SU773448A1

SU773448A1 - Heat flux sensor

Info

Publication number: SU773448A1
Application number: SU772555685A
Authority: SU
Inventors: Николай Васильевич Антонишин; Марк Абрамович Геллер; Анатолий Львович Парнас
Original assignee: Институт Тепло- И Массообмена Им.А.В.Лыкова Ан Белорусской Сср
Priority date: 1977-12-15
Filing date: 1977-12-15
Publication date: 1980-10-23

Description

1one

Изобретение относитс к устройствам дл измерени тепловых потоков и может быть использовано в теплометрии , в особенности в энергетике.The invention relates to devices for measuring heat fluxes and can be used in calorimetry, especially in power engineering.

Известны приборы, .использующие в 5 качестве чувствительного элемента биметаллическую пластину, деформаци изгиба которой служит мерой теплового потока 1. В этих приборах деформаци изгиба закрепленной биметал-10 лической пластины зависит от величины ее абсолютной температуры, геометрических размеров, а также от степени различи термических и механических свойств металлов, из которых (5 выполнена пластина.Instruments are known that use a bimetallic plate as a sensitive element, whose bending deformation serves as a measure of heat flow 1. In these devices, the bending deformation of a fixed bimetal-10 faceplate depends on the magnitude of its absolute temperature, geometrical dimensions, and mechanical properties of metals, of which (5 is made plate.

Наиболее близким по технической сущности к предлагаемому вл етс датчик теплового потока, содержащий корпус, вмонтированный в него 20 чувствительный элемент в виде свободнодеформируюшейс пластины и измеритель деформации чувствительного элемента, пропорциональной величине теплового потока 2. 25The closest in technical essence to the present invention is a heat flux sensor, comprising a housing, a 20 sensing element built into it in the form of a free deforming plate and a strain gauge of the sensing element proportional to the heat flux 2. 25

Работа устройства основана на способе измерени:. величины теплового потока по деформации изгиьа свободнодеформирующейс пластины. Прогиб такой свободнодеформирующейс пластины ЗОThe operation of the device is based on the measurement method :. heat flux rates by deformation of the bend of a free-deforming plate. Deflection of such free deforming plate AOR

не зависит от величины абсолютной температуры, а только от перепада температуры по ее сечению, коэффициентов -теплопроводности и температурного расширени , геометрического размера . Прогиб пластины не зависит также от ее толщины и механических свойств.does not depend on the magnitude of the absolute temperature, but only on the temperature difference over its cross section, the coefficients of thermal conductivity and thermal expansion, and its geometric size. The plate deflection does not depend on its thickness or mechanical properties either.

Недостатком такого прибора вл етс невозможность его работы при измерении тепловых потоков в агрессивных средах, когда на поверхности пластины образуетс устойчива окисна пленка. В этих случа х свободнодеформирующа с пластина становитс биметаллической и ее показани завис т от разницы в коэффициентах линейного расширени пластины и пленки, их геометрических размеров и механических свойств.The disadvantage of such a device is the impossibility of its operation when measuring heat fluxes in corrosive media, when a stable oxide film is formed on the surface of the plate. In these cases, the free-deforming plate becomes bimetallic and its readings depend on the difference in the linear expansion coefficients of the plate and film, their geometrical dimensions and mechanical properties.

Цель изобретени - увеличение точности и надежности измерени .The purpose of the invention is to increase the accuracy and reliability of measurement.

Эта цель достигаетс тем, что пластина выполнена из трех слоев, причем толщина слоев определ етс из услови отсутстви изгиба при изотермическом нагревеThis goal is achieved by the fact that the plate is made of three layers, and the thickness of the layers is determined from the condition that there is no bending during isothermal heating.

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Claims

- TYa y - transverse coordinate,), fuij ,,, „- Poisson's coefficients; . EG, are the elastic moduli of the layers; p a “b / b, 1 + ..„ - “is the plate thickness; n is the number of layers; h, h,. . .h - thickness of the layers of the plate. Layers of the plate, located symmetrically with respect to the central plane of the plate, have the same thickness and are made of the same material. The distances p and q determine the position of the neutral axis of the multilayer plate and are subject to the condition that the algebraic sum of the longitudinal forces in the plate is zero t. -v gli: Iy y, ..-: t: b yp-h, -t For practical purposes, in most cases it is sufficient to use a three-layer plate with outer layers made of materials resistant to the corrosive or erosive influence of the external environment. For a three-layer plate, the condition of the absence of bending is simplified and looks like,.,), (I - i)))) () t, 1n. where d, .dj.d, are the coefficients of thermal expansion of the layers. If the number of layers of the plate is odd and the layers located symmetrically but on both sides of the central layer are the same in size and properties (for example, they are made of the same material), then the condition of no bending during isothermal heating is performed automatically with frontal plate thicknesses. The drawing shows the proposed sensor. The device contains a sensitive element 1, which is made in the form of a round three-layer plate. In the sensor case 2, there is a round hole with an annular groove 3 in which the sensing element is embedded. To create tightness, flexible gaskets 4, for example of paralon, are inserted between the casing and the sensing element. The measurement of the deflection of the plate 1 under;, by the action of the heat flux, is carried out, for example, by an optical-optical interferometer or any other device 5 of a similar purpose. The heat flux falls onto plate 1, the trap is cooled, for example with air or water. Since gaps are left between the sensor body and the plate, the plate can freely deform in the working temperature range. Isothermal heating of the plate does not create a deflection. The bending of the plate occurs only due to the temperature differential over its cross section. The flexural strain of the plate is measured by instrument 5 and the heat flux is calculated from it. Additional insignificant stiffness introduced by flexible pads can be taken into account by preliminary calibration. The effect of the dependence of the thermophysical characteristics of the plate on temperature can also be taken into account by pre-calibrating the sensor or eliminated by stabilizing the temperature of the plate by cooling it. Claim 1. A heat flux sensor comprising a housing, a sensing element embedded in it in the form of a free-deforming plate and a strain gauge of the sensitive element proportional to the heat flux, characterized in that the plate is made of three layers to increase the accuracy and reliability of the measurement , the thickness of the layers is determined from the ratio 1-H.), (o., - d,). Ctiib-rX i - bXi-MO. E-b, where h,, h, j, h are the thicknesses of the layers; E, Er, Ej are the elastic moduli of the layers; di, d2.dij — coefficients of temperature expansion of the layers; . L - Poisson's coefficients. 2. The device according to claim 1, characterized in that the layers of the plate located symmetrically with respect to the central plane of the plate have the same thickness and are made of the same material. Sources of information taken into account in the examination 1.G.A. Geraschenko Basics of heat metering. K., 1971, p.15.

2. USSR author's certificate number 600402, cl. G 01 Z 5/38, 1976 (prototype).