Analysis And Evaluation Of The Air Distribution Under Column Attached Ventilation In Public Area Of Subway Station In Hefei

As a common form of urban public transportation,subway has become people’s first choice for daily transportation because of its high efficiency and convenience.The hot and humid environment of the subway station directly affects the thermal comfort of passengers.Reasonable air distribution has an important influence on passengers’ comfort and health.In the paper,the interior flow field of the public area in the subway station were analyzed under column attached ventilation and mixed ventilation mode,and the optimal design advice and energy saving analysis under column attached ventilation were given.Considering the diversity of the columns in the building space,air distribution characteristics of irregularly curved column attached ventilation were given in the paper.Taking a public area of a double-column station in Hefei as the research object,the velocity field and temperature field in the station under the attached ventilation and mixed ventilation mode were compared and analyzed.The velocity and temperature of operating zone,head-to-foot temperature difference,relative warmth index(RWI)and ventilation efficiency were used for evaluation.The results showed that the average velocity under the two modes can meet the design requirements at the same air volume.Under the attached ventilation,the average temperature of station hall and platform working area were 29.65℃ and 28.78℃ respectively,while under the mixed ventilation mode,the average temperature of station hall and platform working area were 30.82℃and 29.61℃ respectively.As for evaluation of ventilation effect,the temperature difference between head-to-foot under the two modes was less than 3℃.Under themixed ventilation mode,the RWI value in the station was slightly higher than that in the attached ventilation mode.Under the both ventilation modes,in the station hall,the RWI value was "warm".And in the platform,the RWI value was "slightly warm".Under the attached ventilation mode,the ventilation efficiency in the station was higher than that of mixed ventilation mode.Through analyzing the interior flow field distribution and the air distribution evaluation index under attached ventilation with four air supply velocity,the condition 2(the station hall supply velocity was 2.96 m/s,the platform supply velocity was 2.94m/s),which was optimal,can meet the design requirements.Compared with mixed ventilation,the air volume in the station hall decreased by 20% under attached ventilation,and in the platform decreased by 16.4%.The cooling capacity was reduced by about 15.5%.In general,the attached ventilation was more energy-saving than the mixed ventilation mode,providing passengers with a more comfortable environment.Consider the diversity of the column attached ventilation in engineering practice,the paper changed the form of column and made a comparison with circular column.It was found that outer convex column,circular column and inner convex column can form well attached effect,and produce temperature stratification in the height direction.As for evaluation of ventilation effect,the average velocity of the working area was less than 0.3 m/s,and the temperature difference of the head-to-foot in the standing(1.7 m above the ground)and sitting(1.1 m above the ground)positions were less than 1.5℃,and the ventilation efficiency was greater than 1.1.The draft sensation was less than20%.Compared with the circular column attached ventilation,the vertical axis velocity of the outer convex column decayed faster,and the jetting departure point was higher.The inner convex column decayed greatly when it was just ejected from the air inlet,and it decayed to 0.9.However,with the flow along the column surface,the jetting was "entrapped",and the vertical axis velocity decayed slower.The axial velocities of the three kinds of columns attached ventilation in the horizontal direction showed similar distribution law.Aiming at the different curvature and convexity of the columns,the variation law of the horizontal range of irregularly curved column attached ventilation was explored by changing the supply velocity(1~6 m/s).When the horizontal flow was not restrictedby the surrounding walls,the horizontal range of the irregularly curved column increased linearly with the increase of the supply velocity.Within the scope of the study,the horizontal range of the irregularly curved columns with different curvature and convexity was not different at the same supply velocity.