In order to achieve a sustainable reduction in CO2 emissions, industrial processes must be designed in an energy-conscious and efficient manner. One process with enormous energy-saving potential is falling film evaporation. Falling film evaporation is characterized by very good heat transfer with short residence times. For an efficient process design, a thin film evenly distributed around the entire surface is necessary. Deviations from the vertical tube orientation often result in efficiency-reducing film break-ups. These can be avoided by structuring the evaporator surface. Propane is suitable as a heat transfer medium due to its ecological, thermodynamic and physical properties. Within the scope of this work, extensive investigations were carried out on the heat transfer and film stability of a propane falling film in internally structured evaporator tubes (Cu- DHP). In addition to the structure (1x smooth tube, 4x helical structures, 1x longitudinal structure), the main aspects of investigation were the influence of tube inclination (0° to 20° from the vertical), temperature, temperature difference and mass flow rate. The test facility was specially designed and built for these investigations. It was shown that the structuring of the evaporator surface leads to an improvement in film stability and heat transfer. Especially the helical structures favor a tangential distribution of the liquid and thus promote the formation of thin liquid films that wet the entire tube circumference. The groove height has proved to be the main geometric influencing parameter. Overflowing of the structures leads on the one hand to an increase in film thickness, which is inhibiting heat transfer, but on the other hand this promotes turbulence and leads to an improvement in heat transfer. Furthermore, a positive effect of the tube inclination on the heat transfer could be shown. The investigations also revealed the influence of groove transport capacity and shear stress on film stability and heat transfer.weiterlesen