The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
S.k. Som - One of the best experts on this subject based on the ideXlab platform.
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Prediction of flame speed and exergy analysis of premixed flame in a heat recirculating cylindrical micro combustor
Energy, 2017Co-Authors: Uttam Rana, Suman Chakraborty, S.k. SomAbstract:Abstract An interaction between wall heat recirculation, flame speed and Thermodynamic Irreversibility has been established from an analytical model based on flame sheet assumption pertaining to a premixed flame in a cylindrical micro combustor. The total rate of heat recirculation through the combustor wall and the flame speed depict global maxima depending on the wall to gas thermal conductivity ratio. The optimum value of wall to gas thermal conductivity ratio for maximum flame speed bears an inverse relation with the ratio of wall thickness to combustor radius and the outer wall Nusselt number. The proportional change in heat recirculation is more than that in heat generation with wall to gas thermal conductivity ratio, wall thickness to combustor radius ratio and outer wall Nusselt number. The exergy loss at outer wall is around 5–7% of inflow exergy while the exergy destruction in the process of heat recirculation and combustion is around 40–45% of inflow exergy. The second law efficiency is found to be almost constant around a value of 58%.
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Thermodynamic irreversibilities and exergy balance in combustion processes
Progress in Energy and Combustion Science, 2008Co-Authors: S.k. Som, Amitava DattaAbstract:The growing concern for energy, economy and environment calls for an efficient utilization of natural energy resources in developing useful work. An important Thermodynamic aspect in gauging the overall energy economy of any physical process is the combined energy and exergy analysis from the identification of process irreversibilities. The present paper makes a comprehensive review pertaining to fundamental studies on Thermodynamic Irreversibility and exergy analysis in the processes of combustion of gaseous, liquid and solid fuels. The need for such investigations in the context of combustion processes in practice is first stressed upon and then the various approaches of exergy analysis and the results arrived at by different research workers in the field have been discussed. It has been recognized that, in almost all situations, the major source of irreversibilities is the internal thermal energy exchange associated with high-temperature gradients caused by heat release in combustion reactions. The primary way of keeping the exergy destruction in a combustion process within a reasonable limit is to reduce the Irreversibility in heat conduction through proper control of physical processes and chemical reactions resulting in a high value of flame temperature but lower values of temperature gradients within the system. The optimum operating condition in this context can be determined from the parametric studies on combustion irreversibilities with operating parameters in different types of flames.
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Energy and Exergy Balance in the Process of Pulverized Coal Combustion in a Tubular Combustor
Journal of Heat Transfer, 2005Co-Authors: S.k. Som, S. S. Mondal, Sukanta K. DashAbstract:A theoretical model of exergy balance, based on availability transfer and flow availability, in the process of pulverized coal combustion in a tubular air-coal combustor has been developed to evaluate the total Thermodynamic Irreversibility and second law efficiency of the process at various operating conditions. The velocity, temperature, and concentration fields required for the evaluation of flow availability have been computed numerically from a two-phase separated flow model on a Eulerian-Lagrangian frame in the process of combustion of pulverized coal particles in air. The total Thermodynamic Irreversibility in the process has been determined from the difference in the flow availability at the inlet and outlet of the combustor. A comparative picture of the variations of combustion efficiency and second law efficiency at different operating conditions, such as inlet pressure and temperature of air, total air flow rate and inlet air swirl, initial mean particle diameter, and length of the combustor, has been provided to shed light on the trade-off between the effectiveness of combustion and the lost work in the process of pulverized coal combustion in a tubular combustor.
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Energy and Exergy Balance in the Process of Spray Combustion in a Gas Turbine Combustor
Journal of Heat Transfer, 2002Co-Authors: S.k. Som, N. Y. SharmaAbstract:A theoretical model of exergy balance based on availability transfer and flow availability in the process of spray combustion in a gas turbine combustor has been developed to evaluate the total Thermodynamic Irreversibility and second law efficiency of the process at various operating conditions, for fuels with different volatilities. The velocity, temperature and concentration fields in the combustor, required for the evaluation of the flow availabilities and process irreversibilities, have been computed numerically from a two phase separated flow model of spray combustion. The total Thermodynamic Irreversibility in the process of spray combustion has been determined from the difference in the flow availability at inlet and outlet of the combustor. The Irreversibility caused by the gas phase processes in the combustor has been obtained from the entropy transport equation, while that due to the inter-phase transport processes has been obtained as a difference of gas phase irreversibilities from the total Irreversibility. A comparative picture of the variations of combustion efficiency and second law efficiency at different operating conditions for fuels with different volatilities has been made to throw light on the trade off between the effectiveness of combustion and the lost work in the process of spray combustion in a gas turbine combustor.
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Energy and exergy balance in a gas turbine combustor
Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 1999Co-Authors: Amitava Datta, S.k. SomAbstract:AbstractAn energy and exergy balance in the process of spray combustion in a model tubular gas turbine combustor has been made to determine the combustion efficiency and second law efficiency of the process at different operating conditions. The velocity, temperature and species concentration fields in the combustor have been evaluated numerically from a two-phase separated flow model of the spray along with suitable reaction kinetics for the gas phase reaction. A theoretical model of exergy analysis, based on availability transfer and flow availability, has been developed to predict the second law efficiency of the combustion process in the gas turbine combustor. A comparative picture of the functional relationships of combustion efficiency and second law efficiency of the process with the operating parameters of the combustor have been made to throw light on the trade-off between the effectiveness of combustion and the lost work due to Thermodynamic Irreversibility.
K J Chua - One of the best experts on this subject based on the ideXlab platform.
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energy exergy and economic analysis of a hybrid spray assisted low temperature desalination thermal vapor compression system
Energy, 2019Co-Authors: Q. Chen, Kum M Ja, Y Li, K J ChuaAbstract:Abstract Integrating thermal desalination systems with vapor compression is an effective way to improve the energy efficiency. This paper investigates a spray-assisted low-temperature desalination system that is integrated with a thermal vapor compression system (SLTD-TVC). A detailed Thermodynamic model is judiciously developed based on the principles of heat and mass transfer, heat balance, mass balance, and exergy balance. Applying the model, the energy efficiency of the combined SLTD-TVC process is first evaluated. The production ratio of the combined system is found to be 10–35% higher than that of the conventional SLTD process. Accordingly, an exergy analysis is conducted to quantify the sources of Irreversibility within the system. The steam jet ejector is found to be the major source of Thermodynamic Irreversibility, accounting for more than 40% of the exergy destruction. The overall system efficiency is improved at a lower motive steam pressure, a higher number of operating stages and a medium cooling water flowrate. Finally an economic analysis is carried out, which reveals that the changes of both initial plant cost and operation cost are marginal after the integration of the thermal vapor compression system.
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Energy, exergy and economic analysis of a hybrid spray-assisted low-temperature desalination/thermal vapor compression system
Energy, 2018Co-Authors: Q. Chen, M. Kum Ja, Y Li, K J ChuaAbstract:Abstract Integrating thermal desalination systems with vapor compression is an effective way to improve the energy efficiency. This paper investigates a spray-assisted low-temperature desalination system that is integrated with a thermal vapor compression system (SLTD-TVC). A detailed Thermodynamic model is judiciously developed based on the principles of heat and mass transfer, heat balance, mass balance, and exergy balance. Applying the model, the energy efficiency of the combined SLTD-TVC process is first evaluated. The production ratio of the combined system is found to be 10–35% higher than that of the conventional SLTD process. Accordingly, an exergy analysis is conducted to quantify the sources of Irreversibility within the system. The steam jet ejector is found to be the major source of Thermodynamic Irreversibility, accounting for more than 40% of the exergy destruction. The overall system efficiency is improved at a lower motive steam pressure, a higher number of operating stages and a medium cooling water flowrate. Finally an economic analysis is carried out, which reveals that the changes of both initial plant cost and operation cost are marginal after the integration of the thermal vapor compression system.
Amitava Datta - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic irreversibilities and exergy balance in combustion processes
Progress in Energy and Combustion Science, 2008Co-Authors: S.k. Som, Amitava DattaAbstract:The growing concern for energy, economy and environment calls for an efficient utilization of natural energy resources in developing useful work. An important Thermodynamic aspect in gauging the overall energy economy of any physical process is the combined energy and exergy analysis from the identification of process irreversibilities. The present paper makes a comprehensive review pertaining to fundamental studies on Thermodynamic Irreversibility and exergy analysis in the processes of combustion of gaseous, liquid and solid fuels. The need for such investigations in the context of combustion processes in practice is first stressed upon and then the various approaches of exergy analysis and the results arrived at by different research workers in the field have been discussed. It has been recognized that, in almost all situations, the major source of irreversibilities is the internal thermal energy exchange associated with high-temperature gradients caused by heat release in combustion reactions. The primary way of keeping the exergy destruction in a combustion process within a reasonable limit is to reduce the Irreversibility in heat conduction through proper control of physical processes and chemical reactions resulting in a high value of flame temperature but lower values of temperature gradients within the system. The optimum operating condition in this context can be determined from the parametric studies on combustion irreversibilities with operating parameters in different types of flames.
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Energy and exergy balance in a gas turbine combustor
Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 1999Co-Authors: Amitava Datta, S.k. SomAbstract:AbstractAn energy and exergy balance in the process of spray combustion in a model tubular gas turbine combustor has been made to determine the combustion efficiency and second law efficiency of the process at different operating conditions. The velocity, temperature and species concentration fields in the combustor have been evaluated numerically from a two-phase separated flow model of the spray along with suitable reaction kinetics for the gas phase reaction. A theoretical model of exergy analysis, based on availability transfer and flow availability, has been developed to predict the second law efficiency of the combustion process in the gas turbine combustor. A comparative picture of the functional relationships of combustion efficiency and second law efficiency of the process with the operating parameters of the combustor have been made to throw light on the trade-off between the effectiveness of combustion and the lost work due to Thermodynamic Irreversibility.
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Thermodynamic Irreversibilities and Second Law Analysis in a Spray Combustion Process
Combustion Science and Technology, 1999Co-Authors: Amitava Datta, S.k. SomAbstract:A theoretical model of exergy analysis, based on availability transfer and flow availability, in the process of spray combustion has been developed to evaluate the total Thermodynamic Irreversibility and second law efficiency of the process at various operating conditions. The velocity, temperature and concentration fields in the combustor, required for the evaluation of the availabilities and irreversibilities, have been computed numerically from a two phase separated flow model of the spray along with a suitable reaction kinetics for the gas phase reaction. The Thermodynamic irreversibilities associated with the gas phase processes in the combustor have been obtained from the entropy transport equation, while that due to the interphase transport processes have been obtained as a difference of gas phase irreversibilities from the total Irreversibility. The Thermodynamic irreversibilities associated with different processes and a comparative picture of the variation of second law efficiency at various ope...
Hongfei Zheng - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic analysis of an idealised solar tower thermal power plant
Applied Thermal Engineering, 2015Co-Authors: Hongfei Zheng, Xu Yu, Yuehong Su, S B Riffat, Jianyin XiongAbstract:Abstract In the real solar tower thermal power system, it is widely acknowledged that the Thermodynamic Irreversibility, such as convective and radiative loss on tower receiver, and thermal resistance in heat exchangers, is unavoidable. With above factors in mind, this paper presents an ideal model of the solar tower thermal power system to analyze the influence of various parameters on thermal and exergy conversion efficiencies, including receiver working temperature, concentration ratio, endoreversible heat engine efficiency and so forth. And therefore the variation of maximum thermal conversion efficiency in terms of concentration ratio and endoreversible heat engine efficiency could be theoretically obtained. The results indicate that raising the receiver working temperature could initially increase both thermal and exergy conversion efficiencies until an optimum temperature is reached. The optimum temperature would also increase with the concentration ratio. Additionally, the concentration ratio has a positive effect on the thermal conversion efficiency: increasing the concentration ratio could raise the conversion efficiency until the concentration ratio is extremely high, after which there will be a slow drop. Lastly, the endoreversible engine efficiency also has significant influence on the thermal conversion efficiency, it will increase the thermal conversion efficiency until it reaches the maximum and optimum value, and then the conversion efficiency will drop dramatically.
Adrian Bejan - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic optimization of heat transfer equipment configuration in an environmental control system
International Journal of Energy Research, 2001Co-Authors: Amin Alebrahim, Adrian BejanAbstract:In this paper, we show that many features of a heat transfer installation can be deduced from the maximization of the global performance of the greater system that employs the installation. The heat transfer installation is a series of two cross-flow heat exchangers. The greater system is the environmental control system (ECS) of an aircraft. The global performance objective is the minimization of the total Thermodynamic Irreversibility of the ECS. Several architectural features are deduced from principle: the relative position of the two heat exchangers, their relative sizes, and all the geometric aspect ratios of the two heat exchanger cores. We find that the optimized architecture is insensitive (robust) to changes in some of the external parameters. Robustness is a useful feature because it simplifies the design work. Furthermore, one design that is built can be expected to function at near-optimal levels when the external parameters change. The application of this method of topology optimization to more complex systems is discussed. Copyright © 2001 John Wiley & Sons, Ltd.
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Thermodynamic optimization of heat‐transfer equipment configuration in an environmental control system
International Journal of Energy Research, 2001Co-Authors: Amin Alebrahim, Adrian BejanAbstract:In this paper, we show that many features of a heat transfer installation can be deduced from the maximization of the global performance of the greater system that employs the installation. The heat transfer installation is a series of two cross-flow heat exchangers. The greater system is the environmental control system (ECS) of an aircraft. The global performance objective is the minimization of the total Thermodynamic Irreversibility of the ECS. Several architectural features are deduced from principle: the relative position of the two heat exchangers, their relative sizes, and all the geometric aspect ratios of the two heat exchanger cores. We find that the optimized architecture is insensitive (robust) to changes in some of the external parameters. Robustness is a useful feature because it simplifies the design work. Furthermore, one design that is built can be expected to function at near-optimal levels when the external parameters change. The application of this method of topology optimization to more complex systems is discussed. Copyright © 2001 John Wiley & Sons, Ltd.
