| With the rapid development of human society,the problem of energy shortage has become increasingly prominent,and it is urgent to increase the utilization of energy.Enhanced heat transfer technology has received extensive attention from scholars because of its remarkable effect of enhancing heat transfer.It is a very effective technology for energy conservation and emission reduction,and improving energy efficiency.Among them,the longitudinal vortex generator is an effective method of enhanced heat transfer,which generates a spiral vortex in the channel,destroys the development of the boundary layer,and achieves the purpose of enhancing heat exchange.At the same time,because pulsating flow can cause periodic disturbance to the fluid in the pipeline,the wall boundary layer is continuously destroyed,and the heat transfer between the fluid and the wall surface is enhanced.In this paper,the experimental method and numerical simulation software ANSYS 15.0 are used to study the steady-state enhanced heat transfer characteristics of a longitudinal vortex generator in a rectangular channel.First,an experimental platform was set up to study the heat transfer and flow characteristics of the vortex generator during turbulent flow,and compared with the simulation results to verify the accuracy of the numerical simulation.Secondly,the effects of the structure parameters and arrangement of the longitudinal vortex generator on the heat transfer and flow of the rectangular channel are studied during turbulence.Finally,the optimal vortex generator is selected to study the effect of frequency,amplitude and Reynolds number on the pulsating flow and field coordination angle under pulsating flow conditions.Under turbulent conditions,the following conclusions are obtained by comparing the experimental data of the rectangular channel of the vortex generator with the simulation data:1.An uncertainty analysis was performed.The relative uncertainty of Nu was 9.23%,and the relative error of friction factor f was 4.96%.2.Comparing the experimental results with the simulation results,the maximum error of Nu is 6.81%,and the maximum error of f is 7.7%.The experimental results are in good agreement with the simulation results,which shows the correctness of the numerical methods and results in this paper.3,In the three relative positions of the short and long wings of the longitudinal vortex generator,the short wing is located at the upper end of the long wing(close to the entrance side),Nu number is higher than the other two,and the heat transfer performance is good;The upper friction factor f is higher than the other two,and the fluidity is poor,but at the upper end,the overall heat exchange effect is the best.4.In the three kinds of angles between the short and long wings of the vertical vortex generator,the fluidity is improved as the included angle becomes smaller,but the heat transfer effect becomes worse,and the integrated heat transfer effect also deteriorates.Therefore,in terms of comprehensive heat transfer performance,the geometry of the shortwing and long-wing angles of the longitudinal vortex generator is 90° relative to the best.Maintaining the integrity of the longitudinal vortex generator structure is necessary to improve the overall heat transfer effect.5.For array spacing of different vertical vortex generators,the equidistant array spacing is the best among the three array spacings in terms of heat transfer performance,fluidity,and overall heat transfer effect.In pulsating flow,when the Reynolds number Re and the amplitude Au are constant,the frequency is proportional to Nu and Nu increases with increasing frequency,and the effect on the fluid flow resistance varies with the frequency range;when the Reynolds number Re and the frequency are constant Increasing the amplitude helps to enhance the heat transfer effect.When the frequency and amplitude of Au are constant,the increase of Reynolds number has a significant effect on the improvement of pulsating flow heat transfer performance.In the study of the impact of pulsating flow on field coordination,it can be seen that when the frequency is greater than 1,the amplitude and Reynolds number are increased,which helps to improve the synergy of the velocity field and the temperature field and reduce the field coordination angle.It can be summarized as follows: When the frequency is greater than 1,increasing the amplitude and Reynolds number will help to improve the comprehensive heat transfer performance of the pulsating flow. |
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