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A heat engine is a system that transfers thermal energy to do mechanical or electrical work. [1] [2] While originally conceived in the context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, particularly electrical, since at least the late 19th century.
In the history of science, the mechanical equivalent of heat states that motion and heat are mutually interchangeable and that in every case, a given amount of work would generate the same amount of heat, provided the work done is totally converted to heat energy. The mechanical equivalent of heat was a concept that had an important part in the ...
A heat engine is a system that performs the conversion of a flow of thermal energy (heat) to mechanical energy to perform mechanical work. [ 32 ] [ 33 ] A thermocouple is a temperature-measuring device and a widely used type of temperature sensor for measurement and control, and can also be used to convert heat into electric power.
The main feature of thermodynamic diagrams is the equivalence between the area in the diagram and energy. When air changes pressure and temperature during a process and prescribes a closed curve within the diagram the area enclosed by this curve is proportional to the energy which has been gained or released by the air.
For the three examples given above: 1) Heat can be transferred from a region of lower temperature to a higher temperature in a refrigerator or in a heat pump. These machines must provide sufficient work to the system. 2) Thermal energy can be converted to mechanical work in a heat engine, if sufficient heat is also expelled to the surroundings.
A generator converts mechanical energy into electrical energy. [19] A hydroelectric powerplant converts the mechanical energy of water in a storage dam into electrical energy. [20] An internal combustion engine is a heat engine that obtains mechanical energy from chemical energy by burning fuel. From this mechanical energy, the internal ...
Mechanical efficiency, where one form of mechanical energy (e.g. potential energy of water) is converted to mechanical energy ; Thermal efficiency or Fuel efficiency, useful heat and/or work output per input energy such as the fuel consumed; 'Total efficiency', e.g., for cogeneration, useful electric power and heat output per fuel energy ...
Q H = W + Q C = heat exchanged with the hot reservoir. η = W / (Q C + Q H) = thermal efficiency of the cycle If the cycle moves in a clockwise sense, then it is a heat engine that outputs work; if the cycle moves in a counterclockwise sense, it is a heat pump that takes in work and moves heat Q H from the cold reservoir to the hot reservoir.