ENHANCED HEAT TRANSFER FOR IMPROVED ICE-FREE CRYOPRESERVATION-INTERPLAY BETWEEN COOLING AND REWARMING

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

An experimental investigation on the enhancement of convective heat transfer of a flat plate and LED using ionic wind is reported. The natural and forced convection heat transfers were considered. The ionic wind describes the generation of airflow between two electrodes held at a potential difference and is known to enhance heat transfer. An in-depth review of literatures is provided, where the enhancement of heat transfer is attributed to the generation of secondary flow and disruption of existing boundary layer. Two experimental setups have been constructed, for the natural convection heat transfer enhancement of a flat plate and for the forced convection heat transfer enhancement of LED. The bulk flow forced convection of the LED was generated by an axial fan. For the investigation with the flat plate, the parameters involved were the applied voltage to generate the ionic wind, the flat plate heat flux, the separation gap of electrodes and the number of emitter electrodes used. As the applied voltage increased, the enhancement increased. While as the flat plate heat flux increased, the enhancement of ionic wind decreased due to overwhelming effects of buoyancy. With separation gaps of g = 1.5 cm and g = 1.75 cm, the ionic wind produced similar enhancements, while the heat transfer enhancement was lower with a separation gap of g = 2 cm. Increasing the number of emitter electrodes did not increase the enhancement as the enhancement was linked to the corona current. The maximum heat transfer enhancement recorded was η = 1.41. For the enhancement of heat transfer of the LED, the parameters investigated were the bulk flow velocity represented by the Reynolds number and the orientation of electrodes relative to the LED. In the laminar flow regime investigated, the effect of the Reynolds number on the heat transfer enhancement was minimum. At a given low power consumption, the ionic wind enhanced setup produced a lower average heat transfer coefficient as compared to those produced by the setup cooled solely by the axial fan. This was due to the significant heat transfer produced by the axial fan at low power. However, as the total consumption of power increased, the heat transfer enhancement of the ionic wind increased beyond the reach of the setup with axial fan. The maximum heat transfer enhancement of the LED was η = 1.38. An analysis of the electrodes geometry was performed and showed that the enhancement of heat transfer was dependent on the orientation of the electrodes relative to the LED. An average Nusselt number correlation was formed.

The growing demand for efficient heat exchangers has promoted extensive research in exploring advanced heat transfer fluids and novel geometries. This paper investigates the heat transfer and pressure drop characteristics in helical coil heat exchanger employing water-based TiO2 as nanofluid. The utilization of nanofluids offers promising enhancements in thermal conductivity and convective heat transfer in heat exchanger applications. The effect of nanofluid concentration and flow rate on heat transfer and pressure drop with varying helical coil diameter performance is investigated. Experimental tests were conducted using a heat exchanger with different helical coil pipe diameters of 9.53mm, 12.7mm and 15.88mm with constant pitch of 30mm and varying concentrations of TiO2 nanoparticles in water (ranging from 0.1% to 0.5% by volume). The heat transfer coefficient and pressure drop were measured at different operating conditions. The results shows that the addition of TiO2 nanoparticles to water significantly enhanced the heat transfer performance in the helical coil heat exchanger. There is an enhancement in heat transfer coefficient with increasing nanofluid concentration and with increase in pipe diameter. The maximum enhancement in heat transfer coefficient is observed at nanofluid concentration of 0.5% and for pipe diameter of 15.88 mm. However, there is increase in pressure drop with increase in nanofluid concentration and with decreasing pipe diameter. The pressure drop found to be higher for nanofluids compared to pure water. The maximum pressure drop is observed at a concentration of 0.5% and for pipe diameter 9.53mm. In conclusion, the use of a water-based TiO2 nanofluid in a helical coil heat exchanger offers improved heat transfer performance compared to pure water. However, the pressure drop also increases with nanofluid concentration and decreasing pipe diameter. Therefore, a trade-off between heat transfer enhancement and pressure drop should be considered in the design and operation of such heat exchangers.

This paper presents results of an experimental investigation on pressure drop and heat transfer for a wide range of Reynolds and Prandtl numbers ranging from 8 < Pr < 60 and 40 < Re < 3500, for flat tubes without and with passive inserts. For three different kinds of passive insert designs, the impact on heat and momentum transfer due to coaction of the total set of passive inserts with different shape and amount was investigated. Experimental results were analyzed regarding two main aspects: Heat transfer mechanisms and pressure drop induced by friction and form drag forces due to the presence of different shapes. After heat and momentum transfer mechanisms for each passive insert design were analyzed, heat transfer and pressure drop enhancement were compared to each other, leading to an efficiency discussion. Different concepts for efficiency evaluation, which are cited in literature, were applied to the presented experimental data. Pros and cons of the different concepts are discussed. Finally, we propose an equation for evaluation of total performance, which fully respects the energetic and exergetic aspects of heat transfer and pressure drop enhancement.

A review on application and heat transfer enhancement of supercritical CO2 in low-grade heat conversion

Experimental and numerical study of air-water mist jet impingement cooling on a cylinder

Enhancement in heat transfer during condensation of an HFO refrigerant on a horizontal tube with 3D fins

Heat transfer in three-phase fluidized beds containing low-density particles

A comprehensive review of pulsating flow on heat transfer enhancement

Unsteady convective heat transfer in air and oil flows past a heated circular cylinder is modeled numerically by solving the unsteady Navier—Stokes and energy equations with the aid of multiblock computational technologies implemented in the VP2/3 code using composite overlapping structured grids of different topology. Enhancement of heat and momentum transfer is associated with a considerable reduction of temperature boundary layer thickness. Main attention is paid to a self-similar flow regime and heat transfer, with the analysis of averaged and fluctuation characteristics and the comparison of constant physical property and inhomogeneous media.

To investigate the effects of the angle of attack of delta winglet vortex generators (VGs) on heat transfer performance and pressure drop penalty of finned flat tube bank, local and average heat transfer characteristics were studied by using analogy between heat and mass transfer with naphthalene sublimation experiments. In order to consider nonuniform fin temperature, the heat transfer rate from fin surfaces was investigated by solving the conduction equation in the fin with a Finite Volume Method on curvilinear coordinate systems based on experimental results of local heat transfer. Three angles of attack (> = 25°, 35°, 45°) are investigated. Without considering the nonuniform fin temperature, increasing the angle of attack, average Nusselt number and friction factor are increased, the heat transfer enhancement on fin surface without mounted VGs is reduced, but the heat transfer enhancement on fin surface mounted with VGs is less affected. Considering the nonuniform fin temperature, the heat transfer enhancement becomes weak as the angle of attack greater than certain value. The numerical calculation shows that the total heat transfer rate from the fin surface mounted with VGs is larger than the total heat transfer rate from the fin surface constructing the same flow channel. Based on a dimensionless factor of the larger the better, JF, the results show that the angle of attack, 40°, has better heat transfer performance for the configurations discussed in this article.

In this work, heat transfer coefficients during condensation of an environment-friendly refrigerant R-1233zd(e) on the outside surface of two cylindrical tubes are individually measured. The cooling water flows inside the tubes and provides cooling to the vapor refrigerant. One tube is a plain smooth tube (smooth both inside and outside) while the other tube is an enhanced tube, with the inside surface having 2D helical ridges and the outside surface having 3D extruded fins. The tests were conducted at the saturation temperature 36.1 °C, a typical temperature in chiller condensers. The results show the overall heat transfer coefficients of the enhanced tube are approximately 8.4 times higher as a result of the heat transfer enhancement on both sides. The condensation heat transfer degrades with an increase in the degree of subcooling, and the trend of degradation is the nearly the same for both the smooth and the enhanced tube, both is smaller than that in the Nusselt correlation. Compared with condensation on the smooth surface, the condensation heat transfer from the enhanced surface is enhanced approximately 10.8 times higher than that on the smooth surface. In addition to enlarged heat transfer area of the extruded fins, the enhancement in the condensation heat transfer is partly attributed to a better condensate draining mechanism of the 3D-structured fins where surface tension plays an important role. Further analysis reveals that heat transfer during the condensation process on the 3D low-fin surface follows the Nusselt correlation with a multiplier that accounts for the enhancement in heat transfer, which is desirably simple approach to modeling condensation heat transfer on the complex 3D enhanced surfaces. This work can lead to more insights into the physical mechanisms during the complex condensation process.

Experimental studies of thermo-aerodynamic characteristics of non-circular ducts with discrete turbulators on walls and interrupted channels have confirmed the rational enhancement of convective heat transfer, in which the growth of heat transfer outstrips or equals the growth of aerodynamic losses. Determining the regularities of rational (energy-saving) enhancement of heat transfer and the proposed method for comparing the characteristics of smooth-channel (without enhancement) heat exchangers with effective analogs provide new results, confirming the high efficiency of vortex enhancement of convective heat transfer in non-circular ducts of plate-finned heat exchange surfaces. This allows creating heat exchangers with much smaller mass and volume for operation in energy-saving modes.

In connection with investigations concerning the core melt/concrete interaction, the enhancement of heat transfer between two horizontal liquid layers by gas injection has been studied using two systems–oil over water and oil over Wood’s metal–with very different density ratios. For the largest gas injection rate (superficial gas velocity 6.3×10−3 m/s), the heat transfer coefficient is increased by a factor of nearly 400 for oil over water and by a factor of ∼10 for oil over Wood’s metal In the core melt/concrete interaction, the superficial gas velocities might be even higher; therefore, the gas-induced enhancement of interfacial heat transfer should be taken into account.

Theoretical and numerical study on new evaluation criteria for longitudinal vortex enhanced heat transfer