Heat Transfer in Building - How to Properly Install a Heat Flux Sensor

Measuring heat flux is a valuable method for understanding various processes better than just measuring temperature, such as assessing heat flow through walls or cooling specimens. However, achieving accurate and stable heat flux measurements necessitates the correct installation of the appropriate sensor.

Heat flux sensors are a powerful tool for understanding various thermal processes. They have a wide range of applications, together with temperature measurements, from performance analysis of thermal insulation to monitoring of fouling of pipelines and even the health of pigs. Measuring heat flux, basically upgrading your temperature measurement, can provide important insight into thermal processes and system performance.

However, ensuring accurate data requires the use of an appropriate sensor and mounting it correctly to perform stable measurements of both radiative and convective heat flux. This critical step ensures the acquisition of accurate data.

Figure 1. FHF05SC-85X85 heat flux sensor mounted on a wall, using silicone glue. Image Credit: Hukseflux Thermal Sensors B.V.

General Considerations for Heat Flux Measurement

It is vital to ensure the appropriate sensor is employed for the system of interest. Many different models are available with various temperature and heat flux ranges.

It is also crucial to perform a representative measurement. The sensor must be placed at a location representative of the system to be monitored and multiple sensors may be employed to provide an average flux. The representativeness of data can be reviewed using infrared cameras.

Installation Considerations

Regardless of the heat flux sensor type, secure mounting is important to avoid variations in contact resistance between the sensor and the object of interest.

Air gaps between the sensor and the object may cause significant thermal resistance and increase response time. As such, air gaps should be avoided.

Sensors can also gradually become loose, producing unreliable measurements. To prevent this, a stable glue or filler and high-quality cabling and strain relief should be utilized.

Attention must be paid to the sensor surface's optical properties, which should match those of the object the sensor is mounted on.

Mounting

The mounting of a heat flux sensor varies depending on the application.

varies depending on the application. Two key parameters to consider before deciding on a mounting solution are: temperature range and the duration of measurement. These two parameters will aid in selecting the appropriate mounting solution for the heat flux sensor.

Table 1 and the examples at the end of this article will help when it comes to reviewing your options.

Always ensure strain relief on the cable to avoid unnecessary stress on the sensor.

Table 1. Options for mounting heat flux sensors. Materials may act to fix the sensor position, but also to fill up airgaps. Source: Hukseflux Thermal Sensors B.V.

This information has been sourced, reviewed and adapted from materials provided by Hukseflux Thermal Sensors B.V.

If you would like to have more information about heat flux measurements and heat flux sensors, please contact Hukseflux