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首页> 外文期刊>Journal of Heat Transfer >Modeling of Thermophysical Processes in Liquid Ceramic Precursor Droplets Heated by Monochromatic Irradiation
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Modeling of Thermophysical Processes in Liquid Ceramic Precursor Droplets Heated by Monochromatic Irradiation

机译：单色辐射加热的液态陶瓷前驱液滴中热物理过程的建模

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摘要

A transient heat and mass transfer model is formulated to describe radiative heating of ceramic precursor droplets in a nonconvective environment. Heating causes vaporization of solvent from the droplet and concentration of the solute within the droplet leading to precipitation of the solute. It is found that the temperatures within the droplets are fairly uniform, but show different spatial profiles depending on the characteristics of solute absorptivity and duration of radiative heating. Incident laser irradiance and wavelength were found to play a significant role in the temperature profiles within droplets due to the absorption characteristics of the solute and the solvent. Lower levels of incident laser irradiation allows longer times for mass diffusion within a droplet leading to a gradual increase of the solute concentration from its center to its surface. Based on an equilibrium homogeneous precipitation hypothesis, it is found that the droplets heated with low laser irradiance tend to form thick precipitate shells as compared to those exposed to higher irradiances and consequently faster rates of vaporization. Large droplets form thin shells through surface precipitation, while small droplets may precipitate into shells of varying thickness depending on the magnitude of irradiance. Comparisons with con-vective heating in a high temperature plasma indicate that, with proper tuning of the laser irradiance, similar internal temperatures and solute concentration distributions are achievable. These modeling results suggest that different particle morphologies can be obtained from processing of liquid ceramic precursor containing droplets by proper tailoring of radiation parameters (wavelength and irradiance level).
机译：建立了瞬态传热传质模型，以描述非对流环境中陶瓷前驱体液滴的辐射加热。加热导致溶剂从液滴蒸发并在液滴内溶质浓缩，导致溶质沉淀。发现液滴内的温度相当均匀，但是根据溶质吸收率的特性和辐射加热的持续时间显示出不同的空间分布。由于溶质和溶剂的吸收特性，发现入射激光辐照度和波长在液滴内的温度曲线中起着重要作用。较低水平的入射激光辐照允许液滴内的质量扩散时间更长，从而导致溶质浓度从其中心到表面逐渐增加。基于平衡的均匀沉淀假设，发现与暴露于较高辐照下的液滴相比，以较低的激光辐照加热的液滴倾向于形成较厚的沉淀壳，因此汽化速率更快。大液滴通过表面沉淀形成薄壳，而小液滴可能沉淀到厚度不同的壳中，具体取决于辐照强度。与高温等离子体中对流加热的比较表明，通过适当调整激光辐照度，可以实现相似的内部温度和溶质浓度分布。这些建模结果表明，通过适当地调整辐射参数（波长和辐照度），可以从含有液滴的液态陶瓷前体的加工中获得不同的颗粒形态。

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