SU1408326A1 - Method of measuring heat conductivity - Google Patents

Abstract

The invention relates to the field of thermal testing, namely to the field of measuring the thermal conductivity of a substance. The goal is to increase accuracy by reducing the distorting effect of contact thermal resistance on test results. Two heat fluxes are passed: one successively through the contacting sample and the standard, and the other through the contacting standard and the sample. The temperature difference between the two regions of contact between the samples and the standards is recorded. In addition, record the average value of the heat flux. This operation, further as compared with the known technical solutions, provides an increase in accuracy by reducing the influence of contact thermal resistances. 1 il. SL

Description

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Attenuation refers to thermal m, namely to the area of the thermal conductivity of substances, the invention is to increase the

by reducing the distorting contact teph. JBBIX resistance

NZ drawing shows the device, .pgaj feviomee the proposed method. JQ The device consists of a source 1 of heat 2 of the receiver, which placed two pairs of samples, each of which consists of test sample 3 and reference 4, separated by 15 I temperature-equalizing plate 15, in which the junctions of the differential thermocouple 6 mounted to the secondary device 7. Standards I 4 are made in the form of heat meters with one 20 I thermal resistance. I The signals from them are measured by the secondary instrument. 8, which can alternately i be connected to heat meters with the help of an I switch 9. The elements of the device 25 I are protected by thermal insulation 10.

j The method is as follows

I way.

I Install test samples 3 into device cells, then 30 include source 1 and receiver 2 heat, driving them to different constant temperatures selected for measurement. In this case, the readings of the secondary devices 7 and 8 are varied for a while. Their stabilization means the onset of stationary heat transfer. After that, the temperature difference in the areas between the test samples and standards 40 is measured according to the scale of the secondary device 7, and the heat flux value is found as the arithmetic average of the secondary device 8 when it is connected alternately to each heat meter. 45 According to the measured values determine the thermal conductivity of the sample under the formula

oh 5

.50

with (-li- - -4.I-)

Che.Za

Where

index e refers to the standard, and index o refers to the test sample;

 - thermal conductivity; 1 - length; S - section;

LT is the temperature difference in the areas of contact between samples and standards; “P is heat flow.

Increasing the accuracy is provided by measuring an additional quantity — the heat flux P, which makes it possible to exclude from the calculation formula contact thermal resistances along the path of each of the heat fluxes.

The proposed method is particularly promising for studies of substances with high thermal conductivities.

Claims (1)

Invention Formula The method for measuring the thermal conductivity of substances, which consists in creating two parallel heat fluxes between the source and the receiver, one of the streams is passed in series through the sample and the standard, the other stream through the standard and the sample, measuring the temperature difference in the contact areas samples and standards and according to the obtained data, calculate the desired value, characterized in that, in order to increase accuracy by reducing the distorting effect of contact thermal resistance on the results ytany further measured value of the heat flow and thermal conductivity rasschitgaayut formula 1e lt , about ) index e refers to the standard, and index o refers to the test sample; thermal conductivity; length; cross section; temperature difference in the areas of contact between samples and standards; heat flow.