The liquid flow and conjugated heat transfer performance of single-phase laminar flow in rectangular microchannels equipped with longitudinal vortex generators (LVGs) are numerically investigated. Deionized-water with temperature-dependent thermo-physical properties is employed to conduct the simulations. Three dimensional simulations are performed using an open-source flow solver based on finite volume approach and SIMPLEC algorithm. Five different configurations of the microchannel with different angles of attack of the LVGs are considered. Simulation results are compared with available experimental data and a deviation below 10% is achieved. The results show that there is a 2-25% increase in the Nusselt number for microchannels with LVGs, while the friction factor increased by 4-30%, for Reynolds number ranged from 100 to 1100. Except one at Re=100, the overall performance of the all configurations of microchannels with LVGs is higher than one.
Highlights• Temperature-depended thermo-physical properties is used to improve the numerical results.• Thermo-hydraulic performance of the microchannels with LVGs is studied in details.• Higher heat transfer enhancement is observed at higher Reynolds numbers.• Microchannels with LVGs cause higher pressure loss in the device.• The overall efficiency of the microchannels with LVGs is calculated.
Conjugated heat transfer and hydraulic performance for nanofluid flow in a rectangular microchannel heat sink with longitudinal vortex generators (LVGs) are numerically investigated using a finite-volume approach at different ranges of Reynolds numbers. Steadystate three-dimensional simulations are performed on a microchannel heated by a constant heat flux with a hydraulic diameter of 160 μm and six pairs of LVGs using a single-phase model. Coolants are selected to be nanofluids containing low volume-fractions (0.5%-3.0%) of Al2O3 or CuO nanoparticles with different particle sizes dispersed in pure water. The proposed model is validated and compared by already-published experimental, and single-phase and two-phase numerical data for various geometries and nanoparticle sizes. The comparison of results obtained from proposed single-phase model and two-phase model favours the former. The results demonstrate that heat transfer is enhanced by 2.29-30.63% and 9.44%-53.06% for water-Al2O3 and water-CuO nanofluids, respectively, in expense of increasing the pressure drop with respect to pure-water by 3.49%-16.85% and 6.5%-17.70%, respectively. We have also observed that the overall efficiency is improved by 2.55%-29.05% and 9.78%-50.64% for water-Al2O3 and water-CuO nanofluids, respectively. The results are also analyzed in terms of entropy generation, leading to the important conclusion that using nanofluids as the working fluid could reduce the irreversibility level in the rectangular microchannel heat sinks with LVGs. No exterma (minimum) is found for total entropy generation for the ranges of parameters studied.
Molten metal melt pools are characterised by highly non-linear responses, which are very sensitive to imposed boundary conditions. Temporal and spatial variations in the energy flux distribution are often neglected in numerical simulations of melt pool behaviour. Additionally, thermo-physical properties of materials are commonly changed to achieve agreement between predicted melt-pool shape and experimental post-solidification macrograph. Focusing on laser spot melting in conduction mode, we investigated the influence of dynamically adjusted energy flux distribution and changing thermo-physical material properties on melt pool oscillatory behaviour using both deformable and non-deformable assumptions for the gas-metal interface. Our results demonstrate that adjusting the absorbed energy flux affects the oscillatory fluid flow behaviour in the melt pool and consequently the predicted melt-pool shape and size. We also show that changing the thermo-physical material properties artificially or using a non-deformable surface assumption lead to significant differences in melt pool oscillatory behaviour compared to the cases in which these assumptions are not made.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.