The Numerical Study Of Heat Transfer Of Staggered Circular Tube Bank Fin Heat Exchanger With Curve Trapezoidal Vortex Generators

Tube bank fin heat exchanger is the core emblem to realize the heat exchange, betweenworking mediums, and is a energy consuming device in the may processes such as energypower, metallurgy, petrochemical engineering, transportation and construction. Heat transferenhancement is the most important way of improving the heat exchanger performance,reducing manufacturing and cost saving energy. Considering the limitations of size and cost,the area of the fin can’t unlimited increase. In order to further improve the performance ofcircular tube bank fin heat exchanger, setting of vortex generator in the fin surface is a kind ofeffective measures. Meanwhile, many reported results show that: on the fin regions contactingwith the wake regions of the tubes the heat transfer coefficient is very low; in the wakeregions much more mechanical energy is dissipated into heat, hence, pressure drop of fluidflow is large. Therefore, reducing the size of the wake regions is key measure to enhance heattransfer performance for the fin side of circular tube fin heat exchanger. Motivated by these,this paper numerically studies the heat transfer and fluid flow performances of the fin withpunched curve trapezoidal vortex generators (CTVGs) in the wake regions of the tubes.The main works are: establishing physical model and mathematical formulation;programming the code; and analyzing the mechanism heat transfer enhancement of CTVGs.The investigations of the effect of the geometrical parameters of CTVGs, such as thecircumferential position, the radial position, the base length, the edge heights and the fin spacing, onthe heat transfer and fluid flow characteristics of the fin side in a tube bank fin heat exchangerare performed.The numerical results can be drawn as follows:(1) when fluid flows across the tube withvortex generators, a fluid flow is guided into the wake zone, and the side of the wake regiondecreases, thus, heat transfer on the fin surface behind the tube increases;(2) CTVGs canefficiently generate the longitudinal vortices and increase the intensity of secondary flow. This willefficiently enhance the heat transfer on the fin surface downstream CTVGs. Meanwhile, closerelationships exist between the average dimensionless intensity of secondary flow and theaverage Nusselt number;(3) when the start points of CTVGs are positioned more upstreamrespecting to the tube longitude axis, under the same other conditions, CTVGs couldefficiently enhance heat transfer;(4) when the diameter of the base edge of CTVGs is about1.8times of the tube diameter, good the heat transfer performance can be obtained;(5) Smallbase length of CTVGs has better heat transfer performance;(6) due to the lower flowresistance, small height of CTVGs can enforce better heat transfer performance;(7)depending on different Re, there is a optimal fin spacing.