This document discusses the reheat cycle in thermodynamics. The reheat cycle is a modification of the Rankine cycle that is used in steam power plants. It works by reheating the steam after it expands in the high-pressure turbine and before it expands further in the low-pressure turbine. This increases the efficiency by raising the mean temperature of heat addition and reducing moisture content in the steam. Reheating allows for higher turbine work extraction and thermal efficiency compared to the basic Rankine cycle. The document examines the working of reheat cycles in steam turbines and thermal power plants, and their advantages in improving efficiency and reducing blade erosion.
PPT describes the engine performance parameters of the I.C. engine.
Engine performance is an indication of the degree of success of the engine performs its assigned task, i.e. the conversion of the chemical energy contained in the fuel into the useful mechanical work. The engine performance is indicated by the term efficiency, η. Five important engine efficiencies and other related engine performance parameters are:
Power
Indicated Thermal Efficiency (ηith)
Brake Thermal Efficiency (ηbth)
Mechanical Efficiency (ηm)
Volumetric Efficiency (ηv)
Relative Efficiency or Efficiency Ratio (ηrel)
Mean Effective Pressure (Pm)
Specific Fuel Consumption (sfc)
Fuel-Air or Air-Fuel Ratio (F/A or A/F)
Calorific Value (CV)
Power:-
The main purpose of running an engine is to obtain mechanical power.
Brake Power (B.P.)
The power developed by an Engine at the output shaft is called the brake power.
Brake Power= Brake Workdone/Time
B.P.=BWD/sec.
Indicated power (I.P.)
The total power developed by Combustion of fuel in the combustion chamber is called indicated power.
Indicated Power= Indicated Workdone/Time
I.P.=IWD/sec.
Frictional Power (F.P.)
The difference between I.P. and B.P. is called frictional power (f.p.).
FP = IP – BP
Thermal Efficiency (ηth)
Thermal efficiency is the ratio of Power to energy supplied by the fuel.
ηth= Power/ Energy
In I.C. Engine, thermal efficiency can be classified into two categories i.e.
Indicated Thermal Efficiency (ηith)
Indicated thermal efficiency is the ratio of indicated power to the heat supplied or added.
ηith= IP/Qs
2. Brake Thermal Efficiency (ηith)
Brake Thermal Efficiency is the ratio of brake power to the heat supplied or added.
ηbth= BP/Qs
Volumetric Efficiency (ηv)
This is one of the most important parameters which decide the performance of four-stroke engines. Four stoke engines have distinct suction stoke, volumetric efficiency indicates the breathing ability of the engine.
Volumetric efficiency is defined as the ratio of actual flow rate of air into the intake system to rate at which the volume is displaced by the system.
ηv= (푚 ̇"a/a" )/(푉푑푖푠푝푎푐푒푑 푋 푁/2)
"a"= Inlet density is taken atmospheric air density
N= Number of the cylinder in use
A steam turbine is a prime mover in which the potential energy of the steam is transformed into kinetic energy and later in its turn is transformed into the mechanical energy of rotation of the turbine shaft
PPT describes the engine performance parameters of the I.C. engine.
Engine performance is an indication of the degree of success of the engine performs its assigned task, i.e. the conversion of the chemical energy contained in the fuel into the useful mechanical work. The engine performance is indicated by the term efficiency, η. Five important engine efficiencies and other related engine performance parameters are:
Power
Indicated Thermal Efficiency (ηith)
Brake Thermal Efficiency (ηbth)
Mechanical Efficiency (ηm)
Volumetric Efficiency (ηv)
Relative Efficiency or Efficiency Ratio (ηrel)
Mean Effective Pressure (Pm)
Specific Fuel Consumption (sfc)
Fuel-Air or Air-Fuel Ratio (F/A or A/F)
Calorific Value (CV)
Power:-
The main purpose of running an engine is to obtain mechanical power.
Brake Power (B.P.)
The power developed by an Engine at the output shaft is called the brake power.
Brake Power= Brake Workdone/Time
B.P.=BWD/sec.
Indicated power (I.P.)
The total power developed by Combustion of fuel in the combustion chamber is called indicated power.
Indicated Power= Indicated Workdone/Time
I.P.=IWD/sec.
Frictional Power (F.P.)
The difference between I.P. and B.P. is called frictional power (f.p.).
FP = IP – BP
Thermal Efficiency (ηth)
Thermal efficiency is the ratio of Power to energy supplied by the fuel.
ηth= Power/ Energy
In I.C. Engine, thermal efficiency can be classified into two categories i.e.
Indicated Thermal Efficiency (ηith)
Indicated thermal efficiency is the ratio of indicated power to the heat supplied or added.
ηith= IP/Qs
2. Brake Thermal Efficiency (ηith)
Brake Thermal Efficiency is the ratio of brake power to the heat supplied or added.
ηbth= BP/Qs
Volumetric Efficiency (ηv)
This is one of the most important parameters which decide the performance of four-stroke engines. Four stoke engines have distinct suction stoke, volumetric efficiency indicates the breathing ability of the engine.
Volumetric efficiency is defined as the ratio of actual flow rate of air into the intake system to rate at which the volume is displaced by the system.
ηv= (푚 ̇"a/a" )/(푉푑푖푠푝푎푐푒푑 푋 푁/2)
"a"= Inlet density is taken atmospheric air density
N= Number of the cylinder in use
A steam turbine is a prime mover in which the potential energy of the steam is transformed into kinetic energy and later in its turn is transformed into the mechanical energy of rotation of the turbine shaft
Need for cooling of an aircraft. types of air-refrigeration system, DART, Advantages of air refrigeration system, Open and closed cycle air refrigeration,
Need for cooling of an aircraft. types of air-refrigeration system, DART, Advantages of air refrigeration system, Open and closed cycle air refrigeration,
Thermodynamic Cycles for Power Generation—Brief Review
Real Steam Power Plants—General Considerations
Steam-Turbine Internal Efficiency and Expansion Lines
Closed Feed water Heaters (Surface Heaters)
The Steam Turbine
Turbine-Cycle Heat Balance and Heat and Mass Balance Diagrams
Steam-Turbine Power Plant System Performance Analysis Considerations
Second-Law Analysis of Steam-Turbine Power Plants
Gas-Turbine Power Plant Systems
Combined-Cycle Power Plant Systems
Now a day’s power generation is most important for
every country. This power is generated by some thermal
cycles. But single cycle cannot be attain complete power
requirements and its efficiency also very low so that to fulfill
this requirements to combine two or more cycles in a single
power plant then we can increase the efficiency of the power
plant. Its increased efficiency is more than that of if the plant
operated on single cycle. In which we are using two different
cycles and these two cycles are operated by means of different
working mediums. These type of power plants we can called
them like combined cycle power plants. In combined cycle
power plants above cycle is known as topping cycle and below
cycle is known as bottoming cycle. The above cycle generally
brayton cycle which uses air as a working medium. When the
power generation was completed the exhaust gas will passes
in to the waste heat recovery boiler. Another cycle also
involved in bottoming cycle. This cycle works on the basis on
rankine cycle. In which steam is used as working medium.
The main component in bottoming cycle is waste heat
recovery boiler. It will receive exhaust heat from the gas
turbine and converts water in to steam. The steam used for
generating power by expansion on steam turbine. Combined
cycle power plants are mostly used in commercial power
plants.
In this paper we are analyzing one practical
combined cycle power plant. In practical conditions due to
some losses it can not be generates complete power. So that
we are invistigated why it is not give that much of power and
the effect of various operating parameters such as maximum
temperature and pressure of rankine cycle, gas turbine inlet
temperature and pressure ratio of Brayton cycle on the net
output work and thermal efficiency of the combine cycle
power plant.
The outcome of this work can be utilized in order to
facilitate the design of a combined cycle with higher efficiency
and output work. Mathematical calculations and simple
graphs in ms excel, and auto cad has been carried out to
study the effects and influences of the above mentioned
parameters on the efficiency and work output.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
HIL Report on Refrigeration unit & BoilersAkansha Jha
Study of refrigeration unit & boilers. It involved the calculation of safe chimney height required to dispose the smoke out into atmosphere without polluting the land and the estimation of fuel amount required for an oil fired boiler per day in HIL, Rasayani.
FellowBuddy.com is an innovative platform that brings students together to share notes, exam papers, study guides, project reports and presentation for upcoming exams.
We connect Students who have an understanding of course material with Students who need help.
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Our Vision & Mission – Simplifying Students Life
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Like Us - https://www.facebook.com/FellowBuddycom
FellowBuddy.com is an innovative platform that brings students together to share notes, exam papers, study guides, project reports and presentation for upcoming exams.
We connect Students who have an understanding of course material with Students who need help.
Benefits:-
# Students can catch up on notes they missed because of an absence.
# Underachievers can find peer developed notes that break down lecture and study material in a way that they can understand
# Students can earn better grades, save time and study effectively
Our Vision & Mission – Simplifying Students Life
Our Belief – “The great breakthrough in your life comes when you realize it, that you can learn anything you need to learn; to accomplish any goal that you have set for yourself. This means there are no limits on what you can be, have or do.”
Like Us - https://www.facebook.com/FellowBuddycom
Industrial heat pumps, using waste process heat as the source, deliver heat at a higher temperature for use in industrial process heating, preheating, or space heating. There is debate over their definition, but, in general, they represent a worthwhile method of improving the energy efficiency of industrial processes and reducing primary energy consumption.
Industrial heat pumps (IHPs) offer various opportunities in all types of manufacturing processes and operations. Increased energy efficiency is certainly their most obvious benefit, but few companies have realised the untapped potential of IHPs in solving production and environmental problems. This Application Note demonstrates that IHPs can offer the least-cost option for removing bottlenecks in production processes and allowing greater product throughput and, in fact, may be an industrial facility’s best way of significantly and cost-effectively reducing combustion-related emissions.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
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6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
CW RADAR, FMCW RADAR, FMCW ALTIMETER, AND THEIR PARAMETERSveerababupersonal22
It consists of cw radar and fmcw radar ,range measurement,if amplifier and fmcw altimeterThe CW radar operates using continuous wave transmission, while the FMCW radar employs frequency-modulated continuous wave technology. Range measurement is a crucial aspect of radar systems, providing information about the distance to a target. The IF amplifier plays a key role in signal processing, amplifying intermediate frequency signals for further analysis. The FMCW altimeter utilizes frequency-modulated continuous wave technology to accurately measure altitude above a reference point.
1. Koya University
Faculty of Engineering
Chemical Engineering Department – 2nd stage
Instructor
Mr. Ahmed A. Maaroof
Prepared by
Safeen Yaseen Jafar
Submitted Date
8 Dec 2020
Thermodynamics
The Reheat Cycle
2. Table of Content
1. Abstract..................................................................................................................... 1
2. Introduction................................................................................................................ 2
3. Body........................................................................................................................... 3-9
3.1. What is the Reheat Cycle in Thermodynamics........................................................ 3
3.2. Reheat Cycle’s Method to Increase the Efficiency of The Rankine Cycle............. 4
3.3. The Use of Reheat Cycle in Steam Turbines......................................................... 5-6
3.4. Why We Use Reheat................................................................................................ 6-9
4. Conclution......................................................................................................................... 10
5. Reference............................................................................................................................ 11
3. 1
Abstract
We know that nowadays the Power is the most energy which we used in our life for everyday and
many of things. Development in this type of energy is important and we need to use best and safe method to
convert a varies of energy to power like solar, mechanical heat...etc. So, in this essay we talking about the
one of power production method by the cycle of thermodynamic process that called as The Reheat Cycle. Its
mean that The Reheat Cycle is the cycle of conversion of the heat energy to Work or Power by increase the
work turbines in this cycle. In basic Rankine cycle, after the isentropic development in turbine, steam is
specifically fed into condenser for condensation process. There are two turbines in the reheat system which is
utilized for enhancing effectiveness. Steam, after extension from high pressure turbine, is sent again to boiler
and heated till it comes to superheated condition. It is then left to extend in low pressure turbine to
accomplish condenser pressure.
4. 2
Introduction
In thermodynamics we have the important subject or we can say by other word the reheat cycle is the
subject which related to thermodynamics. Generally, the reheat cycle is the reversible cycle (Carnot cycle)
and one type of Rankine cycle is the (Rankine cycle with reheat/reheating cycle). this cycle exits in steam
power plant and its purpose to convert the energy (especially heat energy) to power or work.
Today, most of the electricity produced throughout the world is from steam power plants. However,
electricity is being produced by some other power generation sources such as hydropower, gas power, bio-
gas power, solar cells, etc. One newly developed method of electricity generation is the Magneto hydro
dynamic power plant. This paper deals with steam cycles used in power plants. Thermodynamic analysis of
the Rankine cycle has been undertaken to enhance the efficiency and reliability of steam power plants. The
thermodynamic deviations resulting in non-ideal or irreversible functioning of various steam power plant
components have been identified. A comparative study between the Carnot cycle and Rankine cycle
efficiency has been analyzed resulting in the introduction of regeneration in the Rankine cycle. Factors
affecting efficiency of the Rankine cycle have been identified and analyzed for improved working of thermal
power plants. (Kapooria, R K; Kumar, S And Kasana, K S., 2008)
Basic steam power plants operate based on Rankine cycle (with reheating) and can be employed where both
electricity and heat are required. Many techniques are being used to increase the efficiency of the steam
cycle. Most outstanding of these techniques are reheating and/or reducing the irreversibilities. Reheating
increases the efficiency by raising the mean temperature of the heat addition process, by increasing the steam
temperature at the turbine inlet and also by increasing the efficiency of the expansion process in the steam
turbine.1 The irreversibility of the steam generator can be decreased by raising the steam temperature at the
turbine inlet. Another technique to improve the efficiency is to enhance the quality of steam at the condenser
inlet. (G Gonca &H K Kayadelen 2016)
Reheating is a method of improving Rankine cycle efficiency which consists of inter-stage heating of
the expanding steam. After the first stage of expansion which typically reduces initial steam pressure by one-
fourth, the steam is heated up (or close) to the maximum heat source temperature. After the second
expansion stage the steam reaches condensation pressure. Although more heat input is required for reheating,
the efficiency of a reheating cycle is higher because the two-stage turbine develops relatively more work.
(Ibrahim Dincer, C. Z., 2014)
5. 3
Figure (1) This figure shows us the Reheat cycle and T-S Diagram.
What is the Reheat Cycle in Thermodynamics
A process in which the gas or steam is reheated after a partial isentropic expansion to reduce moisture
content. Also known as resuperheating.
Figure (2) in this figure we can see The Reheat Cycle process diagram.
6. 4
Reheat Cycle’s Method to Increase the Efficiency of The Rankine Cycle
As we see above in the process diagram of reheat cycle. Increase the average temperature at which heat is
transferred to the working fluid in the boiler, or decrease the average temperature at which heat is rejected
from the working fluid in the condenser. (Bajpai, P., 2020) In shorter we can focus on these points below:
1. Lowering the condenser Pressure
Lowering the operating pressure of the condenser lowers the temperature at which heat is rejected. The
overall effect of lowering the condenser pressure is an increase in the thermal efficiency of the cycle.
(Bajpai, P., 2020)
2. Superheating the steam to high temperatures
The average temperature at which heat is added to the steam can be increased without increasing the boiler
pressure by superheating the steam to high temperatures. Superheating the steam to higher temperatures has
another very desirable effect: It decreases the moisture content of the steam at the turbine exit. (Bajpai, P.,
2020)
3. Increasing the Boiler pressure
Increasing the operating pressure of the boiler, automatically raises the temperature at which boiling takes
place. This raises the average temperature at which heat is added to the steam and thus raises the thermal
efficiency of the cycle. (Bajpai, P., 2020)
7. 5
The Use of Reheat Cycle in Steam Turbines
The fundamentals of steam power plant to generate the power by steam is the reheating cycle as we
see and talk about their info as long. So, the reheat cycle increases the turbine work and consequently the
total work of the cycle. This is accomplished not by changing the compressor work or the turbine inlet
temperature but instead by dividing the turbine expansion into two or more parts with constant pressure
heating before each expansion. This cycle modification, as shown in Figure (1) below, is known as reheating.
By reasoning similar to that used in connection with intercooling, it can be seen that the thermal efficiency of
a simple cycle is lowered by the addition of reheating, whereas the work output is increased. However, a
combination of regenerator and reheater can increase the thermal efficiency. (Boyce, 2012)
The purpose of the Reheat Cycle Reheat cycle is worked with Rankine cycle to remove the moisture
from the steam. We use the reheating method is to avoid excess moisture which is carried by the steam at
final stages of expansion process in a turbine. The blades of the turbine erode due to excessive moisture. The
efficiency of steam turbine can be improved by decreasing condenser pressure, increasing boiler pressure or
by using the reheat cycle and regenerative cycle. In a reheat cycle, the vapor is expanded in multiple stages
in different turbines. After the first stage of expansion, the vapor is at the super-heated state(state 1 in the fig)
or dry saturated state (To avoid excess moisture). After every stage of expansion, the vapor is sent to the
boiler where it is reheated, followed by expansion in the turbine of next stage and is finally condensed in a
condenser. (Wiki, 2020)
Figure (3) this figure understand us the cycle of steam power plant and it show us the cycle of reheating.
8. 6
Figure (4) in this figure we see the steam turbine (reheat turbine) STF-D650 is GE’s highest-
performing combined-cycle steam turbine and delivers the reliability and availability needed in today’s
demanding energy environment.
Why We Use Reheat
Consider the Rankine Cycle shown in Figure 1. While at first glance this appears to be an attractive
cycle (a thermal efficiency of 40% is quite good), it has two problems considered as a practical device. First,
the pressure ratio assumed across the turbine is unrealistically high (about 1000). Second, the steam coming
out of the turbine (at S3) is over 20% wet, which may damage a real turbine. We could address the pressure
ratio problem by splitting the turbine into two sequential turbines, each with a PR of about 32. The low
quality of the steam at the turbine outlet is a more interesting problem, and one that can occur in many vapor
powers cycles. When the steam at the outlet of a turbine becomes wet, the liquid present is in the form of
water droplets. If the steam is not very wet, the amount of water is small and the droplets are not too
troublesome to the operation of the turbine. This is because the liquid drops are formed by condensation
from the steam to form a kind of fog. Like atmospheric fog, this fog contains extremely small drops and the
drops move with almost the same velocity as the surrounding steam.
However, as the quality of the steam decreases, the concentration of these water droplets increases.
The turbine blades move rapidly through the steam and tend to collect the water droplets. This is because the
denser water droplets do not move with quite the same velocity as the steam, and so get "scooped up" by the
blade. Once on the blade, the water forms a film and runs to the back of the blade. Here the water is re-
entrained into the steam. But this droplet formation method is completely different to the original one. The
droplets are a completely different size: they are much larger and now no longer follow the steam flow.
When these large drops impact with the turbine blades they can do much damage and certainly impair the
efficiency of the turbine. It is often considered unwise to allow steam with qualities of less than around 85%
to 90% to remain in the turbine. (Peter B. Whalley, Kenneth D. Forbus, M. E. Brokowski., 1997)
9. 7
Thermodynamic Analysis of Reheat Cycle Steam Power Plants
A thermodynamic analysis of a Rankine cycle reheat steam power plant is conducted, in terms of the
first law of thermodynamic analysis (i.e. energy analysis) and the second law analysis (i.e. exergy analysis),
using a spreadsheet calculation technique. The energy and exergy efficiencies are studied as 120 cases for
different system parameters such as boiler temperature, boiler pressure, mass fraction ratio and work output.
The temperature and pressure values are selected in the range between 400 and 590°C, and 10 and 15 MPa,
being consistent with the actual values. The calculated energy and exergy efficiencies are compared with the
actual data and the literature work, and good agreement is found. The possibilities to further improve the
plant efficiency and hence reduce the inefficiencies are identified and exploited. The results show how
exergy analysis can help to make optimum design decisions in a logical manner. (John Wiley & Sons, 2001)
Figure (5) If we see the figure above we can see Steam Power Plant, Reheat Cycle process and their
connection in the plant.
10. 8
Reheat Cycle in Thermal Power Plant
The efficiency of the Reheat Cycle can be improved by increasing the pressure and temperature of the
steam entering into the turbine. As the initial pressure increases, the expansion ratio of the turbine also
increases and the steam becomes quite wet at the end of expansion. This is not desirable as increase
in moisture content of the steam causes corrosion of the turbine blades and increases the losses. This reduces
the nozzle and blade efficiency. In the reheat cycle, the steam is extracted from the suitable point in the turbine
and is reheated with the help of the flue gases in the boiler furnace. The main purpose of reheating is to increase
the dryness of the steam passing through the lower stages of the turbine. The dryness fraction coming out of
turbine should not be less than 0.88. The increase in the thermal efficiency due to the reheat depends upon the
ratio of the reheat pressure to original pressure of the steam. The reheat pressure is generally kept within 20%
of the initial pressure of the steam. The efficiency of the reheat cycle may be less than the Rankine efficiency
if the reheat is used at low pressure. (Sostenes, 2015)
Advantages:
1. The reheating reduces 4 to 5% fuel consumption with a corresponding reduction in the fuel handling
2. The reheat cycle reduces the steam flow of 15 to 20% with corresponding reduction in the boiler,
turbine and feed handling equipment capacities. This also reduces the pumping power in that
proportion.
3. The wetness of the exhaust steam with the reheat cycle is reduced to 50% of the Rankine cycle with a
corresponding reduction in the exhaust blade erosion.
4. Lower steam pressures and temperatures and less costly materials can be used to obtain the required
thermal performance. (Sostenes, 2015)
Disadvantages:
1. The cost of the extra pipes, equipment and controls make the cycle more expensive than the normal
Rankine cycle.
2. The greater floor space is reduced to accommodate the longer turbine and reheat piping.
3. The complexity of the operation and control increases with the adoption of the reheat cycle in thermal
powerplant.
4. All the lighter loads, the steam passing through the last blade rows to the condenser are seriously
super-heated if the same reheat is maintained. Feed water is sometimes sprayed into the low-pressure
cylinders also steam flows as a precaution against over-heating of blades.
5. increases the size of condenser based on unit mass flow of steam due to improved quality of steam at
exhaust from L.P turbine. (Ijesrt Journal, 2015).
11. 9
Figure (6) Above Diagram show us Thermal Power Plant, Reheat Cycle process and their connection
in the plant.
Use of Reheat Cycle and Regenerative Cycle Together
We examine the performance of regenerative-reheat power plants in terms of irreversibility analysis.
The reduction in the irreversible losses with the addition of backward, cascade-type feedwater heaters and/or
a reheat option are compared with a conventional energy-balance approach. The results indicate that most of
the irreversible losses occur in the boiler and that these losses are significantly reduced by the incorporation
of feedwater heating. The incorporation of feedwater heating results in a reduction of the total irreversibility
rate of the cycle by 18%. The corresponding improvement in efficiency is 12%. These two figures are
augmented to 24 and 14%, respectively, by the incorporation of reheat in addition to regeneration. (Habib
and Zubair, 1992)
12. 10
Conclusion
As we talked about in this essay. The most thermodynamics cycles are useful and they are use in
many of thermodynamics processes, and plants. Also, they have a lot of advantages to increase efficiency of
somethings such as generation of energy like work or power. So, we focused on one of the cycle processes or
irreversible processes in thermodynamics like this cycle (Reheat Cycle). this cycle as we talked about before
has many of other points, advantages and uses in plants or our daily life. We can conclude our words in these
points below:
➢ Reheat cycle is one of the cycling processes in thermodynamics like all reversible processes in
thermodynamics.
➢ One of the Rankine Cycle types is Reheat Cycle.
➢ In reheating process, the efficient of generation of power usually is increased.
➢ The reheat cycle can be used in steam and thermal power plants as the process of thermodynamics.
13. 11
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