Temperature State of the Layer of Translucent Material with Depending on Temperature Thermal Conductivity and Absorption of Penetrating Radiation

The results of experimental and theoretical studies of the temperature state of the high- pressure cylinder (HPC) of the T-100-130 steam turbine for one of the start modes are presented. Taking into account the dependence of the coefficient of linear expansion on the temperature, the elongations of the individual sections of the casing under different temperatures and its total elongation after the turbine operation starts to correspond to the stationary operation mode have been found. The studies have shown that in the process of actuation the turbine there is a significant difference in temperature along the length of the HPC casing. In this case, the most intense heating occurs in the area from the second to the sixth section. The greatest temperature difference was observed in stationary operation at maximum temperature in the fifth section. Using the orthogonal method of L. V. Kantorovich, an approximate analytical solution of the thermal conductivity problem for a two-layer wall (turbine casing – thermal insulation) under inhomogeneous boundary conditions of the third kind is obtained. With the use of experimental data on the temperature state of the outer surface of the casing of the HPC by solving the inverse problem of thermal conductivity, the average heat transfer coefficients for the actuation period characterizing the intensity of heat transfer from steam to the casing have been found. On the basis of experimental data on the temperature change of any of the controlled parameters of the turbine over time, a theoretical method for predicting its change in a certain time range from the time of the its last measurement has been developed. The use of this method to predict the change in the temperature difference between the top and bottom of the HPC casing during the actuation showed that for a period of time equal to 3–5 minutes the forecast is fulfilled with high reliability.

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Conditions for a Thermal Explosion in the Plate under Convective-Radiation Heat Transfer

Herald of the Bauman Moscow State Technical University Series Natural Sciences ◽

10.18698/1812-3368-2020-6-48-59 ◽

2020 ◽

pp. 48-59

Author(s):

V.S. Zarubin ◽

G.N. Kuvyrkin ◽

I.Yu. Savelyeva ◽

A.V. Zhuravsky

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Energy Release ◽

Thermal Explosion ◽

Radiation Heat Transfer ◽

The Body ◽

Radiation Heat ◽

Temperature Dependent ◽

Temperature State ◽

The Stability

The processes of obtaining and storing energy-saturated substances are characterized by energy release in their volume. The intensity of this energy release increases with increasing temperature. The stability of the stationary temperature state of a solid with a temperature-dependent intensity of volumetric energy release is directly related to the conditions of heat transfer of this body with the environment. If the heat energy released in the volume of the body can no longer be diverted into the environment, the steady temperature state of the body becomes impossible. The paper studies the conditions for a thermal explosion in a solid in the form of a plate with a temperature-dependent coefficient of thermal conductivity and convective-radiation heat transfer on its surfaces. The statement of the nonlinear problem of steady-state thermal conductivity in the plate is represented by a system of integral relations. The limits of integration of the integrals included in these relations are the desired functions and parameters which determine the temperature state of the plate. A quantitative analysis of these relationships makes it possible to establish the influence of the parameters which determine the intensity of heat transfer and the dependence of the thermal conductivity of the plate material on the conditions for a thermal explosion with an arbitrary law of variation with temperature of the volumetric power of the energy release in the plate. The results of such an analysis are presented in the framework of a one-parameter model of the stationary theory of thermal explosion

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