Experimental and computational fluid dynamic study of water flow and submerged depth effects on a tidal turbine performance

This study involves an experimental and numerical analysis of the Hunter turbine, a vertical axis turbine utilized for tidal energy. A laboratory model of the Hunter turbine, featuring an aspect ratio of 1.2, was designed and tested. Numerical equations, including the Reynolds-averaged Navier–Stokes (RANS) constant, were analyzed through computational fluid dynamics (CFD) software using the k- turbulence model to forecast turbine performance and other related flow specifications, such as pressure lines, stream velocity, and pressure. This simulation was conducted on the surface of the turbine blade, and the results were obtained accordingly. The experimental data were utilized to verify the numerical results, and the difference between the two was reasonably acceptable. The turbine was studied in six different flow coefficients and four different vertical positions. The results indicated that the power coefficient increased as the submerged depth from a water-free surface increased, and after a specific depth, the output power remained constant. It was also observed that the minimum depth from a water-free surface for maximum power coefficient was three times the diameter of the turbine drum (3D)

Evaluation of mechanical vapor recompression and easy multi-effect desalination systems in different climate conditions-sensitivity and 7E analysis

Evaporative desalination systems, such as Multi-Effect Desalination (MED) and Mechanical Vapor Recompression (MVR), play important roles in addressing this challenge. Although large-scale desalination systems possess limitations in catering to the water demands of remote regions and islands and entail the cost of water transportation to residential areas, it is imperative to concentrate on studying the feasibility of employing centralized evaporative water production systems. Firstly, in this study, the initial focus is on conducting energy and exergy analyses of MVR and Easy MED systems, with a goal of enhancing knowledge about the energy consumption, exergy destruction and exergetic efficiency of these systems. Secondly, an economic analysis is undertaken to assess the feasibility of deploying these systems in various global regions. The analysis takes into account different geographical and techno-economic conditions, such as sea water temperature, interest rates, and electricity costs. This investigation also aims to explore variations in Annual Operative Cost (AOC), Total Annual Cost (TAC) and the cost of fresh water across these diverse regions. Thirdly, a sensitivity analysis is performed for the economic assessment of MVR and Easy MED systems. Lastly, exergoeconomic, environmental, enviroeconomic and exergoenvironmental analyses are conducted for both of these systems. The results show that the exergy efficiency of the Easy MED system surpasses that of the MVR, whereby the exergy destruction for Easy MED and MVR are recorded to be 5460 W and 6360 W respectiveyl. In addition to this, the MVR system demonstrated a higher TAC across all cities. The freshwater production cost of the Easy MED system was less expensive than of the MVR system. Perth was the most cost-effective city, with freshwater costs of 6.8 /m3 and 11.91 /m3 for MVR and Easy MED systems, respectively. Further to this, sensitivity analysis revealed that both systems are sensitive to fluctuations in electricity costs and seawater temperatures. The MVR system incurred higher fuel, product, and exergy destruction costs. However, the MVR system also exhibited greater environmental friendliness due to its lower emission of pollution gases

Development of a model efficiency improvement for the designing of feedwater heaters network in thermal power plants

Thermal power plants play a significant role in generating power, electricity, and energy consumption in the world, especially in developing countries. Therefore, the energy analysis of these power plants is very useful to increase the efficiency of systems and reduce energy consumption. One of the components of power plants that play a great role in energy consumption and recovery is the feedwater heater. In this study, a design method-based pinch technology for feedwater heaters of a coal power plant is presented. This method is used to reduce the irreversibility of heat transfer in feedwater heaters in this power plant. This study is performed on six feedwater heaters, which are similar in pairs. The results of this method show that this method is feasible for this system, and the results also show that the implementation of this method with a Pinch range of 10 °C indicated a deficit hot utility of about 48.54 MW. Also, the amount of power plant efficiency improvement is 12.12%, and according to the Pinch method, the energy price of the power plant can be reduced by about 125,489 $/year.https://asmedigitalcollection.asme.org/energyresourceshj2023Mechanical and Aeronautical Engineerin

Thermo-structural fatigue and lifetime analysis of a heat exchanger as a feedwater heater in power plant

Today, the use of shell and tube heat exchangers has become widespread and they are used in various industries under very diverse operating conditions. Specific operating conditions make it possible to consider and simulate the operating terms and failure conditions of these converters. In this study, the design of a shell-and-tube counter-flow heat exchanger in AutoCAD software is first considered, and the system is then meshed and simulated in ANSYS 2019 software. Simulation results of temperature, pressure, heat flux and fluid velocity within the system are reported in order to understand the system performance. Failure conditions are evaluated according to the ASME VIII Boiler and Pressure Vessel Code, and the results of equivalent thermal stress analysis and system lifetime under two extreme loading conditions are reported. The highest equivalent thermal stresses under these extreme load conditions occur at the joints of the tubes and tubes sheet and is equal to 641 and 931 MPa, respectively. Also, the lifetimes of tubes and tube sheets are 105 and 104 cycles respectively for the valley and peak load conditions.http://www.elsevier.com/locate/engfailanal2021-07-01hj2020Mechanical and Aeronautical Engineerin

Statistical and fractal analysis of nitrogen ion implanted tantalum thin films

Please read abstract in the article.https://link.springer.com/journal/3392021-06-03hj2020Mechanical and Aeronautical Engineerin

An artificial intelligence-based prediction way to describe flowing a Newtonian liquid/gas on a permeable flat surface

The purpose of this study is to utilize artificial neural network (ANN), as one of the most powerful artificial intelligence methods, for modeling stream function (f) and the dimensionless temperature (θ) for the considered problem. The problem that is investigated here is flowing a Newtonian fluid on a permeable flat surface. The Homotopy Perturbation Method (HPM) recently developed by the authors for this problem is utilized to provide enough number of the input data. The best ANN is found for each of the two indicated outputs. Then, the best ANN model for each output is utilized to investigate the impact of changing the similarity variable in the range 0.0 to 10.0 on prediction error of the two mentioned outputs. Four values for porosity, which are 0.2, 0.5, 0.8, and 1.0, are investigated. According to the findings, an almost quadratic relation for changes prediction error of f as a function of η is seen, whereas after a sudden drop, the error in prediction of θ declines linearly. Moreover, for the whole range, and for both outputs, the error remains in an acceptable range, which verifies the good accuracy of ANN.http://link.springer.com/journal/10973hj2022Mechanical and Aeronautical Engineerin

Numerical development of a coupled one-dimensional/three-dimensional computational fluid dynamics method for thermal analysis with flow maldistribution

This work describes the development of a methodology that couples one-dimensional (1D) network elements with three-dimensional spatial computational fluid dynamic (CFD) elements to analyze shell-and-tube heat exchangers with dense tube bundles. The 1D elements represent the tube flow while the spatial elements represent the external auxiliary flow. This reduces the computational expense significantly as compared to full computational fluid dynamics analysis of the same system, while a detailed transient temperature distribution can still be obtained. The methodology uses a unique combination of relaxation algorithms, a polynomial regression mapping procedure, and discretisation methods to create a coherent numerical methodology. Simulations are performed on a TEMA-FU-type shell-and-tube heat exchanger. The methodology was validated against full CFD and indicates errors between the calculated logarithmic mean temperature differences (LMTD) of less than 2% over a range of turbulent flow conditions. Various combinations of media for primary and auxiliary fluids are considered, to test the applicability and robustness of the methodology. Finally, a transient simulation of timed step inputs for the flowrate and temperature of both primary and auxiliary fluids also corresponds with a full CFD analysis. It is concluded that the proposed 1D-CFD method is effective for simplifying the analysis of flow-through tube bundles.The Eskom Power Plant Engineering Institute (EPPEI).https://asmedigitalcollection.asme.org/thermalscienceapplicationhj2022Mechanical and Aeronautical Engineerin

Modeling and exergy analysis of domestic MED desalination with brine tank

Desalination systems are taken into account as one of the promising solutions to deal with the water scarcity problem. Among different kinds of desalination systems, having the advantages like using low grade thermal resources, multi-effect type is getting popular more and more. Considering the mentioned issues, in this study, a high performance multi-effect desalination (MED) system is introduced and the enhancement potential of that is evaluated in details. The introduced and reference designs are compared together from different points of view. The results showed that not only the fresh water production of the introduced MED device is enhanced from the range of 12–16 to 14–21.6 L h–1 compared to the base case condition, but also gained output ratio increases up to 30%–40%. Moreover, the conducted exergy analysis shows that with the exergy efficiency of 82%, the brine tank has the highest performance among other components, while the exergy destruction for this part is negligible compared to the other parts. Therefore, a high level of improvement can be achieved using the introduced design.https://www.deswater.compm2020Mechanical and Aeronautical Engineerin

Exergoeconomic analysis and optimization of reverse osmosis desalination integrated with geothermal energy

In this research, the integrated carbon dioxide power cycle with the geothermal energy source to supply the required reverse osmosis desalination power for freshwater production is defined. The cycling power is consumed by the desalination system and sodium hypochlorite generator. Exergoeconomic analysis, and optimization are studied. Exergoeconomic analysis is shown that the desalination system, sodium hypochlorite generator, carbon dioxide turbine, and natural gas turbine have the highest rate for the sum of capital gain and exergy destruction cost. For the first case of optimization, the total cost rate is considered as the objective function. The optimal inlet discharge rate of sodium hypochlorite generator was 62% of the brine water outlet discharge rate of the desalination system. Plus, the total cost rate is reduced by 10% compared to the general case when 100% of brine water discharge rate of the desalination system enters into the sodium hypochlorite generator. The second case is multiobjective optimization to reduce costs and increase productivity.http://wileyonlinelibrary.com/journal/ep2021-01-14hj2020Mechanical and Aeronautical Engineerin