Condensation Microchannel VOF

Nik_Benve · December 6, 2019, 06:27

Hello,
currently i'm working on a multiphase cfd simulation on Ansys Fluent.
I'm trying to simulate the condensation process of r134a (refrigerant) in a veretical microchannel 3.4mm wide and 300mm. The vapour enters at saturation conditions and volume fraction 1. The free stream velocity is 1.99 m/s (G=100 kg/s; density=50.085 kg/m^3).
I'm working in a 2D axysimmetric geometry. The grid is a structured mesh with 510000 and y+ =1.
I chose the k-w SST model with low reynolds correction and implicit formulation for VOF, as i'm trying to obtain a stationary result.
Moreover i wrote a UDF to implement the Lee Model for condensation, defining the Mass Transfer properties.

Right now I'm really struggling to obtain a good convergence of the continuity equation. Indeed the mass flow rate difference between inlet and outlet increases at first and the start to fluctuate.
Any Suggestion?

Thanks for your attention!

neelcfd · April 5, 2022, 05:05

What coefficients are you using for Lee's Model? This coefficients have strong impact on mass balance.

December 6, 2019, 06:27	Condensation Microchannel VOF	#1
Nik_Benve New Member Nicola Benvenuti Join Date: Dec 2019 Location: Italy Posts: 1 Rep Power: 0	Hello, currently i'm working on a multiphase cfd simulation on Ansys Fluent. I'm trying to simulate the condensation process of r134a (refrigerant) in a veretical microchannel 3.4mm wide and 300mm. The vapour enters at saturation conditions and volume fraction 1. The free stream velocity is 1.99 m/s (G=100 kg/s; density=50.085 kg/m^3). I'm working in a 2D axysimmetric geometry. The grid is a structured mesh with 510000 and y+ =1. I chose the k-w SST model with low reynolds correction and implicit formulation for VOF, as i'm trying to obtain a stationary result. Moreover i wrote a UDF to implement the Lee Model for condensation, defining the Mass Transfer properties. Right now I'm really struggling to obtain a good convergence of the continuity equation. Indeed the mass flow rate difference between inlet and outlet increases at first and the start to fluctuate. Any Suggestion? Thanks for your attention!

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April 5, 2022, 05:05		#2
neelcfd New Member Neel Join Date: Nov 2018 Posts: 12 Rep Power: 7	What coefficients are you using for Lee's Model? This coefficients have strong impact on mass balance.