It is then reheated to 400c and expands to 10 kpa in the lowpressure turbine. The reheat raises the average temperature at which you add heat. The efficiency of the rankine cycle can increase by expanding the steam in the turbine in two stages, and reheat it in between. In simple rankine cycle, after the isentropic expansion in turbine, steam is directly fed into condenser for condensation process. Chapter9, lesson c ideal rankine cycle with reheat.
A steam power plant operates on an ideal reheat regenerative rankine cycle and has a net power output of 80 mw. In fact, it is like a brayton cycle with an infinite number of reheat and intercooler stages in the cycle. Software solutions vapor power cycles rankine cycle is a supplement to the partii of the popular, free ebook series on applied thermodynamics. All the steam turbine thermal power plants what we are seeing today is centered around the qualitative thermodynamics of rankine cycle, which is the vapor standard cycle for the same.
Determine the fraction of steam extracted from the turbine and the thermal efficiency of the cycle. In this reheat cycle, steam is expanded isentropically to an intermediate pressure in a highpressure turbine stage i and sent back to the boiler, where it is reheated at constant pressure to the inlet temperature of the highpressure turbine. Gas power cycles our study of gas power cycles will involve the study of those heat engines in which the working fluid remains in the gaseous state throughout the cycle. Regenerative cycle definition is a cycle in a steam engine using heat that would ordinarily be lost. We continue with the reheat cycle developed in chapter 8a, and examine the effect of adding a regenerative heat exchanger in the form of an open feedwater heater, as shown below. The rankine cycle is an idealized thermodynamic cycle of a heat engine that converts heat into. In this example the hp turbine expands the steam from 15 mpa to 1 mpa, and the steam is subsequently reheated back to 600c before being expanded in the lp turbine to 10 kpa. Answer to consider an ideal reheatregenerative rankine cycle with one open feedwater heater. Comparative performance of reheat and regenerative steam. Various items for this system per unit of mass flow rate through the boiler are to be determined. Jan 14, 2010 a reheat rankine cycle steams enter the highpressure turbine at 12. Answer to consider an ideal reheat regenerative rankine cycle with one open feedwater heater. In this case the turbine operates at steady state with inlet conditions of 6 mpa, t 275.
Exercise 1consider a steam power plant operating on the ideal rankine cycle. Steam power plant cycles simple vapor cycle and its components. The schematic of an ideal reheat rankine cycle is shown on the left with its ts diagram. Rankine cycle and its variations are used in steam power plants, marine applications etc. Consider an ideal combined reheat and regenerative cycle in which steam enters the highpressure turbine at 3. Pdf power plant lecture notes chapter2 steam power plant. Given a rankine cycle with reheat operating with the following conditions. Consider an ideal combined reheat and regenerative cycle in which. Rankine cycle with reheat and regeneration mechanical. Jan 17, 2017 lecture series on steam and gas power systems by prof. The simple cycle efficiencies of early gas turbines were practically doubled by incorporating intercooling, regeneration or recuperation, and reheating.
Expand the steam in the turbine in two stages, and reheat it in between reheat the ideal reheat rankine cycle. Further addition of energy causes evaporation of the liquid until. Rankine cycle with regeneration and reheat pdf file 627. The ideal regenerative reheat cycle using an open feedwater heater. The back work ratio of a gasturbine cycle improves as a result of intercooling and reheating. The total heat input and total turbine work output for a reheat cycle become water is typically used as the working. The rankine cycle is an idealized thermodynamic cycle of a heat engine that converts heat into mechanical work while undergoing phase change. Inlet and outlet pressure, temperature of boiler, turbine, pump and condenser. Feb 25, 20 tutorial questions reheat rankine cycle 1. In other words, modify the simple ideal rankine cycle with reheat process. Pdf power plant lecture notes chapter2 steam power. We often study the ideal cycle in which internal irreversibilities and complexities the.
Reheating is a practical solution to the excessive moisture. Lecture series on steam and gas power systems by prof. The regeneration cycle increases the thermal efficiency, but it is affected by the moisture at the outlet of the turbine, therefore, it is not uncommon to combine a reheat cycle and a regeneration cycle. As in gasturbine plants, the thermal efficiency of a steam power plant is raised by means of heat regeneration. The reheat process brings the states at the lower pressure further out in the superheated vapor region and thus raises the quality if twophase in the last turbine section. Water is the working fluid in an ideal rankine cycle with reheat. View homework help chapter 9 rankine cycle problems solutions. Cycle efficiency with reheat northwestern university. Let assume the rankine cycle, which is the one of most common thermodynamic cycles in thermal power plants. Power plant lecture notes chapter2 steam power plant cycles. The condenser pressure, the net power output, and the thermal efficiency are to be determined. Pump in reheat rankine cycle, there are essentially two turbines, one is high pressure turbine hpt and the other is low pressure turbinelpt.
If a steam power plant is operated on a rankine cycle without steam reheating and if complete regeneration of heat is accomplished, then the thermal efficiency of this rankine cycle will be equal to the thermal efficiency of a carnot cycle. The differences of reheat cycle compared to regenerative cycle are discussed as follows. Sep 06, 2019 the rankine cycle is the fundamental operating cycle of all power plants where an operating fluid is continuously evaporated and condensed. Multiple reheat stages rankine cycle the average temperature at which heat is transferred during reheating increases as the number of reheat stages is. Highpressure liquid enters the boiler from the feed pump 12 and is heated to the saturation temperature 2. In this case assume a simple cycle without reheat and without with condensing steam turbine running on saturated steam dry steam. The steam is reheated to 750 o f before it enters the low pressure turbine where the steam is let down to 20 psia. Thus, the thermal efficiency of the cycle can be determined from. Compared to the brayton cycle which uses adiabatic compression and expansion, an ideal ericsson cycle consists of isothermal compression and expansion processes. Calculate the cycle thermal efficiency and the moisture content of the steam leaving the lowpressure turbine.
Aug 06, 2015 first solved problem of rankine reheat cycle. Class problem reheatregenerative rankine cycle with open and closed feedwater heaters consider a steam power plant that operates on an ideal reheatregenerative rankine cycle with one open feedwater heater, one closed feedwater heater, and. A reheat rankine cycle steams enter the highpressure turbine at 12. It was also used to study the performance of reciprocating steam engines. Brayton cycle reading problems 98 910 978, 984, 9108 open cycle gas turbine engines after compression, air enters a combustion chamber into which fuel is injected the resulting products of combustion expand and drive the turbine combustion products are discharged to the atmosphere. Brayton cycle with reheat, regeneration and intercooling. Determine the power output, heat transfer rate input required. Example consider a regenerative cycle using steamas the working fluid. Steam leaves the boiler and enters the turbine at 4 mpa and 400c. Water is the working fluid in an ideal rankine cycle. What is difference between ideal rankine cycle and reheat. The pressure and temperature at the turbine inlet are 1200 lb f in 2 and f, respectively, and the condenser pressure is 1 lb f in 2.
Among the proposed solutions, the organic rankine cycle orc system is the most widely used. Steam enters the high pressure turbine at 10 mpa and 550c and leaves at 0. In reheat rankine cycle, the following improvements are made to increase the efficiency of rankine cycle. We will find that this system does result in an increase in thermal efficiency by preheating the. Steam enters the turbine at 3 mpa and 350c and is condensed in thecondenser at a pressure of 10 kpa. The simple rankine cycle 97c the four processes that make up the simple ideal cycle are 1 isentropic compression in a pump, 2 p constant heat addition in a boiler, 3 isentropic expansion in a turbine, and 4 p constant heat rejection in a condenser. Boiler, turbine, condenser, pump, carnot cycle for steam, disadvantages of carnot cycle application, rankine cycle and. Regenerative cycle definition of regenerative cycle by. An important number of new solutions have been proposed to generate electricity from alternative heat source, such as lowtemperature or lowpower heat sources. We will occasionally encounter reheated cycles whose efficiency is not as high as that of the original rankine cycle operated between the same high and low pressure limits. The rankine cycle is a model used to predict the performance of steam turbine systems.
The rankine cycle is the ideal cycle for vapor power plants. The temperatures at the inlet of both turbines, and the thermal efficiency of the cycle are to be determined. The mass flow rate of steam entering the turbine is 1. The topping cycle is a gasturbine cycle and the bottoming cycle is a nonideal reheat rankine cycle. The simplecycle efficiencies of early gas turbines were practically doubled by incorporating intercooling, regeneration or recuperation, and reheating. Consider an ideal steam reheat cycle where steam enters the highpressure turbine at 3.
For the case presented in our reheat example they are both nearly identical at 40%. Consider an ideal reheatregenerative rankine cycle. R eheat rankine cycle is essentially a modification of simple rankine cycle. Concept of regenerative rankine cycle with feedwater heater will provide better positive result in respect of increase in thermal efficiency of the rankine cycle or in simple way we can say that thermal efficiency of the steam power cycle will be improved quite good by using the concept of regenerative rankine cycle with feedwater heater as compared with reheat cycle. Compared to the brayton cycle which uses adiabatic compression and expansion, an ideal ericsson cycle consists of isothermal compression and expansion processes, combined with isobaric heat regeneration between them.
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