Evaporation and Condensation in Plate Heat Exchangers with functionalized microstructured Surfaces resulting from a Femtosecond Laser Process

• Applicants: Dr. Thomas Gimpel; Professor Dr.-Ing. Stephan Kabelac
• Subject Area: Technical Thermodynamics ; Chemical and Thermal Process Engineering
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450502853

In this project, a basic understanding of the impact of specially laser-treated metal surfaces on their thermohydraulic performance and the beneficial application of these surfaces in evaporation and condensation shall be developed. Irradiation of surfaces with femtosecond laser pulses result, on one side, in new geometric structures in the nano- or micrometer range and, on the other side, in manipulated wetting behaviour due to the incorporation of appropriate atoms into the solid surface. These functionalized surfaces are created by having an adapted ambient during the laser treatment. These features are expected to give an improved bubble nucleation and an enhanced heat flux during evaporation, and an improved droplet nucleation and drainage during condensation.The Gimpel-group operates two femtosecond-laser devices at the TU Clausthal. The group shall explore in this project the dependencies between the laser operating parameters and the resulting microstructures on the metallic samples made of steel and titanium. They create a whole series of different samples. The Kabelac-group at the Leibniz University of Hannover evaluates a selection of these samples in two special heat transfer devices on behalf of their thermal performance. A preselection of these samples is done by characterizing their wetting behaviour and by optical analysis of their microstructured surfaces. Towards the end of the project, two selected functionalized surfaces are selected to be included in a plate heat exchanger condenser and evaporator, which will be part of a technical refrigeration cycle. It is expected that these heat exchangers show a significantly improved performance and give rise to an enhanced efficiency in many applications within energy and chemical technology.

• DFG Programme: Research Grants
• Major Instrumentation: Kontaktwinkelmessgerät
• Instrumentation Group: 1650 Oberflächen-Spannungsmesser