Evaporation

Simulation of evaporation of water droplets

The setup consists of a box with an air inlet and outlet, containing two water droplets of different sizes. The setup simulates evaporation of these droplets and the evaporation rate can be controlled by changing initial temperature, heat capacity of air, humidity and other parameters defined in the Ucv file. Here should be a picture

Figure 1: Setup at the start of simulation

Figure 2: Mid-simulation results

Based on the calculated evaporation rate, the setup shrinks the free surface around the droplets which reduces the number of interior points. As a result, the droplet gets smaller with each time-step. This can also be observed with a plot of Number of droplet interior points vs Time : Here should be a picture

Figure 3: Number of droplet interior points decreasing with time

The movement of free surface present around the droplets is defined using MOVE(0) statement.

MOVE(0) = ( [if (Y%ind_cham% = &CHAMBER_Water&) :: %MOVE_MassChangeRate% else :: %MOVE_VolumeChangeRate% endif], ... [if (Y%ind_cham% = &CHAMBER_Water&) :: equn($EQ_movemasschangerate_freesurface_water$) else :: equn($EQ_movevolumechangerate_freesurface_air$) endif], ... )

There are three types of simulation that can be carried out in this setup: "COUPLED", "WATER_ONLY" and "AIR_ONLY". Simulation type can be selected in the Ucv file.

COUPLED : Simulates evaporation of water droplets under a constant air flow.
WATER_ONLY : Simulates evaporation of water droplets without an air flow.
AIR_ONLY : Simulates evaporation of obstacle under a constant air flow.

The simulation ends when either the given end-time is reached or there are no more points left inside the free surface of droplet which is equivalent to droplets being completely evaporated. TimeLapseFactor is used to speed-up the evaporation process, making it possible to simulate longer run time in a feasible duration. NOTE: Initial air temperature should be given higher than initial water temperature.