Optical Measurement of Solidification Ratio in Phase Change Slurry considering Refraction in Droplets

本研究的目的是建立一种光学方法来测量石蜡液滴在相变浆液中的凝固率。为此，利用蒙特卡罗方法建立了一个分析模型。该模型计算了波长为670 nm的激光对相变浆料层的透射率和反射率。对含有不同直径和不同光学性质的石蜡颗粒的浆料进行了实验，测量了670 nm激光对相变浆料层的透过率和反射率。分别对固化石蜡颗粒和液体石蜡颗粒进行了实验研究，得到了以下结果：1.建立了670 nm激光作用下含凝固石蜡液滴和液化石蜡液滴的相变浆料层透射率和反射率的计算模型。通过与其他研究人员的分析和实验结果的比较，验证了分析模型的结果。结果表明，由于层中石蜡粒子的固化，液滴表面形成空洞，导致反射率增大，透射率降低。采用表面带有凹陷的固体粒子模型，对薄膜透射率和反射率的分析结果与相应的实验结果吻合较好。通过将分析结果与相应的实验结果进行比较，建立了考虑固体粒子表面凹陷的分析模型，从而可以估算石蜡粒子在相变过程中的固化率。

The objective of the present study is to develop an optical method to measure the solidification ratio of paraffin droplets suspended in phase change slurry. For the purpose, an analytical model was developed using the Monte Carlo method. The model calculates the transmittance and reflectance of the phase change slurry layer for laser beam with a wavelength of 670nm. The slurry contains paraffin particles with different diameters and different optical properties Experiments were also carried out to measure the transmittance and reflectance of the phase change slurry layer for laser beam with a wavelength of 670nm. The experiments were carried out for both solidified paraffin particles and liquid paraffin particles.From those study, following results are obtained;1. A model is developed to calculates the transmittance and reflectance of phase change slurry layer containing either solidified or liquefied paraffin droplets for laser beam with a wavelength of 670nm2. The results of the analytical model are confirmed by comparing the results with the analytical and experimental results of other researchers' studies.3. The cause of the increase in the reflectance and the decrease in the transmittance of the layer by the solidification of the paraffin particles in the layer is proved to be the formation of cavities on the droplet surfaces. And, the analytical results of the transmittance and the reflectance of the layer fit very well with the corresponding experimental results by using a solidified particle model with a dimple on the surface.By using the developed analytical model incorporating solid particle with a dimple on the surface, the estimation of solidification ratio of paraffin particles in phase change becomes possible by comparing the analytical results and the corresponding experimental ones.