Consider a horizontal cylinder with L/D = large. Imagine this cylinder is filled with a liquid to different levels (consider cases where it is 10, 20, 50, 70, 90% full, note that liquid level is horizontal.). Divide the wall area not covered by liquid into 10 equal axial strips. Determine the view factor from any axial strip on the cylinder wall to the liquid surface (use crossed strings method). Also determine the view factor from strip to strip.
Use symmetry where possible to determine factors. Plot as a function of fill level. What are the limitations of the crossed strings here?