Nanotechnology is widely used in heat transfer devices to improve thermal performance.Nanofluids can be applied in heat pipes to decrease thermal resistance and achieve a higher heat transfer capability.In the present...Nanotechnology is widely used in heat transfer devices to improve thermal performance.Nanofluids can be applied in heat pipes to decrease thermal resistance and achieve a higher heat transfer capability.In the present article,a comprehensive literature review is performed on the nanofluids’ applications in heat pipes.Based on reviewed studies,nanofluids have a high capacity to boost the thermal behavior of various types of heat pipes such as conventional heat pipes,pulsating heat pipes,and thermosyphons.Besides,it is observed that there must be a selected amount of concentration for the high-performance utilization of nanoparticles;high concentration of nanoparticles causes a higher thermal resistance which is mainly attributed to increment in the dynamic viscosity and the higher possibility of particles’ agglomeration.Enhancement in heat transfer performance is the result of increasing in nucleation sites and the intrinsically greater nanofluids’ thermal conductivity.展开更多
Owing to the energy demands and global warming issue, employing more effective power cycles has become a responsibility. This paper presents a thermo-dynamical study of an irreversible Brayton cycle with the aim of op...Owing to the energy demands and global warming issue, employing more effective power cycles has become a responsibility. This paper presents a thermo-dynamical study of an irreversible Brayton cycle with the aim of optimizing the performance of the Brayton cycle. Moreover, four different schemes in the process of multi-objective optimization were suggested, and the outcomes of each scheme are assessed separately. The power output, the concepts of entropy generation, the energy, the exergy output, and the exergy efficiencies for the irreversible Brayton cycle are considered in the analysis. In the first scheme, in order to maximize the exergy output, the ecological function and the ecological coefficient of performance, a multi-objective optimization algorithm (MOEA) is used. In the second scheme, three objective functions including the exergetic performance criteria, the ecological coefficient of performance, and the ecological function are maximized at the same time by employing MOEA. In the third scenario, in order to maximize the exergy output, the exergetic performance criteria and the ecological coefficient of performance, a MOEA is performed. In the last scheme, three objective functions containing the exergetic performance criteria, the ecologi-cal coefficient of performance, and the exergy-based ecological function are maximized at the same time by employing multi-objective optimization algorithms. All the strategies are implemented via multi-objective evolu-tionary algorithms based on the NSGAII method. Finally, to govern the final outcome in each scheme, three well- known decision makers were employed.展开更多
文摘Nanotechnology is widely used in heat transfer devices to improve thermal performance.Nanofluids can be applied in heat pipes to decrease thermal resistance and achieve a higher heat transfer capability.In the present article,a comprehensive literature review is performed on the nanofluids’ applications in heat pipes.Based on reviewed studies,nanofluids have a high capacity to boost the thermal behavior of various types of heat pipes such as conventional heat pipes,pulsating heat pipes,and thermosyphons.Besides,it is observed that there must be a selected amount of concentration for the high-performance utilization of nanoparticles;high concentration of nanoparticles causes a higher thermal resistance which is mainly attributed to increment in the dynamic viscosity and the higher possibility of particles’ agglomeration.Enhancement in heat transfer performance is the result of increasing in nucleation sites and the intrinsically greater nanofluids’ thermal conductivity.
文摘Owing to the energy demands and global warming issue, employing more effective power cycles has become a responsibility. This paper presents a thermo-dynamical study of an irreversible Brayton cycle with the aim of optimizing the performance of the Brayton cycle. Moreover, four different schemes in the process of multi-objective optimization were suggested, and the outcomes of each scheme are assessed separately. The power output, the concepts of entropy generation, the energy, the exergy output, and the exergy efficiencies for the irreversible Brayton cycle are considered in the analysis. In the first scheme, in order to maximize the exergy output, the ecological function and the ecological coefficient of performance, a multi-objective optimization algorithm (MOEA) is used. In the second scheme, three objective functions including the exergetic performance criteria, the ecological coefficient of performance, and the ecological function are maximized at the same time by employing MOEA. In the third scenario, in order to maximize the exergy output, the exergetic performance criteria and the ecological coefficient of performance, a MOEA is performed. In the last scheme, three objective functions containing the exergetic performance criteria, the ecologi-cal coefficient of performance, and the exergy-based ecological function are maximized at the same time by employing multi-objective optimization algorithms. All the strategies are implemented via multi-objective evolu-tionary algorithms based on the NSGAII method. Finally, to govern the final outcome in each scheme, three well- known decision makers were employed.
