11 Next, for each style (fill thickness and mist diameter), the relationship between airflow velocity and collection efficiency is as shown in graph 4, and the airflow velocity tends to reach the maximum efficiency at 1 to 2 m/s in each style, and the efficiency tends to decrease due to reaccompany over the allowable flow velocity. When actually using Demi Star, there are many types of mist or the average diameter of the mist is unknown, resulting in some errors in the efficiency calculation above, but as an example of the system of water drops and air, it is shown in graph 5. As can be seen from Graph 5, it is difficult to collect and remove with high efficiency at a mist diameter of 1 to 2 μm or less, and a considerable number of layers is required to obtain a satisfactory effect. Collection efficiency It has been announced by C, L, Carpenter, etc. as a theoretical formula for the collection efficiency of Demi stars. E＝ １－ （1 －Et/C）N …………Equation (3.1) C = N/k2F ……………………Equation (3.2) E ：Demi Star's theoretical collection efficiency Et ：Mist collision efficiency C against one line of Demi Stars ：Modification Characteristics of Demi Stars (Table 3) N ：Number of filling layers k2 ：Non-dimensional ratio F ：It is known that Et is affected by the line length, mist diameter, operating conditions, etc., and that there is a relationship as shown in graph 3 between K and Et, defined in the following formula. ……………Equation (3.3) K ：Number of Stokes ρl ：Mist density kg/m3 U ：Airflow speed m/s dl ：Mist diameter m μg ：Fluid viscosity Pa s Df ：Theoretical efficiency E obtained from the line length m expression (3.1 to 3.3) is well matched with the experimental values, and the collection efficiency can be estimated and calculated based on the parameters and variables associated with the actual usage conditions of Demi Star. From graph 3, Et can be approximated by the following equation as a function of K. ……Equation (3.4) However, 0.1 ≤ K ≤ 100 As can be seen from the above relationship, the airflow velocity, mist diameter, and mist properties have a close relationship with the collection efficiency. （dℓ）2ρℓU K＝1 9 μgDf 1 －10 Et＝ －0.22(log 10K）2
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