Heat transfer mechanisms in vapor mushroom region of saturated nucleate pool boiling

To reveal the highly efficient heat transfer mechanisms in the vapor mushroom region of saturated nucleate pool boiling, a new model was developed in which three heat transfer mechanisms were considered: the conduction and evaporation in the microlayer region underneath vapor stem, the conduction and evaporation in the macrolayer region between the vapor mushroom and the heater surface and Marangoni convection in the macrolayer region. Two-dimensional conservation equations for laminar flow in the macrolayer region and conduction in the heater were solved. The SIMPLE-algorithm was used for handling the pressure–velocity coupling. Calculated boiling curve agrees well with the published experimental data and numerical results showed that about 60% heat flux is transferred by evaporation in the microlayer region, and about 40% heat flux is evaporated at the vapor–liquid interfaces of the macrolayer due to both the conduction and Marangoni convection heat transfer in the macrolayer region. Further investigations were also carried out for the cases in which only one or two heat transfer mechanisms were considered to assess the relative influences of the microlayer evaporation and Marangoni convection.