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exergy-destructions
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Optimization Model of Water-energy Nexus in the Cooling Towers
, M.Sc. Thesis Sharif University of Technology ; Avami, Akram (Supervisor)
Abstract
One of the best ways to reduce water consumption is using air cooled heat exchangers, because they work in a completely closed cycle which does not require makeup water. However because of their high surface area and high-technology production method, their production cost is significantly high. Air cooled heat exchangers have relatively high exergy destruction because of low U heat-transfer coefficient. In present research, single-objective and multiple objective optimization problems are developed to minimize total annual cost and exergy destruction. Also the influence of temperature changes on these two objective functions have been evaluated by Monte Carlo simulation. In next step,...
Feasibility and Supply an Optimal Integrated Model of the Energy and Exergy for Producing of Biogas and Ethanol from Solid Waste and wastewaters flows: in Tehran
, M.Sc. Thesis Sharif University of Technology ; Avami, Akram (Supervisor)
Abstract
In recent years, access to clean energy sources is the major instruments for sustainable development. Limitation of energy resources and the problems resulting from the use of fossil fuels was caused attention to biomass in different countries as a stable source of renewable energy. Organic waste in municipal solid waste and domestic wastewater are biomasses that can be used as a raw material used in the production of energy. Practical studies show that quality and quantity of municipal solid waste to produce biogas and bioethanol in Iran is very appropriate. In this process, the household solid waste and wastewater are in the anaerobic digestion reactors and fermentation systems without any...
Flexible Design of LNG Multi-Stream Heat Exchanger (Coldbox) with the Focus on Exergy Destruction and Part-load Operation
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor) ; Hosseini, Vahid (Supervisor)
Abstract
Natural gas liquefaction is a gas refrigeration technology, which enables the export of natural gas worldwide, in liquids formed and stored at very low temperatures. In this project, a plate-fin type of heat exchanger, which is used for liquefaction of natural gas (mainly methane) at very low temperatures, has been investigated. The most important and effective part of this gas refrigeration cycle is the cold box heat exchanger. The cold box consists of two or more floors in which some sorts of fins are installed in each floor. In this simulation, the three-sream heat exchanger is designed in such a way that the input temperature of the natural gas is about 200 K and the output is 145 K at a...
Exergy analysis of waste heat recovery section in steam-natural gas reforming process
, Article Energy and Fuels ; Volume 29, Issue 5 , April , 2015 , Pages 3322-3327 ; 08870624 (ISSN) ; Farhadi, F ; Sharif University of Technology
American Chemical Society
2015
Abstract
In this work, an exergy analysis is performed for the waste heat recovery section (WHRS) of the steam-natural gas reforming (SNGR) process as a major energy intensive process. Two alternate conditions are investigated to evaluate the required thermodynamic parameters: normal operating condition and increase of C2 + components in the process feed stream. At normal operating condition, the exergy efficiency of WHRS amounts to 0.58 while some 17.2 kJ energy is destructed for each mole of H2 produced. If heavier than methane components are increased in the feed up to 8.5 mole %, despite the increase of H2 production, the exergy efficiency decreases down to 0.54...
Multi objective optimization of an irreversible thermoelectric heat pump using evolutionary algorithms and response surface method
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; 2021 ; 15567036 (ISSN) ; Assareh, E ; Erfani, A ; Alirahmi, M ; Jafarinejad, T ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
In this study, modeling of an irreversible thermoelectric heat pump was conducted, and its performance was assessed in terms of exergy for 10, 20, 30 and 40 K difference in temperature (∆T) by changing the values of the design parameters. By employing this model, positive impact of increasing cross-section area, current and thermocouple’s length which in turn increases the exergy efficiency is realized. In addition, diminishing adverse impact of adding more thermocouples on the exergy efficiency of the system is illustrated. Afterward, exergoeconomic performance of the thermoelectric heat pump is evaluated. Then, exergoeconomic factor for each of the system’s components is diagnosed. The...
Thermo-economic-environmental multiobjective optimization of a gas turbine power plant with preheater using evolutionary algorithm
, Article International Journal of Energy Research ; Volume 35, Issue 5 , 2011 , Pages 389-403 ; 0363907X (ISSN) ; Ahmadi, P ; Ghaffarizadeh, A. R ; Saidi, M. H ; Sharif University of Technology
2011
Abstract
In this study, the gas turbine power plant with preheater is modeled and the simulation results are compared with one of the gas turbine power plants in Iran namely Yazd Gas Turbine. Moreover, multiobjective optimization has been performed to find the best design variables. The design parameters of the present study are selected as: air compressor pressure ratio (rAC), compressor isentropic efficiency (ηAC), gas turbine isentropic efficiency (ηGT), combustion chamber inlet temperature (T3) and gas turbine inlet temperature. In the optimization approach, the exergetic, economic and environmental aspects have been considered. In multiobjective optimization, the three objective functions,...
A Novel, eco-friendly combined solar cooling and heating system, powered by hybrid Photovoltaic thermal (PVT) collector for domestic application
, Article Energy Conversion and Management ; Volume 222 , 2020 ; Liravi, M ; Babaie Rabiee, M ; Ghodrat, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Solar heating and cooling technologies can have a vital role to play in understanding the targets in energy security, economic development, and mitigating climate change. This study aimed to investigate the performance of the combined solar cooling/heating system using a Photovoltaic Thermal collector (PVT) for residential applications. The main advantage of using PVT is the conversion of the maximum amount of solar energy into electricity and thermal energy. In this work, water is used to cool the panel and, consequently, increase the efficiency. The cooling cycle comprises a hybrid ejector-compression refrigeration cycle with two evaporator temperatures. To reduce the effect of the global...
A new pre-concentration scheme for brine treatment of MED-MVC desalination plants towards low-liquid discharge (LLD) with multiple self-superheating
, Article Energy ; Volume 225 , 2021 ; 03605442 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Multi-effect distillation units discard brine at high volume to the environment which results in numerous environmental pollutions, low thermodynamic performance, high exergy destruction rate, and high unit cost for the fresh water. This study aims at introducing a new method of pre-treatment for the brine discarded from each stage of the desalination plant to increase its concentration. The new method per-concentrates the brine by superheating the steam produced in the previous stage via recovering valuable thermal heat of the same effect. Due to a low temperature difference between the heat sink and heat source of this self-superheating scheme (i.e., the temperature difference between the...
Performance optimization of a new flash-binary geothermal cycle for power/hydrogen production with zeotropic fluid
, Article Journal of Thermal Analysis and Calorimetry ; Volume 145, Issue 3 , 2021 , Pages 1633-1650 ; 13886150 (ISSN) ; Hosseini Dehshiri, S ; Mostafaeipour, A ; Issakhov, A ; Techato, K ; Arockia Dhanraj, J ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
In this study, the performance of a system consisting of an organic Rankine cycle (ORC) for generating power and an electrolyzer for producing hydrogen with a zeotropic mixture as working fluid to recover waste heat in a geothermal flash-binary cycle is investigated from energy and exergy point of view. The study also investigates the effect of using zeotropic mixtures with different compositions as the ORC's working fluid rather than pure fluids. Using the particle swarm optimization (PSO) algorithm, the optimization is performed to maximize the power production of the entire system. The results show that using the combination of pentane with other pure fluids as working fluid led to...
Dynamic simulation of a solar ejector-based trigeneration system using TRNSYS-EES co-simulator
, Article Energy Science and Engineering ; Volume 10, Issue 3 , 2022 , Pages 707-725 ; 20500505 (ISSN) ; Jafari Mosleh, H ; Karami, M ; Sharif University of Technology
John Wiley and Sons Ltd
2022
Abstract
In this paper, a new configuration of a solar combined cooling, heating, and power (CCHP) system is proposed to recover the waste thermal energy of a steam power plant, which provides the cooling and heating needs of an apartment complex located in Tehran. The required energy of the system is supplied by the parabolic trough solar collectors (PTCs) and, if necessary, an auxiliary heater is also used. An ejector refrigeration cycle (ERC) and a steam Rankine cycle are used for cooling and power generation, respectively. The cycle is dynamically modeled over a year using a TRNSYS-EES co-simulator. It is found that the highest Rankine cycle efficiency is obtained in the cold months (January)...
Optimal design of solar concentrator in multi-energy hybrid systems based on minimum exergy destruction
, Article Renewable Energy ; Volume 190 , 2022 , Pages 78-93 ; 09601481 (ISSN) ; Saboohi, Y ; Fathi, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The paper presents a systematic approach to designing an imaging dish for a concentrator photovoltaic (CPV) system to minimize exergy destruction. The designed CPV system uniformly distributes light rays on the receiver (TPV/multi-junction PV) to enhance the conversion technology efficiency and lifetime. To this end, a parametric dish is designed using imaging optics and the numerical solution of a differential equation. Afterward, a Monte Carlo simulation is used to estimate the output energy and exergy of the CPV system with the parametric dish. Finally, an optimization algorithm finds the optimal design parameters to minimize the system's exergy destruction. The optimal design leads to a...
Energy, exergy and thermoeconomic analysis of a combined cooling, heating and power (CCHP) system with gas turbine prime mover
, Article International Journal of Energy Research ; Volume 35, Issue 8 , June , 2011 , Pages 697-709 ; 0363907X (ISSN) ; Amidpour, M ; Karimkashi, S ; Rezayan, O ; Sharif University of Technology
2011
Abstract
In this paper energy, exergy and thermoeconomic analysis of a combined cooling, heating and power (CCHP) system has been performed. Applying the first and second laws of thermodynamics and economic analysis, simultaneously, has made a powerful tool for the analysis of energy systems such as CCHP systems. The system integrates air compressor, combustion chamber, gas turbine, dual pressure heat recovery steam generator (HRSG) and absorption chiller to produce cooling, heating and power. In fact, the first and second laws of thermodynamics are combined with thermoeconomic approaches. Next, computational analysis is performed to investigate the effects of below items on the fuel consumption,...
Performance enhancement of waste heat extraction from generator of a wind turbine for freshwater production via employing various nanofluids
, Article Desalination ; Volume 478 , 2020 ; Rostami, S ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Water shortage issues are growing through the globe at higher rate than population growth. On the bright side, various methods are devised to capture energy from renewable energy or waste heat from different sectors. Among all inspected approaches, waste heat capturing through cooling process of the wind turbines' generators for desalination at small scale is paid less attention. However, in large wind farms, the scale of this dissipated thermal heat becomes appreciable which can drive several desalination units. Due to the above-pointed facts, the waste heat of a wind turbine with nominal capacity of 7358 kW and height of 24 m for desalinating seawater is inspected here, using a...
Cost and entropy generation minimization of a cross-flow plate fin heat exchanger using multi-objective genetic algorithm
, Article Journal of Heat Transfer ; Volume 133, Issue 2 , Nov , 2011 ; 00221481 (ISSN) ; Hajabdollahi, H ; Dincer, I ; Sharif University of Technology
2011
Abstract
In the present work, a thermal modeling is conducted for optimal design of compact heat exchangers in order to minimize cost and entropy generation. In this regard, an εNTU method is applied for estimation of the heat exchanger pressure drop, as well as effectiveness. Fin pitch, fin height, fin offset length, cold stream flow length, no-flow length, and hot stream flow length are considered as six decision variables. Fast and elitist nondominated sorting genetic algorithm (i.e., nondominated sorting genetic algorithm II) is applied to minimize the entropy generation units and the total annual cost (sum of initial investment and operating and maintenance costs) simultaneously. The results for...