Study On The Control Effect Of Slot Exhaust Hood In Surface Treatment Workshop

With the rapid development of surface treatment technology, the types of pollutant gases emitted have also increased and the type and size of the industrial trough has become more diversified. In order to control the pollutants reasonably and effectively, how to choose the type and amount of local exhaust ventilation has become the key of workshop ventilation design. Existing domestic and foreign exhaust ventilation volume calculation method is still applicable to the current variety of trough type, which needs to be verified. In view of this, to achieve the same effect of pollutants control requirement, exhaust hood type, size of slot exhaust and different solution properties have great influences on the slot exhaust air volume and finally make a comparison with the existing methods.Firstly, this paper uses experimental methods to study the typical trough's air velocity field distribution above the tank solution. By changing the slit outlet height and wind speed, it is finally got a function formula about outlet velocity, outlet height and the velocity above the surface. In addition, this study also verifies the theoretical formulas of hydrochloric acid evaporation rate by experiments.Secondly, this paper determines three controlled wind speed values: 0.2m/s?0.25m/s and 0.3m/s via numerical simulation method and then, analyses the effectiveness of different control velocity, trough width and exhaust hood type. The results are as follows:(1) Under the same hood type, slot length and control of wind speed, when the concentration of pollutants in controlled areas meets health standards, exhaust volume is approximately linear associated with slot width.(2) The greater the controlled wind speed, the greater the growth rate of the exhaust amount with the width.(3) For unilateral slit-type hood, when the width exceeds 700 mm, the growth rate of exhaust volume is higher with the slot width.(4) With a trough, bilateral exhaust volume can reduce by more than 50% than unilateral ventilation exhaust volume.Finally, if the controlled wind speed values are 0.2m/s?0.25m/s and 0.3m/s, compared the volume values in this paper with handbook values, the handbook value is larger when slot width is less than 0.6m for unilateral slot exhaust. When slot width is more than 0.6m, the handbook value is smaller. And for bilateral slot exhaust, the same rule is appeared on the slot width as 1.6m.