| For ventilation and air conditioning system,a reasonable air distribution can not only create a comfortable heat and humid environment for indoor occupants,but also provide a high air quality,and reduce the energy consumption of the system.Mainly airflow patterns are: mixing ventilation(MV),displacement ventilation(DV)and personalized ventilation(PV).On the basis of the advantages and disadvantages for considering the above airflow patterns,many experts and scholars proposed series of novel types of ventilation,such as hybrid ventilation(HV),stratum ventilation(SV),wall-attached air curtain ventilation(WACV)and protected occupiedzone ventilation(POV).These ventilation modes have their own main application for different types of building space,but they are difficult to play their roles in the construction of large span space.Through the study of wall-attached air curtain ventilation,combined with uniformly distributed structure columns in the large span construction,a new method of air distribution known as airflow patterns by column-attached air curtain ventilation(CACV)has been developed,and choose square column as the study object.Based on the summary theories of various kinds of jet,the theoretical model of CACV was firstly built,and divided the flow field of this airflow pattern into vertical column-attached area,jet impinging deflection area and horizontal air lake area.The air lake was subdivided into mainstream area and intersection area for the influence of 90° corner of the square column on the flow field in the air lake,mainly studying the three-dimensional jet characteristics thus.The study then carried out full-scale experiments for CACV,which was validated the feasibility and effectiveness according to the flow visualization experiment.The supply air can form attached jet with wall of square column after the slot,when downstream moved to near ground level,the air direction became to be horizontal for adverse pressure effect of ground,then the main flow turned into secondary-attached flow with the ground,and got a tape of "air lake" for flow field distribution centered the square column in the work area.There was also an obvious phenomenon of flow stratification along the height of the room,which improved the ventilation efficiency and air quality in occupiedzone.In addition,this airflow pattern was got measurement study by three-dimensional velocity testing,on this basis,the axis jet velocity of different flow area,the main section jet velocity distribution,the downstream jet thickness expansion and the flux variation formula of downstream main section were presented.Meanwhile,the numerical simulation model of square column-attached air curtain ventilation was established and the turbulent model—RSM-IP model was proved to be the most effective in prediction of the flow field distribution of square column-attached air curtain ventilation by experimental data.The calculation formula of jet axis temperature and the temperature distribution along the height of the room were obtained,and the effect of indoor load,square column width,column span and return air location on square column-attached air curtain ventilation was also analyzed.Integrating calculation formulas of each characteristic parameter for the flow field,the engineering design process and procedures of square column-attached air curtain ventilation was introduced.According to actual engineering case,the design scheme was given,and the design of the parameters is given,by setting reasonable air supply parameters,the CACV model could satisfy the comfort requirements for occupants and produce an effective result as displacement ventilation(DV)system. |
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