Abstract
Investigating the large number of various materials now available, some materials scientists promoted a method of combining existing materials with geometric features. By studying natural materials, the performance of simple constituent materials is improved by manipulating their internal geometry; as such, any base material can be used by performing millimeter-scale air channels. The porous structure obtained utilizes the low thermal conductivity of the gas in the pores. At the same time, heat radiation and gas convection is hindered by the solid structure. The solution that was proposed in this research for obtaining a material with porous structure consisted in perforating extruded polystyrene (XPS) panels, as base material. Perforation was performed horizontally and at an angle of 45 degrees related to the face panel. The method is simple and cost-effective. Perforated and simple XPS panels were subjected to three different temperature regimes in order to measure the thermal conductivity. There was an increase in thermal conductivity with the increase in average temperature in all studied cases. The presence of air channels reduced the thermal conductivity of the perforated panels. The reduction was more significant at the panels with inclined channels. The differences between the thermal conductivity of simple XPS and perforated XPS panels are small, but the latter can be improved by increasing the number of channels and the air channels’ diameter. Additionally, the higher the thermal conductivity of the base material, the more significant is the presence of the channels, reducing the effective thermal conductivity. A base material with low emissivity may also reduce the thermal conductivity.
Highlights
The research reported in this paper aims at describing a new design of building materials with improved thermal insulation properties, by applying different geometries of air channels inside the materials, increasing porosity and lowering the density
The effective thermal conductivity of porous materials can be calculated by using the thermal conductivity of the solid ( ), the thermal conductivity of the air within
The effective thermal conductivity of porous materials can be calculated by using the thermal conductivity of the solid, the thermal conductivity of the air within the pores (λ air ), the number of pores (n) and the diameter of a pore (D): λe f f =
Summary
Energy conservation by reducing heat losses, the temperature control on walls surfaces aimed for people’s protection and comfort and the increase of the operating efficiency of heating/ventilating/cooling systems, steam plants, commercial and industrial processing and supplying systems are all research directions for sustainable and intelligent development, correlated with the climate changes that have occurred in the past decade. The main factors influencing the heat transfer in a material are the thickness of the material and its thermal properties: thermal conductivity and specific heat. The porous structure uses the low thermal conductivity of the gas in the pores. Heat radiation and gas convection is hindered by the solid structure [4]. Materials with thermal insulation properties are divided according to their inner structure into:
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