Energy Saving Effect in Conditions of Air Infiltration through External Wall Made of Air-Permeable Materials

Abstract

The purpose of research consists: in analysing the results, obtained on the development of lightweight ceramic materials with variable cellular structure parameters for efficient control of heat exchange and air permeability processes in external enclosing structures of buildings; in the compilation of the model of economizing effect in such a structures with penetrable porous medium. The features of thixotropy processes of ceramic slurry masses based on natural silicites are investigated. Lightweight ceramics with variable parameters of the cellular structure was obtained by the method of vibra-swelling at a frequency of vibration of the slurry 1200…1500 min−1, the amplitude 3…5 mm, during 3 min. A model is developed, that describes the heat transfer and air-permeability processes in external enclosing structures during the movement of counter current heat flows from the heated room and as an infiltration from the outer surface of the enclosing structure. This model takes into account, that with such an exchange under certain conditions may arise the economizing effect, in which part of the heat flow of the room is transferred to the pores of the material. It is shown, that according to standards of thermal protection of buildings the process of infiltration of cold air is considered as an unfavourable factor, causing the cooling of the structure mass and increasing of heat losses. Calculation model is applied for a limited number of design solutions of external enclosing structures with the material, having penetrable porous medium, that provides its increased air permeability. Based on model of economizing effect in the external wall, the approximate evaluation of the heat economy is given due to the reducing of the inlet cold air and amount of the heat on its temperature rise. As a result of research are developed the light ceramic materials with changeable parameters of cellular structure. This significantly improved the variability of macrostructure parameters, increased the degree of reproducibility of the required technical result and the strength characteristics of the ceramic material. A model is developed, describing the economizing effect, which can arise during the process of air infiltration in external enclosing with a similar material structure. According to the model the economizing effect increases with raising of building height, as well as with decreasing resistance to air permeability of external enclosure structure. There was given the effect of heat saving during air infiltration on the example of a room with a small area.