I want to know about design"single or twin screw pump"
formulas,diagram,figures.
for example I dont know how calculate dianeter and length of screw.thanks.
Not meaning to be discouraging - but why design what you can buy? Why don't you talk to your vendor about how s/he figures the length or diameter of the screw?
Also did you try doing a Google search? Here's a basic primer on single screw pumps: