  A theoretical model is developed for the forced convection film boiling
phenomenon over a heated sphere moving vertically downwards in the water.
Unprecedented to the previous analytical studies, this model accounts for the
buoyancy effects while solving the momentum, and energy equations in the vapor
phase to obtain the velocity, and the temperature distribution in terms of the
vapor boundary layer thickness. To calculate the vapor boundary layer thickness
an energy balance is applied at the vapor-liquid interface. The flow of liquid
around the sphere is considered to be governed by the potential theory, and the
energy equation in liquid is then solved for the known velocity distribution.
We find that the vapor boundary layer thickness increases with an increase in
the sphere, and the bulk water temperature, and a decrease in the free stream
velocity. This further results in a decrease in the film boiling heat transfer
coefficient. The present study concludes that at low free stream velocities ($<
0.5$ m/s) buoyancy becomes significant in delaying the separation, and when the
velocity is further reduced the separation angle approaches $180^{\circ}$.
