scholarly journals On the Role of Nanofluids in Thermal-hydraulic Performance of Heat Exchangers—A Review

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 734 ◽  
Author(s):  
Salah Almurtaji ◽  
Naser Ali ◽  
Joao A. Teixeira ◽  
Abdulmajid Addali
Keyword(s):  
Heat Exchangers ◽  
Gas Turbines ◽  
Power Plants ◽  
Hydraulic Performance ◽  
Domestic Water ◽  
Operational Conditions ◽  
Oil Refineries ◽  
Land Vehicles ◽  
Different Temperatures

Heat exchangers are key components in many of the devices seen in our everyday life. They are employed in many applications such as land vehicles, power plants, marine gas turbines, oil refineries, air-conditioning, and domestic water heating. Their operating mechanism depends on providing a flow of thermal energy between two or more mediums of different temperatures. The thermo-economics considerations of such devices have set the need for developing this equipment further, which is very challenging when taking into account the complexity of the operational conditions and expansion limitation of the technology. For such reasons, this work provides a systematic review of the state-of-the-art heat exchanger technology and the progress towards using nanofluids for enhancing their thermal-hydraulic performance. Firstly, the general operational theory of heat exchangers is presented. Then, an in-depth focus on different types of heat exchangers, plate-frame and plate-fin heat exchangers, is presented. Moreover, an introduction to nanofluids developments, thermophysical properties, and their influence on the thermal-hydraulic performance of heat exchangers are also discussed. Thus, the primary purpose of this work is not only to describe the previously published literature, but also to emphasize the important role of nanofluids and how this category of advanced fluids can significantly increase the thermal efficiency of heat exchangers for possible future applications.

scholarly journals Recent Advances in Ammonia Combustion Technology in Thermal Power Generation System for Carbon Emission Reduction

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5604
Author(s):  
Hookyung Lee ◽  
Minjung Lee
Keyword(s):  
Power Generation ◽  
Gas Turbines ◽  
Power Plants ◽  
Thermal Power ◽  
Hydrogen Energy ◽  
Application Range ◽  
Combustion Technology ◽  
Power Generation System ◽  
Power Generation Systems

With the formation of an international carbon-neutral framework, interest in reducing greenhouse gas emissions is increasing. Ammonia is a carbon-free fuel that can be directly combusted with the role of an effective hydrogen energy carrier, and its application range is expanding. In particular, as research results applied to power generation systems such as gas turbines and coal-fired power plants have been reported, the technology to use them is gradually being advanced. In the present study, starting with a fundamental combustion research case conducted to use ammonia as a fuel, the application research case for gas turbines and coal-fired power plants was analyzed. Finally, we report the results of the ammonia-air burning flame and pulverized coal-ammonia-air co-fired research conducted at the authors’ research institute.

Selection of Gas Turbine With Minimum Flue Gas Emission

2007 ◽  
Author(s):  
P. Esna Ashari ◽  
V. Nayyeri ◽  
K. Sarabchee
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Fossil Fuels ◽  
Pressure Ratio ◽  
Inlet Temperature ◽  
Effective Parameters ◽  
Combustion Chambers ◽  
Optimum Pressure ◽  
Oil Refineries

Many factories in industry such as petrochemical plants, oil refineries and power plants need heat and power to support their process. This demand can be provided by a combined heat and power cycle (CHP) in the factory site. Some factories use gas turbine cycle to provide heat and power. Emissions from gas turbines, produced by burning fossil fuels in the combustion chambers, have important effects on air pollution. This is a significant problem in many developed and developing countries. Parameters such as inlet temperature and pressure ratio are the most effective parameters in gas turbine emission. By selecting an appropriate gas turbine, emission could be reduced to some extent. Further studies indicate that there is an optimum pressure ratio, which minimizes emissions.

The Efficiency of Closed-Cycle Gas Turbines Controlled by Different Methods and Programs

2020 ◽  
pp. 51-63
Author(s):  
V.D. Molyakov ◽  
B.A. Kunikeev ◽  
N.I. Troitskiy
Keyword(s):  
Gas Turbine ◽  
Heat Exchangers ◽  
Gas Turbines ◽  
Power Plants ◽  
Control Method ◽  
Low Pressure ◽  
Working Fluid ◽  
Closed Cycle ◽  
Efficient Operation ◽  
Pressure Compressor

Closed-cycle gas turbine units can be used as power plants for advanced nuclear power stations, spacecraft, ground, surface and underwater vehicles. The purpose and power capacity of closed gas turbine units (CGTU) determine their specific design schemes, taking into account efficient operation of the units both in the nominal (design) mode and in partial power modes. Control methods of both closed and open gas turbine units depend on the scheme and design of the installation but the former differ from the latter mainly in their ability to change gas pressure at the entrance to the low-pressure compressor. This pressure can be changed by controlling the mass circulating in the CGTU circuit, adding or releasing part of the working fluid from the closed system as well as by internal bypassing of the working fluid. At a constant circulating mass in the single-shaft CGTU, the temperature of the gas before the turbines and the shaft speed can be adjusted depending on the type of load. The rotational speed of the turbine shaft, blocked with the compressor, can be adjusted in specific ways, such as changing the cross sections of the flow of the impellers. At a constant mass of the working fluid, the pressure at the entrance to the low-pressure compressor varies depending on the control program. The efficiency of the CGTU in partial power modes depends on the installation scheme, control method and program. The most economical control method is changing the pressure in the circuit. Extraction of the working fluid into special receivers while maintaining the same temperature in all sections of the unit leads to a proportional decrease in the density of the working fluid in all sections and the preservation of gas-dynamic similarity in the nodes (compressors, turbines and pipelines). Specific heat flux rates, and therefore, temperatures change slightly in heat exchangers. As the density decreases, heat fluxes change, as the heat transfer coefficient decreases more slowly than the density of the working fluid. With a decrease in power, this leads to a slight increase in the degree of regeneration and cooling in the heat exchangers. The underestimation of these phenomena in the calculations can be compensated by the underestimation of the growth of losses in partial power modes.

scholarly journals Investigating the hydraulic resistance in the flow part elements of pneumatic systems and heat exchangers

2021 ◽  
Vol 2057 (1) ◽  
pp. 012015
Author(s):  
A S Pugachuk ◽  
N F Fominykh ◽  
E O Kalashnikova ◽  
Yu A Gavrilova
Keyword(s):  
Hydraulic Resistance ◽  
Heat Exchangers ◽  
Power Plants ◽  
Selective Laser Sintering ◽  
Additive Technologies ◽  
Distributed Power Generation ◽  
Coefficient Of Hydraulic Resistance ◽  
Flow Part ◽  
Shell And Tube

Abstract The article deals with the development of shell-and-tube heat exchangers for the needs of power engineering, based on additive technologies, in particular, selective laser sintering technology with new configurations of heat exchange surfaces. The role of heat exchangers in microturbines, the most common units of power plants of small distributed power generation, is considered. To intensify heat transfer and increase the efficiency of microturbines, it is proposed to use various configurations of flow channels of shell-and-tube heat exchangers made on the basis of additive technologies. Mathematical modeling and experimental study of a gas medium flow in the tubes of a heat exchanger are carried out. The dependences of the coefficient of hydraulic resistance between the surface of inlet and outlet of gas from tubes of various configurations on the Reynolds number are obtained. The results of the experiment allow us to conclude that the resistance of spiral-shaped tubes is slightly higher than the resistance of tubes with three ribs.

scholarly journals Study on Thermal Behavior of Flat Plate Heat Exchanger

2020 ◽  
Vol 6 (7) ◽  
pp. 3235
Author(s):  
Nitesh Kumar Singh ◽  
N. V. Saxena
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Air Conditioning ◽  
Power Plants ◽  
Industrial Applications ◽  
Plate Heat Exchanger ◽  
Chemical Plants ◽  
Oil Refineries ◽  
Gas Processing ◽  
Cooling Air

The plate Fin-and-tube heat exchangers are one of the most common types of heat exchangers used in various industrial applications such as heating, cooling, air conditioning, power plants, chemical plants, petrochemical plants, oil refineries, natural gas processing, industry aerospace, and wastewater treatment. It is very important to reduce the size and weight and improve the heat transfer rate of the heat exchanger. Finned and tubular heat exchangers with different geometries and orientations are used to improve thermal performance. This paper presents the Plate fin heat exchanger and types of Plate Fin Heat Exchanger Surfaces.

scholarly journals Thermo-Hydraulic Performance Evaluation of Shell & Tube Heat Exchanger with Different Tube Geometries

2019 ◽  
Vol 9 (1) ◽  
pp. 2125-2132
Keyword(s):  
Heat Exchanger ◽  
Cross Sections ◽  
Heat Exchangers ◽  
Power Plants ◽  
Waste Heat ◽  
Flow Behavior ◽  
Hydraulic Performance ◽  
Fluid Stream ◽  
Ansys Fluent ◽  
Tube Heat Exchanger

A heat exchanger is equipment that transfers heat energy from one fluid stream to another fluid stream across a solid surface by conduction and convection. Heat exchangers are used in air conditioning & refrigeration systems, power plants, automotive industries, chemical processing, waste heat recovery systems, and food industries. Shell & tube heat exchangers are the most widely used heat exchanger. Earlier many types of studies were carried out on baffle of heat exchanger, as the hydraulic performance of shell side of exchanger relies on baffle elements such as changing baffle types, baffle segments, baffle angles, baffle cuts, etc. are introduced. But only a few researches are concentrated on the tube side. In this paper, efforts have been made to design a shell & tube heat exchanger by using the kern method & referring TEMA standards. Also, the fluid flow behavior & heat transfer mechanism of shell & tube heat exchanger with four different cross-sections of the tubes i.e. Circular, Rectangular, Square & Triangular is numerically investigated using ANSYS-fluent. Numerical simulation was carried out for a single tube pass shell & tube heat exchanger with 25% baffle cut. Finally, from the simulation results, suggestions are made for the best geometry which gives the best thermo-hydraulic performance

The Key Role of Heat Exchangers in Closed Brayton Cycle Gas Turbine Power Plants

1996 ◽  
Author(s):  
Colin F. McDonald
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Gas Turbines ◽  
Power Plants ◽  
External Source ◽  
Plant Performance ◽  
Brayton Cycle ◽  
Intermediate Heat Exchanger ◽  
Enhance Efficiency

In the power generation field, simple cycle gas turbines are dominant, with heat exchanged variants only selected based on particular user’s requirements. For the lesser known closed Brayton cycle (CBC) power plant, heat exchangers are mandatory. The following three categories of heat exchangers are addressed in this paper, 1) heat input to the closed cycle from an external source; for example the heat exchanger in a fluidized bed combuster in the case of a fossil-fired plant, or an intermediate heat exchanger (IHX) in the case of an indirect cycle nuclear gas turbine, 2) recuperator in the system to enhance efficiency, and 3) exchangers (i.e., precooler and intercooler) for heat rejection from the system. The influence that these heat exchangers have on the selection of system parameters, and plant performance is discussed. Heat exchanger technology state-of-the-art for CBC systems is highlighted.

Are Advanced Large Gas Turbine Ready for Use in Captive Applications?

2008 ◽  
Author(s):  
Justin Zachary
Keyword(s):  
Gas Turbines ◽  
High Performance ◽  
Power Plants ◽  
Combined Cycle ◽  
Process Conditions ◽  
Industrial Facilities ◽  
Oil Refineries ◽  
Steam Extraction ◽  
Plant Optimization ◽  
High Level

Industrial facilities are applications where the majority of electricity and steam productions are devoted to internal consumption rather than being exported. Oil refineries, smelters, and chemical and desalinization plants are typical examples. In the case of aluminum smelters, the vast quantities of electricity required by the process cannot be supplied by utilities from the grid and therefore cogeneration is required. Since power and/or steam supply interruptions might have catastrophic effects on the facility processes, the paramount requirement for “dedicated power plants’ is availability and reliability rather than high performance. It is common to find older D and E gas turbines used as the prime mover. In recent years, however, advanced gas turbines (GTs) successfully demonstrated close to 60% efficiency in combined cycle applications. The G and H technology classes, using steam to perform GT cooling duty, accumulated thousands of operating hours. Many improvements from G and H were also implemented into FX Class (latest variants of the air-cooled F technology class). Firstly, the paper addresses the strategies for incorporation of advanced GTs in captive applications where the equipment must cope with rapid changes in power demand, such as load swings, load rejection, harmonic currents, etc. Further, it examines a variety of designs, where there is a high and low process steam demand for process. The discussion encompasses plant optimization aiming at a high level of redundancy: multi-shaft arrangements, common steam headers, and heavy supplementary firing. The selection of an optimum steam turbine (ST) is also discussed, including steam extraction locations and the ability to operate efficiently with steam extraction on and off. Issues dealing with steam purity requirements and water treatment sizing will also be addressed. Since the amount and quality of the condensate return vary substantially, maintaining the water chemistry is essential. In continuation, the article will describe the challenges for the control system design and in particular, the requirements to maintain tight process conditions during transients. Finally, the paper will present the experience of an engineering, procurement, and construction (EPC) contractor for several “captive applications” projects.

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