Abstract
Numerous studies show that non-destructive testing methods satisfy most of the requirements of technical diagnostics of heating networks and technological facilities. Methods of non-destructive testing are based on the observation and automated registration of the temperature state of processes. The developed device is designed to analyze the state of thermal insulation of underground pipelines. The development and research of devices for measuring heat flow requires mandatory consideration of the temperature field of the sensing element, i.e. solutions of the differential equation of thermal conductivity for a body of a certain shape under given boundary conditions. In general, the sensing elements are multi-layered: black coating, calorimetric load, heat-sensitive elements, alternating lacquer and adhesive layers, i.e., the sensing elements are heterogeneous, both in the direction perpendicular to the irradiated surface and in parallel. The heterogeneity in the first case is due to the multi-layering of the sensing element. The article describes solutions to the thermal conductivity equation describing the temperature field of a sensitive element in the form of a hemisphere and a spherical zone, due to the nonequivalence of heat losses during irradiation and calibration by electric current. Taking into account this systematic error makes it possible to increase the accuracy of measuring the energy parameters of radiation. These solutions of the equations formed the basis of the design of the device for measuring heat flow.