The main difference between the Rankine cycle and Brayton cycle is that the Rankine cycle is a vapour cycle, whereas the Brayton cycle is a cycle between liquid and vapour phases.
Both the Rankine cycle and the Brayton cycle are thermodynamic cycles. The thermodynamic cycle is a series of different thermodynamic processes involving work and heat transfer inside and outside the system, with variable temperature and pressure conditions.
What is Rankine Cycle?
The Rankine cycle is a model that predicts the performance of steam turbines. The model is a vapour cycle. This is an ideal model for a thermodynamic cycle with a phase change in the heat engine.
There are four major components to the Rankine cycle and we can ignore the friction losses from any of these four components.
The Rankine cycle is a steam engine, which is used for boiling water to evaporate and then condensed for reuse, thus becoming a closed cycle.
Rankine cycles can be operated in open or closed circuits, as is more common for previous industrial applications. In this process, the heat transfer fluid (HTF) is heated by burning the fuel to produce high-pressure steam and then cooled by spreading it in a condenser.
A condenser will be required when the Rankine cycle is in an open circuit. Otherwise, it will create so much pressure that the system will burst due to its own weight.
The theory behind the Rankine cycle is used to generate electricity in thermal power generation plants. The power generated by this process depends on the temperature difference between the heat source and the cold source.
If the difference is large enough, we can extract more energy than heat energy.
In general, the heat source used here can be either nuclear fusion or combustible fossil fuel. The higher the temperature, the better the source. Cold sources, meanwhile, include cold towers targeting water.
What is Brayton Cycle?
The Brayton cycle is a jet engine; the air is sucked, compressed and then released into the air, thus forming an open bicycle. The Brayton cycle is a thermodynamic cycle used to convert heat into mechanical work. It is named after the American engineer George Breton, who invented it in 1878. This process can be used to replace a turbine engine or other device that uses thermal energy for useful work.
The Brayton cycle is a thermodynamic cycle that describes the operation of a constant pressure heat engine. The cycle usually operates as an open system. But, for the requirements of thermodynamic analysis, we consider it as a closed system operation in which exhaust gases are reused during the process. The process was named after scientist George Brayton.
The cycle consists of three components. They are compressor, mixing chamber and expander. Brayton engines are generally of the turbine engine type.
Difference Between the Rankine Cycle and the Brayton Cycle-
The working fluid undergoes a phase change in the Rankine cycle while the Brayton cycle undergoes no phase change. The working fluid is always in the gaseous phase.
The Rankine cycle is a model that describes the performance of a steam turbine, while the Brayton cycle is a thermodynamic cycle that describes the operation of a constant pressure heat engine.
The main difference between the Rankine cycle and the Brayton cycle is that the Rankine cycle is the vapour cycle, while the Brayton cycle is a cycle between the liquid and the vapour phases.
In addition, another difference between the Rankine cycle and the Brayton cycle is that the Rankine cycle has four components, whereas the Brayton cycle has only three components.
The Brayton cycle consists of two reversible isobaric processes and the Rankine cycle consists of two reversible adiabatic processes.
In the case of the Rankine cycle, both the pump and the steam turbine, and in the case of the Brayton cycle, the compressor and the gas turbine operate at the same pressure difference.
The average specific gravity of the air handled by the compressor is less than the gas in the gas turbine in the Brayton cycle so the work done by the gas turbine is more than the input of the compressor work whereas in the case of the Rankine cycle, the specific water in the pump.
The weight is much less than the steam dissipated in steam turbines, so steam power plants are more popular than gas turbine plants for generating electricity.
The Brayton cycle operates at a pressure ratio higher than the Rankine cycle for the same capacity.
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Abhishek Tiwary is a blogger by passion and a Quality Engineer by profession. He completed his B.Tech degree in the year 2017. Now working in a reputed firm. He loves to share his knowledge with others.