Learning Forum

[abdullahhassan]

Hello, 

I am working on condensation of ammonia in heat exchanger. 

I have started to work on Eulerina Multiphase model and in Phase interaction > heat, mass, reaction> mass > evporation - condensation tab, i found another model which is PHASE CHANGE MODEL with scaling factor. shown in below image. 

can you please explain from & to phase scaling factor. 

suppose i am doing condensation & i have put vapor in From Phase and liquid in To Phase.

aand secondly, 

after initiating this step, ansys automatically inputted heat transfer co-efficient values as Ranz-marshall in Vapor--interphase heat transfer & Zero Resistance in Liquid-Interphase heat transfer. can you explain this zero resistance ? what is this specific step. 

[SRP]

Hi,

The TPC (Thermal Phase Change) model works in the Eulerian multiphase framework. It applies the two-resistance approach where a separate heat transfer process is considered for either side of the phase-interface with different heat transfer coefficients. The thermal phase change model uses scaling factors (Cl and Cv) to calculate the heat transfer from the interface to the liquid phase or gas phase. The default value is 1.

You can refer to fluent theory guide to understand equations used in the background: 14.7.5. Evaporation-Condensation Model (ansys.com)

The zero resistance is equivalent to an infinite phase specific heat transfer coefficient. For example, if  its effect is to force the interface temperature to be the same as the phase temperature.

For more details, please check fluent theory guide: 14.5.17. Description of Heat Transfer (ansys.com)