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Heat Flux Sensors Help Reduce Energy

Use of heat flux sensors in monitoring heat energy loss

A heat flux sensor measures the heat transfer (loss or gain) through a surface. The sensor produces an output that is proportional to the heat flux (Watts/cm2) experienced by the sensor (the heat energy flowing through it). This heat flux can be convective, radiative or conductive and all three can be measured using varying forms of heat flux sensor. Heat flux sensors are known under different names, such as transducers, gauges, plates. In addition there are several styles of heat flux sensor that are single-purpose sensors such as pyrometers (for solar radiation measurement) and Schmidt Boelter gauges (for measurement of heat flux from fire). Heat flux is commonly measured in KWatts per square metre or watts per square centimetre.

Common uses for heat flux sensors:

Heat flux sensors can be used for a variety of applications, typically studies of building insulation and thermal resistance, studies of the effect of fire and flames or heat applied in food preparation conveyor ovens. More extreme applications include monitoring of boiler lining surfaces, flame front profiles in internal combustion engines and rocket motors.

The total heat flux is composed of a conductive, convective and radiative part. Depending on the application, one or more may be required to be measured. An example of measurement of conductive heat flux is a heat flux plate incorporated into a wall.

An example of measurement of radiative heat flux is a pyrometer for measurement of solar radiation. An example of a sensor sensitive to radiative as well as convective heat flux is a Gardon or Schmidt Boelter gauge, used for studies of fire and flames.

Some examples of where Heat Flux is used:

  • In general heat energy transfer is a precursor to temperature going up (or down). Therefore if your application is to control the temperature inside an oven, measuring heat flux will warn you of the temperature the oven is likely to reach in future, allowing a more stable control.
  • Heat Conductivity: If you are trying to establish how good your wall is in keeping temperature inside a building, measuring temperature outside and inside the building will only give half the story, as the temperature outside is dependent on the environment. Heat Flux measurement will give an accurate reading of the heat that is being passed through the wall.
  • In agriculture thermal properties of soil changes as water is absorbed by and then evaporates from the soil. Heat Flux is used to measure the thermal property of soil.
  • Clothing: Measurement of heat transfer properties of material worn by fire rescuers, divers and climbers, will enable the manufacturer to produce materials best suited to the protection of the wearers of these types of clothing.

Typical Heat flux and radiation applications are:

  • Heat energy through walls, roofs and floors of buildings to establish insulation properties of materials, efficient control of heating / cooling.
  • Heat flux through soil for agricultural applications
  • Heat flux from living beings to their surroundings for medical projects - Urology and diabetes issues can be sensed using heat flux techniques.
  • Solar radiation for optimal control of solar collectors.
  • Heat radiation of ovens for optimization of process conditions.
  • Mass flow in pipes.
  • Thermal properties of materials
  • Thermal conductivity - for thermal properties of materials

Heat Flux Sensors are the ideal medium through which heat energy transfer can be measured, as they can operate at low, as well as very high temperatures and give an accurate understanding of the heat properties of the material or the environment being tested. They are easy to use, are fully calibrated and save cost.,3