SU418780A1 - - Google Patents

Description

one

The invention relates to the field of theophysical instrumentation.

The known devices for measuring the coefficient of temperature of the pipe 1 of the materials operating in the myotonic heating mode contain tenloizoloniyuyu skin.x, a base with a heater, upper and lower contact terminals and three temperature sensors.

Such devices have a number of disadvantages. To ensure that the sample is symmetrically heated, the finishing work related to the machining of the metal core parts is required.

The asymmetry of heating is due to the fact that the plates have different heat capacity, geometry, and heat exchange with the surrounding parts of the core.

The proposed device allows to increase the measurement accuracy due to the fact that between the identical contact plates made in the form of hemispheres and the base two racks are inserted with spherical sockets in the upper part and deep ribs in the bottom, which are in contact with the base ribs.

The drawing shows the proposed device.

The device consists of a detachable insulating sheath and a metal core.

The metal core contains base 1, heater 2, pillars 3, 4, contact plates 5, 6, between which test sample 7 is clamped, and cap 8 with heater 9.

The core is fixed in the casing 10 on six metal racks I. The water-cooled casing is the heat insulating sheath of the device.

The heater 2 contains spirals of the electric heater and the cooling system of the core with water and liquid nitrogen.

The cooling system consists of two parts: closed 12 and open 13. Liquid

Nitrogen is first run through the closed system of channels in the heater, and then the bunks and part of the unnapped nitrogen but the tube is injected into the cap 8, significantly speeding up the process of cooling and leveling the temperature of the core.

Heater 2 and base 1 of the screw. The contact surfaces are thoroughly lapped to improve the thermal contact.

K. Hemispheres and needles were soldered to contact plates 5, 6. Hemispheres provide self-installation of contact plates on the sample surface. For reduced thermal resistance of the contacting surfaces

hemispheres and racks 3, 4 are smeared with graphite.

3

Racks are made of one Gu1 material, identical in geometric dimensions and heat capacity. The upper part of the uprights on the hemispherical surface of the surface mates with the contact plates, and the 1 st part ends with 1 deep ribs, which are included in the recesses of the ground landing. The dilution of the uprights to the sides, but the installation of the specimen uses the arms of the uprights with springs (not shown in the drawing line). The sample is pressed against the contact plates by springs through levers and struts.

To ensure a minimum temperature difference between the base and the racks on the cap 8, a heater 9 is installed, which is operated by a temperature controller.

To eliminate scuffing when moving parts, the base and hemispheres are made of stainless steel X18H9T, and the pillars and cap are made of duralumin alloy. Contact plates are made of red copper and chromed.

For temperature measurements in the calorimeter, thermocouples with a diameter of 0.2 mm made of pycrome and Copstantan are used. The installation of thermocouples is constant (the places of termination of thermocouples A, B, C, D are shown in the drawing by crosses).

Thermocouples A and B are mounted in the needles of the contact plates 5, 6, and thermocouples C in the injection needle attached to the holder, which is screwed to the base. Thermocouple D is mounted in the outer cap, and thermocouple E is in rack 4. Thermocouple D and E are temperature control sensors that provide zero non-excess temperatures for the cap and racks.

In the experiment, the thermocouple heating delays are measured relative to the thermocouples L and S.

The coefficient of thermal diffusivity is calculated by the formula:

() .. about,,"( - - ;)

Ca

/ one

0.57f

Bi

R

at,. BUT

2.3

R

where a is the effective heat transfer coefficient on the side surface of the sample, W / M2. / C;

Biot Bi;

2 / and R is the thickness n the radius of the sample, m;

TSL TSA (O; (0 —the temperature of the heating of the thermocouple C is relative to that of the heating of the thermocouple LNV, ° C;

TO TO (O-correction on the contact resistance and nonidentity of thermocouple calibration (° C), is a "permanent instrument and is determined from a calibration test on a copper sample;

And - approximate value of thermal conductivity of the sample for this class of materials, w / m - / (;

P is the coefficient of linear expansion of the sample material (1 // C), determined approximately for a given class of materials. The device works as follows. Test specimen 7 is put on thermocouple C, previously lifted into the casing and extending the stand 3, 4 wedge. Then remove

the wedge from the groove of the struts and the calorimeter closed. A heater is turned on, and the core of the calorimeter is monotonously heated along with the sample. In this case, however, the average thermocouple monitors the temperature of the sample and measures the amount of heat generated by the average thermocouple relative to that of the thermocouples in the contact plates. Next, calculate the coefficient of thermal diffusivity.

Subject invention

An apparatus for measuring the thermal diffusivity of solid materials in monotonic heating mode, comprising

A split heat insulating jacket with a water-cooled jacket, a heater, a base, a cap, contact plates and three temperature sensors, characterized in that, in order to improve measurement accuracy,

Between identical contact plates, made in the form of hemispheres, and a base, two racks with spherical sockets in the upper part and deep ribs in the lower part, which are in contact with the corresponding edges of the base, are inserted.