Bonnes pratiques pour la mise en œuvre des mesures de températures de surface
Good practices for the implementation of surface temperature measurements
Centre Technique des Industries Aérauliques et Thermiques (CETIAT), 25 Av. des Arts, 69603 Villeurbanne, France
a Corresponding author: firstname.lastname@example.org
This paper presents physical principles involved and main errors encountered when performing surface temperature measurements, in contact thermometry. Two concepts are defined: direct temperature measurements where the objective is to evaluate the surface temperature that prevailed prior to the application of the sensor and indirect measurements using surface sensors to assess, for example, the internal temperature of a fluid flowing in a pipe or within a wall. It is important to define the quantity of interest, i.e. the measurand, because the same sensor can be used but implemented differently. For example, for direct measurement, sensors can be calibrated on surface temperature calibrator and should be applied directly on the surface that should be measured. Whereas, for indirect measurements, improving the thermal contact can be achieved by using a thermal dough or sensor insulation and calibration should be realized on site. To illustrate these situations and these phenomena, various measurements of industrial surface temperature are provided. For example, it is important, in an industrial mixing process, to control the mixer surface temperature to ensure the quality of the finished mixed product. The temperature of the machine housings has also to be controlled to prevent the risk of burns. Energy audits can also be based on such measures. Surface temperature sensors are more and more present in the controls of heating and air-conditioning systems such as heat pumps, boilers ... Surface temperature often help saving time during manufacturing and during maintenance operations. Over the past decade, the performances of such sensors has been much improved.
This article outlines the precautions and best practices for implementation of the contact temperature sensors. The environmental effects are studied in order to quantify the impact on the measurements. The concepts developed by Bardon, Cassagne and Sacadura are used to explain the effects present at the interface. The effects of an air flow, the radiation, thermal conductivity of the wall, the fixing system of the sensor are studied for an optimal implementation of relevant solutions. The paper offers an overview of current implementations techniques and possible performance levels.
© Owned by the authors, published by EDP Sciences, 2015
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