### What is Pump?

A pump is mechanical device which is used to transfer fluid from one point to another point, usually from lower elevation to higher elevation. The pump performs this action with the help of a prime movers which are basically electrical motor, IC engine, etc. Based on the type of pump different mechanism are used to transfer the fluid, however the conversion of mechanical energy to pressure (potential) energy remains the fundamental.

Why is pump required to transfer the fluid from low level to high level ?

We know that the fluid at higher level have high potential energy (p = ρ g h), as the fluid is at height “h” it has potential energy, which gets converted to kinetic energy ( ½ m v2 ), the flow due to “v” is generated. But when the same fluid is at lower level, say ground level ‘h=zero’ the potential energy is nil. So, fluid cannot flow on its own as the velocity will not be generated. Hence and external energy is required to push the fluid at height h and generate flow, which is why pumps are used to transfer fluid from low level to high level.

Below is the description of various paths where pump may be required for transfer of fluid. (Point A to Point B).

Identify the case where the pump will be required (For water) Case 1 – The ideal pumping case, here the point A and Point B are clearly at different elevation, B is at higher elevation than A. Hence, the pump will be required to transfer the fluid.

Case 2 – The point B and Point A are at different elevation, but since we need to transfer fluid from A to B and B is at lower elevation than A the pump is not required. The fluid will be move due to gravity as explained earlier.

Case 3 – The point A and B are at same level. Does that mean the pump is not required? Not clearly the case as the path that the fluid must follow is at different elevation. Let’s say point C the highest point in the path, the pump will be required to transfer the fluid from point A to Point C after that the fluid will travel itself as explained earlier.

Case 4 – The point A is at higher level than point B and no intermediate path points are at higher elevation than A, the pump will not be required for fluid transfer from A to B.