OIL IMMERSION HEATER : BRAKE DRUM WOOD HEATER : HOME SOLAR WATER HEATER.
Oil Immersion Heater
a heating device used to maintain a constant temperature in the mash tun.
An electric heating element that is positioned in the liquid to be heated
Electric heating is any process in which electrical energy is converted to heat. Common applications include heating of buildings, cooking, and industrial processes.
a heating element that is immersed in the liquid that is to be heated (as in a hot-water tank)
Any of various thick, viscous, typically flammable liquids that are insoluble in water but soluble in organic solvents and are obtained from animals or plants
Petroleum
a slippery or viscous liquid or liquefiable substance not miscible with water
anoint: administer an oil or ointment to ; often in a religious ceremony of blessing
A viscous liquid derived from petroleum, esp. for use as a fuel or lubricant
cover with oil, as if by rubbing; "oil the wooden surface"