Advanced Materials Research Vol. 1126

Abstract: The paper features the mathematical model of analytical calculation of thermodynamic properties like viscosity, speed of sound and thermal conductivity for fluids in one and two-phase region (fluid-solid, fluid-gas) on the basis of statistical mechanics. For the calculation of thermal conductivity and viscosity for fluids will be presented Chung-Lee-Starling model Equations for the thermal conductivity are developed based on kinetic gas theories and correlated with the experimental data. The low-pressure transport properties are extended to fluids at high densities by introducing empirically correlated density dependent functions. These correlations use acentric factor, dimensionless dipole moment and an empirically determined association parameters to characterize molecular structure effect of polyatomic molecules. The calculation of thermodynamic properties for fluids was developed under the theory of statistical thermodynamics and statistical associated fluid theory. For the calculation of thermal conductivity of solids are the most important two contributions: the heat transport by electrons (el) and by phonons (ph). In our model we have made the assumption that heat transport by electrons and by phonons is independent and the thermal conductivity is than a sum of both terms.

Abstract: The paper explains the nature of mid-gap absorption, amplification effect of photoluminescence (at mid-gap absorption), the mechanism of the ESR signal in chalcogenide glasses, as well as correlations between these phenomena, based on the barrier-cluster-heating model. It also discusses the mechanism of photo-induced structural changes, which play an important role in the application area.

Abstract: Recently the physical model for the temperature field generated by thermophysical single-probe sensor in a shape of planar disc has been derived. The model accounts cylindrical sample having final radius and infinite length. The prototype of measuring electronics RTA was build that operates with auto balancing bridge. For the measurements the single-transition method is used. While the measurement error of the temperature response measured by thermocouple was 1% at the height of temperature response 1°C, the sensitivity of the measurement with the automatically balanced bridge is better and the signal to noise ratio is improved about 10 times. The measuring electronics was tested for measuring the temperature response using a single-sensor. This sensor generates the heat pulse and sense the temperature response in the same time. The next advantage is that the temperature response to the generated step-wise pulse is much smaller and it can be reduced to the level of 1-8° C compared to stationary method like guarded hot plate method. The effect of the temperature field generated by the probe is much smaller, which in the case of measurement of porous materials at the presence of moisture is beneficial, as the resulting redistribution of moisture under the created temperature gradient is negligible. There were derived basic models for the evaluation of this type of experiment. The probe should be in form of full cylinder or an annulus. The derived temperature function counts the outer and inner diameter of annulus. Putting the inner radius to zero we get the solution for full circle probe, so the model is universal. The model counts also the heat losses from the outer surface of the sample, when the time of measurement exceed the time when the penetration depth of generated heat pulse rich the outer radius of sample. The estimated output parameters from single measurement are the thermal conductivity, thermal diffusivity and specific heat. The heat transfer coefficient is additional parameter fitted as free parameter of the model.

Abstract: In situ analysis of hygrothermal state of the Sedlec Ossuary, Czech Republic, is presented in the paper. Within the experimental analysis, the measurement of moisture distribution in several profiles of historical masonry is done on a gravimetric principle. Non-destructive measurement of moisture content on the wall surface is done as well, using a capacitive moisture meter. Moreover, the interior and exterior climate is monitored over an almost two year period. On the basis of the obtained experimental results the hygrothermal conditions in both the masonry and the interior are assessed, including the identification of main moisture sources.

Abstract: Temperature wave method is a quasi-stationary method for measuring thermal diffusivity of a substance. Method of plane temperature waves is a derivative of temperature wave method based on the notion of applying heat flux to first side of a sample and measuring temperature fluctuation on the second side of a sample. Changing temperature wave frequent allows us to enter adiabatic regime. Considering that phase of heat flux is known, the only parameter to be measured is phase of temperature changes on the second side of a sample relative to the phase of heat flux, which (in adiabatic regime) gives us thermal diffusivity.

Abstract: Wider application of commercially produced phase change materials in production of building composites is limited due to their higher price and the inert polymer encapsulation which negatively affects mechanical parameters. This paper is focused on preparation of the composite material for energy savings. The phase change composite is prepared by soaking palm wax into the structure of diatomite powder using vacuum impregnation method. The compatibility of diatomite and palm wax in a newly developed PCM structure is investigated by FTIR spectroscopy. The improved thermal storage properties obtained by DSC analysis reveal melting temperature at 55.9°C and the phase change latent heat of 78.0 J/g. The laser diffraction based devise is used to determine the particle size distribution in order to assess the suitability of the developed wax/diatomite based composite for the cement based building materials. The obtained results indicate promising results from the point of view of improved latent heat storage at reasonable cost.

Abstract: It is an important issue to preserve the cultural assets on open exhibition. Usually, the remains are buried in the ground for preservation after an archaeological excavation in Japan. Today, however, a part of the remains of Heijyo-kyu palace site in Nara, Japan is exhibited in the excavation site exhibition hall. Although the exhibition hall was built for protecting the remains from the external impacts, the deterioration has been confirmed such as soil erosion, salt crystallization and the growth of the bryophytes. In this study, we examined the deterioration of the remains and measured temperature and humidity in the exhibition hall. We also simulated the illuminance distribution in the exhibition hall in order to clarify the effect of the daylight on the growth of the bryophytes.

Abstract: The texture in illite-based ceramics was introduced by spreading a large number of thin layers of a wet plastic mass one on top of the other. The basal planes of the plate-like illite crystals are predominantly oriented parallely with the direction of spreading. The samples were fired at different temperatures ranging from room temperature up to 1100 °C with a heating rate of 5 °C/min, then freely cooled and measured at room temperature. We determined Young modulus (E), thermal diffusivity (a) and relative dimension changes (Δl/l₀) in two directions: parallely to the basal planes (a subscript ||) of the illite crystals and perpendicularly to these planes (a subscript ⊥). It was found that the ratio E_|| / E_⊥ ≈ 2.9 and a_|| / a_⊥ ≈ 2.0 up to 900 °C. Above 900 °C, the values of E and a increase due to sintering, and the differences between the values measured in the two directions decrease. In the case of the thermal diffusivity these differences do not disappear even after firing at the temperature of 1200 °C.

Abstract: European directive on energy performance of buildings (2010) and related national technical rules force reduction of energy consumption of both new and reconstructed buildings due to the so-called passive standard. Consequently the thermal design of such buildings, utilizing advanced materials, structures and technologies, requires proper analysis of relevant physical processes, unlike classical evaluations of thermal resistance from one-dimensional stationary heat conduction. The paper demonstrates a possibility of compromise between complicated multi-physical models and realistic thermal estimation of buildings, as well as some optimization procedures in building design leading to energy reduction.