SU800845A1 - Device for determining thermophysical characteristics of materials - Google Patents

Description

(54) DEVICE FOR DETERMINATION OF THERMOPHYSICAL CHARACTERISTICS OF MATERIALS

thermal mode. The temperature range of the device is negligible.

The purpose of the invention is to simplify the stabilization of the sample temperature and the density of the heat flow through it, as well as the extension of the temperature range of measurements.

The goal is achieved by attaching to each flow heat exchanger a thin electric heater with a uniform heat generation density and a flat temperature equalizing plate with the heat meter and thermocouple placed in the center flush with the sample and the heat exchangers have the same hydraulic resistance and are connected in parallel to the circuit of one heat meter. thermostat or cryostat. Two electric heaters are attached to the upper heat exchanger, one of which is identical to the electric heater on the lower heat exchanger and is connected with it in series to one power supply circuit.

The same hydraulic resistance of the heat exchangers allows them to be thermostatically controlled at the same temperature. The power of the electric heaters is chosen such that the temperature of the sample is above the temperature of the heat exchangers by.

The drawing schematically shows the proposed device.

Flow heat exchangers 1 and 2 have the form of short hollow cylinders and are inserted into a cylindrical heat-insulated body 3. The test material (sample) 4 is placed in the space between the heat exchangers 1 and 2 and the body 3. To the working surface of the heat exchanger 1 are attached thin electric heaters 5 and 6 and flat temperature equalizing . Plain 7. An electric heater 8 and a temperature-equalizing plate 9 are attached to the working surface of the heat exchanger 2. The plates 7 and 9 are flush with the surface in contact with the sample, mounted Heat meters 10 and thermocouple junctions 11. Heat exchangers are connected in parallel to the coolant supply line 12 (coolant from a thermostat (cryostat)) 13. Electric heaters 5 and 8 have the same electrical resistance, are connected in series to the power supply circuit 14, have the same power and serve to control the sample temperature Electric heater 6 is connected to power supply circuit 15 and serves to regulate the density of the heat flux penetrating the sample.

The device works as follows.

Sample 4 is loaded into the device ensuring uniform contact with

plates 7 and 9. Heat exchangers 1 and 2 are supplied with a constant temperature coolant. The circuit 14 is supplied with a voltage sufficient to heat the sample to the desired test temperature. The voltage 15 is supplied with a voltage sufficient to obtain a stationary heat regime with a given heat flux density, in a steady-state steady-state mode, heat flux densities are measured through the upper and lower surfaces of the sample q q q and temperatures at the same points t and t. Knowing the thickness h of the sample, its thermal conductivity is calculated using the formula,. but. h

L h

thermal conductivity of the sample;

where is the sample thickness; heat flux density

q through the sample; . t-and t-temperature of the upper and lower surface of the sample. After that, a transient thermal regime is performed, increasing the voltage in circuit 14 when the sample is heated or reduced when cooled. In so doing, the sample temperature changes accordingly. The amount of heat absorbed (allocated) for the transitional mode by the sample volume located between single contact surfaces with heat exchangers is equal to the integral of the heat flux density through the sample surface over time and proportional to the area closed by the curves μ «(1) and Чц (t) transient recording diagram. The transient mode ends with a new. Stationary mode. The volumetric heat capacity of the sample is determined by the formula

Wed - "

hCtj- t / T is the mass heat capacity of the sample;

 sample density; S. The area in the recording diagram is closed by the q., (T) and q (r) curves;

To record scale; Y and 1 „are the average sample temperatures in the initial and final stationary thermal conditions. The coefficient of thermal conductivity of the sample is calculated using the values of L. and with p.

The proposed device is intended for complex investigation of solid and liquid materials and bulk solids in the range 200-370 K. It is easy to manufacture and maintain. Energy consumption and coolant compared with the known device is reduced, and the stability of the modes of experience and the accuracy of the result is increased.

Claims (2)

Claim 1. A device for determining the thermophysical characteristics of materials in a flat layer in alternating stationary and transient thermal conditions, consisting of two flow heat exchangers between which the sample is placed, two heat meters and two thermocouples, characterized in that, in order to simplify stabilization of the temperature of the sample and the density of the penetrating its heat flux, as well as expanding the temperature range of measurements, a thin electric heater with uniform tight with heat dissipation and a flat temperature equalizing plate with a heat meter and a thermocouple flush with the surface facing the sample, the heat exchangers having the same hydraulic resistance and connected in parallel to the circuit of one thermostat. 2. Device according to claim 1 of m and l - ³ sistent in that the heat exchanger attached to the upper two electron ronagrevatelya, one of which is identical to the lower heat exchanger and electric heater incorporated with them • 0 sequentially in a supply chain.