The influence of liquid viscosity and system pressure on stagnation point vapour thickness during forced-convection film boiling

Abstract

The theoretical model of forced-convection film boiling in the stagnation point region of an axisymmetrical particle is demonstrated. Due to the ‘lubrication effect’ of the laminar vapour flow around the hot particle the liquid flow is slightly perturbed from the frictionless flow. This perturbation depends upon particle surface, free-stream and saturation temperatures. The effect of vapour velocity from the interface, towards the hot surface, on the heat flux conducted from the particle is taken into account. An attempt has been made to include the influence of the system pressure on the phenomenon—so the presented model can be utilized in the description of the coarse premixing phase during vapour (thermal) explosion. The applicability of the model to the calculation of vapour layer thickness in the stagnation point of the sphere and also of heat fluxes at the interface and at the hot surface (the important parameters which influence stability and film boiling collapse) is shown.