Conclusions and Future Work
In this article, a condensation simulation of moist
air on a cold metal plate with a low-degrees-of-freedom model was developed in
ANSYS Fluent by using the energy equation solver and Mixture Model which is
based on Lee Model. This simulation forms a part of research relating to the
problem of condensation behaviour in the climate chamber of the Four-Roller Test Bench at Technische Universität
Some accommodation coefficients in the simulation case
must be determined from experimental data, and an experiment model was
therefore designed which used a Peltier element to cool an aluminium plate and
a climate chamber to control the temperature and the humidity of air. Comparing
the results of simulation and experiment, the condensation simulation in Fluent
has a certain validity for the study of condensation conditions, such as the
time point, position and temperature at which liquid occurs. However, the
volume of condensate water is far below the actual value when the residual
continuity value is at about 10-3.
Evaporation and condensation happen at the same time
and heat transfer and mass transfer are strong in the simulation and experiment.
This was reflected in the accumulation of small droplets and the disappearing
of big drops, which cannot be replicated in the simulation as it is hard to include
all of the physics in dropwise condensation with a very good accuracy. On the
contrary, condensation simulations are possible under some special conditions
that cannot be realized in experiments.
In a future study, condensation simulation will be
applied to the Four-Roller Test Bench. In this case, the air flow will be more
complicated than for laminar flow as the flow will become turbulent flow, and the
same goes for heat transfer and mass transfer. Another target for future
investigation is to research corrosion on metal surfaces caused by water condensation,
where chemical changes need to be considered through use of the Reactions
solver of the multiphase model in Fluent.
It is recommended that for further studies appropriate
settings be determined to obtain a better convergence behaviour and larger
amount of condensate water in a complex geometry model with fine grids.
However, the increasing accuracy of the solution will at the price of computer
resources, CPU computational power and calculation time.