A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by echanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps.

A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall to prevent mixing or they may be in direct contact.

A boiler is a closed vessel in which water or other fluid is heated. The fluid does not necessarily boil. (In North America the term ``furnace`` is normally used if the purpose is not actually to boil the fluid.) The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including central heating, boiler-based power generation, cooking, and sanitation.