DETERMINATION OF THE TEMPERATURE CONDUCTIVITY COEFFICIENT a GRAPHICAL METHOD BASED ON NOMOGRAM FOR A SEMI-CONFINED ROD

Abstract

The article presents a technique and formula for calculating the thermal diffusivity of solids using nomograms of temperature changes. The paper describes a technique by which the final formulas are simplified to algebraic equations using the relative temperature θM of heating a semi-restricted rod from the end.Known equations for solving direct problems of heat conduction using regular modes of the 1-st, 2-nd and 3-rd kind, in which the final formulas are simplified.The article provides methods and formulas for calculating the coefficient of thermal conductivity using nomograms.The method uses the maximum of the first derivative of θM and tabular values of the function erf (1/(2 x Fo )), which is a solution to the direct problem of thermal conductivity. The temperature at a specific point of the rod is measured – x1 and time –τ1 with start of heatingent of thermal conductivity of solid bodies using nomograms of temperature changes.The work describes a method by which the final formulas are simplified to algebraic equations using the relative temperature θM of heating a semirestricted rod from the end. Known equations for solving direct heat conduction problems using regular regimes of the 1-st, 2-nd and 3-rd kind, in which the final formulas are simplified. In work Kondratiev H.M. notes: "The theory of the regular thermal regime is one of the sections of the study of heat transfer insolids. The theory of the regular mode considers the process of cooling or heating not throughout, but only at the stage that has ceased to be affected by the initial state of the body.In work of Lykov O.V. «Theory of thermal conductivity» the solution of the problem is done by three methods: classical, operational and the method of Fourier transformation. Not all methods of pulsed heating are related to these types of regular mode, but it can be used due to the simple form of the exponent. In this work, the proposed method does not belong to regular mode methods. It is done by solving the inverse problem with the help of a well-developed graphic nomogram.According to the accepted classification, the problem is solved under boundary conditions of the 1-st kind, in which the surface temperature is specified as a function of time. Considered a simpler case when surface of the bodyremains constant throughout the heat exchange process.This is achieved with the help of special devices that maintain a constant temperature of a semi-restricted rod with thermal insulation of the side surface.