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International Journal of Exergy

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 International Journal of Exergy (32 papers in press) Regular Issues Experimental Investigation of Phase Change Material Utilization Inside the Horizontal Mantled Hot Water Tank   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   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   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. Cleaner production of purified terephthalic and isophthalic acids through exergy analysis   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   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   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   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   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 an industrial air separation unit for Liquefied Natural Gas production   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   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   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   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   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   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   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   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   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   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   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 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 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) 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 $/h decrease in total cost rate and reduction of 4512 kW in exergy destruction rate. Keywords: Combined cooling; heat and power; Exergy analysis; Thermoeconomic; Multi-criteria optimization. A comparative assessment of SPECO and MOPSA on costing of exergy destruction by Cuneyt Uysal, Dilek Ozen, Huseyin Kurt, Ho-Young Kwak Abstract: This paper presents the comparison of Specific Exergy Costing (SPECO) and Modified Productive Structure Analysis (MOPSA) method to test their abilities on costing of exergy destruction. MOPSA method is applied to a combined supercritical CO2 regenerative cycle and organic Rankine cycle using zeotropic mixtures for gas turbine waste heat recovery system. The results obtained with applying SPECO method to the system are taken from literature. The exergy destruction cost rate of overall system is obtained to be 86.08$/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   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   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. Exergy analysis of district energy systems and comparison of their exergetic, energetic and environmental performance   by Ehsan Ahmadian, Ralf-Roman Schmidt Abstract: This paper investigates the advantages of performing exergy analysis for thermodynamic systems consisting of a district heating network (DHN) by comparing the exergy performance with energetic and environmental performance of three case studies in Austria. Furthermore, the effect of influential parameters such as energy source type, conversion technology, supply/return temperature and reference temperature on exergy performance of the system was investigated. An initial literature review and analysis of the case studies showed that the most influential factor on exergy performance of a system was the type of energy source and its conversion technology. Although lowering the supply temperature of DHN can increase the exergy efficiency of the system, changing reference temperature did not show a clear relationship with exergy efficiency. Finally, no clear relationship between energy and exergy efficiencies of the system was discovered; nevertheless, the higher the exergy efficiency of a system the lower the direct CO2 emissions from it. Keywords: exergy analysis; thermodynamic systems; exergy indicators; district heating network; energy efficiency; CO2 emissions. Comparative Energy and Exergy Analysis and Optimization Study on the Supercritical CO2 Recompression Power Cycle   by Emrah Gumus, Veysi Bashan Abstract: The current study aims at optimization and comparing the recuperative s-CO2 cycle with the re-compression s-CO2 cycle in case of changes in turbine and compressor isentropic efficiency and TITs. Below 317 ? the TIT recuperated Brayton cycle (RBC) has a higher cycle efficiency than RCBC for the case where compressor efficiency is 75% and turbine efficiency is 80%. RBCs with having higher turbomachinery efficiencies (?c=85%, ?t=90%) have higher cycle thermal efficiency than RCBCs with lower turbomachinery efficiencies (?c=75%, ?t=80%). These results will remedy the gap in the literature on information for selecting the appropriate cycle for various purposes under certain thermodynamic inlet conditions. Keywords: Recompression Cycle; Supercritical; s-CO2; Carbondioxide; Thermodynamic analysis; Exergy analysis. Energy and Exergy Analysis of Transcritical CO2 Two Stage Compression Cycle   by Hongli Wang, Jingrui Tian, Yitai Ma Abstract: Based on theoretical analysis and experimental testing, the performances of transcritical CO2 two stage compression cycle with two gas coolers were analyzed. The maximum experimental refrigeration COPc and heat COPh are 2.24 and 3.25, the maximum theoretical COPc and COPh are 2.85 and 3.85. The COP both of COPc and COPh decrease gradually with increasing of the outlet temperature of gas cooler, and the average value of experimental COPc and COPh are 2.02 and 3.13, the average value of theoretical COPc and COPh are 2.54 and 3.54. Range of the evaporating temperature from -5? to 17?, the average value of experimental COPc and COPh are 1.99 and 3.17. The exergy loss both of theoretical value and experimental value are all increase gradually with increasing of differential pressure of throttling valve. The error of exergy loss percentage on theoretical calculation and experimental testing are almost all within +20% and -20%. Keywords: Transcritical CO2 two stage compression cycle; Theoretical analysis; Experimental testing; Energy analysis; Exergy loss. Second-Law Thermodynamic Analysis on Premixed Syngas Flames   by Yusen Liu, Dong Han Abstract: Exergy destructions in laminar premixed flames of syngas with varied fuel compositions, i.e. H2 and CO percentages, were numerically studied at both 1 atm and 5atm. Two syngas compositions, namely 30% H2/70% CO and 70% H2/30% CO, were selected for calculation. The processes causing exergy destructions were separated into heat conduction, mass diffusion and chemical reactions, and the chemical reactions were found the most dominant, followed by heat conduction and mass diffusion. With hydrogen enrichment, the proportion of total exergy destruction was increased by about 1%, but nearly unchanged with pressure elevation. Specifically, with hydrogen enrichment in syngas, the exergy destruction from heat conduction decreased mainly because the flame thickness was narrowed down, and that from mass diffusion increased as a result of high diffusivity of H2, H and H2O, whereas that from chemical reactions increased due to the higher reactivity of H2 than CO. In contrast, the pressure elevation had a more significant impact on the enhancement of exergy destruction rates and reduction of flame thickness. The higher temperature gradient and mole fraction gradients were dominant in the increased exergy destruction from heat conduction and mass diffusion, but the reduction of flame thickness resulted in that the exergy destruction from chemical reactions decreased. Keywords: Second Law of Thermodynamics; Premixed flame; Syngas; Hydrogen. Effect of biodiesel Blending with Diesel Fuel on CI Engine Performance and Energy Availability   by Jehad Yamin, Eiman Sheet Abstract: Abstract. This paper discusses the effect of blending waste cooking oil biodiesel with diesel on the performance, emissions and engine availability of 4-stroke, direct injection diesel engine. This was done using both experimental and analytical methods. The software used was Diesel-RK. rnFirst, the engine was tested using locally available diesel in Jordan to set the baseline performance for comparison and then was run using other fuels and blends. rnFinally, the first and second law parameters were calculated and compared. It was found that 5-10% biodiesel blend gave an average of 5% improvement in the performance from power, torque, fuel consumption and thermal efficiency point of view. rnFurther, it was clear from second law analysis that biodiesel fuel and its blends higher than 10% failed to utilize the available energy of the fuel compared with diesel fuel. Keywords: Second law analysis; engine availability; biodiesel fuel; diesel engine performance; exergy analysis; WCO Biodiesel; engine availability. Performance evaluation of compressor assisted multi-effect absorption refrigeration cycles for power and cooling using evacuated tube collectors.   by Chinedu Frank Okwose, Muhammad Abid, Tahir Abdul Hussain Ratlamwala Abstract: To improve the thermal energy utilization performance of an absorption cycle, compressor-assisted single, double and triple effect absorption refrigeration cycles for power and cooling are proposed in this study. Solar thermal energy from evacuated tube collectors is used as the heat source to drive the cycles. The power generated by the cycles is used to power the compression required to enhance the performance of the cycles. Based on the laws of thermodynamics, the effective energy efficiency and effective exergy efficiency were carried out to study the effect of the heat source temperature (ths,in) and the compression ratio (prcom) on the proposed cycles. In the base case of the proposed cycle (prcom=1.5), the simulation results show that the net power output decreased by 88%, while the cooling output increased slightly by 5.2% for the single effect cycle. The effective energy efficiency decreased from 14% to 13% and the effective exergy efficiency increased from 61% to 66% respectively. A further analysis of multi-effect cycles showed that the system can be operated at low temperatures, with the desorber temperature of double effect cycle decreasing by 32% while the desorber temperature for triple effect cycle decreases by 23% for a compression ratio of 1.5. Keywords: Absorption refrigeration; compression ratio; power; multi-effect cooling; double-output; evacuated tube collector. EXERGY ANALYSIS OF MICROCHANNEL HEAT EXCHANGERSby Mehmed Rafet Özdemir Abstract: This study investigates the exergetic efficiencies of plain microchannel heat exchangers under single-phase and two-phase operating conditions using de-ionized water as the working fluid. The friction factor and heat transfer coefficient data of microchannels are obtained using experimental studies from the literature and analytical/empirical correlations. The exergetic efficiencies of four plain microchannels are compared in order to reveal the effect of different geometrical parameters in terms of exergetic efficiency. The results showed that the microchannel aspect ratio (width/height) is an insignificant parameter on the exergetic efficiency for single-phase flow conditions. However, the exergetic efficiency increased with the decreasing of the microchannel aspect ratio in two-phase tests. On the other hand, the microchannel heat exchanger having shorter heated length exhibited better exergetic efficiency both in single-phase and two-phase regimes compared to the microchannel heat exchanger with longer heated length. Keywords: microchannel heat exchanger; exergy analysis; single-phase flow; two-phase flow.