SU498539A1 - Device for determining thermal conductivity - Google Patents

Description

The invention relates to thermophysical measuring devices.

In order to automatically determine the thermal conductivity coefficient during the thermophysical experiment with the quasi-stationary thermal regime of the studied solid materials, calculating devices are used that are made on the elements of analog computer technology (DC operational amplifiers). The drawbacks of this type of device are the complexity of the computing circuit, the high cost of direct current amplifiers (DCA), the presence of zero drift in the DCF.

The purpose of the invention is to simplify the counting scheme for determining the coefficient of thermal conductivity in the quasi-stationary thermal mode of the solid materials under study and to improve the measurement accuracy.

To achieve this goal, the proposed device is equipped with an electronic automatic potentiometer for measuring the temperature difference in the calorimeter, the rheostatic output of which is connected to the power supply circuit of the first rail, doubled with the second. The sliders of the rheochords are kinematically connected to the motor shaft connected by the control winding through an amplifier and a compensation electric circuit of the first rheochord to the output circuit of the power converter connected to the calorimeter. In addition, a recording device is introduced into the device, the input of which is connected to the output electric circuit of the second rheochord.

The drawing shows a block diagram of the proposed device.

The device for determining the thermal conductivity contains two double rheochords / and 2, the sliders of which are kinematically connected to the motor shaft 3, an electric power measuring transducer 4, an amplifier 5, an electronic potentiometer 6, a recording device 7, a calorimeter 8.

The calculation formula for the coefficient of thermal conductivity in the quasi-stationary thermal regime of the materials under study is:

llA 2Ag

where q is the heat flux; R is the plate thickness; At is the difference in temperature on the plates.

Output voltage Ui of the measuring transducer (power 4, dissipated by the electric heater, is proportional to the heat flux q

U, k, .q,

where ki is a constant coefficient. The output voltage C / 3 of the electronic potentiometer 6 is proportional to the non-dependence of the temperatures on the test plates in the calorimeter 5

t / 2 2-A,

where H2 is a constant coefficient.

The supply voltage U of the Reochord 2 is set to

Us k, .R,

where kg is a constant coefficient. The variable f / i and Uz are in phase. The input of the amplifier 5 receives a differential signal

D (7, -Y4. F / 2,

where 4 is the coefficient determined by the position of the Slider of a reichord /. The amplified differential signal is fed to the engine, which interleaves the slider until the difference signal Af / becomes zero. In this case, the ratio will be

f /, and.

6, and.

and, u,. ,; and, k, qR

 from

and.,

t

k.,

Consequently, the voltage AND coming to the input of the recording device 7 is directly proportional to the coefficient of thermal conductivity of the materials under study.

“J

The voltage may be voltage or alternating current and is determined by the type of recorder. .

Claims (1)

Invention Formula A device for determining the coefficient of thermal conductivity in the quasi-stationary thermal regime of solid materials, including a calorimeter, a power converter, temperature meters, a counting solution A circuit and a recording device, characterized in that, in order to increase accuracy, the counting circuit is equipped with an electronic automatic tool, meter for recording the temperature difference in the calorimeter, the rheostatic output of which is connected to the power supply circuit of the first rheochord doubled with the second, the sliders of which are kinematically connected with the motor shaft connected through the control winding, the amplifier and the compensation electric circuit of the first rail into the output circuit of the power converter connected to the calorimeter and a registering device, the input of which is connected to the output electric circuit of the second reichord. Vn