Analysis Of Performance And Optimization Of Heat Transfer Enhanced Circular Tube With Rectangular Wings Longitudinal Vortex Generator

Energy is the lifeblood for the development of human economy and society which is the material bases for mankind living.It is also the forceful for the progress of mankind.With the development of the social economy,the world's energy consumption is rocketing,the energy crisis is increasing and the environment is continuous worsening.The heat exchange equipments and components are widely used in the high-energy industries such as HVAC,chemical and petroleum.The development of the effective heat transfer enhancement technologies and the efficient heat transfer components have very important significance for energy conservation and environmental protection.The investigations of heat transfer enhanced mechanism have very important academic value.A new heat transfer enhanced circular tube with rectangle wings longitudinal vortex generator was put forwarded based on the theory of heat transfer enhancement.The performance of the new heat transfer enhanced tube with different structure forms was studied in detail through 3D numerical simulation and the heat transfer mechanism was revealed.First,the three-dimensional mathematical and physical model of the heat transfer enhanced circular tube with rectangle wings longitudinal vortex generator was established,the complex computing grid was generated,the grid independence assessment was processed and the reliability validation of the numerical calculation was carried out.By the numerical simulation,the local flow field and temperature distribution was obtained.The results showed that when the rectangle wings were inserted in the heat transfer circular tube,the longitudinal vortex was produced,the secondary flow was formed and the disturbance was enhanced,which makes the temperature gradient and the velocity field have a better synergy and thus the heat transfer was enhanced greatly.Second,the influence of different structural parameters(angle,width and height)of the rectangular wing longitudinal vortex generator on the heat transfer,the resistance and the comprehensive performance of the new type heat transfer circular tube was studied.The results showed that the Nusselt numbers Nu of the enhanced circular tube was higher than the plain tube at the studied range.As compared to the plain tube,the Nusselt numbers Nu of the enhanced circular tube increased by 68%?147.8%,and the friction factors f of the enhanced circular tube increased by 159.7%?1437.9%.The Nusselt numbers Nu and the friction factors f were consistently increased while the value of performance evaluation criterion PEC was consistently decreased with the increase of wings angles;The Nusselt numbers Nu and the friction factors f were consistently increased while the value of performance evaluation criterion PEC was consistently decreased with the increase of the wings widths;The Nusselt numbers firstly increased and then flatten out,the friction factors f was consistently increased and the value of performance evaluation criterion PEC firstly increased and then maintain unchanged with the increase of the wings heights.Finally,the rectangular wing was optimized and three kinds of optimized structures were put forwarded(structure ?,structure ? and structure ?).Taking the rectangular wing with the angle 3 5 deg as an example,the flow and heat transfer characteristics of the optimized structures were studied,and the result was compared with the traditional structure.The results showed that for the optimized structure ?,the optimized structure ? and the optimized structure ?,the Nusselt numbers Nu were not changed distinctly;The friction factors f of the heat transfer enhanced tube with optimized structures were all much less than that of the heat transfer enhanced tube with traditional rectangle wings.Compared with the heat transfer enhanced tube with traditional rectangle wings,the comprehensive performance of the heat transfer enhanced tube with optimized structures was effectively improved.The PEC values of the heat transfer enhanced tube with the optimized structure ? is 1.13?1.17 which is the best.