Numerical Simulation Of Heat Transfer Enhanced Tube Inserted Delta-wing

Energy is important for human survival and development,which is the ensure for the sustained and rapid economic and social development.With the development of social production,energy problem has become the focus of global attention.how to save energy has become an imminent problem.While saving energy and reducing consumption is dependent on progress and application of the heat transfer technology.Therefore,development of new heat transfer technology,developing practical high-efficiency and low-resistance enhanced heat exchanger can bring huge economic and social benefits.In view of this,based on the design principle of heat transfer enhancement by longitudinal vortex generator,a new type of heat transfer tube inserted delta wing longitudinal vortex(Circular tube with a inserted delta wing,which constantly induced longitudinal vortex,secondary flow to enhance the heat transfer);the mathematical and physical model of the heat transfer tube with delta wing,which regarding the coupling of solid and fluid,were established;Through the three dimensional numerical simulation,to research and analysis the local temperature field and velocity field were studied and the mechanism of heat transfer enhancement was analyzed;the effect of the delta wing angle,wing height and the wing span of the heat transfer enhanced tube inserted delta wing were investigated..The major findings are as follows.(1)the inserted delta wing generate the longitudinal vortex,resulting in secondary flow.So that the fluid scouring the tube wall vertically thus thinning the boundary layer and enhancing the fluid mixing.Thereby significantly enhanced heat transfer,with the increase of the small pressure drop,which increase its PEC value.(2)When single-phase water as working medium,the Reynolds number is 20000?100000,the delta wing Angle is 10° to 30°,the study found that the drag coefficient increased with the angle increases,and the maximum value increased by 117.25%than the smooth tube;the Nu increase with the increase of angle,and the maximum increased by 49.94%than the smooth tube;the largest value of PEC is 1.22 when the wing angle is 10°.(3)when the height of the delta wing is 5 mm to 13 mm,calculation show that the drag coefficient is the largest when wing height is 13 mm,and the value increased by 82.2%than the smooth tube;Nu value is the largest when the wing hight is 7 mm,it increased by 45.39%than smooth tube;The largest PEC value is 1.22 when the wing height is 7 mm.(4)When the small wing span is 2.5 cm?12.5 cm,the calculation results show that the drag coefficient decreases with the increase of wing span,and the maximum value increased by 76.06%than the smooth tube;Nu number is the largest when the span is 5 cm,and its maximum 45.39%larger than the smooth tube;The largest PEC value is 1.22 when the wing span is 5 cm.(5)For the three working fluid(air,water,oil),the Nu increases with the increase of the Re number;For the working medium which have a larger Pr number(oil),the heat transfer performance is better at the small Re;for the working medium which have a less Pr number(air),the heat transfer performance is better at the large Re.(6)In the range of Re of 20000?100000,The PEC value of the enhanced heat transfer tube were greater than 1 for the water and air,but is less than 1 for the oil;In the range of Re of 2000?3 500,the PEC value of the enhanced heat transfer tube increased from less than 1 to 1.09 for the oil,and decreased from 1.15 to 0.85 for the air.