Forthcoming articles

International Journal of Exergy

International Journal of Exergy (IJEX)

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International Journal of Exergy (45 papers in press)

Regular Issues

  • ASSESSMENT AND APPLY OF AN ENHANCED EXERGY ANALYSIS FOR AN ARGON LIQUEFACTION SYSTEM   Order a copy of this article
    by Arif Karabuga 
    Abstract: Argon is one of the three basic elements in the air and is obtained by separating the air. It can be stored in liquid form using different liquefaction methods. Its basically and widely liquefied by three different liquefaction methods such as cryogenic, pressure swing adsorption and membrane. The main difference between these three methods is that the purity rates of the products obtained are different. The cryogenic method with the highest purity rate constitutes the method of this study. In the present work, conventional and enhanced exergy analyses were applied to the liquefaction process of argon gas. In the conventional exergy analysis, only the exergy efficiency and exergy destruction rate of the components are calculated. For the process improvement, more detail data about the origin of the destructions and effect of the components mutual on the exergy destructions would be required. In the enhanced exergy analysis, splitting the exergy destruction into endogenous/exogenous and avoidable/unavoidable parts represents a new direction. In the study, forward exergy analysis is performed for each component and endogenous, exogenous, unavoidable and avoidable values of these components were calculated. When the convectional exergy analysis is examined, the exergy efficiency of the argon gas liquefaction system is calculated as 51.77 %. When the enhanced exergy analysis of the system is examined, it is found that the highest exergy destruction occurred in the turbine as 614.3 kW. Furthermore, the highest endogenous exergy degradation was found as 494 kW (%80.4) in the turbine.
    Keywords: Enhanced exergy analysis; Liquefaction system; Argon; Cryogenic; Exergy.

  • Thermodynamic analysis and optimization of double effect absorption type combined power and cooling cycle using LiBr-water as working fluid   Order a copy of this article
    by Rahul Patil, Sunil Bhagwat 
    Abstract: In this work, the mathematical model and simulation of the series and parallel flow Double effect absorption type combined power and cooling cycle (DACPC) has been done in Scilab (open source software) using highly accurate thermodynamic correlations available in the literature. Sensitivity analysis of the operating parameters of a cycle has been studied and it has been optimized using Scilab's inbuilt function "optim" to get maximum exergy efficiency for given evaporator and absorber temperature. The DACPC has been compared with other combined power and cooling cycle from the literature and found that its exergy efficiency is significantly more by 7-41 %. The data of optimized operating conditions is generated and it will be useful for designing the cycle for practical applications. The maximum exergy efficiency of DACPC is in a range of 60 % to 65 %.
    Keywords: Absorption; combined power and cooling; LiBr-water; Exergy; optimization.

  • FRACTION OF THE METABOLIC AGEING ENTROPY DAMAGE TO A HOST MAY BE FLUSHED OUT BY GUT MICROBIATA   Order a copy of this article
    by Mustafa Özilgen, Cennet Yildiz, Bayram Yilmaz 
    Abstract: Entropic age concept suggests that, in the long-term, metabolic heat damages the living systems and causes ageing. Human host, plus millions of microorganisms living in and on it are called the human superorganism. Gut microbiota acts as an autonomous thermodynamic subsystem in the human superorganism, generate and export its own entropy without causing ageing damage to the host. Thermodynamic analyses are performed to quantify entropy generation by the host and the gut microbiota subsystems, and it is found that 12% to 59% of the metabolic entropy of the human superorganism is generated by the gut microbiota and exported with feces, without contributing to the ageing of the host. Although gut microbiota was used to be studied traditionally only for their nutritional benefits to the host, this is a newly hypothesized benefit and needs to be studied further.
    Keywords: Gut microbiota; human superorganism; Schöridinger’s theory; Prigogine’s theory; entropic age; exporting entropy; feces.

  • Energy and Exergy Analyses of an Ignition Engine with Improved Management System Codes   Order a copy of this article
    by Ayyub Fekari, Nader Javani, Samad Jafarmadar 
    Abstract: In this study, an ignition engine is investigated by using three different codes for its management system to obtain the best performance in terms of engine exhaust emissions. The effect of improved engine management system on the energy and exergy efficiencies are investigated. Two different tests in the idle (850-900 rpm) and mid-range (2500 rpm) modes are conducted. According to the results, a reduction in the exhaust emissions can be obtained while the energy efficiencies increase 1.23% both in idle and medium speeds. Meanwhile, the exergy efficiency increases by 4.76% and 0.7% in the idle speed and mid-ranges, respectively through improving the codes of the engine management system. The amount of unburned hydrocarbons, carbon monoxide, and NOx decreases 22.4%, 31%, and 1.4%, respectively, in the idle speed. Similarly, 23.3%, 5.3%, and 18.8% decrease is observed for the same gases in the medium speed, respectively. Brake-specific fuel consumption (BSFC) reduces 1.4% in idle speed and 1.2% in medium speed for the optimum mode in the experiments. The corresponding improved codes based on the conducted experiments in different operating conditions can be assumed as an optimal model for the considered engine.
    Keywords: Exergy efficiency; Energy efficiency; Brake specific fuel consumption; Brake power output.

  • EFFECT OF DIETHYL-ETHER ON EMISSION AND EXERGY ANALYSIS OF NEEM-OIL BASED BIODIESEL FUELED DIESEL ENGINE   Order a copy of this article
    by Veena Chaudhary 
    Abstract: This investigation presents the impact of Diethyl-Ether (DEE) on exergy parameters, and emission concentrations for NEEM45 fueled small DI diesel engine. Diethyl-Ether has been used as an oxygenated improver. DEE is mixed in NEEM45 (neem biodiesel45% +55% diesel) in proportions of 5%, 10%, and 15% by vol% basis. The impact of DEE on exergy analysis of diesel engine has been carried out in this investigation. Engine out emissions, namely NOx, CO, HC, and smoke opacity, are measured. Experimental results indicate a significant decline in NOx,CO and improved exergetic efficiency. The exergetic efficiency is increased by 6.8%, which indicates the lower exergy destruction. NOx emission significantly reduced by 56% as compared to that of NEEM45 without DEE.The experimental results show that exergy parameters and emission characteristics improved with 15% DEE addition.
    Keywords: Diethyl ether; Exergy destruction; Exergetic efficiency; Exergy distribution; Neem biodiesel; NOx emission; Smoke opacity.

  • Analysis of the viability of the 2x250 MWth HTR-PM project for the hydrogen production by the high temperature electrolysis and the Cu-Cl cycle   Order a copy of this article
    by Daniel González Rodríguez, Fernado Roberto De Andrade Lima, Carlos Alberto Brayner De Oliveira Lira, Carlos Rafael García Hernández 
    Abstract: The work describes two proposals for hydrogen production using the HTR-PM reactor as an energy source. The HTR-PM is a small modular nuclear reactor (SMR) partially based on the HTR-10 project. Both proposals take advantage of the high output temperatures of the 2x250 MWth HTR-PM reactor project to increase the efficiency of hydrogen production processes. Two proposals are analyzed, the hydrogen production through the Cu-Cl cycle and the high temperature electrolysis process. To evaluate the efficiency of the proposed conceptual designs, two computational models were developed in a chemical process simulator. For each of the proposed systems, an exergy analysis was carried out to determine the main operating parameters in each case. A determination of the efficiency of the hydrogen production process coupled to the HTR-PM is carried out using the computational model developed. The High Temperature Electrolysis process (HTE) can produce 0.7821 kg/s of hydrogen with 27.37 % of efficiency. For this process, the solid oxide electrolyzer cell is the component with the highest value of the exergy destruction rate. The Cu-Cl process, although producing less hydrogen, 0.5637 kg/s, has higher overall efficiency (32.12 %) than the HTE, mainly due to less global exergy destruction and higher exergetic efficiency.
    Keywords: nuclear hydrogen production; Cu-Cl cycle; high temperature electrolysis;\r\nefficiency; exergy.

  • PERFORMANCE ASSESSMENT OF NANOSTRUCTURED THERMOELECTRIC COOLER   Order a copy of this article
    by Mustafa Asker 
    Abstract: In this research study, 1D numerical simulation for p-type (Bi0.2Sb0.8)2Te3 nanocomposite thermoelectric cooler (TEC) is conducted by utilizing a finite volume method. The model is verified through a comparison with the published analytical data and good agreement is observed. Multiwall carbon nanotube (MWCNT) is used to enhance the thermal characteristics of TEC which is represented by the figure of merit. In this context, three separate scenarios are developed for different MWCNT compositions in order to investigate the influence of various design parameters on the performance of TEC. Also, a parametric study is carried out to analyze the effect of operating conditions such as temperature difference (?T) and current (I) on the performance of TEC in terms of cooling capacity and coefficient of performance (COP). The effect of a geometric parameter such as leg length of the nanostructured TEC has been examined. It is found that the most efficient performance is achieved for nanocomposite containing 0.12 wt% of MWCNT with a figure of merit equal to 1.4. Moreover, the maximum value of exergy efficiency for this nanocomposite is found to be 0.195 at a current value of 0.7A. In addition, an increase in the length of nanostructured TEC leads to decline in exergy of cooling capacity by 0.56 and in exery efficiency by 0.87.
    Keywords: Coefficient of performance; exergy efficiency; finite volume method; thermoelectric cooler.

  • Energy and Exergy analyses of Flat Plate Solar Collectors with nanofluids containing different size and shape of nanoparticles   Order a copy of this article
    by Mohammed Ayaz Uddin, Ahmet Sahin, Bekir S. Yilbas, Abdullah Al-Sharafi 
    Abstract: The effect of nanoparticle size, shape, and volume concentration upon the flat plate solar collector (FPSC) performance is investigated. The enhancement in efficiency due to volume concentration SiO2/H2O nanofluid was significant whereas the enhancement due to size and shape was marginal. In addition, the paper discusses the effect of the concentration, size and shape of nanoparticles upon the pressure drop, pumping power, exergy destruction and entropy generation. The exergy efficiency is found to increase upon increasing the nanoparticle size and volume concentration. However, the effect due to shape variation on the exergy efficiency is minimal.
    Keywords: Collector Efficiency; Entropy Generation; Exergy Destructed; Exergy efficiency; Flat Plate Solar Collector; Nanofluid; Nanoparticle Shape; Nanoparticle Size; Pressure Drop; Pumping Power; Thermophysical Properties.

  • GIS-Based Maritime Spatial Planning for Site Selection of Offshore Wind Farms with Exergy Efficiency Analysis: A Case Study   Order a copy of this article
    by Arife Tugsan Isiacik Colak, Gizem Senel, Cigdem Goksel 
    Abstract: Maritime Spatial Planning (MSP) is a mechanism of supporting adaptive decision-making in response to possible conflicts over offshore wind turbine locations. Offshore wind power has recently started to become an essential factor by beginning to control the use of ocean space. This study aims to show a c GIS-based site-selection with multi-criteria decision analysis for offshore wind farms while taking into account energy and exergy efficiency analyses of the selected model wind turbine. The Analytic Hierarchy Process (AHP) was used to identify potential sites dependent on several critical physical parameters. The first phase of the study is the data collection, which involves the construction of a Geographic Information System (GIS). The second phase is the exclusion step. In the final stage, energy and exergy efficiencies of the wind energy generating system have been investigated. Meteorological parameters are examined on exergy and energy efficiency, and results are shown. The most significant result achieved from this study is that Bozcada has potential sites for installing offshore wind turbines by means of meteorological parameters and suitable location.
    Keywords: Offshore Wind Farm; MSP; Wind Turbine; Energy Efficiency; Exergy Efficiency.

  • Microphysical analysis for peristaltic flow of SWCNT and MWCNT carbon nanotubes inside a catheterised artery having thrombus: Irreversibility effects with Entropy   Order a copy of this article
    by Anber Saleem, Salman Akhtar, Sohail Nadeem, Mehdi Ghalambaz 
    Abstract: The blood flow with carbon nanotubes, examining study case of both single and multi-wall carbon nanotubes, is mathematically interpreted. The blood vessel has a sinusoidally fluctuating outer wall and a thrombus is placed at the centre. The restriction to flow is improved by application of a catheter. Entropy is also examined to interpret the irreversibility results. The final results are explained with graphs for exactly obtained mathematical solutions. Streamlines are drawn and they clearly show sinusoidally fluctuating wall on one side and a thrombus on the other side at the centre.
    Keywords: Peristaltic flow; Catheterized artery; thrombus; Carbon nanotubes; entropy.

  • Application of the data validation and reconciliation method in exergy analysis of technological processes   Order a copy of this article
    by Bozena Boryczko, Adam Holda, Michal Dudek, Zygmunt Kolenda 
    Abstract: One of the main tasks of exergy analysis of real physical and chemical processes is to detect, quantify and calculate exergy losses which occur as the results of thermodynamic imperfection or irreversibilities of every process taking place inside the system. Exergy does not satisfy the law of conservation so the exergy balance is always closed by internal exergy losses which are directly proportional to the entropy generation rate. Exergy balance equations contain directly measurable variables which characterize the mass flow rates, the chemical compositions and specific exergy of substances and products calculated from material and energy balance equations (laws of conservation of mass and energy). These laws - when applied to the principal chemical elements and energy lead to the system of nonlinear algebraic equations. Usually, the number of balance equations is greater than the number of unknowns (not directly measured quantities) and because of inevitable errors of measurements the system of equations is not exactly satisfied. The measured variables must be corrected to satisfy the required equations. Such a correction is called data validation and reconciliation (also known in literature as adjustment of material mass and energy balances.) It is obvious that exergy balance equations must be based on the adjusted mass and energy balances in order to be reliable. Neglecting this process can lead to incorrect values of exergy losses, both internal and external. Thus, the general aim of this paper is the analysis of the influence of the measurement results (mass flow rates, chemical composition) on the accuracy of exergy loss calculation. It results from the general requirement of minimization of exergy losses or maximization of thermodynamic efficiency of the process. From the calculation of entropy generation rate, it can be seen that the disagreement with results based on direct measurement results is contained within a 2-5 % interval.
    Keywords: data reconciliation; model validation; least squares method; mass; energy and exergy balances; entropy generation.

  • Exergy efficiency design for multi-stream plate-fin heat exchangers based on entropy generation assessment   Order a copy of this article
    by Jinghua XU 
    Abstract: This paper presents an exergy efficiency design method for multi-stream plate-fin heat exchangers (MPFHE) based on entropy generation assessment (EGA). Dialectically, there are mutually restrictive influencing factors on efficiency and effectiveness of MPFHE widely used in industry, for instance, cryogenic air separation unit (ASU), Integrated Gasification Combined Cycle (IGCC), liquefied natural gas (LNG) plants, and even semiconductor and advanced chip manufacturing, etc. Firstly, the fundamental concepts of energy, entropy and exergy are introduced. Furthermore, the state corresponding to the designated exergy is creatively defined as the referential assessment state. The potential higher and lower status relative to the referential assessment state are traversed and reckoned to determine the optimal rigorous operation decisions with enough redundancy under variable operating conditions. The multi-objective optimization (MOO) via referential assessment state is built. Taking the ubiquitous Plate-Fin Heat Exchanger (PFHE) as research object, the thermal equilibriums equations are built to calculate equilibrium temperature of each stream in all the passages via Partial Differential Equations (PDEs). The different types of lateral perforated fins and wavy fins are designed to obtain the larger heat transfer coefficient and smaller friction coefficient using multi-physics field synergy computational fluid dynamics (CFD). The changing trend of parameters, for instance, temperature, T-Q diagram, entropy generation, dimensionless entropy generation, exergy loss and exergy efficiency in either stream or system hierarchy are observed to mine the adjustable parameter portfolio. The proposed EGA method is verified by physical experiment concerning heat transfer and flow resistance which involves diverse innovative technologies under different Reynolds number using Particle Image Velocimetry (PIV). The results prove that, the net cost of MPFHE is reduced from 20813 $/kW to 19072 $/kW after using EGA, with absolute change ratio of 8.36%, while keeping the stability of exergy efficiency. The proposed design method provides the rational tradeoff between benefits and costs, therefore, it has important implications for high-efficiency energy utilization and operating economical assessment in heat exchange fields.
    Keywords: Exergy efficiency design; Entropy generation assessment (EGA); Multi-stream plate-fin heat Exchangers (MPFHE); T-Q diagram; exergoeconomic analysis.

  • Techno-economic analysis of power generation by turboexpanders in natural gas pressure reduction stations   Order a copy of this article
    by Bijan Hejazi, Ahmad Rafiee 
    Abstract: The objective of this paper is to perform a techno-economic feasibility study of recovering pressure energy of natural gas stream through installing turboexpanders in a pressure reduction station and selling the generated electrical power to the national grid. As a case study, the operating and real conditions of a major pressure reduction station in Iran is collected throughout the years 2015, 2016 and 2017. To account for the effects of the inherently variable operating conditions, a thermodynamic model based on exergy analysis estimates off-design turboexpander isentropic efficiency, size and cost estimate as well as minimum preheating temperature required to avoid hydrate formation due to the expansion process. The detailed economic analysis shows that for the project to be economically feasible, an electricity purchase price of >$0.08/kWh is required. Furthermore, the results of this study are useful for designing automatic preheating temperature control system.
    Keywords: natural gas; pressure reduction station; exergy recovery; turboexpander; variable operating conditions; computer-aided process design.

  • Energy and Exergy Optimization of Parallel Flow Direct and Indirect Fired Triple Effect Vapour Absorption Systems   Order a copy of this article
    by Md Azhar, M. Altamush Siddiqui 
    Abstract: In this study, optimization of operating parameters (generator temperatures, concentrations, and solution distribution ratios) have been performed to achieve maximum thermodynamic performance and minimum energy consumption in the parallel flow triple effect direct and indirect-fired vapour absorption refrigeration systems. Energy and exergy analyses are considered for the formation of the objective function to optimize the above operating parameters. Moreover, comparison of performance parameters have been shown with parallel flow double effect, series flow double effect, and series flow triple effect cycles. After optimization of triple effect parallel flow cycles, results show that coefficient of performance of both triple effect direct and indirect fired cycles are same. While exergy performance of direct fired cycle is around 70 to 80% lower than indirect fired cycle. Moreover, COP of parallel flow triple effect cycle is 7 to 10% higher than its series flow configuration. Also, flow rate of gaseous fuels of parallel flow triple effect cycle require 5% lesser as compared to series flow. Moreover, exergy performance of parallel cycles was found to be around 9-11% better than series flow cycles, but at the expense of 5-10% higher inlet temperature of the main generator.
    Keywords: Triple Effect; Absorption system; Parallel flow Cycle; Optimization; Direct Fired; Indirect Fired; Exergy Analysis.

  • Nutrition and disease-related entropy generation in cancer   Order a copy of this article
    by Mustafa Özilgen, Melek Ece Öngel, Cennet Yildiz, Bayram Yilmaz 
    Abstract: Lifespan entropy generation limit concept suggests that the living beings die after generating a definite amount of life span entropy, since their bodies cannot tolerate accumulating more damage. A healthy person, who has a lifespan of 78.6 years may generate 11,404 kJ/kg K of nutrition-related lifespan entropy. If that person should be diagnosed with cancer at the age of 40, he/she would have already generated 5,803 kJ/kg K of nutrition-related entropy and may generate 5,593 kJ/kg K of more entropy until dying. After the onset of the disease, approximately 97 kJ/kg K of entropy may be generated via nutrition-related metabolic activity in five years. In lung cancer, disease-related entropy generation is 191 folds of that of the diet-related entropy generation and this is 9 folds in skin cancer. This study points that, very high fraction of the lifespan entropy generated by the cancer patients is fueled not by diet, but by tissue-scavenging, slowing down the scavenging-related chemical activity may actually increase the lifespan of the patients.
    Keywords: Cancer patients; Tissue-scavenging; Entropic-age; Nutrition-related entropy generation; Disease-related entropy generation.

  • Sensitivity analysis of N identical evacuated tubular collectors integrated double slope solar distiller unit by incorporating the effect of exergy   Order a copy of this article
    by Desh Bandhu Singh 
    Abstract: This paper focuses on the sensitivity analysis of N alike evacuated tubular collectors integrated double slope solar distiller unit (NETCDS) using computational programme in MATLAB considering typical day of May of New Delhi climatic situation. The one-at-a-time technique (OAT) has been used for the analysis and it has been concluded that potable water yield is most sensitive with respect to number of collectors followed by water depth and mass flow rate. The average value of sensitivity figure for potable water yield as well as daily exergy output with respect to number of collectors has been found to be 0.68 and 1.4 respectively.
    Keywords: sensitivity analysis; ETC; double slope solar still; exergy.

  • Energetic and exergetic analyses of a solar powered combined compression-absorption refrigeration system   Order a copy of this article
    by Abdul Khaliq, Mathkar Alharthi, Saeed Alqaed 
    Abstract: This communication presents a theoretical framework for the thermodynamic analysis of a combined system which can simultaneously produce cooling for both refrigeration (-50C) and air conditioning (100C) for the hot climatic regions in an eco-friendly and carbon free manner. A tower solar collector unit was employed to drive the proposed combined cooling system consists of a hydrocarbon operated vapour compression refrigeration system which is fed by power from steam turbine shaft, and a waste heat operated single-effect LiBr-H2O operated absorption chiller. A mathematical model using the balances of energy and exergy over the components of the system was developed, and solved using Engineering Equation Solver software. A parametric analysis was conducted to estimate the influence of operating conditions on the system performance. The results show that at base line operation of the system for R600a operated VCR, the energetic efficiency of combined system was found to be 73.66% and the exergetic efficiency of 36.43% while for R290 operated VCR, the energetic and exergetic efficiencies of the combined system were found to be 37.17% and 21.04%, respectively.
    Keywords: Tower solar collector; Steam Rankine cycle; Hydrocarbon operated vapour compression cycle; LiBr-H2O operated absorption chiller; Exergy.

  • Energy and Exergy Analysis of an Industrial Corn Dryer Operated by Two Different Fuels   Order a copy of this article
    by Fatih Ünal 
    Abstract: Drying processes are among the most energy-consuming operations in industrial plants. Therefore, it is highly beneficial for drying facilities to have high energy efficiency and low emission values to the environment. Accordingly, in this study, the data obtained after converting an industrial horizontal type corn dryer that meets its drying air temperature from coal to natural gas was compared by thermodynamic analyses. Before starting the drying process, it was assumed that the corn type DKC6050 with 24-25% corn inlet humidity dries when it reaches approximately 14% corn outlet humidity, which is the storage condition after the drying process. Energy and exergy efficiencies, drying rates, unit drying costs, specific moisture extraction rate, and specific energy consumption values of the analyzed systems were determined using the data obtained from the experiments carried out at 90,100 and 110
    Keywords: drying; industrial drying; corn drying; energy analysis; exergy analysis; unit drying cost.

  • Experimental energetic and exergetic analysis with the novel emulsion fuels incorporating CNT and Al2O3 nano additive for DICI engine   Order a copy of this article
    by Ranjeet Rai, Rashmi Sahoo 
    Abstract: Experimental investigation on the energy, sustainability, and exergy based analysis have been performed for the 5% water in diesel emulsion (WiDE) fuel, 50ppm carbon nano tube (CNT) and 50ppm aluminum oxide (Al2O3) nano-additive fuels on the diesel engine with changeable engine speed and load in the present study. Analysis revealed that the parameters brake thermal efficiency (BTE), exergy efficiency, exergy destruction rate, engine sustainability, and other exergy parameters have higher values with increasing engine load and engine speed for all fuel samples. The engine BTE and exergy efficiency with 5%WiDE, 5%WiDE-Al2O3 and 5%WiDE-CNT nano additives are found to be 1.49%, 2.7%, and 3.07% and 1.85%, 3.08%, and 5.21% higher, respectively, than diesel fuel at 5.6kW effective power and 1500 rpm engine speed. The exergy based sustainability is found highest for 5%WiDE-CNT fuel, at 2000 engine rpm with full engine load. The exergy destruction rate and the entropy generation rate with the neat diesel is 1.42% higher than 5%WiDE fuel, while with 5%WiDE-Al2O3 and 5%WiDE-CNT nano additive fuels have 2.07% and 4.15%, higher values, respectively, compared to diesel fuel. The influence of engine load, engine speed, water emulsification, and nano additive on the exergy efficiency has found a little lower value than the energy efficiency.
    Keywords: Emulsification; CNT; exergy-sustainability analysis; exergy destruction.

  • Exergy-based analysis of irreversibilities for heat pump working fluids and cycle layouts   Order a copy of this article
    by Benjamin Zühlsdorf, Jonas Kjær Jensen, Brian Elmegaard 
    Abstract: The use of zeotropic mixtures in well-designed heat pump cycles enables considerable performance improvements. Temperature glide matching of the heat exchange processes and recovery of expansion losses by internal heat exchange decrease the exergy destruction and yield higher cycle performances. A case study for supply to district heating is presented, indicating increases in COP from 4.3 for a pure fluid in a standard cycle to 5.2 for a zeotropic mixture in a cycle with optimized internal heat exchange. As these improvement potentials are difficult to quantify by conventional and advanced exergy analysis, a new approach was suggested. For deriving a meaningful benchmark for cycle optimization, the exergy destruction was distinguished into a contribution describing the irreversibilities from the respective components operating with an ideal working fluid and cycle design and another contribution resulting from the cycle and working fluid being non-ideal. In addition, the exergy destruction was related to the COP, enabling an intuitive interpretation of the exergy-based analyses.
    Keywords: Cycle design; exergy; exergy destruction; heat pump; irreversibility; Lorenz cycle; refrigerant; temperature glide matching; working fluid; zeotropic mixtures.

  • Exergetic evaluation and optimisation of a novel integrated energy conversion system including thermoelectric generators   Order a copy of this article
    by Muhammad Zesshan Malik, Farayi Musharavati, Morteza Saadat-Targhi, Shoaib Khanmohammadi, HADI GANJEHSARABI 
    Abstract: A comprehensive thermodynamic study of a solar integrated energy system consisted of a solar flat plate collector, an organic Rankine cycle, a thermoelectric generator, and a proton exchange membrane electrolyzer is undertaken to generate power and hydrogen. The Matlab and Engineering Equation Solver softwares are linked, and various optimization scenarios are investigated. The results of computational analysis indicate that with adding a thermoelectric generator unit in the system about 14 kW of energy in the form of electricity can be obtained from the waste heat of condenser. Various optimization schemes with exergy efficiency, exergy destruction rate, as well as hourly hydrogen generation as optimization targets are considered. The optimization results comparison between base case and optimum design shows that exergetic efficiency improves by about 2.3% and rate of exergy destruction decrease by about 0.791 MW.
    Keywords: Electrolysis; exergy efficiency; heat recovery; thermoelectric generator; TEG.

  • Exergy analysis of vapour compression-absorption two stage refrigeration cycle   Order a copy of this article
    by Canan Cimsit, Ilhan Tekin Ozturk 
    Abstract: In this work, the exergy analysis of vapour compression-absorption two stage refrigeration cycle has been performed. To improve the performance of the cycle, it is possible to reduce the total damage by focusing on the parts that cause high exergy damage. Therefore, the detailed exergy analysis has been made for different operating conditions (generator temperature, condenser temperature and intermediate pressure) of the cycle. The exergy destruction rates each component were calculated and compared. The performance coefficient (COPcyclegen) increases as the intermediate pressure increases. Maximum value of the exergy efficiency is obtained at the intermediate pressure of 516.015 kPa. With this cycle, it is possible to refrigeration down by using alternative energy sources. Also, environmentally friendly is refrigeration system because environmentally safe fluids are used in this cycle.
    Keywords: Refrigeration; Absorption; Two stage refrigeration; Energy; Exergy.

  • Experimental study and exergy analysis of three-fluid tubular heat exchanger with nanofluids   Order a copy of this article
    by Tarikayehu Amanuel, Manish Mishra 
    Abstract: The present study addresses numerical and experimental approaches for exergy analysis of three-fluid tubular heat exchanger with Al2O3-water nanofluids. The goal is to assess the exergetic performance of employing nanofluids through a three-fluid heat exchanger. A Single-phase approach has been implemented to conduct numerical analysis in ANSYS fluent workbench v.17.2, commercial CFD package. Experiments were also conducted to investigate the effects of varying flow rates, flow arrangements, and nanoparticle volume concentrations on the overall performance of the exchanger under study. Reynolds number in the range 2500 - 10,000 and volume concentration of nanoparticles in the range 0 - 3% have been considered to study their effects. Besides, four flow arrangements (parallel, parallel-counter, counter-parallel, and counter) have been considered for numerical and experimental studies. The numerical investigation results revealed that increasing flow rate and addition of nanoparticles resulted in a reduction of exergy loss of the system. However, a non-monotonic variation of exergy loss with Reynolds number has been observed from experimental results. The experimental results also showed a significant deviation from the numerical ones, mainly due to the uncertainties in experimental measurements and equipment accuracy. At a maximum Re=10,000, a drop in exergy loss by 23.7% for parallel, 11.56% for parallel-counter, 10.6% for counter-parallel, and 25.8% for counter flow arrangements by varying ? from 0% to 3%. Furthermore, minimum exergy loss for all the flow arrangements was found at ?=3% and Re=4500.
    Keywords: Exergy; Experimental; Numerical; Three-fluid heat exchanger; Nanofluid.

  • Comparative Study of Three Modified sCO2 Brayton Recompression Cycles Based on Energy and Exergy Analysis with GA Optimization   Order a copy of this article
    by Chunlei Li, Qitai Eri 
    Abstract: As a novel supercritical CO2 (sCO2) power cycle, the recompression cycle has gained a lot of attention. Various modifications of the recompression cycle have been put forward. However, comparative studies are still required to determine whether these modifications are necessary. In this paper, three common modifications (reheating, partial cooling, reheated partial cooling) are analyzed and compared with the original recompression cycle from the exergetic perspective. Thermodynamic states are calculated based on the recuperator effectiveness. The genetic algorithm (GA) is used to calculate the split ratio, reheating pressure and pre-cooling pressure. The results show that the thermal efficiencies are: 40.01%, 40.44%, 39.88% and 41.63%. The exergy efficiencies are: 55.49%, 56.07%, 55.27% and 57.69%. They reveal that the modification of reheating or partial cooling alone fail to produce great improvement, but the combination of the two can. Furthermore, the results of a parametric study indicate that the conclusion are not limited to specific parameters. In most cases, a roughly 23% improvement is observed. An explanation can be given from the analysis of the exergy loss distribution and T-s diagrams, which reveal that the reheated partial cooling modification enhances the positive effects of both reheating and partial cooling, thereby achieving greater improvement.
    Keywords: sCO2 Brayton Cycle; Recompression cycle; Exergy analysis; Genetic algorithm optimization.

  • Enhanced Exergetic Evaluation of Regenerative and Recuperative Coal-Fired Power Plant   Order a copy of this article
    by Oguz Arslan, Merve Senturk Acar 
    Abstract: The coal-fired power generation systems are still in use and have a large rate in electricity generation for countries such as Turkey. In this regard, it is an important issue to take into account the relevance of coal generation, to achieve greater operating efficiencies, and to reduce costs and environmental impacts. From this point of view, combustion, which is the most exergy destructive process, should be handled in detail for potential improvement. In this study, Seyitomer coal-fired power plant was analyzed by the enhanced exergy method. In this regard, enhanced exergy analysis of coal combustion was introduced first by defining ideal and unavoidable conditions. The real conditions of the plant were obtained by measurements. As conclusion, an improvement potential of approximately 33.11% was determined for the overall system. The highest avoidable exergy destruction was determined in the boiler group with 29.46%. The endogenous part of this destruction was calculated as 6.77% where the exogenous part was approximately 22.69%. The improvement potential of the boiler group was determined as approximately 19.09%. The second highest avoidable exergy destruction was determined as the turbine group with approximately 16.35%. The endogenous part of this destruction was calculated as approximately 5.70% where the exogenous part was 10.65%.
    Keywords: Coal combustion; Enhanced Exergy; Power plant; Recuperation; Regeneration.

  • A detailed thermodynamic assessment and exergetic performance analysis of an industrial-scale orange juice production plant   Order a copy of this article
    by Zeinab Khorasani Zadeh, Farshid Nasiri, Khadijeh Faraji Mahyari 
    Abstract: In the present work, detailed exergy analysis was conducted on an industrial-scale orange juice production plant located in the north-west part of Iran. The plant consisted of four main lines including steam generation, above-zero refrigeration, mixing and pasteurization lines. The overall rate of destructed exergy in the whole plant was 17.7 MW. The majority (76.2 %) of it was observed in the steam generation in which boiler & compressor had the highest contribution (12073.09 kW /89%) in exergy destruction. In the above-zero refrigeration line, the ice-water tank possessed the highest exergy destruction (2802.36 kW) accounted for 71 % of total exergy destruction, which could be improved by thermal insulation. The mixing and pasteurization lines had the lowest overall exergy destruction (1.5 %). The exergetic efficiencies of all the pumps were in a poor range that strongly are suggested to employ the Variable Speed Drive.
    Keywords: Above-zero refrigeration; Exergy analysis; Exergy destruction; Exergy efficiency; Mixing and pasteurization; Steam generator.

  • Energy and entropy generation analysis of hydrological cycle in tropical regions   Order a copy of this article
    by Saumyakanta Mishra, Bishnu N. Mahapatra, Sudhansu S Sahoo, Auroshish Rout 
    Abstract: The hydrological cycle has been presented in a thermodynamic framework in this paper. The energy and the entropy studies of processes involved in the cycle have been carried out assuming that the hydrologic cycle acts as an actual Rankine cycle and the atmosphere consists of water only. The effect of the irreversibilities and the generation of entropy due to these irreversibilities are also taken into account. The net work of the cycle which is used for atmospheric circulation (mesoscale convective circulation) has been quantified for both the reversible and the irreversible processes. At a given set of operating conditions, the net work outputs and the efficiencies are evaluated for both reversible and irreversible cycles and both these determined values of the reversible cycle are found to be greater than those of the irreversible one. The efficiency value is found to vary from 0.028 to 0.068 when the difference in hot and cold temperatures varies from 10
    Keywords: Hydrological cycle; Rankine Cycle; Energy analysis; Entropy analysis; Irreversibilities.

  • Multi-Objective Optimization of Solar-Driven Combined Stirling Engine/LNG Burned Micro Gas Turbine based on Exergy and Energy Analysis   Order a copy of this article
    by Mojtaba Babaelahi, Hamed Jafari 
    Abstract: An appropriate method for electric power generation is one of the challenges that has been investigated by many researchers in recent years. Due to the limited resources available for fossil fuels, access to new resources and methods for power generation is critical. For the selection of these new resources, various indicators such as efficiency, production cost, and fuel consumption are significant. In this paper, a 200 kW Capstone microturbine is considered a base model and a Stirling engine. Solar energy and LNG fuel have been used as the system's hot source. To power generation in the Stirling engine, the exhaust heat of the Capstone microturbine and the cold exergy of the LNG evaporation has been used as the hot and cold source. For the evaluation of the proposed system, energy analysis and exergy methods have been used. The effect of using solar energy on the fuel consumption, and the effects of ambient temperature, the pressure ratio across the compressor, the temperature of the heat sink in the Stirling engine on the exergy and energy efficiency are examined. The results show that thermal efficiency improves from 34% (base cycle) to 38% and the exergy efficiency from 35% (base cycle) to about 43% in the proposed cycle. Also, the results showed that by increasing the comparison ratio and inlet temperature of the turbine, the exergy and energy efficiencies are increased. Finally, to find the optimal design point, multi-objective optimization was accomplished to reach the maximum efficiency through the particle swarm optimization (PSO) procedure. The results of the optimization showed that the exergy and energy efficiencies are increased by 6.42% and 15.92 %, respectively, compared to the base case.
    Keywords: Solar; Micro-gas-turbine; Stirling Engine; LNG; Exergy; Optimization.

  • Exergy based sustainability analysis of a dual fluid hybrid photovoltaic/thermal (PV/T) solar collector   Order a copy of this article
    by Hasila Jarimi, Devrim Aydin, Adnan Ibrahim, Ahmad Fazlizan, Ahmad Afif Safwan, Kamaruzzaman Sopian 
    Abstract: This paper aims to investigate the exergetic sustainability index (SI) of a dual-fluid PV/T type solar collector that integrates both air and water into the same solar collector. The contribution of the exergy efficiency of each of the dual fluid PV/T collectors components to the overall sustainability of the whole system was analyzed. A theoretical approach based on an experimentally validated numerical model was employed. The results show that, the SI of the PV component of the dual fluid PV/T system is in general higher than the solar thermal component by approximately 9% since it is higher in quality. When evaluated under three different climatic conditions, the contribution of the thermal component as a cooling medium to the PV is only prominent in hot climates with SI higher by 4% compared to the stand-alone PV system. For the cool and cold temperate climates, the difference is less than 0.1%.
    Keywords: Exergy; Sustainability; dual fluid; hybrid photovoltaic thermal; solar thermal.

  • Energy and Exergy Parameters of Low-Temperature Solar Thermal Energy Storage Systems: Empirical Estimation and Optimization   Order a copy of this article
    by Babatunde O. Adetifa, Ademola K. Aremu 
    Abstract: This study presents the energy and exergy analyses of three low-temperature solar thermal energy storage (STES) systems. These STESs were of the same design but, contained different heat storage materials (benzoic acid, stearic acid, and palm olein) evaluated during heat charging and discharging periods. The energy and exergy inputs and outputs were analysed and factored to estimate of the efficiencies during heat charging, while the energy and exergy drop during heat discharge were also estimated. The energy and exergy outputs were optimised using a set constraint employed on Design-Expert 11 software. The energy and exergy outputs ranged between 25.89-95.96 W and 13.15-52.37 W, respectively, depending on the type of heat storage materials used. Under optimized conditions, the energy and exergy outputs increased to 117.1-202.7 W and 81.2-107.5 W, respectively. The STESs were found to have a positive and significant effect on the energy and exergy efficiencies and on the energy and exergy drop. The quantity of water heated only affected the energy and exergy drop. This paper reveals that the energy and exergy parameters of a solar thermal system can be optimised by the integration of a STES.
    Keywords: Heat storage material; Energy; Exergy; Solar cooker; Design-Expert; Water heating.

  • Exergy Analysis of Petrol Engine Accommodated Nanoparticle in the Lubricant System   Order a copy of this article
    by Esam Jassim 
    Abstract: An energy and exergy analysis of a four stroke Spark Ignition Engine operated with nano-lubricant is experimentally investigated to assess the environment-engine energy interaction. The warm-up period and the influence of mixing nanoparticle with the lubricant on the exergy rate at various volume fractions VOF are also reported. It was observed that the engine warm-up period is dropped up to 40% when nano-lubricant is employed. The results also showed that presence of nanoparticles in the lubricant would double the exergy potential of the engine. Energy and Exergy efficiency are both augmented when nanocopper is mixed with the lubricant.
    Keywords: Exergy; ICE; Lubricant; Nanoparticle; Exergy Destruction Rate.

  • Thermodynamics analysis of biomass fired brick drying process   Order a copy of this article
    by Aziz Dogru, Emre Camcioglu, Onder Ozgener, Leyla Ozgener 
    Abstract: For drying the bricks used in the construction sector in Turkey is estimated that the need to power of 460MW. Moreover, the estimated energy consumption and produced brick are 2,680,400MWh/ year and 5 million ton per year, respectively. Due to increasing global warming and climate change, the amount of energy consumed per year for drying decreases. As the outdoor temperature increases, the amount of energy supplied for drying the brick will be reduced. This study was carried out because of this high energy consumption during drying process in brick production sector. According to the case study, energy and exergy analyses of a brick factory with an annual production capacity of 150,000 tons in Manisa were conducted using real operating data. The drying system was analyzed according to ambient temperature (0-20
    Keywords: thermodynamics; exergy.

  • An Exergy Analysis of a Concentric Tube Heat Exchanger using hBN-Water Nanofluids   Order a copy of this article
    by NESE BUDAK ZIYADANOGULLARI, Suleyman PERCIN 
    Abstract: This study investigated the effects of using nanofluids prepared with hexagonal boron nitride (hBN) nanoparticles on the thermal performance and pressure drop of a concentric tube heat exchanger. Experiments were carried out with water-hBN nanofluids for stable, dispersed, 0.01%, 0.1% and 1% volume concentrations, at different flow rates and Reynolds numbers under parallel- and counter-flow conditions. When the experimental results were examined, the exergy loss was higher in the parallel-flow heat exchanger compared to the counter-flow heat exchanger. The highest Exergy loss value was obtained for distilled water at the highest Reynolds number (Re = 7532) for parallel flow operation at 152 W. The exergy loss of water at the highest Reynolds number (Re = 7532) for parallel flow operation increased by 14.7%, 23.8% and 48.6% for hBN-water concentrations of 0.01%, 0.1% and 1% respectively. Exergy loss of water at the highest Reynold number (Re =7532) for counter flow operation increased by 9.23%, 15.3% and 27.1% for hBN-water concentrations of 0.01%, 0.1% and 1% respectively. When evaluating the exergy analysis of the system, exergy losses due to pressure drops were negligible for both flows (parallel and counter).
    Keywords: hexagonal boron nitride–water nanofluid; concentric tube heat exchanger; exergy efficiency; exergy loss; pump power.

  • Energy, exergy, and exergo-economic analyses of a novel three-generation system to produce power, heat, and distilled water   Order a copy of this article
    by Malihe Pashapour, Samad Jafarmadar, Shahram Khalilarya 
    Abstract: In this study, energy, exergy, and exergo-economic analyses were conducted for a new system producing power, heat, and distilled water. First, the waste heat of a gas turbine was recovered by a heat recovery steam generator, and then by an organic Rankine cycle. Simultaneously, a geothermal energy resource was utilized for re-heating the organic fluid to increase the power and efficiency of the ORC. Moreover, this system encompasses a reverse osmosis desalination unit to produce freshwater. Feed-water is heated in the condenser before it enters into the desalination unit; hence, specific power consumption of the high-pressure pump reduces by 43.52%. Exergy efficiency of the system was estimated to be 53.86%, where was 5% higher than basic mode (i.e., with no desalination unit and re-heating). The exergo-economic factor was 12.14%, suggesting that exergy destruction accounts for a high proportion of costs.
    Keywords: Energy; Exergy; Exergo-economic; Gas turbine; Organic Rankine cycle; Heat recovery; Re-heating; Geothermal energy; RO desalination.

  • ENERGY AND EXERGY ANALYSES OF EXPERIMENTAL COMPRESSED AIR VEHICLE PROTOTYPE WITH HEATING ELEMENT   Order a copy of this article
    by Reza Alizade Evrin, Ibrahim Dincer 
    Abstract: In this study, a new automobile powering system comprising of compressed air as a source of energy and as a non-polluting fuel is developed and tested. A working prototype for the pneumatic vehicle is developed at the Ontario Tech University, Oshawa and its performance is investigated. The compresssed air vehicle consists of a novel powering option integrated with a heating element prototype. The study introduces for the first time a compressed air vehicle prototype with 4 air mototrs powering the wheels. In addition, the compressed air exiting the motors is recovered for a second exapnsion to provide electrical power that heats the air before being recovered. The ACE dynamometer is used for investigating the performance of the developed prototype. The energy efficiency for the prototype is found to be 59.5%. Also, the exergy efficiency is 51.0%. The prototype driving range is calculated to be 128 km with 300 liters of air at a pressure of 350 bar. The maximum shaft work generated is measured as 20.84 kW.
    Keywords: Compressed air vehicle; prototype; energy; exergy; efficiency;.

Special Issue on: ECOS 2019 Progress in Exergy Analysis of Energy Systems

  • Exergy Analysis of Novel Integrated Systems Based on MHD Generators   Order a copy of this article
    by Hossein Sheykhlou, Samad Jafarmadar, Rogayieh Abbasgholi Rezaei 
    Abstract: The present work concerns with the thermodynamic analysis of novel opened and closed Magneto Hydrodynamic Organic Rankine Cycles (MHD-ORCs). In this regard, the thermodynamic simulation of the integrated systems with the assumption of the constant stream velocity in the MHD generator has been performed. The impact of MHD input temperature, the electrode surface area, the plasma velocity, and the compressor isentropic efficiency on the overall performance of the combined cycles have been investigated. Moreover, exergy and thermal efficiencies of opened and closed MHD based cycles have been calculated and achieved in optimal points as follows; 66.15 %, 71.67%, 49.21 %, and 39.77%, respectively.
    Keywords: Magneto Hydrodynamic Organic Rankine cycle; MHD generator; Coal combustion; Exergy Efficiency; Thermal Efficiency.

  • Study on combustion irreversibility in turbocharged spark-ignition engines   Order a copy of this article
    by Caio Henrique Rufino, Alessandro José Truta Beserra De Lima, Fazal-Um-Min Allah, Janito Vaqueiro Ferreira, Waldyr Luiz Ribeiro Gallo 
    Abstract: The direct injection (DI) and turbocharging strategies are recently adopted for spark ignition (SI) engines in order to achieve better fuel economy and lower pollutant emissions. A comprehensive analysis is required in order to evaluate the effects of aforementioned strategies on in-cylinder combustion processes. The second law analysis is a proficient thermodynamic tool which is used for identifying irreversibilities and exploring the possibilities of thermal systems optimization. The present work aims at carrying out an exergetic analysis of a downsized turbocharged DISI engine. The engine is fuelled with E10 (gasoline with 10% of ethanol content) while experimental data is acquired for different engine operating conditions. The exergetic analysis identified the combustion irreversibilities. Moreover, a comparison between second law analyses of a previously analysed port fuel injection (PFI) naturally aspirated SI engine and turbocharged DI SI engine is also presented. The study concluded with the potential benefits and drawbacks of newly adopted strategies for SI engines.
    Keywords: Direct-injection; Turbocharging; Spark ignition; Irreversibility; Exergy.

  • Exergy and environmental analysis of black liquor upgrading gasification in an integrated kraft pulp and ammonia production plant   Order a copy of this article
    by Meire Ellen Gorete Ribeiro Domingos, Daniel Florez-Orrego, Moises Teles Dos Santos, Hector Velasquez, Silvio De Oliveira Junior 
    Abstract: The black liquor is a byproduct of the kraft pulping process that contains more than half of the exergy content in the total woody biomass fed to the digester, representing a key supply of renewable energy to the pulping process. In this work, the conventional scenario of the black liquor use (i.e. concentration and combustion) is compared with the black liquor upgrading (via) gasification process for ammonia production in terms of economics, exergy efficiency and environmental impact. The combined energy integration and exergy analysis is used to identify the potential improvements that may remain hidden to the energy analysis alone, namely, the determination and mitigation of the process irreversibility. As a result, the exergy efficiencies of the conventional and the integrated cases average 40% and 42%, respectively, whereas the overall emission balance varies from 1.97 to -0.69 tCO2/tPulp, respectively. The negative CO2 emissions indicate the environmental benefits of the proposed integrated process compared to the conventional kraft pulp mill.
    Keywords: Entrained flow gasifier; Black liquor; kraft pulp; Exergy; Ammonia; Environmental impact; Renewability; Decarbonization; Energy integration; Fertilizers.
    DOI: 10.1504/IJEX.2021.10032908
     
  • Measurement of interior thermal environment of a passive solar house in an urban area in Japan and analysis of time-series variation of human body exergy balance   Order a copy of this article
    by Hideo Asada 
    Abstract: The purpose of this study was to know what kind of time-series variation of interior thermal environment was appeared in the passive solar house as a consequence of installed some passive methods, heating equipment and residents adaptive behaviour acquired through their own lifestyle and accumulated experience and to reveal what time-series variation of human body exergy balance were appeared as a consequence for living in a passive solar house. To know this, we had done a measurement on interior thermal environment of the passive solar house in urban area of Tokyo after 6 years have passed from constructed and had done analysis on time-series variation pattern of human body exergy. As a result, a unique interior thermal environment fluctuation pattern reflecting adaptive behaviour of the residents were formed in the passive house, and the time-series variation patterns of a human body exergy balance created by specific interior thermal environment in winter and summer were explicitly shown and discussed.
    Keywords: passive solar house; measurement; indoor thermal environment; passive solar house; urban area; analysis of time series variation; human body exergy balance; adaptive behavior; lifestyle; accumulated experience; time series variation pattern; unsteady state; radiant heating; natural ventilation; human body exergy consumption.

  • A thermodynamic explanation of the function of bifurcated structures in nature and in engineered artefacts   Order a copy of this article
    by Enrico Sciubba 
    Abstract: Why do bifurcated structures appear in nature? Both in living and non-living systems, the construction of a bifurcation requires some energy input, and in view of the economic principle of nature, this must be justified by a compensating gain for the resulting evolved structure. The most celebrated attempt to a theory of such phenomena is Bejans Constructal Theory, based on a generalization of the Hess-Murray law, first derived in 1903 by the Swiss biologist Walther Rudolf Hess. In spite of the great success of CT, some questions remain unanswered: Given that the purpose of bifurcations is to transport material and immaterial flows, what underlying principle governs the radius ratio between successive branches, the diameter/length ratio and the splitting angle? How do the prevailing boundary conditions influence the onset of bifurcations? This paper presents a novel thermodynamic model based on the assumption that the driving force behind the emergence of a bifurcated structure is its exergy cost. The model may be considered an extension and a completion of the Hess-Murray law: an extension, because it measures the advantage of branched structures with respect to their non-branched counterparts in terms of exergy instead of energy; a completion, because it includes the formation exergy, neglected by previous theories. Since exergy is a homogeneous and rigorous measure of the investment necessary to operate the transport, it seems natural to consider as the fuel required for this transport both the exergy equivalent of the work done to overcome friction and the material exergy embodied in the structure. The model proposed in this paper leads to a quantification of this primary exergy cost. The ubiquity of branched structures seems to suggest that they consume less exergy to perform the same task (transferring mass or energy), and thus can better exploit the resources available in their immediate surroundings, and the numerical results presented here confirm this intuition. The same principle ought to guide the design of artificial bifurcated structures or networks: more effective delivery of material and immaterial fluxes, milder mechanical and thermal gradients, higher power/volume and power/surface ratios
    Keywords: Bifurcated Flows; Exergy Analysis; Hess-Murray Law; Constructal Theory.

  • Electrified District Heating Networks: A Thermo-Economic Optimisation Based on Exergy and Energy Analyses   Order a copy of this article
    by Getnet Tadesse Ayele, Mohamed Tahar Mabrouk, Pierrick Haurant, Björn Laumert, Bruno Lacarrière, Massimo Santarelli 
    Abstract: This paper presents a thermo-economic optimisation of an electrified district heating network consisting of wind power plant, gas-fired combined heat and power plant and heat pumps. The load flow problem of the resulting multi-energy system is formulated by considering all physical and operating parameters in both of the electricity and heat distribution networks. First, energy and exergy analyses are applied to identify and isolate lossy branches of a meshed heating network. This is followed by the optimal placement of heat pumps. Finally, supply and return temperatures are optimised. Particle Swarm Optimisation technique is implemented in order to find the best place of heat pumps, their economical dispatch and optimal temperature profile of the district heating network. Results show that up to 59.12% of the distribution heat loss and 9.37% of the operating cost can be saved by following a step-by-step methodology discussed in this paper.
    Keywords: Combined heat and power (CHP) plants; District heating network (DHN); Electrified district heating network; Energy hubs; Exergy; Heat pumps; Lossy branch identification; Multi-energy systems; Optimal placement; Particle swarm optimisation; Thermo-economic optimisation.

  • Eco-credit system to incentivize the recycling of waste electric and electronic equipment based on a thermodynamic approach   Order a copy of this article
    by Alicia Valero, Ricardo Magdalena, Guiomar Calvo, Sonia Ascaso, Fernando Círez, Abel Ortegof 
    Abstract: The use of electric and electronic equipment has been increasing dramatically in the last years and entails an important amount of waste containing many valuable metals which could constitute an important source of raw materials if appropriately recycled. In this paper, an expression has been developed to value waste of electric and electronic equipment that are sent by users to an appropriate recycling plant. The user obtains in turn eco-credits, which can be later exchanged through different incentives. The eco-credit expression is based on the raw material content of the given device, assessed through an indicator called thermodynamic rarity, which rates minerals according to their scarcity in the crust and the energy required to mine and refine them. Additionally, the state of the device, lifetime and recyclability of the materials are considered in the equation. The expression has been applied as a case study to a working tablet and a LED lamp.
    Keywords: Raw Materials; Reuse; Recycling; Exergy; Eco-credits; Rarity; WEEE.

  • Exergy analysis of a thermostatic heat pump drying system with adjustable bypass air ratios   Order a copy of this article
    by Qiuyuan Qin, Lan Tang 
    Abstract: Drying is the best method to preserve products, but it will consume large amounts of energy. In this paper, a new heat pump drying system is designed, the wet cotton cloth is selected as drying material and the exergy analyses for the main components and the whole system are carried out. The results show that the maximum exergy loss always occurs in the compressor. Both the drying air temperature (DAT) and bypass air ratio (BAR) affect the exergy efficiency of the whole system and components. For the whole system and main components, the optimal BAR at 35?, 40?, 45? are always 40%, 0% and 60% respectively. Under a higher DAT, both the dehumidification ability of the evaporator and its exergy efficiency are reduced by the excess air mass flow rate. Through the exergy analysis, some improvement measures for the exergy efficiency are put forward.
    Keywords: Exergy Analysis; Heat Pump Drying; Drying air Temperature; Bypass Air Ratio.

Special Issue on: IEEES-12 Exergetic Solutions for Better Environment

  • Thermo-hydraulic and Exergy Analysis of Parabolic Trough Collector with Wire Matrix Turbulator: An Experimental Investigation   Order a copy of this article
    by Varun K, Arunachala Chandavar 
    Abstract: The present energy crisis due to the exhaustion of fossil fuels, global warming, the surging gap between energy supply and demand, high electricity price, etc. has paved a path to harness renewable energy resources effectively. Among various sources, due to enormous potential and implicit superiority, solar thermal energy has been proved to be the best solution for the energy crisis. As an outcome, the oldest and prevailing solar concentrating technology i.e. parabolic trough collector (PTC) is being used extensively. However, the majority of studies are numerical as its receiver is subjected to highly non-uniform concentrated heat flux (circumferentially). Further, the outdoor testing is a laborious task due to the transient operating condition. Hence a novel method having a combination of differential heating, analytical model, and SOLTRACE
    Keywords: Parabolic trough collector; Non-uniform heat flux; SOLTRACE®; Wire matrix; Performance evaluation criterion; Exergy enhancement ratio.

  • Design and comparative analysis of a geothermal energy supported plant for tri-generation purposes   Order a copy of this article
    by Nejat Tukenmez, Fatih Yilmaz, Murat Ozturk 
    Abstract: In this study, two geothermal-based energy systems that provide beneficial outputs of hydrogen, electricity and hot-water are proposed. In this study, two thermoelectric generators are included in the second system, unlike the first system, proposed to analyze the impact of thermoelectric generators on plant performance. For comprehensive thermodynamic and performance analysis of the proposed systems, the proposed systems are modeled according to thermodynamic equilibrium equations. The parametric works are performed to address the impact of different system indicators affecting the useful outputs and performance of the modeled systems. In addition, the performance evaluation of the modeled systems is conducted in comparison with several working fluids. The energetic and exergetic efficiencies of the designed first cycle are 40.4% and 31.57%, while the energetic and exergetic efficiencies of the suggested second cycle are found as 49.36% and 41.79%. The hydrogen generation realized by both proposed systems per unit time is 0.001196 kg/s.
    Keywords: Energy; Exergy; Geothermal Energy; Thermodynamic Analysis; Thermoelectric Generator.