The effects of vortex characteristics on performance of coiled wire turbulators used for heat transfer augmentation

The augmentation of the heat transfer by inserting different type turbulators into the channels is the conventional passive enhancement method. The coiled wire is one of the common heat transfer enhancement devices. These turbulators generate almost-periodic vortices into the flow while increasing the heat transfer rate. In this study, the properties of these vortices (i.e. the vortex shedding frequency and amplitudes of the pressure fluctuations of the vortices), flow (vortex)-acoustic coupling and the relation between entropy generation and vortex characteristics were investigated experimentally. Strouhal–Re–Ns,a and Prms–Re–Ns,a variations were presented graphically. It was observed that as the pitch increases, the vortex shedding frequencies decrease and the maximum amplitudes of pressure fluctuation of vortices produced by coiled wire turbulators occur with small pitches. In addition, the effects of the turbulators on the heat transfer, friction factor and performance characteristics were investigated. The coiled wires were thermodynamically advantageous (Ns,a<1) up to 13,000 Reynolds number.

[1]  M. P. Païdoussis,et al.  Fluidelastic vibration of cylinder arrays in axial and cross flow: State of the art , 1981 .

[2]  D. Rockwell,et al.  Oscillator-Model Approach To Theidentification And Assessment Offlow-Induced Vibrations In A System , 1980 .

[3]  A. Bergles,et al.  PERFORMANCE EVALUATION CRITERIA FOR ENHANCED HEAT TRANSFER SURFACES , 1974 .

[4]  V. Zimparov,et al.  Performance evaluation criteria for enhanced heat transfer surfaces , 1994 .

[5]  J. P. Chiou,et al.  Experimental investigation of the augmentation of forced convection heat transfer in a circular tube using spiral spring inserts , 1987 .

[6]  Samir Ziada,et al.  Flow impingement as an excitation source in control valves , 1989 .

[7]  Adrian Bejan,et al.  Method of entropy generation minimization, or modeling and optimization based on combined heat transfer and thermodynamics , 1996 .

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

[9]  Noriaki Ishii,et al.  Dynamic stability criterion for reed valves in refrigerant compressors , 1993 .

[10]  S. B. Uttarwar,et al.  Augmentation of Laminar Flow Heat Transfer in Tubes by Means of Wire Coil Inserts , 1985 .

[11]  Predrag Stojan Hrnjak,et al.  Acoustic resonance in plate heat exchangers , 1998 .

[12]  Yoshiaki Miyamoto,et al.  Thermal hydraulic study on a high-temperature gas–gas heat exchanger with helically coiled tube bundles , 1998 .

[13]  Shinji Nakagawa,et al.  Heat transfer in channel flow around a rectangular cylinder , 1998 .

[14]  M. J. Pettigrew,et al.  Flow-induced vibration : recent findings and open questions , 1998 .

[15]  Adrian Bejan,et al.  Thermodynamic optimization of geometry in engineering flow systems , 2001 .

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

[17]  Y. Jaluria,et al.  An Introduction to Heat Transfer , 1950 .

[18]  S. J. Kline,et al.  Describing Uncertainties in Single-Sample Experiments , 1953 .

[19]  Kenan Yakut,et al.  Flow-induced vibration analysis of conical rings used for heat transfer enhancement in heat exchangers , 2004 .

[20]  Y. N. Chen.  Flow-Induced Vibration and Noise in Tube-Bank Heat Exchangers Due to von Karman Streets , 1968 .

[21]  M. Dietrich,et al.  Heat transfer for forced convection past coiled wires , 1990 .

[22]  Sergio Viçosa Möller,et al.  On the fluctuating wall pressure field in tube banks , 2001 .

[23]  Lawrence E. Kinsler,et al.  Fundamentals of acoustics , 1950 .

[24]  Samir Ziada,et al.  A Theoretical Model for Self-Excited Vibrations in Hydraulic Gates, Valves and Seals , 1980 .

[25]  Samir Ziada,et al.  Flow Periodicity and Acoustic Resonance in Parallel Triangle Tube Bundles , 1997, 4th International Symposium on Fluid-Structure Interactions, Aeroelasticity, Flow-Induced Vibration and Noise: Volume II.

[26]  Donald Rockwell,et al.  Toward Attenuation of Self-Sustained Oscillations of a Turbulent Jet Through a Cavity , 1983 .