The Rankine cycle or Rankine steam cycle is a most commonly used technique in powerplants such as nuclear reactors and thermal power plants. This mechanism uses fuel to generate heat in the boiler, convert the water to steam, and expand this resulting steam through a turbine to generate electricity or to do useful work.
This cycle is a most preferred method for steam power plants. This electricity production process offers more value for the results of the process than the Carnot cycle. It can increase operating temperature, provide top-quality steam with low turbine moisture content, and make steam and water easy to handle. These are some positive factors that will help improve the overall efficiency of this method.
The Rankine cycle has a condenser, turbine, boiler, and pump. These components play a most vital role in the overall performance of the cycle.
Ideal Rankine Cycle
Saturated water in state 1 enters the water supply pump. The feed pump compresses the saturated liquid isentropically to the operating pressure of the boiler.
The temperature of the liquid increases slightly, whereupon the liquid changes from a saturated to a compressed state. The compressed liquid then enters the boiler from state 2. Here the liquid is transformed into superheated vapor at constant pressure. Therefore, the temperature of the steam rises sharply. The superheated steam from State 3 then passes through the turbine to do work. This is isentropic, which significantly reduces pressure and temperature. At the end of this process, the steam turned into a mixture of liquid and steam. Finally, the mixture from the fourth stage passes through the condenser to create a saturated liquid in a constant pressure process.
Actual Rankine Cycle
Ideal conditions cannot be achieved in a thermal power plant. Therefore, the efficiency always decreases in real situations. Fluid friction is one of those effects that lead to ineffective circulation. This leads to a pressure loss in the boiler and in the condensers.
The pressure drop in the boiler causes low pressure steam to enter the steam turbine, which reduces the operating efficiency. Due to the pressure loss in the turbine, the feed pump needs a little more inlet work than expected. Another major problem is heat loss throughout the cycle. This creates more energy requirements than ideal conditions.
What are the applications of the Rankine cycle?
- The Rankine cycle is used in a steam turbine to convert the thermal energy of the steam into useful mechanical work.
- The coal power plant also works on this cycle.
- This cycle also uses in nuclear power plants.
- Recently, many studies have focused on the use of the Rankine cycles to recover poor-quality waste heat.
