Do we really know what temperature is: from Newton’s cooling law to an improved understanding of thermal analysis

Abstract

Temperature is one of the most frequently used physical parameters, commonly measured but not exactly definable under conditions of non-equilibrium. The first part of this article is devoted to a general understanding of temperature and its measurability. In the second part we deal in detail with temperature as the accessible limit, its physical and operational outlook. For extreme cases of rapid temperature changes we propose an alternative temperature term ‘tempericity.’ Regarding the temperature application we suggest four novel branches of optional alternatives of textbook thermodynamics: thermostatics, thermodynamics, thermotics and thermokinetics. The role of heat transfer is discussed within the validity of the Newton’s cooling law and its impact on the sample heat inertia, which became an important part of a constitutive equation of differential thermal analysis. Variability of temperature data is shown as the function of the procedure applied and sensor positioning. This novel understanding is explained by the analysis of a typical thermoanalytical example of a new field of kinetic phase diagrams. Finally, we point out to a possible correlation of the uncertainty principle with the consequence of measured heat and temperature as well as an operational limit of recordability of temperature. The extended discussion of the literature shows the potential and the pivotal role of JTAC journal in finding new approaches leading to better understanding of thermal analysis.