Abstract: The method comprises using thermal flux sensors (4,5,6) to determine the exchange surface <u>A</u> between a reagent (1) and housing (2) containing the above, with the aim of determining the characteristics of the housing (2) and the thermal reaction studied. Said flux sensors (4,5,6) are arranged on the housing (2) in contact and non-contact zones for the above (2) with the reagent (1), such as to continuously determine in real time the precise surface of exchange between the housing (2) and the reagent (1) as a proportion of the measurements taken by each flux sensor (4,5,6) and in such a manner as to determine the thermal exchange coefficient <u>U</u> between the housing (2) and the reagent (1) from the exchange surface <U>A</U> and a measurement of the temperature <u>Tr</u> of the reagent (1) and the wall of the housing (2) respectively, particularly when thermostatted, as in the case of the application to a calorimeter.