Journal articles on the topic 'Particle Heat Transfer'
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1
Huang, Zheqing, Qi Huang, Yaxiong Yu, Yu Li, and Qiang Zhou. "A Comparative Study of Models for Heat Transfer in Bidisperse Gas–Solid Systems via CFD–DEM Simulations." Axioms 11, no. 4 (April 15, 2022): 179. http://dx.doi.org/10.3390/axioms11040179.
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In this study, flow and heat transfers in bidisperse gas–solid systems were numerically investigated using the computational fluid dynamics–discrete element method (CFD–DEM). Three different models to close the gas–solid heat transfer coefficient for each species of bidisperse systems were compared in the simulations. The effect of the particle diameter ratio and particle number ratio between large and small particles on the particle mean temperature and temperature distribution of each species were systematically investigated. The simulation results show that differences in the particle mean temperature and temperature distribution profiles exist among the three heat transfer models at a higher particle number ratio. The differences between the effects of three heat transfer models on heat transfer properties in bidisperse systems with particle diameter ratios of up to 4 are marginal when the particle number ratio between small and large particles is 1.
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Y. Hashim, Mohamed, Hyun Sik Sim, and Ik-Tae Im. "A Computational Study on Inter-Phase Heat Transfer in a Conical Fluidized Bed Reactor Using Hot Air." International Journal of Air-Conditioning and Refrigeration 29, no. 02 (May 29, 2021): 2150018. http://dx.doi.org/10.1142/s2010132521500188.
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This paper presents a computational study on the inter-phase heat transfer inside a conical fluidized bed reactor when hot air is introduced through the bottom inlet. Two different diameters, 2.0[Formula: see text]mm and 4.0[Formula: see text]mm glass particles are used as the first and second solid phase and hot air is used as the third phase. A gas–particle heat transfer and particle–particle heat transfer are investigated by using computational fluid dynamics. Euler–Euler two-fluid model is used to describe dynamics of particles and fluid flow in the reactor. We observe that gas–particle heat transfer coefficient is large when solid particle is small. This is the same tendency as the gas–particle heat transfer coefficient when cold air is introduced among hot particles. Particle-to-particle heat transfer depends much on the superficial velocity at the inlet.
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Bösenhofer, Markus, Mario Pichler, and Michael Harasek. "Heat Transfer Models for Dense Pulverized Particle Jets." Processes 10, no. 2 (January 26, 2022): 238. http://dx.doi.org/10.3390/pr10020238.
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Heat transfer is a crucial aspect of thermochemical conversion of pulverized fuels. Over-predicting the heat transfer during heat-up leads to under-estimation of the ignition time, while under-predicting the heat loss during the char conversion leads to an over-estimation of the burnout rates. This effect is relevant for dense particle jets injected from dense-phase pneumatic conveying. Heat fluxes characteristic of such dense jets can significantly differ from single particles, although a single, representative particle commonly models them in Euler–Lagrange models. Particle-resolved direct numerical simulations revealed that common representative particles approaches fail to reproduce the dense-jet characteristics. They also confirm that dense clusters behave similar to larger, porous particles, while the single particle characteristic prevails for sparse clusters. Hydrodynamics causes this effect for convective heat transfer since dense clusters deflect the inflowing fluid and shield the center. Reduced view factors cause reduced radiative heat fluxes for dense clusters. Furthermore, convection is less sensitive to cluster shape than radiative heat transfer. New heat transfer models were derived from particle resolved simulations of particle clusters. Heat transfer increases at higher void fractions and vice versa, which is contrary to most existing models. Although derived from regular particle clusters, the new convective heat transfer models reasonably handle random clusters. Contrary, the developed correction for the radiative heat flux over-predicts shading effects for random clusters because of the used cluster shape. In unresolved Euler–Lagrange models, the new heat transfer models can significantly improve dense particle jets’ heat-up or thermochemical conversion modeling.
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Sun, J. G., and M. M. Chen. "Measurement of Surface Heat Transfer Due to Particle Impact." Journal of Heat Transfer 117, no. 4 (November 1, 1995): 1028–35. http://dx.doi.org/10.1115/1.2836277.
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Heat transfer coefficients for a surface continuously impacted by a stream of falling particles in air and in helium were measured as functions of particle flux and particle velocity. The purpose was to provide well-controlled data to clarify the mechanisms of heat transfer in particle suspension flows. The particles were spherical glass beads with mean diameters of 0.5, 1.13, and 2.6 mm. The distribution of the particle impact flux on the surface was determined by deconvolution from the measurement of the total solid masses collected at both sides of a movable splitter plate. The particle velocity was calculated from a simple, well-established model. The experimental results showed that in air, the heat transfer coefficient increases approximately linearly with particle impact flux. At high impact fluxes, the heat transfer coefficient decreases with particle impact velocity, and at low impact fluxes, it increases with particle impact velocity. Furthermore, the heat transfer coefficient decreases drastically with the particle size. In helium gas, it was found that at low particle impact fluxes, the difference between the coefficients in helium and in air is small, whereas at high fluxes, the difference becomes large. A length scale, V/n˙dp2, was used to correlate the data. At low particle Reynolds numbers, gas-mediated heat conduction was identified as the dominant particle/surface heat transfer mechanism, whereas at high particle Reynolds numbers, induced gas convection was the dominant mechanism.
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Luo, Xiaotong, Jiachuan Yu, Bo Wang, and Jingtao Wang. "Heat Transfer and Hydrodynamics in Stirred Tanks with Liquid-Solid Flow Studied by CFD–DEM Method." Processes 9, no. 5 (May 12, 2021): 849. http://dx.doi.org/10.3390/pr9050849.
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The heat transfer and hydrodynamics of particle flows in stirred tanks are investigated numerically in this paper by using a coupled CFD–DEM method combined with a standard k-e turbulence model. Particle–fluid and particle–particle interactions, and heat transfer processes are considered in this model. The numerical method is validated by comparing the calculated results of our model to experimental results of the thermal convection of gas-particle flows in a fluidized bed published in the literature. This coupling model of computational fluid dynamics and discrete element (CFD–DEM) method, which could calculate the particle behaviors and individual particle temperature clearly, has been applied for the first time to the study of liquid-solid flows in stirred tanks with convective heat transfers. This paper reports the effect of particles on the temperature field in stirred tanks. The effects on the multiphase flow convective heat transfer of stirred tanks without and with baffles as well as various heights from the bottom are investigated. Temperature range of the multiphase flow is from 340 K to 350 K. The height of the blade is varied from about one-sixth to one-third of the overall height of the stirred tank. The numerical results show that decreasing the blade height and equipping baffles could enhance the heat transfer of the stirred tank. The calculated temperature field that takes into account the effects of particles are more instructive for the actual processes involving solid phases. This paper provides an effective method and is helpful for readers who have interests in the multiphase flows involving heat transfers in complex systems.
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Gorman, John, and Eph Sparrow. "Fluid flow and heat transfer for a particle-laden gas modeled as a two-phase turbulent flow." International Journal of Numerical Methods for Heat & Fluid Flow 28, no. 8 (August 6, 2018): 1866–91. http://dx.doi.org/10.1108/hff-04-2018-0144.
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Purpose The purpose of this study is to examine the physical processes experienced by a particle-laden gas due to various types of collisions, different heat transfer modalities and jet axis switching. Here, attention is focused on a particle-laden gas subjected to jet axis switching while experiencing fluid flow and heat transfer. Design/methodology/approach The methodology used to model and solve these complex problems is numerical simulation treated here as a two-phase turbulent flow in which the gas and the particles keep their separate identities. For the turbulent flow model, validation was achieved by comparisons with appropriate experimental data. The considered interactions between the fluid and the particles include one-way fluid–particle interactions, two-way fluid–particle interactions and particle–particle interactions. Findings For the fluid flow portion of the work, emphasis was placed on the particle collection efficiency and on independent variables that affect this quantity and the trajectories of the fluid and of the particles as they traverse the space between the jet orifice and the impingement plate. The extent of the effect depended on four factors: particle size, particle density, number of particles and the velocity of the fluid flow. The major effect on the heat transferred to the impingement plate occurred when direct heat transfer between the impinging particles and the plate was taken into account. Originality/value This paper deals with issues never before dealt with in the published literature: the effect of jet axis switching on the fluid mechanics of gas-particle flows without heat transfer and the effect of jet axis switching and the presence of particles on jet impingement heat transfer. The overall focus of the work is on the impact of jet axis switching on particle-laden fluid flow and heat transfer.
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Niazi Ardekani, M., O. Abouali, F. Picano, and L. Brandt. "Heat transfer in laminar Couette flow laden with rigid spherical particles." Journal of Fluid Mechanics 834 (November 17, 2017): 308–34. http://dx.doi.org/10.1017/jfm.2017.709.
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We study heat transfer in plane Couette flow laden with rigid spherical particles by means of direct numerical simulations. In the simulations we use a direct-forcing immersed boundary method to account for the dispersed phase together with a volume-of-fluid approach to solve the temperature field inside and outside the particles. We focus on the variation of the heat transfer with the particle Reynolds number, total volume fraction (number of particles) and the ratio between the particle and fluid thermal diffusivity, quantified in terms of an effective suspension diffusivity. We show that, when inertia at the particle scale is negligible, the heat transfer increases with respect to the unladen case following an empirical correlation recently proposed in the literature. In addition, an average composite diffusivity can be used to approximate the effective diffusivity of the suspension in the inertialess regime when varying the molecular diffusion in the two phases. At finite particle inertia, however, the heat transfer increase is significantly larger, smoothly saturating at higher volume fractions. By phase-ensemble-averaging we identify the different mechanisms contributing to the total heat transfer and show that the increase of the effective conductivity observed at finite inertia is due to the increase of the transport associated with fluid and particle velocity. We also show that the contribution of the heat conduction in the solid phase to the total wall-normal heat flux reduces when increasing the particle Reynolds number, so that particles of low thermal diffusivity weakly alter the total heat flux in the suspension at finite particle Reynolds numbers. On the other hand, a higher particle thermal diffusivity significantly increases the total heat transfer.
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Yamada, Jun, Yasuo Kurosaki, and Takanori Nagai. "Radiation Heat Transfer Between Fluidizing Particles and a Heat Transfer Surface in a Fluidized Bed." Journal of Heat Transfer 123, no. 3 (January 8, 2001): 458–65. http://dx.doi.org/10.1115/1.1370503.
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We have investigated the radiation heat transfer occurring in a gas-solid fluidized bed between fluidizing particles and a cooled heat transfer surface. Experimental results reveal that cooled fluidizing particles exist near the surface and suppress the radiation heat transfer between the surface and the higher temperature particles in the depth of the bed. The results also clarify the effects of fluidizing velocity, optical characteristics of particles, and particle diameter on the radiation heat transfer. Based on these results, the authors propose a model for predicting the radiation heat transfer between fluidizing particles and a heat transfer surface.
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Pichler, Mario, Markus Bösenhofer, and Michael Harasek. "Dataset for the Heat-Up and Heat Transfer towards Single Particles and Synthetic Particle Clusters from Particle-Resolved CFD Simulations." Data 7, no. 2 (February 14, 2022): 23. http://dx.doi.org/10.3390/data7020023.
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Heat transfer to particles is a key aspect of thermo-chemical conversion of pulverized fuels. These fuels tend to agglomerate in some areas of turbulent flow and to form particle clusters. Heat transfer and drag of such clusters are significantly different from single-particle approximations commonly used in Euler–Lagrange models. This fact prompted a direct numerical investigation of the heat transfer and drag behavior of synthetic particle clusters consisting of 44 spheres of uniform diameter (60 μm). Particle-resolved computational fluid dynamic simulations were carried out to investigate the heat fluxes, the forces acting upon the particle cluster, and the heat-up times of particle clusters with multiple void fractions (0.477–0.999) and varying relative velocities (0.5–25 m/s). The integral heat fluxes and exact particle positions for each particle in the cluster, integral heat fluxes, and the total acting force, derived from steady-state simulations, are reported for 85 different cases. The heat-up times of individual particles and the particle clusters are provided for six cases (three cluster void fractions and two relative velocities each). Furthermore, the heat-up times of single particles with different commonly used representative particle diameters are presented. Depending on the case, the particle Reynolds number, the cluster void fraction, the Nusselt number, and the cluster drag coefficient are included in the secondary data.
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Tzeng, S. C., Wei Ping Ma, C. H. Liu, Wen Yuh Jywe, and Yung Cheng Wang. "Mechanisms of Heat Transfer in Rotary Shaft of Rotating Machine with Nano-Sized Particles Lubricant." Materials Science Forum 505-507 (January 2006): 31–36. http://dx.doi.org/10.4028/www.scientific.net/msf.505-507.31.
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This study presents an analysis of surfactant added by CuO and Al2O3 nano-sized particles of different percentages. After adding suspending nanocrystalline particles into lubricant of machines, the nano-sized particles will augment the heat transfer characteristics of fluids. Some former studies showed that such liquids pose a great potential for heat transfer enhancement. By applying nanofluids to heat transfer of machine lubricant, this paper attempts to explore dominating factors of heat transfer performance from various weight concentrations of nano-sized particles, the correlation among wall temperature, heat flux, rotational Reynolds number, Nusselt number, Grashof number and rotational Grashof number of four different concentrations. The results show that nano-sized particle lubricant offer a better heat transfer performance than typical lubricants. Since random movement and diffusing effect of nano-sized particles are one crucial factor for an increased heat transfer coefficient, adding 3.5% weight concentration nano-sized particle lubricant will produce an optimum heat transfer performance among Case I~IV.
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Pence, D. V., D. E. Beasley, and R. S. Figliola. "Heat Transfer and Surface Renewal Dynamics in Gas-Fluidized Beds." Journal of Heat Transfer 116, no. 4 (November 1, 1994): 929–37. http://dx.doi.org/10.1115/1.2911468.
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Local instantaneous heat transfer between a submerged horizontal cylinder and a gas-fluidized bed operating in the bubble-flow regime was measured and the resulting signals analyzed. Unique to this investigation is the division of particle convective heat transfer into transient and steady-state contact dynamics through analysis of instantaneous heat transfer signals. Transient particle convection results from stationary particles in contact with the heat transfer surface and yields a heat transfer rate that decays exponentially in time. Steady-state particle convection results from active particle mixing at the heat transfer surface and results in a relatively constant heat transfer rate during emulsion phase contact. The average time of contact for each phase is assessed in this study. Signals were acquired using a constant-temperature platinum film heat flux sensor. Instantaneous heat transfer signals were obtained for various particle sizes by varying the angular position of the heat transfer probe and the fluidization velocity. Individual occurrences of emulsion phase heat transfer that are steady-state in nature are characterized by contact times significantly higher than both the mean transient and mean emulsion phase contact times under the same operating conditions. Transient and steady-state contact times are found to vary with angular position, particle size, and fluidizing velocity. Due to the extremely short transient contact times observed under these fluidization conditions, mean transient heat transfer coefficients are approximately equal to the mean steady-state heat transfer coefficients.
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Wu, Jin Tao, Yu Qiang Dai, Ze Wu Wang, and Feng Xia Liu. "Study on the Heat Transfer in Granular Materials by DEM." Advanced Materials Research 233-235 (May 2011): 2949–54. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.2949.
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The heat transfer in granular materials can be found in many industry processes. But the phenomenon is not well understood. A particle contact heat transfer model (PCHM) was developed by taking each independent mechanism into account. The model combined with DEM was used to simulate heat transfer between particles and inserted heating surface. Comparing with each mechanism, the heat conduction through contact area has the most contribute to apparent effective quantity of heat transfer. The key factors effecting on Qeff include: the number of particles contacting with heating surface, the contact time, and the contact area. When the average diameter is same, the diameter distribution has little effects on heat transfer. While the average diameter is different, the effective heat transfer coefficient decreases with the increasing of particle diameter. The quantity of heat transfer is spatially non-uniform.
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Jacimovski, Darko, Danica Brzic, Radmila Garic-Grulovic, Rada Pjanovic, Mihal Djuris, Zorana Arsenijevic, and Nevenka Boskovic-Vragolovic. "Heat transfer by liquid convection in particulate fluidized beds." Journal of the Serbian Chemical Society, no. 00 (2022): 20. http://dx.doi.org/10.2298/jsc211216020j.
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In this work the theoretical model for heat transfer from a wall to a liquid-solid fluidized bed by liquid convective mechanism has been proposed. The model is based on thickness of boundary layer and film theory. The key parameter in the model is the distance between two adjacent particles which collide with the wall. According to the proposed model, the liquid convective heat transfer in a fluidized bed is 4 to 5 times more intense than in a single-phase flow. Additionally, the wall-to-bed heat transfer coefficient has been measured experimentally in water -glass particles fluidized bed, for different particle sizes. Comparison of the model prediction with experimental data has shown that size of the particles strongly influences the mechanism of heat transfer. For fine particles of 0.8 mm in diameter, the liquid convective heat transfer model represents adequately the experimental data, indicating that particle convective mechanism is negligible. For coarse particles of 1.5 - 2 mm in diameter, the liquid convective heat transfer mechanism accounts for 60 % of the overall heat transfer coefficient.
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Tian, Xing Wang, Yu Zhen Yin, Ping Wang, and Lin Xu. "Numerical Simulation on Flow and Heat Transfer of Power Law Fluid in Structured Packed Porous Media of Particles." Applied Mechanics and Materials 865 (June 2017): 239–46. http://dx.doi.org/10.4028/www.scientific.net/amm.865.239.
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Flow and heat transfer of non-Newtonian fluid in porous media is an universal physical process in nature, industry and agriculture. With a certain concentration of HPAM aqueous solution (a typical power-law type non-Newtonian fluid) as the fluid medium, constructing the porous media skeleton model of orderly arrangement of spherical particles, the flow and heat transfer characteristics in three-dimensional orderly arrangement of porous media have been investigated numerically by using Fluent software. By employing the method of fluid-solid coupling subject to uniform heat flux, the effects of power law fluid rheological index, particle material, particle diameter and porosity on the flow and heat transfer characteristics are analyzed in detail. And also the concept of thermal efficiency is introduced to gain the comprehensive evaluation of its flow and heat transfer characteristics. The results show that the flow resistance decreases with the increase of the power-law index, particle diameter and porosity, and has nothing to do with the thermal conductivity coefficient of particles; while the local convection heat transfer coefficient increases with the increase of the power-law index and the thermal conductivity coefficient of particles, and decreases with the increase of particle diameter and porosity. The results can provide a theoretical basis for the flow and heat transfer mechanism of the power-law type non-Newtonian fluid flowing through the three-dimensional structured packed porous media of particles.
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Malinouski, A. I. "Method for calculation of radiative heat transfer in beds of spherical particles." Doklady of the National Academy of Sciences of Belarus 63, no. 6 (January 7, 2020): 680–88. http://dx.doi.org/10.29235/1561-8323-2019-63-6-680-688.
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A new technique for implementing external (particle-to-wall) and particle-to-particle radiative heat transfer in discrete elements method (DEM) simulations is proposed. It is based on the idea that an expected view factor value depends on relevant local bed parameters (distance between particles, particle radius ratio, and local bed porosity). Calculation of average view factors via the formula requires considerably less computational effort than direct in situ integration, when this happens a reasonable average value and an overall accuracy comparable to direct calculation are provided. Both mono- and polydisperse mixtures of spherical opaque particles were considered. It was shown that using nondimensional parameters, a simple general dependence for an external radiative heat flux may be introduced. Exponential and linear fits were proposed for estimating the particle-particle radiative heat flux. The generalization of the obtained formulas for various bed porosities is proposed. The distribution of cumulative transferred heat flux across the particles up to a certain distance was found, and the recommendations regarding the choice of that parameter to achieve a desired accuracy were formulated. Also, the method to account for the particle emissivity was proposed on the basis of the empirical dependence between emissivity and radiative heat flux in porous materials. The proposed method satisfies all the requirements to become a standard implementation of radiative heat transfer calculation in DEM.
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OTSUKA, Mario, Takeyuki AMI, Miho HAYAMA, Hisashi UMEKAWA, and Mamoru OZAWA. "E310 HEAT TRANSFER CHARACHTERISTICS OF PARTICLE CONVECTION IN FLUIDIZED-BED(Boiler-2)." Proceedings of the International Conference on Power Engineering (ICOPE) 2009.3 (2009): _3–313_—_3–318_. http://dx.doi.org/10.1299/jsmeicope.2009.3._3-313_.
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Chuah, Y. K., and V. P. Carey. "Boiling Heat Transfer in a Shallow Fluidized Particulate Bed." Journal of Heat Transfer 109, no. 1 (February 1, 1987): 196–203. http://dx.doi.org/10.1115/1.3248043.
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Experimental data are presented which indicate the effects of a thin layer of unconfined particles on saturated pool boiling heat transfer from a horizontal surface. Results are presented for two different types of particles: (1) 0.275 and 0.475-mm-dia glass spheres which have low density and thermal conductivity, and (2) 0.100 and 0.200-mm-dia copper spheres which have high density and thermal conductivity. These two particle types are the extremes of particles found as corrosion products or contaminants in boiling systems. To ensure that the surface nucleation characteristics were well defined, polished chrome surfaces with a finite number of artificial nucleation sites were used. Experimental results are reported for heat fluxes between 20 kW/m2 and 100kW/m2 using water at 1 atm as a coolant. For both particle types, vapor was observed to move upward through chimneys in the particle layer, tending to fluidize the layer. Compared with ordinary pool boiling at the same surface heat flux level, the experiments indicate that addition of light, low-conductivity particles significantly increases the wall superheat, whereas addition of heavier, high-conductivity particles decreases wall superheat. Heat transfer coefficients measured in the experiments with a layer of copper particles were found to be as much as a factor of two larger than those measured for ordinary pool boiling at the same heat flux level. The results further indicate that at least for thin layers, the boiling curve is insensitive to layer thickness. These results are shown to be consistent with the expected effects of the particles on nucleation, fluid motion, and effective conductivity in the pool at or near the surface. The effect of surface nucleation site density on heat transfer with a particle layer present is also discussed.
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Mu, Lin, and Hong Chao Yin. "Numerical Simulation of the Influence of Deposits on Heat Transfer Process in a Heat Recovery Steam Generator." Applied Mechanics and Materials 121-126 (October 2011): 1301–5. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.1301.
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Flue gas entrains a large number of ash particles which are composed of alkali substances into the heat recovery steam generator (HRSG). The deposition of particles on the tube surface of heat transfer can reduce the heat transfer efficiency significantly. In the present work, an Eulerian- Lagrangian model based on Computational Fluid Dynamics (CFD) is implemented to simulation flue gas turbulent flow, heat transfer and the particle transport in the HRSG. Several User-Defined Functions (UDFs) are developed to predict the particle deposition/ rebounding as well as the influence of physical properties and microstructure of deposits on the heat transfer process. The results show that only after one day deposition, the total heat transfer rate reduces 27.68% compared with the case no deposition. Furthermore, the total heat transfer rate reduces to only 238.74kW after 30 days of continuous operation without any slag removal manipulation. Both numerical simulation and field measurement identify that the deposits play an important role in the heat transfer in the HRSG. Especially, when the deposits can’t be removed designedly according to the actual operating conditions, the HRSG experiences a noticeable decline in heat transfer efficiency due to continuous fouling and slagging on the tube surface.
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Bahiraei, Mehdi, Seyed Mostafa Hosseinalipour, and Morteza Hangi. "Prediction of convective heat transfer of Al2O3-water nanofluid considering particle migration using neural network." Engineering Computations 31, no. 5 (July 1, 2014): 843–63. http://dx.doi.org/10.1108/ec-12-2012-0311.
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Purpose – The purpose of this paper is to attempt to investigate the particle migration effects on nanofluid heat transfer considering Brownian and thermophoretic forces. It also tries to develop a model for prediction of the convective heat transfer coefficient. Design/methodology/approach – A modified form of the single-phase approach was used in which an equation for mass conservation of particles, proposed by Buongiorno, has been added to the other conservation equations. Due to the importance of temperature in particle migration, temperature-dependent properties were applied. In addition, neural network was used to predict the convective heat transfer coefficient. Findings – At greater volume fractions, the effect of wall heat flux change was more significant on nanofluid heat transfer coefficient, whereas this effect decreased at higher Reynolds numbers. The average convective heat transfer coefficient raised by increasing the Reynolds number and volume fraction. Considering the particle migration effects, higher heat transfer coefficient was obtained and also the concentration at the tube center was higher in comparison with the wall vicinity. Furthermore, the proposed neural network model predicted the heat transfer coefficient with great accuracy. Originality/value – A review of the literature shows that in the single-phase approach, uniform concentration distribution has been used and the effects of particle migration have not been considered. In this study, nanofluid heat transfer was simulated by adding an equation to the conservation equations to consider particle migration. The effects of Brownian and thermophoretic forces have been considered in the energy equation. Moreover, a model is proposed for prediction of convective heat transfer coefficient.
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Wu, C. C., and G. J. Hwang. "Flow and Heat Transfer Characteristics Inside Packed and Fluidized Beds." Journal of Heat Transfer 120, no. 3 (August 1, 1998): 667–73. http://dx.doi.org/10.1115/1.2824335.
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This paper investigates experimentally and theoretically the flow and heat transfer characteristics inside packed and fluidized beds. A single-blow transient technique combined with a thermal nonequilibrium two-equation model determined the heat transfer performances. Spherical particles were randomly packed in the test section for simulating the packed beds with porosity ε=0.38 and 0.39. Particles were strung with different spaces for fluidized beds with ε = 0.48 ~ 0.97. The ranges of dominant parameters are the Prandtl number Pr = 0.71, the particle Reynolds number Red = 200 ~ 7000, and ε = 0.38 ~ 0.97. The results show that the heat transfer coefficient increases with the decrease in the porosity and the increase in the particle Reynolds number. The friction coefficients of the fluidized beds with ε = 0.48 and 0.53 have significant deviations from that of the packed bed with ε = 0.38 and 0.39. Due to fewer interactions among particles for ε = 0.97, the friction coefficient approaches the value of a single particle.
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Delvosalle, C., and J. Vanderschuren. "Gas-to-particle and particle-to-particle heat transfer in fluidized beds of large particles." Chemical Engineering Science 40, no. 5 (1985): 769–79. http://dx.doi.org/10.1016/0009-2509(85)85030-2.
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Bielas, Rafał, and Arkadiusz Józefczak. "The Effect of Particle Shell on Cooling Rates in Oil-in-Oil Magnetic Pickering Emulsions." Materials 13, no. 21 (October 26, 2020): 4783. http://dx.doi.org/10.3390/ma13214783.
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Pickering emulsions (particle-stabilized emulsions) are usually considered because of their unique properties compared to surfactant-stabilized emulsions including better stability against emulsion aging. However, the interesting feature of particle-stabilized emulsions could be revealed during their magnetic heating. When magnetic particles constitute a shell around droplets and the sample is placed in an alternating magnetic field, a temperature increase appears due to energy dissipation from magnetic relaxation and hysteresis within magnetic particles. We hypothesize that the solidity of the magnetic particle shell around droplets can influence the process of heat transfer from inside the droplet to the surrounding medium. In this way, particle-stabilized emulsions can be considered as materials with changeable heat transfer. We investigated macroscopically heating and cooling of oil-in-oil magnetic Pickering emulsions with merely packed particle layers and these with a stable particle shell. The change in stability of the shell was obtained here by using the coalescence of droplets under the electric field. The results from calorimetric measurements show that the presence of a stable particle shell caused a slower temperature decrease in samples, especially for lower intensities of the magnetic field. The retarded heat transfer from magnetic Pickering droplets can be utilized in further potential applications where delayed heat transfer is desirable.
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Sun, Ya Wei, Yi Cheng, Liang He, and Rui Li. "Heat Transfer Model of Larch Bark Particles Pyrolysis." Advanced Materials Research 1096 (April 2015): 232–36. http://dx.doi.org/10.4028/www.scientific.net/amr.1096.232.
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A novel model for larch bark pyrolysis was established by combine dimensions, shapes, boundary conditions, pyrolysis gas diffusion, particle size and reaction heat expression. It overcomes the shortages of early models which are short of expression of the reaction heat and application conditions. By introducing the kinetic equations and shape factor, the model was simulated by commercial software. The simulation results indicated that the pyrolysis time of particles is increasing by particle size, the best size for larch pyrolysis is 0.8 mm under 775K.
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Chen, Huajun, Yitung Chen, Hsuan-Tsung Hsieh, and Nathan Siegel. "Computational Fluid Dynamics Modeling of Gas-Particle Flow Within a Solid-Particle Solar Receiver." Journal of Solar Energy Engineering 129, no. 2 (August 25, 2006): 160–70. http://dx.doi.org/10.1115/1.2716418.
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A detailed three-dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid-particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two-band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray-tracing algorithm. Two kinds of solid-particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the gas velocity, temperature, particle solid volume fraction, particle outlet temperature, and cavity efficiency.
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Tung, V. X., and V. K. Dhir. "Experimental Study of Boiling Heat Transfer From a Sphere Embedded in a Liquid-Saturated Porous Medium." Journal of Heat Transfer 112, no. 3 (August 1, 1990): 736–43. http://dx.doi.org/10.1115/1.2910448.
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Boiling heat transfer from a sphere embedded in a porous medium composed of nonheated glass particles was studied under steady-state and transient quenching conditions. In the experiments, the diameter of the nonheated glass particles forming the porous layers was varied parametrically. Freon-113 was used as the test liquid. Experimental results showed that the maximum heat flux increased monotonically with increasing glass particle diameter and approached an asymptotic value corresponding to the maximum heat flux obtained in a pool free of glass particles. It was also observed that the minimum heat flux was nearly insensitive to the particle size and the film boiling heat transfer coefficient increased slightly with decreasing particle size. In the nucleate boiling region, the heat transfer coefficient showed a much weaker dependence on wall superheat in the presence of particles. Transient data indicated that the surface temperature was not uniform during quenching. Therefore, different maximum heat fluxes were obtained depending on the location of the thermocouple whose temperature history was employed in recovering the transient boiling curve. However, for some applications, cooling rates predicted by imposing the steady-state boiling curve may not be in large error.
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Zhang, Shao Bo. "Experimental Investigation of Convective Heat Transfer in Circulating Water System." Advanced Materials Research 457-458 (January 2012): 439–44. http://dx.doi.org/10.4028/www.scientific.net/amr.457-458.439.
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The laminar convective heat transfer behavior of CuO nanoparticle dispersions in water with three different particle sizes (23 nm, 51 nm, and 76 nm) is investigated experimentally in a flow loop with constant heat flux. The main purpose of this study is to evaluate the effect of particle size on convective heat transfer in laminar region. The experimental results show that the suspended nanoparticles remarkably increase the convective heat transfer coefficient of the base fluid, and the nanofluid with 23nm particles shows higher heat transfer coefficient than nanofluids containing the other two particle sizes about 10% under the same Re. Based on the effective medium approximation and the fractal theory, the effective thermal conductivity of suspension is obtained. It is shown that if the new effective thermal conductivity correlation of the nanofluids is used in calculating the Prandtl and Nusselt numbers, the new correlation accurately reproduces the convective heat transfer behavior in tubes.
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Diao, Kai Kan, Xian Ke Lu, Zhi Ning Wu, and Yu Yuan Zhao. "Heat Transfer Performance of LCS Porous Copper with Different Structural Characteristics." Materials Science Forum 933 (October 2018): 380–87. http://dx.doi.org/10.4028/www.scientific.net/msf.933.380.
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Porous metals are highly efficient media for active cooling and thermal management. However, the working fluid requires high pumping power to flow through the porous metals. This paper investigated the effect of structural characteristics (porosity, pore size and Cu particle size) on the heat transfer performance of porous Cu manufactured by Lost Carbonate Sintering (LCS). The heat transfer coefficient and pressure drop of porous Cu samples with porosity from 0.48 to 0.78, pore size from 250-1500 μm and Cu particle size from 75 to 841 μm were measured under the one-dimensional forced convection condition using water. For all the samples with different pore sizes and Cu particle sizes, the optimum heat transfer coefficient was observed at a porosity between 0.6 and 0.7 and the pressure drop decreased with increasing porosity. The effect of pore size on heat transfer coefficient was not pronounced while pressure drop decreased with decreasing pore size. Samples with large Cu particles (841 μm) had higher optimum heat transfer coefficients and lower pressure drops. The coefficient of performance (CoP), which can be used to describe the overall heat transfer performance, increased with increasing porosity, decreasing pore size and increasing Cu particle size.
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Nasr, K., S. Ramadhyani, and R. Viskanta. "An Experimental Investigation on Forced Convection Heat Transfer From a Cylinder Embedded in a Packed Bed." Journal of Heat Transfer 116, no. 1 (February 1, 1994): 73–80. http://dx.doi.org/10.1115/1.2910886.
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Forced convection heat transfer from a cylinder embedded in a packed bed of spherical particles was studied experimentally. With air as the working fluid, the effects of particle diameter and particle thermal conductivity were examined for a wide range of thermal conductivities (from 200 W/m K for aluminum to 0.23 W/m K for nylon) and three nominal particle sizes (3 mm, 6 mm, and 13 mm). In the presence of particles, the measured convective heat transfer coefficient was up to seven times higher than that for a bare tube in crossflow. It was found that higher heat transfer coefficients were obtained with smaller particles and higher thermal conductivity packing materials. The experimental data were compared against the predictions of a theory based on Darcy’s law and the boundary layer approximations. While the theoretical equation was moderately successful at predicting the data, improved correlating equations were developed by modifying the form of the theoretical equation to account better for particle diameter and conductivity variations.
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Azimi, Seyyed Shahabeddin, Mansour Kalbasi, and Mohammad Hosain Namazi. "Effect of nanoparticle diameter on the forced convective heat transfer of nanofluid (water + Al2O3) in the fully developed laminar region." International Journal of Modeling, Simulation, and Scientific Computing 05, no. 03 (May 5, 2014): 1450008. http://dx.doi.org/10.1142/s1793962314500081.
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Nanofluid is a suspension of nanoparticles (solid particles with diameters below 100 nm) in a conventional base fluid with significantly improved heat transfer characteristics compared to the original fluid. The heat transfer coefficient is a quantitative characteristic of the convective heat transfer. The purpose of this paper is to study the effect of the nanoparticle size (diameter) on the heat transfer coefficient of forced convective heat transfer of nanofluid in the fully developed laminar region of a horizontal tube. Using thermal conductivity model which is a function of the nanoparticle size, flow of a nanofluid (water + Al 2 O 3) in a circular tube submitted to a constant wall temperature is numerically investigated with two particle sizes of 11 nm and 47 nm. The calculated results show that the nanoparticle size does not significantly affect the heat transfer coefficient, however, the heat transfer coefficient decreases as the particle size increases.
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Alammari, Sumaia Bugumaa Abubaker, and Muhammad Abbas Ahmad Zaini. "Nanofluids in Zigzag Elliptical Tube Heat Exchanger: A Design Perspective." Acta Universitatis Sapientiae, Electrical and Mechanical Engineering 14, no. 1 (December 1, 2022): 13–27. http://dx.doi.org/10.2478/auseme-2022-0002.
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Abstract Nanofluids contain nanometer-sized particles in suspension to enhance heat transfer by increasing the thermal conductivity. This paper provides an overview of particle size and volume fraction of nanofluids, and their roles in enhancing the heat transfer. Often, the transfer of heat is enhanced by dispersed particles with small diameter and high concentration despite some debate about the governing effects. The design of elliptical cross-section and zigzag tube also sheds insight into augmenting heat transfer for future research directions and applications.
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Zhevzhyk, Oleksandr, Leonid Kholiavchenko, Serhii Davydov, Iryna Potapchuk, Liudmyla Kabakova, Olena Gupalo, Vitalii Pertsevyi, and Nataliia Morozova. "Mathematical modeling of heating of coal particle within the space between electrodes of arc-heating reactor." E3S Web of Conferences 168 (2020): 00069. http://dx.doi.org/10.1051/e3sconf/202016800069.
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A mathematical model of heating of coal particles that move in the initial section of a submerged gas jet within the space between electrodes of reaction chamber of arc-heating reactor is created. The model takes into account convective heat transfer and heat transfer by radiation from a sphere (particle) – circle (anode) system. The temperatures of particles on mechanical trajectory are obtained depending on particle diameters and the initial coordinate of nozzle leaving.
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Schmidt, Robin, and Petr A. Nikrityuk. "Direct numerical simulation of particulate flows with heat transfer in a rotating cylindrical cavity." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, no. 1945 (June 28, 2011): 2574–83. http://dx.doi.org/10.1098/rsta.2011.0046.
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The purpose of this work was the direct numerical simulation of heat and fluid flow by granular mixing in a horizontal rotating kiln. To model particle behaviour and the heat and fluid flow in the drum, we solve the mass conservation, momentum and energy conservation equations directly on a fixed Eulerian grid for the whole domain including particles. At the same time the particle dynamics and their collisions are solved on a Lagrangian grid for each particle. To calculate the heat transfer inside the particles we use two models: the first is the direct solution of the energy conservation equation in the Lagrangian and Eulerian space, and the second is our so-called linear model that assumes homogeneous distribution of the temperature inside each particle. Numerical simulations showed that, if the thermal diffusivity of the gas phase significantly exceeds the same parameter of the particles, the linear model overpredicts the heating rate of the particles. The influence of the particle size and the angular velocity of the drum on the heating rates of particles is studied and discussed.
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Majeed, Noor Sabeeh, Shaymaa Mahdi Salih, Hussam Nadum Abda Lraheemal Ani, Basma Abbas Abdulmajeed, Paul Constantin Albu, and Gheorghe Nechifor. "Study the Effect of SiO2 Nanofluids on Heat Transfer in Double Pipe Heat Exchanger." Revista de Chimie 71, no. 5 (May 29, 2020): 117–24. http://dx.doi.org/10.37358/rc.20.5.8119.
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In this paper the effect of nanofluid is studied in the double pipe heat exchanger counter current flow, the viscosity of nanofluids are measured at different temperatures and different particle sizes. SiO2 nanoparticles are dispersed at different concentrations (0.2-2) % with different particle sizes of (50-25) nm in base fluid of water. The friction factor and heat transfer coefficient are calculated at different nanoparticle sizes, the results showed that the viscosity was increased as nanoparticle concentration increased. The friction factor is increased as SiO2 nanoparticles concentration and increased as nanoparticles size decreased. The heat transfer coefficient increased as nanoparticle concentration increased and particles size decrease.
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Jayaprakash Mishra and Tumbanath Samantara. "Study of Unsteady Two Phase Flow over An Inclined Permeable Stretching Sheet with Effects of Electrification and Radiation." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 97, no. 2 (August 31, 2022): 26–38. http://dx.doi.org/10.37934/arfmts.97.2.2638.
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An analysis on flow and heat transfer with in a two-dimensional unsteady radiative boundary layer with fluid-particle interaction has been studied. The flow is occurred due to the suddenly linear movement of an inclined permeable stretching sheet. The flow is considered in a neutral medium where no external electric or magnetic field is supplied. But due to the random motion of particles leads to interaction between fluid-particle, particle-particle and particle-wall, a tribo-electric effect occurs. As a result, both the fluid as well as particles are electrified which creates a major impact on flow field. Hence, a balanced mathematical model has been formulated considering both electrification and radiation parameter on both the phases. Using similarity transformation, the governing equations are transferred to ODEs and solved by built in solver Bvp4c of MATLAB. The impacts of various parameters on the flow field have been discussed and determined the heat transfer characteristics. The stronger electric filed significantly enhances the temperature of both fluid and particle phase, which occurs more heat transfer on the surface.
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Jog, M. A., and L. Huang. "Transient Heating and Melting of Particles in Plasma Spray Coating Process." Journal of Heat Transfer 118, no. 2 (May 1, 1996): 471–77. http://dx.doi.org/10.1115/1.2825868.
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In the plasma spray coating process, solid particles are injected into a plasma jet. The heat transfer from the plasma to the particles results in heating and melting of the particles. The molten particles impact on a surface forming a thin coat. In this paper, we investigate the heating and melting of a spherical particle injected into a thermal plasma. The transient temperature distribution in the particle interior is obtained simultaneously with the temperature and number density variations of the ions, electrons, and the neutrals as well as the electric potential variation in the plasma. Our analysis incorporates a model for the production and recombination of electrons and ions. The transport in the plasma is modeled by considering the main body of the plasma as charge neutral and a charge sheath in the vicinity of the particle surface. The heat flux to the particle is evaluated by taking into account all modes of heat transfer to the surface. The temporal variations of the particle temperature distribution are calculated. Results are compared with the available predictions made without taking into account the gas ionization to assess the importance of ionization and particle charging on the heat transport to the particle. For argon, for the particle materials considered in this study, the effect of gas ionization on the heat transport was found to be negligible for plasma temperatures below 6500 K.
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Joulin, Clément, Jiansheng Xiang, John-Paul Latham, Christopher Pain, and Pablo Salinas. "Capturing heat transfer for complex-shaped multibody contact problems, a new FDEM approach." Computational Particle Mechanics 7, no. 5 (February 22, 2020): 919–34. http://dx.doi.org/10.1007/s40571-020-00321-w.
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Abstract This paper presents a new approach for the modelling of heat transfer in 3D discrete particle systems. Using a combined finite–discrete element (FDEM) method, the surface of contact is numerically computed when two discrete meshes of two solids experience a small overlap. Incoming heat flux and heat conduction inside and between solid bodies are linked. In traditional FEM (finite element method) or DEM (discrete element method) approaches, to model heat transfer across contacting bodies, the surface of contact is not directly reconstructed. The approach adopted here uses the number of surface elements from the penetrating boundary meshes to form a polygon of the intersection, resulting in a significant decrease in the mesh dependency of the method. Moreover, this new method is suitable for any sizes or shapes making up the particle system, and heat distribution across particles is an inherent feature of the model. This FDEM approach is validated against two models: a FEM model and a DEM pipe network model. In addition, a multi-particle heat transfer contact problem of complex-shaped particles is presented.
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Shekhovtsov, Valentin, Oleg Volokitin, Gennady Volokitin, and Nelly Skripnikova. "Heat and Mass Transfer in Porous Particle in Thermal Plasma Flow." Key Engineering Materials 839 (April 2020): 178–83. http://dx.doi.org/10.4028/www.scientific.net/kem.839.178.
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The paper presents research into heat and mass transfer in agglomerated particles exposed to the thermal plasma flow. The dynamic motion, heating and melting are considered for agglomerated particles. It is shown that the surface temperature of porous particles rather rapidly reaches the value of Tsur>Tmelt starting from the area of their introduction into the plasma flow. This effect is determined by the low conductivity of porous particles and indicates to a great temperature difference between the particle surface and its nucleus. It is shown that hollow particles can be obtained from silica sand treated by thermal plasma at 6700 K and 515 m/s velocity. The particle surface displays no clear defects. According to the analysis of X-ray diffraction patterns, the obtained hollow particles have no diffraction peaks.
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Persson, B. N. J., and J. Biele. "Heat transfer in granular media with weakly interacting particles." AIP Advances 12, no. 10 (October 1, 2022): 105307. http://dx.doi.org/10.1063/5.0108811.
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We study the heat transfer in weakly interacting particle systems in vacuum. The particles have surface roughness with self-affine fractal properties, as expected for mineral particles produced by fracture, e.g., by crunching brittle materials in a mortar, or from thermal fatigue or the impact of micrometeorites on asteroids. We show that the propagating electromagnetic (EM) waves give the dominant heat transfer for large particles, while for small particles both the evanescent EM-waves and the phononic contribution from the area of real contact are important. As an application, we discuss the heat transfer in rubble pile asteroids.
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Sangulova, I. B., V. P. Selyaev, E. I. Kuldeev, R. E. Nurlybaev, and Ye S. Orynbekov. "Assessment of the influence of the structural characteristics of granular systems of microsilicon on the properties of thermal insulation materials." Kompleksnoe ispolʹzovanie mineralʹnogo syrʹâ/Complex Use of Mineral Resources/Mineraldik shikisattardy Keshendi Paidalanu 320, no. 1 (January 5, 2022): 5–14. http://dx.doi.org/10.31643/2022/6445.01.
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The article discusses experimental studies of the size and shape of structured particles of microsilica small angle x-ray scattering method and a photophonon theoretical description of the heat transfer process in complex heterogeneous structures to assessment of the structural characteristics of granular systems for the properties of thermal insulating materials. The mechanism of heat transfer in granular, porous systems is quite complex, since heat exchange occurs in a material consisting of two phases (solid and gas) and at the phase boundary. Heat transfer in liquid thermal insulation coatings can be carried out from one solid particle to another. In this case, the thermal conductivity will depend on: the chemical and elemental composition of the material; particle granulometry; surface topology - the presence of inhomogeneities, defects on the surface; the number of touches and the contact area between the particles. The heat transfer of gas in the pores is carried out when gas molecules collide. Thermal conductivity will be determined by the ratio of the free path of molecules and linear pore sizes, temperature and dynamic viscosity of the gas phase, the nature of the interaction of gas molecules with the solid phase. Heat transfer by radiation depends on the nature of the particles, the dielectric, magnetic permeability and the degree of blackness of the particle surface. Based on the analysis of possible mechanisms of heat transfer in granular systems, it can be argued that the effective thermal conductivity of the system depends, all other things being equal, on the structure of the pore space of granular materials, topology and the number of particle touches. Considering idealized models of the structure of granular materials in the form of ordered folds of perfectly smooth balls, we can obtain several variants of structures: with tetrahedral; hexagonal; cubic packing of balls.
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Walter, Lindsay P., and Mathieu Francoeur. "Orientation effects on near-field radiative heat transfer between complex-shaped dielectric particles." Applied Physics Letters 121, no. 18 (October 31, 2022): 182206. http://dx.doi.org/10.1063/5.0116828.
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The effect of orientation on near-field radiative heat transfer between two complex-shaped superellipsoid particles of SiO2 is presented. The particles under study are 50 nm in radius and of variable concavity. Orientation is characterized by the degree of rotational symmetry in the two-particle systems, and the radiative conductance is calculated using the discrete system Green's function approach to account for all electromagnetic interactions. The results reveal that the total conductance in some orientations can be up to twice that of other orientations when particles are at a center-of-mass separation distance of 110 nm. Orientation effects are not significantly correlated with system rotational symmetries but are strongly correlated with the minimum vacuum gap distance between particles. As such, orientation effects on near-field radiative heat transfer are a consequence of particle topology, with more extreme topologies leading to a continuation of orientation effects at larger particle center-of-mass separation distances. The concave superellipsoid particles display significant orientation effects up to a center-of-mass separation distance approximately equal to 3.9 times the particle radius, while the convex superellipsoid particles display significant orientation effects up to a center-of-mass separation distance approximately equal to 3.2 times the particle radius. In contrast to previous anisotropic, spheroidal dipole studies, these results of complex-shaped superellipsoid particles suggest that orientation effects become negligible when heat transfer is a volumetric process for all orientations. This work is essential for understanding radiative transport between particles that have non-regular geometries or that may have geometrical defects or abnormalities.
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Uvarova, Lyudmila A., Irina V. Krivenko, Marina A. Smirnova, and Alexey B. Nadykto. "Electromagnetic Radiation and Heat Transfer in Disperse Systems Consisting of Spherical and Cylindrical Particles." EPJ Web of Conferences 224 (2019): 02008. http://dx.doi.org/10.1051/epjconf/201922402008.
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The article deals with the electromagnetic radiation transfer in systems of spherical disperse particles with different optical characteristics. A model of the electromagnetic radiation transfer in cylindrical particles containing a small volume of different chemical substance is developed. The substance differs substantially from that of the particle in a radiation absorption coefficient for the wavelength under study in the long wave approximation. The finite element method is used to calculate the temperature field for the system of spherical particles in a two-dimensional approximation. The configurations of particle packing is chosen on a random basis, which significantly complicated the calculations, the longitudinal and transverse diameters of particle clusters, the distance between centers of two largest particles, and similar natural geometric properties have been considered as characteristic system dimensions.The possibility of controlling heat transfer in such systems is studied. It follows from our model calculations that both electromagnetic and thermal interaction of dispersed particles can be noticeable at large distances between their centers; that near the boundary of the dispersed particle there is a thermal surface layer of the particle, where the temperature distribution is essentially heterogeneous. It is concluded that the thermal mechanism of destruction of a weakly absorbing particle due to a strong increase in temperature because of electromagnetic resonance in a neighboring particle with a strong absorption. It is established that the effect of collective influences in polydisperse system can change temperature by more than 1,5 times.
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Fu, Jianhong, Sheng Chen, and Xiaochen Zhou. "Effect of heterogeneity on interphase heat transfer for gas–solid flow: A particle-resolved direct numerical simulation." Physics of Fluids 34, no. 12 (December 2022): 123317. http://dx.doi.org/10.1063/5.0130850.
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Particle-resolved direct numerical simulation (PR-DNS) of flow past a particle cluster is conducted to analyze the influence of heterogeneous particle distribution on the gas–solid heat transfer calculation. Then, the heat transfer rates calculated using Gunn's correlation are systematically compared with the DNS results for virtual computational fluid dynamics-discrete element method (CFD-DEM) grids with different levels of heterogeneity. The results show that, for a grid located at the interface between the dense cluster region and dilute region, Gunn's correlation significantly overestimates the heat transfer rate, especially at small Reynolds numbers. This is caused by the large temperature difference between the dense and dilute regions in the heterogeneous CFD-DEM grid. The value calculated by Gunn's correlation can be up to ten times the DNS result. For a homogeneous grid inside a dense region, the conventional Nusselt correlation fails to capture the rapid increase in the fluid temperature gradient around the near-interface particles when the grid approaches the cluster–fluid interface. Furthermore, even if the size of the CFD-DEM grid is reduced to twice the particle diameter, the heterogeneous particle distribution still leads to a remarkable error in the heat transfer calculation. Finally, modifications to Gunn's correlation are proposed for three typical cross-interface cases, which can well reflect the influence of the heterogeneous distribution of particles and yield a heat transfer rate close to the PR-DNS results. The mean relative deviations of the three fitted correlations are 5.8%, 14.3%, and 22.4%, respectively.
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Zandi Pour, Hamid Reza, and Michele Iovieno. "Heat Transfer in a Non-Isothermal Collisionless Turbulent Particle-Laden Flow." Fluids 7, no. 11 (November 7, 2022): 345. http://dx.doi.org/10.3390/fluids7110345.
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To better understand the role of particle inertia on the heat transfer in the presence of a thermal inhomogeneity, Eulerian–Lagrangian direct numerical simulations (DNSs) have been carried out by using the point–particle model. By considering particles transported by a homogeneous and isotropic, statistically steady turbulent velocity field with a Taylor microscale Reynolds number from 37 to 124, we have investigated the role of particle inertia and thermal inertia in one- and two-way coupling collisionless regimes on the heat transfer between two regions at uniform temperature. A wide range of Stokes numbers, from 0.1 to 3 with a thermal Stokes-number-to-Stokes-number ratio equal to 0.5 to 4.43 has been simulated. It has been found that all moments always undergo a self-similar evolution in the interfacial region between the two uniform temperature zones, the thickness of which shows diffusive growth. We have determined that the maximum contribution of particles to the heat flux, relative to the convective heat transfer, is achieved at a Stokes number which increases with the ratio between thermal Stokes and Stokes number, approaching 1 for very large ratios. Furthermore, the maximum increases with the thermal Stokes-to-Stokes number ratio whereas it reduces for increasing Reynolds. In the two-way coupling regime, particle feedback tends to smooth temperature gradients by reducing the convective heat flux and to increase the particle turbulent heat flux, in particular at a high Stokes number. The impact of particle inertia reduces at very large Stokes numbers and at larger Reynolds numbers. The dependence of the Nusselt number on the relevant governing parameters is presented. The implications of these findings for turbulence modelling are also briefly discussed.
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Supramono, Dijan, Adithya Fernando Sitorus, and Mohammad Nasikin. "Synergistic Effect on the Non-Oxygenated Fraction of Bio-Oil in Thermal Co-Pyrolysis of Biomass and Polypropylene at Low Heating Rate." Processes 8, no. 1 (January 2, 2020): 57. http://dx.doi.org/10.3390/pr8010057.
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Biomass pyrolysis and polypropylene (PP) pyrolysis in a stirred tank reactor exhibited different heat transfer phenomena whereby heat transfer in biomass pyrolysis was driven predominantly by heat radiation and PP pyrolysis by heat convection. Therefore, co-pyrolysis could exhibit be expected to display various heat transfer phenomena depending on the feed composition. The objective of the present work was to determine how heat transfer, which was affected by feed composition, affected the yield and composition of the non-polar fraction. Analysis of heat transfer phenomena was based on the existence of two regimes in the previous research in which in regime 1 (the range of PP composition in the feeds is 0–40%), mass ejection from biomass particles occurred without biomass particle swelling, while in regime 2 (the range of PP composition in the feeds is 40–100%), mass ejection was preceded by biomass particle swelling. The co-pyrolysis was carried out in a stirred tank reactor with heating rate of 5 °C/min until 500 °C and using N2 gas as carrier gas. Temperature measurement was applied to pyrolysis fluid at the lower part of the reactor and small biomass spheres of 6 mm diameter to simulate heat transfer to biomass particles. The results indicate that in regime 1 convective and radiative heat transfers sparingly occurred and synergistic effect on the yield of non-oxygenated phase increased with increasing convective heat transfer at increasing %PP in feed. On the other hand, in regime 2, convective heat transfer was predominant with decreasing synergistic effect at increasing %PP in feed. The optimum PP composition in feed to reach maximum synergistic effect was 50%. Non-oxygenated phase portion in the reactor leading to the wax formation acted as donor of methyl and hydrogen radicals in the removal of oxygen to improve synergistic effect. Non-oxygenated fraction of bio-oil contained mostly methyl comprising about 53% by mole fraction, while commercial diesel contained mostly methylene comprising about 59% by mole fraction
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Evans, G., W. Houf, R. Greif, and C. Crowe. "Gas-Particle Flow Within a High Temperature Solar Cavity Receiver Including Radiation Heat Transfer." Journal of Solar Energy Engineering 109, no. 2 (May 1, 1987): 134–42. http://dx.doi.org/10.1115/1.3268190.
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A study has been made of the flow of air and particles and the heat transfer inside a solar heated, open cavity containing a falling cloud of 100-1000 micron solid particles. Two-way momentum and thermal coupling between the particles and the air are included in the analysis along with the effects of radiative transport within the particle cloud, among the cavity surfaces, and between the cloud and the surfaces. The flow field is assumed to be two-dimensional with steady mean quantities. The PSI-Cell (particle source in cell) computer code is used to describe the gas-particle interaction. The method of discrete ordinates is used to obtain the radiative transfer within the cloud. The results include the velocity and temperature profiles of the particles and the air. In addition, the thermal performance of the solid particle solar receiver has been determined as a function of particle size, mass flow rate, and infrared scattering albedo. A forced flow, applied across the cavity aperture, has also been investigated as a means of decreasing convective heat loss from the cavity.
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Lee, Y. C., Y. P. Chyou, and E. Pfender. "Particle dynamics and particle heat and mass transfer in thermal plasmas. Part II. Particle heat and mass transfer in thermal plasmas." Plasma Chemistry and Plasma Processing 5, no. 4 (December 1985): 391–414. http://dx.doi.org/10.1007/bf00566011.
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Xu, Yu Peng, Li Jie Cui, Xin Xin Ren, Wei Ge, and Wei Gang Lin. "DEM Simulations on the Heat Conduction in a Particle Mixer." Advanced Materials Research 549 (July 2012): 908–13. http://dx.doi.org/10.4028/www.scientific.net/amr.549.908.
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Understanding the heat transfer among particles with uneven temperature distribution is a key to powder processing. In this work, the discrete element method (DEM) is used to optimize the interior structure of a particle mixer with multiple baffles to achieve better heat transfer between two particulate materials. The simulation results show that optimal values exist for the number of baffles and their widths, slope angles and spacing to enhance heat transfer. The results are helpful to the design of a variety of process such as the ultra-fast pyrolysis in “coal topping”.
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Gao, Wei Min, Ling Xue Kong, F. H. She, and Peter D. Hodgson. "Particle Dynamics and Heat Transfer at Workpiece Surface in Heat Treatment Fluidised Beds." Advanced Materials Research 264-265 (June 2011): 1456–61. http://dx.doi.org/10.4028/www.scientific.net/amr.264-265.1456.
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The particle behaviour in a heat treatment fluidised bed was studied by the analysis of particle images taken with a high speed CCD digital video camera. The comparison of particle dynamics was performed for the fluidised beds without part, with single part and with multi-parts. The results show that there are significant differences in particle behaviours both in different beds and at different locations of part surfaces. The total and radiative heat transfer coefficients at different surfaces of a metallic part in a fluidised bed were measured by a heat transfer probe developed in the present work. The structure of the probe was optimized with numerical simulation of energy conservation for measuring the heat transfer coefficient of 150-600 W/m2K. The relationship between the particle dynamics and the heat transfer was analysed to form the basis for future more rational designs of fluidised beds as well as for improved quality control.
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Phuoc, T. X., and K. Annamalai. "A Heat and Mass Transfer Analysis of the Ignition and Extinction of Solid Char Particles." Journal of Heat Transfer 121, no. 4 (November 1, 1999): 886–93. http://dx.doi.org/10.1115/1.2826079.
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The present work studies the ignition and extinction of a spherical solid fuel particle exposed to a quiescent, hot, oxygen-containing environment. Using particle sizes and ambient temperature and oxygen concentration as parameters, the ignition, burning, and extinction of particles were parametrically analyzed by studying the relative heat production and heat-loss rates. For a given ambient condition, the results showed that it is possible that both large and small particles might not ignite at all. When a particle burns, its size decreases with time and its combustion characteristics are altered. The extinction condition may be reached due solely to the diminishing size of the particle. The particle extinction diameter was calculated. It strongly depends on the ambient condition and the reaction rate, but not on the initial particle size.
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Bu, Chang-sheng, Dao-yin Liu, Xiao-ping Chen, Cai Liang, Yu-feng Duan, and Lun-bo Duan. "Modeling and Coupling Particle Scale Heat Transfer with DEM through Heat Transfer Mechanisms." Numerical Heat Transfer, Part A: Applications 64, no. 1 (July 2013): 56–71. http://dx.doi.org/10.1080/10407782.2013.772864.
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