Research On Thermal Performance Of Assembled Lightweight Composite Wall

Fabricated buildings have entered a period of rapid development recent years.However,China's current prefabricated buildings only account for about 3%of the number of new buildings,and there is still huge room for growth from the planned target of 30%.The light steel keel composite wall has excellent mechanical properties and meets the needs of fabricated buildings,so it is an ideal form of assembled wall.Since energy conservation and environmental protection have always been the direction of China's architectural development,the traditional light steel keel composite wall is difficult to meet the corresponding energy conservation requirements,and some of the performance indicators and structural characteristics of the prefabricated building wall are in conflict with each other.Under the premise of ensuring a high assembly rate,it is not appropriate to use traditional improvement measures to improve the thermal performance of the light steel keel composite wall.Therefore,it is of great significance to study the mature form of fabricated wall structure.In this paper,a combination of normative formula calculation,numerical simulation and experimental test is adopted,and a structural system that can satisfy the assembled building wall is proposed,and the thermal performance of the structural system was analyzed and studied,to pave the way for practical application.Firstly,according to the domestic and foreign research situation and the existing light steel keel composite wall form,for the characteristics of the assembled building and the actual performance requirements,the butyl rubber insulation strip was used to block the light steel keel thermal bridge to improve thermal performance of the wall.Three kinds of wall forms were designed,which are the ordinary wall form without special structure,the wall form with butyl rubber insulation strip,and the wall form with butyl rubber insulation strip and PVC sound insulation felt,and the civil building thermal design code(GB50176-2016)was used to estimate the thermal performance.Secondly,the three-dimensional heat transfer numerical simulation model of three kinds of walls was established.The temperature field and heat flow field inside the wall under steady heat transfer conditions were obtained,and the heat transfer coefficient was calculated,the heat flow distribution and thermal bridge effect were analyzed.The data shows that the use of butyl rubber insulation strips and acoustic felts only increases the overall thickness by 16 mm,and decreases the heat transfer coefficient by 45.4%.Therefore,it can be concluded that the butyl rubber insulation strip can effectively weaken the thermal bridge effect of the light steel keel,so that the three-dimensional heat flow distribution inside the wall becomes uniform,and the thermal performance is greatly improved.Thirdly,the actual test pieces of the three wall forms were tested using the protective hot box method.The results show that the actual heat transfer coefficient of the wall specimens without thermal bridge blocking measures is 1.000 W/m~2?K.The heat transfer coefficient of the specimens using butyl rubber insulation strips alone It is 0.794 W/m~2?K.The heat transfer coefficient of the test piece treated with butyl rubber insulation strip and PVC sound insulation felt is 0.520 W/m~2?K,which fell by48%.The error between numerical simulation results and experimental results of each specimen is less than 5%.Therefore,the two data coincide,which verifies the reliability of the numerical simulation analysis.Finally,each analysis method shows that the assembled lightweight composite wall with thermal bridge blocking measures can meet the requirements of thermal insulation and heat protection.The numerical simulation results of multiple sets of different thickness insulation strip models were fitted,and the GB50176 correction formula which can be used to accurately calculate the heat transfer coefficient of the wall body was obtained.It provides a new choice of wall structure form for construction industry in China.