Pumps (and compressors) are mechanical systems used in our day to day life. For example, a pump is used to raise pressure of liquids as in municipal water works and drainage system, agricultural and irrigation system, tube well , oil pumps in lubrication system, crude oil in petroleum industry, etc. In fact, a pump is used to increase pressure of liquid and can handle any kind of liquid, even contaminated with solid particulates to some degree. In power plants pump is used to handle ash slurry made with water, which is highly erosive in nature. In chemical industries, it is used to handle corrosive fluid, and so on. But its performance is affected by the increase in the viscosity of the liquid and the presence of contamination in it.
The function of the pump is to raise pressure of fluid and impart desirable velocity to it so that fluid may be transported from one place to another; more is the velocity the more is the flow rate and hence less time required for transportation. However, we have learnt that the head loss occurring in transportation increases as square of the flow velocity. It therefore requires pressure of the fluid at the outlet of the pump to be more to overcome these losses. Thus, a compromise is required between the pressure and the velocity at the pump exit. It must, however, be emphasized that the purpose of a pump is mainly to raise the pressure and not the velocity of the fluid. The Following chart gives a broad spectrum of the pumps available in the market.