## Problems

6.1 A turbine with six curved blades is installed centrally in a baffled vessel. The vessel is 2.0 m in diameter. The turbine 61 cm in diameter is positioned 60 cm from the bottom of the vessel. The tank is filled to a depth of 2.0 m and is mixing alum with raw water in a water treatment plant. The water is at a temperature of 25°C and the turbine is running at 100 rpm. What horsepower will be required to operate the mixer.

6.2 Repeat Problem 6.1 using a shrouded turbine with six curved blades.

6.3 Repeat Problem 6.1 using a shrouded turbine with two curved blades.

6.4 Repeat Problem 6.1 using a propeller with three blades and a square pitch.

6.7 A shrouded turbine with six curved blades is installed centrally in a baffled vessel. The vessel is 2.0 m in diameter. The turbine 61 cm in diameter is positioned 60 cm from the bottom of the vessel. The tank is filled to a depth of 2.0 m and is mixing alum with raw water in a water treatment plant. The water is at a temperature of 25°C and the turbine is running at 3.24 hp. Calculate the rpm of the motor driving the agitator.

6.8 A propeller with three blades and a square pitch is installed centrally in a baffled vessel. The vessel is 2.0 m in diameter. The propeller is positioned 60 cm from the bottom of the vessel. The tank is filled to a depth of 2.0 m and is mixing alum with raw water in a water treatment plant. The water is at a temperature of 25°C and the turbine is running at 3.24 hp at an rpm of 100. What is the diameter of the impeller?

6.9 A propeller with three blades and a square pitch is installed centrally in a baffled vessel. The vessel is 2.0 m in diameter. The propeller is positioned 60 cm from the bottom of the vessel. The tank is filled to a depth of 2.0 m and is mixing alum with raw water in a water treatment plant. The turbine is running at 3.24 hp at an rpm of 100. The propeller is 61 cm in diameter. At what temperature is the mixing being done?

6.10 For the vessel in Problem 6.1, at what detention time should it be operated for it to function effectively? At what rate of inflow should it be operated?

6.11 For the vessel in Problem 6.2, at what detention time should it be operated for it to function effectively? At what rate of inflow should it be operated?

6.12 For the vessel in Problem 6.3, at what detention time should it be operated for it to function effectively? At what rate of inflow should it be operated?

6.13 For the vessel in Problem 6.4, at what detention time should it be operated for it to function effectively? At what rate of inflow should it be operated?

6.14 For the vessel in Problem 6.5, at what detention time should it be operated for it to function effectively? At what rate of inflow should it be operated?

6.15 A rapid.mix tank, 2 m in diameter is filled to a depth of 2 m with water and alum introduced continuously in the influent. The turbine is running at 3.24 hp and the average velocity gradient in the tank is 950 s-1. At what temperature is the alum being mixed with water? Determine the influent rate of flow to the mixer corresponding to an effective mixing.

6.16 A rapid.mix tank, 2 m in diameter is filled to a depth of 2 m with water and alum introduced continuously in the influent. The average velocity gradient in the tank is 950 s-1. The temperature of mixing is 25°C. Calculate the power dissipation of the mixer. Determine the influent rate of flow to the mixer corresponding to an effective mixing.

6.17 By considering the criterion for effective mixing, the volume of a rapid. mix tank used to rapidly mix an alum coagulant in a water treatment plant

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