Showing papers on "Heat transfer published in 2015"
TL;DR: In this paper, the effect of thermal radiation on magnetohydrodynamics nanofluid flow between two horizontal rotating plates is studied and the significant effects of Brownian motion and thermophoresis have been included in the model of Nanofluide.
700 citations
TL;DR: In this paper, the current status of heat transfer fluid, which is one of the critical components for storing and transferring thermal energy in concentrating solar power systems, is reviewed in detail, particularly regarding the melting temperature, thermal stability limit and corrosion issues.
626 citations
TL;DR: In this paper, a review of organic phase change materials (PCMs) is presented, focusing on three aspects: the materials, encapsulation and applications of organic PCMs, and providing an insight on the recent developments in applications of these materials.
579 citations
TL;DR: It is shown that the synergistic cooperation in the observed recurrent condensation modes leads to improvements in all aspects of heat transfer properties including droplet nucleation density, growth rate, and self-removal, as well as overall heat transfer coefficient.
Abstract: Vapor condensation plays a key role in a wide range of industrial applications including power generation, thermal management, water harvesting and desalination. Fast droplet nucleation and efficient droplet departure as well as low interfacial thermal resistance are important factors that determine the thermal performances of condensation; however, these properties have conflicting requirements on the structural roughness and surface chemistry of the condensing surface or condensation modes (e.g., filmwise vs dropwise). Despite intensive efforts over the past few decades, almost all studies have focused on the dropwise condensation enabled by superhydrophobic surfaces. In this work, we report the development of a bioinspired hybrid surface with high wetting contrast that allows for seamless integration of filmwise and dropwise condensation modes. We show that the synergistic cooperation in the observed recurrent condensation modes leads to improvements in all aspects of heat transfer properties including droplet nucleation density, growth rate, and self-removal, as well as overall heat transfer coefficient. Moreover, we propose an analytical model to optimize the surface morphological features for dramatic heat transfer enhancement.
424 citations
TL;DR: The preparation of nanofluids by various techniques, methods of stabilization, stability measurement techniques, thermal conductivity and heat capacity studies, proposed mechanisms of heat transport, theoretical models on thermal Conductivity, factors influencing k and the effect of nanoinclusions in PCM are discussed in this review.
341 citations
TL;DR: In this article, the authors reported measured vapor generation efficiencies of 69% at solar concentrations of 10 sun using graphitized carbon black, carbon black and graphene suspended in water, representing a significant improvement in both transient and steady-state performance over previously reported results.
333 citations
TL;DR: In this article, a literature review on the basic and applied research in RHC systems for the built environment is conducted, in terms of thermal comfort, thermal analysis including heat transfer model, heating/cooling capacity, CFD analysis, energy simulation, system configuration and control strategies.
322 citations
TL;DR: In this article, the effects of variable surface heat flux and first-order chemical reaction on MHD flow and radiation heat transfer of nanofluids against a flat plate in porous medium were investigated.
317 citations
TL;DR: In this paper, the effect of the squeeze number, nanofluid volume fraction, Hartmann number and heat source parameter on flow and heat transfer was investigated, and the results showed that skin friction coefficient increases with increase of the Nusselt number and Hartmann numbers but it decreases with an increase in the volume fraction.
311 citations
TL;DR: In this article, a new cooling method for cylindrical batteries which is based on mini-channel liquid cooled cylinder is proposed, and the effects of channel quantity, mass flow rate, flow direction and entrance size on the heat dissipation performance were investigated numerically.
307 citations
TL;DR: In this paper, the augmentation in heat transfer for a shell and tube type LHSU is estimated by carrying out experimental analysis with three longitudinal fins installed on the heat transfer fluid (HTF) tube.
TL;DR: In this paper, the MHD laminar boundary layer flow with heat and mass transfer of an electrically conducting water-based nanofluid over a nonlinear stretching sheet with viscous dissipation effect is investigated numerically.
TL;DR: In this article, the authors investigated the role of the sensible heat of the reservoir and ambient heat transfer in hydrate dissociation in natural gas hydrate reformation and ice generation.
TL;DR: In this paper, the effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo-Kleinstreuer-Li) correlation.
Abstract: In this paper magnetohydrodynamic free convection flow of CuO–water nanofluid in a square enclosure with a rectangular heated body is investigated numerically using Lattice Boltzmann Method (LBM) scheme. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. The influence of pertinent parameters such as Hartmann number, nanoparticle volume fraction and Rayleigh number on the flow, heat transfer and entropy generation have been examined. The results show that the heat transfer rate and Dimensionless entropy generation number increase with increase of the Rayleigh number and nanoparticle volume fraction but it decreases with increase of the Hartmann number.
TL;DR: In this paper, several researches on the micro/nanostructured surfaces that have been designed to enhance boiling heat transfer are introduced and closely reviewed, and the special features of the existing surfaces capable of enhancing BoT are summarized.
TL;DR: In this paper, different nanofluids were developed by mixing a water base fluid with magnetic nanoparticles, and thermal properties such as thermal conductivity and viscosity of the obtained nanoparticles were investigated.
Abstract: The addition of nanoparticles to a base fluid is one of the significant issues to enhance heat transfer. In this study, different nanofluids were developed by mixing a water base fluid with magnetic nanoparticles. Thermophysical properties such as thermal conductivity and viscosity of the obtained nanofluid were investigated. The effect of different nominal diameters of nanoparticles and concentrations of nanoparticles on the thermal conductivity and viscosity of nanofluids have been examined. Three different diameters of magnetic nanoparticles (about 37 nm, 71 nm, and 98 nm) have been tested in this experimental investigation. Experimental results indicate that thermal conductivity increases as volume fraction increases, and thermal conductivity of the nanofluid increases with a decrease of nanoparticle’s size. Moreover, the nanofluid dynamics viscosity ratio increases with an increase in particle concentration and nanoparticle’s diameter. This paper identifies several important issues that should be considered in future work.
TL;DR: In this paper, the authors summarize the basics of fluctuational electrodynamics, a theoretical framework for the study of radiative heat transfer in terms of thermally excited propagating and evanescent electromagnetic waves.
Abstract: Radiative thermal transport via the fluctuating electromagnetic near-field has recently attracted increasing attention due to its fundamental importance and its impact on a range of applications from data storage to thermal management and energy conversion. After a brief historical account of radiative thermal transport, we summarize the basics of fluctuational electrodynamics, a theoretical framework for the study of radiative heat transfer in terms of thermally excited propagating and evanescent electromagnetic waves. Various approaches to modeling near-field thermal transport are briefly discussed, together with key results and proposals for manipulation and utilization of radiative heat flow. Subsequently, we review the experimental advances in the characterization of both near-field heat flow and energy density. We conclude with remarks on the opportunities and challenges for future explorations of radiative heat transfer at the nanoscale.
TL;DR: A review of analytical, numerical and experimental investigations of melting and ensuing convection of phase change materials within enclosures with different shapes commonly used for thermal energy storage is presented in this paper.
Abstract: A review of analytical, numerical and experimental investigations of melting and ensuing convection of phase change materials within enclosures with different shapes commonly used for thermal energy storage is presented. The common shapes of the containers being rectangular cavities, spherical capsules, tubes or cylinders (vertical and horizontal depending on orientation of gravity) and annular cavities are covered. Studies focusing on melting within rectangular cavities are categorized into two groups. The first one is melting due to isothermal heating on one or more boundaries, whereas the second is the constant heat flux-assisted melting. Moreover, constrained and unconstrained melting in both spherical and horizontal cylindrical containers were discussed. The effects of the concentric geometry and location of the heating source on melting in horizontal annular spaces are presented. The review concentrated on elucidating the heat transfer mechanisms (conduction and convection) during the multiple stages of the melting process and the effects of these mechanisms on the liquid–solid interface shape and its progress, melting rate, charging time of the storage system, etc. The strength of buoyancy driven-convection varies greatly with the dimensionless Rayleigh or Stefan numbers and depends somewhat on the location of heat source and imposed boundary condition. High dimensionless numbers and/or side position of the heat source ensure the dominant role of natural convection melting, otherwise conduction will be responsible for major melting within the container. Furthermore, the geometrical parameters such as the aspect ratio in rectangular containers and vertical cylindrical ones, diameter or radius in spherical capsules and horizontal cylindrical vessels, and eccentricity in annular cavities are reviewed. In addition, the parameters affecting the thermal behavior of the melting process in various enclosures, i.e. the Nusselt, Rayleigh, Stefan, Prandtl and Fourier numbers and are reviewed.
TL;DR: In this article, the development of the effective thermal conductivity models for the nanoporous silica aerogel insulation material was summarized, and the procedure of establishing the effective heat transfer model of the aerogels insulation material from nanoscale to macroscale was introduced by taking their previous work as an illustration.
TL;DR: In this article, an air-cooled heat sink considering heat conduction plus side-surface convection is presented, and a postprocessing procedure is described to synthesize manifold or "watertight" solid model computer-aided design (CAD) geometry from 3D point cloud data extracted from the optimization result.
Abstract: Topology optimization of an air-cooled heat sink considering heat conduction plus side-surface convection is presented. The optimization formulation is explained along with multiple design examples. A postprocessing procedure is described to synthesize manifold or “water-tight” solid model computer-aided design (CAD) geometry from three-dimensional (3D) point-cloud data extracted from the optimization result. Using this process, a heat sink is optimized for confined jet impingement air cooling. A prototype structure is fabricated out of AlSi12 using additive layer manufacturing (ALM). The heat transfer and fluid flow performance of the optimized heat sink are experimentally evaluated, and the results are compared with benchmark plate and pin-fin heat sink geometries that are conventionally machined out of aluminum and copper. In two separate test cases, the experimental results indicate that the optimized ALM heat sink design has a higher coefficient of performance (COP) relative to the benchmark heat sink designs.
TL;DR: In this article, the effect of spatially variable magnetic field on ferrofluid flow and heat transfer is investigated and the combined effects of ferrohydrodynamic and magnetohydrodynamic have been taken into account.
Abstract: Effect of spatially variable magnetic field on ferrofluid flow and heat transfer is investigated. The enclosure is filled with Fe3O4–water nanofluid. Control volume based finite element method (CVFEM) is applied to solve the governing equations. The combined effects of ferrohydrodynamic and magnetohydrodynamic have been taken into account. The influences of Magnetic number, Hartmann number, Rayleigh number and nanoparticle volume fraction on the flow and heat transfer characteristics have been examined. Results show that enhancement in heat transfer decrease with increase of Rayleigh number while for two other active parameters different behavior is observed. Also it can be concluded that Nusselt number is an increasing function of Magnetic number, Rayleigh number and nanoparticle volume fraction while it is a decreasing function of Hartmann number.
TL;DR: In this paper, the authors provide a critical review of the analysis of heat transfer by borehole and foundation pile ground heat exchangers with an emphasis on different analytical models, including heat-source models, short-time models, models for energy piles, in situ thermal-response tests, indoor sandbox experiments, and parameter estimation as an inverse problem.
TL;DR: In this article, carbon fibers were added to a phase change material (PCM) to enhance its heat transfer potentials and various strategies were adopted to manage temperature distribution around a single AA-battery-like simulator.
TL;DR: In this paper, the thermal performance of building walls integrated with phase change materials (PCM) was evaluated in terms of heat flux reduction and heat transfer time delay, and the results showed that the optimal location for a PCMTS within the wall cavities is critical for heat transfer reduction and management.
TL;DR: In this paper, the authors present an updated review of properties of nanofluids, such as physical (thermal conductivity) and rheological properties, with emphasis on their heat transfer enhancement characteristics.
TL;DR: In this paper, the thermal characteristics of a finned heat pipe-assisted latent heat thermal energy storage system are investigated numerically using a transient two-dimensional finite volume based model employing enthalpy-porosity technique.
TL;DR: In this paper, water-based nanofluids have been used to enhance the heat transfer performance of a car radiator by adding ZnO nanoparticles to base fluid in different volumetric concentrations (0.01, 0.08), 0.2% and 0.3%).
TL;DR: In this article, an analytical model of heat transfer in polymer foams and a CO 2 foaming process for the preparation of micro/nano-cellular polymer materials for insulating applications are reviewed.
TL;DR: The effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance is shown.
Abstract: Water vapor condensation is commonly observed in nature and routinely used as an effective means of transferring heat with dropwise condensation on nonwetting surfaces exhibiting heat transfer improvement compared to filmwise condensation on wetting surfaces. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings that either have challenges with chemical stability or are so thick that any potential heat transfer improvement is negated due to the added thermal resistance of the coating. In this work, we show the effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance. Heat transfer enhancements of 4× were demonstrated compared to filmwise condensation, and the robustness of these CVD coatings was superior to typical hydrophobic monolayer coatings. Our results indicate that graphene is a promising surface coating ...
TL;DR: In this paper, a paraffin-nanomagnetite (Fe3O4) composites (PNMC) were prepared by a dispersion technique to enhance their thermal properties.