| With the rapid development of metal surface treatment technology,the type and the size of the process groove become more diverse,the types of pollutant gases emitted have also increased.In order to control the pollutants effectively and reasonably,how to choose the type and amount of local exhaust ventilation has become the key of the design for workshop ventilation.Although there are many kinds of calculation methods for different kinds of local ventilation,however,because of the improvement of control standards,it is necessary to verify whether these calculation methods are still suitable for all kinds of process groove type.In view of this,this subject has studied the influence of the type of the slot,the size of the process and the solution property of the solution on the air flow in the surface treatment plant when the same pollutant control effect is achieved,and finally make a comparison with the existing methods.In this paper,the experimental test,theoretical analysis and numerical simulation are used to study the method.First of all,the experimental results were tested in the laboratory and workshop,and the experimental condition was simulated by CFD.The applicability and the numerical simulation method of the theoretical calculation of the evaporation rate of pollutants in this paper are verified by the calculation of the flow field and the concentration field,to provide theoretical basis and calculation basis for the following work.Subsequently,using the CFD numerical simulation tool to simulate the air flow field of the high section single and double side slots,and analyze the influences of the height of the slit,the width of the slot and the length of the slot on the air flow field.Two formulas based on the control wind speed method were fitted,the single condition:Q = 12606vxL0.866W1.779,and the double condition:Q = 8268vxL0.869W2.047.Then using the CFD numerical simulation tool to simulate the concentration field of the high section single and double side slots,and analyze the influences of the height of the vertical baffle,the width of the slot,the length of the slot,the pollutant concentration in the control area and the position of the control area on the exhaust volume.Finally,the respiratory area of the workers is used as the pollutant concentration control area,and summarizes the general formula of concentration control method:Q = aCbLcWd.In this formula,a,b,c and d are constant which are varied by the different types of the slots and the pollutants.In the end,comparing the results of different formulas and methods.For the control wind speed method,the formula of this paper is compared with the manual formula,when the width of the slots is smaller,the calculation results of the formula in this paper is less than that of the formula in the manual;otherwise,when the width of the slots is larger,the calculation results of the formula in this paper is more than that of the formula in the manual.As for the concentration control method,when the temperature and the concentration is lower,the calculation results of the formula in this paper is much less than that of the formula in the manual;when the temperature and the concentration is moderate,the calculation results of the formula in this paper is a bit less than that of the formula in the manual;and when the temperature and the concentration is higher,the calculation results of the formula in this paper is more than that of the formula in the manual. |
