Right now also in centrifugal due to high rpm since it is directly coupled to electric motor the pump creates partial vacuum which means the liquid will certainly flow through vacuum hence the liquid will end up being recieved in the centrifugal pumps suction and because the impeller rotates the liquid will be 
displaced away forward with a particular energy.
A vacuum pump has the inlet hooked up to 1 or both valve covers, sometimes the valley pan. It SUCKS the atmosphere from the engine, therefore reducing the atmosphere pressure build-up created by blow due to Centrifugal Vacuum Pump combustion gases going past the piston rings into the pan.