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Review from Lecture 1: Pumps

Review from Lecture 1: Pumps. Difference between pumps, fans, and compressors Mechanical Efficiency. Dr. C. L. Jones Biosystems and Ag. Engineering . Review from Lecture 1: Pumps. Two types. Dr. C. L. Jones Biosystems and Ag. Engineering . Review from Lecture 1: Pumps.

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Review from Lecture 1: Pumps

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  1. Review from Lecture 1:Pumps • Difference between pumps, fans, and compressors • Mechanical Efficiency Dr. C. L. Jones Biosystems and Ag. Engineering

  2. Review from Lecture 1:Pumps • Two types Dr. C. L. Jones Biosystems and Ag. Engineering

  3. Review from Lecture 1:Pumps • Recip Pumps have a crank, connecting rods, and pistons or plungers • Rotary gear pumps provide more constant output • Recip Pump eqtns. Dr. C. L. Jones Biosystems and Ag. Engineering

  4. Review: Dynamic Pumps • Centrifugal • Relative simplicity • Can handle fluids containing suspended solids • Ease of maintenance…good for food products • 2 parts: impeller and casing • Radial, mixed, axial flow Dr. C. L. Jones Biosystems and Ag. Engineering

  5. Performance Curves Dr. C. L. Jones Biosystems and Ag. Engineering

  6. Performance Curves Dr. C. L. Jones Biosystems and Ag. Engineering

  7. Review: Centrifugal Pump Affinity Laws Dr. C. L. Jones Biosystems and Ag. Engineering

  8. Centrifugal Pump Affinity Laws Dr. C. L. Jones Biosystems and Ag. Engineering

  9. Centrifugal Pump Fundamentals • Static head: the height of a column of liquid • Units: feet or meters • Pump imparts velocity to liquid…velocity energy becomes pressure energy leaving the pump. Head developed = vel. energy at the impeller tips. • Why do we use “feet” or “head” instead of “psi” or “pressure”? • Pump with impeller D will raise a liquid to a certain height regardless of weight of liquid Dr. C. L. Jones Biosystems and Ag. Engineering

  10. Converting pressure to head in feet Dr. C. L. Jones Biosystems and Ag. Engineering

  11. Suction Lift Dr. C. L. Jones Biosystems and Ag. Engineering

  12. Suction Head Dr. C. L. Jones Biosystems and Ag. Engineering

  13. Static Discharge Head • Static Discharge Head = vertical distance from pump centerline to the point of free discharge or the surface of the liquid in the discharge tank. Dr. C. L. Jones Biosystems and Ag. Engineering

  14. Total Static Head • Vertical distance between the free level of the source of supply and the point of free discharge or the free surface of the discharge liquid. Dr. C. L. Jones Biosystems and Ag. Engineering

  15. Total Dynamic Suction Lift or Head • (fluid below suction) Static suction lift - velocity head at suction + total friction head in suction line • (fluid above suction) Static suction head + velocity head at pump suction flange – total friction head in suction line • Velocity head = energy of liquid due to motion, Usually insignificant Dr. C. L. Jones Biosystems and Ag. Engineering

  16. Total Dynamic Discharge Head • Static discharge head + velocity head at pump discharge flange plus discharge line friction Total Dynamic Discharge Head (TH or TDH) (this is what we design for!!!) • Total dynamic discharge head – total dynamic suction head (tank above suction)…. Or…. • Total dynamic discharge head + total dynamic suction lift (tank below suction) Dr. C. L. Jones Biosystems and Ag. Engineering

  17. Total Dynamic Discharge Head (TH or TDH) (this is what we design for!!!) TDH includes friction losses due to piping and velocity Dr. C. L. Jones Biosystems and Ag. Engineering

  18. One last item to consider…NPSH (net positive suction head) Dr. C. L. Jones Biosystems and Ag. Engineering

  19. NPSHR Dr. C. L. Jones Biosystems and Ag. Engineering

  20. NPSHA Dr. C. L. Jones Biosystems and Ag. Engineering

  21. NPSHA Dr. C. L. Jones Biosystems and Ag. Engineering

  22. Capacity, Power, Efficiency • Capacity Q, gpm = 449 x A, ft2 x V, ft/sec • Where A = cross-sectional area of the pipe in ft2 V = velocity of flow in feet per second • Bhp = actual power delivered to pump shaft by driver • Whp = pump output or hydraulic horsepower Dr. C. L. Jones Biosystems and Ag. Engineering

  23. Pump Efficiency • Ratio of whp to bhp: Dr. C. L. Jones Biosystems and Ag. Engineering

  24. System Example: 80 ft of 4” ID galv. iron pipe with 3 elbows, 75’ lift, pumps from an open tank, discharges through a pipe to a tank at atm. Pressure (find rate, imp. dia., eff., motor size, rpm) • Ratio of whp to bhp: Dr. C. L. Jones Biosystems and Ag. Engineering

  25. Homework Handout

  26. Questions??? Dr. C. L. Jones Biosystems and Ag. Engineering

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