Arthur E. Bergles

Heat transfer and pressure drop correlations for the rectangular offset strip fin compact heat exchanger

Abstract The development of thermal-hydraulic design tools for rectangular offset strip fin compact heat exchangers and the associated convection process are delineated. On the basis of current understanding of the physical phenomena and enhancement mechanisms, existing empirical f and j data for actual cores are reanalyzed. The asymptotic behavior of the data in the deep laminar and fully turbulent flow regimes is identified. The respective asymptotes for f and j are shown to be correlated by power law expressions in terms of Re and the dimensionless geometric parameters α, δ, and γ. Finally, rational design equations for f and j are presented in the form of single continuous expressions covering the laminar, transition, and turbulent flow regimes.

On the Nature of Critical Heat Flux in Microchannels

The critical heat flux (CHF) limit is an important consideration in the design of most flow boiling systems. Before the use of microchannels under saturated flow boiling conditions becomes widely accepted in cooling of high-heat-flux devices, such as electronics and laser diodes, it is essential to have a clear understanding of the CHF mechanism. This must be coupled with an extensive database covering a wide range of fluids, channel configurations, and operating conditions. The experiments required to obtain this information pose unique challenges. Among other issues, flow distribution among parallel channels, conjugate effects, and instrumentation need to be considered. An examination of the limited CHF data indicates that CHF in parallel microchannels seems to be the result of either an upstream compressible volume instability or an excursive instability rather than the conventional dryout mechanism. It is expected that the CHF in parallel microchannels would be higher if the flow is stabilized by an orifice at the entrance of each channel. The nature of CHF in microchannels is thus different than anticipated, but recent advances in microelectronic fabrication may make it possible to realize the higher power levels.

ExHFT for fourth generation heat transfer technology

This review paper considers the many techniques that have been developed to enhance convective heat transfer. A summary is given of the techniques that are effective for the various modes of heat transfer. Of particular interest currently is compound enhancement that involves the simultaneous application of several techniques, so as to produce an enhancement that is larger than the individual techniques operating separately. This is considered fourth generation heat transfer technology. To realize this, there are many experimental challenges to be overcome that relate to obtaining and applying data.

Heat transfer enhancement

Heat transfer is vital in many processes, including electric power generation, automotive propulsion…

An experimental study of critical heat flux in very high heat flux subcooled boiling

Abstract An experimental study of forced convective subcooled boiling heat transfer to water was performed at heat fluxes that ranged beyond 10 8 W m −2 . One of the objectives of this study was to obtain predictive ability for the critical heat flux (CHF) at high heat fluxes. Experiments were performed with metallic tubes having inside diameters ranging from 0.3 to 2.7 mm. Mass fluxes ranged from 5000 to 40 000 kg m −2 s −1 , and exit subcoolings from 40 to 135°C. Exit pressures ranged from 0.2 to 2.2 MPa, and length-to-diameter ratios ranged from 2.0 to 50.0. Single-phase and two-phase pressure drop and heat transfer data were shown to be reasonably well predicted by existing correlations. Over 200 CHF stable data points were obtained. CHF was shown to be an increasing function of both mass flux and subcooling, and an inverse function of diameter. CHF increased for length-to-diameter ratios less than 10, and decreased with increasing exit pressure. Unreasonably low CHF values were obtained for several series of tests; these premature failures are believed to be the result of thermal-hydraulic or nucleation instabilities. A ‘high flux’ CHF data base containing over 700 data points was compiled, and a new statistical correlation was developed. This correlation was tested against a recently published data base, with an average deviation of 19.4%.

An Analytical and Experimental Study of Falling-Film Evaporation on a Horizontal Tube

On propose deux modeles, tous les deux bases sur la definition de trois regions de transfert thermique. Etude experimentale mettant en evidence les effets des differents parametres sur le coefficient de transfert thermique

Evaporation and condensation heat transfer and pressure drop in horizontal, 12. 7-mm microfin tubes with refrigerant 22

Using R-22 as the working fluid, a series of tests was performed to determine the evaporation and condensation performance of three tubes having many small, spiral inner fins. A smooth tube was also tested to establish a basis of comparison

Enhancement of pool boiling

Abstract This review considers the many techniques that have been developed to enhance boiling heat transfer. After introducing the techniques, the applications to pool boiling are described. Comments are offered regarding commercial introduction of this technology and the generations of heat transfer technology; advanced enhancement represents 3rd generation heat transfer technology.

Heat transfer enhancement of heat exchangers

Preface. Introduction to Heat Transfer Enhancement - Preview of Contributions S. Kakac. The Imperative to Enhance Heat Transfer A.E. Bergles. Sustainability Criteria for Heat Exchanger Design N.H. Afgan, M.G. Calvalho. Extended Surface Heat Transfer in Heat Exchangers and Performance Measurements P.J. Heggs. Microfin Tube Technology - The Effects of Spiral Angle on Evaporative Heat Transfer Enhancement S.-Y. Oh, A.E. Bergles. Heat Transfer Enhancement by Wing-Type Longitudinal Vortex Generators and their Application to Finned Oval Tube Heat Exchanger Elements M. Fiebig, Y. Chen. Effect of Fin Heat Conduction on the Performance of Punched Winglets in Finned Oval Tubes Y. Chen, M. Fiebig. Heat Transfer and Fluid Flow in Rib-Roughened Rectangular Ducts B. Sunden. On the Airside Performance of Fin-and-Tube Heat Exchangers C.-C. Wang. Optimum Design of Air-Cooled Fin-and-Tube Heat Exchangers: Accounting for the Effect of Complex Circuiting C.-C. Wang. Flow and Heat Transfer Mechanisms in Plate-and-Frame Heat Exchangers B. Sunden. Heat Transfer Enhancement in a Plate Heat Exchanger with Rib-Roughened Surfaces R. Tauscher, F. Mayinger. Heat Transfer Augmentation in Channels with Porous Copper Inserts T.M. Kuzay, J.T. Collins. Boiling on Structured Surfaces R.L. Webb, L.-H. Chien. Heat Exchangers for Thermoacoustic Refrigerators: Heat Transfer Measurements in Oscillatory Flow C. Herman, M. Wetzel. A Study on the High Performance Ceramic Heat Exchanger for Ultra High Temperatures M. Kumada. Boiling and Evaporation of Falling Film on Horizontal Tubes and its Enhancement on Grooved Tubes Y. Fujita. Numerical and Experimental Investigation of Enhancement of Turbulent Flow Heat Transfer in Tubes by Means of Truncated Hollow Cone Inserts T.Ayhan, et al. Modern Advances in Optical Measuring Techniques -- Tools to Support Energy Conservation F. Mayinger. Enhancement of Combined Heat and Mass Transfer in Rotary Exchangers U. Dinglreiter, F. Mayinger. Advances in Understanding of Flame Acceleration for the Improving of the Combustion Efficiency C. Gerlach, et al. Heat and Mass Transfer with Drying of Water-Based Varnishes J. Mintzlaff, F. Mayinger. Energy Conversion in a Hydrogen Fueled Diesel Engine: Optimization of the Mixture Formation and Combustion P. Prechtl, et al. Enhancement of Heat Transfer with Horizontal Promoters S.U. Onbs oglu, A.N. Egrican. The Effect of Augmented Surfaces on Two-Phase Flow Instabilities S. Kakac. Flow Boiling inside Microfin Tubes: Recent Results and Design Methods J.R. Thome. Flow Boiling of Refrigerant-Oil Mixtures in Plain and Enhanced Tubes J.R. Thome. Influence of Confinement on FC-72 Pool Boiling from a Finned Surface M. Misale, et al. Prediction of Condensation and Evaporation in Micro-Fin and Micro-Channel Tubes R.L. Webb. Performance Enhancement of Heat Exchangers for Semiconductor-Chip Manufacturing Wen-Jei Yang, S. Torii. Evaporation and Condensation Heat Transfer Enhancement for Alternative Refrigerants used in Air-Conditioning Machines T. Ebisu. Development of New Concept Air-Cooled Heat Exchanger for Energy Conservation of Air-Conditioning Machine T. Ebisu. Multi-Hole Cooling Effectiveness on Combustion Chamber Walls B. Leger, P. Andre. Experimental Studies on Influence of Process Variables to the Exergy Losses at the Double Tube Heat Exchangers A. Can, et al. Enhancement of Direct-Contact Heat Transfer in Concentric Annuli T.A. Ozbelge, M.K. Shahidi. U

Swirl flow heat transfer and pressure drop with twisted-tape inserts

Abstract An extended review of the application of twisted-tape inserts in tubular heat exchangers and their thermal-hydraulic performance is presented. Twisted tapes promote enhanced heat transfer by generating swirl or secondary flows, increasing the flow velocity due to the tube partitioning and blockage, and providing an effectively longer helical flow length. Depending on the tape-edge to tube-wall contact, some fin effects may also be present. Their usage in both single-phase and two-phase (boiling and condensation) flows is considered, and heat transfer and pressure drop results from different investigations are presented. The characteristic features of swirl-induced heat transfer enhancement, nature of swirl flows and their scaling, and development of predictive correlations for heat transfer coefficients and friction factors (or pressure drop) are discussed. Also, some aspects of the use of geometrically modified twisted-tape inserts, as well as compound application with other enhancement techniques, are briefly discussed.