Numerical Simulation Of Heat Transfer Enhancement By Vortex In Spiral Plate Heat Exchanger

Due to the compact structure and high heat exchange efficiency,spiral plate heat exchangers are widely used in various fields such as machinery manufacturing and chemical production.The pin-fin is the main technology for the heat transfer enhancement of the spiral plate exchangers.The geometry size and arrangement of the pin-fins in the heat exchange channel are important factors that affect the enhanced heat transfer.At present,the research on the heat transfer enhancement of spiral plate heat exchangers mainly focuses on the calculation of the overall heat transfer of the channel.In this paper,the influence of longitudinal vortex size,direction of longitudinal vortex rotation and interaction of longitudinal vortices on heat transfer enhancement in curved channel of spiral plate heat exchanger is analyzed.The numerical simulation method is used to study the flow field,temperature field,vorticity field,friction factor f,average Nu and the comprehensive performance evaluation factor JF of the circular pin-fins,elliptical pin-fins,diamond-shaped pin-fins and two semi-circular pin-fins in the spiral plate heat exchanger.In the curved channel installed with elliptical pin-fins,the fluid velocity on the same section gradually decreases with the increase of the length-to-minor axis ratio of the elliptical pin-fins,the longitudinal vorticity on the same cross section also decreases gradually.The average Nu of the channel decreases while the comprehensive performance evaluation factor JF increases gradually.The elliptical pin-fins has a very significant effect in reducing the friction factor.When a/b=4.0,the friction factor f is the smallest which is only about 41.6%of the cylindrical pin-fins.In the curved channel where the diamond-shaped pin-fins are installed,the diamond-shaped pin-fins with a smaller number of top angles have a prominent effect on reducing the resistance of the channel.The maximum comprehensive performance evaluation factor JF is 1.327.The friction factor increases with the increase of apex angle of the diamond-shaped pin-fins.The average Nu and friction factor f of the curved channel installed with two semicircular pin-fins are larger than that of the cylindrical pin fin.In the pin-fin distance d₁=4～15 mm,JF is greater than 1 and the maximum JF=1.081 is obtained at d₁=10mm,Re=23226.For the parallel semicircular pin-fins,JF is greater than 1 for only the distance with d₁=6～15 mm,and the maximum JF=1.075 is obtained at d₂=6 mm,Re=19355.The overall performance of the elliptical pin-fins channel is better than the other shapes of pin-fins.The diamond-shaped pin-fins with a smaller number of top angles has better comprehensive performance.JF of the channel with diamond-shaped column is greater than the elliptical pin-fin when Re=48387 andθ=15°.