共查询到19条相似文献,搜索用时 346 毫秒
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相变微胶囊悬浮液是一种新型的蓄热-传热功能流体,目前对相变微胶囊与基液流固传递作用认识的欠缺,导致宏观上对悬浮液流动传热性能的研究结果存在较大的差异.为此,本文采用任意拉格朗日-欧拉方法模拟相变微胶囊在液冷微通道内流固作用下的流动传热特性,对比普通颗粒及相变胶囊对液冷微通道壁面温升的抑制作用,考察胶囊位置、形状及数量对壁面温升抑制的影响.结果表明:胶囊及颗粒均对它们上游区域的壁面温升产生抑制作用,而胶囊的相变使得抑制效果更加明显;胶囊越靠近壁面自旋运动越快,越有利于流体与壁面的换热,对壁面温升抑制效果越强,尤其是靠近受热面时;相比椭圆形胶囊,圆形胶囊自旋运动更激烈,对壁面温升抑制效果更优;随着加热区内胶囊数的增加,最大抑制效果在逐渐提升. 相似文献
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小通道扁管内纳米流体流动与传热特性 总被引:2,自引:0,他引:2
建立了测量小通道扁管内纳米流体流动与对流换热性能的实验系统,测量了不同粒子体积份额的水-Cu纳米 流体的管内对流换热系数和摩擦阻力系数,实验结果表明,在相同雷诺数条件下,小通道扁管内纳米流体的对流换热系数 大于纯液体,且随粒子的体积份额的增加而增大,而纳米流体的阻力系数并未明显增大。 相似文献
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M. K. Rathod 《实验传热》2013,26(1):40-55
Thermal performance of a latent heat storage unit is evaluated experimentally. The latent heat thermal energy storage system analyzed in this work is a shell-and-tube type of heat exchanger using paraffin wax (melting point between 58°C and 60°C) as the phase change material. The temperature distribution in the phase change material is measured with time. The influence of mass flow rate and inlet temperature of the heat transfer fluid on heat fraction is examined for both the melting and solidification processes. The mass flow rate of heat transfer fluid (water) is varied in the range of 0.0167 kg/s to 0.0833 kg/s (1 kg/min to 5 kg/min), and the fluid inlet temperature is varied between 75°C and 85°C. The experimental results indicate that the total melting time of the phase change material increases as the mass flow rate and inlet temperature of heat transfer fluid decrease. The fluid inlet temperature influences the heat fraction considerably as compared to the mass flow rate of heat transfer fluid during the melting process of the phase change material. 相似文献
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本文建立了小型平板CPL蒸发器毛细多孔芯内汽液两相流动与传热的模型以及金属外壁和工质区的导热模型,并进行耦合求解.分析了金属侧壁效应对蒸发器性能的影响,提出小型平板CPL存在着侧壁效应传热极限.数值结果表明,工质蒸发发生在多孔芯加热表面附近,蒸发器采用单一金属外壁时由于侧壁效应导致系统传热极限低,而上壁采用导热系数大,侧壁及下壁采用导热系数小的新型结构能够明显的提高系统的传热能力,同时使加热表面的温度维持在较低的水平. 相似文献
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单个颗粒的传热过程对于燃煤流化床锅炉中煤的着火和随后的燃烧过程具有重要的影响。本文建立了一个基于Euler-Lagrange方法的数学模型对其进行了数值研究。该模型对流体相的运动和传热规律以Euler。方法描述,对固体颗粒相则以近年来发展起来的离散单元方法(DEM)在颗粒层次上进行描述。研究结果表明颗粒与床层之间有很高的传热系数。另外,对单个颗粒温度变化过程的模拟研究表明,颗粒经过较短的时间便能接近床层的温度,且不同颗粒具有类似的温度变化特性。 相似文献
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潜热型热功能流体强化换热分析 总被引:4,自引:0,他引:4
本文建立了分析带有相变微胶囊的潜热型热功能流体的流动和换热过程数理模型,应用有限差分法和移动热源法进行联合求解。计算结果表明,相变微胶囊的加入:较好地提高了流体的换热性能。获得了相变颗粒大小和体积分数对强化换热影响等结果。计算结果对该类流体的设计和应用提供了理论依据。 相似文献
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Characterization of size effect of natural convection in melting process of phase change material in square cavity 下载免费PDF全文
《中国物理 B》2021,30(10):104403-104403
The accelerating effect of natural convection on the melting of phase change material(PCM) has been extensively demonstrated. However, such an influence is directly dependent on the size and shape of domain in which phase change happens, and how to quantitatively describe such an influence is still challenging. On the other hand, the simulation of natural convection process is considerably difficult, involving complex fluid flow in a region changing with time, and is typically not operable in practice. To overcome these obstacles, the present study aims to quantitatively investigate the size effect of natural convection in the melting process of PCM paraffin filled in a square latent heat storage system through experiment and simulation, and ultimately a correlation equation to represent its contribution is proposed. Firstly, the paraffin melting experiment is conducted to validate the two-dimensional finite element model based on the enthalpy method.Subsequently, a comprehensive investigation is performed numerically for various domain sizes. The results show that the melting behavior of paraffin is dominated by the thermal convection. When the melting time exceeds 50 s, a whirlpoor flow caused by natural convection appears in the upper liquid phase region close to the heating wall, and then its influencing range gradually increases to accelerate the melting of paraffin. However, its intensity gradually decreases as the distance between the melting front and the heating wall increases. Besides, it is found that the correlation between the total melting time and the domain size approximately exhibits a power law. When the domain size is less than 2 mm, the accelerating effect of natural convection becomes very weak and can be ignored in practice. Moreover, in order to simplify the complex calculation of natural convection, the equivalent thermal conductivity concept is proposed to include the contribution of natural convection to the total melting time, and an empirical correlation is given for engineering applications. 相似文献
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针对爆炸粉末烧结过程中颗粒间的摩擦效应提出了一种无夹角斜碰撞模型,分析了烧结过程中颗粒间摩擦力随温度的变化规律,借助于LS-DYNA有限元程序研究了冲击压力、颗粒大小、材料强度等因素对孔隙闭合时间的影响,给出了颗粒界面温升的表达式。研究结果表明,由摩擦引起的颗粒界面的温升与材料特性、颗粒度、冲击角度、冲击压力等因素有关,随材料的蓄热能力、传热能力和材料强度的增加而减小,并随着材料疏松程度、颗粒直径、冲击压力的增加而增加;在粉末颗粒直径和冲击压力不是太小的情况下,颗粒表面温度将达到材料的熔点。 相似文献
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Laser‐supported processes can be used to modify the electrical and thermal properties of ceramic substrates locally. These processes are characterized by a strong thermal interaction between the laser beam and the ceramic surface that leads to localized melting. During the dynamic melting process an additive material is injected into the melt pool in order to modify the physical properties. The heat and mass transfer during this dynamic melting and solidification process has been studied numerically in order to identify the dominating process parameters. Simulation tools based on a finite‐volume method have been developed to describe the heat transfer, fluid flow and the phase change during the melting and solidification of the ceramic. The results of the calculation have been validated against experimental results. 相似文献