有机无机化学化工热力学教学课件流体输送.pptxVIP

1 8.3 CENTRIFUGAL PUMPS Structure of centrifugal pumps 1. Centrifugal pump theory 2. Head-flow relations for an ideal pump ☆ 3. Head-work relation in an ideal pump 4. Actual performance of centrifugal pump 5. Loss of head; circulatory flow 6. Performance characteristics 7. Variation of pump characteristic curves (affinity law) 2 8. Multistage centrifugal pumps 9. Leakproof pumps 10. Pump priming泵的起动注水(affusion) **11. Piping system characteristic curve **12. Operating point (Duty point) **13. Flow rate control **14. Pump Selection 3 q H (a) (b) p P:operating point (a) Ｈe＝K＋Bqe2 (b) H=A-Bq2 12. Operating point (Duty point) 4 13. Flow rate control Usually the valve on the discharge line is used to control capacity of a centrifugal pump. The method of adjustment the flow rate: (1) Change characteristic curve of flow system. (2) Change characteristic curve of the pump. (3) Connect two pumps 5 (1) Change characteristic curve of flow system. K Bqe2 6 Exercise 1: 200C water is pumped from an open tank to a closed vessel with flow rate 45m3/h. The water level difference between the tank and the vessel is 14m. The gauge pressure in vessel is 49kPa. The size of the pipeline is Ф140×4.5mm diameter and 200m length (all kinds of friction loss are included ), the friction factor λ is 0.02. (1) Calculate the equation of pipeline head-capacity curve. 7 (2)  If a centrifugal pump, which has head-capacity curve : H=26-5.6×10－4Q2 (Q is in ‘m3/h’, and H is in ‘m’.) is used in the system, and the valve on the discharge line need to be partially closed to maintain the flow rate at 45m3/h. Calculate the new head-capacity curve equation of pipeline after the valve is partially closed. (3) Calculate the power loss due to the partially closing valve (assume pump efficiency is 70%). 8 (2) Change characteristic curve of the pump. 9 (3) Connect two pumps ----in parallel 10 11 (3) Connect two pumps ----in series 12 13 Compare the two kind of connecting manner Low friction loss H