| The Qinghai-Tibet Plateau region is cold with low pressure and dry with lack of oxygen.At present,the problem of creating a suitable indoor thermal environment has been basically solved,in order to ensure the physical and mental health of personnel and work efficiency,the creation of a comfortable oxygen environment and wet environment has become an urgent need.In the existing research,the oxygen environment is mainly created for the restricted areas with high population density such as tunnels,trains and hospitals,and the wet environment is mainly created for the relative humidity regulation of indoor air under atmospheric pressure conditions,however,the atmospheric pressure in the Qinghai-Tibet Plateau region is low,the air density is small,the wet oxygen content is low,and the diffusion process of wet oxygen components in the air is different from that in the atmospheric pressure region.And for the office building,the directional wet oxygen transport to the work site is an effective means to ensure the wet oxygen environment.Therefore,based on the wet oxygen demand at the office location,proposing suitable parameters for moisture supply and oxygen supply is a prerequisite to ensure the efficient creation of a local wet oxygen environment in the plateau.Based on this,this paper firstly analyzes the factors affecting the effect of moisture supply and oxygen supply at the working point under low pressure drying conditions,establishes a physical model and a mathematical model for moisture oxygen transport,analyzes the effect of low air pressure on air physical parameters,and provides basic parameters for subsequent numerical calculations,and proposes the average oxygen concentration,average velocity,average moisture content and its inhomogeneity coefficient as evaluation describing the level of moisture oxygen diffusion and distribution The influence of atmospheric pressure,end form of moisture supply and oxygen supply,end position,exit velocity,oxygen concentration and wet component concentration on the diffusion and distribution characteristics of wet oxygen is analyzed by numerical calculation,and the suggested values of key parameters of moisture supply and oxygen supply end are given to meet the oxygen demand,wet demand and wet oxygen synergistic transport demand at the working point.Specific research results are as follows:Part1:There is a separate oxygen demand(1)The location of the oxygen supply end has a significant effect on the oxygen supply effect.Since the density of oxygen component is greater than the density of surrounding air will produce sinking phenomenon,it is recommended that the oxygen supply end be placed directly in front of the face,and the angle between the grille upward and horizontal is 30°～40°.(2)Because the distance between the oxygen supply end and human breathing area is short,the form of oxygen supply end has less influence on oxygen diffusion and oxygen supply level in the breathing area;lower atmospheric pressure can enhance oxygen diffusion and make oxygen distribution in the breathing area more uniform,but it has less influence on the average oxygen concentration in the breathing area.(3)Oxygen supply end exit velocity and oxygen supply concentration have significant effects on oxygen diffusion and oxygen supply effect.Oxygen supply end velocity will determine the inertial force on oxygen-rich air outflow,and oxygen supply concentration will determine the size of gravity effect on oxygen-rich air diffusion process,both of which will affect oxygen-rich airflow organization and thus affect oxygen supply effect.(4)To meet the oxygen demand at the working point under low pressure conditions,the oxygen supply end exit speed is recommended to be 0.3～0.4m/s,and the oxygen supply concentration is 28.1%～31.7%.Part2: There is a separate wet demand(1)The location of the end of the wet end affects the organization of wet airflow and wet component space distribution,due to the density of wet components less than the surrounding air will produce uplift,it is recommended that the end of the wet end placed in the human face oblique above,downward tilt angle of 30°～ 45°.(2)As the distance between the wet end and the breathing area is short,the end form has less influence on wet diffusion.Lower atmospheric pressure will reduce the resistance to water vapor diffusion,enhance the wet diffusion process,and make the wet distribution in the respiratory area more uniform,but the average moisture content of the respiratory area has a small impact.(3)The exit speed of the end of the wet supply and the size of the wet component concentration have a significant impact on the wet diffusion and the wet supply effect.The exit speed of the wet supply determines the inertial force on the wet air outflow,and the wet component concentration determines the upward floating force on the wet air diffusion process,so both will affect the airflow organization of the wet air and the spatial distribution of the wet component,thus affecting the wet supply effect in the breathing zone.(4)To meet the wet demand of the working point under low pressure drying conditions,the exit speed of the wet end is recommended to be 0.4～0.45m/s,and the relative humidity of wet air is 47.5%～85.5%.Part3: There is a demand for collaborative transportation of wet oxygen(1)The use of double pipes for moisture and oxygen supply will make the wet diffusion and oxygen diffusion affect each other,so it is better to use a single pipe for wet oxygen synergistic transport,and the closer the density of the air fed into the wet oxygen is to the density of indoor air,the better the wet oxygen synergistic diffusion effect.(2)To meet the demand of wet oxygen co-conveying at the working point under the low pressure dry condition,the recommended range of wet oxygen concentration(relative humidity-oxygen concentration)combination is: 47.5%～57%-27.2%～30.8%,57%～66.5%-29%～30.8%,66.5%～76%-30.8%～32.6%,76%～95%-32.6%～ 34.4%,the recommended range of export speed: 0.3～0.6m/s.The results of the above study can provide suggested values for the end parameters of wet oxygen source to meet the oxygen demand,wet demand,and wet oxygen synergistic transport demand at the working site in the plateau,and provide a theoretical basis for the creation of wet oxygen environment at the working site under low pressure dry conditions. |
