Interaction of counter rotating longitudinal vortices and the effect on fluid flow and heat transfer

Abstract The flow with longitudinal vortices is an important phenomenon in fluid dynamics and heat transfer. As the longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty, vortex generators (VGs) which can generate longitudinal vortices are widely used to enhance the heat transfer of compact heat exchanger. In order to obtain a better heat transfer performance, researchers always try to punch lots of VGs out of the fin surface. But the increasing number of VGs is not necessarily linked with the rise in heat transfer performance augmentation. This is because the longitudinal vortices will interact with each other when they meet in the flow channel and the interaction between the longitudinal vortices is always disadvantage for the heat transfer enhancement. In this paper, numerical simulation of the interaction between two counter-rotating longitudinal vortices was carried out for the plate–fin heat exchanger using two rows of delta winglet type vortex generators. The effect of the transversal distance between the two VGs on the interaction of vortices and the effect of such interaction on heat transfer enhancement are studied in detail. New and important understandings about the interaction of counterrotating longitudinal vortices are obtained. The intensity of the longitudinal vortices and the heat transfer performance are sensitive to the interaction between longitudinal vortices. The interaction between counterrotating vortices decreases the average intensity of vortices, but does not necessarily decrease the heat transfer performance of longitudinal vortices. The common flow region formed between the counterrotating longitudinal vortices is beneficial to the heat transfer enhancement though interaction takes place in the common flow region between longitudinal vortices. An optimum arrangement of VGs exists for obtaining the best heat transfer performance. The arrangement of VGs with the transversal distance is zero must be avoided due to the serious interaction between longitudinal vortices.

[1]  John K. Eaton,et al.  The Effect of Embedded Longitudinal Vortex Arrays on Turbulent Boundary Layer Heat Transfer , 1994 .

[2]  P.M.V. Subbarao,et al.  Experimental study of the effect of winglet location on heat transfer enhancement and pressure drop in fin-tube heat exchangers , 2005 .

[3]  Liang-Bi Wang,et al.  The Effectiveness of Secondary Flow Produced by Vortex Generators Mounted on Both Surfaces of the Fin to Enhance Heat Transfer in a Flat Tube Bank Fin Heat Exchanger , 2013 .

[4]  R. W. Mayne,et al.  Heat exchanger optimization , 1978 .

[5]  Liangbi Wang,et al.  Relationship between heat transfer intensity and absolute vorticity flux intensity in flat tube bank fin channels with Vortex Generators , 2008 .

[6]  L. B. Wang,et al.  The effects of span position of winglet vortex generator on local heat/mass transfer over a three-row flat tube bank fin , 2004 .

[7]  Wen-Quan Tao,et al.  Three-Dimensional Numerical Simulation on Laminar Heat Transfer and Fluid Flow Characteristics of Strip Fin Surface With X-Arrangement of Strips , 2004 .

[8]  K. Kataoka,et al.  Heat/mass transfer in taylor vortex flow with constant axial flow rates , 1977 .

[9]  Liang-Bi Wang,et al.  Numerical study of the relationship between heat transfer enhancement and absolute vorticity flux along main flow direction in a channel formed by a flat tube bank fin with vortex generators , 2009 .

[10]  Mohd Zamri Yusoff,et al.  An overview on heat transfer augmentation using vortex generators and nanofluids: Approaches and applications , 2012 .

[11]  Koichi Nishino,et al.  Heat transfer and pressure loss penalty for the number of tube rows of staggered finned-tube bundles with a single transverse row of winglets , 2003 .

[12]  V. C. Patel,et al.  Influence of streamwise curvature on longitudinal vortices imbedded in turbulent boundary layers , 1994 .

[13]  L. B. Wang,et al.  The Optimum Height of Winglet Vortex Generators Mounted on Three-Row Flat Tube Bank Fin , 2003 .

[14]  W. Hingst,et al.  Structure and development of streamwise vortex arrays embedded in a turbulent boundary layer , 1993 .

[15]  M. Fiebig,et al.  Vortices and Heat Transfer , 1997 .

[16]  J. Yanagihara,et al.  Optimization of winglet-type vortex generator positions and angles in plate-fin compact heat exchanger: Response Surface Methodology and Direct Optimization , 2015 .

[17]  Liangbi Wang,et al.  NUMERICAL STUDY OF INTERACTIONS OF VORTICES GENERATED BY VORTEX GENERATORS AND THEIR EFFECTS ON HEAT TRANSFER ENHANCEMENT , 2006 .

[18]  Gautam Biswas,et al.  Heat transfer in a channel with built-in wing-type vortex generators , 1992 .

[19]  Koichi Nishino,et al.  Numerical and experimental determination of flow structure and heat transfer effects of longitudinal vortices in a channel flow , 1996 .

[20]  Martin Fiebig,et al.  Flow structure and heat transfer in a channel with multiple longitudinal vortex generators , 1992 .

[21]  Anica Trp,et al.  Numerical investigation of heat transfer enhancement in a fin and tube heat exchanger using vortex generators , 2014 .

[22]  John K. Eaton,et al.  Heat Transfer Effects of a Longitudinal Vortex Embedded in a Turbulent Boundary Layer , 1984 .

[23]  Gautam Biswas,et al.  Heat transfer enhancement in fin-tube heat exchangers by winglet type vortex generators , 1994 .

[24]  Gautam Biswas,et al.  A note on the flow and heat transfer enhancement in a channel with built-in winglet pair , 2007 .

[25]  Kwangho Lee,et al.  A numerical analysis on flow field and heat transfer by interaction between a pair of vortices in rectangular channel flow , 2001 .

[26]  Martin Fiebig,et al.  Wing-type vortex generators for fin-and-tube heat exchangers , 1993 .