I am attempting to recreate / verify Fadhl, et. al. "Numerical modelling of the temperature distribution in a two-phase closed thermosyphon" and am having much trouble with the condensation mechanism. Evaporation works just fine, as shown in the picture. However, there is no condensation at all, even with other attempts and different geometries. I have been trying for over a month on this one problem, any insight would be greatly appreciated!
My setup: (all numeric values taken from Fadhl's report)
Planar 2D Space, Transient, Gravity in -x
Materials: water-vapor, water-liquid (liquid has polynomial density)
Multiphase: VOF, primary phase is vapor, secondary is liquid; (surface tension coefficient polynomial), wall + jump adhesion enabled. 1 mass transfer mechanism set up, liquid to vapor, evaporation condensation with frequncies 0.1, 0.1, saturation temperature at 373.
Viscous: standard k-e, enhanced wall treatment, thermal effects
Boundary Conditions: evaporator has constant heat flux of 12,505 W/m2, condenser has convection with hc = 707.6 W/m2-K and stream temp 301.45 K, adiabatic section has zero heat flux
Methods: SIMPLE setup, PRESTO, first-order upwind, georeconstruct, residuals under 0.0001
Thank you in advance!
Hi
I did the same simulation with no condensation.
you can use the following tutorial:
https://www.youtube.com/watch?v=Hk_DgX53nV0
if you found the problem let me know.
If you are considering water as a heat transfer fluid, use evaporation frequency 0.1 and condensation frequency 180.
In Fluent, evaporation frequency (Be), and condensation frequency (Bc) have been set equal to 0.1. However, Be and Bc should be set with being proportional to vapor density and liquid density. If they have the same value, the amount of the mass transfer in the phase change won't be able to keep the balance because of the difference between the liquid density and the vapor density. As a result, you might have a hard time in the convergence of continuity eq. as well. In the Fadhlstudy, the mass transfer time relaxation parameter for the condensation ( Bc ) has been calculated using the equation, Bc = Bv * ( liquid density / vapor density). = 0.1*( 1000/0.55) = 181 (approximate).)
Also, I have a question regarding your boundary condition set up, Why are you using the k-epsilon model?
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