Study Of Heat Transfer Enhancement On Twisted Flat Tube

As a carrier of energy transfer,heat exchanger is widely used in various industrial fields.Shell and tube heat exchanger is one of the most widely used heat exchangers because of its simple and reliable structure and low price.The energy crisis of the 1970 s led to extensive research and development of enhanced heat transfer technologies around the world.As a new type of passive heat transfer heat exchanger,spiral flat tube heat exchanger can improve the comprehensive heat transfer capacity of shell and tube heat exchanger.In this paper,by means of numerical simulation,fluent software was used to systematically explore the spiral flat pipe.The main contents of numerical simulation are as follows:(1)firstly,the heat transfer and flow resistance characteristics of smooth straight flat tubes and straight elliptical tubes with different structural parameters,namely different axial ratios,are simulated.Under the condition of laminar uniform heat flow and with the same Reynolds number,the difference between the heat transfer coefficient of the flat tube and the ellipse tube and that of the smooth straight circular tube with the same circumference is compared and analyzed,and the change rule of the heat transfer coefficient,nusserl number and the comprehensive heat transfer performance with the axial ratio b/a is studied and analyzed.(2)the similarities and differences of the streamline shapes of twisted flat tube,twisted ellipse tube and straight flat tube,straight ellipse tube and smooth circular tube are compared and studied,and the fundamental mechanism of helical structure improving heat transfer performance of heat exchange tube is analyzed.Then the influence of Reynolds number on the heat transfer and flow resistance characteristics of helical flat tube and helical oval tube is analyzed from the secondary flow distribution cloud diagram,temperature and velocity field,etc.Then the influence of the axial ratio on the heat transfer and flow resistance characteristics of helical flat tube and helical oval tube was compared and analyzed from the aspects of secondary flow distribution cloud diagram,temperature and velocity field and field synergy Angle,and the heat transfer performance of the two tubes with the same axial ratio was compared.The influence of helical torque S and the axial ratio b/a on the heat transfer performance of helical flat pipe is analyzed.(3)a kind of eccentric helical flat pipe is proposed,and the similarities and differences of the fluid flow trajectories between the eccentric helical pipe and the eccentric helical pipe are analyzed.Combined with the comprehensive heat transfer factors,the influence of the two on the heat transfer performance is pointed out.A kind of three-axis spiral flat pipe is also proposed.The section of the shape flat pipe is composed of three half flat pipes at an Angle of 120 degrees.Under the same axial ratio,the heat transfer performance of the helical tube is compared with that of the ordinary helical tube.