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Enabling better global research outcomes in soil, plant & environmental monitoring.

Hukseflux NF01 Heat Flux Sensor

The NF01 needle type heat flux and temperature sensor is used for monitoring in high temperature environments, typically in walls and shells of blast furnaces and smelters. Measuring heat flux as well as temperature with one sensor is more accurate and practical than using distributed temperature measurements. The same technology is used to manufacture heat flux sensors for different applications.

Suggested use

  • trend monitoring of heat flux in industrial installations
  • detection of emergencies
  • energy efficiency studies

NF01 is used for monitoring heat flux and temperature in high temperature environments

NF01 is used for measurement of the energy balance of industrial blast furnaces and smelters, in steel shells as well as in the graphite and brick refractory. It has been applied successfully in iron furnace emergency response systems and in smelters for titania slag production. The sensors inside NF01, a thermopile and a thermocouple, are protected by a fully sealed stainless steel “needle” body. The needle can withstand temperatures up to 700°C, as well as the aggressive chemical environment of a furnace. Optionally the sensor temperature range can be extended to 1000°C. The cable is made of PVC. The sensor outputs are heat flux, an analogue voltage signal in the millivolt range, and temperature using a thermocouple type K. The user must know the thermal conductivity of the surrounding material to calculate the heat flux.


The usual approach to measurement of heat flux is to estimate it from distributed temperature measurements. This leads to large measurement errors and is not practical.

  • NF01 creates a single temperature difference signal. This is much more accurate than calculating a heat flux by subtracting two individual temperature measurements
  • NF01 sensors can be quickly installed; contrary to spatially distributed temperature sensors, the relative position of the sensors used for the temperature difference measurement is already determined during manufacturing. The exact depth of insertion is not a critical factor determining the accuracy of this relative position. Installation can be done quickly with little training
  • NF01 sensors are fully exchangeable. Contrary to spatially distributed temperature sensors, the sensors in the NF01 are “matched pairs”. This is essential to attain the best possible temperature difference measurement
  • NF01 has a fast heat flux response time: the high accuracy makes it possible to measure a temperature difference across a small distance
  • NF01 is durable; the swaged thick-wall needle lasts longer than normal sensors
Measurand: heat flux temperature
Measurement range: 0.05 to 50 x10³ W/m² (typical)
Sensitivity (nominal): 2 x10⁻⁶ V•m/K
Heat flux sensor: thermopile
Temperature sensor: thermocouple type K
Needle length: specified by the user
Needle diameter: 8 x10⁻³ m
Needle diameter optional: 4 x10⁻³ m
Sensor design: swaged SS 310 sheath
Rated measurement range: 0.05 to 50 x10³ W/m² (typical)
Rated Operating Temperature Range:
-Sensor: -30 to +700°C
-Sensor optional: -30 to +1000°C
-Cable: -30 to +85°C
Standard cable length: 10 m (see options)
Design: user-specific: in cooperation with the user for the specific application
Installation: see the manual for recommended parts for installation
  • longer cable (specify total cable length in m)
  • 4 x 10⁻³ m needle diameter
  • wire cladding colour codes according to ANSI
  • needle lengths (specify NL)
  • needle rated operating temperature range up to 1000°C