Learning Forum

[Manish Patel]

I am using Lee evaporation model to simulate saturated pool boiling case for dielectric fluid. I am using constant wall heat flux boundary condition.

When, I am plotting Heat flux vs Wall superheating, I am getting unrealistic too high wall superheating compared to the experimental value.

For example, at heat flux of 200 kW/m2, the wall superheating should be 14 °C, But I am getting around 145°C of superheating.

I know the lee coefficient is sensitive here. I did trial and error with different values ranging from 0.1 to 1000 but, the wall superheating never goes near to 14°C, it is always above 100° (which is unrealistic).

How do I deal with this issue?

[Rob]

The wall is 145C or the liquid is 145C? Remember the wall will heat up until it pushes 200kW/m2 into the fluid, so if there's no flow in that region (ie very low heat transfer into the fluid) the temperature will keep increasing to meet the set flux. 

[Manish Patel]

 

The Wall Temperature (above saturation) is 145°C. Not the liquid temperature. 

Yes, there is no flow in the region since its pool boiling. 

Yes, temperature keeps increasing to meet the set heat flux value. But, Wall adjacent temperature is not much high and realistic value. 

How to solve this issue? Is considering Wall adjacent temeperature is the solution?

 

[Rob]

You need to decide what to monitor, but I'd look at the cell values too. The various wall temperatures are defined in the manual.