The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
G P Beretta - One of the best experts on this subject based on the ideXlab platform.
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Evidence of Convective heat transfer enhancement induced by spinodal decomposition.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: P Poesio, A M Lezzi, G P BerettaAbstract:Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the Péclet number, defined as the ratio between Convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the Péclet number is small - i.e., when viscosity and diffusivity are large - or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong Convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a 1-mm -thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of Convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but Effectively Convective Effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface H model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.
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Evidence of Convective heat transfer enhancement induced by spinodal decomposition.
Physical Review E, 2007Co-Authors: P Poesio, A M Lezzi, G P BerettaAbstract:Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the P\'eclet number, defined as the ratio between Convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the P\'eclet number is small---i.e., when viscosity and diffusivity are large---or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong Convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a $1\text{\ensuremath{-}}\mathrm{mm}$-thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of Convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but Effectively Convective Effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface $H$ model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.
Jiuzhou Zhao - One of the best experts on this subject based on the ideXlab platform.
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Solidification of Immiscible Alloys and Convective Effect
Materials Science Forum, 2014Co-Authors: Jiuzhou Zhao, Hong Xiang JiangAbstract:A model describing the microstructure formation in a directionally solidified immiscible alloy under the Convective Effect is presented. The microstructure evolution in a directionally solidified Al-Pb alloy is investigated. It is demonstrated that Convective flows have great Effects on the solidification of immiscible alloys. A Convective flow against the solidification direction causes an increase in the nucleation rate while a Convective flow along the solidification direction causes a decrease in the nucleation rate. The Convective flows lead to a more uneven distribution of the minority phase droplets in the melt. It causes an increase in the size of the largest minority phase droplets and is against the obtaining of the immiscible alloys with a well dispersed microstructure.
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Convective Effect on the solidification of hypermonotectic alloys
Journal of Materials Research, 2011Co-Authors: Jiuzhou ZhaoAbstract:A model is developed to analyze the microstructure evolution in a continuously solidified hypermonotectic alloy. The model takes into account the common actions of the nucleation and diffusional growth/shrinkage of the minority phase droplets, the spatial phase segregation, and the convections of the melt. The microstructure formation in a continuously solidified hypermonotectic alloy is calculated. The numerical results demonstrate that the convections have great Effect on the microstructure formation. The Convective flow against the solidification direction causes an increase in the nucleation rate while the Convective flow along the solidification direction causes a decrease in the nucleation rate of the minority phase droplets. The convections lead to a more nonuniform distribution of the minority phase droplets in the melt. It causes an increase in the size of the largest minority phase droplets and is against the obtaining of the hypermonotectic alloys with a well-dispersed microstructure.
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Convective Effect on the microstructure evolution during a liquid-liquid decomposition
Applied Physics Letters, 2008Co-Authors: Jiuzhou ZhaoAbstract:The microstructure evolution during a liquid-liquid phase transformation was calculated. The Effect of convections on the microstructure development was investigated. The results demonstrate that the Convective flow against the solidification direction causes an increase in the local nucleation rate. Convections lead to a more nonuniform distribution of the minority phase droplets (MPDs) in the melt. They cause an increase in the size of the largest MPDs and are against the obtaining of the immiscible alloys with a well dispersed microstructure.
P Poesio - One of the best experts on this subject based on the ideXlab platform.
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Evidence of Convective heat transfer enhancement induced by spinodal decomposition.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: P Poesio, A M Lezzi, G P BerettaAbstract:Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the Péclet number, defined as the ratio between Convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the Péclet number is small - i.e., when viscosity and diffusivity are large - or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong Convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a 1-mm -thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of Convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but Effectively Convective Effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface H model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.
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Evidence of Convective heat transfer enhancement induced by spinodal decomposition.
Physical Review E, 2007Co-Authors: P Poesio, A M Lezzi, G P BerettaAbstract:Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the P\'eclet number, defined as the ratio between Convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the P\'eclet number is small---i.e., when viscosity and diffusivity are large---or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong Convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a $1\text{\ensuremath{-}}\mathrm{mm}$-thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of Convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but Effectively Convective Effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface $H$ model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.
Jiaxin Zhao - One of the best experts on this subject based on the ideXlab platform.
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Year-round performance analysis of a photovoltaic panel coupled with phase change material
Applied Energy, 2019Co-Authors: Jiaxin Zhao, Aotian SongAbstract:Abstract Phase change material (PCM) is in employed in photovoltaic (PV) system for thermal regulation and efficiency improvement. The hybrid system is named as a PV-PCM system. While progress is achieved in understanding system performance in laboratory and daily simulation, few results are reported in a seasonal and yearly basis, which requires substantial computation time to solve Navier-Stokes equations. In this study, an enhanced conductivity method is applied to simulate the Convective Effect without solving N-S equations. The model is developed based on 1-D thermal resistance model and validated with experimental data, possessing a good balance between accuracy and simplicity. The model is, therefore, adopted to examine and optimize seasonal and yearly PV-PCM performance. Within five systems simulated, the result suggests that systems perform diversely under different weather conditions. For instance, PV-PCM system with high melting temperature usually performs well in summer while might prevent heat transfer in winter since the PCM cannot be melt in cold days. Finally, the highest year-round improvement in electricity production 2.46% compared to reference PV system, which is lower than the value reported in most studies conducted only on a sunny day or in laboratory in a short-time scale. Moreover, the economic analysis indicates that, without a significant improvement in PCM performance or exploiting electricity-and-heat cogeneration, PV-PCM system may not be viable for real application at this stage.
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mathematical modelling and sensitivity analysis of solar photovoltaic panel integrated with phase change material
Applied Energy, 2018Co-Authors: Jiaxin ZhaoAbstract:Abstract It is reported that every degree rise in photovoltaic (PV) temperature could lead to a decrease in electricity output by 0.4–0.65%. Phase change material (PCM), which could absorb great amount of heat without raising the temperature of itself, is employed in this study to control PV module temperature and increase power generation. This kind of integrated system is the so-called PV-PCM system. In recent years, some work has already been conducted in using PCM for PV panel thermal regulation both numerically and experimentally, while some issues are still unsolved or unclear, for example, limited number of cases in simulation, difficulties in modelling PCM Convective Effect, the impact and uncertainty resulting from some common assumptions in numerical simulation. To examine these issues, an improved thermal resistance model through applying enhanced conductivity method is developed to incorporate PCM Convective Effect in 1-D model, offering a good compromise between accuracy and simplicity. The numerical simulation result illustrates that neglecting PCM Convective and radiative heat transfer will cause significant errors. Finally, based on simulation of over 300 cases, the two-variable analysis demonstrates that every 100 W/m2 increase in solar radiation can lead to about 5 °C increase in peak temperature, and an optimal performance can be achieved when the melting temperature of PCM is slightly higher, such as 5 °C, than the ambient temperature.
A M Lezzi - One of the best experts on this subject based on the ideXlab platform.
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Evidence of Convective heat transfer enhancement induced by spinodal decomposition.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: P Poesio, A M Lezzi, G P BerettaAbstract:Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the Péclet number, defined as the ratio between Convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the Péclet number is small - i.e., when viscosity and diffusivity are large - or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong Convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a 1-mm -thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of Convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but Effectively Convective Effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface H model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.
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Evidence of Convective heat transfer enhancement induced by spinodal decomposition.
Physical Review E, 2007Co-Authors: P Poesio, A M Lezzi, G P BerettaAbstract:Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the P\'eclet number, defined as the ratio between Convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the P\'eclet number is small---i.e., when viscosity and diffusivity are large---or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong Convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a $1\text{\ensuremath{-}}\mathrm{mm}$-thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of Convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but Effectively Convective Effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface $H$ model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.