SU1597707A1 - Apparatus for measuring heat conduction of hard materials - Google Patents

Abstract

The invention relates to experimental thermal physics — to devices for determining the thermal conductivity of solid materials. The purpose of the invention is to reduce the measurement time and expand the scope. The device contains two heat-conducting units, one of which has a heater and the other has a heat meter. These blocks are made in the form of heat pipes, one of which is equipped with a non-condensable gas with a heater in the area of its surface in contact with the sample under study, and a heat meter on the second heat pipe covers its external surface in the cooling zone. 1 il.

Description

The invention relates to the field of thermal properties research, namely, to the measurement of thermal conductivity of solid materials.

The aim of the invention is to reduce the measurement time and expand the scope.

The implementation of heat-conducting blocks in the form of heat pipes allows to significantly reduce the thermal inertia of the blocks and thereby reduce the measurement time by reducing the time for the device to reach a stationary thermal mode.

The drawing shows the structural diagram of the proposed device.

The device contains two heat-conducting units, each of which is made in the form of a heat pipe, in the case 1 of which there is a capillary. structure 2 and heat carrier (liquid in capillary structure 2 and its vapors

inside the case 1). The outer surface of the housing 1 has zones of heating 3 and cooling 4. One of these pipes (in the drawing above) is supplied with non-condensing gas 5. In its heating zone 3 a heater 6 is installed, and in the cooling zone 4 there is a contact surface 7 On the case 1, the other pipes, the contact surface 7 is placed in the heating zone 3, and the heat meter 8 in the cooling zone 4. Sample 9 is mounted between the contact surfaces 7.

The capillary structure 2 can be made of metal felt, metal mesh or other porous material and can be made in the form of threaded or concentric ditches on the inner surface of the housing 1. The material of the housing 1 and the capillary structure 2 is chosen for reasons of compatibility with the coolant. As a heat carrier

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ate

maybe water, alcohol, acetone or liquid metals. The choice depends on the operating temperature of the device. Non-condensable gas may be possible. spirit or any inert gas. The contact surfaces 7 have a flat shape. To prevent the occurrence of convective currents and reduce lateral heat loss, sample 9 should be surrounded by Q screens (not shown).

A device for measuring thermal conductivity works as follows.

In preparation for the measurement, heat pipes are diluted, the heater is turned on 6, and the Pipe with non-condensable gas 5 is heated over the other heat pipe by several degrees (the amount of overheating is determined in calibration experiments with reference 20 samples). In this case, the heat carrier in the capillary structure 2 in the heating zone 3 evaporates, its vapors condense on the inner surface of the corona 1 in the cooling zone 4, pushing 25 upwards non-condensable gas 5. Cooling the heat pipe body is natural convection of the environment. The heat carrier condensate under the action of gravity flows. The JQ is down and, with the aid of a capillary structure 2, is evenly distributed along the inner surface of the housing 1 in the heating zone 3.

Next, the contact surfaces 7 protrude, see & contact grease, sample 9 install contact surface 7 of the heat pipe with a heat meter 8 and lower another heat pipe, clamping sample 9 between the contact surfaces 7. In this case, the heat flux from heater 6 is transferred additionally through sample 9 to a heat pipe with a heat meter-8. Since the heater 6 is permanently turned on, less heat is removed from the heat pipe with the heater 6. However, its temperature remains almost unchanged due to the fact that the heat pipe is partially filled with non-condensable gas. The heat flux passed through the sample 9 evaporates the coolant from the capillary structure of the heat pipe with a heat meter 8, the vapors condense on the inner surface of the housing 1,

and the condensate under the action of capillary forces and gravity comes back to the heating zone 3. This heat pipe is also cooled by natural convection of the environment.

If the diameter of the heat pipes is 10 mm, the wall thickness of the body is 1 mm, and the length is 200 mm, then the volume of the metal from which the heat blocks are made is less than 20 cm, i.e. more than 30 times less than the volume of blocks of the known device (the diameter of each block is 80 mm, height is 75 mm). Consequently, the inertia of the blocks will decrease by 30 times, which entails a reduction in the measurement time by a factor as well.

The temperature of the heat pipe with a non-condensable gas makes it possible to have a reference temperature unchanged during a series of measurements.

In addition, new and significant in the proposed device is that the heat meter installed in the cooling zone of the heat pipe is not in contact with the sample. This makes it possible to significantly simplify its design and makes it possible to carry out measurements on samples of arbitrary geometry without additional measurements, which makes it possible to expand the field of application of the device.

Claims (1)

Invention Formula A device for measuring the thermal conductivity of solid materials, including two thermally conductive units, one of which is equipped with a heater, the other with a heat meter and both with temperature sensors located on surfaces in contact with the test sample, characterized in that in order to reduce the measurement time and applications, heat-conducting blocks are made in the form of heat pipes, one of which is supplied with non-condensable gas with a heater in the area of its contacting surface. The new tube covers its outer surface in the cooling zone. neither 8 J 2