共查询到20条相似文献,搜索用时 531 毫秒
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基于植物根系仿生的土壤热湿迁移数值模拟 总被引:1,自引:0,他引:1
以实验数据为依据,把土壤中的水分含量和水分梯度分布作为影响植物根系生长的环境因子,结合非饱和多孔介质中传热传质的数学模型,对冬小麦的根系生长进行仿生模拟,分析根系吸水对非饱和土壤湿分与热量传递的影响。在相同环境条件下,对裸土和有作物覆盖的土壤床中的热、湿迁移也进行了模拟比较。 相似文献
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多孔介质高强度传热传质的理论研究 总被引:3,自引:0,他引:3
提出了高强加热下含湿多孔介质传热传质新模型,模型包括的水分种类齐全、水分迁移机制全面,假设条件相对较少,考虑了非Fourier传热效应和非Fick传质效应,模型通过具体的含湿量分区分析得到简化。 相似文献
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Convective heat transfer coefficients were measured experimentally for a tube immersed vertically in a circulating fluidized bed. Circulating fluidized beds operate in the dilute transport regime of two-phase (solid/gas) flow. The dominant mechanism for heat transfer to surfaces is particle-induced convection. In this study, experiments were carried out in a circulating fluidized bed of15 cm diameter and 11 m height. An instrumented tube of 9.5 mm diameter and 1.3 m length was placed vertically at the centeriine of the fluidized bed to measure convective heat transfer coefficients at several different elevations in the bed. Three types of particles, with mean diameters ranging from 68 to 2S1 urn, were used in the experiments at superficial gas velocities in the range of 1.3 to 8.2 m/s. Results showed that the convective heat transfer coefficients with solid/gas two-phase circulation were two to three times greater than those for single-phase gas convection at the same velocity. For a given gas velocity, the coefficients increased with increasing solid mass flux, but decreased with elevation. It was demonstrated that the heat transfer coefficients for the immersed tube and for the bed wall could be correlated with different functional dependence on the two-phase suspension density. 相似文献
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雾化喷射冷却的机理及模型研究 总被引:2,自引:0,他引:2
雾化喷射冷却的换热机理十分复杂,目前其研究还很不成熟。本文从喷射雾滴的特性参数出发,以被冷却表面上形成的喷射液膜为对象,考虑了冷却液体向环境的散热,建立质量、能量守恒方程,得到半经验半解析的雾化喷射换热模型。其中,本文提出真换热系数和显换热系数的概念,认为显换热系数受空间散热影响,而真换热系数只与喷雾动量有关。最后设计了雾化喷射局部换热实验,对模型进行检验,结果表明,该模型能够较好地符合实验所得的换热系数及加热面表面温度沿喷射半径的分布趋势。 相似文献
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微通道内超临界二氧化碳的压降与传热特性 总被引:4,自引:0,他引:4
进行了微通道内超临界CO2的局部和平均传热与压降特性实验研究。结果表明,临界点附近物性参数的剧烈变 化使压降增大,但传热被大大强化。同时也发现,系统压力、质量流速及CO2温度对流动与传热特性有重要影响。在大 量实验数据的基础上,得出了冷却条件下水平微通道内超临界CO2强制对流换热关联式。 相似文献
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Abstract Heat and mass transfer rates from complex surfaces to a turbulent channel flow were measured using an infrared imaging system and the naphthalene sublimation technique, respectively. The surfaces are composed of spherical particles embedded either in a layer of thermally conducting, nonevaporating liquid or in an isothermal layer of subliming naphthalene. The experimental results indicate that, in general, the surface heat and mass transfer coefficients vary as the surface roughness increases, whereas the surface heat transfer coefficient changes as the solid-to-liquid thermal conductivity ratio is varied. Mass transfer rates exhibit less sensitivity to variations in the naphthalene height for surfaces composed of smaller particles, and heat transfer rates from surfaces of smaller particles remain fairly constant as the liquid level and thermal conductivity ratios are varied. The results are discussed relative to drying of partially wetted surfaces with surface complexity induced by the presence of droplets upon an impermeable substrate or a receding moisture front in a bed of granular material. 相似文献
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Macroscopic laws of heat and mass transfer at gas-phase ignition of solid condensed substance with relatively low calorific power by a typical local energy source, namely, a small hot metal particle shaped as a parallelepiped, are investigated. The proposed model takes into account a group of interrelated processes of heat and mass transfer with thermal decomposition and chemical reaction in the interaction of solid and a source with limited energy content. The influence of the heat content of a local energy source on the characteristics of the process is analyzed. 相似文献