When a slug has been displaced from its normal position the thickness of the water film is decreased over part of the surface, and higher temperatures may be expected where the film is thin. The experimental data necessary for an exact calculation is incomplete, but some approximate estimates ae made here with special assumption concerning the heat transfer coefficient h as a function of the angle p from the point where the water film is thinnest. Variation in water bulk temperature around the annulus due to poor mixing is not considered here.