Study And Application Of Xiaokuangti External-wall Composite External Insulation System

Building energy saving is an important area of today's construction industry, and to improve the insulation properties, structural performance, and durability of building envelope are important direction for the development of exterior insulation technology. Based on the current quality defects, in order to meet the energy efficiency standards, improve the service life, reduce the later replacement and maintenance costs, and improve the performance of the system's structure and durability, this paper studies and develops a new composite external wall insulation system named xiaokuangti. Through theoretical analysis, numerical simulation and tracking test in the pilot project, the paper has completed a study of the following aspects:(1) The initial advance of xiaokuangti systemThe system, which optimally combines the closed air layer with insulation materials and enhances the thermal insulation performance of the overall system through the rational use of the closed air layer, can reduce the amount of insulation materials, the weight of the system, the energy consumption of the insulation material in the production process and waste disposal when its service life comes to an end. Through the design of the anti-shear key, the system can weaken the temperature stress of the outer facing layer and reduce the cracking probability. By using the structure system it can make the insulation system's life match the design cycle of the main structure. Based on national standards, the paper invents the xiaokuangti system from three organic components including the thermal insulation, structural system, interconnect structure of sub-system. Two national patents have been granted on the basis of above achievement.(2) Derived the equivalent thermal conductivity calculating equations based on the geometric dimensions change of the closed air layerBased on heat transfer theory, by the introduction of the equivalent thermal conductivity and the calculation of the heat transfer amount of the natural convection in the form of Fourier heat conduction formula, the paper studies the equivalent thermal conductivity variation of the Air layer with its thickness, height variation, temperature and poor external conditions changing and has got the thermal conductivity curve equation access to meet the engineering design accuracy of the closed air layer with the changes of these factors, and provides a simple thermal conductivity calculation for the xiaokuangti system design applications.(3) Obtained the optimal size range of the air layer thickness in insulation systemWhile combing solid insulation materials with the special material-air layer, its thermal insulation properties will inevitably vary with the change of the size and the ratio of the air layer, and the solid insulation material performance. By calculation and analysis, the paper has obtained the optimal size of the air layer and the combination of different insulation materials, sensitive changing areas, and the best ratio combinations in the specification of external building envelope thermal insulation performance requirements. A theoretical basis for the optimization design of the xiaokuangti system is provided.(4) Structure performance analysis of the xiaokuangti systemThe paper mainly simulates the stress and deformation law of the system in the temperature field, and compares it with that of the traditional system. The results show that temperature stress is the main reason for cracking of the outer facing layer. In this paper, it proves the anti-shear key can reduce the stress peaks in the extreme weather conditions, or delay the cracks on the outer layer, thereby reducing the probability of the insulation system leakage, cracking, and improving the performance of the structure and extending its service life.(5) Thermal performance analysis of the xiaokuangti systemIn accordance with the building envelope evaluation index, based on the physical model of unsteady heat transfer, the unsteady heat-conduction differential equations under the third boundary on the principle of the thermodynamic theory were established. And in accordance with the measured temperature of the housing inside and outside wall fitted in harmonic temperature wave as the amount of external interference, the heat flux density, attenuation coefficient, delay time and other performance indicators of the xiaokuangti system were calculated and the results (compared by recommended practices with the national norms) proved the superiority of xiaokuangti external wall insulation system. (6) Simulating applications and experimental verification of xiaokuangti systemIn order to test the applicability of the system, based on the optimization of the xiaokuangti system, the paper produces the kind of insulation system and applied it to a pilot project in Zhengzhou City. Energy simulation based on different directions the thickness of the insulation layer, indoor comfort indicator to distinguish between periods of heating indicators in winter and summer respectively, has been done, so as to obtain the system's engineering application pattern. A tracking test of 240h on the wall surface temperature, heat flow and room energy consumption has been taken. Through the comparison of test data and the theoretical results of the analysis, the superiority and the applicability of xiaokuangti is verified.(7) Application methods of xiaokuangti systemThe application methods of the xiaokuangti system composite exterior insulation system are introduced from five aspects:1. basic components; 2. range of applications; 3 main materials and technical requirements; 4. technical points of design; 5. the construction method(8) Constructed atlas of xiaokuangti systemThe research results of this paper are part of the xiaokuangti system constructed atlas. As one of the scientific research results of significant public interest research projects in Henan Province (081100910400), it has passed the evaluation of scientific research.(9) Obtained 18 composed thermal index of xiaokuangti systemAccording to the curved equation of equivalent heating conducting coefficient of closed air layer of xiaokuangti system, the optimization to the insulation has been taken to the system. The paper first combines closed air layer with three different insulation materials, then forms 18 xiaokuangti systems by combining them with the most commonly daily used wall external enclose materials, and separately calculates the thermal calculating index above, which provides a theoretical reference to the follow-up promotion and energy conversion calculation.