Srinivasan Seshasai
W Booth School of Engineering Practice and Technology, McMaster University, Hamilton, ON L8S 4L8, Canada.
Foods. 2021 Dec 24;11(1):46. doi: 10.3390/foods11010046.
A three-stage solidification model for food droplets has been implemented in a computational fluid dynamics code. It comprises of an initial cooling stage that is based on the principles of convective heat transfer. This is followed by the solidification period that is initiated once the droplet cools to a phase change temperature. Finally, when the droplet is completely solidified, the tempering phase begins where the droplet cools to the temperature of the ambient air. The model has been validated with respect to the experimental data for cocoa butter. Additional simulations were made in which the crystallization behavior of the cocoa butter droplets in relation to the droplet size, ambient air temperature and the relative drop-gas velocity was investigated. It was found that the crystallization time is exponentially related to the droplet size. Further, it increased with the ambient temperature, but decreased with the relative drop-gas velocity. Overall, the results suggest operating at the extreme values of the process parameters, requiring high amount of energy, to minimize the crystallization time. It was concluded that there is a need for optimizing the operating conditions of the powder production process to minimize the energy requirement of the system while maintaining a reasonable crystallization time.
一种用于食品液滴的三阶段凝固模型已在计算流体动力学代码中实现。它包括基于对流热传递原理的初始冷却阶段。接下来是凝固期，一旦液滴冷却到相变温度，凝固期就开始。最后，当液滴完全凝固时，回火阶段开始，此时液滴冷却到环境空气的温度。该模型已针对可可脂的实验数据进行了验证。还进行了额外的模拟，研究了可可脂液滴的结晶行为与液滴尺寸、环境空气温度和相对液滴 - 气体速度的关系。发现结晶时间与液滴尺寸呈指数关系。此外，它随环境温度升高而增加，但随相对液滴 - 气体速度降低。总体而言，结果表明在过程参数的极值下运行，这需要大量能量，以最小化结晶时间。得出的结论是，需要优化粉末生产过程的操作条件，以在保持合理结晶时间的同时最小化系统的能量需求。
