Lecture 12 Pumps Flashcards
definition of a pump
machine : move liquid: raise pressure
four reasons for pumping
pressure
velocity
friction
elevation
3 types of pumps
gravity
positive displacement
kinetic
positive displacement cpump description and 4 examples
part of liquid is trapped and displaced by applicatrion of a force
diaphragm
reciprocating hand pump
rotary (da vinci wheel)
rope pump
when to use PD
high viscosity
high presure
low velocity
fragile solids
three types of centrifugal pumps (which are kinetic pumps)
radial
axial
mixed
how does cavitation occur
absolute presure at pump inlet falls below vapour pressure of fluid
bubbles form
they reach impeller , increased pressure, collapse, large localised pressure
three types of efficencies
hydraulic
mechanical
volumetric
hydraulic efficeincy based on
friction
accel/deccel
change in directions
what is mechanical efficiency
power gained by fluid compared to power upplied by shaft
volumetric efficiency
leakage and backflow