AbstractThe original method employed by Wilson to eliminate the use of thermocouples embedded in the tube wall in evaluating the heat‐transfer coefficient of the condensing vapours is not fundamentally sound. A modified method on a more rigorous basis is presented.It has been demonstrated theoretically that the heat‐transfer coefficient of a condensing vapour is a function of rate of heat only. The proposed method consists in varying the rate of flow of cooling water inside the condensing tube and the over‐all temperature difference to obtain the heat‐transfer coefficients at a constant rate of heat‐transfer. The over‐all temperature drop is varied by changing the pressure in the vapour space. The film coefficient is then calculated from the intercept of a plot of δ T/q against 1/(1 + 0.011t) V0.8.The heat‐transfer coefficients of trichloroethylene, bromobenzene, nitromethane and n‐hexyl alcohol have been experimentally determined by the proposed method. The theory of the method was confirmed by plotting h0 against q; the slope was equal to‐1/3.The heat‐transfer coefficients predicted from Nusselt's equation agreed with those determined experimentally for trichloroethylene and bromobenzene, but not with those for nitromethane and n‐hexyl alcohol.