Showing papers on "Heat transfer coefficient published in 2013"
TL;DR: In this article, the authors characterized pool boiling on surfaces with wettabilities varied from superhydrophobic to super-hydrophilic, and provided nucleation measurements, and developed an analytical model that describes how biphilic surfaces effectively manage the vapor and liquid transport, delaying critical heat flux and maximizing the heat transfer coefficient.
428 citations
TL;DR: In this paper, free convection heat transfer in a concentric annulus between a cold square and heated elliptic cylinders in the presence of magnetic field is investigated, and the Lattice Boltzmann method is applied to solve the governing equations.
284 citations
TL;DR: In this article, a linear interpolation between the Nusselt numbers at Re −2300 and Re −4000 is presented, based on the results of a paper published recently.
280 citations
TL;DR: In this paper, a consolidated database for flow boiling in mini/micro-channels is amassed from 31 sources, of which 10,805 data points are designated as pre-dryout.
279 citations
TL;DR: In this paper, a critical review of the current state of research in microchannels is presented with a focus on the future research needs, including single-phase gas flow, enhancement in singlephase liquid flow and flow boiling, flow boiling instability, condensation, electronics cooling, and microscale heat exchangers.
Abstract: Heat transfer and fluid flow in microchannels have been topics of intense research in the past decade. A critical review of the current state of research is presented with a focus on the future research needs. After providing a brief introduction, the paper addresses six topics related to transport phenomena in microchannels: single-phase gas flow, enhancement in single-phase liquid flow and flow boiling, flow boiling instability, condensation, electronics cooling, and microscale heat exchangers. After reviewing the current status, future research directions are suggested. Concerning gas phase convective heat transfer in microchannels, the antagonist role played by the slip velocity and the temperature jump that appear at the wall are now clearly understood and quantified. It has also been demonstrated that the shear work due to the slipping fluid increases the effect of viscous heating on heat transfer. On the other hand, very few experiments support the theoretical models and a significant effort should be made in this direction, especially for measurement of temperature fields within the gas in microchannels, implementing promising recent techniques such as molecular tagging thermometry (MTT). The single-phase liquid flow in microchannels has been established to behave similar to the macroscale flows. The current need is in the area of further enhancing the performance. Progress on implementation of flow boiling in microchannels is facing challenges due to its lower heat transfer coefficients and critical heat flux (CHF) limits. An immediate need for breakthrough research related to these two areas is identified. Discussion about passive and active methods to suppress flow boiling instabilities is presented. Future research focus on instability research is suggested on developing active closed loop feedback control methods, extending current models to better predict and enable superior control of flow instabilities. Innovative high-speed visualization and measurement techniques have led to microchannel condensation now being studied as a unique process with its own governing influences. Further work is required to develop widely applicable flow regime maps that can address many fluid types and geometries. With this, condensation heat transfer models can progress from primarily annular flow based models with some adjustments using dimensionless parameters to those that can directly account for transport in intermittent and other flows, and the varying influences of tube shape, surface tension and fluid property differences over much larger ranges than currently possible. Electronics cooling continues to be the main driver for improving thermal transport processes in microchannels, while efforts are warranted to develop high performance heat exchangers with microscale passages. Specific areas related to enhancement, novel configurations, nanostructures and practical implementation are expected to be the research focus in the coming years.
227 citations
TL;DR: Based on Fourier's law and the Seebeck effect, the authors in this article presented a mathematical model of a TEG device using the exhaust gas of vehicles as heat source, and the results showed that the output power and efficiency increase significantly by changing the convection heat transfer coefficient of the high temperature side than that of low temperature side.
227 citations
TL;DR: In this article, an experimental study on the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and different volume concentrations of Al 2 O 3 (0.3-2)% flowing in a horizontal shell and tube heat exchanger counter flow under turbulent flow conditions is investigated.
219 citations
TL;DR: In this article, the authors demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil.
Abstract: Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer
213 citations
TL;DR: In this paper, the effect of inserting metal foams in the receiver tube of a parabolic trough collector on heat transfer was investigated, and the effects of layout (top/bottom), geometrical parameter (H ), and porosity ( φ ) on the flow resistant, heat transfer and thermo-hydraulic performance were analyzed.
210 citations
TL;DR: In this article, the overall heat transfer coefficient of CuO/water nanofluids is investigated experimentally under laminar flow regime (100 ǫ/ǫ, Re  ≥ 1000) in a car radiator.
TL;DR: In this article, the heat transfer performance of the automobile radiator is evaluated experimentally by calculating the overall heat transfer coefficient (U ) according to the conventional ǫ-NTU technique.
01 Jun 2013
TL;DR: This work demonstrates immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil, and offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer.
Abstract: Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer
TL;DR: In this paper, the heat transfer coefficients and friction factor with SiO2/water nanofluid up to 4% particle volume concentration are determined for flow in a circular tube under constant heat flux boundary condition.
TL;DR: In this article, the heat transfer coefficient and friction factor of the nanofluids flowing in a horizontal tube under laminar flow conditions, experimentally, have been presented.
TL;DR: In this paper, the authors investigated the heat transfer enhancement of micro-channel heat sinks with periodic expansion-constriction cross-sections both experimentally and numerically, and found that the numerical predictions of apparent friction factor and Nusselt number are in good agreement with experimental data.
TL;DR: In this paper, the experimental results and the potential performance of the investigation on flat solar thermal collectors using nanofluids as innovative heat transfer fluids for solar energy applications were reported.
TL;DR: In this paper, the authors explored the forced convective heat transfer performance of using Al2O3/water nanofluid to replace the pure water as the coolant in a copper minichannel heat sink.
TL;DR: In this paper, a new universal approach to predicting the condensation heat transfer coefficient for mini/micro-channel flows is proposed that is capable of tackling many fluids with drastically different thermophysical properties and very broad ranges of all geometrical and flow parameters of practical interest.
TL;DR: In this article, the effect of fluid flow and geometrical parameters on heat transfer rate in shell and coiled tube heat exchangers has been investigated experimentally using Wilson plots.
TL;DR: In this paper, the effect of mean diameter of nanoparticles on the convective heat transfer and pressure drop studied at nanoparticle volume concentration from 0.01 to 0.02 by volume.
TL;DR: In this paper, the melting of lauric acid in a rectangular thermal storage unit heated from one side was studied and an experimental effort was made to visualize temperature field and melt front evolution during solid-liquid phase change process.
TL;DR: In this paper, the authors developed structure features to control the bubble trajectory for enhancing the heat transfer coefficient and creating separate liquid and vapor pathways that result in an increased critical heat flux (CHF).
Abstract: Evaporation momentum force arises due to the difference in liquid and vapor densities at an evaporating interface. The resulting rapid interface motion increases the microconvection heat transfer around a nucleating bubble in pool boiling. Microstructure features are developed on the basis of this hypothesis to control the bubble trajectory for (i) enhancing the heat transfer coefficient, and (ii) creating separate liquid and vapor pathways that result in an increased critical heat flux (CHF). An eightfold higher heat transfer coefficient (629 000 W/m2 °C) and two-and-half times higher CHF (3 MW/m2) over a plain copper surface were achieved with water.
TL;DR: In this paper, the heat transfer and pressure drop of nanofluids containing carbon nanotubes in a horizontal circular tube are experimentally investigated, and the results suggest that the nanophluids at low concentration enhance the convective heat transfer with little extra penalty in pump power, thus have great potential for applications in heat transfer systems.
TL;DR: In this article, the most important parameters both geometrical (porosity, pore density, and foam core height) and operative (air mass flow rate, imposed heat flux) affecting the heat transfer and fluid flow behavior of these enhanced surfaces are analyzed and discussed.
TL;DR: In this article, numerical simulations of single elongated bubbles in flow boiling conditions within circular microchannels were performed, where thin-film evaporation was proved to be the dominant heat transfer mechanism in the liquid film region between the wall and the elongated bubble.
TL;DR: In this paper, the capacity of dense suspensions of solid particles to transfer concentrated solar power from a tubular receiver to an energy conversion process by acting as a heat transfer fluid was demonstrated.
TL;DR: In this article, the authors investigated the thermophysical properties, pressure drop and heat transfer performance of Al2O3 nanoparticles suspended in R-134a, and they used a model from existing studies to determine the thermal conductivity and viscosity of the nanorefrigerants for the nanoparticle concentrations of 1 to 5 vol%.
TL;DR: In this article, a new correlation was developed for laminar flow in helically coiled tubes, which can predict the experimental heat transfer data very well, and the Seban and McLaughlin correlation can accurately predict the thermal behavior of water and nanofluids when nanof-luid properties are taken into account.
TL;DR: In this article, the heat transfer performance of the plate heat exchanger has been investigated using different nanofluids (CeO2, Al2O3, TiO2 and SiO2) for various volume flow rates and wide range of concentrations.