The use of Karelia’s finelyground mining waste and local clay for production of heatinsulating materials

The results of the study of fine-grained feldspathic and talcchlorite waste from Republic of Karelia’s mining companies as a new mineral product for heat-insulating materials and stationary heat accumulators (fireplaces and furnaces) are reported. The physico-mechanical and thermal-physical properties of the materials, based on finely ground waste and local clay, are appraised. The materials produced from pegmatite waste are highly strong, and can be used for lining furnaces and fireplaces. Heat-insulating materials based on talc-chlorite waste have low thermal expansion at 20‒900 °C, their thermal resistance increases 9 times (at 980 °C, water) and their mechanical strength is 2,6 times higher than that of samples containing talcum powder.

Influence of Applied Frequency on Thermal Physical Properties of Coatings Prepared on Al and AlSi Alloys by Plasma Electrolytic Oxidation

In this study, plasma electrolytic oxidation (PEO) was performed on Al and AlSi substrates using a pulsed direct current (DC) power source. The coating process was carried out in a Na2SiO3 electrolyte with the systematic change of pulse frequency (50–1400 Hz). The surface characteristics of the coatings were examined using scanning electron microscopy (SEM). The phase structure was characterized using X-ray diffraction (XRD). A differential scanning calorimeter (DSC) and a laser flash apparatus (LFA) were employed to test heat capacity and heat conductivity, respectively. Results showed that as the discharge frequency increased, the thermal physical properties of Al-PEO and AlSi-PEO coatings changed in different ways. At a high frequency, Al-PEO coatings had low porosity and were closed-pore structured whereas AlSi-PEO coatings had high porosity and large-size open-pore structures could be observed on their surfaces due to concentrated discharges. Based on these findings, it was found that the thermal productivity of coatings is closely correlated with the open-/closed-pore structure instead of porosity. PEO coatings with low heat capacity or low heat conductivity could be obtained with a controlled frequency.

One-step coupled calculations (Serpent-OpenFOAM) for a fuel rod of the IPR-R1 triga reactor

In this work, a single step of coupled calculations for a fuel rod of IPR-R1 TRIGA was performed. The used me-thodology allowed to simulate the fuel pin behavior in steady-state mode for different power levels. The aim of this paper is to present a practical approach to perform coupled calculations between neutronic (Monte Carlo) and thermal-hydraulic (CFD) codes. For this purpose, is necessary to evaluate the influence of the water thermal-physical properties temperature variations on keff parameter. Besides that, Serpent Nuclear Code was used for the neutronics evaluation, while OpenFOAM was used for thermal-hydraulics. OpenFOAM si- mula-tions were made by using a modified chtMultiRegionFoam solver, developed to read Serpent output correctly. The neutronic code was used without any modifications. The results shows that this coupled calculations were consistent and that leads to encouraging further methodology development and its use for full core simulation. Also, the results shows good agreement with calculations performed using other version of OpenFOAM and Milonga as neutronic code.

Experimental Study of the Space–Time Effect of a Double-Pipe Frozen Curtain Formation with Different Groundwater Velocities

Groundwater velocity has significant effects on the formation of a frozen curtain during freezing. In order to study the influence of the velocity on a frozen curtain, a large physical model test platform was established for double-pipe freezing. Based on this platform, freezing tests for different velocities were carried out. Quartz sand was selected as a similar material. The freezing temperature of the saturated sand layer was found by analyzing the results of the nuclear magnetic resonance (NMR). Based on the study of the thermal physical properties of the sand layer, the freezing test results were analyzed, and the results showed that the flow led to the differential development of the temperature between the upstream and downstream sections of the freezing pipes. Moreover, the larger the velocity, the greater the difference. The flow prolonged the overlapping time of the frozen curtains. Additionally, the flow slowed down the development of the frozen curtain area and the frozen curtain thickness. The larger the flow velocity, the greater the inhibition of the flow on the development of the frozen curtain. The test results can provide more references for the design and construction of freezing engineering with flowing groundwater.

Method of operational life’s increasing of transport’s parts due to usage of coatings based on epoxy matrix modified by maleinic anhydride with improved thermal physical properties

The use of a new method of operational life increase of the transport means parts due to the introduction of polymer-based modified materials has been substantiated in the paper under discussion. It is shown that the use of matrices based on epoxy diane oligomers is quite promising direction in protective coatings formation. Some active additives have been applied to improve the properties of epoxy matrices on preliminary stage of their formation. The use of maleinic anhydride modifier containing active to the interphase interaction functional groups is promising as well. Epoxy diane oligomer has been used as the main component for the matrix in the composite formation. The hardener polyethelenepolyamine has been used to link the epoxy compositions enabling to harden the materials at room temperature. The choice of maleinic anhydride as a modifier to improve thermal-physical properties of the developed materials has been substantiated. It has been found that to form a composite material or a protective coating with improved thermal-physical properties it is necessary to apply maleinic anhydride as a modifier in epoxy matrix in the following ratio: q = 0,5 pts.wt. per q = 100 pts.wt. of epoxy oligomer ЕД-20. In this case the material has been formed where, comparing with nonmodified matrix, the indices of glass transition temperature are being increased from Тс = 327 К tо Тс = 335 К, heat resistance (by Martenson) from Т = 341 К to Т = 362 К, and thermal coefficient of linear expansion in the range of temperatures ∆Т = 303…423 К is being decreased from α = 9,9 ×10-5 К-1 to α = 4,4 ×10-5 К-1. It has been proved that the maleinic anhydride content in the matrix with its small fraction (q = 0,5 pts.wt.) has activated the processes of interphase interaction in epoxy CM structure formation, resulted in the increase of number of both physical and chemical bonds per polymer volume unit. This process will involve the increase of gel fraction degree in CM, and, correspondingly, both the cohesion and thermal-physical properties of modified CM have been improved. The developed material under discussion could be efficiently used as a matrix in formation of protective coatings which are to be operated under high temperatures conditions and dynamic or static loadings.

Связь механических свойств анизотропных материалов с их теплофизическими характеристиками на примере древесины сосны

The paper discusses experimentally found relation between mechanical an thermal physical properties of anisotropic materials observed at the pine wood (Pínus sylvéstris L). Hardness and main components of temperature diffusivity tensor measured at the normal to the fibers, tangential and radial faces of the pine wood sample having various moisture content can be linked with linear relations. It renders possible to make express estimation of anisotropic materials mechanical properties typically requiring labor and material extensive destructive testing by means of measurement of its thermal properties using dynamic thermography.

Prediction of the thermal conductivities of wood based on an intelligent algorithm

For thermal comfort and energy-saving performance, a floor-heating method is superior to conventional heating modes, e.g., radiator, fan coil, etc. The floor-heating method has been developed to be a primary indoor heating form. Wood is the most common floor surface material. Due to the anisotropy of wood, it is difficult to obtain a general theoretical formula for its thermal physical properties. In this paper, intelligent algorithms were adopted to predict thermal conductivities of wood. First, the study elaborated frequently used testing methods of thermal conductivity. Next, 130 types of common wood species were measured to form a database of thermal properties. With this database, intelligent algorithms were used to make predictions. For the thermal conductivity predictions that were conducted with support vector machine, the degree of fit between the predicted results and the measured results was not less than 0.87 (k-fold validation). This study validated the feasibility of the usage of the intelligent algorithm for the research and prediction of the thermal conductivities of wood.