Measurement Of Particle Resuspension From Surfaces When Wipe By A Dry Towel

Indoor air quality is closely related to people's health.Excessive indoor suspended particulate content will have a negative impact on human respiratory health and work efficiency.The sources of indoor suspended particles are very wide,in the room,the originally deposited particulate matter is affected by various behaviors and will be suspended from the surface into the room air.Cleaning behavior is one of the important behaviors that provoke the resuspension of particles deposited indoors.Wiping behavior is an indispensable cleaning action in people's daily lives.It is necessary to explore the process of resuspending deposited particles caused by wiping.In this thesis,we explored the process of resuspending deposited particles from the surface when using a dry towel to wipe the surface.First,a wiping experimental device platform was established,and a model hand was controlled to move horizontally through the guide rails to simulate the behavior of a person wiping the surface.The surface material to be wiped in the experiment was black cardboard or stainless steel plate,and the wiper used was a black towel of textile fiber material.During the experiment,the model hand held the dry towel and pressed it on the dust surface.The guide rail could control the speed,distance and wiping method of the model hand movement.In the study,a high-speed camera was used to record the wiping process,showing the image of particles detaching and suspending from the surface.Before and after wiping,use a precision electronic balance to weigh the mass of the towel and dust surface to calculate the mass of particles adhering to the towel and the mass of particles suspended in the air.In the wiping experimental device,a particle counter was used to measure the number of suspended particles at different positions.In addition,after wiping,the shape of particles spattering on the bottom edge of the towel was photographed.This study shows that when wiping,the particles deposited on the surface are suspended from the bottom of the towel and extending upward from the edge of the towel.The particles falling off on the towel and the particles splashing and breaking at the bottom are the main sources of suspended particles.Airflow and the thrust of the towel fibers on the particles are the main mechanisms of action.The suspended particles will follow the air flow generated by the wiping.When the towel stops wiping or reverse wiping,the suspended particles tend to spread to the surrounding space.The thickness and edge shape of the towel will affect the suspension of the particles.When the thicker towel is wiped(about 6cm thick in this study),the suspended particles will form a particle vortex and move forward,inhibiting the upward movement of the particles.As the wiping speed,wiping distance,wiping times,and dust density increase,the number of suspended particles will increase.Under low dust density(?s<4g/m~2in this study),when the wiping speed increases from 20cm/s to 40cm/s,the number of suspended particles in the size bin from 3 to 5?m can increase by more than 3 times;when the wiping distance increases from 10cm to 20cm,The number of suspended particles in the size bin from 3 to 5?m increased by more than 85%.