International Journal of Exergy http://www.inderscience.com/browse/index.php?journalID=135&year=2012&vol=10&issue=1 Inderscience Publishers Ltd en-uk International Journal of Exergy 1742-8297 1742-8300 © 2012 Inderscience Publishers Ltd editor@inderscience.com https://www.inderscience.com/images/files/coverImgs/ijex_scoverijex.jpg http://www.inderscience.com/browse/index.php?journalID=135&year=2012&vol=10&issue=1 http://www.inderscience.com/link.php?id=45058 The method presented in this paper gives not only the availability loss in each elementary step of the whole process in the engine, but also an insight into how big is the part of burnt fuel available during an elementary piston motion, something which cannot even theoretically be realised as pΔV work. This method is based on decomposition of a complex real process to so-called elementary processes equivalent to the real one. Practical applications of the decomposition method favour antecedence plotting of special u-s diagrams for combustion products. Decomposition method as a new type of second law analysis of the combustion process of internal combustion engines
Neven Ninić; Mirko Grljušić; Maro Jelić
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 1 - 20
The method presented in this paper gives not only the availability loss in each elementary step of the whole process in the engine, but also an insight into how big is the part of burnt fuel available during an elementary piston motion, something which cannot even theoretically be realised as pΔV work. This method is based on decomposition of a complex real process to so-called elementary processes equivalent to the real one. Practical applications of the decomposition method favour antecedence plotting of special u-s diagrams for combustion products.

]]> 10.1504/IJEX.2012.045058 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 1 - 20 Neven Ninić; Mirko Grljušić; Maro Jelić Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Department of Mechanical Engineering and Naval Architecture, University of Split, R. Boškovića b.b., 21000 Split, Croatia. ' Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Department of Mechanical Engineering and Naval Architecture, University of Split, R. Boškovića b.b., 21000 Split, Croatia. ' Marine Department, University of Dubrovnik, Cira Carica 4, 20000 Dubrovnik, Croatia internal combustion engines second law analysis availability loss u-s diagram decomposition method thermodynamics combustion process burnt fuel piston motion. 2012-01-24T23:20:50-05:00 10 1 1 20 2012-01-24T23:20:50-05:00 http://www.inderscience.com/link.php?id=45057 The exergy change of the surroundings of exhaust-gas emitting ports, and its probable effects on the atmosphere, are investigated and the current stable state changing point of the atmosphere is determined. The potential for doing work is described and the effects of the amount of exhaust gas on the atmosphere are studied through calculation and analysis of an exergy-change function, which is nonlinear and dynamic. This function accounts for the flow direction of the exhaust gas in the absence of a local wind. It appears that exergy can be used as a state function to describe the change, the stability and the order of a system. Analysing the effects on the atmosphere of exergy changes due to exhaust-gas emissions
Yongan Ao; Yueren Wang; Marc A. Rosen
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 21 - 33
The exergy change of the surroundings of exhaust-gas emitting ports, and its probable effects on the atmosphere, are investigated and the current stable state changing point of the atmosphere is determined. The potential for doing work is described and the effects of the amount of exhaust gas on the atmosphere are studied through calculation and analysis of an exergy-change function, which is nonlinear and dynamic. This function accounts for the flow direction of the exhaust gas in the absence of a local wind. It appears that exergy can be used as a state function to describe the change, the stability and the order of a system.

]]> 10.1504/IJEX.2012.045057 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 21 - 33 Yongan Ao; Yueren Wang; Marc A. Rosen Faculty of Civil and Environmental Engineering College, Shenyang Jianzhu University, Shenyang, Liaoning 110168, China. ' Faculty of Civil and Environmental Engineering College, Shenyang Jianzhu University, Shenyang, Liaoning, 110168, China. ' Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4, Canada exergy analysis exhaust gases atmosphere exergy change function nonlinear exhaust emissions air pollution. 2012-01-24T23:20:50-05:00 10 1 21 33 2012-01-24T23:20:50-05:00 http://www.inderscience.com/link.php?id=45059 Critical insulation thickness is known to refer to the insulation thickness that maximises the rate of heat transfer in cylindrical and spherical systems. The same analogy is extended to the rate of entropy generation in the present study. The possible critical insulation thickness that yields a maximum rate of entropy generation is investigated. Entropy generation is related to heat transfer through and temperature distribution within the insulation material. It is found that there exists a critical insulation thickness for maximising the rate of entropy generation that is a function of the Bi number and the surface to ambient temperature ratio. The solution of such critical thickness is formulated analytically for both cylindrical and spherical geometries. It is also found that the critical insulation thickness for the rate of entropy generation does not coincide with that for the rate of heat transfer. Critical insulation thickness for maximum entropy generation
Ahmet Z. Sahin
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 34 - 43
Critical insulation thickness is known to refer to the insulation thickness that maximises the rate of heat transfer in cylindrical and spherical systems. The same analogy is extended to the rate of entropy generation in the present study. The possible critical insulation thickness that yields a maximum rate of entropy generation is investigated. Entropy generation is related to heat transfer through and temperature distribution within the insulation material. It is found that there exists a critical insulation thickness for maximising the rate of entropy generation that is a function of the Bi number and the surface to ambient temperature ratio. The solution of such critical thickness is formulated analytically for both cylindrical and spherical geometries. It is also found that the critical insulation thickness for the rate of entropy generation does not coincide with that for the rate of heat transfer.

]]> 10.1504/IJEX.2012.045059 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 34 - 43 Ahmet Z. Sahin Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia critical insulation thickness entropy generation maximisation heat transfer. 2012-01-24T23:20:50-05:00 10 1 34 43 2012-01-24T23:20:50-05:00 http://www.inderscience.com/link.php?id=45060 This paper studies heat transfer and entropy generation in a pin fin that is convectively heated at its base and losing heat through its tip in addition to the heat loss from its lateral surface. The analysis accounts for the skin friction drags at the base and the tip of the fin as well as the drag owing to forced convection over the lateral surface of the fin. The entropy generation rate is found to be a function of Reynolds and Prandtl numbers of hot and cold fluid flows, fluid friction to heat transfer irreversibility parameters based on hot and cold fluid properties, the ratios of hot fluid/fin and cold fluid/fin thermal conductivities, and the temperatures of the hot and cold fluids. Results illustrate the effects of various parameters on the entropy generation rate and the optimum fin length. Minimum entropy generation design of a convectively heated pin fin with tip heat loss
Abdul Aziz; Waqar Ahmed Khan
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 44 - 60
This paper studies heat transfer and entropy generation in a pin fin that is convectively heated at its base and losing heat through its tip in addition to the heat loss from its lateral surface. The analysis accounts for the skin friction drags at the base and the tip of the fin as well as the drag owing to forced convection over the lateral surface of the fin. The entropy generation rate is found to be a function of Reynolds and Prandtl numbers of hot and cold fluid flows, fluid friction to heat transfer irreversibility parameters based on hot and cold fluid properties, the ratios of hot fluid/fin and cold fluid/fin thermal conductivities, and the temperatures of the hot and cold fluids. Results illustrate the effects of various parameters on the entropy generation rate and the optimum fin length.

]]> 10.1504/IJEX.2012.045060 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 44 - 60 Abdul Aziz; Waqar Ahmed Khan Department of Mechanical Engineering, School of Engineering and Applied Science, Gonzaga University, Spokane, WA 99258, USA. ' Department of Engineering Sciences, PN Engineering College, National University of Sciences and Technology, Karachi 75350, Pakistan entropy generation pin fins skin friction drag Reynolds number heat transfer tip heat loss forced convection thermal conductivity optimum fin length. 2012-01-24T23:20:50-05:00 10 1 44 60 2012-01-24T23:20:50-05:00 http://www.inderscience.com/link.php?id=45061 In this study, an exergy analysis is applied to a conceptual integrated two-stage biomass gasifier and Solid Oxide Fuel Cell (SOFC) system. Several simulations are conducted to assess the effect of some key input parameters on the exergy ratios of the components and the exergy efficiency of the system. The results show that the exergy efficiency of the integrated system varies between 11.6% and 40.4%. The highest exergy destructions occur at the two-stage gasifier and the heat exchanger supplying heat to the air entering the SOFC; whereas the dryer, the blower, and the SOFC have the lowest exergy destructions. Exergy analysis of an integrated two-stage biomass gasifier and Solid Oxide Fuel Cell system
C. Ozgur Colpan
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 61 - 76
In this study, an exergy analysis is applied to a conceptual integrated two-stage biomass gasifier and Solid Oxide Fuel Cell (SOFC) system. Several simulations are conducted to assess the effect of some key input parameters on the exergy ratios of the components and the exergy efficiency of the system. The results show that the exergy efficiency of the integrated system varies between 11.6% and 40.4%. The highest exergy destructions occur at the two-stage gasifier and the heat exchanger supplying heat to the air entering the SOFC; whereas the dryer, the blower, and the SOFC have the lowest exergy destructions.

]]> 10.1504/IJEX.2012.045061 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 61 - 76 C. Ozgur Colpan Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street Toronto, Ontario M5B 2K3, Canada SOFC solid oxide fuel cells biomass gasifiers gasification pyrolysis exergy efficiency energy simulation heat exchangers. 2012-01-24T23:20:50-05:00 10 1 61 76 2012-01-24T23:20:50-05:00 http://www.inderscience.com/link.php?id=45062 This work presents the exergy balances of biogas dual fuel combustion modes using two different pilot fuels in a single-cylinder diesel engine. The main focus is on the use of biodiesel (BD) as a pilot in place of fossil diesel fuel. The results reveal that the important exergy loss recovery sources are the exhaust gas and cooling water exergy. By accessing these losses, there is an increase of 28–30% in work exergy for dual fuel modes as compared to diesel mode. Use of BD, in place of diesel as a pilot, reduces the maximum exergy efficiency roughly by 2%. Diagnosing the effects of pilot fuel quality on exergy terms in a biogas run dual fuel diesel engine
Bibhuti B. Sahoo; Ujjwal K. Saha; Niranjan Sahoo
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 77 - 93
This work presents the exergy balances of biogas dual fuel combustion modes using two different pilot fuels in a single-cylinder diesel engine. The main focus is on the use of biodiesel (BD) as a pilot in place of fossil diesel fuel. The results reveal that the important exergy loss recovery sources are the exhaust gas and cooling water exergy. By accessing these losses, there is an increase of 28–30% in work exergy for dual fuel modes as compared to diesel mode. Use of BD, in place of diesel as a pilot, reduces the maximum exergy efficiency roughly by 2%.

]]> 10.1504/IJEX.2012.045062 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 77 - 93 Bibhuti B. Sahoo; Ujjwal K. Saha; Niranjan Sahoo Department of Mechanical Engineering, Synergy Institute of Engineering and Technology, Dhenkanal 759001, Odisha, India. ' Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India. ' Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India biodiesel biogas dual fuel diesel engines exergy loss recovery fuel quality combustion modes biofuels exergy efficiency. 2012-01-24T23:20:50-05:00 10 1 77 93 2012-01-24T23:20:50-05:00 http://www.inderscience.com/link.php?id=45063 The present work reports the results of an entropy generation analysis on a symmetric flow distributor. The entropy generation minimisation method (EGM) was applied in order to lower the intrinsic irreversibilities associated to the geometric configuration of the flow pattern, aiming to improve the uniformity of flow distribution. 3D Computational Fluid Dynamics (CFD) methods were used to simulate the flow conditions, including a local entropy generation model. The implementation of the entropy generation minimisation method enabled to achieve a significant optimisation of the original design. Irreversibilities reduction of a flow distribution system by means of the EGM methodology
Bladimir Ramos-Alvarado; Abel Hernandez-Guerrero; V.H. Rangel-Hernandez
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 94 - 109
The present work reports the results of an entropy generation analysis on a symmetric flow distributor. The entropy generation minimisation method (EGM) was applied in order to lower the intrinsic irreversibilities associated to the geometric configuration of the flow pattern, aiming to improve the uniformity of flow distribution. 3D Computational Fluid Dynamics (CFD) methods were used to simulate the flow conditions, including a local entropy generation model. The implementation of the entropy generation minimisation method enabled to achieve a significant optimisation of the original design.

]]> 10.1504/IJEX.2012.045063 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 94 - 109 Bladimir Ramos-Alvarado; Abel Hernandez-Guerrero; V.H. Rangel-Hernandez Department of Mechanical Engineering, University of Guanajuato, Salamanca-Valle de Santiago Road, km. 3.8+1.5, Palo Blanco Community, Mexico. ' Department of Mechanical Engineering, University of Guanajuato, Salamanca-Valle de Santiago Road, km. 3.8++1.5, Palo Blanco Community, Mexico. ' Department of Mechanical Engineering, University of Guanajuato, Salamanca-Valle de Santiago Road, km. 3.8+1.5, Palo Blanco Community, Mexico flow distribution irreversibilities reduction EGM entropy generation minimisation computational fluid dynamics 3D CFD. 2012-01-24T23:20:50-05:00 10 1 94 109 2012-01-24T23:20:50-05:00 http://www.inderscience.com/link.php?id=45064 This paper presents an entropy generation analysis for steady conduction in a hollow sphere with temperature dependent internal heat generation and asymmetric convective cooling. An exact analytical solution for the temperature distribution is used to compute dimensionless local and total entropy generation rates in the hollow sphere. The total entropy generation rate depends on reference heat generation rate Q, the heat generation-temperature variation parameter a, the temperature asymmetry parameter λ and Biot numbers Bi1 and Bi2. Graphs illustrating the effect of these parameters on the local and total entropy generation rates are presented. Total entropy generation in the hollow sphere can be minimised with an appropriate choice of cooling parameters. Entropy generation in an asymmetrically cooled hollow sphere with temperature dependent internal heat generation
Abdul Aziz; Waqar Ahmed Khan
International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 110 - 123
This paper presents an entropy generation analysis for steady conduction in a hollow sphere with temperature dependent internal heat generation and asymmetric convective cooling. An exact analytical solution for the temperature distribution is used to compute dimensionless local and total entropy generation rates in the hollow sphere. The total entropy generation rate depends on reference heat generation rate Q, the heat generation-temperature variation parameter a, the temperature asymmetry parameter λ and Biot numbers Bi1 and Bi2. Graphs illustrating the effect of these parameters on the local and total entropy generation rates are presented. Total entropy generation in the hollow sphere can be minimised with an appropriate choice of cooling parameters.

]]> 10.1504/IJEX.2012.045064 International Journal of Exergy, Vol. 10, No. 1 (2012) pp. 110 - 123 Abdul Aziz; Waqar Ahmed Khan Department of Mechanical Engineering, Gonzaga University, Spokane, WA 99258, USA. ' Department of Engineering Sciences, PN Engineering College, National University of Sciences and Technology, Karachi 75350, Pakistan local entropy generation rates total entropy generation rates hollow spheres temperature dependent internal heat generation asymmetric cooling steady conduction. 2012-01-24T23:20:50-05:00 10 1 110 123 2012-01-24T23:20:50-05:00