Assignment 2 sol

# Assignment 2 sol - = 1.8 for flat blade Density of water ρ...

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Assignment 2 Solutions 2. A flocculator paddle of the design and dimensions shown below is rotated through water at 20 o C with an angular speed of 4.0 r/min. (a) How much power is dissipated into the water? (b) If the tank in which this paddle is rotating has the dimensions of 4 × 4 × 4 m and the flow through the tank is 5000 m 3 /d, determine the Gt value for the flocculator. (a) Total Power Paddle velocity for Inner board = π x 2 x 4 x 1/60 = 0.419 m/s Paddle velocity for outer board = π x 3 x 4 x 1/60 = 0.628 m/s Power for each paddle Paddle tip speed (V p ) = 0.75 x paddle velocity Co-efficient of drag (Cd)

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Unformatted text preview: = 1.8 for flat blade Density of water ( ρ ) = 998.2 kg/m 3 Viscosity, μ = 1.002 x10-3 N.s/m 2 P = (C d A p ρ V p 3 )/2 Power, P1 for inner board = [1.8 x (0.1 x3 x 4) x 998.2 x (0.75 x 0.419) 3 ]/2 = 33.46 watt Power, P2 for inner board = [1.8 x (0.1 x3 x 4) x 998.2 x (0.75 x 0.628) 3 ]/2 = 112.64 watt Total power P = P1 + P2 = 33.46 + 112.64 = 146.1 watt (b) Gt Retention Time, t = V/Q = 4x4x4/5000 = 0.128 days = 1106 sec G = [P/(Vx μ )] 1/2 = [146.1/(4x4x4x1.002x10-3 )] 1/2 = 47.75 s-1 Therefore, Gt = 1106 x 47.75 = 52811.5...
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Assignment 2 sol - = 1.8 for flat blade Density of water ρ...

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