Surface Evaporation in a Solar Desalination CFD Simulation
In this project, the surface evaporation process in a 2D solar desalination system is simulated and analyzed.
This ANSYS Fluent project includes CFD simulation files and a training movie.
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Solar desalination introduction
In general, the main mechanism used in desalination plants is to evaporate the saltwater and then to distill the water vapor. Due to the high cost of this process, it has always tried to provide the energy needed for this process at the lowest possible cost. One of the best methods that has received a lot of attention in recent years is the use of solar energy to supply the energy needed for this process. However, the remarkable point in this regard is the evaporation of water, which should normally occur at 100 degrees of Celsius. In this method, it is not necessary to reach the temperature of 100 degrees, since in surface evaporation, the water can be vaporized at any temperature.
In this project, the surface evaporation process in a 2D solar desalination system is simulated and analyzed. In this process the surface of the fluid water will receive the warmth of solar rays, then based on the principles of surface evaporation, the water molecules on the surface of the water will start to evaporate. Finally, when the gauge pressure and temperature of water vapor reach 3000 Pa and 343.15 K respectively, it will leave the desalination system through the defined pressure outlet. The Laminar model is used for flow analysis. A UDF was used to determine the phase change method. The VOF multi phase model for three phases of air, water vapor and water fluid has been used to investigate the phase interactions. Gravity is also activated in this analysis due to the presence of buoyant and volumetric forces.
Solar desalination geometry and mesh
The geometry of this model is designed in ANSYS design modeler® and is meshed in ANSYS meshing®. The mesh type used for this geometry is structured and the element number is 938174.
CFD simulation settings
The key assumptions considered in this project are:
- Simulation is done using pressure-based solver.
- The present simulation and its results are transient. 2306 time steps with a step size of 0.05 seconds are exploited for this simulation.
- The effect of gravity has been taken into account and is equal to -9.81 m/s2 in Y direction.
The applied settings are summarized in the following table.
|(solar desalination)||Boundary conditions|
|Gauge pressure||3000 Pa|
|wall motion||stationary wall|
|Heat transfer coefficient||10 W/m2K|
|Free stream temperature||305.15 K|
|Heat generation rate||93500 W/m3|
|Wall thickness||0.01 m|
|(solar desalination)||Solution Methods|
|Volume fraction||second order upwind|
|momentum||second order upwind|
|energy||second order upwind|
|gauge pressure||3001 Pa|
|velocity (x,y)||(0,0) m/s|
|vapor volume fraction||0|
|Air volume fraction||0|
The contours of density, pressure, temperature, velocity, etc. are presented.
All files, including Geometry, Mesh, Case & Data, are available in Simulation File. By the way, Training File presents how to solve the problem and extract all desired results.