• Abetterunderstandinghelpsyoumakeabettermeasurement• Visuallearningcanmeanbetterunderstanding• Quickconversionsinthefield

Parameter

Drybulb temperature

Humidity ratio

Saturationcurve(100%RH)

RelativeHumidity

Dewpointtemperature

VaporPressure

Enthalpy

Wetbulbtemperature

Specific volume (dryair)

Comments&Questions

Ifwedon’tgettoyourquestion today,we’llrespondviaemailafterthewebinar.

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 45%Dewpoint

Vapor pressure

Humidity ratio

Enthalpy


Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 57FVapor pressure .47inHgHumidity ratio 69grainsEnthalpy


Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 57FVapor pressure .47inHgHumidity ratio 69grainsEnthalpy 30BTU/lb


Exercise#1Dry bulb 80FWetbulb 65FRH

Dewpoint

Vapor pressure

Humidity ratio

Enthalpy


Exercise#1Dry bulb 80FWetbulb 65FRH 45%Dewpoint 57FVapor pressure .48inHgHumidity ratio 70gr/lbEnthalpy 30btu/lbSaturationvaporpressure 1.02inHg

Comments&Questions


Exercise2:ControlledEnvironments

MeasuredParameters:• Greenhousemaintainedat40%RHat80°F• Outdoorairis60%RHat40°F

Questions:• Iftheoutdoorairinbroughtinsideandheatedto80°Fwhathappenstothehumidity?• Willtherebecondensationonthegreenhouseglass?

Exercise#2 OutsideDry bulb 40°FWetbulb

RH 60%Dewpoint

Vapor pressure

Humidity ratio

Enthalpy


Exercise#2 Outside WarmedDry bulb 40°F 80°FWetbulb 35°F 54°F

RH 60% 14%Dewpoint 27.3°F 27.3°F

Vapor pressure 0.15inHg 0.15inHg

Humidity ratio 21.8grains/lb

21.8grains/lb

Enthalpy 13BTU/lb 23BTU/lb


0.25in Hg 1.03in Hg

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

RH 40%Dewpoint

Vapor pressure

Humidity ratio

Enthalpy


Comments&Questions


Exercise3:EvaporativeCoolingEfficiency

MeasuredParameters:Denver– 90FTdry,65FTwetNYC– 90FTdry,80FTwet

Task:ProvewhyevaporativecoolingismoreefficientinDenvercomparedtoNYC

Howitworks

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

Dewpoint

Exercise#3 NYC DENDry bulb 90F 90FWetbulb 80F 65FRH 65%Dewpoint 77F

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

Dewpoint

Exercise#3 NYC DENDry bulb 90F 90FWetbulb 80F 65FRH 65% 25%Dewpoint 77F 50F

Comments&Questions


SummaryofthePsychrometric Chart

1. WhatisaPsychrometric Chart?2. Whyshouldyoucare?3. Reviewthechartanatomy4. Exercise1– Wetbulb5. Exercise2– Florist6. Exercise3- EvaporativeCooling

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HumidityAcademy

• Resourcesformakingabettermeasurement• Psychrometric charts• Technicalnotes• Humiditycalculator• Applicationnotes• more

www.rotronic-usa.com/humidity-academy

NextWebinarInterpretingHumidityInstrumentSpecificationsThursday,December10th1:00PMEST• Registeratwww.rotronic-usa.com/humidity-webinars

Takeaways• Learnhowtointerprettheterm"Accuracy". Aspecificationtitled“Accuracy”fromonemanufacturermaynotbecomparabletotheAccuracyspecificationfromasecondmanufacturer.

• Explorethedifferencesinspecificationmethodologiesofseveralmanufactures

• Learnhowtoapplyamethodologythatcanbeusedtoobjectivelycomparethespecifiedperformanceoftheinstruments.

Helpingyoumakeabetterhumiditymeasurement– andmore.

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how to read a psychrometric chart - rotronic...how to read a psychrometric chart helping you make a...

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