NUCLEATE BOILING REGIME

As demonstrated in the literature, the nucleate boiling is said to begin for heat fluxes higher than 5000 W/m2. This is manifested by a sudden decrease in temperature after having remained constant, for a certain range of heat flux, as shown in the pool boiling curve for propane (Figure 3 presented in 'BIBLIOGRAPHIC RESEARCH - Boiling Regime').

Diphasic simulations were launched using Neptune_CFD with the same mesh as the monophasic simulation at first. As the nucleate boiling model was activated, the values of the wall temperature and different heat fluxes were provided by Neptune CFD by doing small modifications in the FORTRAN files defined in ‘SRC’ directory.

It should be remarked that there are some compromises to be considered, when defining the quality of mesh, between the average wall temperature, average wall heat fluxes, size of the wall adjacent cells and time of simulation. Besides, the ability of Neptune CFD to provide reliable results for boiling regime with high gas volume fraction, due to some difficulties in convergence of the solution, will be discussed in the 'Discussion' section.