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In the current numerical study, the thermal and flow field performance of an array of confined multiple jets with air, water, and water‐Al2O3 nanofluid in the maximum crossflow configuration over the target plate with and without pin fins is investigated. The numerical results are validated with the experimental data; it is found that a reasonable prediction related to heat transfer can be made. For this study, steady‐ state Reynolds‐averaged Navier‐Stokes simulations with the shear‐stress transport k‐ω turbulence model in ANSYS Fluent were performed. The simulations are performed with volumetric concentration ϕ = 0.2% to 3% and the jet's Reynolds number Re = 15 000 to 35 000. In all cases, the jet outlet‐to‐target plate distance Z D/ is 3. It is found that the increase in values of the volumetric concentration of nanoparticles results in a decrease of the Nusselt number and an increase of the convective heat transfer coefficient. This is because there is an increase in thermal conductivity of the working fluid with the increase in the volumetric concentration of nanoparticles for the same Reynolds number. About 81.5% and 89.1% enhancement in the average heat transfer flux values is observed for flat and pin fin‐roughened target plates, respectively, for ϕ = 3%. [ABSTRACT FROM AUTHOR]

To commercialize large‐scale and high‐density microalgae cultivation, a 10L cross‐flow flat‐plate airlift photobioreactor (CFA‐PBR) was designed and amplified to two types of 40L CFA‐PBRs via different scaling‐up methods. The multiphase flow characteristics and bioreaction process of these CFA‐PBRs were studied by experiments and computational fluid dynamics (CFD) simulation. The results show that the parameters of CFA‐PBRs, such as bubble size, gas holdup, mass transfer, and photosynthetic reaction efficiency, mainly conform to the principle of geometric similarity under the same light thickness and superficial gas velocity, which is significant for large‐scale industrial applications of the efficient high‐density algae cultivation. [ABSTRACT FROM AUTHOR]

Based on the Tesla‐type turbomachinery principle of operation, a fan consisting of flat, round discs arranged in between two separate channels, which generate two air flows in opposite directions, is investigated. Simulations of a model with one disc as well as a five‐channel model at different grids were performed. With almost unthrottled operation, secondary flows could be determined at velocity magnitudes of up to 20 % of the mean main flow velocity, with secondary currents reaching up to 50 % in throttled operation. Besides high dissipation and recirculation, these secondary currencies are found to be capable of reducing the overall efficiency of the system. Thus, topic of further investigations is the potential of increasing efficiency by means of straighteners and geometric adaptions. [ABSTRACT FROM AUTHOR]