A polynomial temperature profile model for suspended droplet evaporation over a wide range of ambient pressures and convection conditions

The suspended droplet technique has been widely applied in experimental droplet evaporation studies, but heat conduction caused by support fiber can change the evaporation characteristics. In the present study, a novel theoretical model is proposed to investigate the effect of a suspender on droplet heating and evaporation. Considering the vortex circulation inside the droplet and the heat diffusion along the support fiber, the temperature distribution is assumed to exhibit a polynomial profile. The effects of pressure on the thermodynamic and transport properties are also accounted for. The simulation results are consistent with previous experimental data over a wide range of ambient pressures and convection conditions. The performance of the new model is further compared with that of other models in terms of computational efficiency and accuracy. The new model requires an order of magnitude less CPU time than does the effective thermal conductivity model to preserve the key features of the temperature distribution accurately. In addition, a dual effect of the fiber diameter on the evaporation rate is demonstrated. With increasing fiber diameter, the evaporation rate increases and then decreases. There are two different patterns that can depict heat transfer between the suspended droplets and the fibers: an "immersed area pattern" and a "fiber temperature pattern". A switchover in the two patterns is responsible for the dual effect, which occurs at a threshold fiber diameter related to the environment.