问答题
Suppose a certain rectangular settling tank: length is L=20 m; width is B=4 m; depth is H=2 m. If we change it into a countercurrent lamella sedimentation tank: horizontal distance between 2 lamellas is 10 cm; length of lamella is l=1 m; dip angle is 60. Ignore the thickness of lamella.
When critical velocity is u0=1 m/h, settling efficiency could be improved to [填空1] times after refit (ratio, retain only 1 significant digits),
In the new settling tank, Re is [填空2] (retain only 2 significant digtis).