[malekan.cfd]

Dear All,

There is a double pipe heat exchanger that I want to model using Fluent. Outer pipe contains hot water, while inner pipe contains r134a (initially as liquid, then as gas by receiving heat from hot water). I know we can use VoF and evaporation-condensation option to model r134a, but how can I include outer pipe (containing hot water) into the model?

When I activate VoF, it allows me to choose between phase 1 & 2, or their mixture to assign the material for different parts of the problem, don't know how to include hot water for the outer tube.

Any help would be appreciated.

Malekan

[malekan.cfd]

Can I use a udf to change material properties of the inner tube with temperature, something like this:

DEFINE_PROPERTY(thermal_conductivity,cell,thread)
{
real tc, T;
T = C_T(cell,thread);

if(T =< 300)
tc = 1;
else
tc = 2;

return tc;
}

Using this udf for all material properties related to the inner tube, instead of using multiphase model of Fluent. Is it feasible and results in reliable solution?

Malekan