![]() Note that about 90% of all electricity generation uses steam turbines. Since the steam turbine is a rotary heat engine, it is particularly suited to be used to drive an electrical generator. The basic operation of the steam turbine is similar to the gas turbine, except that the working fluid is water and steam instead of air or gas. Compression, heating, and expansion are continuous and occur simultaneously, unlike reciprocating engines. A steam turbine consists of a boiler ( steam generator), turbine, condenser, feed pump, and various auxiliary devices in its simplest form. In general, a steam turbine is a rotary heat engine that converts thermal energy contained in the steam to mechanical energy or electrical energy. These factors contribute to higher efficiency for the cycle. By condensing the working steam to a liquid (inside a condenser), the pressure at the turbine outlet is lowered, and the energy required by the feed pump consumes only 1% to 3% of the turbine output power. One of the major advantages of the Rankine cycle is that the compression process in the pump takes place on a liquid. In the case of the Rankine cycle, the Ideal Gas Law almost cannot be used (steam does not follow pV=nRT) therefore, all important parameters of water and steam are tabulated in so-called “ Steam Tables “. Moreover it has a very high heat of vaporization, which makes it an effective coolant and medium in thermal power plants and other energy industries. ![]() For example, water has the highest specific heat of any common substance – 4.19 kJ/kg K. While many substances could be used as the working fluid in the Rankine cycle (inorganic or even organic), water is usually the fluid of choice due to its favorable properties, such as its non-toxic and unreactive chemistry, abundance, and low cost, as well as its thermodynamic properties. In contrast to the Brayton cycle, the working fluid in the Rankine cycle undergo the phase change from a liquid to vapor phase and vice versa. In this cycle, the heat is supplied externally to a closed loop, which usually uses water (in a liquid and vapor phase) as the working fluid. The Rankine cycle is an idealized thermodynamic cycle of a constant pressure heat engine that converts part of heat into mechanical work. The Rankine cycle was named after him and describes the performance of steam turbine systems, though the theoretical principle also applies to reciprocating engines such as steam locomotives. He contributed to thermodynamics, particularly focusing on the first of the three thermodynamic laws, together with Rudolf Clausius and William Thomson (Lord Kelvin). Rankine developed a complete theory of the steam engine and indeed of all heat engines. In 1859, a Scottish engineer, William John Macquorn Rankine, advanced the study of heat engines by publishing the “ Manual of the Steam Engine and Other Prime Movers”. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |