A model pump has an impeller diameter of 30 cm. During a manufacturer's test, this model achieved an efficiency of 80%. A prototype in the same family (geometrically similar) is 10 times larger than this tested model. Under the same operating conditions dynamically similar to those in the model test, what most approximately will be the efficiency of the prototype pump? 74%

> | E9 docs.google.com/form تبديل الحساب Questions 7 نقاط Q1/ The power of 6-blade flat blade turbine agitator in a tank is a function of diameter of impeller, number of rotations of the impeller per unit time, viscosity and density of liquid. From a dimensional analysis, obtain a relation between the power and the four variables. 3. صفحة 2 من

4. A pump is required to pump fresh water at a flow rate of 5000 m³/hour against a head of 8 mat a speed of 1500 rev/min. It is planned to test a scale model with a head of 2 m at a flowrate of 100 m³/hour under dynamically similar conditions (but neglecting changes in ReynoldsNumber). Determine: a) The speed at which the model must be run.b) The scale that must be used for the model.c) The mechanical power required to drive the model pump is found to be 680W at theoperating point. Calculate the power required to drive the full scale pump.d) After the full scale pump is fitted into the system it is found that the pump head risereally needs to be increased by 30%. At what speed should the full scale pump now berun at to achieve this head rise and what will be the new ideal flow rate and powerconsumption in order to match this operating condition?e) Briefly comment on the main advantages and limitations of testing a scale model toprove the performance of a larger prototype.

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