Energy Saving Study Of Natural Ventilation Based On Coupled BES With CFD

Recently,with the promotion of energy conservation and emission reduction in our country,more and more attention has been paid to building energy efficiency.And natural ventilation as a very important passive energy efficiency measure has its irreplaceable advantages,which does not need to power consumption,but also can ensure the indoor fresh air,take away the excess heat and improve indoor thermal comfort.Therefore,the study of natural ventilation in buildings is of great significance.Building simulation technology is important building performance research tools,which can be used to investigate the applicability of each energy efficiency measure in building design stage,thus guide the building design.However,recently,the research on natural ventilation is mostly based on CFD(Computational Fluid Dynamics).This technique can simulate the effects of natural ventilation on indoor thermal comfort and pollutants,but there is no way to simulate the effect of natural ventilation on building energy consumption.The research on the energy efficiency of natural ventilation is mostly based on the building energy consumption simulation technology;however,the simulation of natural ventilation is based on the Multi-zone airflow network method.This method is a simplified method,which regard each space as a node,that is,the physical parameters of air inside the space is consistent,often has many limitations and contains big error,especially for indoor temperature stratification in the space.In order to overcome the disadvantage of the both and take the advantage of both,this paper implements a building energy simulation and computational fluid dynamics(CFD)coupling method,which can not only solve the error of natural ventilation simulation in building energy simulation,but also can obtain the effect of natural ventilation on indoor thermal comfort and pollutant.A coupled EnergyPlus and Fluent model has been implemented to calculate the airflow of opening and heat transfer coefficient of building surface,and the airflow rates of openings and heat transfer coefficients from the airflow network module in EnergyPlus and those from CFD model were compared.Results show that airflow network model generally predict smaller airflow rates for the openings.Airflow network model generates better results for openings on the south and east facade and internal openings,where there is no immediate adjacent building.Among the heat transfer coefficients calculation methods in EnergyPlus,the TARP algorithm generated closest HTC values to the coupled CFD results.The overall heat transfer coefficients of all the enclosure surfaces are calculated and it is found that the overall thermal resistances generated from the three convective HTC algorithms are almost the same,yet with observable difference from coupled CFD simulations.This paper also analyzes energy saving potential of nature ventilation in different thermal zone,and it is found that natural ventilation can reduce heating and cooling energy by reducing mechanical cooling and mechanical ventilation operation hours.Meanwhile,it is also found that among the nature ventilation's energy saving potential in six thermal zones,hot summer and cold winter zone occupies first place,hot summer and warm winter comes second.Energy saving potential of nature ventilation in server cold A zone and B zone is very little.