Hukseflux FHF04SC User manual

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USER MANUAL FHF04SC
Self-calibrating foil heat flux sensor with thermal
spreaders and heater
Hukseflux
Thermal Sensors

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Cautionary statements
Cautionary statements are subdivided into four categories: danger, warning, caution and
notice according to the severity of the risk.
DANGER
Failure to comply with a danger statement will lead to death or serious
physical injuries.
WARNING
Failure to comply with a warning statement may lead to risk of death or
serious physical injuries.
CAUTION
Failure to comply with a caution statement may lead to risk of minor or
moderate physical injuries.
NOTICE
Failure to comply with a notice may lead to damage to equipment or may
compromise reliable operation of the instrument.

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Contents
Cautionary statements 2
Contents 3
List of symbols 4
Introduction 5
1Ordering and checking at delivery 9
1.1 Ordering FHF04SC 9
1.2 Included items 9
1.3 Quick instrument check 10
2Instrument principle and theory 11
2.1 Theory of operation 11
2.2 The self-test 14
2.3 Calibration 14
2.4 Application example 15
2.5 Application example: non-invasive core temperature measurement 17
3Specifications of FHF04SC 18
3.1 Specifications of FHF04SC 18
3.2 Dimensions of FHF04SC 21
4Standards and recommended practices for use 22
4.1 Heat flux measurement in industry 22
5Installation of FHF04SC 23
5.1 Site selection and installation 23
5.2 Installation on curved surfaces 25
5.3 Electrical connection 26
5.4 Requirements for data acquisition / amplification 29
6Maintenance and trouble shooting 30
6.1 Recommended maintenance and quality assurance 30
6.2 Trouble shooting 31
6.3 Calibration and checks in the field 32
7Appendices 34
7.1 Appendix on wire extension 34
7.2 Appendix on using FHF04SC with BLK – GLD sticker series 35
7.3 Appendix on standards for calibration 36
7.4 Appendix on calibration hierarchy 36
7.5 Appendix on correction for temperature dependence 37
7.6 Appendix on measurement range for different temperatures 38
7.7 Appendix on temperature measurement accuracy 39
7.8 EU declaration of conformity 40

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List of symbols
Quantities Symbol Unit
Heat flux ΦW/m²
Voltage output U V
Sensitivity S V/(W/m2)
Temperature T °C
Thermal resistance per unit area Rthermal,A K/(W/m²)
Area A m²
Electrical resistance R Ω
Electrical power P W
subscripts
property of heatsink heatsink
property of heater heater
property of sensor sensor
maximum value, specification limit maximum

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Introduction
FHF04SC is a combination of the standard model FHF04 heat flux sensor and a heater.
The heater allows the user to perform self-tests, verifying sensor functionality and
stability during use, without having to remove the sensor. FHF04SC is ideal for high-
accuracy and long-term heat flux measurement, construction of calorimeters, (zero heat
flux) core temperature measurement and thermal conductivity test equipment.
FHF04SC measures heat flux through the object in which it is incorporated or on which it
is mounted, in W/m2. The sensor in FHF04SC is a thermopile. This thermopile measures
the temperature difference across FHF04SC’s flexible body. A type T thermocouple is
integrated as well. The thermopile and thermocouple are passive sensors; they do not
require power.
Multiple small thermal spreaders, which form a conductive layer covering the sensor,
help reduce the thermal conductivity dependence of the measurement. With its
incorporated spreaders, the sensitivity of FHF04SC is independent of its environment.
Many competing sensors do not have thermal spreaders. The passive guard area around
the sensor reduces edge effects and is also used for mounting.
Figure 0.1 FHF04SC self-calibrating foil heat flux sensor with thermal spreaders and
heater, showing its front and back side

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Measuring heat flux, users may wish to regularly check their sensor performance. During
use, the film heater is activated to perform a self-test. The heat flux sensor response to
the self-test results in a verification of sensor performance. Implicitly also wire
connection, data acquisition, thermal connection of the sensor to its environment and
data processing are tested. Heat flux sensors are often kept installed for as long as
possible. Using self-testing, the user no longer needs to take sensors to the laboratory to
verify their stable performance. In a laboratory environment, using a metal heat sink,
you may even perform a formal calibration. The heater has a well characterised and
traceable surface area and electrical resistance.
The FHF04SC self-calibrating foil heat flux sensor has unique features and benefits:
•heater for self-test
•flexible (bending radius ≥ 15 x 10-3 m)
•low thermal resistance
•wide temperature range
•fast response time
•integrated type T thermocouple
•robustness, including metal connection block, may be used as strain relief
•IP protection class: IP67 (essential for outdoor application)
•integrated thermal spreaders for low thermal conductivity dependence
FHF04SC’s suggested use:
•high-accuracy scientific measurement of heat flux, with a high level of data quality
assurance
•study of convective heat transfer mechanisms
•calorimeter prototyping
•(zero heat flux) non-invasive core temperature measurement
•thermal conductivity test equipment
\
Figure 0.2 Application example: FHF04SC being installed to measure heat flux on a pipe

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Using FHF04SC is easy. It can be connected directly to commonly used data logging
systems. The heat flux in W/m2is calculated by dividing the FHF04SC output, a small
voltage, by the sensitivity. The sensitivity is provided with FHF04SC on its product
certificate.
Equipped with wires with strain relief, protective covers on both sides and potted so that
moisture does not penetrate the metal connection block, FHF04SC has proven to be very
robust and stable. The connection block may be used as strain relief between sensors
and wires.
FHF04SC calibration is traceable to international standards. The factory calibration
method follows the recommended practice of ASTM C1130 - 17. When used under
conditions that differ from the calibration reference conditions, the FHF04SC sensitivity to
heat flux may be different than stated on its certificate. See Chapter 2 in this manual for
suggested solutions.
Would you like to study energy transport / heat flux in detail? Hukseflux helps taking this
measurement to the next level: order FHF04SC with radiation-absorbing black and
radiation-reflecting gold stickers. You can then measure convective + radiative flux with
one, and convective flux only with the other. Subtract the 2 measurements and you have
radiative flux. They can be applied to the sensor by the user or at the factory; see the BLK
– GLD sticker series user manual and installation video for instructions.
Figure 0.3 FHF04SC heat flux sensor: with BLK-5050 and GLD-5050 stickers
absorbs radiation
reflects radiation

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See also:
•model FHF04, our standard model for general-purpose heat flux measurement
•model FHF03, our most economical foil heat flux sensor
•model HFP01 for increased sensitivity (also consider putting two or more FHF04s in
series)
•BLK - GLD sticker series to separate radiative and convective heat fluxes
•Hukseflux offers a complete range of heat flux sensors with the highest quality for any
budget

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1Ordering and checking at delivery
1.1 Ordering FHF04SC
The standard configuration of FHF04SC is with 2 metres of wire.
Common options are:
•with 5 metres wire length
•with LI19 hand-held read-out unit / datalogger; NOTE: LI19 does not measure
temperature, only heat flux
•BLK-5050 black sticker (to measure radiative as well as convective heat flux)
•GLD-5050 gold sticker (to measure convective heat flux only)
•BLK - GLD sticker series can also be ordered pre-applied at the factory
1.2 Included items
Arriving at the customer, the delivery should include:
•heat flux sensor FHF04SC with wires of the length as ordered
•product certificate matching the instrument serial number
Figure 1.2.1 FHF04SC’s serial number and sensitivity are visible on the metal connection
block. FHF04SC is delivered with bundled wiring.

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1.3 Quick instrument check
A quick test of the instrument can be done by connecting it to a multimeter.
1. Check the sensor serial number and sensitivity on the sticker on the metal connection
block against the product certificate provided with the sensor.
2. Inspect the instrument for any damage.
3. Check the electrical resistance of the sensor between the red [+] and black [-] wires.
Use a multimeter at the 1k Ω range. Measure the sensor resistance first with one
polarity, then reverse the polarity. Take the average value. The typical resistance of the
wiring is 0.1 Ω/m. Typical resistance should be the nominal sensor resistance of 200 Ω
plus 0.2 Ω for the total resistance of two wires (back and forth) for each m. Infinite
resistance indicates a broken circuit; zero or a lower than 1 Ω resistance indicates a short
circuit.
4. Check the electrical resistance of the thermocouple between the brown [+] and white
[-] wires. Use a multimeter at the 100 Ω range. Measure the thermocouple resistance
first with one polarity, then reverse the polarity. Take the average value. The typical
resistance of the copper wiring is 0.1 Ω/m, for the constantan wiring this is 2.5 Ω/m.
Typical resistance should be the nominal thermocouple resistance of 2.5 Ω plus 2.6 Ωfor
the total resistance of the two wires (back and forth) of each m. Infinite resistance
indicates a broken circuit; zero or a lower than 1 Ω resistance indicates a short circuit.
5. Check if the sensor reacts to heat: put the multimeter at its most sensitive range of
DC voltage measurement, typically the 100 x 10-3 VDC range or lower. Expose the sensor
to heat. Exposing the back side (the side wit the heater) to heat should generate a
positive signal between the red [+] and black [-] wires. Doing the same at the front side
(the side with the dot), reverses the sign of the output.
6. Check the electrical resistance of the heater between any of the yellow wires and any
of the grey wires. Use a multimeter at the 1 kΩ range. Typical resistance should be
around 100 Ω. Infinite resistance indicates a broken circuit; zero or a lower than 1 Ω
resistance indicates a short circuit.
7. Check the electrical resistance between the 2 yellow wires and the 2 brown wires.
These resistances should be in the 0.1 Ω/m range, so 0.2 Ω in case of the standard 2 m
wire length.