[mrmoodmechanic]

problem: The rectangular tank made up of copper is filled with liquid nitrogen with the help of copper tube, there is no flow (i.e. the liquid nitrogen is completely filled )
ambient temperature = 300k
how much time the liquid nitrogen take to come at normal temperature? ( I think its a two phase simulation)
how to do the simulation in ansys?

[vinerm]

To me it does not really look like a CFD problem (or even a flow problem) until you consider that there is some kind of flow, such as because of evaporation. As long as is liquid, it has to heat up by gaining some energy. Once it reaches evaporation point, it has to gain latent heat and evaporate. Once evaporated, it begins to heat up further. Evaporation part is straightforward since heat required is given by

q1 = mL, m being mass of and L being its heat of evaporation. First and last part are easy if it is assumed that liquid and vapor are well-mixed because then it is as simple as

q2 =

and q has to be supplied from the environment, therefore,

q1 + q2 =

It all boils down to knowing value of heat supply rate from the outside. Divide heat required by heat supply rate and you get time required. In practice, radiation plays a very important role in heating cryogenic liquids, that's why flasks are double-walled. And liquid and vapor are never well-mixed. Vapor has to be treated as ideal gas otherwise you can't contain vapor, which has a far lower density than liquid, in the same volume. If you wish to carry out CFD, you have to use VOF model with mass transfer or E-C model in Fluent.