Transcript Heat Flux Sensors - Fire protection engineering

Heat Flux Sensors
Isaac T. Leventon
7/17/2015
Heat Flux Measurements
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
• Thermal management of materials
and manufacturing processes
– Annealing, film drying, surface
processing
– Heat exchangers, dryers, boilers,
condensers
• Fire Applications
– Heat transfer as a controlling
mechanism of fire phenomena
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Heat Transfer Fundamentals
Heat Flux Measurement
Heat Transfer Fundamentals
• Heat flux, q” [kW m-2]
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
Lab Methods Day
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1D Planar Heat Flux Sensor
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
Lab Methods Day
7/17/2015
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Schmidt-Boelter Gauge
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
Lab Methods Day
7/17/2015
5
Gardon Gauge
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
• Single thermocouple pair
– Temperature difference from
center to edge is proportional
to incident heat flux
• Fairly simple construction
• Water cooling possible for
high heat fluxes
• Not suited for use with
convection heat transfer
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Radiometers
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
• Separate radiation from
convection using a
transparent window
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
Lab Methods Day
7/17/2015
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Semi-Infinite Surface
Temperature Methods
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
• For short exposures, material
surface temperature history
can define heat transfer
– Assume 1D heat transfer at
surface, no effect at back:
Practical Considerations &
Key Concerns for Use
Calibration
– Time limit to minimize errors:
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Calorimeter Methods
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
• Determine q” by measuring
amount absorbed energy,
assume uniform temperature
• Slug Calorimeter
• Thin Skin Calorimeter
– Thin metal plate welded to a
thermocouple, calculate heat
transfer rate (convection and/or
radiation) assuming 1D heat flow
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Mounting ConsiderationsPhysical Impacts on Flow
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
• Sensor protrusion, depression,
or misalignment at the surface
of the material may produce
a boundary layer disturbance
– Greater effect in laminar systems
– Difficult to quantify or observe
– Blowing effect
Calibration
Lab Methods Day
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Mounting ConsiderationsThermal Impacts on Flow
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
• Under fire conditions,
measured cold gauge heat
flow is typically greater than
net heat transfer into a sample
• Water cooled sensors may
alter the local temperature
gradient in the flow
Lab Methods Day
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Gauge Care and Maintenance
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
• Do not overheat sensors
– Check water flow, if used for
cooling, before each test
– Ensure water is off at end of day
• Using water >65°C to cool a
gauge may limit formation of
deposits at its surface
• Protect your sensors – avoid
dirt, oils, scratches, dust, and
physical damage of the
gauge face
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Calibration
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
• Heat flux sensors should be
50
calibrated
under similar
45
conditions
as their intended use
40
35
• The typical
calibration is given
30
25
as sensor
voltage versus incident
20
15
radiation
10
5
• NIST 250-65
Heat Flux Sensor
0
0
5 (Blackbody
10
15
20
25
Calibration
radiation
Unknown Heat Flux Gauge Voltage (mV)
calibration)
Reference Gauge Measured
Heat Flux (kW m-2)
Heat Flux Measurement
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References to consider
Heat Flux Measurement
Heat Transfer Fundamentals
Spatial Temperature Gradient
Heat Flux Sensors
Schmidt-Boelter
Gardon
Time Temperature Change
Heat Flux Sensors
Semi-Infinite Surface
Temperature Methods
Calorimeters
Practical Considerations &
Key Concerns for Use
Calibration
• Heat Flux, T. E. Diller
• Low Heat Flux Measurements: Some Precautions,
A.F. Robertson and T.J. Ohlemiller (NIST)
• High Temperature Heat Flux Measurements,
Hager et. al (NIST)
• Performance and Modeling of Heat Flux sensors
in Different Environments, D.G. Holmberg and
C.A. Womeldorf (NIST)
• Narrow Angle Wide Spectral Range Radiometer
Design, W. Camperchioli (NASA)
• HEAT FLUX TRANSDUCERS and INFRARED
RADIOMETERS for the DIRECT MEASUREMENT OF
HEAT TRANSFER RATES (Medtherm)
• NIST Measurement Services: Heat-Flux Sensor
Calibration, Tsai et al. (NIST Special Publication
250-65)
Presentation/Conference Name
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Additional equations
• Analytical solution of sampled
temperature data to recreate
heat flux signals
Presentation/Conference Name
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