Mathematical Problems in Engineering
Volume 2015, Article ID 370159, 8 pages
http://dx.doi.org/10.1155/2015/370159
Parameter Sensitivity of the Microdroplet Vacuum Freezing Process
1School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110004, China
2School of Mechanical Engineering, Shenyang University, Shenyang 110044, China
3Shenyang Aircraft Design and Research Institute, Shenyang 110035, China
Received 12 August 2014; Accepted 7 September 2014
Academic Editor: Gongnan Xie
Copyright © 2015 Zhijun Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
The vacuum freezing process of microdroplets (<100 μm in diameter) is studied by dynamic mesh method. The mass transfer coefficient was studied using the results of related papers that considered droplet diameters exceeding 1 mm. The diameter, initial temperature, and vacuum chamber pressure effects are also discussed. To estimate parameter sensitivity, the effects of material density, specific heat, and thermal conductivity in 20% scope, as well as latent evaporation/sublimation in 5%, were simulated. The results show that the mass transfer coefficient is essentially different between microdroplets (<100 μm) and macrodroplet (>1 mm). Pressure and droplet diameter have an effect on cooling and freezing stages, but initial temperature only affects the cooling stage. The thermal conductivity coefficient affected the cooling stage, whereas affected the freezing stage. Heat capacity affected the cooling stage, but has virtually no effect on all stages. The actual latent heat of freezing was also affected. Higher density corresponds to lower cooling rate in the cooling stage.