| In recent years,people spend up to 80%of their time indoors,so indoor air quality has received widespread attention.As one of the main factors affecting indoor air quality,ultrafine particles have a serious impact on human health,so it is of great significance to study the distribution rules of indoor ultrafine particles.The purpose of this subject is to explore the effect of indoor temperature,air velocity,and source height on indoor ultrafine particle concentration distribution by combining numerical simulation and experimental research.The numerical simulation of this subject uses FLUENT computational fluid dynamics software to calculate the concentration distribution of ultrafine particles in the room under different working conditions.Combined with the research content of the subject,a comprehensive experimental platform for air particulate control technology was used only for experimental research.Under the working conditions set in this topic,the following conclusions are drawn:（1）Numerical simulation results showed that after the ultrafine particles were emitted from the particle source.The particle source was taken as the center and diffused into the three-dimensional space where they were located.The particle concentration attenuation rate per unit distance within the range of 0m-0.75m and 0.75m-1.5m in the Y direction was equal,and the particle concentration attenuation rate per unit distance within the range of 0m to the height of the particle source and the height of the particle source to2m in the Z direction was equal.Both Y and Z directions were symmetrically distributed.（2）The numerical simulation results showed that:when the height of the particle source was 1.1m,the ultrafine particles mainly gathered within 0.5m from the particle source.The particle concentration would suddenly fall in the range of 2.5m-2.0m.（3）Under the setting conditions of constant particle source height and air supply speed and different indoor temperatures,the simulation results showed that the maximum concentration value of measuring point 1 at different temperatures was 8.37E-05kg/m3,and the minimum concentration value was 8.17E-05 kg/m3.The difference between the two was2.04E-06 kg/m3,and this difference ranked first in the difference between the maximum concentration value and the minimum concentration value at different temperatures at each measuring point.It was concluded that when the temperature changes between 10℃ and30℃,the concentration of ultrafine particles at each measuring point did not change much.From the experimental results,it could be seen that the maximum concentration of ultrafine particles at each measuring point appears at Z=1.0m or Z=1.2m,and the concentration of ultrafine particles at each measuring point was less affected by temperature.Combining the numerical simulation results with the experimental results,we could see that the two results were consistent,that was,within the temperature ranged of 10℃-30℃,the temperature change had little effect on the indoor ultrafine particle concentration distribution.（4）Under the setting conditions that the height of the particle source,the indoor temperature remain unchanged,and the air supply speed was different.From the simulation results,it could be seen that with the increased of wind speed,the concentration of ultrafine particles at the measuring point on the extension line of the particle source and the measuring point near the return air inlet was increasing.However,the particle concentration of the measuring point near the air outlet showed a downward trend.The maximum concentration value of measuring point 7 under different wind speeds was 5.97E-06kg/m3,and the minimum concentration value was 6.31E-07 kg/m3.The difference between the two was 5.3E-06 kg/m3.And this difference was the last in the difference between the maximum concentration value and the minimum concentration value at different wind speeds at each measuring point.From the experimental results,it could be seen that the maximum concentration of ultrafine particles at each measuring point appears at Z=1.0m or Z=1.2m,and the ultrafine particle concentration at each measuring point was greatly affected by wind speed.Combining the simulation results with the experimental results,it could be seen that within the air velocity ranged of 0.5m/s-2.5m/s,the change of the air velocity had a great influence on the concentration distribution of ultrafine particles in the room.As the wind speed increased,the ultra-fine particles gradually diffused toward the return air inlet.（5）Under the setting conditions that the indoor temperature and air supply speed were unchanged and the height of the emission source was different.The simulation results showed that when the height of the emission source was 0.5m,1.1m and 1.6m,the ultrafine particles were mainly concentrated in the height range of 0-1.0m,0.6-1.6m and 1.1-2.0m.It could be seen from this that when the indoor temperature was 20℃,the emission speed of ultrafine particles was 1.6 m/s,and the air velocity was 1.5 m/s,the height of the main aggregation area of ultrafine particles was about 1.0 m.From the experimental results,it could be seen that the main distribution area of the particles would move in the vertical direction as the height of the particle source changed.Combining the numerical simulation results with the experimental results,it could be seen that the height of the particle source had a greater influence on the distribution of ultrafine particles in the room.Changing the height of the particle source can control the distribution area of ultrafine particles in the room.（6）The experimental results were reported to the numerical simulation results,and the errors obtained were within the acceptable range.This verified the accuracy of the mathematical model employed in the numerical simulation and the reliability of the numerical simulation results. |
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