Hello
I am working on a model that simulates a heated pipe with water flow inside it. I need the temperature field on the outer surface of the pipe as a function of time, therefore i made a multiscale CHT model. Since the pipe is heated to over 600K i am also using the transition boiling model to capture the vapor layer that will form next to the wall.
What i am unsure of is how to ensure correct heat transfer between the fluid and the solid region when I have this thin vapor layer. I read in the manuals that the energy coupling is achieved using an explicit mapped contact interface where the Boundary Heat Flux and by default the Specified Y+ Heat Transfer Coefficient at Y+ = 100 are exchanged across the interface. So the reference temperature depends on the chosen Y+ value.
I am assuming that the Y+ value has to be chosen to be inside the vapor layer, yet where in the vapor layer seems quite arbitrary to me.
I tried using the local heat transfer coefficient that uses the wall-cell HTC, but it resulted in nearly no change to the temperature of the solid region.
So my question is: how does one ensure that the chosen Y+ value is correct and takes into account the vapor layer?
And are there other better methods to achieve this energy coupling?
Thank you in advance