Heat transfer enhancement in a tube using circular cross sectional rings separated from wall

A numerical study was undertaken for investigating the heat transfer enhancement in a tube with the circular cross sectional rings. The rings were inserted near the tube wall. Five different spacings between the rings were considered as p = d/2, p = d, p = 3d/2, p = 2d and p = 3d. Uniform heat flux was applied to the external surface of the tube and air was selected as working fluid. Numerical calculations were performed with FLUENT 6.1.22 code, in the range of Reynolds number 4475-43725. The results obtained from a smooth tube were compared with those from the studies in literature in order to validate the numerical method. Consequently, the variation of Nusselt number, friction factor and overall enhancement ratios for the tube with rings were presented and the best overall enhancement of 18% was achieved for Re = 15,600 for which the spacing between the rings is 3d.

[1]  J. P. Hartnett,et al.  Advances in Heat Transfer , 2003 .

[2]  W. Kays,et al.  Turbulent Prandtl number : where are we ? , 1994 .

[3]  U. Gross,et al.  Numerical study of fin-spacing effects in annular-finned tube heat exchangers , 2004 .

[4]  Charles Hirsch,et al.  An introduction to turbulence models , 1990 .

[5]  V. Zimparov,et al.  Enhancement of heat transfer by a combination of three-start spirally corrugated tubes with a twisted tape , 2001 .

[6]  Eric M. Kennedy,et al.  Friction factors for pipe flow of xanthan-based concentrates of fire fighting foams , 2005 .

[7]  Pongjet Promvonge,et al.  Experimental investigation of heat transfer and flow friction in a circular tube fitted with regularly spaced twisted tape elements , 2006 .

[8]  V. Gnielinski.  New equations for heat and mass transfer in turbulent pipe and channel flow , 1976 .

[9]  Paisarn Naphon,et al.  Effect of coil-wire insert on heat transfer enhancement and pressure drop of the horizontal concentric tubes , 2006 .

[10]  Kenan Yakut,et al.  Optimum design-parameters of a heat exchanger having hexagonal fins , 2006 .

[11]  Bengt Sundén,et al.  Performance comparison of some tube inserts , 2002 .

[12]  Ahmet Tandiroglu,et al.  Energy dissipation analysis of transient heat transfer for turbulent flow in a circular tube with baffle inserts , 2006 .

[13]  Sutanu Sarkar,et al.  Application of a Reynolds stress turbulence model to the compressible shear layer , 1990 .

[14]  Zhengguo Zhang,et al.  An experimental heat transfer study for helically flowing outside petal-shaped finned tubes with different geometrical parameters , 2007 .

[15]  B. S. Petukhov.  Heat Transfer and Friction in Turbulent Pipe Flow with Variable Physical Properties , 1970 .

[16]  Gautam Biswas,et al.  Heat transfer and flow structure in laminar and turbulent flows in a rectangular channel with longitudinal vortices , 1995 .

[17]  Pei-Xue Jiang,et al.  Experimental and numerical investigation of convection heat transfer in a rectangular channel with angled ribs , 2006 .

[18]  Pongjet Promvonge,et al.  Experimental investigation of heat transfer and friction characteristics in a circular tube fitted with V-nozzle turbulators☆ , 2006 .

[19]  D. Evin,et al.  Heat transfer enhancement in circular tubes using helical swirl generator insert at the entrance , 2007 .

[20]  B. Baek,et al.  A study on heat transfer enhancement using straight and twisted internal fin inserts , 2006 .

[21]  Pongjet Promvonge,et al.  Heat transfer in a circular tube fitted with free-spacing snail entry and conical-nozzle turbulators ☆ , 2007 .

[22]  Giovanni Tanda,et al.  Heat transfer in rectangular channels with transverse and V-shaped broken ribs , 2004 .

[23]  A. R. Khaled.  Heat transfer enhancement in hairy fin systems , 2007 .

[24]  M. H. Kamran Siddiqui,et al.  Heat transfer augmentation in a heat exchanger tube using a baffle , 2007 .

[25]  Pongjet Promvonge,et al.  Heat transfer augmentation in a circular tube using V-nozzle turbulator inserts and snail entry , 2007 .

[26]  Bayram Sahin,et al.  Performance analysis of a heat exchanger having perforated square fins , 2008 .

[27]  C. Hung,et al.  Numerical study of heat transfer enhancement of a horizontal tube with an eccentrically inserted plate , 1997 .

[28]  B. Launder,et al.  Lectures in mathematical models of turbulence , 1972 .

[29]  Stephen A. Jordan,et al.  The turbulent character and pressure loss produced by periodic symmetric ribs in a circular duct , 2003 .

[30]  Jean-Marie Buchlin,et al.  Convective heat transfer in a channel with perforated ribs , 2002 .

[31]  Shyy Woei Chang,et al.  Turbulent heat transfer and pressure drop in tube fitted with serrated twisted tape , 2007 .

[32]  Masud Behnia,et al.  Reynolds averaged simulation of flow and heat transfer in ribbed ducts , 2002 .

[33]  Developing 3-D turbulent mixed convection in a circular duct inserted with longitudinal strips , 2001 .

[34]  D. R. Oliver,et al.  Heat transfer enhancement in round tube using wire coil: Influence of length and segmentation , 2003 .

[35]  J. San,et al.  Heat transfer enhancement of transverse ribs in circular tubes with consideration of entrance effect , 2006 .

[36]  Giovanni Tanda,et al.  Heat transfer and pressure drop in a rectangular channel with diamond-shaped elements , 2001 .

[37]  Selahaddin Orhan Akansu,et al.  Heat transfers and pressure drops for porous-ring turbulators in a circular pipe , 2006 .