InstrumentModelforNarrowAngleRadiometersKAITLYNSCHEIB, JENNIFERSPINTI, ANDREWFRY, STANHARDING,IGNACIOPRECIADODEPARTMENTOFCHEMICALENGINEERINGTHEUNIVERSITYOFUTAH

L15001.5MWFurnace

FDandRecycleFan

ConvectiveSection

BaghouseAir/FGR/O2Control

RadiativeSection

Burner

SamplePorts(Radiometers)

OverviewofanInstrumentModel

MeasuredSignal(mV)

QuantityofInterest(Incidentheatflux)

SourcesofUncertainty

NarrowAngleRadiometerDesign◦ Thechangeintemperatureofthethermistorcausesachangeinresistance◦ DesignbasedonIFRFandusedbyPRAXAIR◦ Wehaveidentifieduncertaintiesinconstruction,operationandcalibration

𝛼"#

NarrowAngleRadiometerDesign:WheatstoneBridge

𝑉%&'( = 𝑉'**𝑅,-,

𝑅,-, + 𝑅/−

𝑅122𝑅122 + 𝑅3 𝑅122 =

𝑉-45𝑅/𝑉'** − 𝑉-45

𝛼"#

NarrowAngleRadiometerDesign:LensFocallength(17-25mm):𝑓 = 7

,8/

Reflectivity(0.022-0.041):𝜌 = ,:8,;,:

DesignUncertainty

𝛼"#

• Transienttemperature

• Irradiatedthermistortemperature

• Non-irradiatedthermistorplacement

• Measuredvoltage

• Refractiveindex• Imagesize• Focalpoint• Lensmounting

• Viewangle• Reflectivity

DesignUncertainty:WheatstoneBridge◦ Resistors◦ Two250ΩresistorswereusedintheWheatstonebridge

◦ Operatingtemperaturerange:-55˚Cto150˚C◦ Resistorscandriftupto1%overlifetime

◦ Thermistors◦ Thetemperatureofthethermistorsisrelatedtotheresistance

◦ Theoperatingtemperaturerangeofthethermistorsis-40˚Cto125˚C

◦ Thethermistorresistancecandriftupto1%◦ ±5%uncertaintybetweenthermistors

𝑇 = 𝐴 + 𝐵𝑙𝑛𝑅𝑅2&"

+ 𝐶𝑙𝑛3𝑅𝑅2&"

+ 𝐷𝑙𝑛D𝑅𝑅2&"

8/

DesignUncertainty:TransientTemperatureEffectsonWheatstoneBridge

DesignUncertainty:ViewAngleRadiometer 1 1 3 3

Percentofmax 2% 0% 2% 0%

Viewangle 5.67˚ 6.7˚ 3.7˚ 4.16˚

Correction2D(⍺) 0.286 0.244 0.356 0.318

Correction 3D(⍺) 0.303 0.238 0.552 0.474

𝑞F'G” = 𝑞1” 1 − 𝜌 𝛼

Camperchioli, William. “Narrow Angle Wide Spectral Range Radiometer Design.” NASA, 2005.

Calibration:MuffleFurnace

01002003004005006007008009001000110012001300

0 10 20 30 40 50 60 70

Flux(W

/m2)

mV

Radiometer3

12/01- 10cm- midrange

12/02- 5cm- midrange

11/28- 7.6cm- midrange

Calibration:LowRangeBlackbody

https://www.landinst.com/products/landcal-r1200p-high-temperature-portable

0

100

200

300

400

500

25 27 29 31 33 35 37 39

Flux(W

/m2)

mV

Radiometer3

10/28- lowrange

8/8- lowrange

7/12- lowrange

CalibrationUncertaintyMid-rangeuncertainties◦ Targettemperature◦ Graphitesheet◦ Non-uniformtemperature◦ Targetsize◦ Calibrationalignment

Low-rangeuncertainties:◦ Non-uniformtemperature◦ Targetsize◦ Targettemperature◦ Oxidelayerformation◦ Calibrationalignment

CalibrationResults

InstrumentUncertainty:AnalysisWHEATSTONEANALYSIS

Voltagedividerequation:

𝑅122 =Z[\] 7±/%

Z̀ aa±D%Z 8Z[\]

Wheatstonebridgeequation:

𝑉%&'( = 𝑉'** ± 3𝑚𝑉7h[h±/%

(7h[h±/%)

InstrumentUncertainty:Results

Tbb (˚C) mVmin mVmax ±%

600 -21.591 71.374 186.74%

800 -15.393 78.089 149.10%

1000 -4.570 89.815 110.722%

1200 11.699 107.441 80.361%

ConclusionsandRecommendationsManysourcesofuncertaintyhavebeenidentifiedandaccountedfor

Therearestillsourcesofuncertaintynotaccountedforasseeninthecalibrationcurves

ThelargestsourceofuncertaintycomesfromtheuseoftheWheatstonebridge◦ ±130% with1%thermistoruncertaintyvs.±72% withnothermistoruncertainty

Weneedmoreaccurateheatfluxmeasurementsinthefuture

Recommendations◦ EliminateWheatstonebridge:usethermopileinstead◦ Smallerviewangleandeliminatereflectivityinsidetube◦ Higherpurgegasflowrate

THANKYOU