SU949447A1

SU949447A1 - Method and device for measuring thermal physical characteristics

Info

Publication number: SU949447A1
Application number: SU792792418A
Authority: SU
Inventors: Виталий Васильевич Курепин; Семен Ефимович Буравой; Владимир Александрович Береговой; Владимир Гаврилович Карпов
Original assignee: Ленинградский технологический институт холодильной промышленности
Priority date: 1979-07-04
Filing date: 1979-07-04
Publication date: 1982-08-07

Description

Изобретение относитс к теплофизическому приборостроению и предназначено дл исследовани теплофизических характеристик твердых тел.The invention relates to thermophysical instrumentation and is intended to study the thermophysical characteristics of solids.

Известен способ определени теплофизических характеристик в режиме 4oнoтoннoгo разогрева образца, включающий использование двух образцов сравнени с известными теплофизическими свойствами, прижатых снаружи к поверхност м исследуемого образца 1.A known method for determining the thermophysical characteristics in the mode of 4-in-phase heating of a sample includes the use of two comparison samples with known thermophysical properties that are pressed from the outside to the surfaces of the test sample 1.

Недостатком способа вл етс необходимость симметрировани нагрева и ограничение точности вследствие погрешности значени теплофизических свойств образцов сравнени .The disadvantage of the method is the need for balancing the heating and limiting the accuracy due to the error in the value of the thermophysical properties of the comparison samples.

Устройство дл осуществлени указанного способа включает в себ рбойму дл пакета образцов, блок нагрева , термопары и систему регистрации температурных изменений.A device for implementing this method includes a housing for the sample packet, a heating unit, thermocouples, and a system for detecting temperature changes.

Наиболее близким к изобретению техническим решением вл етс способ измерени теплофизических характеристик образца, монотонно разогреваемого через одну из изотермических поверхностей при периодическом изменении теплового потока на другой по-. верхности с периодом, большим времени регул ризации температурного пол образца, включающий измерение теплового потока, температур в xapaicTepных сечени х образца, скорости измерени температуры и расчет характеристик по известным формулам 2J.The closest technical solution to the invention is a method for measuring the thermophysical characteristics of a sample monotonically heated through one of the isothermal surfaces with a periodic change in the heat flux to the other. surfaces with a period greater than the time required to adjust the temperature field of the sample, including the measurement of heat flux, temperatures in xapaicTep sections of the sample, the speed of temperature measurement, and the calculation of characteristics using the known formulas 2J.

Недостатком известного способа вл етс ограниченна точность вследствие того, что услови эксперимента на двух стади х испытани отличаютс от оптимальных.The disadvantage of this method is the limited accuracy due to the fact that the experimental conditions at two stages of testing differ from the optimal ones.

При реализации известного способа ближайшим техническим решением вл етс устройство дл измерени теплофизических характеристик, состо щее из разъемной теплозащитной оболочки, металлического дра, включающего нагревательный блок, контактирующий с основанием, на котором установлен When implementing the known method, the closest technical solution is a device for measuring thermal and physical characteristics, consisting of a detachable heat-shielding shell, a metal core, including a heating unit in contact with the base on which

20 тепломер, образец и пластинка, окруженные адиабатической оболочкой, две термопары в пластине и термопару в тепломере.20 heat meter, sample and plate surrounded by an adiabatic shell, two thermocouples in the plate and a thermocouple in the heat meter.

Цель изобретени - повышение точ25 ности.The purpose of the invention is to improve accuracy.

Поставленна цель достигаетс тем, что согласно способу измерени теплофизических характеристик образца, монотонно разогреваемого через одну The goal is achieved by the fact that, according to the method of measuring the thermophysical characteristics of a sample, monotonically heated through one

Claims

30 of isothermal surfaces with periodic variation of heat flux on another surface with periods of large time regulation of the temperature field of the sample, including measurement of heat flux, temperatures in characteristic sections of the sample, rates of temperature change and calculation of characteristics using well-known formulas, simultaneously with monotonous heating, the temperature drop on the sample is successively set to zero and 5-50 K, and the heat flux is measured on an isothermal surface subjected to monotonic heating eve. To implement the proposed method, a device for measuring thermal and physical characteristics consisting of a separable heat-shielding shell of a metal core including a heating unit, in contact with a base on which a heat meter, a sample and a plate are installed, surrounded by an adiabatic sheath two thermocouples in a plate and a thermocouple in a heat meter, In which a regulator is additionally installed, and a heater is installed in the plate, the thermo-napfci plates and the heat meter are switched on differentially and in series with the setting device Temperature fluctuations and a regulator connected to the plate heater. In addition, the diameter of the plate is pa. veins to the internal diameter of the adiabatic shell. FIG. Figure 1a shows the character of temperature variation on the faces of the sample t () and) and in its central section C (t;), and the thermal impact tax on one of the faces. The heat diagram of the proposed measurement method is shown in FIG. iff, where) and) are the heat fluxes on the edges of the sample with zero trans & de temperatures between them, (T) and qj (C) are the heat fluxes with a drop of 5-50 K on the Sample, 1 is sample 2 and 3 - Sampling contact surfaces of the measuring device. After regularizing the temperature field of the sample with a zero differential, a symmetric, parabolic temperature distribution is created in it, and the heat capacity and thermal diffusivity are measured, with a fixed differential, a parabolic temperature close to the linear temperature distribution and the thermal conductivity coefficient is measured. The design formulas for the characteristics determined in the experiment follow the solution of the heat conduction problem for a monotonically heated plate. These formulas, without taking into account the correction terms and contact resistance, have the form L cf Chg 2 (f + 0,5cmb -, -. -S -V--:. Where b dt / dT is the heating rate of the sample at the appropriate stage of the experiment, 2 ( f, S, m is the thickness and cross-sectional area, the mass of the sample. The method allows independent measurements of a, L, and E conditions that are optimal for each parameter, and the known ratio L asp is verifiable. Under conditions of strict symmetry, q qz Fig. 2 is a general view of the device according to the invention. The device comprises a detachable insulating sheath 1, load Equal unit 2, base 3, heat meter 4, sample 5, plate b, gradient 7 and adiabatic 8 heaters, thermocouples 9 and 10, systems 11 and 13 of automatic regulation, thermocouples 12, controlling the operation of the gradient heater. the heat meter 4 installs the test sample 5, then the plate b with the gradient heater 7 and lower the upper part of the insulating shell 1 together with the adiabatic shell 8. The equality of the diameters of the adiabatic shell and the plate with the heater allows Conditions in which the correction for heat transfer to the side surface of the sample is small: flows from. top and bottom contact surfaces compensate each. Sequential setting of zero differential and 5-50 K on the sample provides, in the first case, optimal accuracy conditions for heat capacity and thermal diffusivity, and, in the second case, for thermal conductivity. When determining the thermophysical characteristics, the calorimetric device is heated at a speed of about 0, 1 K / s using heater 2. To measure thermal conductivity on the regulator 13, the temperature difference of the upper plane of the sample relative to the lower 5-50 K is set. After measuring on the regulator 13 V Oh and there is a measurement of a and c. The circuit is then transferred back to measurement mode A by setting V to 5-50 K. The heat fluxes q entering. the sample, and q, coming out of the sample, are measured by a co-test of heat resistance meter 4, which is pre-calibrated (in particular, by a standard sample). The time of establishment of each mode is determined by the inertia of the top plate and the sample and, as the analysis shows, at the selected heating rate, measurements can be made every 5 K. The proposed method and device can be used in a comprehensive study of the thermal properties of thermal insulators and semiconductors with L 0 , 5-5 W / (m.K), as well as in the creation of industrial thermophysical devices. Claim 1. Method of measuring the thermophysical characteristics of a sample monotonically heated through one of the isothermal surfaces with a periodic change in heat flux on the other surface with a period longer than the temperature field of the sample, including measurement of the heat flux, temperatures in characteristic sections of the sample, velocity temperature changes and the calculation of the characteristics according to known formulas, characterized in that, in order to increase the measurement accuracy simultaneously with the monotonous roar, the temperature difference across the sample sequentially set to zero and 5-50 K, and the heat flow was measured on an isothermal surface being monotonic heating. 2. A device for measuring thermal characteristics according to claim 1, consisting of a separable heat-shielding shell, a metal core, including a heating unit in contact with the base, on which a heat meter, a sample and a plate are installed, surrounded by a shield-sheath, two thermogaps in the plate and a thermocouple in a heat meter, characterized in that a regulator is additionally installed, and a heater is installed in the plate, the thermocouple plate and the heat meter are connected differentially and in series with a differential temperature sensor urs and regulator connected to the heater plate. 3. The device according to claim 2, characterized in that the plate diameter is equal to the internal diameter of the adiabatic shell. Sources of information taken into account during the examination 1.Lykov AV, Auzrman L.Ya. Theory of drying. Pytsepromnzdat, 1946, p. 265.

2. Frayman Yu.E. Absolute method for complex determination of thermophysical characteristics. - Ing. Phys. journals 1964, t. 7, 10, p. 73-79 (prototype).

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