Two-phase flow
 

I am trying to create subcooled flow boiling through a duct under the influence of gravity in transient condition , so as to determine the impact of temperature gradient on the walls. the problem is that i couldn't get a proper temperature rise in fluid. fluid flows at a constant temperature till close to the outlet and then there is a sudden change in temperature ( ie the phase change the is supposed to occur gradually is taking place suddenly at the exit) can anyone help me ??

Am using Eulerian model, RPI boiling

I am not sure how helpful this will be for you, but I had a problem where I was getting a sudden change in temperature (and density) at a boundary condition in a RANS analysis. We determined that it was most likely an improperly defined operating condition that wasn't realistic. This caused some sort of conflict between the turbulence model near wall approximations and the boundary condition. Once I fixed my operating condition I didn't have any problems.