Numerical simulation of dropwise condensation over hydrophobic surfaces using vapor-diffusion model

Dropwise condensation of humid air over hydrophilic and hydrophobic surfaces is numerically investigated using a phenomenological, Lagrangian model. Mass flux through droplets free surface is predicted via a vapor-diffusion model. Validation with literature experimental data is successfully conducted at different air humidities and air velocities. The accuracy of the implemented condensation model is compared with a standard analogy between convective heat and mass transfer, showing that the latter is not able to predict heat transfer performances in the investigated air velocity range.

A simple vapor-diffusion method enables protein crystallization inside the HARE serial crystallography chip

Fixed-target serial crystallography has become an important method for the study of protein structure and dynamics at synchrotrons and X-ray free-electron lasers. However, sample homogeneity, consumption and the physical stress on samples remain major challenges for these high-throughput experiments, which depend on high-quality protein microcrystals. The batch crystallization procedures that are typically applied require time- and sample-intensive screening and optimization. Here, a simple protein crystallization method inside the features of the HARE serial crystallography chips is reported that circumvents batch crystallization and allows the direct transfer of canonical vapor-diffusion conditions to in-chip crystallization. Based on conventional hanging-drop vapor-diffusion experiments, the crystallization solution is distributed into the wells of the HARE chip and equilibrated against a reservoir with mother liquor. Using this simple method, high-quality microcrystals were generated with sufficient density for the structure determination of four different proteins. A new protein variant was crystallized using the protein concentrations encountered during canonical crystallization experiments, enabling structure determination from ∼55 µg of protein. Additionally, structure determination from intracellular crystals grown in insect cells cultured directly in the features of the HARE chips is demonstrated. In cellulo crystallization represents a comparatively unexplored space in crystallization, especially for proteins that are resistant to crystallization using conventional techniques, and eliminates any need for laborious protein purification. This in-chip technique avoids harvesting the sensitive crystals or any further physical handling of the crystal-containing cells. These proof-of-principle experiments indicate the potential of this method to become a simple alternative to batch crystallization approaches and also as a convenient extension to canonical crystallization screens.

The Influence of Vapor Attachment Kinetics on Snow Effective Properties

<p>Proper modelling of heat and mass transfer in snow is a prerequisite for understanding snow metamorphism and simulating the mass and energy budget of a snowpack and the underlying ground. The transfer of heat and water vapor in snow can be described with macroscopic conservation equations, which include effective coefficients such as the snow thermal conductivity or the snow water vapor diffusion coefficient. Here, we investigate the impact of the surface kinetics of water vapor sublimation and deposition at the microscopic scale on these macroscopic equations, restraining ourselves to the limiting cases of slow and fast kinetics. In particular, we show that under the assumption of fast kinetics the thermal behavior of snow is similar to that of a regular inert medium, but with an enhanced conduction in the pores, due to latent heat transported with water vapor. Besides, faster kinetics increases the effective water vapor diffusion coefficient, which nonetheless remains less than that in free air. M<span>ost (but not all) available experimental investigations suggest that in snow, fast surface kinetics prevails, so that our results have numerous implications for the proper simulation of heat and mass transfer in snow.</span></p>

Components of apparent soil thermal conductivity measured by the heat pulse method

<p>Knowledge on the components of apparent soil thermal conductivity (λ) across various water contents (θ) and temperatures is important to accurately understand soil heat transfer mechanisms. In this study, soil thermal conductivity was measured for sandy loam and silty clay soils at various temperatures and air pressures using a transient method. Four components of λ, namely, heat conduction, latent heat transfer by water vapor diffusion, sensible heat transfer by liquid water, and sensible heat transfer by water vapor diffusion were quantified. Results showed that in uniform soils, the magnitudes of sensible heat transfers by liquid water and water vapor were negligible during these transient measurements. The contribution of latent heat transfer through vapor diffusion to total heat transfer increased as temperature increased, and the peak value occurred at an intermediate water content. The water content at which the maximum vapor diffusion occurred varied with soil texture. In addition to the four calculated components, a significant residual contribution to λ caused by an unidentified vapor transfer mechanism was observed between 3.5°C and 81°C. For example, calculations indicated that approximately 66% of the sandy loam λ at θ=0.11 m<sup>3</sup> m<sup>−3</sup> was caused by an unidentified vapor transfer mechanism at 81°C. This extra contribution by vapor transfer could be explained either as enhanced vapor diffusion or by an advection mechanism. Further investigation is needed to clarify whether enhanced diffusion or advection is occurring in unsaturated soils. </p>

Macro-Scale Numerical Simulation of Moisture Transmission in Zeoli-Based Moisture Conditioning Material

By random growth method, this paper constructs isotropic porous media, anisotropic-1 porous media, and anisotropic-2 porous media, which have the same porosity but different micropore morphologies, and explores how the pore morphology affects the water vapor diffusion in the pores of porous media. The results show that: the random growth method can effectively reconstruct various porous moisture conditioning materials, and control their porosity and pore morphology; the equilibrium water vapor concentration and stabilization time of water vapor diffusion can effectively demonstrate the pore connectivity of porous media and the dynamic migration features of materials in the pores; the greater the change in the equilibrium water vapor concentration, the faster the stabilization of water vapor diffusion, and the better the pore connectivity of porous media.