Consideration of the procedural error for measuring contact sensor temperature during thermophysical studies

Abstract

The procedural error is described for measuring the temperature of a contact sensor with placement within the grooves of an experimental specimen made of ceramic material. Mathematical modelling is performed for the error under specimen one-sided heating conditions. The effect is demonstrated for the error on the result of processing experimental data by means of mathematical processing of nonstationary nonlinear reverse thermal conductivity problems. Recommendations are given for reducing this error.Keywords: procedural error for measuring temperature (PEMT), contact sensor for measuring temperature, thermophysical properties (TPP), reverse thermal conductivity problem (RTP), thermocement based on water glass.In order to plan rocket and space equipment construction it is necessary to have data about the thermophysical properties (TPP) of materials over a wide temperature range. Uncertainty of data about material TPP may lead to an error in design, going beyond permissible temperature limits and loss of operating capacity for onboard equipment and instruments.Recently there has been widespread use of methods for determining TPP in which experimental data are processed by means of software for non-stationary non-linear reverse thermal conductivity problems (RTP) [1]. In processing experimental data it is particularly important to have accurate determination of the temperature field for a material specimen [2]. With use of the most widespread sensors (thermocouples) the procedural error for temperature measurement (PETM) arises due to different optical and thermophysical properties of the specimen sensor material, heat flows through electrodes, contact resistance in the zone of sensor installation, etc.Publications [3 -8] have been devoted to a method for determining the PETM. Before the widespread use of personal computers the error was predominantly determined in analytical form different methods of placing (fixing) sensors and temperature regimes. As a result of this complex dependences were obtained within which there are also such interconnected values as the rate of change in temperature, dimensions, thermophysical and optical properties of test material, and also materials for fastening a sensor and sensor material itself. Practical use of analytical dependences was limited due to the considerable number of functions, simplifying mathematical description of the actual thermophysical processes. In practice only a qualitative estimate of this error was limited, and often it was ignored.With widespread use of personal computers and development of programs for modelling heat exchange processes such as ANSYS, NASTRAN, etc., the situation has changed fundamentally. Work has appeared within which attempts have been made to consider PETM on a real time scale. However, the correctness of methods for fixing heat sensors, properties of the materials used for mounting them, the nature of heat exchange in a complex specimen -temperature sensor system, have not yet been studied sufficiently.The aim of this work included ...

Determination of necessary time of measurements of surface thermocouples depending on conditions of technological processes

“…1a) in case of = 1. The value 0.2 was accepted as minimum because in practice of thermocouple maintenance even in case of the long operation terms and mechanical damages the lowering of to such values is improbable [1][2][3][4][5][6][7].…”

“…Nowadays, temperature measurements are used for control and condition monitoring of technological equipment and quality of technological process behavior in all industries. Such as [1][2][3][4] metallurgy, power engineering, aircraft industry, and also medicine, fire safety [5,6] and other person focus areas are among such productions.…”

“…A fairly large number of works (for example, [2,3,[9][10][11]) was devoted to the solution of such problems with use of balance approaches and methods. The results of the adjoint heat transfer problem solutions taking into account real operating conditions of thermocouple practically are not present.…”

Research of the thermal contact conditions influence on the results of superficial thermocouples measurements

“…;, r rR TT == (6) где T r -температура нагревательного элемента. Граничные условия на оси симметрии r = 0:…”

“…При этом для многих предприятий, как правило, контроль температуры играет определяющую роль в обеспечении качества технологических процессов и технико-экономических показателей производства в целом. Особенно следует выделить такие направления, как энергетика, металлургия, машиностроение [3][4][5], а также пожарная безопасность, медицина [6][7][8] и другие.…”