International Journal of Exergy (53 papers in press)
Thermoeconomic assessment of a waste heat recovery system driven by a marine diesel engine for power and freshwater production
by Yadaleh Aghdoudchaboki, Ahmad Khoshgard, Gholam Reza Salehi, Farivar Fazelpour, Ali Emadi
Abstract: To develop eco-friendly ships, an integrated system with power and fresh water production capabilities is introduced so as to recover waste heat of a marine engine. A thermoeconomic analysis is conducted on the system which consists a marine engine, a multi-effect desalination unit and an organic Rankine cycle. The modelling results for the base case showed that the suggested cycle is capable of 387.95 kW power and 7.04 m3/hr fresh water. In addition, the effects of major design parameters on the system performance is assessed and illustrated. The ORC contributed to the total exergy destruction by 67% while that was 33% for MED unit. Moreover, a two-objective optimisation with total cost rate and exergy efficiency as objective functions is performed to obtain the optimum values of five design parameters. An optimal condition with the exergy efficiency of 35.96% and total cost rate of 2.54 $/hr is introduced as the best trade-off solution.
Keywords: thermoeconomic; waste heat recovery; WHR; marine engine; organic rankine cycle; ORC; multi-effect desalination; MED.
Advanced exergoeconomic analysis of solar-biomass hybrid systems for multi-energy generation
by ALAIN BIBOUM, Ahmet YILANCI
Abstract: In this study, advanced exergoeconomic analysis of solar-biomass hybrid energy systems for the northern part of Cameroon is conducted. Three concentrating solar power (CSP) technologies, Parabolic Trough Collector (PTC), Linear Fresnel Reflector (LFR) and Solar Tower (ST), hybridized with biomass-fired (BF) technology are investigated. It is found that exergy destruction from the solar field alone is responsible for the most of the whole exergy destructions (86.3% for PTC-BF, 92.2% for ST-BF and 85.4% for LFR-BF). The results show that LFR-BF hybrid system is the best cost-efficient system while ST-BF hybrid system is the worst cost-efficient system considering initial investment, avoidable-endogenous exergy destruction, cost associated with avoidable-endogenous exergy destruction and total cost required for the optimization.
Keywords: hybrid system; advanced exergy analysis; advanced exergoeconomic analysis; solar thermal power; concentrating solar energy; biomass.
Entropy Generation and Heat Transfer in Magnetohydrodynamic Two-Dimensional Stagnation-point Flow on a Sliding Plate
by Mehmet Demir
Abstract: Entropy generation and heat transfer in magnetohydrodynamic two-dimensional stagnation point flow of a viscous fluid over a moving horizontal plate have been investigated. The temperature of the plate is constant and sliding with a constant velocity in its own plane. An alternative similarity transformation has been proposed for the temperature field for not to neglect the viscous dissipation and Ohmic heating terms in the energy equation. The governing equations are reduced to a set of non-linear ordinary differential equations by using appropriate similarity transformations. Velocity components, temperature field, and local entropy generation rate are obtained numerically by using the Matlab built-in routine bvp4c. A new dimensionless group is used to represent the magnitude of dissipation which allows the transition to some special cases. The effects of the dimensionless parameters on the velocity components, temperature, and entropy generation are carefully examined and presented graphically. It has been observed that when the magnitude of the dissipation is high then an increase in the external magnetic field causes the increment of the temperature and entropy generation while decrementing the heat transfer from the wall to the fluid. In the other case, the effect of the external magnetic field is the opposite on the temperature and the heat transfer. Also, it has been shown that to neglect the viscous dissipation and/or Ohmic heating terms in the energy equation may lead to errors.
Keywords: Similarity transformation; Entropy generation; Stagnation point flow; Magnetohydrodynamics (MHD).
Sugarcane bagasse and vinasse conversion to electricity and biofuels: an exergoeconomic and environmental assessment
by Rafael Nogueira Nakashima, Daniel Flórez-Orrego, Hector Ivan Velásquez, Silvio De Oliveira Junior
Abstract: Biomass conversion into either electricity or biofuels requires various energy intensive processes that may drastically affect its technical and environmental competitiveness against their non-renewable counterparts. Therefore, in this paper, a comparative assessment between the total (c_t) and non-renewable (c_nr) unit exergy costs and specific CO_2 emissions (c_co2) of the electricity, methane and hydrogen produced from sugarcane vinasse and bagasse is presented and compared with the conventional (fossil fuel-based) supply chains. As a result, the non-renewable unit exergy costs and specific CO_2 2 emissions for the transportation service in all cases analyzed are 3.1 to 4.7 times lower compared with conventional fossil fuels (e.g. diesel, gasoline, natural gas and hydrogen). Among the waste upgrade alternatives, methane production is able to maximize the exergy flow rate of products in the transformation stage (52.4-58.6 MW), while hydrogen and electricity production can substantially increase the transportation service in the end-use stage (51.7-52.1%) and the operational revenues (2706-2889 EUR/h).
Keywords: sugarcane bagasse; vinasse; ethanol; biofuels; electricity;exergoeconomy; waste upgrade; environmental assessment; greenhouse gas emissions; biorefinery; anaerobic digestion; biomass gasification; hydrogen; biomethane; synthetic natural gas.
Exergoenvironmental Analysis and Evaluation of Coupling MSF, MED and RO Desalination Plants with a Combined Cycle Plant
by Mohammad Hasan Khoshgoftar Manesh, S. Kabiri, M. Yazdi
Abstract: In this paper, freshwater production through Multi-Effect Desalination (MED), Multi-stage Flash (MSF), Reverse Osmosis (RO), hybrid (MED+ RO) and hybrid (MSF+ RO) units have been investigated in view of Exergetic, Economic, and environmental analysis. Results show that the maximum amount of freshwater produced occurs in the combined cycle coupling with the MSF unit. This cycle can produce 1056.67 cubic meters per hour of freshwater. The amount of electricity power consumed in RO desalination unit is the lowest specific energy consumption among all desalination methods. The unit consumes about 5 kWh of electricity per cubic meter of freshwater produced. The cost of producing freshwater per RO desalination unit is very low. The RO unit freshwater price is about $ 0.1 per cubic meter. The integration of the selected desalination plants with Qom combined cycle power plant, the pollutants from the fuel and product of each equipment has been decreased significantly. Thus, the combined cycle combined with the MED unit the environmental impact rate decreased by 23% compared to the combined cycle. Also, in the integration of combined cycle with MSF unit, RO unit, MED_RO unit, and MSF_RO unit, it has been found that 25%, 60%, 27%, and 25% decrease can be obtained in the environmental impact rates, respectively.
Keywords: multi-stage flash desalination; Reverse Osmosis; multi-effect desalination; exergy; exergoenvironmental analysis; combined cycle power plant.
Comparative performance of an automobile heat pump system with an internal heat exchanger using R1234yf and R134a
by Erkutay Tasdemirci, Murat Hosoz
Abstract: Automotive heat pump (AHP) systems have been using in vehicles where waste heat is limited such as electric cars. Due to its impact on global warming, the use of R134a was restricted, and R1234yf has been regarded as its best alternative for automotive air conditioning systems. The AHP systems using R1234yf perform poorly, and a remedy to this problem may be the use of an internal heat exchanger (IHX). This study aims at evaluating and comparing various performance parameters of an experimental AHP system using R134a and R1234yf with and without an IHX. The findings revealed that the R1234yf system with IHX provided only 13.9% lower heating capacity but 7.8% higher COP based on total power consumption in comparison to the R134a system. Moreover, for 5
Keywords: R134a; R1234yf; heat pump; automotive; air conditioning.
A More Realistic Performance Evaluation of Solar Convertors: The Need for Exergic Spectral Analysis of Radiative Heat Transfer
by Amir Arya, Mahmood Yaghoubi, Khosrow Jafarpur
Abstract: Solar energy harvesting devices have got considerable attention by researchers and significant efforts have been made to optimize their performance recently. For efficiency studies, exergy analysis is a useful approach to evaluate the thermodynamic behavior of the related system. However, in contrary to conduction and convection mechanisms, the exergy theory of radiation is not well developed, yet. The conventional theory of Petela for radiation exergy, despite its global usage is not well applied for solar energy convertors which are working in a certain spectrum bandwidth such as photovoltaic (PV) panels. More specifically, the inlet exergy of PVs are generally assumed to be the full spectrum exergy, which is not the case for the available panels and consequently the calculated efficiency is underestimated. In the present study, the energy and entropy fraction functions are presented as a function of wavelength and temperature. Then, the integral form of the radiation exergy in a specified wavelength bandwidth is derived as a function of dimensionless wavelength and temperature. It is shown that in contrary to energy and entropy, the exergy fraction function cant be expressed as a function of a single variable (i.e. ?T). As an application, the second law efficiency of various PV panel types are estimated based on the proposed method and compared with those predicted by the usual approach. It is shown that up to 55 % error for exergic efficiency of PV panels might occur by using the conventional relation.
Keywords: Radiation exergy; Photovoltaic energy; Spectral performance; Petela’s formula; solar energy; radiation entropy; Black body fractional function;.
Exergy Analysis of Crude Oil Gathering and Transportation System by Three Box Model
by Qinglin Cheng
Abstract: "Three box" exergy analysis optimization method is applied to oil field system in order to identify and improve the weak links of crude oil gathering and transportation system. The universal Black Box, White Box, Gray Box models and balance equations of oil field analysis are established according to different requirements of rough, fine and sub-fine analysis. The weak link of energy utilization is determined. The heating furnace is identified as the lowest exergy efficiency equipment in crude oil gathering and transportation system, which can provide a theoretical basis and scientific method for improving system energy efficiency.
Keywords: "Three box" model; crude oil gathering and transportation system; weak link of energy utilization; heating furnace.
Performance Assessment of a Modified Power Generating Cycle based on Effective Ecological Power Density and Performance Coefficient
by GÜVEN GONCA, Bahri Sahin, Mehmet Cakir
Abstract: Thermo-ecological performance optimization and analyses of an engine running with a modified power generating cycle are carried out based on Effective Ecological Power Density (EFECPOD) and Effective Ecological Performance Coefficient (EFECPEC). They provide a unique value for combined characteristics of thermal efficiency, power, cycle volume, entropy generation and maximum combustion temperature. The impacts of design and operational parameters such as compression ratio, equivalence ratio, engine speed, exhaust temperature ratio, pressure ratio, cycle pressure ratio and cycle temperature ratio on maximum EFECPOD and EFECPEC have been examined for modified power generating cycle.
Keywords: Internal combustion engine cycles; Performance characteristics; EFECPOD; Thermo-ecology.
First and Second Law Based Thermal Optimisation of the Kalina Cycle Integrated into an Existing Burner-Based Cogeneration System Using Waste Chips as Fuel
by Yildiz Koc, Huseyin Yagli
Abstract: Due to increasing energy demand and decreasing fossil resources, the optimisation of existing systems has a critical role to minimise energy consumption and diminish the adverse effect of power systems on the environment. Therefore, the main interest of researchers is mainly focused on developing a new combined system to use energy sources more efficient. In the present study, a KC was integrated into an existing burner, which uses waste chips as fuel for producing steam and drying moist fiber. The KC was analysed based on the first and second law of thermodynamics and thermally optimised. After detailed analyses for varying turbine inlet temperature at 50 bar (up to 330
Keywords: Exergy; Kalina cycle; performance analysis; thermal optimisation; waste heat recovery; wood chipboard production.
An Exergy Study on Compression Ignition Engine Operating with Biogas Gas and Coke Oven Gas
by Hongqing Feng, Zhirong Nan
Abstract: This paper studies the combustion emission characteristics, exergy conversion and utilization, and irreversibility of compression ignition (CI) engines fueled by coke oven gas (COG) and biogas, which is conducted by establishing a zero-dimensional single-zone combustion model and an exergy analysis model. When the intake air temperature is same, the peak temperature of the COG in the cylinder is higher than the biogas, and the difference is about 64K, which results in much higher NOx emission of the coke oven gas. The irreversible loss of COG-fueled engines in the working process is 22% and the working exergy accounts for 58%, which is much larger than biogas. By properly increasing the intake air temperature, the intake pressure and speed can reduce the irreversible loss.
Keywords: Coke oven gas; Biogas; Exergy analysis; Compression ignition engine.
Exergy analysis of a shell & tube heat exchanger using DETHE software
by Joaquin Zueco, Sergio Ayala-MiÃ±ano
Abstract: In this paper, a sensibility study of irreversibility due to geometrical parameters variation of a shell-and-tube heat exchanger is proposed by using an exergy analysis. The irreversibility calculation model has been implemented on DETHE (Design Tubular Heat Exchangers) software, where thermohydraulic calculations are based on Bell-Delaware method. A prior evaluation of thermohydraulic results of DETHE is provided against a commercial software. Through an exergetic analysis in the study case, formulation to be implemented in the software for irreversibility calculation is developed. A real case study of a heat exchanger located in a pre-heat train of atmospheric crude distillation unit is analysed. Irreversibility results due to key design parameters variation for this heat exchanger are provided and discussed.
Keywords: Heat exchanger; Exergy method; Irreversibility; DETHE; Bell-Delaware; Second Law Thermodynamics.
Exergy analysis of plate heat exchanger with graphene alumina hybrid nanofluid: Experimentation
by Atul Bhattad
Abstract: The water-based hybrid nanofluid is proposed as a cooling agent in a corrugated counter-flow type plate heat exchanger aimed at sub-ambient temperature applications. For this purpose, an experimental investigation has been done with different working fluids. Fluids considered as a coolant are DI water, alumina nanofluid, and alumina-graphene hybrid nanofluid in 80:20 nanoparticle ratio by volume with a total volume concentration of 0.01% dispersed in DI water. Various exergy related performance factors like coolant outlet temperature, coolant exergy rate, irreversibility rate, non-dimensional exergy, and second law efficiency have been considered. The influence of coolant inlet temperature and flow rate on different parameters has been investigated. Coolant outlet temperature, coolant exergy rate, irreversibility rate and non-dimensional exergy augments by 2.5%, 4.8%, 7.5% and 3.5%, respectively. While the second law efficiency degrades using nanoparticles and increasing flow rate and decreases with the coolant inlet temperature.
Keywords: Hybrid nanofluid; Plate heat exchanger; Graphene; Non-dimensional exergy; Irreversibility; Second law efficiency.
Energetic and exergetic analysis of a novel geothermal driven multi-generation system using n-pentane as working fluid
by Nima Khosravi, Devrim Aydin
Abstract: In the present study, a geothermal driven multi-generation system for electric power, heating, cooling and hydrogen production is introduced. The proposed system is based on an Organic Rankine Cycle (ORC), where n-pentane is used as the working fluid. Within the study, it is aimed to evaluate the impact of geothermal source flow rate/temperature, ambient temperature and turbine inlet pressure on the energetic and exergetic performance of different system components. Besides, the overall first and second law efficiencies of the multi-generation system for different operating conditions are determined.
In the investigated system, generated electricity can be partially used for domestic needs while the rest is proposed to be used for hydrogen production through an electrolysis process. Heat recovered from the ORC is also utilized for driving a single-effect absorption chiller (SEAC) for producing heating and cooling. The study results showed that the optimum mass flow rate and temperature of the geothermal source are 11.88 kg/s and 483.2 K, respectively. For the optimized operating conditions of the proposed multi-generation system, overall energetic and exergetic efficiencies were determined as 0.56 and 0.41, respectively.
Keywords: multi-generation system; exergetic assessment; geothermal energy; organic rankine cycle; power generation; heating and cooling; electrolysis; hydrogen production; n-pentane; absorption.
Evaluation of an Urban Area in Cold Climate with a New Perspective: Exergoeconomic Analysis
by Yelda MERT, Suha Orçun MERT
Abstract: The Exergoeconomic analysis of an urban area is introduced in this study, performed in an annual energy interaction basis. The investigated period covers the year of 2016, and indoor and outdoor temperatures, construction properties, and annual energy consumptions for heating purposes were all taken into account during the analysis. The selected urban area is the Campus housings of Van Yuzuncu Y?l University, which were constructed in 2012 after the Van Earthquakes. Known as an important tool in understanding the cost structure of energy-intensive sectors, the exergoeconomic analysis was introduced as part of the planning concept in the study, and the analysis involves the results of exergetic cost and exergy efficiency analyses for the case area. Considering the urban nature of the study location, annual meteorological and domestic values were fully covered in the calculations. The results show that, despite being a well-designed and constructed urban area, certain specific design considerations were not met, and there is plenty of space for improvement in cost-reduction, particularly so for a location with such a cold climate.
Keywords: efficiency; exergoeconomy; exergy; mass housing; urban area planning.
Energy and exergy analyses of solar drying sardine fillets
by Hamza Lamsyehe, Younes Bahammou, Hind Mouhanni, Mounir Kouhila, Zakaria Tagnamas, Haytem Moussaoui, Abdelkader Lamharrar, Ali Idlimam
Abstract: Fish is a highly perishable food product. It has a very short because it contains up to 78% of water. The aim of this work is to examine the effect of solar drying on the dehydration kinetics of Moroccan sardine fillets. The curves of the experimental kinetics of drying sardine fillets are carried out at four temperatures (50, 60, 70 and 80
Keywords: Activation energy; diffusion coefficient; exergy; sardine fillets; solar drying.
Optimized Annual Performance of Hybrid Solar Energy MED-TVC Desalination Plants with and without Preheating
by Davood Beyralvand, Mahmood Yaghoubi
Abstract: In the current study, energy, exergy, economic and environmental (4E) analysis for a multi-effect desalination plant with and without feed brine preheater integrated with a steam boiler and solar hybrid system for three coastal cities of southern Iran during a year is investigated. Four main configurations of hybrid/MED-TVC, hybrid/MED-TVC.FH, boiler/ MED-TVC and boiler/MED-TVC.FH are considered. By using Artificial Bee Colony algorithm, systems were optimised. The results show that: using feed brine preheater, the unit cost reduced by 6.5% for the system with a boiler and 3.8% for the hybrid system.
Keywords: Solar energy; MED-TVC.FH; CO2 emission; ABC algorithm; 4E analysis.
Parametric analysis of Energy and Exergy of the human body in Indian conditions
by Arvind Kumar Patel, SATISH P.A.L. SINGH Rajput
Abstract: The second law of thermodynamics is useful to examine the energy and exergy analyses of any energy conversion system. Over the past decades, this law is also applied to biological systems, such as the human body and other natural species. In this work, energy and exergy parameters of the homeotherms in the summer and winter seasons are performed for Indian conditions by using the approach of exergy analysis. For this study, Bhopal (India) is selected as the location for environmental data. The weather of Bhopal is hot and arid for summer and cold and dry for the winter. The outcome of this work indicates that the energetic metabolic rate is much higher than the metabolic exergetic rate. The actual metabolic rate for the summer season is 60 W/m2 compared to 72.91 W/m2for the winter and the metabolic exergetic rate for winter is almost three times higher than summer. The maximum energy loss from all sources of heat transfer is calculated as 34.26 W/m2 in summer and 40.48 W/m2 in winter.rnFurther in the summer season, the Predicted Mean Vote value is 0.85, and in winter, this value is slightly higher at1.06. Because of the higher Predicted mean vote value, the Predicted Percentage Dissatisfaction is also somewhat high. The Predicted percentage of dissatisfaction values for summer and winter are 24.49% and 28.71%, respectively. These results indicate that thermal dissatisfaction is more significant in the winter season compared to the summer season. rn
Keywords: Energy; Exergy; PMV; PPD; Thermal Comfort; Summer; Winter.
Application of Cumulative Exergy Consumption Approach to Assess the Sustainability of Rapeseed Production in Two Different Farming Systems
by Mahdi Esmaeilpour-Troujeni, Abbas Rohani, Mehdi Khojastehpour
Abstract: The study aimed to assess the sustainability of mechanized production system (MPS) and semi-mechanized production system (SMPS) in the rapeseed agroecosystem in northern Iran. The study was conducted through the cumulative exergy consumption (CExC) approach, including the two sustainability indices of cumulative degree of perfection (CDP) and renewability index (RI). The CDP was higher in the MPS (4.36) than SMPS (4.29). The RI was determined to be 0.712 for MPS and 0.731 for SMPS. The results highlighted that CDP and RI could significantly be improved through the consumption of renewable-based energy resources, including biofuel and solar energy.
Keywords: Cumulative exergy consumption; Mechanized and Semi-mechanized; Rapeseed; Renewable energy; Sustainable agriculture.
Energy, Exergy and Exergo-environmental Assessment of a Novel Solar powered Kalina Cycle Incorporated with Micro-CCHP for Poly-generation.
by Victor Adebayo, Michael Adedeji, Muhammad Abid, Olusola Bamisile
Abstract: In this study, a solar parabolic trough collector combined with a Kalina cycle, multi-stage flash desalination unit, a proton exchange membrane electrolyzer for hydrogen production, and a micro-combined cooling, heating, and power system is presented. Systematic energy, exergy, and exergo-environmental evaluation is used to analyze the viability of the integrated systems as the most effective approach for performance assessment of integrated systems. The energy and exergy efficiencies of the overall system is observed to be 50.51% and 3.27% respectively. The rate of exergy destruction of each component and the overall cycle is determined where the parabolic trough collector is shown to have an exergy destruction rate of 234.4kW, which is the highest among all the components. The performance of the proposed systems is also checked through a parametric study of the different key parameters.
Keywords: Energy; Exergy; Exergo-environmental; Desalination; Hydrogen.
Enhanced exergy based malfunction diagnosis of an integrated solar combined cycle system: Parametric study and multi-objective optimization
by Fateme Ahmadi Boyaghchi
Abstract: In this research, a malfunction diagnosis method based on the enhanced exergy concept is applied to quantify the anomalies' sources in a real integrated solar combined cycle system (ISCCS). A comprehensive parametric study is performed to evaluate the malfunction indicators and the overall performance of the power plant by varying the substantial operating parameters under single and multi-malfunction conditions. Then, the fast and elitist non-dominated sorting genetic algorithm (NSGA-II) is applied to maximize the net power and minimize the total exergy destruction rate of the system under a multi-malfunction condition.
Keywords: Malfunction diagnosis; performance degradation; enhanced exergy; ISCCS; parametric study; optimization.
Environmental life cycle assessment of an ammonia production process through Cumulative Exergy Demand and ReCiPe: A focus on power generation from natural gas and biomass
by A. Ghannadzadeh, R. Shabani, H. Ale Ebrahim
Abstract: The environmental impacts of the ammonia production process are because of the discharge of harmful chemicals as well as the high electricity demand. One way to control its environmental impacts in the electricity transition phase, is the natural gas/biomass based scenarios. This Life Cycle Assessment (LCA) study, which has used ReCiPe and Cumulative Exergy Demand, proves that natural gas is not right option for this specific case because the natural gas-based scenarios have more burdens than the residual fuel oil-based scenarios especially regarding Fossil Depletion (0.72%), Human Toxicity (14%), Freshwater Ecotoxicity (23%), Particulate Matter Formation (33%), Marine Ecotoxicity (37%), and Terrestrial Acidification (40%). Moreover, this study shows that it is possible to reduce the environmental impacts without retrofitting the heart of process technology using the biomass-based scenarios. This paves the way for a sustainable ammonia process under the energy transition scenarios where retrofitting the process heart is not desired.
Keywords: Environmental sustainability; Exergy; ReCiPe; Energy transition; Bioenergy; Monte Carlo simulation.
Experimental Study and Exergy Efficiency Prediction of Three-leaved Yam (Dioscorea Dumetorum) Starch Drying
by Emmanuel Oke, Kenechi Nwosu-obieogu, Chiamaka Ude
Abstract: This study predicted three-leaved yam starch drying using Adaptive Neuro-Fuzzy Inference System (ANFIS), Artificial Neural Network (ANN) and Support Vector Machine (SVM). The input and output variables were drying temperature, time, air velocity and Exergy Efficiency (EE) as well as Sustainability Index (SI) respectively. The EE performance indices are: ANN (R2 = 0.999, MSE=7.40038E-13), ANFIS (R2 = 0.251, MSE=0.001) and SVM (R2 = 0.999, MSE= 3.25E-06). The SI prediction indices are: ANN (R2 = 0.99, MSE=1.0E-10), ANFIS (R2 = 0.41, MSE=0.010) and SVM (R2 = 0.61, MSE= 0.051).
Keywords: Exergy efficiency; ANN; ANFIS; SVM; Sustainability index.
ENTROPY GENERATION AND ACCUMULATION IN BIOLOGICAL SYSTEMS
by Mustafa Özilgen, Cennet Yildiz, Ayse Selcen Semerciöz, Bahar Hazal Yalcinkaya, Tanya Deniz Ipek, Esin Öztürk Isik
Abstract: In living systems, entropy is generated as the result of the metabolic activity, most of it is exported, while only a small fraction is accumulated. Accumulation reveals itself as structural impairment, regarded as a sign of aging and measured in terms of information entropy. This study shows that higher blood flow rate fuels higher work performance and cause higher entropy generation. Since a very important fraction of the work performance in a living system is the internal work, including those of the heart beating, breathing, formation of new molecules, maintenance of the body, muscle contraction-relaxation process, signal transmission in neurons and active transport of some molecules, entropy generation should not be regarded detrimental to the organisms as long as entropy is not collected, but exported. Anterior cingulate cortex, a constituent of the grey matter in the brain, is the neuroanatomical interface between emotion and cognition. In the literature, lower blood flow, is reported as the cause of the shrinking grey matter volume, i.e., entropy accumulation, with aging, confirming that entropy generation within an organ is not detrimental for health, as long as the entropy does not accumulate but flushed out.
Keywords: Aging impairment; Entropy accumulation; Entropy generation; Information entropy; Measuring impairment.
Experimental study on exergy and sustainability analysis of the thermoelectric based exhaust waste heat recovery system
by Rashmi Sahoo
Abstract: In the present study, the energy and exergy analysis of a thermoelectric based waste heat recovery system of a passenger automobile is performed at different loads. Further, an exergetic sustainability assessment is performed by incorporating parameters like exergy destruction factor, environmental impact factor and exergetic sustainability index. Results revealed that by employing waste heat recovery, the exergetic efficiency can be improved by up to 5.78%. The study showed that the exhaust gas is more suitable for heat recovery as it has 81.8 % more exergy than the cooling water.
Keywords: Thermoelectric generators; power; sustainability; entropy generation.
Energy and Exergy Analysis of Solar Photovoltaic Thermal (PV/T) System: Experimental and Numerical Verification
by Metin GÜL, Ersin AKYÜZ
Abstract: In this study, the electrical and thermodynamic performance of a flat-plate liquid PV/T system was investigated, and the experimental results were verified with a numerical model implemented. The simulation analyses showed that the increasing inlet and ambient temperature had a negative effect on thermal efficiency and the highest thermal efficiency was obtained at 800 W/m2 solar radiation. The optical efficiency of the experimental system was verified with the simulation and reported as 45.8% and 47.9%, respectively. Electrical, thermal, and total energy efficiencies obtained hourly on a daily basis were also calculated and varied between 1213.8%, 36.1-45.2%, and 49.1-58.4% respectively. The hourly exergy analyses were also carried out on a daily basis and the results showed that the exergy efficiencies changed between 13.8-14.32%. The experimental data measured in a period of 19 days was analysed and it was found that 68.9 kWh thermal and 19.5 kWh electrical energy were produced from the system at 0.033 kg/s mass flow rate. The annual total thermal and electricity energy outputs were also calculated by using the measured meteorological data as 1912 kWh and 556.8 kWh respectively. In addition, an economic analysis was conducted for the PV/T system, both thermal and electrical energy costs were calculated separately, and sensitive analysis was performed to calculate the effect on the cost of energy by varying interest rate and lifetime of the system.
Keywords: Photovoltaic thermal system (PV/T); solar energy; energy; exergy; life-cycle cost.
Performance Analysis of Human Cardiorespiratory System based on the Second Law of Thermodynamics
by Abhijit Dutta, Himadri Chattopadhyay
Abstract: The purpose of this study is to develop a thermodynamic model of the human cardiorespiratory system under different physiological conditions. To quantify the performance, an analysis based on the second law of thermodynamics has been carried out for the human cardiorespiratory system. The analysis reports three different physiological conditions i.e. rest, moderate level of physical activity and extreme level of physical activity. While the body temperature was assumed at 360C, the standard ambient condition is taken as 250C dry bulb temperature (DBT) and 50% relative humidity (RH). Results show that the human cardiorespiratory performance increases significantly with the increase in physical activity. However, the cardiorespiratory performance also notably increases with the increase in ambient temperature and RH. The cardiomegaly condition of the human cardiorespiratory system decreases the efficiency of the system. It has been observed that O2 fluctuation for metabolic use has no significant effect on the human cardiorespiratory performance. A new dimensionless number, which is the ratio of breathing rate to the heart rate (BHR), is introduced in this work. The increase in BHR affects the cardiorespiratory system performance at rest. During an elevated level of physical activity, the rise in BHR increases the cardiorespiratory performance. The present work reveals that the thermodynamic performance of the cardiorespiratory system depends on the inhaled air property (temperature and RH), cardiomegaly condition and the variation of BHR. It is also noticed that the efficiency of the cardiorespiratory system behaves in a different manner at different levels of activities with the rise in BHR. At rest, efficiency decreases with the increase in BHR, however, it increases with the increase in BHR during the active condition. Hence authors of this work believe that this BHR might have a strong connection with the governing of the artificial ventilation. The state of hypoxia and hyperoxia is basically a consequence of change in BHR.
Keywords: Cardiorespiratory system; Thermodynamic performance; Physiological condition; Relative humidity; Breathing rate to heart rate ratio (BHR).
Thermodynamic assessment of a new solar power-based multigeneration energy plant with thermochemical cycle
by Murat Ozturk
Abstract: In this study, a novel solar energy assisted multigeneration energy plant by using the solar radiation as a renewable energy resource is designed to produce some useful products, such as electricity, heating-cooling, and hydrogen, and modeled to increase the system performance. This designed multigeneration energy system consists of the solar power tower, steam Rankine cycles, absorption heating-cooling system, Cu-Cl thermochemical cycle, and hydrogen liquefaction unit. A thermodynamic assessment is developed by using the energetic and exergetic analyses to determine the irreversibilities of Cu-Cl thermochemical reaction-based integrated system at different working conditions. The energy and exergy performances of solar power assisted multigeneration system are computed as 22.21% and 14.02%. In the present study, the highest exergy destruction of this plant is determined for the solar power tower, and also, 5738 and 4812 kW of exergy destruction happens in the heliostat and central receiver, respectively. Moreover, the parametric works are carried out by changing the reference conditions and design indicators.
Keywords: Solar energy; thermodynamic analysis; integrated system; thermochemical cycle.
Energy and exergy analyses of a large capacity supercritical utility boiler system
by Perwez Siddiqui
Abstract: In this study, energy and exergy analyses of an 800 MW supercritical utility coal-fired boiler have been conducted to assess the thermodynamic performance of all the individual heat transfer components and the entire boiler as well for the various plant operating conditions: BMCR, VWO, TMCR, 100% TMCR, 80% TMCR, 60% TMCR, 50% TMCR, and all HP heaters out of service. It is found that the 1st law efficiency of the boiler varies from 85.98% to 87.28%, and 2nd law efficiency of the boiler varies from 44.33% to 46.62% for the above operating conditions. The highest exergy conversion efficiency is found to be in the primary superheater, except for all HP heaters out of service condition where it is found to be in the primary reheater. Maximum exergy destruction is found to be in combustion chamber and then water wall for the above operating conditions.
Keywords: boiler; energy; exergy; thermal efficiency.
Embodied Exergy-based analysis of a Municipal Solid Waste treatment system with uncertainty inclusion
by Sofia Russo, Vittorio Verda
Abstract: The development of an Integrated Solid Waste Management (ISWM) system is still a matter of interest in many countries. One of the main challenges is to efficiently allocate the material streams in order to save energy and recover materials. The aim of this paper is to use the Embodied Exergy criteria to evaluate the distribution of the material streams into a Solid Waste (SW) treatment system composed by: a Mechanical Biological Treatment (MBT) plant for Refuse Derived Fuel (RDF) production and a paper recycling plant for cardboard production. Two scenarios are compared, based on the inlet mass flow to the MBT plant and the cardboard production. Stochastic tools based on Monte Carlo simulation are adopted for generating simulation scenarios, in order to account for the uncertainty that occurs in external (e.g. waste composition) and internal (e.g. equipment energy consumption) parameters.
Keywords: Municipal Solid Waste; Mechanical Biological Treatment; Paper recycling; Uncertainty analysis; Embodied Exergy; Exergy analysis.
Thermodynamic analysis and optimization of double effect absorption type combined power and cooling cycle using LiBr-water as working fluid
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
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
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
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
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
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
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.
Microphysical analysis for peristaltic flow of SWCNT and MWCNT carbon nanotubes inside a catheterised artery having thrombus: Irreversibility effects with Entropy
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
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
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
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
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
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.
Special Issue on: GCGW-2019 Exergy Analysis of Processes Associated with Global Warming
ASSESSMENT AND APPLY OF AN ENHANCED EXERGY ANALYSIS FOR AN ARGON LIQUEFACTION SYSTEM
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.
EXERGY-BASED EVALUATION OF A WASTE HEAT DRIVEN POLYGENERATION SYSTEM WITH CO2 AS THE WORKING FLUID
by Jing Luo, Tatiana Morosuk, George Tsatsaronis, Bourhan Tashtoush
Abstract: A waste heat driven polygeneration system that couples a supercritical power cycle with a transcritical refrigeration cycle is proposed and evaluated in this study. The stand-alone system using carbon dioxide as the working fluid produces power, refrigeration, and heating capacities simultaneously. Three scenarios of the system with different ambient temperatures (25-35oC) are optimized using the exergoeconomic approach to obtain the lowest average cost of the products. The obtained results show that the average product cost is the highest (113 $/GJ) for the scenario with the ambient temperature of 30 oC, while the product cost is reduced to 82 $/GJ when the ambient temperature is 35 oC. Moreover, the pressure for merging the sub-systems influences the performance of the system significantly, and the variations of the operating conditions differ among the scenarios by increasing the merging pressure. Besides, a multi-objective optimization is implemented for supporting decision-makers to find the optimal solutions.
Keywords: Polygeneration system; Carbon dioxide; Supercritical power cycle; Transcritical refrigeration cycle; Exergoeconomics; Optimization.
GIS-Based Maritime Spatial Planning for Site Selection of Offshore Wind Farms with Exergy Efficiency Analysis: A Case Study
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.
Special Issue on: ECOS 2019 Progress in Exergy Analysis of Energy Systems
Exergy Analysis of Novel Integrated Systems Based on MHD Generators
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
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
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.
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
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
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
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
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.