Instrument Model for Narrow Angle Radiometers KAITLYN SCHEIB, - - PowerPoint PPT Presentation

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Instrument Model for Narrow Angle Radiometers KAITLYN SCHEIB, - - PowerPoint PPT Presentation

Apr 09, 2023 116 likes β€’311 views

Instrument Model for Narrow Angle Radiometers KAITLYN SCHEIB, JENNIFER SPINTI, ANDREW FRY, STAN HARDING, IGNACIO PRECIADO DEPARTMENT OF CHEMICAL ENGINEERING THE UNIVERSITY OF UTAH L1500 1.5 MW Furnace Radiative Section Baghouse Air/FGR/O 2

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SLIDE 1

Instrument Model for Narrow Angle Radiometers

KAITLYN SCHEIB, JENNIFER SPINTI, ANDREW FRY, STAN HARDING, IGNACIO PRECIADO DEPARTMENT OF CHEMICAL ENGINEERING THE UNIVERSITY OF UTAH

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SLIDE 2

L1500 1.5 MW Furnace

FD and Recycle Fan Convective Section Baghouse Air/FGR/O2 Control Radiative Section Burner Sample Ports (Radiometers)

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SLIDE 3

Overview of an Instrument Model

Measured Signal (mV) Quantity of Interest (Incident heat flux) Sources of Uncertainty

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SLIDE 4

Narrow Angle Radiometer Design

  • The change in temperature of the thermistor causes a change in resistance
  • Design based on IFRF and used by PRAXAIR
  • We have identified uncertainties in construction, operation and calibration

𝛽"#

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SLIDE 5

Narrow Angle Radiometer Design: Wheatstone Bridge

π‘Š

%&'( = π‘Š '**

𝑆,-, 𝑆,-, + 𝑆/ βˆ’ 𝑆122 𝑆122 + 𝑆3 𝑆122 = π‘Š

  • 45𝑆/

π‘Š

'** βˆ’ π‘Š

  • 45

𝛽"#

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SLIDE 6

Narrow Angle Radiometer Design: Lens

Focal length (17-25 mm): 𝑔 =

7 ,8/

Reflectivity (0.022-0.041): 𝜍 =

,:8,; ,:<,; 3

𝛽"#

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SLIDE 7

Design Uncertainty

𝛽"#

  • Transient

temperature

  • Irradiated thermistor

temperature

  • Non-irradiated

thermistor placement

  • Measured voltage
  • Refractive index
  • Image size
  • Focal point
  • Lens mounting
  • View angle
  • Reflectivity
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SLIDE 8

Design Uncertainty: Wheatstone Bridge

  • Resistors
  • Two 250 Ω resistors were used in the Wheatstone

bridge

  • Operating temperature range: -55˚C to 150˚C
  • Resistors can drift up to 1% over lifetime
  • Thermistors
  • The temperature of the thermistors is related to the

resistance

  • The operating temperature range of the thermistors is -40˚C

to 125˚C

  • The thermistor resistance can drift up to 1%
  • Β±5% uncertainty between thermistors

π‘ˆ = 𝐡 + πΆπ‘šπ‘œ 𝑆 𝑆2&" + π·π‘šπ‘œ3 𝑆 𝑆2&" + πΈπ‘šπ‘œD 𝑆 𝑆2&"

8/

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SLIDE 9

Design Uncertainty: Transient Temperature Effects on Wheatstone Bridge

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SLIDE 10

Design Uncertainty: View Angle

Radiometer 1 1 3 3 Percent of max 2% 0% 2% 0% View angle 5.67˚ 6.7˚ 3.7˚ 4.16˚ Correction 2D (⍺) 0.286 0.244 0.356 0.318 Correction 3D (⍺) 0.303 0.238 0.552 0.474

π‘ŸF'G

”

= π‘Ÿ1

” 1 βˆ’ 𝜍 𝛽

Camperchioli, William. β€œNarrow Angle Wide Spectral Range Radiometer Design.” NASA, 2005.

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SLIDE 11

Calibration: Muffle Furnace

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 10 20 30 40 50 60 70

Flux (W/m2) mV

Radiometer 3

12/01 - 10cm - mid range 12/02 - 5 cm - mid range 11/28 - 7.6 cm - mid range

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SLIDE 12

Calibration: Low Range Blackbody

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

100 200 300 400 500 25 27 29 31 33 35 37 39

Flux (W/m2) mV

Radiometer 3

10/28 - low range 8/8 - low range 7/12 - low range

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SLIDE 13

Calibration Uncertainty

Mid-range uncertainties

  • Target temperature
  • Graphite sheet
  • Non-uniform temperature
  • Target size
  • Calibration alignment

Low-range uncertainties:

  • Non-uniform temperature
  • Target size
  • Target temperature
  • Oxide layer formation
  • Calibration alignment
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SLIDE 14

Calibration Results

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SLIDE 15

Instrument Uncertainty: Analysis

WHEATSTONE ANALYSIS Voltage divider equation: 𝑆122 =

Z

[\] 7Β±/%

Z

`aaΒ±D%Z 8Z [\]

Wheatstone bridge equation:

π‘Š

%&'( = π‘Š '** Β± 3π‘›π‘Š 7h[hΒ±/% (7h[hΒ±/%)<(7Β±/%) βˆ’ 7kllΒ±/% 7kllΒ±/% <(7Β±/%)

HEAT FLUX ANALYSIS

Input parameters Range View angle 3.7˚ - 4.16˚ View angle area correction (⍺) 0.356 – 0.318 Blackbody temperature Β±10˚C Lens refractive index 1.35 – 1.51

π‘Ÿm

” = πœπ‘ˆm

  • π‘Ÿ1

” = 2π‘Ÿm ” 1 βˆ’ π‘‘π‘π‘‘πœ„

π‘ŸF'G

”

= π‘Ÿ1

” 1 βˆ’ 𝜍 𝛽

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SLIDE 16

Instrument Uncertainty: Results

Tbb (˚C) mV min mV max ±% 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%

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SLIDE 17

Conclusions and Recommendations

Many sources of uncertainty have been identified and accounted for There are still sources of uncertainty not accounted for as seen in the calibration curves The largest source of uncertainty comes from the use of the Wheatstone bridge

  • Β±130% with 1% thermistor uncertainty vs. Β±72% with no thermistor uncertainty

We need more accurate heat flux measurements in the future Recommendations

  • Eliminate Wheatstone bridge: use thermopile instead
  • Smaller view angle and eliminate reflectivity inside tube
  • Higher purge gas flow rate
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SLIDE 18

THANK YOU