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Laser Powder Bed Fusion (LPBF) was utilized to create a series of aluminum alloy (i.e., AlSi10Mg) 5-mm-diameter support pillars with a fixed height of 5 mm containing varying filet angles and build orientations (i.e., 0°, 10°, 20°, 30°, 40°, 50°, and 60° from the normal surface) to determine their effects on surface roughness and water wettability. From experiments, anisotropic wetting was observed due in part to the surface heterogeneity created by the LPBF process. The powder-sourced AlSi10Mg alloy, typically hydrophobic, exhibited primarily hydrophilic behavior for build angles of 0° and 60°, a mix of hydrophobic and hydrophilic behavior at build angles of 10° and 20°, and hydrophobic behavior at 30°, 40°, and 50° build angles. Measured surface roughness, Ra, ranged from 5-36 micrometers and varied based on location. 3D-topography maps were generated and arithmetic mean heights, Sa, of 15.52-21.71 micrometers were observed; the anisotropy of roughness altered the wetting behavior, thereby prompting some hydrophilic behavior. Build angles of 30° and 40° provided for the smoothest surfaces. A significantly rougher surface was found for the 50° build angle. This abnormally high roughness is attributed to the melt pool contact angle having maximal capillarity with the surrounding powder bed. In this study, the critical melt pool contact angle was near-equal to the build angle suggesting a critical build angle exists which gives rise to pronounced melt pool wetting behavior and increased surface roughness due to enhanced wicking followed by solidification.

• Condensation at steam mass fluxes of 35-75 kg/m 2 s and N2 mass fractions of 0-30%. • Nitrogen in hydrophilic channel reduces condensation heat transfer by 24-55%. • Dropwise condensation heat transfer enhancement in hydrophobic channel with N2. • Condensation heat transfer coefficients are a function of vapor mass fraction.

Engineering innovations—including those in heat and mass transfer—are needed to provide food, water, and power to a growing population (i.e., projected to be 9.8 × 109 by 2050) with limited resources. The interweaving of these resources is embodied in the food, energy, and water (FEW) nexus. This review paper focuses on heat and mass transfer applications which involve at least two aspects of the FEW nexus. Energy and water topics include energy extraction of natural gas hydrates and shale gas; power production (e.g., nuclear and solar); power plant cooling (e.g., wet, dry, and hybrid cooling); water desalination and purification; and building energy/water use, including heating, ventilation, air conditioning, and refrigeration technology. Subsequently, this review considers agricultural thermal fluids applications, such as the food and water nexus (e.g., evapotranspiration and evaporation) and the FEW nexus (e.g., greenhouses and food storage, including granaries and freezing/drying). As part of this review, over 100 review papers on thermal and fluid topics relevant to the FEW nexus were tabulated and over 350 research journal articles were discussed. Each section discusses previous research and highlights future opportunities regarding heat and mass transfer research. Several cross-cutting themes emerged from the literature and represent future directions for thermal fluids research: the need for fundamental, thermal fluids knowledge; scaling up from the laboratory to large-scale, integrated systems; increasing economic viability; and increasing efficiency when utilizing resources, especially using waste products.

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