Research On Thermal Insulation Optimization And Energy-saving Design Of Underground Building Envelope In Northwest China

In recent years,the number of development and use of underground buildings has increased rapidly.How to create a comfortable indoor thermal environment and make the indoor climate infinitely close to the comfortable climate of the human body is an inevitable problem in the thermal design of underground buildings.According to the"Code for Thermal Design of Civil Buildings"(GB 50176-2016),underground buildings mainly conduct thermal design for thermal insulation structures at present.However,underground buildings have their particularities and structural complexity.The research on indoor thermal environment has not yet formed a unified technical specification.Energy-saving technologies and construction methods for underground spaces in the project have been restricted,which has also led to different underground buildings.Thermal design is similar.In this context,this article takes the major cities in Northwest my country as the research object,analyzes and discusses the thermal design methods proposed in the prior standard specifications for the thermal design and energy-saving design of underground buildings,and compares the optimized thermal design methods.As a result,it provides a reference for the optimization of thermal insulation design methods for underground buildings in the northwest region.At the same time,the building numerical model is established and De ST is used to simulate the building energy consumption.The energy-saving effect and energy-saving potential results obtained can provide reference for the regional adaptability of underground buildings in the northwestern region.The main contents of this research are as follows:(1)The climate of selected five typical cities in the northwestern region was analyzed,mainly including the annual outdoor air temperature.At the same time,the actual ground temperature of the five cities was discussed and compared with the outdoor air temperature and the coldest monthly average outdoor temperature given by the thermal engineering specifications.The results showed a large difference,which provided a feasibility for the study.Data support.And compared the current mainstream building energy simulation software and finally selected De ST as the simulation tool,and introduced its main features and advantages.(2)The Ptemp is selected as the main calculation tool,and the simplified external thermal insulation structure wall is the research object,based on the above-mentioned actual ground temperature and the underground building envelope determined by the thermal code Based on the comparative analysis of outdoor calculation parameters of thermal insulation design,an optimized design method based on the current insulation design method of underground building envelope structure considering the outdoor side soil temperature buffer layer is proposed,and the actual ground temperature of each city is used as the outdoor calculation parameter to compare the two methods comparing.The thickness of 1.6m is determined as the buffer layer,and the surface temperature and the thickness are used as the main result.Through the results,it is found that whether to consider the influence of the soil buffer layer and the actual ground temperature has a influence on the results.The difference obtained by the optimized calculation model and the calculation model of the thermal specification is very large,and the maximum can reach Above 10°C.Regression analysis of the results.The regression equation has a high correlation.(3)Taking the underground first floor of an actual building of Xi’an University of Architecture and Technology as the main research object,through simulation and testing research methods,the actual situation of the indoor thermal environment of the underground space of the building is studied and the numerical model is verified.And based on the requirements of the external wall insulation performance the external wall external insulation with cement plaster and reinforced concrete as the main structural layer is continuously increased the thickness of the XPS insulation layer in the system,the heat load level of the same building model in five cities and two climate zones and the energy-saving potential of the room were studied,and the optimal heat transfer coefficient values of the outer walls of underground buildings in each city were obtained through simulation results.And through the results,it is found that the annual cumulative heat load index of Xining in severe cold area is 10.66 k W·h/m~2,which is lower than that of Xi’an(11.53)and Lanzhou(12.69)and Yinchuan(13.33).And through the energy-saving contribution rate index J to analyze the energy-saving potential of underground space in various regions,the energy-saving rate of each city is between 14.2%and 46.21%.The results show that the energy consumption of underground buildings in severe cold areas is not necessarily greater than that in cold areas,and the colder areas have greater energy-saving rates and greater energy-saving potential.