Recent Work on Theoretical Modeling of Condensation and Freezing Heat Transfer Phenomena

P. Cheng*, C Zhang, X Li and J Zhao

School of Mechanical Engineering, Shanghai Jiaotong Univerisity, Shanghai, P. R. China

 

Abstract-Recent work on theoretical modeling of condensation and freezing phenomena, carried out at Shanghai Jiaotong University, will be summarized in this paper. Analytical modeling of dropwise condensation based on an improved classical model of LeFevre and Rose (1966) will be presented. It is shown that the condensation heat flux predicated by this improved analytical model, without any fitting constants, is in agreement with existing experimental data. Direct numerical simulations on filmwise and dropwise condensation heat transfer on a vertical cold plate, based on single-component phase-change lattice Boltzmann method, have been carried out. Transition from dropwise to film condensation on a hydrophobic downward-facing horizontal cold flat plate under constant wall temperature conditions has been investigated and complete dropwise condensation curves are obtained. A multi-component phase-change LB model has been developed, and effects of non-condensable gas on film condensation in forced condensation flow along a horizontal cold plate have been investigated. Condensate film thickness, distributions of velocity, temperature and NCG fraction in the entire flow field, as well as condensation heat transfer on the cold plate are obtained numerically. The accuracy of this multi-component phase-change has been validated by comparison with the similarity solution given by Sparrow, Minkowycz and Saddy (1967).  In addition, a triple phase-change lattice Boltzmann method, based on a coupling of existing vapor-liquid phase-change model and enthalpy-based liquid-solid phase-change model, has been developed. This triple phase-change LB model is applied to (i) condensation and freezing on a cryogenic spot on a vertical flat plate, (ii) condensation and freezing outside an array of horizontal cold cylinder, and (iii) droplet impact and freezing on a cryogenic cold spot of a horizontal hydrophobic surface. These theoretical modeling and simulation work provide further physical insights on condensation and freezing heat transfer phenomena.