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

在本项目中，应了解特殊激光处理的金属表面对其热工水力性能的影响以及这些表面在蒸发和冷凝中的有益应用。用飞秒激光脉冲照射表面，一方面导致纳米或微米范围内的新几何结构，另一方面由于将适当的原子掺入固体表面而导致操纵润湿行为。这些功能化表面通过在激光处理期间具有适应的环境而产生。预计这些功能将在蒸发过程中提供更好的气泡成核和增强的热通量，并在冷凝过程中改善液滴成核和排水。Gimpel组在TU Clausthal操作两个飞秒激光设备。该小组将在该项目中探索激光操作参数与钢和钛制成的金属样品的显微结构之间的依赖关系。他们创造了一系列不同的样本。汉诺威莱布尼茨大学的Kabelac小组在两种特殊的传热装置中评估了这些样品的热性能。这些样品的预选是通过表征它们的润湿行为和它们的微结构化表面的光学分析来完成的。在项目结束时，两个选定的功能化表面被选择用于板式换热器冷凝器和蒸发器，这将是技术制冷循环的一部分。预计这些热交换器显示出显著改善的性能，并在能源和化学技术的许多应用中提高效率。

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.