SU1323869A1 - Calorimeter - Google Patents

Abstract

The invention relates to thermal measurements and makes it possible to increase the accuracy of measurements by reducing the heat exchange between the shell and the cell. The test substance is placed in a capsule 4 calorimetric i. Cell 3. The heat released by the substance is captured by the battery thermocouple 6, which measures the difference in temperature between the cell 3 and the shell 5 placed relative to each other with a gap. The heat shield 7 installed in the gap reduces convection heat exchange between elements 3 and 5. Eliminating the radiant component, significant at high temperatures, allows the electrically insulating heat-conducting filler 8 to fill the gap. The ratio of the sizes of sections of the gap divided by screen 7 is inversely proportional to the ratio of the areas of the side surfaces of the cell 3 and screen 7. 2 Il. 00 00 00 O5 co

Description

The invention relates to thermal measurements and can be used in various fields of technology, for example, to determine the heat capacity of substances, to study the processes of absorption and heat release in physics, thermochemistry, biology, etc.

The whole invention is to increase the measurement accuracy by reducing the heat exchange between the calorimetric cell and the calorimetric envelope while simultaneously stabilizing the sensitivity of the calorimeter by linearizing the volt-watt characteristic of the calorimeter.

FIG. 1 schematically shows the calorimeter; in fig. 2 shows section A-A in FIG. one.

The calorimeter contains a metal calorimetric unit 1 enclosed in a thermostat, inside which a calorimetric element 2 is placed, consisting of a calorimetric cell 3 with a capsule 4 in which the test substance is placed, and a calorimetric shell 5, which is in thermal contact with the calorimetric unit 1. Thermal the connection between the calorimetric envelope and the calorimetric cell is carried out using a battery of thermocouples 6. In the space between the cell and the sheath there is a screen 7 separating the gap between them on two sites (Fig. 2), in each of which there is an electrically insulating heat-conducting filler 8, a powder of aluminum oxide. VIHII.

The calorimeter works as follows.

The measured heat released from the capsule 4 through the calorimetric cell 3, then through the branches of the battery thermocouple 6 and the filler 8 goes to the calorimetric casing 5, and then to the calorimetric unit 1, while the battery thermocouple 6 measures the temperature difference between the calorimetric cell and the calorimetric casing . Preliminary calibration experiments establish the correspondence between the heat flux, the separation of Ngims in the cell, and the thermal emf of the battery thermocouple.

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It is known that heat exchange between the calorimetric cell and the shell is generally characterized by the following reasons: radiation of the outer surface of the calorimetric cell and the inner walls of the shell; thermal conductivity of the calorimeter parts projecting into the surrounding air; thermal conductivity and convection of the thermal insulating layer of air between the calorimetric cell and the shell.

To reduce convection, heat transfer, leading to instability of the sensitivity of the calorimeter, a screen is installed between the calorimetric envelope and the cell, dividing the gap into two sections.

It was established experimentally that with a ratio of the sizes of the gaps formed, which are inversely proportional to the ratio of the areas of the side surfaces of the cell and the screen, it is possible to reduce the convective component of heat transfer by 2.1 times.

A further reduction in the convective component and the elimination of the radiant component, significant at high temperatures, is achieved by introducing an electrically insulating heat-conducting filler (alumina) into the gaps, while the accuracy of measurements using the proposed device is increased by linearizing the volt-watt characteristic of 4.9 times.

Claims (1)

Invention Formula A calorimeter containing a calorimetric block in which a calorimetric cell with thermosensitive elements is placed surrounded by a shell, characterized in that, in order to improve the measurement accuracy, a heat shield is installed between the shell and the cell, dividing the gap between them into two sections, while the sizes of the gaps formed are inversely proportional to the ratio of the areas of the side surfaces of the cell and the screen, and each of the gaps is filled with an electrically insulating heat-conducting filler. tfue.Z VNIIPIZakaz 2954/44 Circulation 776 Subscription Production and printing enterprise, Uzhgorod, st. Project, 4