Tube setter design Case
-Design and calculation of tube settler sedimentation tank(lamella water treatment)
1. Known conditions
Treatment capacity Q = 195000 m3/ D
Inclined tube sedimentation tank is divided into two groups
The settling velocity of particles is 0.35 mm / s
Rising velocity in clear water area: v = 2.5mm/s
The hexagonal honeycomb tube is hot pressed with plastic sheet, the tube thickness is 0.4mm, the edge distance is d = 30mm, and the horizontal inclination angle is 0.4mmθ=600。
2. Design calculation
1. The flow rate of each sedimentation tank Q: 1
Q=195000/2 m3/d=97500 m3/d=1.13 m3/s
2. Clear water area:
A = q / v = 1.13/0.0025 = 452 m2, in which the area occupied by inclined pipe structure is calculated as 3%, then the actual required area of clear water area is a/= 452×1.03=465.6 m2
In order to distribute water evenly, the plane size of inclined pipe area is 15.8m×The inlet area is arranged along the side of 29.5 m long.
3. Length of inclined pipe L
Flow rate: V0= V / sinθ=2.5/sin600=2.5/0.866=2.89mm/s
Length of inclined tube: l = (1.33 V0- μ sinθ)d/µcos600=(1.33×2.89-0.35×0.866)d30/0.35×0.5=607mm
Considering the factors of turbulent flow and mud deposition at the pipe end, the transition zone is 250mm
Total length of inclined pipe: l/= 250 + 607 = 857, calculated by 1000mm
4. Pool height:
Protection height: 0.3m
Clear water area: 1.2m
Water distribution area: 1.2m
Height of perforated sludge hopper: 0.8m
Height of inclined tube: H = l/sinθ=one×sin600=0.87m
Total height of pool: H = 0.3 + 1.2 + 1.2 + 0.8 + 0.87 = 4.37m
5. Perforated wall is used at the inlet of sedimentation tank
Perforated pipe is used for sludge discharge and perforated pipe is used for water collection system. All the above calculation are the same as that of general sedimentation tank or clarifier.
6. Recalculate the Reynolds number and sedimentation time in the tube
Re=Rv0/ξ
In the formula, hydraulic radius: r = D / 4 = 30 / 4 = 7.5mm = 0.75cm
Flow rate: V0= 0.289cm/s
Kinematic viscosity:ξ=0.01cm2/ S (when t = 200C)
Re= 0.75×0.289/0.01=21.68
Precipitation time: T = l// V0= 1000 / 2.89 = 346s = 5.77min (precipitation time t is generally between 4 ~ 8min)
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