SINGLE DROPLET GROWTH MODEL FOR DROPWISE CONDENSATION CONSIDERING NON-CONDENSABLE GAS
The purpose of present study is to develop a single droplet growth model for solving the heat and mass transfer process during dropwise condensation in the presence of non-condensable gas (NCG). Considering the multi-scale feature of droplet size, a Knudsen layer between the droplet and the continuous fluid region is introduced to incorporate the transition between the continuum and kinetic limit. The kinetic theory gases and the laws of continuum fluid dynamics are used to model the mass transfer process of vapor in the Knudsen layer and the continuous fluid region, respectively. The heat transfer through the droplet is determined by Fourier's law of heat conduction. These three regions (the continuous fluid region, the Knudsen layer and the droplet region) are incorporated by matching both the mass flow rate and the energy flow rate over the interface. From the present model, the droplet growth rate and the nucleation size of droplet can be evaluated. Furthermore, a numerical algorithm is developed to describe a consequence of the time-dependent sub-processes during dropwise condensation. Finally, the dropwise condensation process is
simulated by an association between the algorithm and the droplet growth rate and minimum radius from the growth model. Additionally, the average heat flux from simulation is compared with the results of dropwise condensation experiments of moist air. The effects of relative humidity and sub-cooling in dropwise condensation of moist air are also studied.