Detectors calorimetric

Thus in addition to the data required to determine the surface excess amount (cf. Section 3.3.1), one needs to know dQKV (the heat exchanged reversibly during each adsorption step) and Vc (the volume - dead space - of that part of the adsorption bulb which is located within the calorimetric detector (cf. Figure 3.15). Vc is evaluated by liquid weighing or by geometrical considerations and corrected for the sample volume. 

The vertical cylindrical fiimace consists of a graphite resistor surrounding a gas-tight alumina tube, with an inner diameter of 23 mm and a length of 600 mm, in which the calorimetric detector is placed and the experimental chamber, localized. The geometry of the resistor provides a 140-mm long constant temperature zone in the central part of the tube. The furnace has an external water-cooled jacket and can be heated up to about 2000°C. 

The features of the calorimetric detector and of the mixing and stirring systems, located within the experimental chamber, vary according to the nature of the experiment. The acquisition and processing of the experimental data is operated by a computer. 

Low-Temperature Calorimetric Detectors for High-Mass ions... 

Low-temperature calorimetric detectors, also known as cryogenic detectors [84], are based on the principle that the kinetic energy E of the impinging ions is transformed into heat the rise in temperature is given by... 

N. E. Booth, Calorimetric detectors for high mass ions. Rapid Commun. Mass Spectrom. 11, 943-947 (1997). 

A schematic representation of the instruments is shown in Fig. 4. The transi-tiometer itself is constructed as a twin calorimeter with a variable operating volume. It is equipped with high-pressure vessels, a pVT system, and Lab-VIEW-based virtual instrument software. Two cylindrical fluxmeters or calorimetric detectors (internal diameter 17 mm, length 80 mm), each made from 622... 

Fig. 10 Three differential modes of scamimg transitiometry according to the differential principle of the calorimetric detector, taking into account the respective roles of the measuring (M) and reference (R) vessels and the content of the reference vessel, (a) Thermal I differential without reference sample mode, (b) Thermal II diEfeitmtial with reference sample mode, (c) Thermal II differential comparative mode in this case a direct comparison between two polymers (MDPE and PVDF) samples is possible...

Fig. 5 Photograph of a standard scanning transitiometer (from BGR TECH, Warsaw). The calorimetric detector, which can be moved up and down over the measuring and reference calorimetric vessels (in twin differential arrangement), is shown in its upper position. In this position, the calorimetric vessels, which are firmly fixed on the stand table, are then accessible for loading...

The quartz tube is introduced in the Calvet type DSC (set in the vertical position). A fritted glass substrate is located in the middle of the tube to receive the powdered sample in order to be surrounded by the calorimetric detector. Tight connections are adjusted at both ends of the tubes for the gas inlet and outlet. 

The relation (2.16) shows that the power dissipated in the vessel is directly correlated to the heat flux. The term e/8 corresponds to the calibration factor of the calorimeter. This relation provides the correlation between the electrical output of the calorimetric detector and the corresponding heat flux exchanged with the sample. 

In a Calvet calorimeter, the most important part is the thermoelectric element that provides the performances of the calorimetric detector. 

This procedure needs to know precisely the volume Vs of the sample cell, which is located within the calorimetric detector and to reduce the dead volume, which is outside the detector. Vs can be estimated by liquid weighting or from geometrical measurements and by taking into account the volume occupied by the sample. 

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