Academic literature on the topic 'Overall exergy efficiency'
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Journal articles on the topic "Overall exergy efficiency":
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Ponnusamy, Sathyakala, Sundara Sai Gangadharan, and Balaji Kalaiarasu. "An exergy analysis for overall hidden losses of energy in solar water heater." Thermal Science, no. 00 (2020): 343. http://dx.doi.org/10.2298/tsci200530343p.
Abstract:
This study investigates the hidden thermal losses of glass plate, collector plate, water pipe and storage tank of solar water heater in the process of energy conversion. The present non-conventional energy methods are insufficient, whereas the exergy analysis provides a remarkable solution. Thus, employing the exergy analysis, entropy generation, exergy destruction and exergy efficiency of each subsystem of solar water heater are computed. The obtained results showed that the entropy generation and exergy destruction are high during the heat transfer in each subsystem. Henceforth, the existing solar water heater design is modified placing hexagonal honeycomb structure between the glass plate and the collector plate and also water pipe is insulated to trap huge amount of solar energy. The proposed design exhibits improved exergy efficiency when compared with the existing model, which enhances the performance of the system.
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Abuel, Paul Mikii, Abir Hossain Mridul, and Wilson Fidelis Ekpotu. "Efficiency Assessment of a Combined Heat and Power Plant Using Exergy Analysis." Journal of Sustainable Development 17, no. 2 (February 8, 2024): 55. http://dx.doi.org/10.5539/jsd.v17n2p55.
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This study conducted an exergy analysis of a cogeneration power plant utilizing gas turbines, air compressors, combustion chambers, heat recovery steam generators, heat exchangers, and pumps. The study performed an extensive exergy analysis of the system, focusing on each component's process and calculating its base efficiency while tabulating the corresponding exergy degradation. Relevant equations for mass, energy, and exergy were identified to determine optimal control volume conditions for an optimal system and boundary conditions that would enhance the design and reduce exergy destruction. The research project developed revisions and modifications necessary to the base system, utilizing available parameters and boundary conditions, to enable a second law analysis, improve the overall efficiency, and reduce irreversibility and the loss of exergy. The proposed modifications included the remodelling of the cogeneration plant by applying additional processes to utilize the excessive waste heat in the plant. The study further optimized the plant's efficiency by modifying individual system elements that yielded minimal exergy destruction to the overall design. The proposed modifications explored the best-case alteration on optimizing overall plant efficiency with minimum irreversibility compared to the initial analysis done. The technical contributions of this research project are the revisions and modifications that enabled a second law analysis and improved the overall efficiency of the cogeneration power plant.
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Guerrero-Martin, Camilo Andrés, Juan Sebastián Fernández-Ramírez, Jaime Eduardo Arturo-Calvache, Harvey Andrés Milquez-Sanabria, Fernando Antonio da Silva Fernandes, Vando José Costa Gomes, Wanessa Lima e Silva, Emanuele Dutra Valente Duarte, Laura Estefanía Guerrero-Martin, and Elizabete Fernandes Lucas. "Exergy Load Distribution Analysis Applied to the Dehydration of Ethanol by Extractive Distillation." Energies 16, no. 8 (April 18, 2023): 3502. http://dx.doi.org/10.3390/en16083502.
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This study presents the analysis of the exergy load distribution in a separation process by extractive distillation for ethanol dehydration. The methodology carried out is divided into three parts: the calculation of the flow exergy considering the physical and chemical exergies of the distillation process; the calculation of the primary and transformed exergy contributions considering the consumed exergy; and finally, the overall process efficiency, which shows the real percentage of energy being used in the process. The simulation of an extractive distillation separation system is carried out using Aspen Plus®, from Aspen Tech Version 9. In general, heat transfer processes (heating or cooling) are the ones that generate the greatest exegetic destruction, which is why they must be the operations that must be optimized. As a result of our case study, the local exergy efficiency of the extractive distillation column is 13.80%, which is the operation with the greatest energy loss, and the overall exergy efficiency of the separation system is 30.67%. Then, in order to increase exergy efficiency, a sensitivity analysis is performed with the variation of the azeotrope feed, number of stages, reflux ratio, and solvent feed variation on ethanol purity to reach an overall efficiency of 33.53%. The purity of ethanol is classified as higher than that of the specified, 99.65%.
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Malaine, Salek, Mohamed Charia, Najib Ababssi, Jilali Dardouch, and Abdellah Boulal. "Advanced exergetic study to assess the effects of rectification and distillation on absorption refrigerators." Thermal Science, no. 00 (2022): 147. http://dx.doi.org/10.2298/tsci220402147m.
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In this paper, an advanced exergetic study is carried out to improve the exergy efficiency and minimize the exergy losses of an absorption refrigerator. Two thermal processes based on rectification and distillation were proposed to meet this critical requirement. A numerical simulation model was established in the FORTRAN language, building on the analytical Gibbs free energy equations. This model was validated from a thermodynamic point of view by previously published results. Preliminary results showed that when the efficiency of the absorber and boiler is increased, the vapors produced by the boiler become enriched in ammonia, and the overall exergy efficiency increases, which reduces considerably the irreversibility of the components of the studied absorption system. A comparative study of the effect of these two thermal processes on the overall exergy efficiency and total exergy losses was evaluated simultaneously. The results show that the refrigerator with a distiller has a higher exergy efficiency (?ex=24.37 % at 86?C), and at the same time has a lower total exergy loss ( =457.45 kW) than the refrigerator with a rectifier (?ex=22.34 % at 85?C; =532.37 kW). This study reveals that the distillation process can contribute more to the exergy improvement and exergy loss minimization of the studied absorption refrigerator than the rectification process.
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Srimanickam, B., M. M. Vijayalakshmi, and Elumalai Natarajan. "Experimental Study of Exergy Analysis on Flat Plate Solar Photovoltaic Thermal (PV/T) Hybrid System." Applied Mechanics and Materials 787 (August 2015): 82–87. http://dx.doi.org/10.4028/www.scientific.net/amm.787.82.
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The objective of present study is to conduct exergy analysis on flat plate solar photovoltaic thermal (PV/T) hybrid system. The solar insolation, current, voltage, inlet and outlet air temperature of the cooling duct, ambient air temperature, and solar panel surface temperature are the major parameters used to calculate the energy and exergy efficiency. An amended electrical efficiency is used to estimate the electrical output and performance of PV/T hybrid system. Further, an enriched equation for the exergy efficiency of a PV/T hybrid system has been used for exergy analysis. Finally, parametric studies have been carried out. An extensive energy and exergy analysis is carried out to calculate the electrical and thermal parameters. The experimental results are in good agreement with the earlier studies. In addition to that, the electrical efficiency, thermal efficiency, electrical thermal efficiency, overall energy efficiency and exergy efficiency of PV/T hybrid system is found to be about 9.78%, 24.22%, 27.17%, 44.84% and 11.23% respectively.
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Fu, Yunchi, and Yanzhe Li. "Experimental Study on the Working Efficiency and Exergy Efficiency of the Vehicle-Mounted Thermoelectric Generator for Cold Chain Logistics Transportation Vehicle." Processes 11, no. 6 (June 11, 2023): 1782. http://dx.doi.org/10.3390/pr11061782.
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This paper investigates a vehicle-mounted thermoelectric generator system working efficiency and exergy efficiency in a cold chain logistics transport vehicle (CLVTEG). The study examines the impact of factors such as load resistance, temperature difference, and copper foam on the performance of CLVTEG. Results demonstrate that adding copper foam significantly improves the output power of CLVTEG, with 40 PPI copper foam showing a 1.8 times increase compared to no copper foam. Additionally, copper foam enhances working and exergy efficiency, with 10 PPI copper foam achieving the best overall efficiency. The study also explores the effect of temperature difference on CLVTEGs efficiency, observing an initial increase followed by a decrease. Overall, this research underscores the importance of considering work and exergy efficiency when evaluating thermoelectric generators. Adding copper foam in the CLVTEG central area enhances heat transfer, resulting in improved efficiency. These findings offer valuable insights for optimizing the design and operation of thermoelectric generators in cold chain logistics transport vehicles.
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Sejkora, Christoph, Lisa Kühberger, Fabian Radner, Alexander Trattner, and Thomas Kienberger. "Exergy as Criteria for Efficient Energy Systems—A Spatially Resolved Comparison of the Current Exergy Consumption, the Current Useful Exergy Demand and Renewable Exergy Potential." Energies 13, no. 4 (February 14, 2020): 843. http://dx.doi.org/10.3390/en13040843.
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The energy transition from fossil-based energy sources to renewable energy sources of an industrialized country is a big challenge and needs major systemic changes to the energy supply. Such changes require a holistic view of the energy system, which includes both renewable potentials and consumption. Thereby exergy, which describes the quality of energy, must also be considered. In this work, the determination and analysis of such a holistic view of a country are presented, using Austria as an example. The methodology enables the calculation of the spatially resolved current exergy consumption, the spatially resolved current useful exergy demand and the spatially resolved technical potential of renewable energy sources (RES). Top-down and bottom-up approaches are combined in order to increase accuracy. We found that, currently, Austria cannot self-supply with exergy using only RES. Therefore, Austria should increase the efficiency of its energy system, since the overall exergy efficiency is only at 34%. The spatially resolved analysis shows that in Austria the exergy potential of RES is rather evenly distributed. In contrast, the exergy consumption is concentrated in urban and industrial areas. Therefore, the future energy infrastructure must compensate for these spatial discrepancies.
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Minutillo, Mariagiovanna, Alessandra Perna, and Alessandro Sorce. "Exergy analysis of a biomass-based multi-energy system." E3S Web of Conferences 113 (2019): 02017. http://dx.doi.org/10.1051/e3sconf/201911302017.
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This paper focuses on a biofuel-based Multi-Energy System generating electricity, heat and hydrogen. The proposed system, that is conceived as refit option for an existing anaerobic digester plant in which the biomass is converted to biogas, consists of: i) a fuel processing unit, ii) a power production unit based on the SOFC (Solid Oxide Fuel Cell) technology, iii) a hydrogen separation, compression and storage unit. The aim of this study is to define the operating conditions that allow optimizing the plant performances by applying the exergy analysis that is an appropriate technique to assess and rank the irreversibility sources in energy processes. Thus, the exergy analysis has been performed for both the overall plant and main plant components and the main contributors to the overall losses have been evaluated. Moreover, the first principle efficiency and the second principle efficiency have been estimated. Results have highlighted that the fuel processor (the Auto-Thermal Reforming reactor) is the main contributor to the global exergy destruction (9.74% of the input biogas exergy). In terms of overall system performance the plant has an exergetic efficiency of 53.1% (it is equal to 37.7% for the H2 production).
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Sreekumar, Sreehari, Supriya Chakrabarti, Neil Hewitt, Jayanta Deb Mondol, and Nikhilkumar Shah. "Performance Prediction and Optimization of Nanofluid-Based PV/T Using Numerical Simulation and Response Surface Methodology." Nanomaterials 14, no. 9 (April 28, 2024): 774. http://dx.doi.org/10.3390/nano14090774.
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A numerical investigation was carried out in ANSYS Fluent® on a photovoltaic/thermal (PV/T) system with MXene/water nanofluid as heat transfer fluid (HTF). The interaction of different operating parameters (nanofluid mass fraction, mass flow rate, inlet temperature and incident radiation) on the output response of the system (thermal efficiency, electrical efficiency, thermal exergy efficiency, and electrical exergy efficiency) was studied using a predictive model generated using response surface methodology (RSM). The analysis of variance (ANOVA) method was used to evaluate the significance of input parameters affecting the energy and exergy efficiencies of the nanofluid-based PV/T system. The nanofluid mass flow rate was discovered to be having an impact on the thermal efficiency of the system. Electrical efficiency, thermal exergy efficiency, and electrical exergy efficiency were found to be greatly influenced by incident solar radiation. The percentage contribution of each factor on the output response was calculated. Input variables were optimized using the desirability function to maximize energy and exergy efficiency. The developed statistical model generated an optimum value for the mass flow rate (71.84 kgh−1), the mass fraction (0.2 wt%), incident radiation (581 Wm−2), and inlet temperature (20 °C). The highest overall energy and exergy efficiency predicted by the model were 81.67% and 18.6%, respectively.
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Nenov, Valentin, Lyubka Atanasova, Hyusein Yemendzhiev, and Ralitza Koleva. "Microbial Electrolysis Cell Exergy Evaluation." Processes 12, no. 2 (February 2, 2024): 319. http://dx.doi.org/10.3390/pr12020319.
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Bio-electrochemical systems have increasingly become the focus of research due to their potential in environmental biotechnology, particularly in the domains of waste utilization and energy recovery. A prominent method within this domain is the transformation of organic matter into hydrogen via microbial electrolysis cells (MECs). This study offers a thorough analysis of MEC performance, employing exergy analysis and incorporating relevant data from the existing literature. The findings of this research indicate a relationship between process efficiency and effective electron transfer originating from biological oxidation to the cathode reaction, facilitating hydrogen generation. The assessment performed revealed that the exergy efficiency of the process varies by a wide range, depending on conditions such as substrate type and concentration, applied external voltage, and the presence of specific inhibitors. This interplay between substrate concentration, overall efficiency, and energy requirement underlines the complex dynamics of optimizing MEC performance. Our insights provide understanding of the challenges in bio-electrochemical systems, offering implications for their sustainable and efficient use in environmental biotechnology. The theoretical analysis involved assessing the utilization of glucose and glycerol, along with the evaluation of electrical energy consumption and hydrogen yield. Our results demonstrate that a higher applied voltage is associated with greater exergy efficiency. Furthermore, after comparing the use of glucose and glycerol as substrates, our study supports the preferential application of glucose for enhanced efficiency.
Book chapters on the topic "Overall exergy efficiency":
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Patro, Chandra Sekhar. "Influence of Retention Policies on Employee Efficiency and Organization Productivity." In Advances in Logistics, Operations, and Management Science, 124–49. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-4666-9758-4.ch008.
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In the continuously developing economy, organizations should be able to anticipate the technological innovations and compete with other organizations worldwide. This need makes an organization's ability to evolve through its employees' learning and continuous development. In this context employee retention has become a most critical issue for all the organizations as a result of the shortage of skilled labor, economic growth and employee turnover. Employee retention refers to the various policies and practices which let the employees stick to an organization for a longer period of time. The employees are the real assets of any organization, so the management should exert some effort to determine the non-monetary interests and preferences of its key employees, and then attempt to meet these preferences in action. This study is an attempt to identify the various retention policies practiced in different public and private organisations, and evaluate the effectiveness of these policies on employees' efficiency and its influence on the overall productivity of an organisation.
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Gurcaylilar-Yenidogan, Tugba, and Safak Aksoy. "Untangling the Innovativeness-Performance Puzzle." In Advances in Business Strategy and Competitive Advantage, 85–103. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1169-5.ch005.
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This chapter investigates the relationships between innovativeness and firm performance from a multidimensional viewpoint. As previous studies have shown controversial results on the performance implications for innovative capacity, the promising venue for the innovation research study is to address the question of under which conditions innovativeness leads to improved financial performance. To this end, the results of this study demonstrate some major findings. First, non-technical innovativeness exerts positive influence over technical innovativeness. Second, novelty of technical innovation activities causes a diminishing effect on financial performance due to the ambiguity of value-creation. Third, technical innovativeness enhances financial performance when the relationship between technical innovativeness and financial performance is mediated by market effectiveness and production efficiency. Overall, this chapter clarifies the conflicting results on the innovativeness-financial performance link and hence contributes to the innovation literature.
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Kolekar, Shivaji N. "ROOTSTOCKS FOR TROPICAL AND SUB- TROPICAL FRUIT CROPS." In Futuristic Trends in Agriculture Engineering & Food Sciences Volume 3 Book 16, 214–34. Iterative International Publisher, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3bcag16p6ch2.
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When it comes to fruit crops, rootstocks are crucial in determining how productive orchards are. separate growth results can be obtained by budding or grafting two separate plants together that have complementary traits. This variance is apparent when taking into account the relative importance of rootstocks with respect to precocity, yield, and tree size control; additionally, variations in crop load, annual phenological cycles, fruit respiration patterns, and canopy management approaches are all taken into account. However, the impact of these factors on physiological, biochemical, and molecular aspects is still not fully comprehended. Rootstocks exert their influence on scion growth, vigor, and structure, as well as the precocity of the scion, flowering abundance, the likelihood of successful fruit set, and yield efficiency. The utilization of rootstocks in various fruit crops significantly impacts fruit crop production by influencing factors such as canopy structure, nutrient absorption, flowering, yield, and fruit quality (Rom et al., 1987). Moreover, rootstocks can also mitigate both biotic and abiotic stressors, including challenges related to soil pathogens, temperature extremes, salinity, and nutritional imbalances (Reddy et al., 2003). Rootstocks play a central role in determining the overall efficiency of orchards, encompassing responsibilities for water and mineral uptake and providing tree stability. They can provide some degree of tolerance to soils that may be overly moist or dry, and they are essential in regulating the size of trees. Studies and research on the selection and use of appropriate rootstocks in crops such as citrus, mango, and grapes have previously been carried out in a number of nations, with an emphasis on controlling growth vigor, nutrient absorption, soil salinity, moisture stress, and yield efficiency. India has yet to fully exploit the significant potential of rootstocks for many commercial fruit crops, and there is a need to identify rootstocks with optimal attributes that align with the specific environmental conditions in which the trees will be cultivated. This implies that a rootstock deemed most suitable for a particular variety and set of environmental conditions may not be the ideal choice for a different variety in a distinct environmental context (Nimbolkar et al., 2016). As such, comprehensive research on rootstocks for tropical and sub-tropical fruit crops becomes imperative.
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Bhadoriya, Ankita, Kuldeep Vinchurkar, Shivangi Patidar, Praveen Sharma, Pritesh Paliwal, and Bimlesh Kumar Rathore. "DATA INTEGRITY - A CRUCIAL REQUIREMENT FOR PHARMACEUTICAL INDUSTRIES REGULATORY COMPLIANCE." In Futuristic Trends in Chemical Material Sciences & Nano Technology Volume 3 Book 13, 164–83. Iterative International Publishers, Selfypage Developers Pvt Ltd, 2024. http://dx.doi.org/10.58532/v3becs13p2ch2.
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In the dynamic realm of pharmaceuticals, the assurance of data integrity emerges as a linchpin for achieving and sustaining regulatory compliance. This book chapter meticulously explores the multifaceted dimensions of data integrity, dissecting its significance within the stringent frameworks governing the pharmaceutical industry. Acknowledging data as the lifeblood of drug development and production, the chapter scrutinizes the profound impact that lapses in data integrity can exert on the quality, safety, and efficacy of pharmaceutical products. Navigating through the complex terrain of regulatory requirements, the chapter elucidates key concepts underpinning data integrity, ranging from the fundamental principles to the intricacies of implementation. It delves into the challenges inherent in maintaining data integrity throughout the product life cycle, addressing issues such as data accuracy, completeness, and consistency. Practical insights are offered on establishing robust data management systems that not only meet regulatory expectations but also elevate overall operational efficiency. With a focus on proactive measures, the chapter outlines best practices for data governance, validation, and documentation. Case studies and real-world examples underscore the tangible consequences of inadequate data integrity, emphasizing the critical need for a steadfast commitment to regulatory compliance. By synthesizing theoretical frameworks with practical guidance, this chapter serves as a comprehensive resource for pharmaceutical professionals striving to fortify their systems against data integrity vulnerabilities. Ultimately, the pursuit of data integrity is portrayed not merely as a regulatory obligation but as a fundamental ethical imperative, safeguarding public health and reinforcing the industry's commitment to the highest standards of quality and transparency.
Conference papers on the topic "Overall exergy efficiency":
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Rosen, Marc A. "Impact on Overall Efficiency of Component Efficiency Increases for an Existing Thermal Electrical Generating Station." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33149.
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Most electrical generating utilities are striving to improve the efficiencies of their existing thermal electric generating stations, many of which are old. Exergy methods have been shown to provide meaningful insights that can assist in increasing the efficiency of conventional coal-to-electricity technologies. Here, exergy analysis is used to assess measures for improving the efficiencies of coal-fired electrical generating stations. This scope of the study is limited to minor practical improvements, which can be undertaken with limited effort and cost and are not overly complex. The plant considered is the coal-fired Nanticoke Generating Station (GS) in Ontario, Canada. The findings suggest that the results of exergy analyses should be used, along with other pertinent information, to guide efficiency improvement efforts for thermal generating stations. Also, efficiency improvement efforts should focus on plant components responsible for the largest exergy losses: the steam generator (where large losses occur from combustion heat transfer across large temperature differences), the turbines, the electrical generator and the transformer. Possible improvements in these areas should be assessed in conjunction with other criteria, and other components should be considered where economically beneficial improvements can be identified.
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Rosen, M. A., and M. N. Le. "Efficiency Analysis of a Process Design Integrating Cogeneration and District Energy." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0306.
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Abstract An efficiency analysis, accounting for both energy and exergy considerations, is reported of a design for cogeneration-based district energy proposed for the city of Edmonton, Canada, by the utility Edmonton Power. The original concept using central electric chillers, as well as two variations (one considering single-effect and the other double-effect absorption chillers), are examined. The energy- and exergy-based results differ markedly (e.g., overall energy efficiencies are shown to vary for the three configurations considered from 83 to 94%, and exergy efficiencies from 28 to 29%). For the overall processes, as well as individual subprocesses and selected combinations of subprocesses, the exergy efficiencies are generally found to be more meaningful and indicative of system behaviour than the energy efficiencies.
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Horlock, J. H. "The Effect of Heat Exchanger Effectiveness and Exergy Loss in the Estimation of Cycle Efficiency." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-352.
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The effect of heat exchanger effectiveness on cycle efficiency is well known. But the relationship between exergy loss in heat exchangers and the effectiveness is less well documented. In this paper the relationship is explored; it is shown how the exergy loss in the heat exchanger is changed as effectiveness is altered. It is also shown how the exergy losses in other components of the recuperative gas turbine cycle are changed, together with the overall cycle performance, as the effectiveness is varied.
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Hossain, Mohammad A., Md Taibur Rahman, Mohammad Ikthair Hossain Soiket, and Sarzina Hossain. "Investigation and Improvement of Thermal Efficiency of Hypersonic Scramjet." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37385.
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This work is focused on investigation of thermal efficiency of a Hypersonic scramjet engine and propose some improvement of thermal efficiency based on thermodynamic and fluid flow analysis. Thermal management system is one of the main research fields in scramjet design. As it has no moving parts, the total thermal efficiency depends on inlet conditions, conditions of combustor exit and conditions of the engine exit. A combustor exit condition dictates the velocity and temperature after combustion. we concentrate our focus on this section. The first part of the paper, we tried to describe the fundamental exergy relationship for scramjet and we developed the relation of exergy distribution and exergy delivery rate. From an extensive literature review, we have found the relations between fluid velocity, pressure and temperature, which is described in the later part of the paper. Our main focus is to develop a combined relation of thermal efficiency in terms of engine exit velocity, temperature and air-fuel ratio. Different characteristic parameters such as overall efficiency, thermal efficiency, specific impulse have been determined at different inlet temperature ratio or the cycle static temperature ratio (T3/T0) and an optimum inlet temperature ratio is proposed for maximum overall efficiency.
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Cheremnykh, Ekaterina, and Fabio Gori. "Exergy and Extended Exergy Cost Assessment of a Commercial Truck." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37860.
Abstract:
To gain a clearer understanding of the overall economic and environmental impact of the manufacturing process of a single vehicle, including its operational phase, it is useful to examine the process in a life-cycle perspective and with an exergy approach.. The method of Extended Exergy Accounting (EEA) has already provided reliable results both for the assessment of entire countries and for the analysis of specific industrial sectors. National transportation sectors, generally reputed inefficient, have been the subject of a series of energy and exergy efficiency studies, though so far the phase of vehicle manufacturing was not specifically addressed. The present study is an attempt to quantitatively develop the complex evaluation of the exergy cost of a single vehicle, in particular of a commercial truck produced in the US (for which the available data are extensive and reliable). In the analysis performed in the course of this study, the last version of EEA has been employed, with the latest available data on the allocation coefficients for labour and capital cost factors. Particular attention is given to data selection and their processing. The values of the exergy costs for materials flows, energy inputs and of their equivalents for capital, labour and environment remediation are predicted. The results shows numerically the exergetic costs of economic, labour, material and energy inputs, and emphasize the further research of environmental remediation costs.
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Chow, Raymond, George J. Nelson, and Jay L. Perry. "Electrolyzer Exergy Analysis for an Environmental Control and Life Support System." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88119.
Abstract:
An exergy based analysis of the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS) is conducted to assess its overall performance. Exergy is chosen as a measure of performance because it accounts for both the first and second laws of thermodynamics. The exergy efficiency of a system is first defined as the total exergy destroyed by the system relative to the total exergy input to the system. To determine the ECLSS exergy efficiency, the system is divided into constituent subsystems which in turn are divided into assemblies and components. Based on this system decomposition, exergy balances are derived for each assembly or component. Exergy balances and supporting calculations are implemented in MATLAB® code. The major subsystems of the ECLSS considered in this analysis include the Atmosphere Revitalization Subsystem (ARS), Atmosphere Control and Supply Subsystem (ACS), Temperature and Humidity Control Subsystem (THC), Water Recovery and Management Subsystem (WRM), and Waste Management Subsystem (WM). This paper focuses on the ARS and its constituent assemblies and components. Exergy efficiency of the ARS and its constituent assemblies and components is first presented. The Oxygen Generation Assembly (OGA), an assembly within the ARS, is then highlighted because the exergy destruction by the OGA is a large magnitude contributor to the overall exergy destruction of the ECLSS. The OGA produces oxygen to meet the crew’s metabolic demand via water electrolysis in a proton exchange membrane (PEM) electrolyzer. The exergy destruction of the OGA’s PEM electrolyzer is a function of the amount of oxygen produced, which determines the necessary current density and voltage drop across the PEM electrolyzer. In addition, oxygen production in the PEM electrolyzer requires deviation from the Nernst potential, presenting trade-offs between the exergy efficiency and critical life support functions. The results of parametric studies of PEM electrolyzer performance are presented with an emphasis on the impacts of polarization and operational conditions on exergy efficiency.
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Yilanci, Ahmet, Ibrahim Dincer, and Harun Kemal Ozturk. "Determination of Some Thermodynamic Parameters for a Hybrid Solar-Hydrogen System." In ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54342.
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In this paper, we undertake a study to investigate the performance of a hybrid photovoltaic-hydrogen system through energy and exergy efficiencies, improvement potential. This will help identify the irreversibilities (exergy destructions) for performance improvement purposes. Energetic and exergetic renewability ratios are also introduced for grid dependent hybrid energy systems. A case study is presented to highlight the importance of the thermodynamic parameters and show them using some actual and theoretical data. Three different energy demand options from photovoltaic panels to the consumer are identified and considered for the analysis. The minimum and maximum overall energy and exergy efficiencies of the system are calculated based on these options. It is found that the overall energy efficiency values of the system vary between 0.88% and 9.7% while minimum and maximum overall exergy efficiency values of the system are 0.77% and 9.3%, respectively. The monthly improvement potential of the system is also studied to investigate the seasonal performance.
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Boyano, A., G. Tsatsaronis, T. Morosuk, and A. M. Blanco-Marigorta. "Advanced Exergetic Analysis of Chemical Processes." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10463.
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In this paper, a steam methane reforming (SMR) process for the production of hydrogen is studied. The process is based on two chemical reactions (reforming and water-gas-shift reaction). For each component but especially focusing on the chemical reactors, the avoidable part of the exergy destruction is estimated. The assumptions required for these calculations are discussed in detail and represent the main contribution of this work to the development of exergy-based methods for the analysis of chemical processes. In an advanced exergy analysis, the exergy destruction within a component is split into avoidable/unavoidable parts. This splitting improves understanding of the sources of thermodynamic inefficiencies and facilitates a subsequent optimization of the overall process. The overall SMR process is characterized by high energetic and exergetic efficiencies. However, the majority of the exergy destruction is caused by the irreversibility of chemical reactions and heat transfer. Results of this paper suggest options for improving the efficiency of the overall process.
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Ray, Tapan K., Pankaj Ekbote, Ranjan Ganguly, and Amitava Gupta. "Second-Law Analysis in a Steam Power Plant for Minimization of Avoidable Exergy Destruction." In ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90144.
Abstract:
Performance analysis of a 500 MWe steam turbine cycle is performed combining the thermodynamic first and second-law constraints to identify the potential avenues for significant enhancement in efficiency. The efficiency of certain plant components, e.g. condenser, feed water heaters etc., is not readily defined in the gamut of the first law, since their output do not involve any thermodynamic work. Performance criteria for such components are defined in a way which can easily be translated to the overall influence of the cycle input and output, and can be used to assess performances under different operating conditions. A performance calculation software has been developed that computes the energy and exergy flows using thermodynamic property values with the real time operation parameters at the terminal points of each system/equipment and evaluates the relevant rational performance parameters for them. Exergy-based analysis of the turbine cycle under different strategic conditions with different degrees of superheat and reheat sprays exhibit the extent of performance deterioration of the major equipment and its impact to the overall cycle efficiency. For example, during a unit operation with attemperation flow, a traditional energy analysis alone would wrongly indicate an improved thermal performance of HP heater 5, since the feed water temperature rise across it increases. However, the actual performance degradation is reflected as an exergy analysis indicates an increased exergy destruction within the HP heater 5 under reheat spray. These results corroborate to the deterioration of overall cycle efficiency and rightly assist operational optimization. The exergy-based analysis is found to offer a more direct tool for evaluating the commercial implication of the off-design operation of an individual component of a turbine cycle. The exergy destruction is also translated in terms of its environmental impact, since the irretrievable loss of useful work eventually leads to thermal pollution. The technique can be effectively used by practicing engineers in order to improve efficiency by reducing the avoidable exergy destruction, directly assisting the saving of energy resources and decreasing environmental pollution.
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Behrang, A., H. Abbas, C. Istchenko, A. Solano, and S. Kisra. "A Pore-To-Process Digital Design Methodology for Life-Cycle Assessment of a Geothermal Power Plant." In ADIPEC. SPE, 2023. http://dx.doi.org/10.2118/217007-ms.
Abstract:
Abstract The development and operation of geothermal plants play a vital role in the transition to sustainable and low-carbon energy systems. In this paper we presented a seamless and flexible pore-to-process digital solution for the design and assessment of geothermal systems, encompassing the geothermal reservoir, gathering network, and geothermal power plant. Our primary focus in this study is on the geothermal power plant. This includes a detailed analysis of the functionality and performance of two common geothermal power plants; 1. A single-flash power plant and a double-flash geothermal power plant within the overall system. This work shows that overall exergy efficiency of the studies geothermal power plants decreases overtime due to a decrease in the geothermal reservoir quality. The analysis performed in this study demonstrates that variation of the inlet separator pressure affects the overall plant behavior. The parametric studies also display the overall exergy efficiency of the power plants as well as the turbine power reduction as the inlet separator pressure increases. This is due to lower efficiency in converting the available energy into useful work. Our studies displayed that a substantial portion of the available exergy in the geothermal fluid is being dissipated in the condenser. Therefore, optimizing the condenser design and operation becomes a crucial factor for enhancing the overall efficiency of the studies of geothermal power plants.