Learning Forum

[samiasadaf_uetian]

Hello everyone...I am working on flow boiling through microchannel using Multiphase VOF method on Ansys Fluent (Transient flow)
I am new to ansys and also to this research topic and have started from relatively a simpler geometry (horizontal 2D rectangular channel with 70mm in length and 1mm in height)

Boundary conditions : Inlet: velocity 0.01m/s temperature:372.14K, Outlet : 0Pa, temperature 300K, Upper heating wall: 374.15 K ,Lower heating wall :374.15K (for bubbly flow)
initial liquid fraction is 1 and vapor fraction is 0.

I have got the vapor and liquid volume fractions for bubbly and semi slug flow which are increasing and decreasing with time respectively.

but when I plot these fractions along the length of computational domain...they are showing huge fluctuation.

Secondly, I need to calculate the vapor quality. I am confused about calculating it.

in Some articles ,it has been calculated using mass flow rates .

whereas in others, it is calculated based on enthalpy formula.

in post CFD, the values of mass flow rates are in -ve ...should I consider -ve sign while calculating...
and similarly enthalpy values are also in -negative.

please help me with calculation of vapor quality

Thanks

[Rob]

Some images will help with the volume fraction question. 

Please define what you want to check for vapour quality: quantity is usually enough for most models. Mass leaving the domain is always negative, enthalpy is a function of temperature, reference temperature & phase.