Ventilation Design Based On Distribution Of Indoor Particles And CO₂ Using CFD Simulations

Background: The airtightness of buildings is improved to reduce infiltration of cold air and energy consumption.However,it also leads to lots of problems,such as high indoor pollutant concentration,which will reduce work efficiency and cause many health problems.For instance,the pollutants such as CO2 generated by people gather in the indoor environment.In addition,outdoor fine particles can enter into indoor by penetration.When outdoor air pollution is severe,the natural ventilation can't guarantee indoor air quality.Therefore,in order to provide fresh air and decrease indoor pollutants,it is necessary to optimize ventilation system design in residential buildings.Contents: In this paper,the distribution and removal of fine particles and CO2 are investigated in two different environments and the ventilation strategies are proposed.First,under the condition of floor heating,the effects of ventilation mode,air velocity and floor temperature difference on the dispersion and distribution of fine particles are investigated.Second,the effects of ventilation mode,ventilation rate and pollutant source location on the distribution of CO2 are investigated.The multi-mode ventilation systems are optimally designed according to different source locations to efficiently remove indoor pollutants.Methods: The experimental and numerical methods are applied in this study.The experimental data is used to validate the reliability of numerical simulation.Then the numerical method is used to simulate the distribution of airflow and pollutants.The turbulence model is solved by using RNG k-? model.The Lagrangian particle tracking model is used to simulate the transportation of particles and the species transport equation is solved for CO2 distribution.Conclusions:(1)Ventilation design for floor heating(removal of particles)Under floor heating,the air velocity increases with the increasing of floor temperature difference.The removal of fine particles is faster with increasing of air supply velocity and floor temperature difference.For the same air supply velocity(0.5m/s),it takes about 200 s for the normalized particle concentration decreasing to 0.1 with floor temperature difference of 15 K,however it takes about 391 s for zero floor temperature difference(0K).The down supply ventilation mode performs better to remove indoor particles with the increasing of floor temperature difference.When the floor temperature difference is 15 K,the time for removing particles can be reduced by 15% with down supply ventilation mode.(2)Multi-mode ventilation design(removal of CO2)The distribution of CO2 concentration is different with different ventilation modes and pollutant source positions.Under different ventilation modes and pollutant source positions,it is effective to reduce CO2 concentration by increasing ventilation rate.For most positions of pollutant source,down-supply and ceiling-return ventilation mode is better to remove CO2.The ventilation rate can be reduced by 30.4% for the same indoor CO2 concentration.Significance: In this study,the relationships between airflow,temperature and particle concentration in a ventilated and floor heating room are pointed out,which will provide useful guidelines for indoor pollutant control and ventilation design in floor heating rooms.In addition,the multi-mode is constructed with different pollutant source positions.This finding can give guides for ventilation strategy with multi-pollutant source,indoor air quality monitoring and intelligent ventilation.This study will give some references for future researches to improve indoor air quality and reduce building energy consumption.