The heat transfer coefficient on the service side of a double-pipe heat exchanger is determined with the Wilson-plot method. Condensing hexanol vapor is used as heating medium and water in single phase counter current flow on the product side. In addition to the Wilson-plot, two alternative methods are used for calculating the service side film heat transfer coefficient: the Nusselt theory for film condensation and the extraction from an overall heat transfer coefficient based on an energy balance and employing the Gnielinski equation for the tube side heat transfer. As the result, heat transfer coefficient can be calculated as a function of the transferred heat flux employing the Wilson-plot.