Boiling Heat Transfer on the Micro-Textured Interfaces (original) (raw)
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Boiling and quenching heat transfer advancement by nanoscale surface modification
Scientific reports, 2017
All power production, refrigeration, and advanced electronic systems depend on efficient heat transfer mechanisms for achieving high power density and best system efficiency. Breakthrough advancement in boiling and quenching phase-change heat transfer processes by nanoscale surface texturing can lead to higher energy transfer efficiencies, substantial energy savings, and global reduction in greenhouse gas emissions. This paper reports breakthrough advancements on both fronts of boiling and quenching. The critical heat flux (CHF) in boiling and the Leidenfrost point temperature (LPT) in quenching are the bottlenecks to the heat transfer advancements. As compared to a conventional aluminum surface, the current research reports a substantial enhancement of the CHF by 112% and an increase of the LPT by 40 K using an aluminum surface with anodized aluminum oxide (AAO) nanoporous texture finish. These heat transfer enhancements imply that the power density would increase by more than 100%...
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering, 2019
The higher-thermal conductive Cu-Al 2 O 3 nanoparticles are deposited on the copper surface by using single-step electrodeposition technique. The developed Cu-Al 2 O 3 nanocomposite-coated surfaces attained excellent adhesiveness with copper substrate. Again, the surface morphology parameters like wettability, roughness, porosity, and porous layer thickness, as per the necessity in structured surfaces, can be easily managed by managing the electrodeposition parameters like potential difference, deposition time, current density, and electrolyte concentration. The surface morphology characterization is carried out with respect to the wettability, roughness, coating thickness, porosity, and average pore diameter. The flow boiling heat transfer experiments at different mass flow rates with deionized (DI) water are carried out in a minichannel of developed experimental setup. The Cu-Al 2 O 3 coating offers lower thermal resistance due to its higher thermal conductivity and lower coating thickness. Again, the percentage enhancement in critical heat flux (CHF) and boiling heat transfer coefficient (BHTC) of the Cu-Al 2 O 3-coated surfaces is decreased with the increase in mass flow rate, which is owing to the partial wetting of the pores at higher mass flow rate. The maximum augmentations in BHTC and CHF for the coated surfaces are achieved up to 84% and 86% as compared to the bare surface, respectively, which are due to the improvement in surface wettability and formation of huge number of cavities/pores on coated surfaces. Thus, the porous surface with minichannel is the potential candidate for the microelectronics cooling devices due to its compact size, lower heating surface temperature, higher CHF, and higher BHTC.
Enhancement of flow boiling heat transfer in microchannels by nano- and micro-surface treatments
Mécanique & Industries, 2011
Ce papier présente nos études sur le transfert thermique en ébullition convective dans les microcanaux dont l'objectif est de développer des systèmes de refroidissement compacts qui peuvent s'adapter aux composants de puissance miniaturisés. Les nano-et micro-structurations de surface ont été utilisées comme des techniques innovantes permettant d'améliorer la performance de transfert thermique et de retarder le phénomène d'assèchement intermittent. It a été observé que les surfaces contenant des microstructures ont de meilleurs coefficients de transfert thermique par rapport aux surfaces lisses (jusqu'à 85% d'amélioration). En particulier, en rendant cette surface structurée plus mouillante, l'assèchement intermittent a significativement retardé.
Advances in Boiling Heat Transfer Enhancement using Micro/Nano Structured Surfaces
European Journal of Engineering Research and Science
In this article we present an inclusive review of research carried out in the field of phase change heat transfer enhancement. First, we discuss about different kinds of conventional heat transfer enhancement techniques performed in convection heat transfer related heat exchangers. Next, we present the advantages of implementing phase change heat transfer and report a brief introduction to the physics behind the phase change (boiling) heat transfer phenomenon. We present a well explained data about different kinds of enhancement techniques using micro and nano scale structures on heat transfer surface/device to increase the limit of boiling heat transfer. The entire review article is broadly divided into two categories: first the investigation related to fluid flow or transport mechanism over the micro/nano structured surface which is of crucial importance, second is the actual computational and experimental methods to achieve higher heat transfer capability in terms of critical hea...
Analysis of Enhanced Pool Boiling Heat Transfer on Laser—Textured Surfaces
Energies
Enhancement of pool boiling heat transfer can be attained with a number of passive and active techniques. The paper experimentally analyses the impact of laser treatment of the copper surfaces on pool boiling heat transfer of distilled water and ethyl alcohol. The samples were modified with a laser beam to produce longitudinal grooves of highly developed microstructures in the laser textured area. Specimens of different groove depths, groove widths and micro-fin widths were produced. The results indicate a significant influence of laser processing on heat flux dissipated from the surfaces and heat transfer enhancement for all the samples tested. The experimental results have been generalized in the form of a heat flux correlation based on a modified model of enhanced pool boiling heat transfer.
Volume 5B: Heat Transfer — General Interest; Internal Air Systems; Internal Cooling, 2021
Transpiration cooling is able to provide more uniform coolant coverage than film cooling to effectively protect the component surface from contacting the hot gas. Due to numerous coolant ejection outlets within a small area at the target surface, the experimental thermo-fluid investigation on transpiration cooing becomes a significant challenge. Two classic methods to investigate film cooling, the steady-state foil heater method and the transient thermography technique, both fail for transpiration cooling because the foil heater would block numerous coolant outlets, and the semi-infinite solid conduction model no longer holds for porous plates. In this study, a micro-lithography method to fabricate a silver coil pattern on top of the additively manufactured polymer porous media as the surface heater was proposed. The circuit was deliberately designed to cover the solid surface in a combination of series connection and parallel connection to ensure the power in each unit cell area at...
2010 14th International Heat Transfer Conference, IHTC 14, 2010
The National Renewable Energy Laboratory (NREL) is leading a national effort to develop next-generation cooling technologies for hybrid vehicle electronics, as part of the Advanced Power Electronics and Electrical Machines program area in the U.S. Department of Energy's (DOE's) Vehicle Technologies Program. The overarching goal is to reduce the size, weight, and cost of power electronic modules that convert direct current from the batteries to alternating current for the motor, and vice versa. Aggressive thermal management techniques help in achieving the goals of increased power density and reduced weight and volume, while keeping the chip temperatures within acceptable limits. The viability of aggressive cooling schemes such as spray and jet impingement in conjunction with enhanced surfaces is being explored as part of the program. In this work, we present results from a series of experiments with pool and spray boiling on enhanced surfaces, such as a microporous layer of copper and copper nanowires, using HFE-7100 as the working fluid. Spray impingement on the microporous coated surface showed an enhancement of 100%−300% in the heat transfer coefficient at a given wall superheat with respect to spray impingement on a plain surface under similar operating conditions. The critical heat flux also increased by 7%−20%, depending on the flow rates. Heat transfer coefficients obtained on the nanowire-grown surface are considerably better than those obtained on the plain surface, although the enhancement is lower than those obtained on the microporous surface. The critical heat flux is also considerably lower for the nanowire surface than for the plain surface.
Nano Energy
Enhancing boiling heat transfer by surface modification is of critical interest for improving the efficiency of many energy systems and for addressing thermal management bottlenecks in electronics. However, the improvement of all boiling heat transfer characteristics including the critical heat flux, heat transfer coefficient and onset of nucleate boiling, usually has conflicting requirements on surface wettability and morphology. In this work, we develop a two-level hierarchical surface with patterned copper nanowire arrays for boiling heat transfer enhancement. By surrounding long nanowire arrays with short nanowires where microcavities are formed between short nanowire clusters, a novel strategy is reported to improve all the boiling heat transfer characteristics through increasing bubble nucleation site density, capillary-induced liquid rewetting, and the separation of liquid-vapor pathways. Compared to boiling heat transfer performance on the plain copper surface, a 71% higher critical heat flux, a 185% higher heat transfer coefficient as well as a 37% lower onset of nucleate boiling are demonstrated on such two-level hierarchical surfaces. In addition, we correctly predict the effect of surface structure on the boiling heat transfer performance by an analytical model. Through distinguishing the role of different structure morphologies including the improved nucleation site by microcavities, enhanced liquid wicking by nanowires, and continuous liquid supply by long nanowire arrays, we have established a comprehensive understanding on the relation between the surface structures and boiling heat transfer characteristics.