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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
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