https://jmnr.sku.ac.ir/ Journal of Microfluidic and Nanofluidic Research en daily 1 Mon, 01 Dec 2025 00:00:00 +0330 Mon, 01 Dec 2025 00:00:00 +0330 https://jmnr.sku.ac.ir/article_116665.html The progressive miniaturization of electronic components alongside escalating power densities has generated unprecedented thermal management challenges, with heat flux values attaining 10⁴ W/cm² in specialized applications. Microchannel heat sinks (MCHSs) have established themselves as a highly effective cooling solution owing to their exceptional heat dissipation capacity and favorable surface-area-to-volume characteristics. This review synthesizes findings from previous investigations, encompassing heat transfer enhancement approaches, including rib structures, cavity configurations, pin-fin arrays, and biomimetic designs, advanced working fluids, flow instability phenomena, machine learning implementations, and multi-objective optimization strategies. https://jmnr.sku.ac.ir/article_116669.html Microcyclones are fluid separation devices that utilize centrifugal forces generated by tangential fluid injection to remove fine particles from gas or liquid streams. This review synthesizes recent advances in microcyclone fundamentals, performance enhancement strategies, and applications. Electrostatic field integration improved collection efficiency from 88.3% to 96.2% for fly ash and from 46.2% to 99.1% for submicron pollen. Stereolithographic 3D printing enabled minimum channel dimensions of 0.75 mm and cut diameters as low as 0.05 μm at 5 L/min with fabrication costs of approximately $10 per device. Optimized geometries achieved classification precision of 95.94% and efficiency of 72.89% for 25 μm silica particles. Miniature hydrocyclones demonstrated 99.98% oil-water separation efficiency at 1 L/min, while virtual cyclones reduced cut-off diameters by 38.6% with only 7.3% pressure drop increase. Openable cyclone designs achieved sampling yields 1.3 times higher than unopenable alternatives. Persistent challenges include particle entrainment, clogging susceptibility, and non-linear pressure drop versus cut-size relationships. Future directions focus on device integration, refined turbulence models, and emerging applications in aerovirology and personalized air monitoring https://jmnr.sku.ac.ir/article_116681.html This study experimentally investigates the thermal-hydraulic performance of alternating flattened tubes in a double-pipe heat exchanger. The primary objective is to evaluate the effects of geometric modifications, including pitch length and degree of flattening, on heat transfer enhancement and pressure drop compared to conventional circular tubes. Four tube configurations were examined: alternating flattened tubes with pitch lengths of 12 cm and 28 cm (flattening of 1 cm), a completely flattened tube (100 cm pitch length, 1 cm flattening), and an alternating flattened tube with a higher flattening degree of 1.2 cm (pitch length 12 cm). Experiments were conducted over a range of Reynolds numbers, and the Nusselt number and pressure drop were measured and analyzedc. The results demonstrate that alternating flattened tubes significantly improve heat transfer compared to circular tubes. The AF_12_1 tube (12 cm pitch, 1 cm flattening) exhibited the highest Nusselt number, achieving 1.9 times that of the circular tube. However, this enhancement was accompanied by an increase in pressure drop, which was 1.22 times higher than the circular tube at higher Reynolds numbers. Increasing the pitch length or reducing the degree of flattening decreased both heat transfer and pressure drop. The completely flattened tube showed a more modest improvement (1.33 times the Nusselt number) with the lowest pressure drop increase. Overall, the alternating flattened tube with shorter pitch length and moderate flattening provides the best thermal performance at the cost of higher flow resistance. https://jmnr.sku.ac.ir/article_116723.html Nanofibrous structures are widely used in filtration, membrane separation, protective materials, biomedical systems, and other transport-related applications. Numerical simulation of flow and transport phenomena in such media requires a reliable geometrical representation of the fibrous domain. However, generating controlled fibrous geometries, particularly random and disordered structures with prescribed fiber diameter, orientation, and density, remains a challenging and time-consuming step in computational modeling. In this study, a MATLAB-based computational code coupled with COMSOL Multiphysics through Live-Link is developed to generate micro/nanofibrous structures inside a cylindrical computational domain. The proposed framework enables the construction of a single fiber with arbitrary dimensions, arrays of parallel fibers, fibers with prescribed orientations, and fully random fibrous networks. The code allows independent control over key structural parameters, including fiber diameter, fiber number, fiber density, orientation, spatial distribution, and computational domain size. Moreover, fibrous structures can be generated using uniform or non-uniform fiber diameters, making the method suitable for representing both idealized and more realistic fibrous media. The generated geometries can be directly used in COMSOL Multiphysics as initial computational domains for the simulation of fluid flow, pressure drop, permeability, particle transport, and other coupled physical phenomena. The developed MATLAB–COMSOL Live-Link framework provides a flexible and efficient tool for rapidly constructing parametric fibrous geometries and systematically studying the effect of microstructural parameters on transport behavior in fibrous media. This approach can facilitate the design, optimization, and numerical analysis of micro/nanofibrous materials in filtration and related applications.