Question

Chemical Engineering Fluid Mechanics 30. The purpose of a centrifugal pump is to increase the pressure of a liquid in order to move it through a piping system. The pump is driven by a motor, which must provide sufficient power to operate the pump at the desired conditions. You wish to find the pressure developed by a pump operating at a flow rate of 300 gpm with an oil having a specific gravity (SG) of 0.8 and a viscosity of 20 cP and the required horsepower for the motor to drive the pump. The pump has an impeller diameter of 10 in., and the motor runs at 1200 rpm. termine the dimensionless groups that would be needed to completely describe the per formance of the pump. (b) You want to determine the pump pressure and motor horsepower by measuring these quan- tities in the lab on a smaller-scale model of the pump that has a 3 in. diameter impeller and a 1800 rpm motor, using water as the test fluid. Under the operating conditions for both the lab model and the field pump, the value of the Reynolds number is very high, and it is known that the pump performance is independent of the fluid viscosity under these condi- tions. Determine the proper flow rate at which the lab pump should be tested and the ratio of the pressure developed by the field pump to that of the lab pump operating at this flow (c) The pump efficiency (n) is the ratio of the power delivered by the pump to the fluid (as hotor. Because this is a dimensionless number, it should also have the same value for both rate as well as the ratio of the required motor power in the field to that in the lab determined by the pump pressure and flow rate) to the power delivered the lab and field pumps when they are operating under equivalent conditi to the pump by the tion satisfied? condi- 31. When a ship moves through the water, it causes waves. The energy and momentum in waves must come from the ship, which is manifested as a "wave drag" force on the ship. I known that this drag force (F) depends upon the ship speed (V), the fluid properties (p these

Answer 1

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