Measurements with contact in heat transfer: principles, implementation and pitfalls

International audienceThe main objective of this lecture is to make the end users aware of the various physical phenomena and especially of the errorsfrequently met during temperature and heat flow measurement. Phenomena which occur in thermometry with contact (thermoelectriceffect, thermoresistance...) and without contact (pyrometry with single, two colors or multiwavelength) will be presented. For thermometry with contact, the analysis of systematic errors related to the local disturbance of field temperature due to the introduction of sensors will be emphasized. Indeed intrusive effects due to sensors are usually ignored and can be reduced using know how as will be shown through analytical modeling. Otherwise, interests of using semi intrinsic thermocouples will be discussed. The specificities of temperature measurement in fluid flow and for semi transparent material will be detailed. Finally heat flow measurement using direct methods (gradient, enthalpic, electric dissipation ...) or inverse methods (heat flow sensors with network of thermocouples) will be reminded. This lecture is also dedicated to non contact thermometry. Specificities of radiative methods and procedures to overcome bias in temperature measurement will be discussed. The amount of thermal radiation emitted by a surface is only a fraction of the blackbody radiation at the same temperature. This ratio, i.e. the emissivity, is an additional unknown parameter. Whatever the number of considered wavelengths in passive radiation thermometry, one faces anunderdetermined problem, notwithstanding the fact that the atmosphere between the sensed surface and the sensor introduces itself additional unknown parameters. We will present several solutions (and some pitfalls) for the problem of emissivity and temperature separation developed in the field of multiwavelength pyrometry (MWP) and in the field of multiwavelength/hyperspectral remote sensing of earth