Numerical study of the thermo-hydraulic characteristics in a circular tube with ball turbulators. Part 1: PIV experiments and a pressure drop

Abstract In the paper, being the first part out of two (the second one is focused on processes of heat transfer), results of the computer simulations of the flow in a circular pipe with a ball inserts turbulising the flow are presented. An influence of the diameter of balls and their longitudinal distance on a pressure drop in the turbulent flow as a function of the Reynolds number (for Re = 10,000 ÷ 300,000) was analyzed. The investigations were carried out for different diameters of the balls (Db = 7, 10, 13, 16 and 19 mm) and different distances between them (L = 20, 24, 28, 32, 36, 40, 48, 60 and 85 mm) at a constant inner diameter of the tube (Dp = 26 mm). The results indicate that for the whole tested range of ball diameters and their longitudinal arrangements, there is an analytical dependency which allows for expressing a friction factor by the relationship: f = A⋅ReB. The constants A and B were functions of two variables: a dimensionless diameter of the ball (X = Db/Dp) and a dimensionless longitudinal distance between balls (Y = L/Dp). These two constants are closely related. They can be calculated analytically for the entire range of X and Y using a formula of the fourth order surface polynomial (15 coefficients of that polynomial are presented in the paper). The paper presents also experimental investigations carried out using a PIV (Particle Image Velocimetry) apparatus. A comparative analysis of selected inserts and numerical calculations was the goal. The obtained results show a good correlation between the experiment and computer modelling.

[1]  Pongjet Promvonge,et al.  Heat transfer behaviors in a tube with combined conical-ring and twisted-tape insert ☆ , 2007 .

[2]  S. Chang,et al.  Heat transfer and pressure drop in a square spiral channel roughened by in-line skew ribs , 2011 .

[3]  P. G. Vicente,et al.  Flow pattern assessment in tubes with wire coil inserts in laminar and transition regimes , 2007 .

[4]  P. Jasiński,et al.  Corrugated channels heat transfer efficiency analysis based on velocity fields resulting from computer simulation and PIV measurements , 2011 .

[5]  K. Siddiqui,et al.  Investigation of the flow field inside flat-plate collector tube using PIV technique , 2010 .

[6]  Raj M. Manglik,et al.  Low Reynolds number forced convection in three-dimensional wavy-plate-fin compact channels: fin density effects , 2005 .

[7]  P. Jasiński,et al.  Numerical study of the thermo-hydraulic characteristics in a circular tube with ball turbulators. Part 2: Heat transfer , 2014 .

[8]  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 .

[9]  Henryk Charun,et al.  Heat transfer and pressure drop in a vertical tube with a nodular turbulizer , 2008 .

[10]  A. Zachár,et al.  Analysis of coiled-tube heat exchangers to improve heat transfer rate with spirally corrugated wall , 2010 .

[11]  P. G. Vicente,et al.  Flow field and heat transfer investigation in tubes of heat exchangers with motionless scrapers , 2011 .

[12]  Pongjet Promvonge,et al.  Heat transfer and turbulent flow friction in a circular tube fitted with conical-nozzle turbulators ☆ , 2007 .

[13]  Enyu Wang,et al.  Numerical investigation of turbulent flow and heat transfer in a channel with novel longitudinal vortex generators , 2012 .

[14]  Piotr Jasiński,et al.  Numerical Study of Friction Factor and Heat Transfer Characteristics for Single-Phase Turbulent Flow in Tubes with Helical Micro-Fins , 2012 .

[15]  Michele Ciofalo,et al.  Numerical prediction of turbulent flow and heat transfer in helically coiled pipes , 2010 .

[16]  The Particle Image Velocimetry Experimental Study of Flame Extinction in Standard Square Flammability Column Resulting From Stretching , 2011 .

[17]  Aydın Durmuş,et al.  Heat transfer and exergy loss in cut out conical turbulators , 2004 .

[18]  Smith Eiamsa-ard,et al.  Experimental investigation of convective heat transfer and pressure loss in a round tube fitted with circular-ring turbulators☆ , 2010 .

[19]  Karen A. Thole,et al.  Heat transfer augmentation along the tube wall of a louvered fin heat exchanger using practical delta winglets , 2008 .