Experimental measurements and CFD evaluation of wall heat flux partitioning during sub-cooled flow boiling of R-11 within vertical annulus - 15379

In this paper we review heat transfer and wall heat flux partitioning applicable to subcooled forced flow nucleate boiling. Subcooled flow boiling experiments were conducted at low pressure for vertical up flow and for a wide range of mass fluxes (435 - 1443 Kg/m²*s) and heat fluxes (4.7 - 31.2 W/cm²), which enabled to study the influence of different boundary conditions on the development of local boiling parameters. The contribution of each of the mechanisms for transfer of heat to the liquid - forced convection and evaporation, as well as the energy transport associated with vapor generation has been quantified in terms of nucleation site densities, bubble departure, bubble detachment frequency, flow parameters like velocity, inlet subcooling and wall superheat. A comparison of the experimented data with predictions from selected models is also included. A good overall agreement between calculated and experimental data from the literature has been obtained. The experimental wall temperatures are reasonably well predicted, the Kurul and Podowski heat partitioning wall boiling model is adequate for the calculation of the wall temperature. By predicting the temperature at the wall surface, critical regions can be identified