Journal articles on the topic 'Overall exergy efficiency'
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1
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.
2
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.
Abstract:
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.
3
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.
Abstract:
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%.
4
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.
Abstract:
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.
5
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.
Abstract:
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.
6
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.
Abstract:
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.
7
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.
Abstract:
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.
8
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.
Abstract:
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).
9
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.
Abstract:
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.
10
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.
Abstract:
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.
11
Wang and Fu. "Thermodynamic Investigation of an Integrated Solar Combined Cycle with an ORC System." Entropy 21, no. 4 (April 22, 2019): 428. http://dx.doi.org/10.3390/e21040428.
Abstract:
An integrated solar combined cycle (ISCC) with a low temperature waste heat recovery system is proposed in this paper. The combined system consists of a conventional natural gas combined cycle, organic Rankine cycle and solar fields. The performance of an organic Rankine cycle subsystem as well as the overall proposed ISCC system are analyzed using organic working fluids. Besides, parameters including the pump discharge pressure, exhaust gas temperature, thermal and exergy efficiencies, unit cost of exergy for product and annual CO2-savings were considered. Results indicate that Rc318 contributes the highest exhaust gas temperature of 71.2℃, while R113 showed the lowest exhaust gas temperature of 65.89 at 800 W/m2, in the proposed ISCC system. The overall plant thermal efficiency increases rapidly with solar radiation, while the exergy efficiency appears to have a downward trend. R227ea had both the largest thermal efficiency of 58.33% and exergy efficiency of 48.09% at 800W/m2. In addition, for the organic Rankine cycle, the exergy destructions of the evaporator, turbine and condenser decreased with increasing solar radiation. The evaporator contributed the largest exergy destruction followed by the turbine, condenser and pump. Besides, according to the economic analysis, R227ea had the lowest production cost of 19.3 $/GJ.
12
Li, Peng, Baokuan Li, Zhongqiu Liu, and Wenjie Rong. "Evaluation and analysis of exergoeconomic performance for the calcination process of green petroleum coke in vertical shaft kiln." Thermal Science, no. 00 (2021): 294. http://dx.doi.org/10.2298/tsci210609294l.
Abstract:
The main objective of this paper is to establish a mathematical framework to analyze the complex thermal economic performance of the calcination process. To find the factors affecting exergy efficiency loss, different exergy destruction is investigated in detail. Furthermore, the exergy flow cost model for exergy cost saving has also been developed. The results show that the vertical shaft furnace is a self-sufficiency equipment without additional fuel required, but the overall exergy destruction accounts for 54.11% of the total exergy input. In addition, the energy efficiency of the waste heat recovery boiler and thermal deaerator are 83.52% and 96.40%, whereas the exergy efficiency of the two equipment are 65.98% and 94.27%. Furthermore, the import exergy flow cost of vertical shaft furnace, waste heat recovery boiler and thermal deaerator are 366.5197 RMB/MJ, 0.1426 RMB/MJ and 0.0020RMB/MJ, respectively. Based on the result, several suggestions were proposed to improve the exergoeconomic performance. Assessing the performance of suggested improvements, the total exergy destruction of vertical shaft furnace is reduced to 134.34 GJ/h and the exergy efficiency of waste heat recovery boiler is raised up to 66.02%. Moreover, the import exergy flow cost of the three different equipment is reduced to 0.0329 RMB/MJ, 0.1304 RMB/MJ and 0.0002 RMB/MJ, respectively.
13
Hasanuzzaman, Md, R. Saidur, and N. A. Rahim. "Analysis of Energy and Exergy of an Annealing Furnace." Applied Mechanics and Materials 110-116 (October 2011): 2156–62. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.2156.
Abstract:
Furnace is the most common and important part in metal industries. The useful concept of energy and exergy utilization is analyzed to investigate the energy and exergy efficiency, exergy losses, energy savings and cost benefit of an annealing furnace. The exergy efficiency of the combustor is found to be 47.05 %. The energy and exergy efficiencies of the annealing chamber are found to be 17.74 % and 12.86 % respectively. The overall energy and exergy efficiencies of the furnace are found to be 16.86 % and 7.30 % respectively. The annealing chamber is the major contributor for exergy destruction about 57 % of the annealing furnace. By using a heat recovery system from flue gas, about 8.11% of fuel can be saved within the payback period of less than 2 months.
14
Rosengarten, G., G. Morrison, and M. Behnia. "A Second Law Approach to Characterising Thermally Stratified Hot Water Storage With Application to Solar Water Heaters." Journal of Solar Energy Engineering 121, no. 4 (November 1, 1999): 194–200. http://dx.doi.org/10.1115/1.2888166.
Abstract:
This paper presents a method of characterising and evaluating the performance of hot water storage systems in terms of their temperature distribution. The change in exergy from the stratified state to the delivery state depends on the stored energy and the stratification. It can thus he used to define the storage efficiency for sensible heat storage devices. A new parameter that isolates the stratification component of the exergy is defined and called the stratification efficiency. The effect of temperature distribution, delivery temperature and tank cross-section on exergy and stratification efficiency is investigated. The advantage that stratification offers over a mixed tank is examined in terms of the storage efficiency and overall solar water heating system performance. Exergy is used to assess the operation of mantle heat exchangers in solar water heating systems and it is shown that exergy and stratification efficiency, as well as energy, should be used to ascertain the performance of such heat exchangers.
15
Bertel-Pérez, Forlin, Grisel Cogollo-Cárcamo, and Ángel Darío González-Delgado. "Assessing Exergy Efficiency in Computer-Aided Modeled Large-Scale Production of Chitosan Microbeads Modified with Thiourea and Magnetite Nanoparticles." Sustainability 15, no. 19 (October 3, 2023): 14443. http://dx.doi.org/10.3390/su151914443.
Abstract:
Chitosan, the deacetylated derivative of chitin, is a biopolymer with many applications in different sectors, such as pharmaceutical, food, and wastewater treatment, amongst others. It can be used as a source for synthesizing bioadsorbents modified with chelators and nanoparticles for the removal of pollutants. In this report, we conducted an exergy analysis to evaluate the large-scale production of chitosan-based bioadsorbents modified with iron nanoparticles and chelators. The objective was to identify energy inefficiencies and propose technological enhancements to improve energy utilization. The process was simulated using Aspen Plus V.10® software, enabling the quantification of chemical and physical exergies for the species and streams involved. We calculated process irreversibilities, exergy losses, waste exergy, and utility exergy flows for each stage and the overall process. These findings provide valuable insights into optimizing energy utilization in the production of chitosan-based bioadsorbents. The overall exergy efficiency was 4.98%, with the washing and drying stages of nanoparticles and adsorbent synthesis accounting for the largest contribution to process irreversibilities and exergy destruction. To increase the global exergy efficiency of the process, it is proposed to implement process improvement strategies, such as mass or energy integration, to obtain better energy performance.
16
Pirkandi, J., A. M. Joharchi, and M. Ommian. "Thermodynamic and exergic modelling of a combined cooling, heating and power system based on solid oxide fuel cell." Journal of Mechanical Engineering and Sciences 13, no. 4 (December 30, 2019): 6088–111. http://dx.doi.org/10.15282/jmes.13.4.2019.23.0479.
Abstract:
In this research, thermodynamic and exergic analyses have been carried out on a combined cooling, heating and power cogeneration system that includes a solid oxide fuel cell and a single-effect lithium bromide absorption chiller. Results indicate that by increasing the system inlet air flow rate, the overall efficiency of the hybrid system is reduced, due to the reduction of the cell’s working temperature and exhaust gases temperature; while an increase in the working pressure of the system has no effect on its efficiency. The results also show that by raising the temperature of exhaust gases, the rate of exergy destruction diminishes, while the rate of exergy loss in the hybrid system increases. In the absorption chiller cycle, the maximum exergy destruction rate occurs in the generator, and the minimum rate is achieved in the pressure-reducing valve, between the evaporator and the condenser. Also, in the fuel cell cycle, the highest exergy destruction rate occurs in the heat exchanger of the inlet air to the cell, and the lowest exergy destruction rate occurs in the two water pumps. Moreover, the entropy generation rate and the exergy destruction rate of the fuel cell cycle are higher than those of the chiller cycle.
17
Mizobe, Koki, Chairunnisa, Kyaw Thu, and Takahiko Miyazaki. "Potential Evaluation of Power-to-Gas system by using Wind Turbine and PEM." E3S Web of Conferences 465 (2023): 01011. http://dx.doi.org/10.1051/e3sconf/202346501011.
Abstract:
The Power-to-Gas (PTG) is one of the progressing technologies that enables the conversion of electrical energy into hydrogen or methane gas. This study focuses on the comprehensive analysis of energy efficiency, exergy efficiency, and exergy destruction rate within the PTG overall system. The investigation covers the evaluation of the wind turbine for power generation, the proton exchange membrane (PEM) employed in hydrogen production, and the methanation unit dedicated to methane production. The analysis examines the overall system as well as each individual component. By quantifying the energy and exergy efficiencies, this study provides potential improvements for maximizing the PTG system's overall effectiveness. The outcomes of this study contribute to the advancement and deployment of PTG technologies, thereby facilitating the integration of renewable energy sources and promoting sustainable energy solutions.
18
G. L., David, Sodiki J. I., and Nkoi B. "Performance Evaluation of a Chiller Plant in a Bottling Company." International Journal for Research in Applied Science and Engineering Technology 11, no. 1 (January 31, 2023): 601–10. http://dx.doi.org/10.22214/ijraset.2023.48610.
Abstract:
Abstract: This study is focused on the performance evaluation of a water-cooled chiller. Exergy analysis of a water-cooled chiller was carried out in order to identify the contributions of individual components to the total exergy destruction. The second law efficiency of each component as well as the exergetic efficiency of the chiller were assessed. Data were taken at two-hour intervals (six readings daily) for thirty days. Data obtained from the chiller inventory records include suction and discharge pressure and temperature of the refrigerant in the compressor, as well as temperature and mass flow rates of cooling water and chilled water. Other properties of the refrigerant were obtained from ammonia property table. From the results obtained, the compressor was identified as the largest contributor to exergy destruction (about 59% of the total exergy destruction in the chiller), the evaporator contributed about 16%, the condenser contributed 20% while the throttle valve contributed the least to exergy destruction (5%). It was ascertained that the evaporator has the highest second law efficiency of 70.29%, while the efficiencies of the compressor and condenser were 60.01% and 36.09%, respectively. The average exergetic efficiency of the chiller was found to be 35.10%. The overall results reveal that the potential capacity of the chiller remained unutilized. Measures to improve the performance indices and overall efficiency of the chiller have been suggested in this study
19
Liu, Zhiqiang, Zhixiang Zeng, Chengwei Deng, and Nan Xie. "Advanced Exergy Analysis of an Absorption Chiller/Kalina Cycle Integrated System for Low-Grade Waste Heat Recovery." Processes 10, no. 12 (December 6, 2022): 2608. http://dx.doi.org/10.3390/pr10122608.
Abstract:
Exergy analysis and advanced exergy analysis of an absorption chiller/Kalina cycle integrated system are conducted in this research. The exergy destruction of each component and overall exergy efficiency of the cascade process have been obtained. Advanced exergy analysis investigates the interactions among different components and the actual improvement potential. Results show that among all the equipment, the largest exergy destruction is in the generators and absorber. System exergy efficiency is obtained as 35.52%. Advanced analysis results show that the endogenous exergy destruction is dominant in each component. Interconnections among different components are not significant but very complicated. It is suggested that the improvement priority should be given to the turbine. Performance improvement of this low-grade waste heat recovery process is still necessary because around 1/4 of the total exergy destruction can be avoided. Exergy and advanced exergy analysis in this work locates the position of exergy destruction, quantifies the process irreversibility, presents the component interactions and finds out the system improvement potential. This research provides detailed and useful information about this absorption chiller/Kalina cycle integrated system.
20
Sukchai, Sukruedee, Yodthong Mensin, and Wikarn Wansungnern. "Comparative Analysis of Exergy and Efficiency for Stratified Thermal Storage Tank with Solar Flat Plate and Evacuated Tube Collectors." Applied Mechanics and Materials 855 (October 2016): 114–18. http://dx.doi.org/10.4028/www.scientific.net/amm.855.114.
Abstract:
In recent years, solar water heating technology has got the major importance in water heating applications. For the efficient and effective working of solar water heaters, storage of the hot water is the main issue in this water heating technologies. This paper mainly presents the exergy and efficiency comparison between the solar flat plate water heater and evacuated tube water heater. A five level stratified thermal storage tank is designed and developed for this analysis. At each level of the tank, temperature of the water is collected for each one hour interval from 9:00 to 16:00 hours in both cases and the overall exergy and efficiency of the two water heaters were calculated. The average efficiency of all the levels for flat plate and evacuated tube collectors are 7.91% and 8.20% respectively. The overall system efficiency is obtained as 39.54% for flat plate and 41.00% for evacuated tube solar collector. At each level exergy is calculate for both systems and the average exergy of all the levels for flat plate collector is 4.243 kW and for evacuated tube solar collector is 4.371 kW.
21
Silva Ortiz, Maciel Filho, and Posada. "Mass and Heat Integration in Ethanol Production Mills for Enhanced Process Efficiency and Exergy-Based Renewability Performance." Processes 7, no. 10 (September 27, 2019): 670. http://dx.doi.org/10.3390/pr7100670.
Abstract:
This paper presents the process design and assessment of a sugarcane-based ethanol production system that combines the usage of both mass and heat integration (pinch analysis) strategies to enhance the process efficiency and renewability performance. Three configurations were analyzed: (i) Base case: traditional ethanol production (1G); (ii) mass-integrated (1G2G); and (iii) mass and heat-integrated system (1G2G-HI). The overall assessment of these systems was based on complementary approaches such as mass and mass–heat integration, energy and exergy analysis, exergy-based greenhouse gas (GHG) emissions, and renewability exergy criteria. The performances of the three cases were assessed through five key performance indicators (KIPs) divided into two groups: one is related to process performance, namely, energy efficiency, exergy efficiency, and average unitary exergy cost (AUEC), and the other one is associated to environmental performance i.e., exergy-based CO2-equation emissions and renewability exergy index. Results showed a higher exergy efficiency of 50% and the lowest AUEC of all the systems (1.61 kJ/kJ) for 1G2G-HI. Furthermore, the destroyed exergy in 1G2G-HI was lower by 7% and 9% in comparison to the 1G and 1G2G cases, respectively. Regarding the exergy-based GHG emissions and renewability performance (λindex), the 1G2G-HI case presented the lowest impacts in terms of the CO2-equivalent emissions (94.10 gCO2-eq/MJ products), while λindex was found to be environmentally unfavorable (λ = 0.77). However, λindex became favorable (λ > 1) when the useful exergy of the byproducts was considered.
22
Hassan, Mohanad F., Abdul Hadi N. Khalifa, and Ahmed J. Hamed. "Exergy Analysis of Humidification–Dehumidification Water Desalination Unit Working under Baghdad Conditions." International Journal of Air-Conditioning and Refrigeration 29, no. 02 (April 23, 2021): 2150017. http://dx.doi.org/10.1142/s2010132521500176.
Abstract:
Water desalination unit powered by renewable energy sources is sometimes needed at places far from the energy grid lines. Consequently, even countries with rich energy resources, such as the Arabian Gulf countries, have shown strong interest in desalination processes that often use renewable energy sources. This work aims to conduct an exergy analysis of solar-powered humidification–dehumidification (HDH) unit. The exergy analysis input data are extracted from a previous work conducted in August 2020 under Baghdad conditions, 33.3∘N latitude and 44.14∘E longitude. The previous work’s HDH unit consisted of six parabolic trough solar collectors (PTSCs), with a total aperture area of 8.76[Formula: see text]m2. Meteonorm v7.3 software was used to obtain the weather data for Baghdad City, Iraq. The HDH unit results had revealed low exergy efficiency, where the maximum overall exergy efficiency was 0.305% at 12.00[Formula: see text]noon, August 17, 2020, when the salty water flow rate was 1 L/min. The unit’s overall exergy efficiencies were 0.09%, 0.16%, 0.31%, and 0.085% when the salty water flow rates were 0.8, 0.9, 1, and 1.2 L/min, respectively. Maximum exergy destructions for the HDH unit components were 0.513, 0.156, 0.332, and 0.304[Formula: see text]kW for solar radiation, dehumidifier, humidifier, and PTSC, for a salty water flow rate of 1[Formula: see text]L/min. In contrast, the overall exergy destruction of the HDH unit was 1.3[Formula: see text]kW.
23
Aloanis, Armando Ariakta, Heindrich Taunaumang, Alfrie Rampengan, and Jeferson Polii. "ANALISIS EKSERGI DAN OPTIMASI PEMBANGKIT LISTRIK TENAGA PANAS BUMI LAHENDONG UNIT-2." Jurnal FisTa : Fisika dan Terapannya 2, no. 2 (October 31, 2021): 66–75. http://dx.doi.org/10.53682/fista.v2i2.131.
Abstract:
Geothermal development is carried out by increasing the efficiency of existing generators. In this study, geothermal development at the Lahendong Unit-2 geothermal power plant is carried out by conducting exergy analysis and optimizing geothermal plant efficiency using a genetic algorithm by adjusting the pressure on the separator. Exergy calculations and optimization of genetic algorithms, using the Python programming language with the help of libraries such as PyXSteam, Pandas, Numpy, matplotlib, random, and time. Exergy flow and efficiency are calculated on the components of the separator, turbine, condenser, cooling tower, and the entire plant. The amount of exergy that enters the generator from geothermal fluids is 28882.73 kW. The amount of exergy that comes in produces an output power of 13,000 kW with an overall efficiency of the generator is 45.010%, and the amount of exergy from brine is 1794.11 kW. Optimization using the genetic algorithm method produces the most optimal output power value of 13035,480445 kW at a separator pressure of 10.4025 bar. The increased quality of the steam generates this increase in power so that the mass flow rate of the steam that rotates the turbine becomes more than before.
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Wang, Shucheng, Pengcheng Wei, Sajid Sajid, Lei Qi, and Mei Qin. "Assessment of an integrated solar combined cycle system based on conventional and advanced exergetic methods." Thermal Science, no. 00 (2021): 325. http://dx.doi.org/10.2298/tsci210825325w.
Abstract:
An integrated solar combined cycle system based on parabolic trough solar collector and combined cycle power plant is proposed. The advanced system is socio-economic significance compared to traditional combined cycle power system. Plainly, the exergetic analyses (exergy destruction and efficiency) via conventional and advanced methods are used for thermodynamic properties of the integrated solar combined cycle system components. In addition, the exergy destruction is divided into endogenous, exogenous, avoidable, and unavoidable. The results show that the combustion chamber has the largest fuel exergy and the highest endogenous exergy destruction rate of 1001.60 MW and 213.87 MW, respectively. Additionally, the combustion chamber has the highest exergy destruction rate of 235.60 MW(60.29%), followed by the parabolic trough solar collector of 54.20 MW(13.87%). For overall system, the endogenous exergy destruction rate of 320.83 MW (82.10%) and exogenous exergy destruction rate of 69.97 MW (17.90%) are resulted via the advanced exergy analysis method. Besides?Several methods to reduce the exergy destruction and improve the components? efficiency are put forward.
25
Adesina, Kehinde Adewale, and C. Abiodun Popoola. "Exergy Rate Profile of Multicomponent Distillation System." International Journal of Recent Contributions from Engineering, Science & IT (iJES) 4, no. 2 (July 5, 2016): 29. http://dx.doi.org/10.3991/ijes.v4i2.5710.
Abstract:
Exergy rate profiles, exergetic efficiency and irreversibility were used to examine the driving forces in multicomponent distillation system with the view to identifying feasible and efficient operating parameters. The mixture used comprised of 5% propane, 15% iso-butane, 25% nbutane, 20% iso-pentane and 35% n-pentane. Operating variables were feed temperature (-30 oC and -80 oC), pressure (800 kPa and 1200 kPa), and reflux-ratio (2 and 6). Stage-by-stage system exergy analysis was estimated. Column profiles of base case -30 oC, -80 oC, -30 oC-reflus ratio 6, -80 oC reflux ratio 6 and base case reflux ratio 6 did not crossed thus are thermodynamically feasible. Base case -30 oC-reflux ratio 2, -80 oC-reflux ratio 2, and base case-reflux ratio 2 were crossed and constricted and are infeasible. Base case results gave efficiency of 81.7% at depropanizer and 65.2% at debutanizer. Base cases sensitivity results with -30 oC, -80 oC and reflux ratio 6, efficiency range 57.40 – 70% and 65.20% - 54.90% for depropanizer and debutanizer respectively. Spitted cases gave 81.7% and 62.20% with more scatter profiles. Splitted feed base case -30 oC design gave the lowest overall system exergy loss rate of 1.12E+6 and efficiency of 95.70%. Design feasible parameters, system efficiency and irreversibility which form basis
26
Ehyaei, M. A., A. Anjiridezfuli, and M. A. Rosen. "Exergetic analysis of an aircraft turbojet engine with an afterburner." Thermal Science 17, no. 4 (2013): 1181–94. http://dx.doi.org/10.2298/tsci110911043e.
Abstract:
An exergy analysis is reported of a J85-GE-21 turbojet engine and its components for two altitudes: sea level and 11,000 meters. The turbojet engine with afterburning operates on the Brayton cycle and includes six main parts: diffuser, compressor, combustion chamber, turbine, afterburner and nozzle. Aircraft data are utilized in the analysis with simulation data. The highest component exergy efficiency at sea level is observed to be for the compressor, at 96.7%, followed by the nozzle and turbine with exergy efficiencies of 93.7 and 92.3%, respectively. At both considered heights, reducing of engine intake air speed leads to a reduction in the exergy efficiencies of all engine components and overall engine. The exergy efficiency of the turbojet engine is found to decrease by 0.45% for every 1?C increase in inlet air temperature.
27
Khaliq, A., and K. Choudhary. "Combined First and Second-Law Analysis of Gas Turbine Cogeneration System With Inlet Air Cooling and Evaporative Aftercooling of the Compressor Discharge." Journal of Engineering for Gas Turbines and Power 129, no. 4 (May 1, 2007): 1004–11. http://dx.doi.org/10.1115/1.2747257.
Abstract:
A conceptual gas turbine based cogeneration cycle with compressor inlet air cooling and evaporative aftercooling of the compressor discharge is proposed to increase the cycle performance significantly and render it practically insensitive to seasonal temperature fluctuations. Combined first and second-law approach is applied for a cogeneration system having intercooled reheat regeneration in a gas turbine as well as inlet air cooling and evaporative aftercooling of the compressor discharge. Computational analysis is performed to investigate the effects of the overall pressure ratio rp, turbine inlet temperature (TIT), and ambient relative humidity φ on the exergy destruction in each component, first-law efficiency, power-to-heat ratio, and second-law efficiency of the cycle. Thermodynamic analysis indicates that exergy destruction in various components of the cogeneration cycle is significantly affected by overall pressure ratio and turbine inlet temperature, and not at all affected by the ambient relative humidity. It also indicates that the maximum exergy is destroyed during the combustion process, which represents over 60% of the total exergy destruction in the overall system. The first-law efficiency, power-to-heat ratio, and second-law efficiency of the cycle significantly vary with the change in the overall pressure ratio and turbine inlet temperature, but the change in relative humidity shows small variations in these parameters. Results clearly show that performance evaluation based on first-law analysis alone is not adequate, and hence, more meaningful evaluation must include second-law analysis. Decision makers should find the methodology contained in this paper useful in the comparison and selection of advanced combined heat and power systems.
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Guedri, Kamel, Mohamed Salem, Mamdouh El Haj Assad, Jaroon Rungamornrat, Fatimah Malek Mohsen, and Yonis M. Buswig. "PV/Thermal as Promising Technologies in Buildings: A Comprehensive Review on Exergy Analysis." Sustainability 14, no. 19 (September 27, 2022): 12298. http://dx.doi.org/10.3390/su141912298.
Abstract:
Solar Photovoltaic (PV) systems are degraded in terms of efficiency by increment in their temperature. To keep away from efficiency degradation regarding the temperature increase, various thermal management techniques have been introduced to keep the temperature low. Besides improvement in electrical efficiency, the overall efficiency can be enhanced by using the extracted thermal energy from the cell. The extracted heat in these systems, known as PV/Thermal (PV/T), can be applied for some purposes including water or air heating. This article reviews the works on the PV/T systems exergy analysis and discusses their findings. Based on the findings of the reviewed works, different factors such as the system configuration, used components and elements, and working conditions affect the exergy efficiency of these systems. As an example, use of coolants with improved thermal features, i.e., nanofluids, can cause improvement in the exergy efficiency. In addition to the nanofluid, making use of the thermal energy storage unit can further enhance the exergy efficiency. Furthermore, it has been observed that the materials of nanostructures can be another element that influences the enhancement of exergy efficiency. Moreover, the usage of some components such as glazing can lead to avoidance of thermal energy loss that would be beneficial from an exergy point of view. Finally, according to the reviewed works and knowledge of the authors, some suggestions are represented for future works in this field.
29
Baiju, V., and C. Muraleedharan. "Exergy Assessment of Single Stage Solar Adsorption Refrigeration System Using ANN." ISRN Mechanical Engineering 2012 (September 25, 2012): 1–10. http://dx.doi.org/10.5402/2012/915154.
Abstract:
A new approach based on artificial intelligence is proposed here for the exergy assessment of solar adsorption refrigeration system working with activated carbon-methanol pair. Artificial neural network model is used for the prediction of exergy destruction and exergy efficiency of each component of the system. Pressure, temperature and solar insolation are used as input variables for developing the artificial neural network model. The back propagation algorithm with three different variants such as CGP, SCG and LM are used in the network A and network B. The most suitable algorithm and the number of neurons in hidden layer are found as LM with 9 for network A and SCG with 17 for the Network B. The artificial neural network predicted results are compared with the calculated values of exergy destruction and exergy efficiency. The values of the exergy destruction and exergy efficiency of components (condenser, expansion device, evaporator, adsorbent bed, solar concentrator and overall system) are found to be close to 1. The RMS and COV values are found to be very low in all cases. The comparison of the results suggests that the artificial neural network provided results are within the acceptable range.
30
Ye, Wenlian, Zhe Yang, and Yingwen Liu. "Exergy loss analysis of the regenerator in a solar Stirling engine." Thermal Science 22, Suppl. 2 (2018): 729–37. http://dx.doi.org/10.2298/tsci170911058y.
Abstract:
In order to evaluate the irreversibility and exergy losses of the regenerators in a solar beta-type free piston Stirling engine due to flow friction, 1-D thermodynamic model to quantify exergy loss in the regenerators are built. The effects of important parameters, such as oscillating flow pressure drop, the exergy loss to flow friction, the exergy losses to conduction heat transfer at the hot and cold side of the regenerator and the percentage of Carnot efficiency of Stirling engine are presented and studied in detail. Results show that exergy loss decreases with the increase of the porosity and matrix diameter. As for the regenerator length, there is an optimum value that is equal to 0.035 m where the exergy loss is minimal and the percentage of Carnot efficiency is maximal. Therefore, some parameters should be selected reasonably to meet the overall design requirements of a solar Stirling engine.
31
Rosen, Marc A., Ibrahim Dincer, and Norman Pedinelli. "Thermodynamic Performance of Ice Thermal Energy Storage Systems." Journal of Energy Resources Technology 122, no. 4 (September 6, 2000): 205–11. http://dx.doi.org/10.1115/1.1325406.
Abstract:
The thermodynamic performance of an encapsulated ice thermal energy storage (ITES) system for cooling capacity is assessed using exergy and energy analyses. A full cycle, with charging, storing, and discharging stages, is considered. The results demonstrate how exergy analysis provides a more realistic and meaningful assessment than the more conventional energy analysis of the efficiency and performance of an ITES system. The overall energy and exergy efficiencies are 99.5 and 50.9 percent, respectively. The average exergy efficiencies for the charging, discharging, and storing periods are 86, 60, and over 99 percent, respectively, while the average energy efficiency for each of these periods exceeds 99 percent. These results indicate that energy analysis leads to misleadingly optimistic statements of ITES efficiency. The results should prove useful to engineers and designers seeking to improve and optimize ITES systems. [S0195-0738(00)00904-3]
32
Zhang, Jianyun, Zhiwei Yang, Linwei Ma, and Weidou Ni. "Exergy Analysis of Coal-Based Series Polygeneration Systems for Methanol and Electricity Co-Production." Molecules 26, no. 21 (November 4, 2021): 6673. http://dx.doi.org/10.3390/molecules26216673.
Abstract:
This paper quantifies the exergy losses of coal-based series polygeneration systems and evaluates the potential efficiency improvements that can be realized by applying advanced technologies for gasification, methanol synthesis, and combined cycle power generation. Exergy analysis identified exergy losses and their associated causes from chemical and physical processes. A new indicator was defined to evaluate the potential gain from minimizing exergy losses caused by physical processes—the degree of perfection of the system’s thermodynamic performance. The influences of a variety of advanced technical solutions on exergy improvement were analyzed and compared. It was found that the overall exergy loss of a series polygeneration system can be reduced significantly, from 57.4% to 48.9%, by applying all the advanced technologies selected. For gasification, four advanced technologies were evaluated, and the largest reduction in exergy loss (about 2.5 percentage points) was contributed by hot gas cleaning, followed by ion transport membrane technology (1.5 percentage points), slurry pre-heating (0.91 percentage points), and syngas heat recovery (0.6 percentage points). For methanol synthesis, partial shift technology reduced the overall exergy loss by about 1.4 percentage points. For power generation, using a G-class gas turbine decreased the overall exergy loss by about 1.6 percentage points.
33
Oyedepo, S. O., R. O. Fagbenle, S. S. Adefila, and Md Mahbub Alam. "Exergoeconomic analysis and performance assessment of selected gas turbine power plants." World Journal of Engineering 12, no. 3 (August 1, 2015): 283–300. http://dx.doi.org/10.1260/1708-5284.12.3.283.
Abstract:
In this study, exergoeconomic analysis and performance evaluation of selected gas turbine power plants in Nigeria were carried out. The study was conducted using operating data obtained from the power plants to determine the exergy efficiency, exergy destruction, unit cost of electricity and cost of exergy destruction of the major components of a gas turbine engine in the selected power plants. The results of exergy analysis confirmed that the combustion chamber is the most exergy destructive component compared to other cycle components as expected. The total efficiency defects and overall exergetic efficiency of the selected power plants vary from 38.64 to 69.33% and 15.66 to 30.72% respectively. The exergy analysis further shows that the exergy improvement potential of the selected plants varies from 54.04 MW to 159.88 MW. The component with the highest exergy improvement potential is the combustion chamber and its value varies from 30.21 MW to 88.86 MW. The results of exergoeconomic analysis show that the combustion chamber has the greatest cost of exergy destruction compared to other components. Increasing the gas turbine inlet temperature (GTIT), both the exergy destruction and the cost of exergy destruction of this component were found to decrease. The results of this study revealed that an increase in the GTIT of about 200 K can lead to a reduction of about 29% in the cost of exergy destruction. From exergy costing analysis, the unit cost of electricity produced in the selected power plants varies from cents 1.99 /kWh (N3.16 /kWh) to cents 5.65 /kWh (N8.98 /kWh).
34
Seyed Mahmoudi, S. M., Niloufar Sarabchi, Mortaza Yari, and Marc A. Rosen. "Exergy and Exergoeconomic Analyses of a Combined Power Producing System including a Proton Exchange Membrane Fuel Cell and an Organic Rankine Cycle." Sustainability 11, no. 12 (June 13, 2019): 3264. http://dx.doi.org/10.3390/su11123264.
Abstract:
Comprehensive exergy and exergoeconomic assessments are reported for a proposed power producing system, in which an organic Rankine cycle is employed to utilize the waste heat from the fuel cell stack. A complete mathematical model is presented for simulating the system performance while considering water management in the fuel cell. The simulation is performed for individual components of the fuel cell system, e.g., the compressor and humidifiers. A parametric study is conducted to evaluate the effects on the system’s thermodynamic and economic performance of parameters, such as the fuel cell operating pressure, current density, and turbine back pressure. The results show that an increase in the fuel cell operating pressure leads to a higher exergy efficiency and exergoeconomic factor for the overall system. In addition, it is observed that the overall exergy efficiency is 4.16% higher than the corresponding value that is obtained for the standalone fuel cell for the same value of fuel cell operating pressure. Furthermore, the results indicate that the compressor and condenser exhibit the worst exergoeconomic performance and that the exergoeconomic factor, the capital cost rate and the exergy destruction cost rate for the overall system are 40.8%, 27.21 $/h, and 39.49 $/h, respectively.
35
Rosen, M. A. "Appropriate Thermodynamic Performance Measures for Closed Systems for Thermal Energy Storage." Journal of Solar Energy Engineering 114, no. 2 (May 1, 1992): 100–105. http://dx.doi.org/10.1115/1.2929986.
Abstract:
Several definitions of energy and exergy efficiency for closed systems for thermal energy storage (TES) are developed and discussed. A simple model is utilized in which heat quantities are transferred at specified temperatures to and from a TES. Efficiency definitions are considered for the overall storage process and for the three component periods which comprise a complete storage process (charging, storing, and discharging). It is found that (1) appropriate forms for both energy and exergy efficiency definitions depend on which quantities are considered to be products and inputs; (2) different efficiency definitions are appropriate in different applications; (3) comparisons of different TES systems can only yield logical results it they are based on a common definition, regardless of whether energy or exergy quantities are considered; and (4) exergy efficiencies are generally more meaningful and illuminating than energy efficiencies for evaluating and comparing TES systems. A realistic, but simplified, illustrative example is presented. The efficiency definitions should prove useful in the development of valid and generally accepted standards for the evaluation and comparison of different TES systems.
36
Li, Chengjie, Bin Li, Junying Huang, and Changyou Li. "Energy and Exergy Analyses of a Combined Infrared Radiation-Counterflow Circulation (IRCC) Corn Dryer." Applied Sciences 10, no. 18 (September 10, 2020): 6289. http://dx.doi.org/10.3390/app10186289.
Abstract:
Energy consumption performance evaluation of an industrial grain dryer is an essential step to check its current status and to put forward suggestions for more effective operation. The present work proposed a combined IRCC dryer with drying capacity of 4.2 t/h that uses a novel drying technology. Moreover, the existing energy–exergy methodology was applied to evaluate the performance of the dryer on the basis of energy efficiency, heat loss characteristics, energy recovery, exergy flow and exegetic efficiency. The results demonstrated that the average drying rate of the present drying system was 1.1 gwater/gwet matter h. The energy efficiency of the whole drying system varied from 2.16% to 35.21% during the drying process. The overall recovered radiant energy and the average radiant exergy rate were 674,339.3 kJ and 3.54 kW, respectively. However, the average heat-loss rate of 3145.26 MJ/h indicated that measures should be put in place to improve its performance. Concerning the exergy aspect, the average exergy rate for dehydration was 462 kW and the exergy efficiency of the whole drying system ranged from 5.16% to 38.21%. Additionally, the exergy analysis of the components indicated that the combustion chamber should be primarily optimized among the whole drying system. The main conclusions of the present work may provide theoretical basis for the optimum design of the industrial drying process from the viewpoint of energetics.
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Faria, S. H. B., and R. J. Zemp. "USING EXERGY LOSS PROFILES AND ENTHALPY-TEMPERATURE PROFILES FOR THE EVALUATION OF THERMODYNAMIC EFFICIENCY IN DISTILLATION COLUMNS." Revista de Engenharia Térmica 4, no. 1 (June 30, 2005): 76. http://dx.doi.org/10.5380/reterm.v4i1.3553.
Abstract:
In this work the temperature-enthalpy profile and the exergy loss profile are used together
to improve thermodynamic efficiency of distillation columns, by identifying possible
benefits of using side exchangers. The method proposed is to compute the exergy loss
profile and to analyse the distribution of the losses across the column stages. The present
work aims at applying the stage-by-stage exergy analysis to the distillation of non-ideal
mixtures, e.g. methanol/water. For these systems the use of thermodynamic excess
properties is required: Gibbs free energy for phase equilibrium and enthalpy of solution
for energy balance. Initial studies showed that the enthalpy of solution has a small effect
on the overall energy balance of the distillation column, but a significant impact on the
exergy loss profiles. Some profiles even showed a violation of the second law of
thermodynamics, with entropy being destroyed on some stages, clearly indicating that a
wrong approach to exergy calculation was being used.A model for exergy calculations of
non-ideal solutions is presented. The exergy values so computed are then checked by a
consistency test, using the reversible column profile. Finally, the exergy procedures are
used to study a typical methanol/water distillation columns, where the exergy profiles are
used to identify scope for intermediate heat exchange.
38
Sun, Wenxu, and Zhan Liu. "Parametric Assessment on the Advanced Exergy Performance of a CO2 Energy Storage Based Trigeneration System." Applied Sciences 10, no. 23 (November 24, 2020): 8341. http://dx.doi.org/10.3390/app10238341.
Abstract:
In this paper, conventional and advanced exergy analyses are comprehensively introduced on an innovative transcritical CO2 energy storage based trigeneration system. Conventional exergy analysis can quantify in an independent way the component exergy destruction. However, the advanced technology is able to evaluate the interactions among components and identify the tangible promotion potential by allowing for the technical and economic limitations. In this method, the component exergy destruction is separated into avoidable and unavoidable parts, as well as the endogenous/exogenous parts. Calculation of the split parts is carried out by utilizing the thermodynamic cycle-based approach. Results coming from conventional exergy analysis indicate that the first three largest exergy destructions are given by cold storage, compressor 1, and heat exchanger 3. However, advanced analysis results demonstrate that the cold storage, compressor 1, and compressor 2 should be given the first improvement priority in sequence by depending on the avoidable exergy destruction. The turbine efficiency produces a higher impact on overall exergy destruction than compressor efficiency. The pinch temperature in cold storage causes the highest effect on exergy destruction amongst all the heat exchangers. There exists an optimum value in the compressor inlet pressure and ambient temperature.
39
Valencia, Guillermo, Armando Fontalvo, Yulineth Cárdenas, Jorge Duarte, and Cesar Isaza. "Energy and Exergy Analysis of Different Exhaust Waste Heat Recovery Systems for Natural Gas Engine Based on ORC." Energies 12, no. 12 (June 20, 2019): 2378. http://dx.doi.org/10.3390/en12122378.
Abstract:
Waste heat recovery (WHR) from exhaust gases in natural gas engines improves the overall conversion efficiency. The organic Rankine cycle (ORC) has emerged as a promising technology to convert medium and low-grade waste heat into mechanical power and electricity. This paper presents the energy and exergy analyses of three ORC–WHR configurations that use a coupling thermal oil circuit. A simple ORC (SORC), an ORC with a recuperator (RORC), and an ORC with double-pressure (DORC) configuration are considered; cyclohexane, toluene, and acetone are simulated as ORC working fluids. Energy and exergy thermodynamic balances are employed to evaluate each configuration performance, while the available exhaust thermal energy variation under different engine loads is determined through an experimentally validated mathematical model. In addition, the effect of evaporating pressure on the net power output, thermal efficiency increase, specific fuel consumption, overall energy conversion efficiency, and exergy destruction is also investigated. The comparative analysis of natural gas engine performance indicators integrated with ORC configurations present evidence that RORC with toluene improves the operational performance by achieving a net power output of 146.25 kW, an overall conversion efficiency of 11.58%, an ORC thermal efficiency of 28.4%, and a specific fuel consumption reduction of 7.67% at a 1482 rpm engine speed, a 120.2 L/min natural gas flow, 1.784 lambda, and 1758.77 kW of mechanical engine power.
40
Sarhaddi, Faramarz, Said Farahat, Hossein Ajam, and Amin Behzadmehr. "Exergetic Optimization of a Solar Photovoltaic Array." Journal of Thermodynamics 2009 (February 10, 2009): 1–11. http://dx.doi.org/10.1155/2009/313561.
Abstract:
An exergetic optimization is developed to determine the optimal performance and design parameters of a solar photovoltaic (PV) array. A detailed energy and exergy analysis is carried out to evaluate the electrical performance, exergy destruction components, and exergy efficiency of a typical PV array. The exergy efficiency of a PV array obtained in this paper is a function of climatic, operating, and design parameters such as ambient temperature, solar radiation intensity, PV array temperature, overall heat loss coefficient, open-circuit voltage, short-circuit current, maximum power point voltage, maximum power point current, and PV array area. A computer simulation program is also developed to estimate the electrical and operating parameters of a PV array. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, exergetic optimization has been carried out under given climatic, operating, and design parameters. The optimized values of the PV array temperature, the PV array area, and the maximum exergy efficiency have been found. Parametric studies have been also carried out.
41
Yao, Erren, Like Zhong, Yuan Zhang, Ruixiong Li, Huanran Wang, and Guang Xi. "Comprehensive performance exploration of a novel pumped-hydro based compressed air energy storage system with high energy storage density." Journal of Renewable and Sustainable Energy 14, no. 6 (November 2022): 064102. http://dx.doi.org/10.1063/5.0119831.
Abstract:
A compressed air energy storage system is the key issue to facilitating the transformation of intermittent and fluctuant renewable energy sources into stable and high-quality power. The improvement of compression/expansion efficiency during operation processes is the first challenge faced by the compressed air energy storage system. Therefore, a novel pumped-hydro based compressed air energy storage system characterized by the advantages of high energy storage density and utilization efficiency is proposed in this study. To perform a comprehensive investigation on the system, the locations and magnitudes of irreversible sources within the system are estimated through the conventional exergy method, and the interactions among components and realistic potential for system performance improvement are identified by the advanced exergy method. The results indicate that the interactions among components are complex but not very significant since the endogenous exergy destruction is larger than the exogenous exergy destruction for all components within the system. Furthermore, the conventional exergy analysis reveals that the expander, compressor1, and pump are the most important components, accounting for 25.99%, 22.55%, and 15.34% of the total exergy destruction, respectively. Nevertheless, advanced exergy analysis recommends that the hydraulic turbine, pump, and expander have the optimization priorities since they share 28.61%, 27.72%, and 10.07% of the total endogenous avoidable exergy destruction. Finally, the overall system exergetic efficiency achieves a higher value of 18.49% under unavoidable conditions than that under real conditions.
42
Rezaie, Behnaz, Bale V. Reddy, and Marc A. Rosen. "Exergy Assessment of a Solar-Assisted District Energy System." Open Fuels & Energy Science Journal 11, no. 1 (March 30, 2018): 30–43. http://dx.doi.org/10.2174/1876973x01811010030.
Abstract:
Background:District Energy (DE) is a technology capable of using renewable energy (e.g., solar thermal systems) and waste heat as energy sources efficiently. DE technology nonetheless has potential for improvement. Thermal Energy Storage (TES) can enhance DE performance significantly.Objective:An exergy analysis of a DE system which includes a solar thermal energy system and TES is performed, so as to improve understanding of its performance.Method:A case study based on the Friedrichshafen DE system in Germany is used to assess thermodynamically the role of solar energy and TES in a DE system. The system performance is separated into three modes: (1) fossil fuel is the only source of energy, (2) a discharging TES and fossil fuel provide heat for the DE system, and (3) solar energy and fossil fuels are the energy supplies. Exergy analyses are conducted for each performance mode and the overall DE system.Results:The results quantify the benefits of incorporating solar energy and TES on the performance of the Friedrichshafen DE system, and demonstrate that the overall exergy efficiency of the DE system increases from 23% to 27% with assistance of solar thermal collectors and TES, while the total energy efficiency increases from 83% to 87%.Conclusion:An increase of exergy efficiency is observed when TES is added to a DE system, due to a reduction in solar thermal energy loss by the TES, which allows more solar energy to be converted to useful energy to satisfy the DE system thermal energy demand.
43
Arsana, Made Ery, I. Gusti Bagus Wijaya Kusuma, Made Sucipta, and I. Nyoman Suamir. "Exergy and Energy Analyses of Dual-Temperature Evaporator Split AC System Incorporated A Capillary Tube and A Two-Phase Ejector." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 77, no. 1 (November 7, 2020): 88–99. http://dx.doi.org/10.37934/arfmts.77.1.8899.
Abstract:
This study was aimed to investigate performance of a split type air conditioning (SAC) system applying exergy destruction method. A numerical model was established based on exergy destruction analysis of a Condenser Outlet Split-Split Air Conditioning (COS-SAC) system integrated with dual-temperature evaporator and incorporated capillary tube and ejector as expansion devices. An experimental test system was also established to experimentally validate the model. Two type of refrigerants R-290 and R-22 were involved in the evaluations. The Coefficient of Performance (COP) of the ejector COS-SAC system, exergy destruction, and exergy efficiency were determined and compared with those in the SAC system utilizing capillary tube. The results showed there was a significant improvement in the overall exergy efficiency of the COS-SAC systems. The COP of the COS-SAC system was also found to be better than the COP of the SAC system.
44
GÜNGÖR ÇELİK, Ayşegül. "Advanced Exergy Assessment of an Air Source Heat Pump Unit." Bitlis Eren Üniversitesi Fen Bilimleri Dergisi 13, no. 1 (December 25, 2023): 15–22. http://dx.doi.org/10.17798/bitlisfen.1308933.
Abstract:
Conventional exergy-based analysis methods are used for evaluating the performance of the energy conversation systems. Conventional exergy-based analyses identify the sources, amounts, and reasons of irreversibilities (exergy destructions), costs and environmental effects, and provide a general direction for improvement. However, interactions between system components (endogenous/exogenous) and technical limitations (avoidable/unavoidable) cannot be identified with any conventional analysis. Hence, the real potential for improvement and optimization strategies can be misguided. Advanced exergy based analysis seeks to overcome this limitation. An air source heat pump unit was assessed applying conventional and advanced exergy analysis approaches respectively. Avoidable/unavoidable and endogenous/exogenous exergy destructions, modified exergy efficiencies and modified exergy losses ratios were calculated for every single component of the system. The results showed that while the evaporator and condenser efficiencies could be upgraded via constructional enhancements to the overall system and other system components, internal operating conditions were mainly responsible of the inefficiencies regarding with the compressor. The analysis demonstrated that while it was possible to improve evaporator and condenser efficiency by making constructive enhancements to whole system design, the efficiency of the compressor was mainly determined by the internal conditions in which the compressor operated.
45
Agberegha, Larry Orobome, Peter Alenoghena Aigba, Solomon Chuka Nwigbo, Francis Onoroh, Olusegun David Samuel, Tanko Bako, Oguzhan Der, Ali Ercetin, and Ramazan Sener. "Investigation of a Hybridized Cascade Trigeneration Cycle Combined with a District Heating and Air Conditioning System Using Vapour Absorption Refrigeration Cooling: Energy and Exergy Assessments." Energies 17, no. 6 (March 7, 2024): 1295. http://dx.doi.org/10.3390/en17061295.
Abstract:
The insufficiency of energy supply and availability remains a significant global energy challenge. This work proposes a novel approach to addressing global energy challenges by testing the supercritical property and conversion of low-temperature thermal heat into useful energy. It introduces a combined-cascade steam-to-steam trigeneration cycle integrated with vapour absorption refrigeration (VAR) and district heating systems. Energetic and exergetic techniques were applied to assess irreversibility and exergetic destruction. At a gas turbine power of 26.1 MW, energy and exergy efficiencies of 76.68% and 37.71% were achieved, respectively, while producing 17.98 MW of electricity from the steam-to-steam driven cascaded topping and bottoming plants. The cascaded plant attained an energetic efficiency of 38.45% and an exergy efficiency of 56.19%. The overall cycle efficiencies were 85.05% (energy) and 77.99% (exergy). More than 50% of the plant’s lost energy came from the combustion chamber of the gas turbine. The trigeneration system incorporated a binary NH3–H2O VAR system, emphasizing its significance in low-temperature energy systems. The VAR system achieved a cycle exergetic efficiency of 92.25% at a cooling capacity of 2.07 MW, utilizing recovered waste heat at 88 °C for district hot water. The recovered heat minimizes overall exergy destruction, enhancing thermal plant performance.
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Rakhesh, B., G. Venkatarathnam, and S. Srinivasa Murthy. "Experimental Studies on a Heat Pump Operating With R22, R407C and R407A: Comparison From an Exergy Point of View." Journal of Energy Resources Technology 125, no. 2 (June 1, 2003): 101–12. http://dx.doi.org/10.1115/1.1538631.
Abstract:
Experiments are conducted on a heat pump with refrigerants R22, R407C and R407A. The performance is compared in terms of coefficient of performance, heating/cooling capacities, and exergy efficiency of the overall system. The results are analyzed from an exergy point of view to bring out the conditions under which the performance is maximum.
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Zhang, Yeqiang, Biao Lei, Zubair Masaud, Muhammad Imran, Yuting Wu, Jinping Liu, Xiaoding Qin, and Hafiz Ali Muhammad. "Waste Heat Recovery from Diesel Engine Exhaust Using a Single-Screw Expander Organic Rankine Cycle System: Experimental Investigation of Exergy Destruction." Energies 13, no. 22 (November 12, 2020): 5914. http://dx.doi.org/10.3390/en13225914.
Abstract:
The organic Rankine cycle is a mature small-scale power generation technology for harnessing low- to mid-temperature heat sources. However, the low efficiency of the cycle still hinders its widespread implementation. To optimize the cycle’s performance, it is crucial to identify the source and magnitude of losses within each component of the cycle. This study, thus, aims to investigate the irreversible losses and their effect on the performance of the system. A prototype organic Rankine cycle (ORC) with the exhaust of a diesel engine as the heat source was developed to experimentally investigate the system and ascertain the losses. The experiments were performed at steady-state conditions at different evaporation pressures from 1300 kPa to 1600 kPa. The exergy loss and exergetic efficiency of the individual component and the overall system was estimated from the experimentally measurement of the pressure, temperature, and mass flow rate. The results indicate that the exergy losses of the evaporator are almost 60 kW at different evaporation pressures and the exergy loss rate is from 69.1% to 65.1%, which accounted for most of the total exergy loss rate in the organic Rankine cycle system. Meanwhile, the highest shaft efficiency and exergetic efficiency of the screw expander are 49.8% and 38.4%, respectively, and the exergy losses and exergy loss rate of the pump and pipe are less than 0.5 kW and 1%. Due to the relatively higher exergy loss of the evaporator and the low efficiency of expander, the highest exergetic efficiency of the organic Rankine cycle system is about 10.8%. The study concludes that the maximum improvement potential lies in the evaporator, followed by the expander.
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Hanif Mat Muhammad, Mohd, Aman Mohd Ihsan Mamat, and Wan Saiful-islam Wan Salim. "Exergy Analysis of Organic Rankine Cycle and Electric Turbo Compounding for Waste Heat Recovery." International Journal of Engineering & Technology 7, no. 3.11 (July 21, 2018): 152. http://dx.doi.org/10.14419/ijet.v7i3.11.15951.
Abstract:
With such tough legislation on current emission standards, car manufacturers are focusing on increasing the efficiency of their engines with the development of advance waste heat recover (WHR) technology. Organic Rankine Cycle (ORC) and Electric Turbo Compounding (ETC) system have a good potential to be used as exhaust energy recovery. This paper compares the exergy availability and losses between the ORC and the ETC. In this particular study, exhaust data from the Proton 1.6L CamPro CFE turbocharged engine was used. This particular engine already has a main turbocharger, making the added WHR as a secondary recovery system to further increase the engine efficiency. Both systems are coupled to a 1 kW electric generator for ease of comparisons. At first the available exergy is calculated for both WHR technologies. Exergy losses from rotating the generator are analysed to finally determine the thermal efficiency of the overall system. Exergy calculation is simplified to only account for chemical and physical exergy since kinetic and potential energy are negligible in comparison. Available exergy for ORC was significantly high which went up to 12.5 kW with the exergy losses recorded at 9.7 kW. The ETC achieved only 5 kW but had a small loss at 8x10-3 kW. Average thermal efficiency of the ORC systems was 10.7% compared to ETC which was 58.7%. It can be concluded that the complexity of the ORC system contributes to its downfall where multiple components increase its exergy losses compared to the simplistic design of an ETC.
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Geetha, R., M. M. Vijayalakshmi, and E. Natarajan. "Modeling and Simulation Assessment of Solar Photovoltaic/Thermal Hybrid Liquid System Using TRNSYS." Applied Mechanics and Materials 813-814 (November 2015): 700–706. http://dx.doi.org/10.4028/www.scientific.net/amm.813-814.700.
Abstract:
The PV/T hybrid system is a combined system consisting of PV panel behind which heat exchanger with fins are embedded. The PV/T system consists of PV panels with a battery bank, inverter etc., and the thermal system consists of a hot water storage tank, pump and differential thermostats. In the present work, the modeling and simulation of a Solar Photovoltaic/Thermal (PV/T) hybrid system is carried out for 5 kWp using TRNSYS for electrical energy and thermal energy for domestic hot water applications. The prominent parameters used for determining the electrical efficiency, thermal efficiency, overall thermal efficiency, electrical thermal efficiency and exergy efficiency are the solar radiation, voltage, current, ambient temperature, mass flow rate of water, area of the PV module etc. The simulated results of the Solar PV/T hybrid system are analyzed for the optimum water flow rate of 25 kg/hr. The electrical efficiency, thermal efficiency, overall thermal efficiency, equivalent thermal efficiency, exergy efficiency are found to be 10%, 34%, 60%, 35% and 13% respectively. The average tank temperature is found to be 50°C.
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Mibarki, Nawel, Zakaria Triki, Abd-Elmouneïm Belhadj, Hichem Tahraoui, Abdeltif Amrane, Sabrina Cheikh, Amina Hadadi, et al. "Energy and Exergy Analysis of Solar Air Gap Membrane Distillation System for Seawater Desalination." Water 15, no. 6 (March 20, 2023): 1201. http://dx.doi.org/10.3390/w15061201.
Abstract:
Air gap membrane distillation (AGMD) is a widely utilized technology for producing drinking water due to its low heat loss, high thermal efficiency, and compatibility with solar energy. The application of the first and second laws of thermodynamics in energy and exergy analyses provides a comprehensive evaluation of the efficiency of thermal processes. This study aims to examine numerically the energy and exergy performance indicators of a solar AGMD system used for seawater desalination. The simulation was carried out using MATLAB 9.7 software. The total thermal efficiency and overall efficiency of each element in the AGMD system were calculated for various solar field energy outputs, and moreover, a parametric study was conducted. The results indicate that the exergetic efficiency of the AGMD system components was the lowest in the solar field, with the concentrator having the lowest energy efficiency. Additionally, the thermal and exergetic efficiency of the entire solar AGMD system decreases along with the raise of ambient temperature. An additional investigation was conducted to better apprehend the sources of exergy destruction in the solar field. The obtained results from this study can be employed as a guide to reduce exergy destruction in the whole solar AGMD desalination system with recognition of the main sources of irreversibility.