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A better understanding of the mechanics of condensation is needed to devise active bioaerosol samplers. Here, dropwise water condensation produced by directing humid air flow perpendicularly on ambient (25 °C) and cooled (4 °C) copper plate substrates was studied. Numerical data obtained from solving the two-dimensional incompressible Navier–Stokes equations with low Reynolds numbers (=40) showed significant vorticity strength developing at the edges of the copper plate. This resulted in a higher degree of aerosol deposition and an increased likelihood of drop nucleation at the impaction zone. When a drop is already present at the edge, simulations predicted that the high vorticity region shifted to the apexes of drops with concomitant increase in the magnitude of vorticity strength. These results explained the experimentally observed dropwise condensation of larger drops at the edges of the ambient substrate. Analyses of drop size distributions at the center and edges of ambient and cooled substrates showed that drop growth was enhanced by improved condensation on the cooled substrate surface in addition to the flow vorticity effect. Preliminary findings indicate that the recovery of viable aerosolized Escherichia coli from ambient and cooled substrate was found to be invariant, portending its utility for sampling when the electrical power available for cooling is limited. Copyright © 2023 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Nowadays, impinging jets are of great importance in cooling of electronic constituents which have decreasing heat transfer area with miniaturization and hence have extremely high heat fluxes. In this study, improvement of the cooling of microchips that are also used in computers and have a quite high amount of heat generation has been researched. For this aim, cooling of copper plate surfaces having 1000 W/m2 constant heat flux and two different patterns that are rampart and rectangular shapes by using a single air jet flow in channels whose cross-section is rectangle and having three sides closed and one side open has been investigated. Numerical investigation has been performed steady and 3D energy and Navier-Stokes equations by implementing computer program of Ansys-Fluent with k-e turbulance model. While the upper and lower surfaces of the channel whose cross-section is rectangle are adiabatic, constant heat flux has been applied to the surfaces of rampart and rectangle. The used jet fluid is air and the temperature of inlet air is 300 K. The range of Re for the study is 4000-10000 when the evaluated interval between the jet-plate (H/Dh) is 4-10. The acquired results have been matched with the numerical and experimental conclusions of the study in the literature and they have been found to be compatible with each other. The results have been presented as the average Nu number and the surface temperature variation for each patterned surface with the rampart and rectangle shape. The temperature, velocity and streamline contour distributions of the jet flow along the channel for different H/Dh ratios and Re numbers have been evaluated for ramparts and rectangular pattern surfaces. In the work, the values of the mean Nu number, surface temperature and outlet jet flow temperature from the channel have been also analyzed for all surfaces in both patterned geometries. A higher average Nu number value of 31.45% has been obtained for rectangle patterned surfaces according to rampart patterned surfaces for Re=4000 and H/Dh=4. [ABSTRACT FROM AUTHOR]