Thermo-Mass Coupling Fractal Study of Wet Phase-Change Rough Porous Materials
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摘要:
多孔材质复杂的内部结构和含湿状态对传热和传质特性有着重要意义，其热质耦合传递过程广泛存在于能源开发和工程隔热等领域。不同于在多孔材质理想状态下对传热和传质特性的单方面分析，该文将孔道的分布参数、粗糙表面、含湿状态和相变等因素考虑进去，运用分形理论推导出了含湿相变粗糙表面多孔材质的渗流系数和耦合等效导热系数的表达式。结果表明，渗流系数与面积分形维数、含湿饱和度呈正相关，与相对粗糙度、迂曲分形维数呈负相关；耦合等效导热系数与渗流系数、相变量呈正相关，与相对粗糙度呈负相关。此外，结果还表明，相变量以及相变引起的气体膨胀压强差对热质耦合传递也有着重要影响。
Abstract:The complex internal structures and moisture states of porous materials are of great significance to heat and mass transfer, and their coupling heat and mass transfer processes widely exist in energy development and engineering heat insulation. Beyond the unilateral analysis of heat and mass transfer characteristics of porous materials under ideal conditions, the distribution parameters of porous channels, rough surface, wet states and phase-change were considered, and the fractal theory was used to deduce the expressions of the seepage coefficient and the coupling equivalent thermal conductivity of porous materials with wet phase-change rough surface. The results show that, the seepage coefficient is positively correlated with the area fractal dimension and the moisture saturation, and negatively correlated with the relative roughness and the tortuous fractal dimension. The coupling equivalent thermal conductivity is positively correlated with the seepage coefficient and the phase variable, but negatively correlated with the relative roughness. In addition, the phase variable and the gas expansion pressure difference caused by phase-change also have important effects on the coupling heat and mass transfer.
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Key words:
- moisture saturation /
- phase-change /
- rough surface /
- thermo-mass coupling transfer /
- fractal
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图 2 等效导热系数λdeff与孔隙率φ的关系
Figure 2. The relationship between equivalent thermal conductivity λdeff and porosity φ
图 3 面积分形维数Df对环状渗流系数kcw的影响
Figure 3. The influence of area fractal dimension Df on annular seepage coefficient kcw
图 4 迂曲分形维数Dt对环状渗流系数kcw的影响
Figure 4. The influence of tortuous fractal dimension Dt on annular seepage coefficient kcw
图 5 饱和度s对环状渗流系数kcw的影响
Figure 5. The influence of saturation s on annular seepage coefficient kcw
图 6 渗流系数对等效导热系数λdeff的影响
Figure 6. The effect of the seepage coefficient on equivalent thermal conductivity λdeff
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