Condensation of refrigerant inside the circular tube
 

I am working on simulation of condensation of refrigerant inside the circular tube.
In this problem i have used Eulerian multiphase model ..It s asking bubble diameter for secondary phase(refrigerant in liquid phase)....how do i calculate it....Another problem is operating pressure .....My inlet pressure is 15.5 bar and outlet is 15.3....then what would be the pressure outlet condition and....... operating pressure.

Dear Vishal

Will u please elaborate your problem in detail.

Hi ,
Dear sir,
I am working on condensation of refrigerant inside the smooth long circular tube. I am using fluent for the same. My problem setup is like this
Models -
1.Multiphase-Eulerian
2.Energy
3.K-e,realizable,std wall,mixture
Materials-
1.R404a-vapor(primary phase)-Its properties
2.R404a-liquid-(secondary phase)-Its properties
Phases
1.Primary-R404a-vapor
2.Secondary-R404a-liquid
-Bubble diameter1e-05(assumed-do not know)
phase interaction
Drag-Symmetric
Heat-ranz marshall
Mass transfer-r404a vapor to r404a-liquid through evaporation condensation at constant saturation temp.
surface tension constant
Boundary conditions
Inlet -Velocity inlet for mixture and each phase(Turbulence intensity 4% & Hydraulic dia 0.00814mm for each phase)
outlet-pressure outlet-0 gauge pressure
tube wall at constant wall temp.much more below saturation temp.
operating pressure is atm.(:confused:my condensing pressure is 15 bar gauge..... what to be used operating pressure and pressure at the outlet)
Solution method
phase coupled simple
Volume fraction-modified HRIC, all others Quick
initialization from all zones.
I have not included Enthalpy
My solution giving no condensation at any point in the tube........not a single sign.
am i going in right way
Please help me.