Bestimmung von Wärmeübergangskoeffizienten mit Hilfe des Wilson‐Plot‐Verfahrens

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.     

Experimentelle Bestimmung von Wärmeübergang und Druckverlust in Multiportflachrohren

Heat transfer and pressure drop data of three smooth multiport minichannels featuring hydraulic diameters > 1 mm are presented. Experiments were conducted under single phase convection of heptane and under convection of condensing R134a. Two specifically designed testing facilities feature a novel measurement setup to register the amount of condensate generated and to measure the temperatures of the refrigerant and minichannel wall. The results for the smallest minichannel geometrie show that the assumption of an increasing heat transfer rate with decrasing hydraulic diameter is not generally valid.