Hukseflux HF01 User manual

Copyright by Hukseflux | manual v1622 | www.hukseflux.com | [e-mail]
USER MANUAL HF01
High temperature heat flux sensor

HF01 manual v1622 2/27
Warning statements
Follow the installation instructions of this user
manual.
The sensor and sensor-to-cable transition should not
be exposed to significant force.
Putting more than 12 Volt across the sensor wiring
can lead to permanent damage to the sensor.
Do not use “open circuit detection” when measuring
the sensor output.
In aluminium production, use the optional silicone
sleeve.
Only for supply with the optional CE type
examination (ATEX) certificate: ask the supplier for
ATEX rated operating conditions.

HF01 manual v1622 3/27
Contents
Warning statements 2
Contents 3
List of symbols 4
Introduction 5
1Ordering and checking at delivery 7
1.1 Ordering HF01 7
1.2 Included items 7
1.3 Quick instrument check 7
2Instrument principle and theory 9
3Specifications of HF01 11
3.2 Dimensions of HF01 14
4Standards and recommended practices for use 15
4.1 Heat flux measurement in industry 15
5Installation of HF01 16
5.1 Site selection and installation in industry 16
5.2 Electrical connection 18
5.3 Requirements for data acquisition / amplification 19
6Maintenance and trouble shooting 20
6.1 Recommended maintenance and quality assurance 20
6.2 Trouble shooting 21
6.3 Calibration and checks in the field 22
7Appendices 24
7.1 Appendix on uncertainty evaluation 24
7.2 Appendix on calibration hierarchy 24
7.3 Appendix on cable extension / replacement 24
7.4 Appendix on magnet replacement 25
7.5 Appendix on recoating/ repainting of sensor surfaces 25
7.6 EU declaration of conformity 26

HF01 manual v1622 4/27
List of symbols
Quantities Symbol Unit
Heat flux ΦW/m²
Voltage output U V
Sensitivity S V/(W/m2)
Temperature T °C
Temperature difference ΔT °C, K
Temperature dependence TD 1/K
Resistance R Ω
Subscripts
property of thermopile sensor sensor
calibration reference condition reference
property of the object on which HF01 is mounted object
property at the (object) surface surface
property of the surrounding environment environment

HF01 manual v1622 5/27
Introduction
HF01 measures heat flux and surface temperature at high temperatures, typically in
industrial environments. It is particularly suitable for trend-monitoring and comparative
testing. HF01 measures heat flux and surface temperature of industrial furnaces, boilers,
fluidised beds, distillation columns and ovens. The sensors inside HF01, a thermopile and
a thermocouple, are protected by fully sealed stainless steel body. It is suitable for long
term use at one location as well as repeated installation when a measuring system is
used at multiple locations.
HF01 measures heat flux through the object on which it is mounted, in W/m2, as well as
its surface temperature in °C. The sensors in HF01 are a thermopile and a type K
thermocouple. The thermopile measures the temperature difference across the body of
HF01, creating an output that is representative of the local heat flux. The thermocouple
measures the absolute temperature of the surface on which HF01 is mounted, as well as
the approximate sensor body temperature. A thermopile and a thermocouple are passive
sensors; they do not require power.
The part of the cabling closest to the sensor is a special high-temperature metal
sheathed cable with an interlocked spiral stainless steel armour. The sensor as well as
the high temperature cable and armour withstand temperatures up to 800 °C.
The temperature range is reduced to 600 °C in case the black coating is used, to 550 °C
in case the frame with magnets is used.
To avoid leakage of current, a risk in aluminium reduction cells, a silicone sleeve is
placed over the metal armour. The low-temperature extension cable has wire insulation
and a jacket of PTFE type plastic. One face of HF01 is painted black, the other is blank
metal.
Using HF01 is easy. It can be connected directly to commonly used data logging systems.
The heat flux, Φ, in W/m2, is calculated by dividing the HF01 output, a small voltage U,
by the sensitivity S, and by applying a linear correction based on the temperature
measurement involving the temperature dependence TD.
The measurement function of HF01 is:
Ф = U/(S∙(1 + TD∙(T - Treference))) (Formula 0.1)
The sensitivity and temperature dependence are provided with HF01 on its product
certificate.
Equipped with heavy duty cabling, and having a fully stainless steel casing so that
moisture does not penetrate the sensor, HF01 has proven to be very reliable. It survives
long-term outdoor installation and repeated installation using the frame with magnets.

HF01 manual v1622 6/27
Figure 0.1 HF01 high temperature heat flux sensor
HF01 is most suitable for relative measurements using one sensor, i.e. monitoring of
trends relative to a certain reference point in time or comparing heat flux at one location
to the heat flux at another location.
In the user wants to perform accurate absolute measurements with HF01, as opposed to
relative measurements, he must make his own uncertainty evaluation and correction for
systematic errors. See the appendix on uncertainty evaluation. However the analysis of
trends is sufficient in many situations. In those cases a high absolute measurement
accuracy is not needed, and a formal uncertainty evaluation is not necessary.
HF01 calibration is traceable to international standards. The factory calibration method
follows the recommended practice of ASTM C1130. The recommended calibration interval
of heat flux sensors is 2 years.
Suggested use of HF01:
•trend-monitoring and comparative measurement of heat flux and surface temperature
in industrial installations
See also:
our complete product range of heat flux sensors
ALUSYS measuring system
HF05 industrial heat flux sensor for lower temperatures up to 170 °C
needle type heat flux sensors NF01 and NF02

HF01 manual v1622 7/27
1Ordering and checking at delivery
1.1 Ordering HF01
The standard configuration of HF01 is with 0.9 m high temperature cable and 3.5 m low
temperature extension cable.
Common options are:
longer cable (specify total cable length for both cable types in m)
frame with magnets
frame with 2 mounting holes (no magnets)
thermocouple type N
sensor and high temperature cable temperature range -180 to + 800 °C
EC type examination certificate (ATEX) II 2 G EEx d IIC T6
connector at HF01 cable end
low temperature extension cable with 2 connectors, matching cable connector and
chassis connector
chassis connector with internal wiring
(colour code of wiring identical to cable colour code)
silicone protection sleeve around the high temperature cable (specify length in m,
standard length 1 m, covering the standard 0.9 m high temperature cable)
1.2 Included items
Arriving at the customer, the delivery should include:
heat flux sensor HF01
cable of the lengths as ordered
product certificate matching the instrument serial number
1.3 Quick instrument check
A quick test of the instrument can be done by connecting it to a multimeter.
1. Check the electrical resistance of the heat flux sensor between the black [-] and red
[+] wires and the thermocouple between the green [+] and white [-] wires. Use a
multimeter at the 100 Ω range. Measure the sensor resistance first with one polarity,
then reverse the polarity. Take the average value. Typical resistance should be the
nominal sensor resistance of 10 to 30 Ω for the thermopile sensor at standard cable
lengths, plus for additional low temperature extension cable 0.2 Ω/m (resistance per
meter cable ) for the total resistance of two wires (back and forth added), for high
temperature cable 13 Ω/m. For the thermocouple work with 10 to 50 Ω at standard cable
lengths, plus additional low temperature extension cable 3 Ω/m resistance per meter
cable ), for high temperature cable 28 Ω/m. Infinite resistance indicates a broken circuit;
zero or a lower than 1 Ω resistance indicates a short circuit.

HF01 manual v1622 8/27
2. Check if the heat flux 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 heat, for instance touching it with your hand. The signal should
read > 2 x 10-3 V now. Touching or exposing the black side should generate a positive
signal, doing the same at the opposite side, the sign of the output voltage reverses. Also
look at the reaction of the thermocouple to heat. The thermocouple is located at the
blank metal side of the sensor.
3. Inspect the instrument for any damage.
4. Check the sensor serial number engraved on the transition piece between high
temperature cable and low temperature extension cable, against the certificate provided
with the sensor.

HF01 manual v1622 9/27
2Instrument principle and theory
HF01’s scientific name is heat flux sensor. A heat flux sensor measures the heat flux
density through the sensor itself. This quantity, expressed in W/m2, is usually called
“heat flux”. HF01 users typically assume that the measured heat flux is representative of
the undisturbed heat flux at the location of the sensor. Users may also apply corrections
based on scientific judgement.
The heat flux sensor in HF01 is a thermopile. This thermopile measures the temperature
difference across the body of HF01. Working completely passive, the thermopile
generates a small voltage that is a linear function of this temperature difference. The
heat flux is proportional to the same temperature difference divided by the effective
thermal conductivity of the heat flux sensor body.
Using HF01 is easy. For readout the user only needs an accurate voltmeter that works in
the millivolt range. To convert the measured voltage, U, to a heat flux Φ, the voltage
must be divided by the sensitivity S, a constant that is supplied with each individual
sensor, and correct for the temperature of the sensor.
The temperature sensor inside HF01 is a type K thermocouple located at the blank metal
side of the sensor.
Figure 2.1 The general working principle of a heat flux sensor. The sensor inside HF01 is
a thermopile. A thermopile consists of a number of thermocouples, each consisting of two
metal alloys marked 1 and 2, electrically connected in series. A single thermocouple will
generate an output voltage that is proportional to the temperature difference between its
hot- and cold joints. Putting thermocouples in series amplifies the signal. In a heat flux
sensor, the hot- and cold joints are located at the opposite sensor surfaces 4 and 5. In
steady state, the heat flux 6 is a linear function of the temperature difference across the
sensor and the average thermal conductivity of the sensor body, 3. The thermopile
generates a voltage output proportional to the heat flux through the sensor.
The exact sensitivity of the sensor is determined at the manufacturer by calibration, and
is found on the calibration certificate that is supplied with each sensor.
5
4
321
6

HF01 manual v1622 10/27
Heat flux sensors such as HF01, for use in industry at high heat flux levels, are typically
calibrated under the following reference conditions:
conductive heat flux (as opposed to radiative or convective heat flux)
homogeneous heat flux across the sensor and guard surface
room temperature
heat flux in the order of 1500 W/m2
Unique features of HF01 are:
low electrical resistance (low pickup of electrical noise)
high sensitivity (good signal to noise ratio in low-flux environments such as
buildings)
robustness, including a strong cable
built-in temperature sensor; type K thermocouple
IP protection class: IP68 for sensor and high temperature cable
Measuring with heat flux sensors, errors may be caused by differences between
calibration reference conditions and the conditions during use. The user should analyse
his own experiment and make his own uncertainty evaluation.
Figure 2.2 Heat flux sensor model HF01 with optional frame with magnets (2),
connected to a high- temperature metal sheathed cable with interlocked spiral stainless
steel armour (4) and low-temperature extension cable (6). The frame (1) with magnets
(7) is an option intended for temporary mounting on carbon steel walls. It is provided
with a cable strain relief (3). The armour may be electrically insulated by a silicone
sleeve (5). Dimensions are in x 10-3 m.
7
ø 25
90
40
HF01 SN xxxx
5421 63
2
1
2
3
4

HF01 manual v1622 11/27
3Specifications of HF01
HF01 measures the heat flux density through the surface of the sensor. This quantity,
expressed in W/m2, is called heat flux. It also measures the absolute temperature of the
surface on which it is mounted. HF01 is passive, using thermopile and thermocouple
sensors. The thermopile generates a small output voltage proportional to the heat flux.
HF01 can only be used in combination with a suitable measurement system.
Table 3.1 Specifications of HF01 (continued on next page)
HF01 SPECIFICATIONS
Sensor type
high temperature heat flux sensor
Sensor type according to ASTM
heat flow sensor or heat flux transducer
Heat flux sensor
thermopile
Measurand
heat flux
Measurand in SI units
heat flux density in W/m2
Measurement range
-50 to 50 x 103W/m2
Temperature sensor
thermocouple type K
Temperature sensor specification
ANSI MC96.1-1982 / EN 60584
Measurand
temperature
Measurand in SI units
temperature in °C
Measurement function / required
programming
Ф= U/(S∙(1 + TD∙(T - Treference)))
Recommended number of sensors
2 per measurement location
Sensitivity (nominal)
0.5 x 10-6 V/(W/m2)
Response time (95 %)
300 s (depends on the thermal contact resistance)
Directional sensitivity
heat flux from black painted side to the opposite blank
metal side generates a positive voltage output signal
Expected voltage output
multiply the sensitivity by the maximum expected
heat flux
Required readout
heat flux sensor: 1 x differential voltage channel or 1
x single ended voltage channel
temperature sensor: 1 x Type K differential
thermocouple channel or 1 x Type K single ended
thermocouple channel
both with input resistance > 106Ω
Rated operating temperature ranges:
sensor and high temperature cable
black coating
optional frame with magnets
low temperature extension cable
optional connectors
optional silicone protection sleeve
-30 to +800 °C
-30 to +600 °C
-30 to +550 °C
-30 to +240 °C
-50 to +250 °C
-60 to +250 °C
IP protection class
Sensor and high temperature cable
Low temperature extension cable
IP68
IP67
Rated operating relative humidity range
0 to 100 %
Required sensor power
zero (passive sensors)
Temperature dependence TD
+ 0.0015 1/K
Non-stability
< 1 %/yr (for typical use)
Sensor diameter
25 x 10-3 m
Sensor thickness
6.0 x 10-3 m
Sensor thermal resistance
4.2 x 10-3 K/(W/m2)
Sensor thermal conductivity
1.4 W/(m·K) (nominal)

HF01 manual v1622 12/27
Table 3.1 Specifications of HF01 (started on previous page, continued on the next page)
Standard cable lengths
High temperature cable
Low temperature extension cable
0.9 m (see options)
3.5 m (see options)
Heat flux sensor resistance range
10 to 30 Ω (standard cable length)
Low temperature extension cable: heat
flux sensor cable resistance
0.2 Ω/m (nominal)
High temperature cable: heat flux sensor
cable resistance
13 Ω/m (nominal)
Temperature sensor resistance range
10 to 50 Ω (standard cable length)
Low temperature extension cable:
temperature sensor cable resistance
3 Ω/m (nominal)
High temperature cable: temperature
sensor cable resistance
28 Ω/m (nominal)
Black coating emissivity
0.92 (nominal)
High temperature metal interlocked
spiral armour diameter
5 x 10-3 m
Low temperature extension cable
diameter
4 x 10-3 m
Transition piece diameter
10 x 10-3 m
Marking
1 x engraving on the transition piece, showing serial
number
1 x sticker at low temperature extension cable end,
showing serial number.
Gross weight including 0.9 and 3.5 m
cable
0.75
Net weight including 0.9 and 3.5 m cable
0.60 kg
Packaging
plastic case of 160 x 220 x 50 mm
INSTALLATION AND USE
Standards governing use of the
instrument
N/A
Orientation
the blank metal side usually is in contact with the
object. In case the sensor embedded in the object,
there is no preferred orientation.
Installation
see recommendations in this user manual
avoid mechanical force on the sensor body and
sensor-to-cable transition.
make user there is good thermal contact between
sensor and object.
in aluminium production , use the silicone protection
sleeve
Cable extension
see options: longer cable, extention cable and
connectors
Optional connectors on HF01 cable and
extension cable
LEMO brand, 12 x 10-3 m outer diameter
Recoating
the black surface may be recoated with high
temperature black paint, see the appendix on this
subject

HF01 manual v1622 13/27
Table 3.1 Specifications of HF01 (started on previous 2 pages)
CALIBRATION
Calibration traceability
to SI units
Product certificate
included
(showing calibration result and traceability)
Calibration method
method HFC, according to ASTM C1130
Calibration hierarchy
from SI through international standards and through
an internal mathematical procedure
Calibration uncertainty
< 20 % (k = 2)
Recommended recalibration interval
2 years
Calibration reference conditions
90 °C, heat flux of 1500 W/m2, thermal conductivity
of the surrounding environment 0.0 W/(m·K)
Validity of calibration
based on experience the instrument sensitivity will not
change during storage. During use the instrument
“non-stability” specification is applicable.
Field calibration
is possible by comparison to a calibration reference
sensor. Usually mounted side by side. Preferably
reference and field sensor of the same model and
brand. Typical duration of test > 24 h.
Temperature sensor tolerance class
IEC Tolerance class EN60584-2: Type K, class 2
Temperature sensor error limits
ASTM E230-ANSI MC96.1: Type K, standard limits
MEASUREMENT ACCURACY
Uncertainty of the measurement
statements about the overall measurement
uncertainty can only be made on an individual basis.
see the chapter on uncertainty evaluation.
VERSIONS / OPTIONS
Order code
HF01 / high temperature cable length in m /
low temperature extension cable length in m
Longer cable
longer cable (specify total cable length for both cable
types in m)
Frame with magnets
frame with magnets and silicone sleeve
Frame with 2 mounting holes
frame with 2 mounting holes (no magnets)
Thermocouple type N
thermocouple type N
EC type examination certificate (ATEX)
II 2 G EEx d IIC T6
Extended temperature range
sensor and high temperature cable temperature range
-180 to + 800 °C
Connector
connector at HF01 cable end
Extension cable
low temperature extension cable with 2 connectors
with 2 connectors matching cable connector and
chassis connector (specify cable length in m)
Silicone sleeve
silicone protection sleeve around the high temperature
cable (specify length in m, standard length 1 m,
covering the standard 0.9 m high temperature cable)
Chassis connector
chassis connector with internal wiring
(colour code of wiring identical to cable colour code)
SPARE PARTS
Magnets
set of 10 magnets for HF01

HF01 manual v1622 14/27
3.2 Dimensions of HF01
Figure 3.2.1 HF01 heat flux sensor with optional frame with magnets.
Dimensions in x 10-3 m.
7
ø 25
90
40
HF01 SN xxxx
5421 63
2
1
2
3
4

HF01 manual v1622 15/27
4Standards and recommended practices
for use
Use of HF01 is not subject to standardised operating procedures.
4.1 Heat flux measurement in industry
Many HF01 sensors measure on industrial walls and metal surfaces, estimating the
installation’s energy balance. Typically the total measuring system consists of multiple
heat flux- and temperature sensors. In many cases heat flux sensors are used for trend-
monitoring. In such cases reproducibility is more important than absolute measurement
accuracy.
Figure 4.1.1 Industrial heat flux sensor mounted on a boiler wall using tack-welded
threads and spring-loaded bolts. The sensor is mounted on a well prepared flat surface.
Cabling must be provided with strain relief.

HF01 manual v1622 16/27
5Installation of HF01
5.1 Site selection and installation in industry
Table 5.1.1 Recommendations for installation of HF01 heat flux sensors
Location
Choose a location that is representative of the process that is analysed
if possible, avoid exposure to sun, rain, etc.
Do not expose to drafts and lateral heat fluxes
Do not mount in the vicinity of thermal bridges, cracks, heating or cooling
devices and fans
Performing a
representative
measurement /
recommended
number of sensors
We recommend using > 2 sensors per measurement location. This
redundancy also improves the assessment of the measurement accuracy
Orientation
Mounted on vertical surfaces, the cable exit from the sensor should point
down.
Surface cleaning and
levelling
Minimise any thermal contact resistance between sensor and object.
Create a clean and smooth surface with a diameter of 0.1 m, so that the
air gap between sensor and object surface is less than 0.2 x 10-3 m
Mechanical mounting:
avoiding strain on the
sensor to cable
transition
The sensor-to-cable transition is vulnerable.
During installation as well as operation, the user should provide proper
strain relief of the cable so that transition is not exposed to significant
force.
For permanent mooning: first install the cable including strain relief and
after that install the sensor.
Mechanical mounting:
The sensor body withstands only limited pressure and strain.
Users should not exert significant mechanical force on the sensor or on
the sensor to cable transition.
Permanent
installation
For permanent mounting using the metal frame with 2 holes: tack-weld
or screw M6 thread to the surface on which HF01 is mounted at a hart-to-
hart distance of 60 x10-3 m. Bolts holding the sensor should be used for
positioning and for loose fixation only, and should be spring- loaded to
guarantee good sensor to surface contact without exerting too much
force.
If the temperature remains below 240 °C, for long-term installation fill up
the space between sensor and object with silicone construction sealant,
silicone glue or silicone adhesive, that can be bought in construction
depots. Use this in combination with the spring-loaded threads.
Short term
installation
In case the object surface is magnetic: use the optional frame with
magnets.
Consider filling up air gaps with thermal paste.
Signal amplification
See the paragraph on electrical connection.

HF01 manual v1622 17/27
Figure 5.1.1 Permanent installation of HF01 with frame. The HF01 sensor (2) has a
frame (4) with 2 holes (3). For permanent mounting, using the metal frame with 2 holes,
tack-weld or screw M6 thread to the surface on which HF01 is mounted at a hart-to-hart
distance of 60 x10-3 m. Bolts holding the sensor should be used for positioning and for
loose fixation only, and should be spring- loaded to guarantee good sensor to surface
contact without exerting too much force.
21
23 4
1
3
2
4

HF01 manual v1622 18/27
5.2 Electrical connection
A heat flux sensor should be connected to a measurement system, typically a so-called
datalogger. HF01 is a passive sensor that does not need any power, neither for the heat
flux sensor, nor for the temperature sensor. Cables may act as a source of distortion, by
picking up capacitive noise. We recommend keeping the distance between a datalogger
or amplifier and the sensor as short as possible. For cable extension, see the appendix on
this subject.
Table 5.2.1The electrical connection of HF01. The shield is not connected to the
stainless steel sensor body
WIRE
Red
heat flux signal [+]
Black
heat flux signal [−]
Green
thermocouple type K [+]
White
thermocouple type K [−]
Blank
shield

HF01 manual v1622 19/27
5.3 Requirements for data acquisition / amplification
The selection and programming of dataloggers is the responsibility of the user. Please
contact the supplier of the data acquisition and amplification equipment to see if
directions for use with the HF01 are available.
Table 5.3.1 Requirements for data acquisition and amplification equipment for HF01 in
the standard configuration
Capability to measure small voltage
signals
preferably: < 5 x 10-6 V uncertainty
Minimum requirement: 20 x 10-6 V uncertainty
(valid for the entire expected temperature range of the
acquisition / amplification equipment)
Capability for the data logger or the
software
to store data, and to perform division by the sensitivity to
calculate the heat flux.
Ф = U/(S∙(1 + TD∙(T - Treference))) (Formula 0.1)
Capability to measure thermocouple
type K
preferably: measurement uncertainty within ± 3 °C
Data acquisition input resistance
> 1 x 106Ω
Open circuit detection
(WARNING)
open-circuit detection should not be used, unless this is done
separately from the normal measurement by more than 5
times the sensor response time and with a small current
only. Thermopile and thermocouple sensors are sensitive to
the current that is used during open circuit detection. The
current will generate heat, which is measured and will
appear as a temporary offset.

HF01 manual v1622 20/27
6Maintenance and trouble shooting
6.1 Recommended maintenance and quality assurance
HF01 measures reliably at a low level of maintenance. Unreliable measurement results
are detected by scientific judgement, for example by looking for unreasonably large or
small measured values. The preferred way to obtain a reliable measurement is a regular
critical review of the measured data, preferably checking against other measurements.
Table 6.1.1 Recommended maintenance of HF01. If possible the data analysis is done
on a daily basis.
MINIMUM RECOMMENDED HEAT FLUX SENSOR MAINTENANCE
INTERVAL
SUBJECT
ACTION
1
1 week
data analysis
compare measured data to the maximum possible or
maximum expected heat flux and to other measurements for
example from nearby or redundant instruments. Historical
seasonal records can be used as a source for expected values.
Look for any patterns and events that deviate from what is
normal or expected. Compare to acceptance intervals.
2
6 months
inspection
inspect cable quality, inspect mounting, inspect location of
installation
look for seasonal patterns in measurement data
3
2 years
recalibration
recalibration by comparison to a calibration standard
instrument in the field, see following paragraphs.
recalibration by the sensor manufacturer
4
lifetime
assessment
judge if the instrument will be reliable for another 2 years, or
if it should be replaced