International Journal of Exergy (11 papers in press)
EXTREMELY SMALL ENERGY REQUIREMENT BY POLIOVIRUS TO PROLIFERATE ITSELF IS THE KEY TO AN OUTBREAK OF AN EPIDEMIC
by Mustafa Ozilgen, Sevgi Eylul Ferahcan, Ayse Selcen Semercioz
Abstract: Poliovirus is an RNA virus which proliferate itself in the intestines. Thermodynamic assessment of the proliferation process has been assessed after calculating the energy and exergy of the RNA with the group contribution method. Mass, energy and exergy balances are performed to calculate the energy and exergy exploited from the host cell as 4.65x10-19 and 3.35x10-17 kJ, respectively. In a typical epidemic in 1988, 350,000 cases were reported, implying that the total of 1.627x10-9 kJ of energy 1.174x10-7 kJ of exergy were exploited from them during the epidemic. Although the energy and exergy efficiency of virus generation in a host cell were very small, e.g., 1.376 x 10-6 and 9.78 x 10-5, respectively; energy and exergy employed in this process was very small implying that extremely small energy and exergy requirement by poliovirus to proliferate itself is the key to an outbreak of an epidemic.
Keywords: Virus; epidemic; energy; exergy; devastation of the host cells.
Energy and Exergy Analyses of Al2O3-diesel-biodiesel Blends in a Diesel Engine
by Hakan Ozcan
Abstract: The usage of nanoparticles as a fuel additive to improve fuel economy and reduce harmful exhaust emissions has been a popular research topic in recent years. The effects of biodiesel (5% in volume) and aluminum oxide (Al2O3) nanoparticles (50 ppm and 100 ppm) addition to pure diesel on the energy and exergy analysis of a diesel engine were investigated in this experimental study. The experiments were carried out at variable engine loads (25%, 50%, 75%, and 100%) and constant engine speed at 1500 rpm. The results of this study showed that the biodiesel addition increased the brake specific fuel consumption (BSFC) while decreased slightly the brake thermal efficiency (BTE). As well as, the heat loss from cooling water increased, whereas the unaccounted heat loss, the engine brake power, and the heat loss by exhaust gases reduced. On the other hand, the addition of Al2O3 nanoparticles at a rate of 50 ppm and 100 ppm to biodiesel-pure diesel blend increased the BTE, and the exergy efficiency by 8.15% and 7.28%, averagely. Further, BSFC, entropy generation, and unaccounted losses decreased by 7.57%, 13.49%, and 31.89 % averagely.
Keywords: Al2O3; Biodiesel; Energy Analysis; Exergy Analysis; Combustion.
Thermodynamic examination of a novel solar-thermochemical based integrated system for multi-generation
by Guliz Onder, Fatih Yilmaz, Murat Ozturk
Abstract: In this paper, a thermodynamic examination of novel solar-thermochemical based integrated system is investigated for multi-generation purpose. The investigated multigeneration system consists of six sub-systems, namely solar dish collector (SDC), double stage-organic Rankine cycle (DS_ORC), organic Rankine cycle (ORC), single effect absorption cooling (SEAC), hybrid magnesium chlorine (Mg-Cl) thermochemical system, and hydrogen liquefaction system. In this regard, the parametric study is given to investigate how the overall performance and exergy destruction rate of integrated-system are affected by way of various factors, such as references temperature, solar irradiation. Moreover, the overall energetic, exergetic efficiencies and total exergy destruction rate of integrated-system are investigated. The exergy destruction rate and exergy efficiency of Mg-Cl thermochemical system are found to be 12,400 kW and 43.85%, respectively. Furthermore, the energy and exergy efficiencies of overall integrated-system are calculated as 54.17% and 50.46%, respectively.
Keywords: solar energy; thermochemical cycle; multi-generation; hydrogen; energy; exergy.
Energy and exergy analyses of a HCCI engine based system running on hydrogen enriched wet-ethanol fuel
by Shahid Islam, Ibrahim Dincer, Abdul Khaliq
Abstract: In this paper, the investigation of thermodynamic performance of a hydrogen enriched wet-ethanol fueled homogenous charge compression ignition (HCCI) engine is conducted through energy and exergy methodologies. The energy and exergy analyses are performed through a thermodynamic model by considering the gas composition formed after the combustion process. The energy and exergy efficiencies of the system increase from 41.56% to 44.01% and from 37.23% to 38.73%, respectively, with the increase in hydrogen energy share from 5% to 20% in the air-fuel mixture. The energy and exergy efficiencies of the system are found to be increasing with an increase in the pressure ratio of turbocharger and compressor polytropic efficiency. The increase in the ambient temperature results in the decrease in both energy and exergy efficiencies. The detailed exergy analysis of the system reveals that the highest amount of exergy destruction is associated with HCCI engine and the maximum available work increases with the increase in the hydrogen percentage.
Keywords: Exergy; Energy; Efficiency; Hydrogen; Ethanol; HCCI; Combustion.
Designing and Exergetic Analysis of a Solar Power Tower System for Iskenderun Region
by Hüseyin Yağlı, Cuma Karakuş, Yıldız Koç, Mehmet Çevik, İrem Uğurlu, Ali Koç
Abstract: In this paper, a steam cycle assisted solar tower power system is designed and parametrically optimised for Iskenderun region by considering the weather conditions. After the optimisation, exergy-based analysis of the compounds and overall plant is performed for the best-performing cycle conditions. As a result of the annual based monthly parametric optimisation, the design parameters, working performance, energy and exergy efficiencies of system are compared to obtain the best-performing cycle conditions which is found in July at the tower outlet pressure and temperature of 100 bar and 1000
Keywords: solar power tower (SPT); steam cycle; parametric optimization; energy analysis; exergy analysis.
Towards a better understanding of energy systems using emergy-based exergoeconoenvironmental analysis
by Mortaza Aghbashlo, Marc A. Rosen
Abstract: This paper introduces emergy-based exergoeconoenvironmental analysis, a new methodology for improved understanding of energy systems through simultaneous consideration of thermodynamic, financial, and ecological criteria. A new parameter called exergetic ecological emergy/financial emergy ratio is first introduced. This parameter is then used for deriving emergy-based exergoeconoenvironmental balances for an energy system by combining it with exergy cost concepts. The exergetic ecological emergy/financial emergy ratio for all exergy streams of the system is determined using the SPECO approach. The developed approach is applied to a simple cogeneration system of power and steam to demonstrate its general applicability and robustness. The outcomes of the developed method herein are assessed in comparison with those of emergy-based exergoeconomic and exergoenvironmental methods. Overall, the highest total exergetic ecological emergy/financial emergy ratio (13.0841 sej/sej) is observed in the heat-recovery steam generator followed by the air preheater (10.0379 sej/sej). Even though both emergy-based exergoeconomic and exergoenvironmental methods give the improvement priority first for the combustion chamber, the heat-recovery steam generator is suggested by emergy-based exergoeconoenvironmental analysis. Generally, the hybrid framework developed here appears to be a promising complement to available exergy-based techniques for systematically developing thermodynamically, financially, and ecologically conscious energy systems.
Keywords: Emergy; Exergoeconoenvironmental analysis; Specific exergy costing; Exergy cost .
Energy and Exergy Analyses of Paddy Drying Process in a Vertical Fluidized Bed Dryer
by Binayak Pattanayak, Siba Shankar Mohapatra, Harish Chandra Das
Abstract: This research article focuses on the energy and exergy analysis of paddy drying using Fluidized bed dryer. The energy analysis of paddy drying process is conducted using First law of thermodynamics. The parameters Energy Utilization (EU) and Energy Utilization Ratio (EUR) are determined from the first law analysis. Similarly, second law of thermodynamics is used for the exergy analysis of paddy drying. Exergy analysis is conducted with the help of the parameters like exergy evaporation rate, exergy destruction and exergetic efficiency. Specific Moisture Extraction Rate (SMER) is determined to get the value of moisture vaporization rate per energy consumed for drying. Paddy grains are dried in a batch of 2 kg and 3 kg at 400C, 500C temperature of drying air and drying air velocity of 2 and 3 m/s. From the analysis it is observed that EU, EUR, SMER and exergy destruction decreased and exergetic efficiency increased with drying time. The exergy evaporation rate first increases to a certain value from zero and then decreases continuously. The exergetic efficiency varies from 12.37% to 86.25% whereas EU and EUR varied from 55 J/s to 549 J/s and 0.087 to 0.656 respectively.
Keywords: Energy; Energy Utilization; Energy Utilization Ratio; Exergy; Exergy Destruction; Exergetic Efficiency.
Theoretical investigation of entropy generation effects in nanofluid flow over an inclined stretching cylinder
by Adnan Butt, Asif Ali, Muhammad Nazim Tufail, Amanullah Dar
Abstract: Laminar incompressible boundary layer flow and heat transfer of nanofluid over an inclined stretching cylinder is considered and the entropy effects are theoretically examined during the phenomena. The problem is mathematically modelled and nonlinear partial differential equations are attained. With the help of suitable similarity transformations, these partial differential equations are transformed into nonlinear ordinary differential equations which are numerically solved by utilizing shooting technique with fourth-fifth order Runge-Kutta method. The results obtained are compared with the previously existing literature by considering certain limiting cases. The influence of physical parameters on flow, heat transfer and concentration of nanoparticles are analyzed qualitatively with the use of graphs and tables. Furthermore, the impact of various physical parameters on local entropy generation number and averaged entropy generation number are also presented through graphs. A detailed comprehensive study has been carried out of the problem.
Keywords: Inclined stretching cylinder; nanofluid; entropy generation; mixed convection.
Energy and Exergy Analyses of a Novel Solar PTC Assisted Multi-Generation System
by Olusola Bamisile, MUSTAFA DAGBASI, SERKAN ABBASOGLU
Abstract: In this study, a solar assisted multigeneration system is presented. The exergy and energy performance analyses is the objective of this research. The multigeneration system consists of two Rankine cycles, two absorption cycles and a hot water tank. Solar parabolic trough collectors are used to generate thermal energy from the sun which in turn is used to power the system. The multi-generation system achieves an energy and exergy efficiency of 77% and 49% respectively without solar input. Considering the solar PTC, the efficiencies respectively are 57% for energy and 40% for exergy. The COPs for the absorption cycle and other findings from the study are presented in details in the full paper. Exergy destruction in major components are calculated and parametric studies are done to check the performance of the system under varying global solar irradiance conditions.
Keywords: Absorption cycle; Energy; Exergy; Parabolic Trough Collectors; Rankine cycle; Solar.
Performance evaluation of a mobile air conditioning unit:an exergetic approach
by Huseyin Gunhan Ozcan, Arif Hepbasli, Huseyin Gunerhan
Abstract: This study considers a public bus (having a capacity of 99 passengers and a volume of 69 m3) along with its vapor compressed mobile air conditioning (MAC) unit (utilizing R134a as a refrigerant) together as a low exergy (so-called LowEx) system. The LowEx analysis, which has been mostly applied to buildings, and conventional exergy analyses method are utilized together (coupled up analysis method) to assess the performance of this system for the first time to the best of the authors knowledge. Based on the LowEx analysis, total exergy efficiency and exergy flexibility factor are calculated to be 11.92% and 0.56 for the heating mode and 3.41% and 0.19 for the cooling mode, respectively. Furthermore, through on the conventional exergy analyses, the highest exergy efficiency belongs to condenser with 93.08% in the cooling mode, while it is 93.20% for the water heat exchanger in the heating mode, respectively.
Keywords: LowEx; conventional exergy; public bus; mobile air conditioning; heating and cooling.
Exergy Analysis and Assessment of Performance Criteria for Compressed Air Energy Storage (CAES) Concepts
by Friederike Kaiser, Uwe Krüger
Abstract: Compressed Air Energy Storage (CAES) power plants provide positive and negative power reserves to compensate for an increasing share of intermittent renewable electric energy generation from wind and solar power stations. The compressed air is stored to drive a very efficient open gas turbine. However, enthalpy, a measure of the energy content of compressed air, is close to zero at ambient air temperatures. This indicates that enthalpy underestimates the ability of compressed air to do work and implies low storage efficiencies of the CAES open gas turbine cycle. Thus, in this project, the characterization of different CAES concepts based on exergy in contrast to enthalpy is discussed, including the fuel-driven CAES plants Huntorf and McIntosh and forthcoming concepts.
The CAES energy efficiency defined as caes = Wel,G/(Wel,M + Qfuel), resulting in approximately 42 % for Huntorf and 54 % for McIntosh, is unsuitable for characterizing CAES as an electrical energy storage. Instead, an alternative Round Trip Energy Efficiency rt4 is presented, which can be split up into a compression conversion efficiency cc and a turbine conversion efficiency tc. An exergy-based counterpart is deemed ideal to evaluate the storage properties of CAES. However, the enthalpy-based tc emphasizes the efficient generation characteristics of fuel-driven CAES technology (e.g. McIntosh with over 82 % fuel efficiency of the turbine process as compared to a Carnot value of 75 %).
Keywords: Compressed Air Energy Storage; CAES; Huntorf; energy storage efficiency; exergy; steady state thermodynamics; performance criteria; comparison.