Experimental And Numerical Study Of Summer Night Ventilation For Buildings Containing Internal Thermal Mass Using Earth-to-air Heat Exchanger

Night ventilation is one of the strategies to reduce energy consumption in buildings with wide application prospects.However,there are still many issues to be studied on how to improve the practicality and applicability of night ventilation technology.Earth-to-Air Heat Exchanger（EAHE）is a kind of ventilation approaches using geothermal energy.It uses the feature that the ground temperature of soil is higher than the outdoor air temperature in winter and lower than the outdoor air temperature in summer,and introduces the outdoor air into the tunnel by means of heat pressure induction or mechanical ventilation,and then exchanges heat with the soil and enters the room,thus improve the heat and humidity environment in the room.Based on the importance of building internal thermal mass for night ventilation and the poor applicability of traditional night ventilation for areas with small diurnal temperature difference,this paper proposes a coupling form of combining EAHE with building internal thermal mass for night ventilationFirst,based on a full-scale experimental bench in Chongqing,the effect of night ventilation for buildings with internal thermal mass using EAHE on the regulation of indoor air temperature in summer was studied.By comparing the effect of using EAHE for night ventilation with conventional night ventilation on the building ventilation effect,and the effect of adding or not adding building internal thermal mass on night ventilation,the cooling effect of night ventilation with EAHE coupled with building internal thermal mass in summer was investigated.The temperature difference ratio（TDR）,Integrated discomfort degree of indoor temperature(I_DCT)and potential energy efficiency index（PEE）were introduced to evaluate the ventilation effect of EAHENV+ITM.The study concludes that the addition of internal thermal mass can effectively improve the thermal comfort and energy saving potential of night ventilation in buildings with night ventilation in summer.In buildings with additional internal thermal mass,the use of EAHE for night ventilation can increase the cooling capacity of the thermal mass during night ventilation compared with the conventional night ventilation method,thus improving the cooling effect of night ventilation on indoor air temperature.Then,based on the Computational Fluid Dynamics simulation tool Ansys Fluent platform,a numerical calculation model of night ventilation for buildings with additional internal thermal mass using EAHE is established,and the physical model simplification methods and numerical calculation setup methods are introduced.The numerical simulation results are compared with the experimental results to verify the accuracy of the numerical calculation method proposed in this paper,and to demonstrate the feasibility of the CFD simulation tool for the study of night ventilation for buildings with internal thermal mass using EAHE.Finally,the numerical calculation method established in this paper is used to study the cooling effect of combining EAHE with building internal thermal mass for night ventilation in summer and its influencing factors.It is shown that night ventilation with this mode can effectively reduce indoor air temperature and improve indoor thermal comfort throughout the day compared with no ventilation;the energy saving potential of night ventilation with this mode is higher than that of all-day ventilation.The main factor affecting the cooling effect of EAHENV+ITM on indoor air temperature is the amount of building internal thermal mass.While the effects of the ACH and the duration of night ventilation on the reduction of indoor air temperature are not obvious,reducing the ACH helps to improve the energy saving potential of this coupled form,and reducing the duration of this coupled form for night ventilation can make the deterioration of energy saving potential caused by the increase of the number of operating days slower.