Comparison of winglet-type vortex generators periodically deployed in a plate-fin heat exchanger – A synergy based analysis

The objective of the present investigation is to assess the performance of a plate-fin heat exchanger with an emphasis on acquiring fundamental understanding of the relation between local flow behavior and heat transfer augmentation mechanism. Numerical simulations are performed in a rectangular channel containing built-in longitudinal vortex generators on the bottom wall arranged periodically both in the streamwise and spanwise directions. Two types of vortex generators, namely, rectangular winglet pair (RWP) and delta-winglet pair (DWP) with two different flow arrangements, common-flow-up (CFU) and common-flow-down (CFD) have been explored to assess the influence of shape and flow arrangements on heat transfer enhancement. The basic mechanisms of flow structure and heat transfer characteristics have been examined with the help of secondary velocity vectors, streamlines, and temperature contours. Additionally, the mechanism of the local heat transfer augmentation has been explained using a novel concept called the field synergy principle. The performance of the vortex generators has been compared based on integral quantities such as Nusselt number, pressure loss, performance evaluation factor and domain averaged synergy angle. The computations reveal enhanced mixing of fluid between the wall layer and the core due to strong secondary flows produced by vortex generators. The performance analysis indicates that the RWP is more effective in terms of heat transfer enhancement as compared to DWP. The field synergy analysis has shown that the sites with higher Nusselt number are associated with smaller synergy angle or better coordination between the velocity vector and the temperature gradient.

[1]  Shantanu Biswas,et al.  Generation of Longitudinal Streamwise Vortices—A Device for Improving Heat Exchanger Design , 1994 .

[2]  Anthony M. Jacobi,et al.  Heat Transfer Enhancement by Delta-Wing-Generated Tip Vortices in Flat-Plate and Developing Channel Flows , 2002 .

[3]  Gautam Biswas,et al.  Augmentation of Heat Transfer by Creation of Streamwise Longitudinal Vortices Using Vortex Generators , 2012 .

[4]  M. Fiebig,et al.  Numerical analysis of heat transfer and flow loss in a parallel plate heat exchanger element with longitudinal vortex generators as fins , 1995 .

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

[6]  Suhas V. Patankar,et al.  An analysis of the effect of plate thickness on laminar flow and heat transfer in interrupted-plate passages , 1981 .

[7]  M. Fiebig,et al.  Comparison of Wing-Type Vortex Generators for Heat Transfer Enhancement in Channel Flows , 1994 .

[8]  M. Fiebig,et al.  Experimental investigations of heat transfer enhancement and flow losses in a channel with double rows of longitudinal vortex generators , 1993 .

[9]  S. Lau,et al.  Measurement of momentum and heat transport in the turbulent channel flow with embedded longitudinal vortices , 1999 .

[10]  F. Harlow,et al.  Numerical Calculation of Time‐Dependent Viscous Incompressible Flow of Fluid with Free Surface , 1965 .

[11]  Bu-Xuan Wang,et al.  A novel concept for convective heat transfer enhancement , 1998 .

[12]  Gautam Biswas,et al.  Numerical Investigations on Enhancement of Heat Transfer in a Compact Fin-and-Tube Heat Exchanger Using Delta Winglet Type Vortex Generators , 1999 .

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

[14]  C. W. Hirt,et al.  Calculating three-dimensional flows around structures and over rough terrain☆ , 1972 .

[15]  Wen-Quan Tao,et al.  Field synergy principle for enhancing convective heat transfer--its extension and numerical verifications , 2002 .

[16]  Ahmad Sohankar, Lars Davidson,et al.  EFFECT OF INCLINED VORTEX GENERATORS ON HEAT TRANSFER ENHANCEMENT IN A THREE-DIMENSIONAL CHANNEL , 2001 .

[17]  W. Tao,et al.  Numerical study on laminar convection heat transfer in a channel with longitudinal vortex generator. Part B: Parametric study of major influence factors , 2008 .

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

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

[20]  Wen-Quan Tao,et al.  Numerical study of fluid flow and heat transfer in a flat-plate channel with longitudinal vortex generators by applying field synergy principle analysis , 2009 .

[21]  E. Sparrow,et al.  Fully Developed Flow and Heat Transfer in Ducts Having Streamwise-Periodic Variations of Cross-Sectional Area , 1977 .

[22]  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 .

[23]  Wen-Quan Tao,et al.  A unified analysis on enhancing single phase convective heat transfer with field synergy principle , 2002 .

[24]  R. Shah,et al.  Heat transfer surface enhancement through the use of longitudinal vortices: a review of recent progress , 1995 .

[25]  Felix Hueber,et al.  Principles Of Enhanced Heat Transfer , 2016 .

[26]  Pongjet Promvonge,et al.  Enhanced heat transfer in a triangular ribbed channel with longitudinal vortex generators , 2010 .