Preliminary Study On Air Distribution Mode Of Wall Attached Duct Multi-directional Jet Supply In Occupied Zone

Building a good indoor air quality and reducing energy consumption has always been a key issue in the HVAC industry,compared to the widely used mixed ventilation mode in current buildings,displacement ventilation is generally considered to be an efficient and energy-saving form of air distribution mode.However,the displacement ventilation supply air velocity is limited,it is difficult to meet more indoor load under the condition of limited outlet area,as well as it is not suitable for heating.This paper proposes the wall attached duct multi-directional jet supply in occupied zone,which can not only have better indoor air quality and human thermal comfort than the displacement ventilation system,but also undertake more indoor load and can be used for heating.Firstly,in this paper the air distribution characteristics of the wall attached duct multi-directional jet supply in occupied zone is analysed by using numerical simulation method in Airpak,and in order to verify the accuracy and reliability of the simulation model,an full-scale experimental bench is set up.Through the analysis of indoor temperature and velocity distribution,the study shows that in cold conditions the wall attached duct multi-directional jet supply in occupied zone can form an air-lake model and temperature stratification phenomenon in the vertical direction,which is similar to the displacement ventilation.Then,in order to compare the wall attached duct multi-directional jet supply in occupied zone and displacement ventilation,a more authoritative MIT displacement ventilation office model in the field of airflow organization will be studied as a reference,numerical models of the wall attached duct multi-directional jet supply in occupied zone and displacement ventilation are set up under the cold condition,the temperature field,velocity distribution,vertical temperature difference between head and foot,Draught Rate(DR),PMV,PPD,Air Diffussion Performance Index(ADPI),mean age of air field,and ventilation efficiency were compared between the two ventilation modes under the same air supply temperature,air supply volume and heat boundary condition.It can be seen that the wall attached duct multi-directional jet supply in occupied zone can create better indoor air quality,provide better human thermal comfort,have higher ventilation efficiency and larger air supply,as well as can undertake larger indoor load.Finally,in order to study the heating capacity of the wall attached duct multi-directional jet supply in occupied zone,take an office in the cold city of Dalian as example,establish numerical models of the wall attached duct multi-directional jet supply in occupied zone and displacement ventilation under heating conditions,and results show that hot air flow sent from the air outlet can be diffused in the lower working area of the room in the wall attached duct multi-directional jet supply in occupied zone by increasing supply air velocity and changing the supply air angle,in the same time happen heat exchange with indoor air to meet indoor heating needs.While in the displacement ventilation system,due to the lower supply air velocity,the air flow has not yet entered the work area and is directly diffused into the upper part of the room under the effect of the heat buoyancy,resulting in poor heating effect.Therefore,the wall attached duct multi-directional jet supply in occupied zone can meet more indoor load on the basis of the advantages of displacement ventilation,it can be used under the heating condition.