大学课件-化工原理-第2章流动小结.ppt

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1、Fluid characters Force exerted on the fluid mass force surface force Types of Fluids(1) Incompressible and compressible fluid (2) Newtonian and non-Newtonian fluid (3) Ideal and real fluid,For an incompressible fluid,Continuity (Mass conservation ),The Fluid in Motion,（1）Static fluid static fluid eq

2、u.,（2）Ideal fluid- Bernoulics equ.,(3) Real fluid- Momentum equation,Momentum Changes in a Fluid,Momentum equation,Fluid flow in pipe Stream line Turbulent flow Transitional flow,The Nature of Fluid Flow,laminar sub-layer,Boundary layer 99% u,Boundary layer (chapter 11),separation of boundary layer,

3、（1）viscosity （2）pressure gradient is negative （3）kinetic energy exhaust during flow,Flow in a Pipe,Developing flow,Fully developed flow,Velocity Distribution, Streamline Flow,The kinetic energy per unit mass :,Velocity Distribution, Turbulent Flow,The kinetic energy per unit mass :,Friction loss,Moo

4、dy friction factor,Fanning friction factor Darcy friction factor,Laminar motion,Friction factor,Hagen-Poiseuille equation,Turbulent motion,Transitional region,Fully turbulent flow,Miscellaneous Friction Losses,The friction loss occurring as a result of Sudden enlargement Sudden contraction Various p

5、ipe fittings-elbow, union, valves (gate, globe, needle),Pressure Measuring Devices,The simple manometer U-tube The well-type manometer The inclined manometer The inverted manometer,Measurement of Fluid Flow,The Pitot tubeThe Orifice MeterThe Venturi MeterRotameter,Momentum equation,Pumping Equipment

6、 For Liquids,The positive displacement type Centrifugal pumps,Reciprocating pump (往复泵） The piston pump(活塞泵） The plunger or ram pump（柱塞泵） The diaphragm pump（隔膜泵） The metering pump（计量泵） Positive displacement rotary pump（转动泵） The gear pump（齿轮泵） The screw pump（螺杆泵）,The positive displacement type,The Cen

7、trifugal Pump The principle and structure Air bind（气缚）,Virtual head,He,Volumetic rate Q,N shaft work power,Ne effective power,Efficiency ,Hydraulic efficiency, Volumetric efficiency, Mechanical efficiency,Operating characteristics,Factors on performance of the pumpPhysical properties of liquid to be

8、 deliveredRotation speedImpeller diameter,Cavitation（气蚀）,NPSH (net positive suction head) (净正吸上高度或汽蚀余量）,(a) NPSHr(必需汽蚀余量),(b) NPSHa (装置汽蚀余量),The height installation of the pump (安装高度） Uprightness height between inlet of the pump and the level of the liquid delivered The maximum height installation Z

9、max,Allowable height installation,System characteristics,Factors affecting system characteristics 1）A (1) z (2) ,2）B,High resistance,Low resistance,1) To adjust the valve,system characteristics vary pump characteristics be fixed,Resistance on valve,Adjustment of flowrate,Not be used frequently.,2) T

10、o change pump characteristics,Pump operates in Parallel,Duty point,Pump operates in Series,Duty point,Low resistance pipeline-in parallel high resistance pipeline-in series,Pumping Equipment for Gases,According to the outlet pressure and the compression ratio r r = outlet pressure / inlet pressure (absolute) Fans (通风机)： P 1.471104Pa(g)， r 2.942105Pa(g) ，r 4,