FR3007133A1 - DEVICE AND METHOD FOR DIFFERENTIALLY THERMAL AND CALORIMETRIC ANALYSIS OF SAMPLE VOLUMES FOR THE THERMODYNAMIC CHARACTERIZATION OF PHASE CHANGE MATERIALS - Google Patents

Abstract

The present invention relates to the field of thermal analysis and calorimetry, that is to say the measurement of heat amounts, and more particularly to the field of differential calorimetry for measuring and comparing the heat exchange between a sample to study and a known reference. The invention makes it possible to perform this type of measurement accurately and reproducibly on samples in any type of state, stable or metastable, in particular samples of phase change materials and having a large volume.

Description

Apparatus and method for differential thermal and calorimetric analysis of large volume samples for the thermodynamic characterization of phase change materials TECHNICAL FIELD OF THE INVENTION The present invention relates to the field of thermal and calorimetric analysis methods, that is to say the measurement of transformation temperatures and relative amounts of heat, and more particularly to the field of differential calorimetry allowing to measure and compare, for a given heating or cooling, the heat exchanges between a sample to be studied and a known reference with the source or the heat sink. The invention makes it possible to perform this type of measurement accurately and reproducibly on samples of unconventional size and in any type of state, stable or metastable. BACKGROUND OF THE INVENTION In a manner known per se, a calorimeter is a system for measuring thermal effects in order to determine the quantities of heat exchanged, in particular with a sample made of a material with phase change (in English Phase Change Material or PCM) to study. The thermal effects are detectable on macroscopic samples only in a state of non-thermal equilibrium. Indeed, a phase change can not be achieved at equilibrium because it is necessary to bring energy and thus create a thermal gradient. However, one of the problems of industrial devices is the precise and reproducible evaluation of the heat exchanges, in particular with the aim of studying the physical and chemical transformations of the samples, for example, made of a phase-change material tested, accompanied by heat exchange between a sample and the calorimeter. Some of these solutions are disclosed below. Many documents disclose systems for performing measurements on unconventional size samples, as described for example in US 5,135,311. This document discloses a calorimetric enclosure of several cubic meters, such a chamber being rendered adiabatic to allow the study of heat exchanges between a living being and the enclosure in which the latter is disposed.

However, it is not a matter of differential calorimetry, since there is no reference measuring chamber. On the other hand, this calorimeter was designed to measure the heat loss of living beings, and is therefore not suitable for the study of heat exchange during the changes of states of the industrial samples involved in our application.

Document US 2010 / 0,255,588 discloses a calorimeter that can contain large volume samples, typically several hundred milliliters. It is not a matter of differential calorimetry, since only one measuring chamber is necessary. Moreover, the features highlighted in this document concern the possibility of effectively regulating the temperature inside the calorimetric compartment (s), and not for measuring the heat exchanges during the changes of states of the industrial samples involved in our analysis. application. The document FR 2,717,900 describes a differential calorimeter, comprising a measurement chamber and a reference chamber and which makes it possible to measure the amount of heat evolved or absorbed by a sample of several hundred kilograms contained in a large container up to to several hundred liters. But again, the document provides no information as to the study of the phase transitions of the sample itself.

Moreover, the state of the art describes numerous devices and methods whose purpose is to improve the accuracy of temperature measurements in the vicinity of the points of change of state. Indeed, measurements in these particular areas of temperature for a sample near a phase change, (solid-solid, solid-liquid, solid-gas, liquid-gas for the main ones) are particularly difficult to perform because seat brutal variations of the physicochemical variables. It should be noted that the calorimetric temperature measurement of a change of state of a micro-sample is a very developed area in science. Document US 2002 / 0,098,593 discloses a differential calorimetry thermal analysis device, including optical measuring tools and a method which greatly reduce inaccuracies in the context of heat exchange measurements obtained by conventional differential calorimetry. The document describes a calorimeter comprising a multitude of measuring speakers, which allows measurements on several samples of the same nature simultaneously. The purpose of the device and method described is the reduction of measurement inaccuracies. However, the use of a multitude of speakers does not allow in this case to study samples of large volume. Another document which deals with the precise measurement of the determination of these points of change of state is the document US 2007 / 0,242,722 which proposes in particular a method and a device making it possible to perform differential calorimetry on various samples. The calorimeter comprises a measurement chamber and a reference chamber, each connected to a temperature probe and partially in contact with a temperature-controlled metal structure. However, to have a better measurement accuracy with a relatively short measurement time, the samples to be tested are small in the order of 5 mm3. In this document, it is proposed to accurately measure the freezing point of a small sample of phase change material (CPM) to be tested in the liquid state to establish the temperature / enthalpy relationship determining the heat storage capacity. However, to limit the uncertainty of the calorimetric measurement, the method uses the principle of heating and cooling in stages and requires a thorough numerical analysis, based on the extrapolation of data obtained by conventional differential calorimetry. Indeed, the method proposes to draw tangents to the temperature curve of the sample, to deduce the phase changes corresponding to the temperature at which the freezing of the sample takes place, from the temperature difference between the sample. reference and the sample to be tested. The method therefore offers an indirect value of this freezing temperature. Ultimately, this method requires sophisticated processing, evaluation and data representation.

GENERAL DESCRIPTION OF THE INVENTION The object of the present invention is to remedy all or some of the disadvantages mentioned above. It aims to propose a new device and a new process which, related to the principle of the classical differential calorimetry, ensures the precise quantification of heat exchanges between one or more samples of unconventional size and the other parts of the calorimeter, whatever the state of the sample (s), stable or metastable. To this end, the invention relates to a device for differential thermal and calorimetric analysis of a test sample, in particular of a phase-change material in a measurement interval, comprising: a reservoir in which are disposed at at least two identical enclosures, a so-called reference chamber filled with a reference material and at least one measurement chamber comprising the sample to be tested, a temperature measuring device associated with each chamber, acquisition means and data processing apparatus for delivering, as a function of time, differential signals representative of the temperature difference between said at least two enclosures to derive a characteristic temperature, in particular the phase change temperature, of the sample to be tested, said analysis device being characterized in that: - it comprises means of heating and / or cooling, for tr ansmettre said at least two speakers a working temperature in the measurement interval, the tank being filled with a heat transfer fluid that can be subjected to at least a predetermined thermal setpoint to regulate it, said at least two enclosures being totally immersed in said fluid during the differential analysis, - it comprises a device for measuring the heat flux associated with each enclosure so that the differential signals delivered are also a function of the difference between the thermal flows passing through said at least two enclosures, The thermal and calorimetric analysis device of the invention is particularly intended for analyzes where the sample is a phase-change material and / or where the volume of the samples to be tested is large and consistent with the industrial volumes. Thus, the system described in the invention makes it possible to perform accurate and reproducible measurements of heat amounts by conventional differential calorimetry with measuring chambers 100 to 1000 times larger than the measuring chambers of conventional calorimeters. According to another feature, the thermal and calorimetric analysis device of the invention is characterized in that the volume ratio between the chambers and the heat transfer fluid ensures a stability of the characteristic temperature of the sample to be tested, such as that the temperature during phase changes of this sample, lower than 0.1 ° C. Advantageously, the volume ratio is such that the volume of the heat transfer fluid contained in the reservoir is at least greater than two and a half times the total volume occupied by said at least two measuring chambers.

Additional features may be provided for the differential thermal and calorimetric analysis device of the invention, such that: - each of said at least two enclosures has an internal volume of at least 50 milliliters; means for circulating the thermal transfer fluid in closed circuit may be provided and be associated with means for controlling the circulation of the heat transfer fluid; said at least two enclosures are sealed and the measuring chamber is provided with an opening and closing system for sealingly introducing the sample to be tested and maintaining it in a leak-proof manner; screw from the outside environment; the reservoir containing the heat transfer fluid may be hermetic; at least one measurement chamber is connected on the one hand to a reservoir containing the sample to be tested in the liquid phase, and on the other hand to a reservoir containing a gas under a pressure greater than the internal pressure of the chamber; flow of the sample to be measured or pressurized gas tanks to the measuring chamber being provided by means of communication of the measuring chamber respectively with the reservoir containing the sample and the compressed gas reservoir. Thus, the system can be better isolated from the outside environment, also permitting measurements over a wide range of pressures and temperatures. On the other hand, it is possible to load samples in the liquid phase without extracting the measuring chambers from the heat transfer fluid; - The tank is equipped with a purge system for emptying and replacement of the heat transfer fluid with a fluid adapted to the temperature ranges necessary for the study of phase changes of the sample to be tested. Thus, it is easy to adapt the thermodynamic properties of the heat transfer fluid as a function of the pressure and temperature parameters during the measurements; the temperature regulation of the heat transfer fluid is ensured by thermo-resistances whose power is regulated by at least one PID regulator, and the temperature of said fluid is measured by a temperature probe and / or a refrigeration unit integrated in the circulation means of the heat transfer fluid. This may be useful for effectively maintaining the thermal equilibrium of the heat transfer fluid at the chosen temperature, or for working at temperatures below the temperature of the external environment; the measurement chambers consist of a good thermal conductive material, preferably aluminum, copper, silver or metal alloys and / or the reference material may be air, sapphire, alumina, water, oil , and preferably air; A further object of the invention is to provide a method of thermal analysis and calorimetry.

This method has the particularity of being a method of differential and quantitative thermal and calorimetric analysis of a sample to be tested, a method being implemented by a differential thermal and calorimetric analysis device according to the characteristics of said analysis device. This method is characterized in that it comprises the following steps: a step of placing the sample to be tested in at least one measuring chamber, different from the reference chamber, and being totally immersed in a fluid thermal transfer step, a thermal equilibrium step, at an initial temperature remote from the phase change temperature, of all the parts of the device, and circulation of the fluid, a step of choice and applying at least one thermal setpoint to the heat transfer fluid, associated with triggering the acquisition and storage in memory of the temperature and heat flow data of each measuring chamber subjected to these same thermal instructions, a step of correlating the temperature and heat flux data obtained in each chamber and comparing the results between the reference chamber and at least one chamber measurement, by the processing means and the software assembly so as to have a data directly representative of the change of state temperature of the sample to be tested.

The enclosures used have an internal volume of at least 50 milliliters. The method may furthermore comprise the following steps: a step of placing at least one sample in at least one measuring chamber, different from the enclosure of reference, the enclosures being fully immersed in a heat transfer fluid; a step of thermally equilibrating all the parts of the device, and putting the fluid in circulation, a step of triggering the acquisition and recording in memory of the temperature and heat flow data. of each measurement chamber, - a step of placing at least one other sample in the liquid or gaseous phase in at least one measurement chamber containing the sample previously put in place, by opening the communication means of the enclosure with a reservoir containing the one or more samples in the liquid or gaseous state, - a step of closing the communication means of the measuring chamber with the reservoir; an opening step, once a new thermal equilibrium has been reached and the measurements acquired and recorded, means of communication of the measurement chamber with the reservoir and of another means of communication of the measuring chamber for the placed in communication with a tank containing a neutral gas under pressure, allowing the emptying of the measuring chamber. a step of correlating the temperature and heat flux data obtained in each chamber and comparing the results between the reference chamber and at least one measuring chamber, by the processing means and the software unit. The presence of a reference chamber and the differential mounting with the at least two measuring cells make it possible to annihilate any anomalies in the regulation of the fluid temperature and the thermal disturbances coming from the external environment. The differential mounting also allows recording on a more accurate scale, differences in temperature and heat flow between the reference speaker and the at least two measuring speakers. Preferably, the method according to the invention may also comprise the following steps: a step of injecting the material to be measured into the measurement chamber and previously thermostatically controlled in said fluid, by opening means of communication of the chamber with a reservoir containing the sample in the liquid state, - a step of closing the means of communication of the measuring chamber with the reservoir containing the sample, - a step of choosing and applying at least one thermal setpoint to the thermal transfer fluid to bring the test liquid to the desired phase transition, respectively gaseous or solid, or to undergo a reaction, the step being associated with triggering the acquisition and storage in memory of the data of temperature and heat flow of each measuring chamber subjected to these same thermal instructions, - a step of opening the means of communication of the enclosure with the res. reservoir containing the liquid sample, after having brought the material present in the measuring chamber into a liquid state, - a step of opening another communication means of the measurement chamber for communicating with a reservoir containing a pressurized neutral gas, for emptying the measuring chamber; - a step of correlating the temperature and heat flow data obtained in each chamber and comparing the results between the reference chamber and at least one measuring chamber, by the processing means and the software package. Thus, the thermal analysis and calorimetry device also makes it possible to carry out other types of studies, such as mixing or dissolution reactions. Preferably, in the method according to the invention, the classification of the materials tested according to their latent heat using the software set and the means of acquisition, recording and data processing comprises: a step of storing the temperature data of the thermal transfer fluid and the reference and measurement chambers, and heat flux data of said speakers, - a step of correlating the temperature and heat flow data of the reference chambers and measuring, which allows the follow-up as a function of time of the temperature and the corresponding peak on the heat flux curve of the measuring chamber, - a step of determining the heat flow between the sample and the fluid of the heat transfer in the phase change zone of the sample, by comparing the heat flow from the measurement chamber to the heat transfer fluid with the flow of heat from the reference chamber to said fluid, the temperature of the measuring chamber being substantially constant, - a step of classifying the materials according to their capacities to store thermal energy, with regard to the quantities of heat flux exchanged between the tested samples and the heat transfer fluid during the phase transition of said samples. A further object of the invention is to describe the use of a thermal analysis and calorimetric device For this purpose, the invention relates to a use of a thermal analysis device and calorimetric differential according to the invention, integrated in an experimental thermal power station as a thermal and calorimetric measuring device in the storage unit where the tested samples can be in the liquid, solid or gaseous state. Thus, certain products or pure bodies at constant pressure can store and restore a lot of energy without their internal temperature varies: this is the case of materials in the course of phase transition of the first order. According to another feature, the use of the thermal and calorimetric analysis device is characterized in that the volume of the measurement chambers makes it possible to solve the problems related to the scale factor and to overcome the sampling phenomena which modify the supercooling properties of the sample (s) studied. Thus, the use of large volume samples statistically allows a very large number of germination sites present in the samples, as will be seen later.

The invention, with its features and advantages, will emerge more clearly on reading the description given with reference to the accompanying drawings in which: FIG. 1 illustrates the invention in one embodiment; FIG. 2 illustrates an example of a thermogram obtained by conventional differential calorimetry; Figure 3 illustrates the invention in another embodiment. DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The invention has been developed to overcome certain defects inherent in the differential differential scanning calorimetry (DSC) ("Differential Scanning Calorimetry"). In the example of the phase change material samples, the temperature-enthalpy relationship is an important feature since it determines the heat storage capacity. Measurements by DSC make it possible to determine this relationship experimentally. Thus, in order to carry out these measurements, commercial calorimeters propose measurement chambers (30, 31) of very small volume, of the order of a hundred microliters, in order to ensure a sufficient accuracy of the enthalpy measurements. However, as soon as it is desired to increase the volume of the samples to be analyzed, the commercial calorimeters quickly become limited. In general, in a calorimeter, the larger the enclosures, the larger the volume of the heat transfer fluid, and the more difficult it will be to maintain the isothermicity of this fluid at a given rate. Indeed, in a very large volume of fluid, the homogenization of the temperature of this fluid is not only difficult to ensure but also require additional external resources and sometimes expensive. In other words, larger speakers require a larger thermostat bath and lead to additional costs in the manufacture of the measuring device. Moreover, for a sample of phase change material, the larger the mass of the sample to be tested, the longer the temperature stabilization time is to ensure good thermal homogeneity and good accuracy in the measurements. Therefore, to have the same measurement accuracy on a sample of larger volume, it is necessary to resort to complex and very cumbersome industrial systems. Indeed, if we increase the size of the speakers (samples), we also multiply the dimensions of the calorimeter several thousand times for this adaptation, it would be necessary to have an analysis device that would have gigantic dimensions . The invention thus proposes an analysis device allowing an adaptation of the principles of the DSC for large samples (about 4700 times the size of a "classical" sample) in a compact analysis device and having a reasonably sized scaled down. The analysis device according to the invention makes it possible to analyze samples of large volume with great accuracy while having a simple configuration, a very good isothermality and while being compact.

To do this, the size of the speakers of the device of the invention offers a compromise between the largest possible dimensions to overcome the disadvantages of conventional calorimeters, while being of reasonable size to obtain the best accuracy of the desired temperature measurement . The invention therefore proposes very precise calorimetric measurements, in a very wide range of sample volumes, in particular for representative volumes of an industrial device (of the order of 50m1 to 1000m1 or even 10000m1), making it possible in particular to to free from certain undesirable kinetic effects, and above all offering possibilities of industrial applications in the field of energy. With reference to FIG. 1, the thermal and calorimetric analysis device (0) will now be described. The invention is a system allowing, among other things, the study of heat exchanges between the different parts of said device (0), typically between a sample of which we want to know certain thermodynamic properties and a thermostated fluid. More specifically, the thermal and calorimetric analysis device (0) authorizes the implementation of a thermal analysis and calorimetric technique making it possible to measure the differences in heat exchanges between a sample, a reference and said fluid. called thermal transfer subjected to a thermal setpoint. This technique, the conventional differential calorimetry, makes it possible in particular to study the physical and chemical transformations of the samples tested, for example and in a nonlimiting manner, the phase transitions of these samples. Of course, this technique makes it possible to study other types of reaction, for example and without limitation, a reaction in the liquid phase between at least two liquid constituents introduced into the measuring chamber (31), a reaction between at least one solid component and at least one liquid component initially placed in the measuring chamber (31), and a gas phase sample introduced into the measuring chamber (31). In some embodiments, the thermal and calorimetric analysis device (0) is a calorimeter comprising a reservoir (1), for example and without limitation, a steel tank, stainless steel tank or any other rigid material withstanding pressure and temperature variations, said reservoir being filled with a heat transfer fluid (2).

The heat transfer fluid (2) may be heated and / or cooled by heating and / or cooling means, for example and without limitation, by immersion heaters (4) distributed in the fluid in a homogeneous manner, said immersion heaters being controlled by means for controlling (41) and regulating (40) the temperature, the regulating means being for example and without limitation, PID type regulators (40), the control means being, for example and in a nonlimiting manner, temperature probes (41). This type of regulator makes it possible to control the power delivered to the immersion heaters (4), in order to subject the thermal transfer fluid (2) to thermal instructions. A thermal setpoint is defined as a controlled variation and followed by the temperature of the heat transfer fluid (2) from an initial temperature to a final temperature. For the sake of good homogeneity of the temperature of the heat transfer fluid (2), a closed fluid circulation system is put in place, containing, for example and without limitation, a pump and a flow control system (21). ) of fluid (2). According to a variant of the invention, the means for heating and / or cooling the heat transfer fluid (2) may be arranged outside the tank (1), for example, at the level of the fluid circulation circuit ( 2). In some embodiments, a refrigeration unit is integrated with the circulation system of the heat transfer fluid (2) so as to study the heat exchanges at temperatures below the temperature of the external environment. However, according to other variants, the refrigeration unit may for example be disposed outside the tank, and may use a refrigerant other than the heat transfer fluid (2). The thermal and calorimetric analysis device (0) is furthermore constituted of at least two measurement chambers (30, 31) which, according to the exemplary embodiment of the invention, are perfectly identical and perfectly fluid-tight. heat transfer (2).

Preferably, the enclosures (30, 31) are provided with an opening and sealing system, allowing the introduction of samples to be tested. These measuring enclosures (30, 31) are, for example and without limitation, cylindrical, machined in a material that is a good thermal conductor, for example and without limitation, aluminum, copper, silver, or any other metal alloy. The geometry of each enclosure may vary without departing from the scope of the invention. Each chamber has an internal volume corresponding to a volume well beyond the volumes used in conventional DSC calorimeters and approaching the representative volume of samples used industrially. For example and in a nonlimiting manner, the internal volume of each chamber is between 50 and 1000 mL, or even 10000 mL, and preferably the volume of each chamber is of the order of 250 mL. According to the invention, said at least two enclosures (30, 31) and said heat transfer fluid (2) have a ratio of volumes allowing easy control of the fluid temperature, in order to preferentially obtain a temperature stability lower than 0.1 ° C of the characteristic temperature of the sample (in particular, the phase change temperature) for the cells having a volume of 1000m1 to 10,000m1, or even a temperature stability of 0.01 ° C for the cells from 50 ml to 1000m1, especially during the phase changes of the sample. In order to obtain this accuracy and this temperature stability, the device of the invention is configured so that the total volume occupied by all the measuring speakers (30, 31) respects a ratio such as the volume of said at least two speakers ( 30, 31) and the volume of said heat transfer fluid (2) obey the following formula (F1): - 2 * wherein 1 / fluid represents the volume of the heat transfer fluid (2); Vhors-all-cell represents the total volume of the analysis device in the absence of said at least two enclosures (30, 31); Twenty-cell represents the internal volume of each chamber (30, 31); The envelope represents the volume of the envelope of each enclosure (30, 31); AT represents a change in temperature of the fluid, during the transformation of the test sample Q represents the heat exchanged during the variation (or increment) between said fluid (2) and said at least two enclosures (30, 31); CPfluid represents the heat capacity volume of the heat transfer fluid (2); CPenvelope represents the volume heat capacity of the envelope of each enclosure (30, 31). It is thus clear that the volume ratios between the volume of the heat transfer fluid (2) and the volume of the enclosures (30, 31) are configured to maintain a good temperature stability within the heat transfer fluid (2). Therefore, a thermal equilibrium can be established so that the temperature of the enclosures (30, 31) does not vary beyond the temperature variation of the fluid (2) during the transformation of the sample to be tested. It should be noted that this variation must remain small for the thermal regulation of the bath remains correct, even when the sample absorbs or returns thermal energy. Preferably, the volume ratio is such that the volume of the heat transfer fluid (2) contained in the reservoir (1) is greater than at least two and a half times the total volume occupied by said at least two measuring chambers. In this way, the heat flows from the enclosures (30, 31) to the heat transfer fluid have very little influence on the temperature variations of the heat transfer fluid (2): the latter thus has a high stability in temperature, less than 0.1 ° C, preferably less than 0.01 ° C. Therefore, the heat transfer fluid (2) having a high temperature stability, it allows the maintenance of the temperature stability of the enclosures (30, 31) less than 0.1 ° C, or even less than 0.01 ° C as has been specified above in the description. Unexpectedly, the inventors have discovered that the internal volume of the enclosures (30, 31) makes it possible to dispense with the scale factor during kinetic supercooling phenomena. This notion of supercooling will be discussed later in the description. In order to be able to measure using the conventional differential calorimetry technique, an enclosure is preferably full of air, and said reference enclosure (30). This enclosure may also contain a reference material other than air, for example, alumina, water, an oil or any other material not undergoing a change of state or physico-chemical transformation caused by the thermal setpoint during the measurement interval. At least one chamber is charged with the sample to be measured, and said laboratory or measuring chamber (31).

In order to measure heat exchanges, each chamber (30, 31) is instrumented with at least one device for measuring temperature variations (Th) and at least one device for measuring heat fluxes (11). This type of instrumentation makes it possible in particular to specify the exothermic or endothermic nature of a reaction. It also makes it possible to overcome outside parasitic phenomena (mechanical, electrical, magnetic or thermal). For example and without limitation, the devices for measuring temperature variations are thermocouples (Th) type K, performing a dead turn around each chamber (30, 31) of measurement. The accuracy of these thermocouples can be between 0.001 K and 1 K, preferentially around 0.1 K.

For example and without limitation, the devices for measuring heat flows are heat flow meters (In consisting of sensitive plates, for example and not limited to platinum, fixed against the outer wall of the measuring chambers (30, 31 The heat flux meters (11) are of great precision, for example and without limitation, between 0.001 and 100 mV / (W.cm-2), preferably between 1 and 5 mV / (W.cm). 2), and provide more accurate heat flux measurements than extrapolated heat fluxes from temperature curves obtained with thermocouples (Th). However, it is useful to instrument the measurement chambers (30, 31) with thermocouples (Th) to define the temperature range in which the heat flow measurements are made. In some embodiments, the reservoir (1) is covered with a cover in the same material, in order to limit the evaporation of the heat transfer fluid (2).

In some embodiments, the thermal and calorimetric analysis device (0) can be sealed. This makes it possible to greatly reduce heat exchanges with the external environment, such a device being an isothermal system whose temperature is slowly varied, and also makes it possible to work in greater temperature and pressure ranges. For example and without limitation, it is possible to work in temperature ranges between -50 and 600 ° C, preferably between 10 and 180 ° C, and pressure ranges between 0 and 100 bar, preferably between 1 and 100 bar. and 10 bars. The temperature and pressure limits of a thermal and calorimetric analysis device (0) depend solely on the temperature and pressure resistance of the materials used for the design of said device. In the vicinity of high pressures, it is possible in some embodiments to charge the measurement chambers (30, 31) with samples without removing said enclosures (30, 31) from the heat transfer fluid (2). In this case, the pressure inside the measurement chambers (30, 31) is independent of the pressure of the rest of the device (0), and remains at atmospheric pressure so that the experimenter can freely load or unload the loudspeakers measuring device (31) in samples. According to an improved embodiment of the invention, at least one measurement chamber (31) can be connected on the one hand to a reservoir (7) containing the sample studied in the liquid phase, and on the other hand to a reservoir (8) containing a gas under pressure. The gas pressure in the tank will in all cases be greater than the pressure inside the measuring chamber (s) (31). The flow of the sample from the reservoir (7) to the enclosure (31), and the flow of gas from the gas reservoir (8) to the enclosure (31) is regulated by communication means (70, 80). of the enclosure with respectively the reservoir (7) containing the sample and the reservoir (8) containing the gas under pressure. These communication means may be, for example and without limitation, communication valves (70, 80) that can be controlled by software contained in the data acquisition means (5).

This improved embodiment is useful for the simulation of industrial processes that a conventional calorimeter does not allow. It is indeed possible to introduce a liquid phase in the device (0) during data acquisition in order to study the energy balance of a dissolution in the liquid phase, an oxidation, a combustion, of any type of chemical reactions in general. According to a variant of this embodiment, a chamber, preferably in the form of a coil, can be inserted into the circuit of the heat transfer fluid, and / or immersed in this fluid upstream of the chamber which contains the sample to be tested. to thermostate the fluid before any reaction takes place.

In some embodiments, the heat transfer fluid reservoir (1) (2) is equipped with a purge system for draining the fluid (2). The choice of the type of fluid (2) depends on the temperature and pressure ranges at which the measurements are made, and a change of fluid (2) in the tank (1) must be able to be done quickly and with few constraints.

Furthermore, it is possible to use for the heat transfer fluid any material that can be in the liquid state at the working temperature at which the change of state of the sample to be tested is observed. In a preferred embodiment, the thermal and calorimetric analysis device (0) is maintained at atmospheric pressure. In some embodiments, the thermal and calorimetric analysis device (0) comprises a software package associated with means for acquiring and recording (5) temperature and heat flow data, for example and non-limiting, an acquisition unit (5) associated with a mass storage device. The thermal and calorimetric analysis device is also equipped with means, hardware and software, signal processing (6), for correlating and comparing the temperature data and the heat flow data obtained from the speaker or speakers. measurement (31) with the data obtained from the reference chamber (30). The acquisition frequency of the temperature and flux data may be, for example and without limitation, between 0.001 Hz and 1000 Hz, and preferably between 1/60 and 1/30 Hz, the thermodynamic phenomena studied being relatively long and extended experiences over several hours. Acquisition frequencies below 1 Hz are therefore appropriate in some embodiments. However, it is worth noting that the frequency limit depends primarily on the technical characteristics of the data acquisition and recording means (5). To better understand the advantages of this thermal analysis device and calorimetric, it is proposed according to the invention a thermal analysis method and calorimetry, which will now be described. In a first step, the sample, object of the heat exchange measurements, is inserted in at least one measurement chamber (31), different from the reference chamber (30). The enclosures (30, 31) are immersed in the heat transfer fluid (2). In some embodiments, it is possible to insert a sample into one or more measurement chambers (31) without removing them from the transfer fluid. In a second step, it is then necessary to ensure that all the parts of the device (0) are at the same temperature, which will be called initial temperature in some embodiments, using the measuring means and controlling the temperature (Th, 41) of the enclosures (30, 31) and the fluid (2). The thermal equilibrium is reached all the more quickly as the heat transfer fluid (2) is circulated by the circulation means (20, 21). This initial temperature is far from the phase change temperature of the measured sample.

The third step consists of a choice and the application of at least one thermal setpoint to the heat transfer fluid (2), using means for controlling and regulating the temperature (40, 41) and means heating (4). A thermal setpoint is defined as a controlled variation and followed by the temperature of the heat transfer fluid (2) from an initial temperature to a final temperature. This thermal stress, applied to the heat transfer fluid (2), will induce heat exchanges between the measurement chambers (30, 31) and the fluid (2). The comparison of the temperature and heat flow data obtained from the reference chamber (30) and the measurement chamber (s) (31) will make it possible to study the physical and chemical transformations of the measured sample. For this to be possible, this step of applying at least one thermal setpoint is associated with the acquisition and recording of the temperature and heat flow data of the measurement chambers (30, 31) subjected to these same thermal instructions.

The last step is to correlate the temperature data with the heat flux data, for each measuring chamber (30, 31), whether it contains a sample (31) or that it is the reference (30). ). These correlations then allow comparisons to be made between the results obtained for the reference chamber (30) and those obtained for at least one measurement chamber (31). These comparisons make it possible to directly detect thermodynamic transitions of the test material, such as phase transitions, and the temperatures at which they occur. Indeed, during phase transitions, a material can store or provide a lot of heat, without changing the temperature. On the other hand, the thermal and calorimetric analysis device (0) is adapted to the study of material in all known thermodynamic states, for example and without limitation the solid, liquid, gaseous stable or metastable states. An example is presented in FIG. 2, showing the temperature (T measurement) and heat flux (-r measurement) curves of the measuring chamber (31), as well as the temperature (Tref) and flux curves of the measuring chamber (31). heat (Ibref) of the reference chamber (30) as a function of time. We note well the phase transition, in this case a melting, which takes place while the temperature of the measuring chamber (31) is almost constant. By comparison, the temperature of the reference chamber (30) increases in exactly the same way as the temperature of the heat transfer fluid (2), and the temperature or flow curves of the reference chamber (30) do not have no discontinuity or breakage. It should be noted that the heat flux curve of the reference (30), outside the temperature zone characteristic of the change of state of the sample, has values that are substantially lower than those of the heat flow curve of the sample. measuring chamber (31). This results from the differences in heat capacities, thermal conductivities and densities between the enclosure (31) containing the sample and the reference (30) inert. An interpretation of the curve, delivered by the analysis device of the invention, for determining the phase change temperature is easy and provides direct access to the desired temperature for the sample tested. In some embodiments, the method can be adapted to mixing or dissolution reactions, not requiring the application of a thermal setpoint.

In a first step, a first sample is placed in at least one measurement chamber (31) different from the reference chamber (30). In a second step, it is then necessary to ensure that all the parts of the device (0) are at the same temperature, which will be called initial temperature in some embodiments, using the measuring means and controlling the temperature (Th, 41) of the enclosures (30, 31) and the fluid (2). The thermal equilibrium is reached all the more quickly as the heat transfer fluid (2) is circulated by the circulation means (20, 21).

In a third step, the acquisition and recording of the temperature and heat flow data of the speakers (30, 31) are triggered. In a fourth step, the communication valve (70) allowing the circulation of at least one other sample in the liquid or gaseous phase is opened in order to inject the said sample or samples into at least one measuring chamber (31) containing at least minus a sample set up beforehand. In a fifth step, this communication valve (70) is closed. Thus, as soon as all the samples are in contact in at least one measurement chamber (31), the system acquires and records the heat flows due to the reactions generated by the contacting of the samples, until the thermal equilibrium be reached. Thus, in the sixth step, once the heat and temperature flow data have been acquired and recorded, the communication means (70) of the measuring chamber (31) with the reservoir (7) are open, and the other communication valve (80), connecting the measuring chamber (31) to the compressed gas reservoir (8), is opened, so as to drive the final material from the measuring chamber (31) to the reservoir ( 7). For example and without limitation, these reactions may be mixing reactions: a reaction in the liquid phase between at least two samples, a reaction between at least one sample, a liquid sample and a gaseous sample; or else dissolution reactions: dissolution of at least one solid sample by at least one liquid sample.

Finally, the last step consists of the correlation of the temperature data with the heat flux data, and for each measuring chamber (30, 31), that it contains at least one sample (31) or that it is the reference (30). This step makes it possible to clearly identify the type of reaction, for example and in a nonlimiting manner, exothermic or endothermic. In certain embodiments, and with reference to FIG. 3, the method can be adapted to samples in the liquid phase, with the possibility of never removing the enclosures (30, 31) from the transfer fluid (2). In this case, at least one measuring chamber (31) is connected to two independent tanks (7, 8), one (7) containing the sample in liquid phase, and the other (8) containing gas under pressure. The pressure of this gas is greater than the pressure inside the measuring chamber (s) (31). The flow of the sample in the liquid phase and the gas between the tanks and the enclosure or enclosures is controlled by flow control means (70, 80), for example and without limitation a communication valve. This process will now be described. In a first step, the communication valve (70) for circulating the sample in the liquid phase is opened to inject said sample into at least one measurement chamber (31). In a second step, this communication valve (70) is closed. The third step consists, as for the process described above, in a choice and in the application of at least one thermal setpoint to the heat transfer fluid (2), by means of control and regulation means of the temperature (40, 41) and heating means (4). This thermal stress applied to the heat transfer fluid (2) is chosen so as to allow a phase change of the sample in the liquid phase, respectively towards the solid or gaseous state depending on the type of measurement, and will induce exchanges. of heat between the measurement chambers (30, 31) and the fluid (2). The comparison of the temperature and heat flow data obtained from the reference chamber (30) and the measurement chamber (s) (31) will make it possible to study the physical and chemical transformations of the tested sample caused by the thermal setpoint. For this to be possible, this step of applying at least one thermal setpoint is associated with the acquisition and recording of the temperature and heat flow data of the measurement chambers (30, 31) subjected to these same thermal instructions. At the end of the measurement and in a fourth step, that is to say once the thermal equilibrium reached and the change of state of the sample finished, the sample has undergone a change of state towards its initial state, that is to say liquid. The communication valve (70) connecting the measuring chamber (31) to the reservoir (7) containing the liquid sample is then opened again. In a fifth step, the other communication valve (80), connecting the measuring chamber (31) to the compressed gas reservoir (8), is opened, so as to drive the liquid sample from the measuring chamber ( 31) to the reservoir containing the liquid sample (7).

Finally, the last step consists in correlating the temperature data with the heat flux data, for each measurement chamber (30, 31), whether it contains a sample (31) or that it is the reference (30). This step clearly identifies the phase changes in the sample, and the temperatures at which they occur.

Another advantage related to the large volume of the measurement chambers (30, 31) is the possibility of carrying out calorimetric dissolution measurements of at least one solid sample initially placed in the measuring chamber (31), by at least one liquid contained in a tank (7) and introduced into the measuring chamber (31) following the opening of the communication valve (70). Working on large-volume samples allows measurement of lower thermal effects relative to one mole of sample: this greatly increases the accuracy of heat flow measurements compared to conventional differential calorimetry allowing only the study low volume samples. Another advantage related to the large volume of measurement chambers (30, 31) is the possibility of solving the problems related to the scale factor and to overcome sampling phenomena during supercooling phenomena. Indeed, the supercooled state is the metastable state of a material remaining in the liquid phase while its temperature is lower than its solidification point. In this state, the least impurity or interface defects present in the enclosure that contains the liquid can trigger the solidification reaction. However, the measuring chambers of the state of the art thermal analysis and calorimetry apparatus are of such a small volume that the number of impurities or interface defects present in the enclosure which contains the liquid can be very different from one speaker to another or from one experience to another. It will therefore be very difficult under these conditions to obtain these metastable states of the material in a reproducible manner. The advantage of having measuring chambers (30, 31) of a sufficiently large volume, for example and in a nonlimiting manner at least 0.05 liters, preferably 0.250 liters, is to overcome these phenomena of sampling. More particularly, with the device of the invention and using larger volume speakers than those used by microcalorimeters, it is possible to observe physico-chemical phenomena that can not be seen below some sample mass.

For example, with the device of the invention, it is possible to observe the phenomenon of crystallization of a liquid which takes place in two stages. The first step concerns the germination, or appearance of the first "embryos" of solid ordered in a completely disordered liquid. The second step concerns the growth of these germs by accretion of the atoms in a liquid into an ordered network. The first step is carried out in practice at a temperature below the thermodynamic equilibrium solid-liquid temperature. This is referred to as the solidification delay or supercooling interval measured in Kelvin (or oc). This supercooling interval depends on the nature of the material, among others, the mobility of the atoms and the ease of the solid in formation to be ordered. .

Germination occurs heterogeneously, that is to say that the "embryos" of solid arise on local defects which may be for example chemical impurities or surface heterogeneities. The number of these defects is an increasing function of the volume of the sample.

By increasing this volume, it promotes the appearance of the first seeds of the crystalline phase and consequently reduces the supercooling interval. Physical phenomena, including heat exchange, occurring in large samples with a volume greater than or equal to 50 mL and tested in the thermal analysis device (0), are measured significantly. more accurate than in the prior art. This accuracy is obtained thanks to enclosures (30, 31) with a volume greater than 50 ml, preferably 250 ml, making it possible to overcome the scale factor and the supercooling phenomenon, and / or through the use of at least at the level of the measuring chamber (31) of at least one heat flux measuring device (11) for more precisely detecting certain transformations, such as the state changes of the samples tested, and / or the volume of heat transfer fluid (2) stored in the reservoir (1), at least 2.5 times the volume of the enclosures (30, 31) so as to maintain the temperature stability of the enclosures (30, 31). Thus, in certain embodiments offering the combination of at least one device for measuring heat flow to at least one enclosure (30, 31) whose volume is greater than or equal to 50 ml, offers great precision in the differential thermal and calorimetric analyzes according to the invention.

Similarly, embodiments combining at least one speaker whose volume is greater than or equal to 50 ml with a heat transfer fluid (2) whose volume is at least 2.5 times greater than the volume of the speakers (30). , 31), offers a high accuracy in the differential thermal and calorimetric analyzes according to the invention. In addition, embodiments combining at least one heat flux measuring device, at least one chamber (30, 31) whose volume is greater than or equal to 50 ml, and a thermal transfer fluid (2) whose volume is at least 2.5 times larger than the volume of said speakers, provides unmatched measurement accuracy. The invention may relate to a combination of all or part of these speaker volume (30, 31), heat transfer fluid volume (2) and heat flow measurement device (11) characteristics. The invention is therefore also better adapted to industrial reality, based on materials of lower purity than materials conventionally studied in the laboratory, but in much larger quantities. Thus, in certain embodiments, the use of the thermal and calorimetric analysis device (0) with industrial materials of a lower purity than the measurement materials in large quantities will make it possible to avoid the metastable states of the material and thus allow the phase changes of the materials under conditions very close to the industrial reality. Due to the size of the sample, analyzes at very slow speeds are also possible. The measuring chambers containing the materials can thus store large amounts of heat without changing the temperature, in order to restore it later. In some embodiments, the features of the invention can be exploited in an energy storage application, the thermal and calorimetric analysis device (0) being integrated in a thermal power station, for example a power plant. experimental solar.

Schematically, the heat transfer fluid (2) is heated by the solar radiation, and this excess heat is absorbed in the materials contained in the measurement chambers (31). The amount of energy that can be stored by the device (0) is all the greater as the materials used in the measurement chambers have latent heats of greater state change. A further advantage of the invention is therefore the implementation of a method for classifying materials according to their latent heat: the higher the latent heat of a material, the more interesting it will be to use it in the process. part of an energy storage application. For example, conventional differential scanning calorimetry is performed at heating and cooling rates of 10 ° C / min. The analysis device of the invention operates at 0.1 ° C / min or 100 times more slowly. The method according to the invention for classifying materials according to their latent heat will now be described. The first step of the method consists in storing in the storage means all the temperature data of the heat transfer fluid (2), the temperature of the reference (30) and measurement (31) chambers obtained respectively by the means of temperature control (41) and temperature measuring devices (Th). The heat flux data obtained by the heat flux measurement devices (11) from the reference chamber (30) to the heat transfer fluid (2) and the measurement chamber (31) to the thermal transfer fluid on the other hand, are also recorded. The second step of the method consists in the correlation by the software set of the temperature and heat flow data, on the one hand for the reference chamber (30), and on the other hand for at least one measuring chamber (31). This step thus makes it possible to identify the phase change temperature of the sample studied. The phase change is marked on the curve representing the heat fluxes between the measuring chamber (31) and the thermal transfer fluid by a peak, the temperature of the measuring chamber (31) being substantially constant during the changeover. phase of the sample. The third step makes it possible to calculate the heat flow of the sample towards the heat transfer fluid (2) during the change of state of said sample, by comparison, thanks to the software set, of the heat flow of the enclosure of reference (30) to the heat transfer fluid (2) with the heat flow from the measurement chamber (31) to said fluid (2). The fourth step is the classification of materials based on their ability to store thermal energy. The greater the heat flow from the sample to the heat transfer fluid during the phase transition of said sample, the greater the latent heat of the sample, and hence its ability to store thermal energy. This technical characteristic of the invention will therefore be used in the context of energy applications related to energy storage. Experimental part 1. Calculation of the volume ratio: The calculation of the volumes necessary for the construction of a thermal and calorimetric analysis device (0) according to the invention is based on a heat balance of the device itself. The heat transfer fluid (2) is temperature controlled. It receives heating means and / or cooling a first thermal power. The device thermally releases a second power through leaks with the external medium. The transformation of the material releases or absorbs a third power. When the device (0) is isothermal and / or no transformation of the material is engaged, the first and second powers are equal; the third power is zero.

If the power is measured under these conditions, the "thermal leakage of the device" is measured. In the tank, a sufficient quantity of temperature-controlled heat transfer fluid is provided so that the temperature of this fluid does not rise or fall below a certain threshold during the heating or cooling of the fluid. sample in a transformation. An example of calculation is given in the following table in which the characteristics are relative to the dimensions of each chamber, the volume of the heat transfer fluid used, the type of material to be tested, and the type of fluid used respectively.

Characteristics of each enclosure: Each enclosure is taken in this cylindrical example, provided with a sealing plug serving as an opening and closing system for the introduction of the sample to be measured. Each chamber has a length of 20 cm, an internal diameter of 6 cm, an outer diameter of 7 cm and an internal volume of approximately 510 cm 3. The cap is 3 cm high, 1 cm thick, 7 cm inside diameter, 8 cm outside diameter. The total volume of each speaker is 840 cm3. The body volume of each enclosure is about 330 cc. The phase change material has a transformation energy AH of between 144 J / cm3 and 648 J / cm3. The shell material of each cell is either an aluminum alloy (durai), copper, whose thermal mass is 815 J / K or 1220 J / K thermal mass steel. The fluid can be oil (thermal mass 586 J / K), water (thermal mass of 1387 J / K) or molten salt (thermal mass of 1097 J / K). To determine the lower limit of the ratio between the total volume of said enclosures and the volume of the fluid, the minimum energy value 144 J / cm 3 is used, the shell material is steel and the heat transfer fluid is the water. By calculating the lower limit according to the formula (F1), with an AT of 0.02 K, we obtain a VtruidiVhors all-enclosure ratio = 2.76 If the geometry of the enclosure is parallelepipedal, for example 1001 00 * 250 mm, the ratio VtruideNhors while speakers becomes greater than or equal to 2.5. 2. Comparison of the measurement results of a sample provided on the one hand by a conventional calorimeter and on the other hand by a thermal and calorimetric analysis device according to the invention. Measurement in conventional differential calorimetry: The conventional measurement calorimeter used is that designed by Setaram and bearing the reference DSC131. A first sample of a sebacic acid and a second sample of a succinic acid were analyzed by the DSC 131 calorimeter. With the DSC measurement, the supercooling of the sebacic acid is around 5.7 ° C. succinic acid around 56.9 ° C. Measurement with the thermal and calorimetric analysis device of the invention: With the analysis device according to the invention, it has been possible to demonstrate that the supercooling of sebacic acid takes place at 1 ° C. and that of the succinic acid at 14.8 ° C. Thus, conditioned in a volume closer to that of the industrial samples, the average supercooling degree of the first and second samples is much closer to that observed in the industrial application, which the classical DSC could not have brought to light. .

In addition, having measurements as accurate and close to those observed in industrial application is an important advance when using phase change materials (PCMs). Indeed, these MCP materials are generally used to store thermal energy in a very small temperature range but with high accuracy. These materials have a higher storage density than other materials when used around the temperature of their phase change but have volume-dependent characteristics. As a result, having very precise measurements opens the way to integrate (or better use) these materials in various applications that require precise knowledge of this temperature.

The present application describes various technical features and advantages with reference to the figures and / or various embodiments. Those skilled in the art will appreciate that the technical features of a given embodiment may in fact be combined with features of another embodiment unless the reverse is explicitly mentioned or it is evident that these features are incompatible. In addition, the technical features described in a given embodiment can be isolated from the other features of this mode unless the opposite is explicitly mentioned.

It should be obvious to those skilled in the art that the present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered by way of illustration, but may be modified in the field defined by the scope of the appended claims, and the invention should not be limited to the details given above.

Claims (16)

REVENDICATIONS1. Device for the differential thermal and calorimetric analysis (0) of a test sample, in particular of a phase-change material in a measuring interval, comprising: - a reservoir (1) in which at least two enclosures are arranged identical (30, 31), a so-called reference chamber (30) filled with a reference material and at least one measuring chamber (31) comprising the test sample, - a temperature measuring device (Th) associated to each enclosure, data acquisition and processing means (5, 6) for delivering, as a function of time, differential signals representative of the temperature difference between said at least two enclosures (30, 31) for deducing a characteristic temperature, in particular the phase change temperature, of the sample to be tested, said analysis device (0) being characterized in that: - it comprises means for heating and / or cooling (4), for transmitting to said at least two enclosures (30, 31) a working temperature in the measuring interval, the reservoir (1) being filled with a heat transfer fluid (2) which can be subjected to minus a predetermined thermal setpoint for regulating it, said at least two enclosures (30, 31) being totally immersed in said fluid (2) during the differential analysis, - it comprises a device for measuring the heat flux (11) associated with each enclosure (30, 31) so that the differential signals delivered are also a function of the difference between the thermal flows passing through said at least two enclosures (30, 31), 2. Analysis device (0) according to claim 1 characterized in that the volume ratio between said enclosures (30, 31) and said heat transfer fluid (2) provide stability of the characteristic temperature of the sample to test, such as the temperature during phase changes of this sample, below 0.1 ° C. 3. Analysis device (0) according to claim 1 or 2 wherein the volume ratio is such that the volume of the heat transfer fluid (2) contained in the reservoir (1) is at least greater than two and a half times the total volume occupied by said at least two measurement chambers (30, 31). 4. Analysis device (0) according to any one of claims 1 to 3 wherein each of said at least two enclosures (30, 31) has an internal volume of at least 50 milliliters. 5. Analysis device (0) according to any one of claims 1 to 4, comprising closed circuit circulation means (20) of the heat transfer fluid (2) associated with means for controlling the circulation (21). ) of the heat transfer fluid (2). 6. Analysis device (0) according to any one of claims 1 to 5 wherein said at least two enclosures (30, 31) are sealed and one of said at least two enclosures (30, 31) is provided with an opening and closing system for introducing the sample to be measured and maintaining it in a sealed manner with respect to the external environment. 7. Analysis device (0) according to any one of claims 1 to 6, wherein the reservoir (1) containing the fluid (2) heat transfer is hermetic. 8. Analysis device (0) according to any one of claims 1 to 7, wherein at least one measuring chamber (31) is connected on the one hand to a reservoir (7) containing the sample to be tested. liquid phase, on the other hand to a tank (8) containing a gas under a pressure greater than the internal pressure of the chamber (31), the circulation of the sample to be measured or the pressurized gas of the tanks (7, 8) to the measuring chamber (31) being provided by means of communication (70, 80) of the measuring chamber (31) respectively with the reservoir containing the sample (7) and the compressed gas reservoir ( 8). 9. Analysis device (0) according to any one of claims 1 to 8, wherein the reservoir (1) is equipped with a purge system for emptying and replacing the heat transfer fluid (2) by a fluid adapted to the temperature ranges necessary to study the phase changes of the sample to be tested. 10. Analysis device (0) according to any one of claims 1 to 9, wherein the temperature control of the heat transfer fluid (2) is provided by thermo-resistors (4) whose instantaneous power is regulated by temperature control means (40), for example at least one PID regulator (40) and / or a refrigeration unit that can be integrated with the circulation means (20) of the heat transfer fluid (2), and the measurement the temperature of said fluid (2) is provided by control means (41), for example a temperature sensor (41). 11. Analysis device according to one of claims 1 to 10, wherein the measuring chambers (30, 31) are made of a good thermal conductive material, preferably aluminum, copper, silver or silver. metal alloys and / or the reference material is a material that does not undergo any change of state or physico-chemical transformation caused by the said at least one thermal setpoint in the measurement interval, such as, for example, air, sapphire, water, alumina, water, oil, or air. 12. A method for the differential and quantitative thermal and calorimetric analysis of a sample to be tested, the method being implemented by a differential thermal and calorimetric analysis device (0) according to any one of claims 1 to 10, and characterized in that it comprises the following steps: a step of placing the sample to be tested in at least one measurement chamber (31), different from the reference chamber (30), and being totally immersed in a heat transfer fluid (2), - a thermal equilibrium step, at an initial temperature remote from the phase change temperature, of all the parts of the analysis device (0), and of putting into circulation fluid (2), - a step of choosing and applying at least one thermal setpoint to the heat transfer fluid (2), associated with triggering the acquisition and recording in memory of the temperature data and heat flux of each measuring chamber (30, 31) subjected to these same thermal setpoints, - a step of correlating the temperature and heat flow data obtained in each chamber (30, 31) to deliver as a function of the time, differential signals representative of the temperature difference between said at least two enclosures (30, 31) and the difference between the heat flows through these enclosures to directly deduce the phase change temperature of the sample to test 13. Method according to claim 12, characterized in that it comprises the following steps: a step of placing at least one sample in at least one measurement chamber (31), different from the reference chamber (30), the enclosures being fully immersed in a heat transfer fluid (2); a step of thermally equilibrating all the parts of the analysis device (0), and circulating the fluid (2), a step of triggering the acquisition and the recording in memory temperature and heat flow data of each measuring chamber (30, 31), - a step of introducing at least one other sample in the liquid or gaseous phase into at least one measurement chamber (31) containing sample previously set up, by opening the communication means (70) of the chamber with a reservoir (7) containing the said sample or samples in the liquid or gaseous state, - a step of closing the communication means (70). ) of the measurement chamber (31) with the reservoir (7). an opening step, once a new thermal equilibrium has been reached and the measurements acquired and recorded, means of communication (70) of the measuring chamber (31) with the reservoir (7) and of another means of communication (80) of the measurement chamber (31) for communication with a reservoir (8) containing a pressurized neutral gas, for emptying the measuring chamber (31). a step of correlating the temperature and heat flow data obtained in each chamber (30, 31) and comparing the results between the reference chamber (30) and at least one measurement chamber (31), by means of processing means (5) and the software package. 14. The method of claim 12 or 13, characterized in that it comprises the following steps: - a step of injecting the material to be measured in the enclosure (31) by opening means of communication (70) of the enclosure with a reservoir (7) containing the sample in the liquid state, - a step of closing the communication means (70) of the enclosure (31) with the reservoir (7) containing the sample, - a step of choice and application of at least one thermal setpoint to the heat transfer fluid (2) to bring the test liquid to the desired phase transition, respectively gaseous or solid, or to undergo a reaction, the step being associated triggering the acquisition and storage in memory of the temperature and heat flow data of each measurement chamber (30, 31) subjected to these same thermal setpoints, - a step of opening the communication means ( 70) of the enclosure (31) with the reservoir (7) containing the liquid sample, after having brought the material present in the measuring chamber (31) into a liquid state, - a step of opening another communication means (80) of the measuring chamber (31). ) for placing in communication with a reservoir (8) containing a pressurized neutral gas, allowing the emptying of the measuring chamber (31), - a step of correlating the temperature and heat flow data obtained in each chamber ( 30, 31) and comparing the results between the reference chamber (30) and at least one measuring chamber (31), by the processing means (5) and the software unit. 15. Method according to any one of claims 12 to 14, characterized in that the classification of the tested materials according to their latent heat using the software set and means of acquisition, recording and data processing (5, 6) comprises: - a step of storing the temperature data of the heat transfer fluid (2) and the reference (30) and measurement (31) chambers, and heat flux data of said enclosures (30, 31), a step of correlating the temperature and heat flow data of the reference (30) and measuring (31) chambers, which allows the temperature and the corresponding peak to be monitored as a function of time. the heat flux curve of the measuring chamber (31), a step of determining the heat flux between the sample and the heat transfer fluid (2) in the phase change zone of the sample, by comparison of the heat flux of the pregnant e measurement (31) to the heat transfer fluid (2) with the heat flow from the reference chamber (30) to said fluid (2), the temperature of the measurement chamber (31) being substantially constant a step of classifying the materials according to their capacity to store thermal energy, with regard to the quantities of heat flux exchanged between the tested samples and the heat transfer fluid (2) during the phase transition of said samples. 16. Use of a differential thermal and calorimetric analysis device (0) according to any one of claims 1 to 11, characterized in that the device (0) is integrated in an experimental thermal power station as a thermal measuring device. and calorimetric in the storage unit where the tested samples can be in liquid, solid or gaseous state.