The same system is used in larger-scale refrigerating and air-conditioning plants and in heat pumps, where refrigerant is either condensed or evaporated and air is either heated or cooled, depending on the use. Similarly , hot-water and steam-heating or chilled-water and brine-cooling systems are used to heat or cool air for comfort systems in buildings, planes, ships, etc. Air coolers are used for lubricant oil-cooling systems on aircraft, ships, vehicles, and stationary gas-turbine or diesel-engine power generators.