Application of a Novel Method for a Simulation of Conductivity of a Building Material in a Climatic Chamber

This work proposes the application of a new simulation method based on fractal geometry for the calculation of the thermal conductivity for building materials. The results obtained are compared with the measurement, in a climatic chamber, of the heat flow through a material chosen as the sample. The test sample is made with “pietracantone”, a stone widely used as a building material and as an ornamental stone in the areas of Cagliari and Sassari in Sardinia. This material is characterized by a limestone matrix and a porosity which significantly influences the value of thermal conductivity. It is not known to the authors that this material had already been studied for its thermal propertie

Intermingled fractal units model and electrical equivalence fractal approach for prediction of thermal conductivity of porous materials

The effective thermal conductivity of porous materials is a function of the intrinsic characteristic of the solid and the fluid phases that occupy the pores, of the volume fraction of the pores, and of their dimensional distribution. This last aspect is less known and studied than the others because the porous microstructure is difficult to define in conventional geometric terms. In this work, an Intermingled Fractal Units model (denominated IFU) is presented, developed by varying some constructive aspects of the Sierpinski carpet. Simple fractals can be used effectively to describe pore size distributions which present a regular growth toward the larger diameters and therefore are not suited to describe very common structures which present one or more peaks in their distribution. But the use of more fractal units means that the IFU is able to effectively simulate the pore size distribution, the volume fractions of the voids as well as the geometry of the microstructure of non-fractal porous materials. By turning IFU model into electrical fractal pattern, it is possible to calculate effective thermal conductivity of the materials. In this approach the value of effective thermal conductivity coefficient derived from the nth stage was used as a default value for the solid phase in the nth + 1 step. This full fractal procedure has been verified with deterministic or random fractal models as well as with some porosity–conductivity experimental data, namely, those obtained from advanced ceramics (Yitria stabilized zirconia) already available in the scientific literature and the results are comparable and very close

Il manuale tematico della terra cruda

Il manuale tematico della terra cruda integra il manuale del recupero delle architetture in terra cruda. Tratta di un insieme di argomenti che convergono tutti sull'obiettivo della maggior comrensionedel comportamento e dell'uso del materiale terra e del suo reingresso nel quadro delle pratiche edilizie corrent

An intermingled fractal units model to evaluate pore size distribution influence on thermal conductivity values in porous materials

The modeling of the microstructure of the materials is growing. Several studies have shown that fractal geometry is a tool that can replicate and investigate the nature of the materials and their physical properties. In particular, many of these are related to the porous microstructure in its different aspects. The influence of the pore size distribution has been little investigated yet. In this work the overall issue is to show a model for the calculation of thermal conductivity for porous materials with different pore size distribution, but with constant porosity. The intermingled fractal unit model used, is characterized by a close relationship with real microstructure and in prevent studies it has been possible to find good correlations with the experimental data

A geometrical fractal model for the porosity and thermal conductivity of insulating concrete

The analysis of the porous microstructure can be addressed through the use of fractal geometry. The translation of the experimental data into mathematical equations allows researchers to obtain a number of geometric representations for which it is possible to apply those relations which are suitable to measure physical magnitudes otherwise difficult to measure. In this research we concentrated on the study of different kinds of cement as follows: - clay - wood aggregates. The determination of the thermal conductivity of the materials which were chosen can be carried out using the well-known concept of electrical analogy. Their microstructures are simulated using fractal patterns. Using the value of the effective conductivity that has been calculated in the previous stage as the value of conductivity of the solid phase, it is possible to obtain a set of results that will be fully comparable with the experimental ones. A further circuit diagram has been created to simulate the different compositions of the mixtures of the samples we studied, and again, the values were very close to the experimental ones

An intermingled fractal units model and method to predict permeability in porous rock

For the calculation of the permeability of porous materials we have utilized an approach based on the description of the microstructure of the voids using fractal geometry. The fractal dimension of the microstructure has been calculated using porosimetric data obtained with the technique known as mercury intrusion porosimetry, subsequently simulating the experimental pore size distributions through the application of an Intermingled Fractal Units model based on unit type: the Sierpinski carpet. In this model a special analytical expression of the permeability has been studied from which a set of values that satisfactorily agree with those obtained from the experimental tests were derived. As reference material a porous rock (calcareous stone) has been considered