Rupp Ariana I K S, Gruber Petra
Department of Biology, Biomimicry Research and Innovation Center, The University of Akron, Akron, OH 44325, United States of America.
Myers School of Art and Department of Biology, Biomimicry Research and Innovation Center, The University of Akron, Akron, OH 44325, United States of America.
Bioinspir Biomim. 2021 Jun 4;16(4). doi: 10.1088/1748-3190/abdd9e.
Evaporative interfaces help process heat and substances in a variety of technical realms, from electronic to architectural applications. Because geometry affects the hydraulics, thermal properties and aerodynamics of evaporative devices, their performance can be tuned through design. While non-smooth interfaces are widely exploited to enhance transfer passively, surface area extension in packed volumes is a predominant line of research. This leaves aerodynamic structure-transfer relations and the impact of geometry itself unclear. Meanwhile, protrusions in leaves such as lobes and toothed margins have been associated with enhanced vapor dissipation. This experimental study explores the design space of leaf-inspired structures with evaporating protrusions. Three sets of water-absorbing models with fixed evaporating surface area and unlimited hydraulic supply were tested: (1) paper strips with dimension-equivalent protrusions of varied shape and degree of elongation; (2) cellulose sponges with the same designs as their cross-sectional profile, extruded three-dimensionally; (3) ceramic tiles with grooves of varied cross-section, conceived as building elements for evaporative cooling. Overall, results demonstrate that protrusions affect mass transfer rate and surface temperatures and can be integrated in the design of evaporative exchangers with non-smooth geometries. For the paper models, evaporation rate correlated with protrusion aspect ratio, supporting a functional interpretation of leaf design and its utilization in low-wind plate-fin exchangers. However, the same transfer enhancement was not regained from simply extruding an effective design into three-dimensions. For the ceramic tiles, geometry-driven differences in evaporation depended on the aerodynamic roughness and size of the grooved pattern, and on ventilation. Their outdoor thermal behavior was complex due to a multifaceted interaction with the environment and geometry-related factors such as self-shading and thermal mass. Ultimately, this design effort illustrates the potential of structured interfaces for evaporative exchange and thermoregulating the built environment.
蒸发界面有助于在从电子到建筑应用等各种技术领域中处理热量和物质。由于几何形状会影响蒸发设备的水力学、热性能和空气动力学，因此可以通过设计来调整其性能。虽然非光滑界面被广泛用于被动增强传递，但在紧凑空间中扩展表面积是一个主要的研究方向。这使得空气动力学结构-传递关系以及几何形状本身的影响尚不清楚。与此同时，叶片上的凸起，如裂片和锯齿状边缘，与增强的蒸汽消散有关。本实验研究探索了具有蒸发凸起的叶片启发结构的设计空间。测试了三组具有固定蒸发表面积和无限水力供应的吸水模型：（1）具有不同形状和伸长程度的尺寸等效凸起的纸条；（2）具有与其横截面轮廓相同设计的纤维素海绵，三维挤压成型；（3）具有不同横截面凹槽的瓷砖，被设想为用于蒸发冷却的建筑元件。总体而言，结果表明，凸起会影响传质速率和表面温度，并且可以集成到具有非光滑几何形状的蒸发交换器设计中。对于纸质模型，蒸发速率与凸起的纵横比相关，支持了叶片设计的功能解释及其在低风速板翅式交换器中的应用。然而，仅仅将有效的设计三维挤出并不能恢复相同的传递增强效果。对于瓷砖，蒸发中几何形状驱动的差异取决于凹槽图案的空气动力学粗糙度和尺寸以及通风情况。由于与环境以及诸如自遮阳和热质量等几何相关因素的多方面相互作用，它们在室外的热行为很复杂。最终，这项设计工作说明了结构化界面在蒸发交换和调节建筑环境温度方面的潜力。
