Application Of EAHES On Passive Buildings In Chengdu

Using earth to air heat exchange system(EAHES)in passing building is a significant energy-saving technology,and its energy-saving effect is related to the system heat exchange capacity.So,it is very important to study the heat transfer model for the design of the EAHES and the energy-saving evaluation of the system application.First,this paper introduces the principles and characteristics of the EAHES,and gets the initial temperature distribution of the soil in Chengdu.Besides,the temperature of the soil and the air in winter and summer are analyzed for discussing the feasibility of applying this technology in this area.Secondly,by analyzing the heat exchange process of EAHES and the simplification of the physical model,a dynamic heat transfer model is proposed.By simplifying the heat transfer model of the system,a quasi-three-dimensional unsteady exchange model(a 2-D sub-model of transient heat conduction for soil and 1-D sub-model of transient convection-diffusion for air)is established.The models are solved numerically using finite volume method.By selecting appropriate discrete equations,the discrete equations of air temperature and humidity and soil temperature were obtained respectively.Then they were solved sequentially by using the MATLAB software program.Finally,the parameter values of all air nodes and soil nodes are obtained(all the air node are simultaneously solved and axial soil unit is computed respectively).And compared with the experimental data of Goswami and Benkert,the error is within 10%,so the accuracy of the model is verified.Then,with the help of the dynamic model of soil air heat exchange,the factors that affect the heat exchange capacity of the system are analyzed.The buried depth has the greatest influence on the heat exchange capability.The influence of pipe diameter and pipe length on heat exchange capacity is second.When other conditions are determined,the change of wind speed has little effect on heat exchange.The effect of inlet air temperature on heat exchange capacity is negligible.Finally,the article takes the first example of the passive building in Chengdu as the research object,and designs the application of EAHES in the fresh air system.Finally,analyzing the energy efficiency of EAHES in passive buildings.The results show that it has good effect,the satisfaction rate reaches 35.1% in summer.The winter does not meet the requirements,but 91.2% of the time the system processed the air enthalpy value of the indoor design status to 70% of the value of the indoor design status.