Main goal of the paper is to present the algorithm serving to solve the heat conduction inverse problem. Authors consider the heat conduction equation with the Riemann-Liouville fractional derivative and with the second and third kind boundary conditions. This type of model with fractional derivative can be used for modelling the heat conduction in porous media. Authors deal with the heat conduction inverse problem, which, in this case, consists in identifying an unknown thermal conductivity coefficient. Measurements of temperature, in selected point of the region, are the input data for investigated inverse problem. Basing on this information, a functional describing the error of approximate solution is created. Minimizing of this functional is necessary to solve the inverse problem. In the presented approach the Ant Colony Optimization (ACO) algorithm is used for minimization.

In this study, agar-based nanocomposite films containing ultra-porous silica aerogel particles were fabricated by gel casting using an aqueous agar/silica aerogel slurry. The silica aerogel particles did not show significant agglomeration and were homogeneously distributed in the agar matrix. Transmission electron microscopy observations demonstrated that the silica aerogel particles had a mesoporous microstructure and their pores were not incorporated into the agar polymer molecules. The thermal conductivities of the agar and agar/5 wt.% silica aerogel nanocomposite films were 0.36 and 0.20 W·m–1·K–1, respectively. The transmittance of the agar films did not decrease upon the addition of silica aerogel particles into them. This can be attributed to the anti-reflection effect of silica aerogel particles.

The article presents the prototype of a measurement system with a hot probe, designed for testing thermal parameters of heat insulation materials. The idea is to determine parameters of thermal insulation materials using a hot probe with an auxiliary thermometer and a trained artificial neural network. The network is trained on data extracted from a nonstationary two-dimensional model of heat conduction inside a sample of material with the hot probe and the auxiliary thermometer. The significant heat capacity of the probe handle is taken into account in the model. The finite element method (FEM) is applied to solve the system of partial differential equations describing the model. An artificial neural network (ANN) is used to estimate coefficients of the inverse heat conduction problem for a solid. The network determines values of the effective thermal conductivity and effective thermal diffusivity on the basis of temperature responses of the hot probe and the auxiliary thermometer. All calculations, like FEM, training and testing processes, were conducted in the MATLAB environment. Experimental results are also presented. The proposed measurement system for parameter testing is suitable for temporary measurements in a building site or factory.

The article presents a novel method that allows measurement of thermal conductivity that is based on Stefan-Boltzmann law. The developed method can be used to determine thermal conductivity of ceramic investment casting molds. The methodology for conducting thermal conductivity tests of ceramic material samples is presented. Knowledge of the value of thermal capacity and thermal conductivity as a function of temperature enables computer simulations of the process of cooling and solidification of liquid metal in a mold.

In the present article, we introduced a new model of the equations of general ized thermoelasticity for unbounded orthotropic body containing a cylindrical cavity. We applied this model in the context of generalized thermoelasticity with phase-lags under the effect of rotation. In this case, the thermal conductivity of the material is considered to be variable. In addition, the cylinder surface is traction free and subjected to a uniform unit step temperature. Using the Laplace transform technique, the distributions of the temperature, displacement, radial stress and hoop stress are determined. A detailed analysis of the effects of rotation, phase-lags and the variability thermal conductivity parameters on the studied fields is discussed. Numerical results for the studied fields are illustrated graphically in the presence and absence of rotation.

By simulating the actual working conditions of a cable, the temperature variation rule of different measuring points under different load currents was analyzed. On this basis, a three-dimensional finite element model (FEM) was established, and the difference and influence factors between the simulation temperature and the experimental measured value were discussed, then the influence of thermal conductivity on the operating temperature of the conductor layer was studied. Finally, combined with the steady-state thermal conductivity model and the experimental measured data, the relation between thermal conductivity and load current was obtained.

The work presents results of research on the influence of micro materials on the thermal conductivity λ of gypsum. In the research, cellulose-based polymer and aerogel were used as the modifying micro materials. For the purpose of measuring the thermal conductivity, a non-stationary method was used based on the “hot wire method”. A very precise set of devices for measuring and recording the temperature of the heating wire was used. In the presented solution, a single measurement took only one minute. Measurements were recorded with the help of a computer measuring system, with a sampling time of 0.01s. During the 60-second-long test, 6000 measurements of the heating wire temperature were collected. A decrease of the thermal conductivity and density of hardened gypsum with added micro materials was observed due to modifications of the structure of the final product. Experimental values of the thermal conductivity of the gypsum specimens with the addition of polymer and aerogel were respectively over 23% and 6% lower than the non-modified gypsum specimen.

In this study, we investigated the effect of Fe addition (0, 0.25, 0.50 and 0.75 wt.%) on the microstructure, mechanical properties and electrical conductivity of as-cast and as-extruded Al-RE alloys. As the Fe element increased by 0 and 0.75wt.%, the phase fraction increased to 5.05, 5.76, 7.14 and 7.38 %. The increased intermetallic compound increased the driving force for recrystallization and grain refinement. The electrical conductivity of Al-1.0 wt.%RE alloy with Fe addition decreased to 60.29, 60.15, 59.58 and 59.13 %IACS. With an increase in the Fe content from 0 to 0.75 wt.% the ultimate tensile strength (UTS) of the alloy increased from 74.3 to 77.5 MPa. As the mechanical properties increase compared to the reduction of the electrical conductivity due to Fe element addition, it is considered to be suitable for fields requiring high electrical conductivity and strength.

Heat and mass transfer stretched flow of an incompressible, electrically conducting Jeffrey fluid has been studied numerically. Nanoparticles are suspended in the base fluid and it has many applications such as cooling of engines, thermal absorption systems, lubricants fuel cell, nanodrug delivery system and so on. Temperature dependent variable thermal conductivity with Rosseland approximation is taken into account and suction effect is employed in the boundary conditions. The governing partial differential equations are first transformed into set of ordinary differential equations using selected similarity transformations, which are then solved numerically using Runge-Kutta-Felhberg fourth-fifth order method along with shooting technique. The flow, heat and mass transfer characteristics with local Nusselt number for various physical parameters are presented graphically and a detailed discussion regarding the effect of flow parameters on velocity and temperature profiles are provided. It is found that, increase of variable thermal conductivity, radiation, Brownian motion and thermophoresis parameter increases the rate of heat transfer. Local Nusselt number has been computed for various parameters and it is observed that, in the presence of variable thermal conductivity and Rosseland approximation, heat transfer characteristics are higher as compared to the constant thermal conductivity and linear thermal radiation.

In this study, a new laser flash system was proposed for the determination of the thermal conductivity of brown coal, hard coal and anthracite. The main objective of the investigation was to determine the effect of coal rank, composition, physical structure and temperature on thermal conductivity. The solid fuels tested were medium conductors of heat whose determined thermal conductivities were in the range of 0.09 to 0.23 W/(m K) at room temperature. The thermal conductivity of the solid fuels tested typically increased with the rank of coal and the measurement temperature. The results of this study show that the physical structure of solid fuels and temperature have a dominant effect on the fuels' thermal conductivity.

The aim of this work is the development of Cu-Al2O3 composites of copper Cu-ETP matrix composite materials reinforced by 20 and 30

vol.% Al2O3 particles and study of some chosen physical properties. Squeeze casting technique of porous compacts with liquid copper

was applied at the pressure of 110 MPa. Introduction of alumina particles into copper matrix affected on the significant increase of

hardness and in the case of Cu-30 vol. % of alumina particles to 128 HBW. Electrical resistivity was strongly affected by the ceramic

alumina particles and addition of 20 vol. % of particles caused diminishing of electrical conductivity to 20 S/m (34.5% IACS). Thermal

conductivity tests were performed applying two methods and it was ascertained that this parameter strongly depends on the ceramic

particles content, diminishing it to 100 Wm-1K-1 for the composite material containing 30 vol.% of ceramic particles comparing to 400

Wm-1K-1 for the unreinforced copper. Microstructural analysis was carried out using SEM microscopy and indicates that Al2O3 particles

are homogeneously distributed in the copper matrix. EDS analysis shows remains of silicon on the surface of ceramic particles after

binding agent used during preparation of ceramic preforms.