Forthcoming articles

International Journal of Exergy

International Journal of Exergy (IJEX)

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International Journal of Exergy (31 papers in press)

Regular Issues

  • Exergetic Approach to Determine Optimum Insulation Thickness for Cooling Applications with Life cycle Integrated Economic Analysis   Order a copy of this article
    by Emin Acikkalp, Süheyla Yerel Kandemir, Onder Altuntas, T. Hikmet Karakoc 
    Abstract: Optimum insulation thickness for building walls is investigated using a new method called as Combined economic and environmental methods (CEEM). In this method, environmental costs are integrated in the fuel and insulation material costs and in this way, it is possible to consider both of economic and environmental aspects. Environmental cost of carbon dioxide, fuel and insulation materials are added to their cost and total annual cost for the system is calculated and results are investigated according to insulation thickness. In this paper, optimum insulation thickness with life cycle integrated economic analysis in terms of exergy approach is defined. Rockwool and glasswool are chosen as insulation materials and calculations were made for Bilecik located in Marmara region in Turkey. Optimum points are found for CEEM, economic approach and environmental approach and they are compared with each other.
    Keywords: Insulation thickness; life cycle integrated economic analysis; energy consumption.

  • Exergetic optimization of twin screw expanders   Order a copy of this article
    by Hormoz Abolhasani, Mahdi Moghimi, Mahmood Ebrahimi 
    Abstract: Limited access to energy resources, air pollution and its subsequent detriments to Ozone layer have accentuated the importance of green industry for recovering exergy from high-pressure flow to generate clean electrical power. Due to low maintenance costs, usage in two-phase fluids and longer lifespan, the twin screw expanders (TSE) have attracted great attention though there is still much to be done to improve their performance. The complexity of computing in screw machines, as well as the time consuming of their simulation throughout the entire design space by the computational fluid dynamics (CFD), requires the use of other complementary tools to optimize the performance of these types of machines. In this paper, based on laboratory model specification and experimental data a TSE model was simulated and validated using CFD. Consequently, by helping design of experiments (DOE) a CFD alternative model is obtained called surrogate-based modeling (SBM) and the effect of three main geometric parameters on the expanders exergy efficiency were investigated in entire design space. Finally, a more efficient TSE with 86% exergy efficiency was obtained by using multi-objective genetic algorithm in the shortest time.
    Keywords: Exergy efficiency; Surrogate-based modeling; Twin screw expander; Design of experiments.

  • Performance simulation of a double-reheat Rankine cycle mercury turbine system based on exergy   Order a copy of this article
    by GÜVEN GONCA, İbrahim Genç 
    Abstract: In this paper, a thermo-ecologic performance investgation of a Rankine cycle mercury turbine system (RCMTS) operating with natural gas and consisting of three turbines, one open feed mercury heater (OFMH) and two closed feed mercury heaters (CFMHs) is comprehensively performed. The most known performance characteristics such as net power (NP), net power density (NPD), exergy efficiency (EXEF), exergy destruction (EXED) and ecological coefficient of performance (ECOP) are used to investigate and optimize the system performance. The effects of condenser and boiler temperatures, the first and second reheat stage temperatures, temperature of the extracted mercury from the LPMT (Low pressure mercury turbine) on the performance properties of the system have been investigated. The results indicated that the component pressures and stage temperatures noticeably affect the performance characteristics of the mercury turbine system.
    Keywords: Mercury turbine; Optimization; Reheated Rankine cycle; ECOP; Exergy; ANN Model.

  • Experimental Investigation of Phase Change Material Utilization Inside the Horizontal Mantled Hot Water Tank   Order a copy of this article
    by Dogan Erdemir, Necdet Altuntop 
    Abstract: The main objective of this study is to experimentally investigate the effect of placing phase change material (PCM) inside the horizontal mantled hot water tank on thermal energy storage (TES) performance. Six cylindrical paraffin tubes made of glass of 1 liter were placed inside the mantled hot water tank storage tank side by side vertically, respectively. At the end of this study, it was found that using paraffin inside the hot water tank increased the TES capacity and amount of hot water obtained from the tank. The amount of obtained hot water didnt increase proportionally with the increase of the amount of paraffin, as the volume of the tank was constant. Because the amount of hot water in the tank decreased with increasing the amount of paraffin. The stored energy in the paraffin wasnt transferred to the water efficiently. In order to obtain the highest volume of hot water, 4 tubes paraffin should be placed inside the tank. Discharging period duration could be increased 17 minutes with 4 tubes paraffin. Each added 1-liter paraffin reduced the temperature in the tank by nearly 1
    Keywords: Horizontal mantled hot water tank; Phase change material; Paraffin; Solar domestic hot water system.

  • Energy and Exergy Analyses of Chemical Looping Combustion based 660 MWe Supercritical Coal Fired Power Plant   Order a copy of this article
    by Gajanan Dattarao Surywanshi, B. Basant Kumar Pillai, Venkata Suresh Patnaikuni, Ramsagar Vooradi, Sarath Babu Anne 
    Abstract: Coal still remains to be the major resource for power production in many countries. Supercritical (SupC) steam generated coal-fired power plants (CFPP) are found to be superior to subcritical steam generated plants in terms of the overall plant efficiency. Chemical looping combustion (CLC), which is an indirect combustion between fuel and air, is an innovative, inherent CO2 capture and recent technology for power production. In this study, two cases - conventional SupC CFPP without CO2 capture and CLC based SupC CFPP for high-ash Indian coal have been simulated. Detailed energy and exergy analyses are conducted for both the cases and compared. The study shows that CLC based capture technology has less energy penalty with Fe2O3 oxygen carrier and little energy gain with CuO and NiO carriers compared to conventional plant without CO2 capture. This study demonstrates the superiority of CLC based SupC CFPP for CO2 capture over the conventional plant.
    Keywords: Supercritical power plant; Chemical looping combustion; Energy analysis; Exergy analysis; High ash coal.
    DOI: 10.1504/IJEX.2020.10024695
  • Human body exergy consumption in the thermal environment of shelter gymnasium in winter   Order a copy of this article
    by Koichi Isawa 
    Abstract: This study attempts to evaluate the thermal stress in the winter shelter gymnasium in terms of human body exergy balance analysis. The human bodys exergy consumption rate was quantitatively analysed, revealing that the total human exergy consumption differs depending on the difference in heat insulation performance of the evacuation gymnasium. Integrated exergy consumption after 30 days is 15.7 MJ/m2 for an existing outer skin with no heating, 14.4 MJ/m2 for an existing outer skin with radiant heating, and 12.5 MJ/m2 for a modified outer shell with no heating It decreased to 9.6 MJ/m2 in the rehabilitating envelope with radiant heating. In the case of existing hulls, accumulation of thermal stress was found to be greater than in the case of renovation hulls.
    Keywords: natural disaster; community shelter; gymnasium; indoor thermal environment; thermal stress; human body; thermal adaptation; physiological adaptation; exergy; Numerical analysis.; unsteady state; passive system; building envelope; active system; heating system.

  • Entropy analysis of 3D MHD nanofluid flow over a linearly stretching surface   Order a copy of this article
    by Muhammad Nazim Tufail, Adnan Saeed Butt, Asif Ali 
    Abstract: A numerical study of three dimensional magnetohydrodynamic flow of nanofluid over a surface stretching linearly in two directions is carried out. The problem is analyzed from first and second law of thermodynamics point of view. Suitable similarity transformations are employed to obtain nonlinear ordinary differential equations from the partial differential equations that govern the considered problem. The shooting technique with fourth fifth order Runge Kutta method is utilized to solve the converted equations. The effects of pertinent parameters on velocity and temperature profiles as well as on entropy generation are discussed briefly using graphs.
    Keywords: Buongiorno model; Brownian motion; thermophoresis; entropy generation; magnetic field.

  • Exergy analysis of the valorization of rice straw for energy purposes with a life cycle approach. Rice production in Cuba   Order a copy of this article
    by Edelvy Bravo, Ralf Kiran Schulz, Osvaldo Romero Romero, Eduardo Lopez Bastida, Yenima Martinez Castro, Alberto E. Calvo Gonzalez, Leonor Patricia Guereca Hernandez 
    Abstract: In this paper the Exergy analysis methodology is used to analyze four alternatives for the valorization of rice straw for energy purposes in Cuba. The exergy input and output of the product (%), the exergy destroyed (MJ) and the exergetic efficiency (%) are calculated. The exergetic efficiency increases in the three alternatives where rice straw is valorized for energetic purposes. In alternative 4, where it is considered the production of biomethane (to replace 60% of the diesel fuel for harvesting and transportation of products) and electricity via biogas, the exergetic efficiency reaches values of 66.6%. The exergy flow contained in the product increases from 13.2% to 21.9%. The increase in exergy flow in the final product also represents a reduction in greenhouse gas emissions as emissions are avoided by generating the same amount of electricity in a thermal power plant. Alternative 4 also achieves the highest sustainability index (2.994). The cumulative exergy consumption in greenhouse gases (CExCGEI), a new indicator that considers the accumulated exergy that is destroyed in greenhouse gases, is proposed.
    Keywords: Exergy; Wastes; Rice straw; Biogas; Sustainability; Renewable energy.

  • Cleaner production of purified terephthalic and isophthalic acids through exergy analysis   Order a copy of this article
    by Ali Ghannadzadeh, Majid Sadeqzadeh 
    Abstract: The purified terephthalic and isophthalic acids production process was improved through the exergy analysis approach demonstrated here. The overall exergy losses and low-exergy-efficient units were first identified and presented using visualized exergetic flowsheets. Recommendations were then proposed to reduce losses based on the main cause(s) of irreversibility. Three out of the five constituent blocks contained the highest exergy losses. The oxidation block was the main player where it was suggested that using several reactors in series with gradually decreasing temperatures could lower losses. The product refining block had the second largest irreversibilities, where improving coolers performance were recommended. The crude terephthalic acid crystallization block was the third largest loss producer (1,547 kJ/kg), where isothermal and isobaric mixing in the Solvent Dehydrator was suggested to reduce losses. The approach used in this work can be adapted to improve the energy footprint of other chemical processes.
    Keywords: sustainability; irreversibilities; purified terephthalic acid; purified isophthalic acid; process design; exergy; energy efficiency; visualized exergetic flowsheets.

  • Energy and exergy analyses of dual refrigerant system for liquefaction of natural gas   Order a copy of this article
    by Morteza Saadat-Taraghi, Shoaib Khanmohammadi 
    Abstract: Present study proceeds thermodynamic modeling, and analysis of dual refrigerant system for liquefaction of natural gas (LNG) that is one of the most important technologies in producing LNG. Using energy equations pressure, quality, enthalpy, entropy of natural gas and two refrigerants i.e. methane and propane is specified. The effects of different cycle variables on the thermodynamic performance especially the coefficient of performance (COP) is studied. Using the second law of thermodynamic for the system components, the exergy destruction rates has been found. The exergy analysis results show that heat exchanger I (HX I), heat exchanger II (HX II) and turbine have the highest exergy destruction rate. Furthermore, results indicate that the total exergy destruction rate of studied cycle for generation of 1 kg/s LNG is 2996 kW. Moreover, energy and exergy analysis shows that important parameters such as propane mass flow rate has different effects on the COP and exergy destruction rate.
    Keywords: LNG; Liquefaction; COP; exergy destruction; dual refrigerant precooling mixed.

  • Tumor Cells and Life Expectancy: an Exergy Approach   Order a copy of this article
    by Izabela Henriques, Silvio De Oliveira Junior 
    Abstract: The relation between energy and life has been under discussion for a long time and recently the concept of exergy is also being applied to analyze living organisms. In the present work, the rate of living theory and exergy analysis are gathered in order to assess the effects of cancer on life expectancy. Herein, an exergy model of a cancer cell metabolism is proposed taking into account the changes in the metabolic paths of the tumor. The results indicate a threefold increase in the rate of exergy metabolism of a cancer cell, in comparison to a healthy one. Moreover, per mole of glucose, a cancer cell obtains 8.9 moles of ATP against 32 synthetized by a healthy one. However, because of the increase in the rate of glucose uptake, the metabolic routes of the tumor are less efficient but are faster, being able to fulfill the needs of the proliferating cells. The analysis of a generic tumor progression indicates that, in the absence of treatment, the survival time would be around 3 years. Furthermore, in case of complete removal of the tumor, every six months living with the disease would lead to a reduction of almost four years in life expectancy.
    Keywords: exergy destruction; metabolism; cancer; life expectancy.

  • Interpreting Exergy Analysis as applied to Spray Drying Systems   Order a copy of this article
    by Perry Johnson, Timothy Langrish 
    Abstract: The comparison of different energy recovery systems employed on a spray dryer is challenging. This work compares two cases with a base case of a dryer alone, to identify any available improvements and interpretation of the factors used within exergy analysis, for system-wide optimisation. While exergy analysis results indicate natural gas boiler systems (Case 1) are superior to compressor-driven recovery systems (Case 2) (13% better evaporation efficiency), this paper demonstrates the significant potential to improve either system, and that dryers are one of the limiting units within the process (38% exergy improvement potential). The improvement potential for both cases is quite high (~90% of total added exergy), particularly as the inlet gas temperature increases. This paper demonstrates a method of simplifying exergy analysis to make it more accessible to engineers as a tool for optimising thermal and non-thermal systems that include a dryer as a significant part of the system.
    Keywords: Energy; Exergy; Analysis; Dryer; Vapour Recompression; Optimisation; Efficiency; Effectiveness; Drying; Exergy analysis.

  • Entropy generation effects in MHD Casson Nanofluid past a permeable stretching surface   Order a copy of this article
    by Adnan Saeed Butt, Khadija Maqbool, Syed Muhammad Imran, Babar Ahmad 
    Abstract: The primary focus of the present study is to analyse the effects of entropy generation on hydromagnetic Casson Nanofluid flow past a permeable stretching surface with convective heat and mass boundary conditions. The problem is given mathematical formulation and partial differential equations are converted into system of nonlinear ordinary differential equations by suitable similarity variables. The transformed problem is solved analytically by Homotopy-Pade method and numerically by shooting technique coupled with fourth fifth order Runge-Kutta-Fehlberg method. The results are compared with existing literature under limiting conditions and are found to be in excellent agreement. The effects of pertinent parameters on entropy generation are displayed by plotting graphs of local entropy generation number, averaged entropy generation number and Bejan number. The results are discussed in detail. It is found that magnetic field parameter, thermal Biot number and solutal Biot number have increasing effects on entropy generation whereas increase in Casson fluid parameter causes entropy production to decrease.
    Keywords: Casson Nanofluid; entropy generation; stretching sheet; convective heat and mass conditions.

  • Exergy analysis of tea drying in a continuous vibro-fluidized bed dryer   Order a copy of this article
    by Merve Ozturk, Ibrahim Dincer 
    Abstract: In the current study, a comprehensive thermodynamic investigation through energy and exergy analyses is performed to study and assess the performance of a 3-stage tea drying system which has vibro-fluid bed dryer. Also, energy and exergy efficiencies are, in this regard, investigated with the thermodynamic data obtained from the literature. A parametric study is carried out to investigate the effects of varying the state properties and operating conditions on the performance of the drying system. The overall energy and exergy efficiencies of the system are found as 42% and 7.2%, respectively. The main reason for the low exergy efficiency is the high exergy destruction rate for the components of the system. The total exergy destruction ratio of drying chambers is calculated as 58% of overall exergy destruction rate of the system.
    Keywords: Drying; Tea; Energy; Exergy; Efficiency; Vibro-Fluid Bed Dryer.

  • Exergy analysis of an industrial air separation unit for Liquefied Natural Gas production   Order a copy of this article
    by Ali Ghazikhani, Asghar Rahimi, Mojtaba Mamourian 
    Abstract: The idea of adding compressed natural gas to the main heat exchanger of an industrial air separation unit to produce liquefied natural gas in small scale is studied. The unit effectiveness is selected as the objective function to compare air separation unit and combined LNG and air separation unit. The results indicate that 1 kg/h dry air can also produce 0.013-0.027 kg/h liquid natural gas for different operating conditions of the air separation unit. Comparing with the base air separation unit, the cold box irreversibility of the combined unit reduces approximately 5-11%, while the process effectiveness increases about 35- 60% for different operating conditions.
    Keywords: Air separation unit; Liquid Oxygen; CNG; LNG; Exergy analysis; Effectiveness; Irreversibility; Combined unit.

  • Entropy Generation Rate Analysis in Pendulum Cart System Undergoing Damped Oscillation   Order a copy of this article
    by Amin A. Mohammed, M. Sunar, Ahmet Z. Sahin 
    Abstract: A mechanical system consisting of a cart with slender rod is considered in this work for entropy generation rate investigation via a thermodynamic analysis. The dynamic model of the system is formulated using Lagranges equation. Entropy generation rate is then introduced as the time derivative of the net-work potential of the system. Entropy generation rate is simulated for different initial conditions and a parametric study is performed to examine the effect of different parameters such as damping and stiffness on the entropy production. It is found that, entropy generation rate follows a pattern of three peaks being repeated with time. The stiffness and initial conditions have direct effect on the entropy generation rate. In this case, increasing either property increases entropy generation rate. The maximum EGR is found to be 0.332\times{10}^{-4} and 0.600\times{10}^{-4}\ \ W/K for nonlinear and linearized system respectively.
    Keywords: Entropy Generation Rate; Exergy Destruction; Damping; Mechanical Oscillation.

  • Entropy Generation Analysis due to Heat Transfer and Nanofluid Flow through Microchannels: A Review   Order a copy of this article
    by Krishan Kumar, Rajan Kumar, Rabinder Singh Bharj 
    Abstract: This work presents a detailed review of the entropy generation due to the heat transfer and the fluid flow through different channels. The earlier contribution of the researchers in the form of theoretical, numerical and experimental studies on the entropy generation in the conventional or microchannels with or without disruption in the flow and with or without the use of nanofluids is reviewed. The brief discussion on the microchannels, disrupted microchannels, nanofluids and entropy generation is presented. Studies performed on the channel cross-sectional shapes and rib shapes for thermal performance optimization are discussed in the paper. Nanoparticles such as Al2O3, Cu, CuO, Ag, SiO2, etc. have been used for preparing the nanofluids along with water, ethylene glycol, etc. as base fluids. Additionally, the effect of disruption in flow field on the entropy generation is also discussed. The disruptions in the form of ribs, cavities, vortex generators, etc. have been taken into account. It is hoped that this review article can provide a basis for further research on the irreversibility analysis of the nanofluid flowing through disrupted microchannels to improve the hydrodynamic and thermal performance of the system.
    Keywords: microchannel; nanofluid; ribs; entropy generation; pressure drop; heat transfer characteristics.

  • Thermodynamic performance assessment of solar based combined power and absorption refrigeration cycle   Order a copy of this article
    by Mohd Parvez, Faizan Khalid, Osama Khan 
    Abstract: Concentrated solar power technology has gained rapid pace in the area of Concentrated solar power technology has gained rapid pace in the area of sustainable energy. In recent years concentrated solar power is being appreciated worldwide as they effectively convert available solar energy to its true potential resultant energy. In this context, the principal objective of this research is to develop a model driven on solar thermal integrated with a cogeneration cycle. The effect on power generation was noted by varying parameters such as DNI, turbine inlet pressure, mass flow rate of molten salt and turbine entrance temperature was ascertained on energy and exergy efficiencies of cogenerated driven cycle. From the results it was observed, a gradual growth at turbine entry pressure ranging between 180 bar to 220 bar causes an eventual rise in first law related efficiency and exergy related efficiency of Rankine and cogeneration cycle from (31.115% to 31.44%; 42.05% to 42.56%) and (42.03% to 42.14%; 56.04% to 56.55%).
    Keywords: cogeneration; combustion cycle; exergy analysis; vapour absorption; solar energy.

  • Energy, Exergy and Environmental Analyses of a Biomass Driven Multi-Generation System   Order a copy of this article
    by Olusola Bamisile, Q.I. Huang, Mustafa Dagbasi, Micheal Taiwo, Victor Adebayo 
    Abstract: In this research, a biogas driven multi-generation system is presented. The multi-generation system consists of a gas cycle, steam cycle, absorption cycle, hot water producing chamber and hot air producing chamber. The biogas used as thermal input source is derived from agricultural waste specifically maize silage and chicken manure. Thermodynamic analysis is done with energy and exergy approach. The exergy destruction within major components of this system are also analyzed. The environmental analysis for this research focuses on the carbon emission reduction. The energy and exergy efficiency of the system respectively increases from 25.16% and 18.61% when generating electrical energy only, to 73.15% and 27.27% when multi-generating.
    Keywords: Biogas; Energy; Exergy; Multi-generation; Thermodynamics.

  • Evaluation of a Heat Recovery Steam Cycle Based on Energy, Exergy, Environmental and Economic Analyses   Order a copy of this article
    by Saeed Mohammadi, Ehsan Amiri Rad 
    Abstract: In this study, the waste heat from the chimneys of a cement factory was recovered by a steam cycle for power generation. The performance of the cycle was evaluated by a 4E analysis for both configurations with a feed water heater (FWH) (Case A) and without FWH (Case B). The results indicated that the efficiency of the cycle was decreased by installing FWH. The maximum energy and exergy efficiencies occurred when the pressure of boiler for configurations A and B were 830 kPa and 913 kPa, respectively while considering the economic analysis, the best performance occurred when the boiler pressure of each configuration were 1049kPa and 1200 kPa, respectively. Furthermore, both configurations were investigated by presenting a novel 4E objective function (4EF). For Configurations A and B, general efficient Pressure (GEP) was found, which were 1148 kPa and 1368 kPa, respectively. Also, the effects of the pinch point temperature difference were analyzed.
    Keywords: Waste heat recovery; 4E Analysis; Cement; Steam Cycle.

  • Experimental investigation of exergy performance of a water cooled hybrid photovoltaic thermal collector   Order a copy of this article
    by Nikhil Gakkhar, Manoj K. Soni, Sanjeev Jakhar 
    Abstract: In this paper, the performance of a water cooled hybrid photovoltaic thermal collector (HPTC) is evaluated by carrying out exergy analysis on the data generated through experimental investigation. For the experimentation, a hybrid HPTC was designed and fabricated which would provide combined electric and thermal energy. The field testing was carried out at different mass flow rates, collectively ranging from 0.083 kg/s to 0.116 kg/s in different configurations during peak summer period. The exergetic investigation was carried out to identify exergy losses, exergy destruction and exergy efficiency of the system. The exergy efficiency of the system was calculated using three different scenarios taken from the literature. The Scenario (I) was taken by excluding exergy losses and Scenario (II) was considered by taking exergy losses and destruction. Both the Scenario were compared with Scenario (III), which considered exergy destruction only and it was found out that the exergy efficiency obtained in Scenario (III) was more than the other two scenarios and ranged between 48.55% to 61.36%, 41.44% to 55.85% and 35.09% to 48.16% for fixed inner tube flow rate of 0.091 kg/s and varying annulus mass flow rate of 0.008 kg/s, 0.017 kg/s and 0.025 kg/s respectively. It was also found out that exergetic efficiency was a function of mass flow rate of cooling water at a given solar radiation. The proposed system may be helpful in providing combined heat and power for semi-arid regions of Rajasthan, India.
    Keywords: Exergy; Solar energy; CPV/T; Hybrid system; Water cooling.

  • Energetic and Exergetic Performance of NH3-H2O based Absorption Refrigeration Cycle: Effect of Operating Factor   Order a copy of this article
    by Gorakshnath Takalkar, Rahul Bhosale, Nilesh Mali, Sunil Bhagwat 
    Abstract: One of the major objectives while designing the vapor absorption refrigeration system (VARS) is to acquire the better performance within the accessible heat source and sink temperature limit. In this paper, attempts are made to identify the temperature limit for the optimization of a single stage ammonia water (NH3-H2O) absorption-refrigeration system (AAR) by performing a thermodynamics analysis by applying both first and second law of thermodynamics. To estimate the potential of utilization of a low-grade heat energy, operating factor (R) is considered towards optimizing the energetic (COP) and exergetic COP (ECOP). The simulated COP and ECOP results are expended to predict the feasibility and optimum operating region for an AAR cycle in terms of the R and various operating temperature such as T_(gen ), T_(abs ), T_(cond ), T_(e ,) The R determined in this study (based on the optimization of ECOP and COP) covers a wide range of applications i.e., from deep-freezing (253.15 K) to air conditioning (283.15K) and from water-cooling (303.15 K) to air cooling (318.15 K). Resulted optimum COP (for R in the range of 1.5 to 1.85) and ECOP (for R in the range of 1.3 to 1.5) specifies better selection criteria for available heat source and sink temperatures limits for evaporation temperatures from 283.15 K to 253.15 K.
    Keywords: Ammonia Absorption Refrigeration; Solar energy; low-grade energy utilization; and Exergy performance; Operating factor.

  • Exergetic Analysis of Human Respiratory System Including Effect of Age and Gender   Order a copy of this article
    by Abhijit Dutta 
    Abstract: In this paper, an attempt has been made to analyze the exergetic efficiency of human respiratory system and quantify the change in exergetic performance involving the effects of ambient temperature change, hypothermia, hyperthermia, age and gender during the respiration process. The analysis considers an air flow rate of 2.04
    Keywords: Exergetic efficiency; respiratory system; hypothermia; hyperthermia; physiological condition; Hb.

  • Organisms live at far-from-equilibrium with their surroundings while maintaining homeostasis, importing exergy and exporting entropy   Order a copy of this article
    by Cennet Yildiz, Volkan Adem Bilgin, Bayram Yilmaz, Mustafa Özilgen 
    Abstract: Homeostasis means maintenance of internal constancy of the critical physiological parameters of the organisms, such as energy, water, pH, ion concentration, oxygen and temperature to sustain their living state. Organisms are far-from-equilibrium systems and die when they come equilibrium with their environment. Homeostasis is achieved via steady state material and energy fluxes between the organism and its environment to maintain the constancy of the homeostatic properties at far from equilibrium. Cannon wrote about homeostasis in 1920s, Prigogines Nobel-winning theory suggested in 1940s that the dissipative systems import energy and export entropy to be able to survive. Schr
    Keywords: Far-from thermodynamic equilibrium state; energy and entropy fluxes; homeostasis; steady state.

  • Thermoeconomic assessment of a waste heat recovery system driven by a marine diesel engine for power and freshwater production   Order a copy of this article
    by Yadollah Aghdoud Chaboki 
    Abstract: To develop eco-friendly ships, an integrated system with power and fresh water production capabilities is proposed to recover marine engine waste heat. Marine engine, multi-effect desalination unit and organic Rankine cycle are the main elements of the proposed system. The new multi-generation cycle is modeled in energy, exergy and economic aspects. The modeling results for the base case showed that the suggested cycle is capable of 387.95 kW power and 7.04 m3/hr. Additionally, the influences of different major parameters on the performance of the system is investigated and illustrated. Two-objective optimization (total cost rate and second law efficiency were objectives) is performed to determine the optimal values of five decision variables are obtained. An optimal condition with the total cost rate of 2.54 $/hr and exergy efficiency of 35.96% is introduced as the best trade-off solution.
    Keywords: Thermoeconomic; Waste heat recovery; Marine engine; Organic Rankine cycle; Multi-effect desalination (MED).

  • Dynamic reference environment for exergy: a trigeneration system case study   Order a copy of this article
    by Wojciech Kostowski, Wodzis?aw Piekarczyk 
    Abstract: The paper discusses the problem of reference temperature for exergy calculation using an example of a combined cold, heat and power unit integrated with biomass gasification. Depending on the ambient temperature and the demand for heating and cooling, several modes of operation are considered. The performance of the system is evaluated by exergy analysis for various reference temperatures. First, the annual average temperature of 8.5 C is applied. Then, monthly variation of the reference temperature between 0.5 and 18.6C (Katowice, Poland) is considered. It has been shown that a constant reference temperature yields misleading results with numerical error between 5% for high-temperature media to almost 90% for cooling agents, in particular for cooling agents, where the useless return water has apparently more exergy than the cold ice water. In conclusion, a variable reference temperature is recommended for exergy analysis of systems including cooling or low-temperature heating agents.
    Keywords: exergy; reference environment; CCHP; biomass; gasification; internal combustion engines; absorption chiller; steam engine.

  • Exergoeconomic Pricing Strategy of Crude Oil Gathering and Transportation System   Order a copy of this article
    by Cheng Qinglin 
    Abstract: Taking a typical oil transfer station in eastern China as an example in this paper, exergy economics theory in algebraic pattern is applied to the energy system of the oil transfer station on the basis of the exergy analysis. By analyzing the cost structure of each equipment and unit, exergy economics equilibrium equation in algebraic pattern can be established. Two different cost allocation methods, extraction method and energy level method, are introduced into the auxiliary equation. Combined with the principle of exergy loss pricing, the unit cost of each exergy loss is calculated. The results show that the energy level method can effectively distinguish the changes of energy quality, which is more suitable for the economic pricing strategy of the oil transfer station gathering and transportation system, and provides a more scientific and effective method and basis for the energy-saving transformation of the oil field gathering and transportation system.
    Keywords: crude oil gathering and transportation system; cost structure; cost allocation method; the cost of exergy economics.

  • Exergy and exergoeconimic analysis and multi-criteria optimization of 1 MW installed CCHP system (a case study in Kashan University)   Order a copy of this article
    by Saber Khanmohammadi, Shoaib Khanmohammadi, Hossein Khorasanizadeh 
    Abstract: The present study deals with exergy and exergo-economic evaluation of a 1 MW combined cooling, heat and power (CCHP) system, composed of a natural gas prime mover internal combustion engine located in the main campus of the University of Kashan, in Kashan, Iran. To retrieve the thermal energy from exhaust gas of the engine and the heat removed by the engine jacket water, shell and tube heat and plate heat exchangers have been incorporated, respectively. The refrigeration unit of the system is consisting of a Li-Br absorption chiller with refrigeration capacity of 200 refrigeration tones (RT). Using appropriate linking between Engineering Equation Solver (EES) and Matlab software, thermal and economic modeling and muti-criteia optimization (MCO) have been performed. A novel approach of the current study is consideration of technical and economical viewpoints simultaneously and applying a multi-objective optimization to find the optimum operating parameters of an installed CCHP system. The optimization results showed that the minimum total exergy destruction rate occurs for the exhaust gas extraction factor of 0.68 which causes 33.52 $/h total cost rate. For this case, among all of the system components the most exergy destruction rate of 1700 kW belongs to the engine. In addition, the results of the genetic algorithm based multi-objective optimization represented that the optimization causes 2.68 $/h decrease in total cost rate and reduction of 4512 kW in exergy destruction rate.
    Keywords: Combined cooling; heat and power; Exergy analysis; Thermoeconomic; Multi-criteria optimization.

  • A comparative assessment of SPECO and MOPSA on costing of exergy destruction   Order a copy of this article
    by Cuneyt Uysal, Dilek Ozen, Huseyin Kurt, Ho-Young Kwak 
    Abstract: This paper presents the comparison of Specific Exergy Costing (SPECO) and Modified Productive Structure Analysis (MOPSA) method to test their abilities on costing of exergy destruction. MOPSA method is applied to a combined supercritical CO2 regenerative cycle and organic Rankine cycle using zeotropic mixtures for gas turbine waste heat recovery system. The results obtained with applying SPECO method to the system are taken from literature. The exergy destruction cost rate of overall system is obtained to be 86.08 $/h and 1113.13 $/h for MOPSA and SPECO methods, respectively. The exergoeconomic factor of overall system is found to be 31.88% for SPECO method, while this value is found to be 85.82% for MOPSA method. The obtained results with applying MOPSA method for exergy destruction cost rate are significantly lower and more consistent compared to the results obtained by SPECO method.
    Keywords: SPECO; MOPSA; Thermoeconomics; Exergy Destruction; Organic Rankine Cycle; Supercritical Cycle.

  • Energy and Exergy Analysis of a PV/Thermal Storage System Design Integrated with Nano-enhanced Phase Changing Material   Order a copy of this article
    by Alper Ergün 
    Abstract: Nanotechnology and heat storage applications are among the most popular fields of the researchers in recent years. In this study, three different CPV/T systems were analyzed experimentally under the same conditions for four days. While no modifications on the CPV were made in the first system, the rear of the panel used in the second system was covered with a phase-changing material (PCM). In the third system, together with PCM, nano-sized aluminum oxide (Al2O3) particle in a weight percentage of 5% was added into the system (namely, nano-enhanced PCM). The experimental analysis revealed that 8% more power output and module efficiency were obtained from the system with the PCM and the nano-enhanced PCM compared to the normal system. These systems which were also designed with a heat storage have an average of 42W thermal energy gain. As the exergy analysis results show, the exergy destruction of the system with the nano-enhanced PCM was found to be lower than that of the PCM system, while exergy efficiency was found to be 14% higher in the former system.
    Keywords: Nano-enhanced PCM; heat storage; CPV; photovoltaic-thermal.

  • Thermodynamic analysis of a gasifier- based coal-to fuel cogeneration system   Order a copy of this article
    by Mathkar A. Alharthi, Abdul Khaliq, Mohammad Luqman 
    Abstract: This paper attempts to carry out a thermodynamic analysis of a cogeneration system composed of a coal gasifier, a gas turbine cycle, and a heat recovery steam generator within the meaning of the first and second law of thermodynamics. For this purpose a thermodynamic model has been developed where the syngas and combustion products are considered as the mixture of various gaseous species and the variation in specific heat with gas composition and temperature is accounted. The analysis aims in particular to examine the influence of the pressure ratio, turbine inlet temperature and pinch point on the performance of cogeneration system. Results show that increasing the gasifier pressure leads to decrease the first law efficiency of cogeneration but it provides a small gain in its second law efficiency. Both first and second law efficiencies of cogeneration decrease with increasing the pinch point temperature, however, the increase of pinch point temperature involves a significant rise of power to heat ratio. A considerable improvement in the performance parameters of cogeneration is observed with the rise of turbine inlet temperature. Entropy generation evaluated after the application of second law reveals gasifier as the most irreversible component of cogeneration where 28607 kW of irreversibility rate is found. Irreversibility rates of 5994 kW and 2597 kW are observed to be in the combustion chamber and HRSG. Increasing the gasifier pressure lead to decreased the first law efficiency of cogeneration but provide a small gain in its second law efficiency.
    Keywords: Coal gasifier; syngas; cogeneration; entropy generation.