Lämpökoneistot

Lämpökoneistot, or heat engines, are devices that convert thermal energy into mechanical work. This conversion process is governed by the principles of thermodynamics, particularly the second law. The fundamental operation of a heat engine involves absorbing heat from a high-temperature source, converting a portion of that heat into useful work, and rejecting the remaining heat to a low-temperature sink.

The efficiency of a heat engine is a crucial parameter, defined as the ratio of the work output to the heat input. The theoretical maximum efficiency for any heat engine operating between two temperatures is given by the Carnot efficiency, which depends solely on the temperatures of the hot and cold reservoirs. In practice, real heat engines have efficiencies lower than the Carnot limit due to irreversible processes such as friction and heat loss.

Common examples of heat engines include the internal combustion engine found in most vehicles, steam engines used in power plants and historical transportation, and jet engines used in aircraft. These engines operate on various thermodynamic cycles, such as the Otto cycle for gasoline engines, the Diesel cycle for diesel engines, and the Rankine cycle for steam engines. The continuous operation of a heat engine requires a working fluid that undergoes a cycle of expansion and compression, thereby producing mechanical power. The development and improvement of heat engines have been central to technological advancements and industrial revolutions throughout history.