Research On Air Distribution Methods Of Guardrail-based Air Supply Terminal In Areas With High Density Of People

In the waiting zones of airports,train stations,bus stations,subway stations,and other transportation hubs,poor indoor environment is primarily caused by human body-related factors in conjunction with the high density of people.Because the air supply terminal of existing ventilation systems is too far away from the human,the waste heat and pollutants generated by dense crowds cannot be effectively removed.People also feel draft discomfort due to the high local air velocity.In addition,people in the waiting area still need oxygen.For high-altitude hypoxic areas with high occupant density,it is necessary not only to have good temperature and humidity control but also provide oxygen-rich environments to meet the normal physiological needs of humans.Traditional oxygen supply systems,including individual oxygen supply（IOS）,distributed centralized oxygen supply（DCOS）and diffusion-type oxygen supply（DTOS）are limited in completing oxygen delivery tasks by the balance between low cost and high efficiency.This study proposes a guardrail-based air supply terminal that integrates guardrails and air ducts.Without changing the basic layouts of high and large spaces,the device can deliver fresh air or oxygen-rich air directly to the working area or human breathing zone.This study uses a combination of experimental research and numerical simulation.Firstly,three indicators,velocity target value,temperature target value,oxygen concentration target value are introduced to facilitate the evaluation of air/oxygen supply through the guardrail-based air supply terminal.The angle,width,velocity,air supply temperature,and oxygen supply concentration of the jets installed on the guardrail are optimized based on CFD numerical simulations.Secondly,this paper comparatively studied the air supply and oxygen supply characteristics of three common air distributions（ceiling-mounted air diffusers,displacement ventilation diffusers and middle sidewall-level air diffusers）in the high space.Lastly,the effectiveness of air supply and oxygen supply of the guardrail-based air supply terminals are verified by full-scale experiments and visualization experiments.The research results show that the optimal values of the air velocity at the circular nozzles V₁was 0.25 m/s,the penetration air velocity at the strip nozzles V₂ was 0.15 m/s,and the width of the unventilated strip W was 290 mm.The guardrail-based air supply terminal was found to create a homogeneous air velocity of 0.3 m/s to avoid draft sensations.In addition,the temperature of the working area was maintained at 26℃ in the summer,creating a comfortable environment.Compared with other air distributions in large and tall spaces,the velocity target value,temperature targeted value and air age of the guardrail-based air supply terminal are the smallest,and its energy consumption is61%lower than that of the vertical wall jets.The research results show that the optimal nozzle angleθof the guardrail nozzles for oxygen supply was 146°,the nozzle width W was 30.0 mm,and the nozzle air velocity V was 3.0 m/s.Compared with oxygen supply through other existing air distribution systems in high and large spaces,the optimized guardrail-based air supply terminal have9%to 27%higher effectiveness,expressed in terms of the oxygen concentration target value.The oxygen supply efficiency is 271%to 658%higher.The implementation of the system was studied at altitudes of 2000 m,3000 m,4000 m and 5000 m,which proved that this oxygen supply system has better implementation effects.By increasing the height of the guardrail by 100 mm,the oxygen distribution of guardrail slot diffusers can cover the breathing zone of adults in Europe and North America,and effectively increase the oxygen concentration inhaled by human body.The research results show that the air distribution generated by guardrail-based air supply terminals has a better effect of supplying air and oxygen-rich air.This study can provide new ideas for the design of air distribution in areas with high density of people,and promote the study of diffusion-type oxygen supply in high altitude areas.