Analysis of temperature measuring error in high-temperature ceramic samples with various methods of thermocouple fixing

The evaluation of methodological errors in measuring the temperature of nitride ceramics under unilateral heating by high-intensity heat flow was carried out. Simulation of thermal processes in the temperature sensor — sample system was performed using the Siemens PLMNX program. Various methods of fixing platinum-rhodium thermocouples with a diameter of 0.1 mm on the surface and inside the samples have been investigated. The regularities of the influence of the size of the hot junction, the presence of thermal cement, the shape of the grooves for fixing thermocouples on the methodological error of temperature measurement were investigated. Significant errors were revealed when installing thermocouples on the surface of the sample without violating its integrity. Recommendations for the installation of thermocouples were given. The results of the paper can be useful in the preparation of experimental samples for thermal tests on radiation heating stands.

The study of the destruction of heat-resistant chamotte concrete during its sharp heating and cooling

The article investigates the destruction of heat-resistant chamotte concrete of various classes: low-cement and medium-cement with the addition of quartz sand (to increase alkaline resistance) and with the addition of metal fiber (to reduce cracking) after exposure to thermal shock. Two methods for determining the heat resistance of concrete were used, in which the destruction of the material was evaluated using ultrasound using the method of a water-cooled plate and the method of one-sided heating-cooling. Studies conducted using the method of unilateral heating-cooling, revealed the formation of macrocracks in samples of low cement concrete. This method turned out to be more sensitive when evaluating concrete destruction.

New Models of Droplet Deposition and Entrainment for Prediction of Dryout in Uniform and Non-Uniform Heated Annuli

In this paper, we present a phenomenological modeling of annular flow for dryout prediction in vertical annuli by adopting a new set of correlations of droplet deposition and entrainment. The performance of the new correlations is tested by using the experimental data of Becker and Letzter [1] measured in a 3000mm annulus under bilateral as well as unilateral heating conditions, and the experimental data of Becker et al. [2] obtained in a 3650mm long annulus in respect of eight different axial heat flux profiles. The applicability of two widely used correlations of droplet deposition and entrainment in annuli which were derived from flows in vertical tubes was also checked. It was shown that large discrepancies were observed for the tube-based correlations, while for our present model the predicted CHFs as well as the positions of dryout occurrence in the case of non-uniformly heated annuli agree well with the experimental data.

Numerical Approach for Computation of the Heat and Heat Flux for Covering of the Emission in the Surrounding Air of Subjected to Unilateral Heating Flat Wood Details before their Bending

A numerical approach for the computation of the specific (for 1 m2) energy consumption, qe, and the specific heat flux, dqe/dτ, needed for covering of the emission in the surrounding environment of the subjected to unilateral heating flat wood details aimed at their plasticizing and following bending has been suggested. The approach is based on the integration and differentiation of the solutions of a linear model for the calculation of the non-stationary 1D temperature distribution along the thickness of subjected to unilateral heating flat wood details, suggested by the authors earlier.For the numerical solution of the model aimed at the determination of qe and dqe/dτ software program has been prepared, which was input in the calculation environment of Visual Fortran. Using the program, computations have been carried out for the determination of the change in the energy qe and in the flux dqe/dτ, which are consumed by spruce details with an initial temperature of 20 °C, moisture content of 0.15 kg·kg-1, and thicknesses of 6 mm, 8 mm, and 10 mm during their 10 min unilateral heating at temperatures of the heating metal band of 100 °C, 120 °C, and 140 °C and of the surrounding air of 20 °C. The obtained results are graphically presented and analyzed.