To examine and investigate the impact of nanofluid on heat exchanger performance,including the total heat transfer,the effect of friction factor,the average Nusselt number,and the thermal efficiency,the output heat tr...To examine and investigate the impact of nanofluid on heat exchanger performance,including the total heat transfer,the effect of friction factor,the average Nusselt number,and the thermal efficiency,the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically.The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021.The nanoparticles volume fractions adopted are 0.2%and 0.35%that used in numerical computations under 200 to 1400 Reynolds numbers range.The increasing of temperature is approximately 13%from the bottom to the top of heat exchanger,while the maximum enhancement of Nusselt number is about 10%,19%for volume fractions 0.2%and 0.35%respectively.The elevated values of the friction factor at the volumetric ratios of 0.2%and 0.35%are 0.25%and 0.47%respectively.The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.展开更多
The main problem of wind turbines is associated with induction generators in their power supply during short circuits in the grid.In this research,a new method is presented for the uninterrupted operation of a wind tu...The main problem of wind turbines is associated with induction generators in their power supply during short circuits in the grid.In this research,a new method is presented for the uninterrupted operation of a wind turbine equipped with an induction generator fed on both sides of feeding during network errors.Wind farms equipped with a doubly-fed induction generator(DFIG)require two abilities to allow system operators to increase proficiency.These capabilities include fault ride-through and synchronization of output force fluctuations,especially when these generators generate significant electrical power.A MATLAB®software environment has been used to evaluate and improve the performance of these turbines.A fuzzy complement(FC)controller is used to improve the performance of the DFIG.The results demonstrate that this controller limits the operation of the turbine current and voltage in the short-circuit mode well.Regarding results obtained from comparing two different modes,it can be said that ripple is 4%in the FC mode,while this parameter is equal to 10%for the proportional-integral controller.展开更多
文摘To examine and investigate the impact of nanofluid on heat exchanger performance,including the total heat transfer,the effect of friction factor,the average Nusselt number,and the thermal efficiency,the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically.The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021.The nanoparticles volume fractions adopted are 0.2%and 0.35%that used in numerical computations under 200 to 1400 Reynolds numbers range.The increasing of temperature is approximately 13%from the bottom to the top of heat exchanger,while the maximum enhancement of Nusselt number is about 10%,19%for volume fractions 0.2%and 0.35%respectively.The elevated values of the friction factor at the volumetric ratios of 0.2%and 0.35%are 0.25%and 0.47%respectively.The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.
文摘The main problem of wind turbines is associated with induction generators in their power supply during short circuits in the grid.In this research,a new method is presented for the uninterrupted operation of a wind turbine equipped with an induction generator fed on both sides of feeding during network errors.Wind farms equipped with a doubly-fed induction generator(DFIG)require two abilities to allow system operators to increase proficiency.These capabilities include fault ride-through and synchronization of output force fluctuations,especially when these generators generate significant electrical power.A MATLAB®software environment has been used to evaluate and improve the performance of these turbines.A fuzzy complement(FC)controller is used to improve the performance of the DFIG.The results demonstrate that this controller limits the operation of the turbine current and voltage in the short-circuit mode well.Regarding results obtained from comparing two different modes,it can be said that ripple is 4%in the FC mode,while this parameter is equal to 10%for the proportional-integral controller.
