The Rankine cycle is a thermodynamic cycle. Like other thermodynamic cycles, the maximum efficiency of the Rankine cycle is given by calculating the maximum efficiency of the Carnot cycle. It is named after William John Macquorn Rankine, a Scottish polymath. In engineering and thermodynamics, a heat engine performs the conversion of heat energy to mechanical work by exploiting the temperature gradient between a hot source and a cold sink. Heat is transferred from the source, through the working body of the engine, to the sink, and in this process some... The Atkinson cycle engine is a type of Internal combustion engine invented by James Atkinson in 1882. ... The Brayton cycle is a cyclic process generally associated with the gas turbine. ... A heat engine is an engine that uses heat to produce mechanical work by carrying a working substance through a cyclic process. ... In a combined cycle power plant, or combined cycle gas turbine (CCGT) plant, a gas turbine generator generates electricity and the waste heat from the gas turbine is used to make steam to generate additional electricity via a steam turbine, this last step enhances the efficiency of electricity generation. ... The Crower six-stroke engine is a concept under development by Bruce Crower, known for the invention and manufacture of many devices now used in automotive acceleration racing (see National Hot Rod Association and drag racing). ... The Diesel cycle is the combustion process of a type of internal combustion engine, in which the burning of the fuel is triggered by the heat generated in first compressing air in the piston cavity, into which is then injected the fuel - as opposed to it being ignited by a... This article or section seems not to be written in the formal tone expected of an encyclopedia entry. ... The Kalina cycle is a thermodynamic cycle for converting thermal energy to mechanical power which utilizes working fluid comprised of at least two different components and a ratio between those components is varied in different parts of the system to increase thermodynamical reversibility and therefore increase overall thermodynamic efficiency. ... The Lenoir cycle is an idealised thermodynamic cycle for the pulse jet engine. ... In engineering, the Miller cycle is a combustion process used in a type of four-stroke internal combustion engine. ... Dual Combustion Cycle(Also known as limited pressure cycle or mixed cycle) is a combination of Otto Cycle and Diesel Cycle, in a way , that heat is added partly at constant volume and partly at constant pressure. ... The four-stroke cycle of an internal combustion engine is the cycle most commonly used for automotive and industrial purposes today (cars and trucks, generators, etc). ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... A Stirling engine and generator set with 55 kW electrical output, for combined heat and power applications. ... The two-stroke cycle of an internal combustion engine differs from the more common four-stroke cycle by having only two strokes (linear movements of the piston) instead of four, although the same four operations (intake, compression, power, exhaust) still occur. ... ‹ The template below has been proposed for deletion. ... Thermodynamic efficiency (e) is defined as: where W is the absolute value of the work done in one thermodynamic cycle. ... A heat engine is an engine that uses heat to produce mechanical work by carrying a working substance through a cyclic process. ... William John Macquorn Rankine (July 2, 1820 - December 24, 1872) was a Scottish engineer and physicist. ...

This article will deal with the Rankine cycle from an engineering point of view. Engineering is the application of scientific and mathematical principles to develop economical solutions to technical problems, creating products, facilities, and structures that are useful to people. ...

Processes of the Rankine cycle

Image File history File links TS diagram of Rankine cycle extracted from http://tis. ...

There are four processes in the Rankine cycle, each changing the state of the working fluid. These states are identified by number in the diagram above.

• Process 4-1: First, the working fluid is pumped (ideally isentropically) from low to high pressure by a pump. Pumping requires a power input (for example mechanical or electrical).
• Process 1-2: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a saturated vapor. Common heat sources for power plant systems are coal, natural gas, or nuclear power.
• Process 2-3: The superheated vapor expands through a turbine to generate power output. Ideally, this expansion is isentropic. This decreases the temperature and pressure of the vapor.
• Process 3-4: The vapor then enters a condenser where it is cooled to become a saturated liquid. This liquid then re-enters the pump and the cycle repeats.

The exposed Rankine cycle can also present vapor overheating^[1] , which reduces the amount of liquid condensed after the expansion in the turbine. An isentropic process (a combination of the Greek word iso -same- and entropy) is one during which the entropy of working fluid remains constant. ... An electrically-driven waterworks pump near the Hengsteysee, Germany. ... Coal Coal (IPA: ) is a fossil fuel extracted from the ground by underground mining or open-pit mining (surface mining). ... Natural gas is commonly referred to as gas. ... A nuclear power station. ... WWII era steam turbine used for ship propulsion. ... The term condenser has the following meanings: In electronics, it is another (old-fashioned) word for capacitor. ...

Description

Rankine cycles describe the operation of steam heat engines commonly found in power generation plants. In such vapour power plants, power is generated by alternately vaporizing and condensing a working fluid (in many cases water, although refrigerants such as ammonia may also be used). A heat engine performs the conversion of heat energy to work by exploiting the temperature gradient between a hot source and a cold sink. Heat is transferred to the sink from the source, and in this process some of the heat is converted into work. ... A power station (also power plant) is a facility for the generation of electric power. ... Evaporation is the process whereby atoms or molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state. ... Condensation is the change in matter1 of a substance to a denser phase, such as a puppy gas (or vapor) to a liquid. ... A refrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back. ...

The working fluid in a Rankine cycle follows a closed loop and is re-used constantly. Water vapour seen billowing from power plants is evaporating cooling water, not working fluid. (NB: steam is invisible until it comes in contact with cool, saturated air, at which point it condenses and forms the white billowy clouds seen leaving cooling towers). Vapor (US English) or vapour (British English) is the gaseous state of matter. ... In physical chemistry, and in engineering, steam refers to vaporized water. ...

Variables

	heat input rate (energy per unit time)
	mass flow rate (mass per unit time)
	mechanical power used by or provided to the system (energy per unit time)
η	thermodynamic efficiency of the process (power used for turbine per heat input, unitless)
h1,h2,h3,h4	these are the "specific enthalpies" at indicated points on the T-S diagram

Mass flow rate is the movement of mass per time. ... In physics, power (symbol: P) is the rate at which work is performed. ... Enthalpy (symbolized H, also called heat content) is the sum of the internal energy of matter and the product of its volume multiplied by the pressure. ...

Equations

Each of the first four equations^[1] are easily derived from the energy and mass balance for a control volume. The fifth equation defines the thermodynamic efficiency of the cycle as the ratio of net power output to heat input. A mass balance (also called a material balance) is an accounting of material entering and leaving a system. ... Thermodynamic efficiency (e) is defined as: where W is the absolute value of the work done in one thermodynamic cycle. ...

Real Rankine cycle (non-ideal)

In a real Rankine cycle, the compression by the pump and the expansion in the turbine are not isentropic. In other words, these processes are non-reversible and entropy is increased during the two processes (indicated in the figure as ΔS). This somewhat increases the power required by the pump and decreases the power generated by the turbine. It also makes calculations more involved and difficult. An electrically-driven waterworks pump near the Hengsteysee, Germany. ... WWII era steam turbine used for ship propulsion. ... In thermodynamics, entropy, symbolized by S, is a state function of a thermodynamic system defined by the differential quantity , where dQ is the amount of heat absorbed in a reversible process in which the system goes from the one state to another, and T is the absolute temperature. ... In physics, power (symbol: P) is the rate at which work is performed. ...

Variations of the basic Rankine cycle

Two main variations of the basic Rankine cycle are used in modern practice.

Rankine cycle with reheat

In this variation, two turbines work in series. The first accepts vapor from the boiler at high pressure. After the vapor has passed through the first turbine, it re-enters the boiler and is reheated before passing through a second, lower pressure turbine. Among other advantages, this prevents the vapor from condensing during its expansion which can seriously damage the turbine blades. WWII era steam turbine used for ship propulsion. ... Evaporation is the process whereby atoms or molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state. ... A boiler is a closed vessel in which water or other fluid is heated under pressure. ... Condensation is the change in matter1 of a substance to a denser phase, such as a puppy gas (or vapor) to a liquid. ...

Regenerative Rankine cycle

The regenerative Rankine cycle is so named because after emerging from the condenser (possibly as a subcooled liquid) the working fluid is heated by steam tapped from the hot portion of the cycle. This increases the average temperature of heat addition which in turn increases the thermodynamic efficiency of the cycle. If the temperature of the liquid is lower than the Saturation Temperature for the existing pressure, it is called either a Subcooled liquid (implying that the temperature is lower than the Saturation Temperature for the given pressure) or a Compressed liquid (implying that the pressure is greater than the Saturation... In physical chemistry, and in engineering, steam refers to vaporized water. ... In thermodynamics, temperature is the physical property of a system that underlies the common notions of hot and cold —something that is hotter has the greater temperature. ... In physics, heat, symbolized by Q, is defined as energy in transit. ... Thermodynamic efficiency (e) is defined as: where W is the absolute value of the work done in one thermodynamic cycle. ...

References

• ^Van Wyllen 'Fundamentals of thermodynamics' (ISBN 85-212-0327-6)
• Moran & Shapiro 'Fundamentals of Engineering Thermodynamics' (ISBN 0-471-27471-2)
• Wikibooks Engineering Thermodynamics

External links

Rankine cycle on the Mathcad Application Server http://twt.mpei.ac.ru/MAS/Worksheets/Rankine3D.mcd

Organic Rankine Cycle for electric power generation http://www.turboden.it/orc.asp