CFD-based numerical investigation of convective heat transfer in multi-channel micro-exchangers using MWCNT–water nanofluid G. Anjaneya, S. Sunil, M. B. Hanamantraygouda, N. K. Manjunatha, K. Ravikiran, C. Solaimuthu, H. Ramesha, S. Harish, B. P. Dileep, C. Durga Prasad, Aymen Adem Scientific Reports, 2026 Efficient cooling is a key factor influencing the performance of compact electronic systems, which requires advanced thermal management. Microchannel Heat Exchangers (MCHEs) are increasingly becoming popular due to their high surface area-to-volume ratio and ability to dissipate high heat flux. The current study aims to explore the performance of MCHEs using a water-based, multiwalled carbon nanotube-blended nanofluid as coolant under different channel counts and geometries. A 3D CFD model was developed in ANSYS Fluent using the finite volume method, assuming constant thermophysical properties and steady-state, laminar flow, with uniform heat flux boundary conditions. An aluminum MCHE of dimensions 45 mm × 45 mm × 7 mm was analyzed with five channel geometries (square, circular, sawtooth, cross, and curved sawtooth) at three channel counts (5, 8, and 11). Two concentrations of multi-walled carbon nanotube (MWCNT)–water nanofluid (0.1 and 0.2%) were considered. Results exhibited that the baseline configuration (Square channel, 5 channels, water as coolant) achieved a convective heat transfer coefficient of 2008.24 W/m²K, overall heat transfer coefficient (U) of 1258.75 W/m²K, and thermal effectiveness (ε) of 0.102. The optimum configuration, curved sawtooth geometry with 5 channels and 0.2% MWCNT nanofluid, yielded h = 8271 W/m²K, U = 6590 W/m²K, and ε = 0.4765. ANOVA analysis confirmed channel geometry as the most influential factor, contributing 70.6% to effectiveness and 78.2% to the overall heat transfer coefficient.
Development and Characterization of Microstructure, Mechanical and Thermal Behavior of AA-2219-Al2O3 MMCs for I. C. Engine Application S. Harish, Shanawaz Patil Results in Chemistry, 2026 Aluminium alloy AA2219 is a high strength alloy known for its great mechanical properties and superior performance at high temperatures. The current study examines the impact of alumina micron particles on the microstructure, tensile stress, elongation, yield stress, hardness, impact strength, thermal conductivity, and thermal expansion of AA2219 reinforced with Al 2 O 3 at weight percentages ranging from 3 to 12 wt% of composites. The convectional and cost-effective stir casting procedure used to create the AA2219-alumina composite. Micro-structure investigation using optical and SEM predicts the production of dendritic structure throughout the AA2219 with alumina composite, as well as the uniform dispersion of ceramic particles in the matrix AA2219 due to the vortex created in the two stages of stir speed 150–300 rpm during casting. It was found that increasing the alumina ceramic particles from 3 to 12 wt% improved mechanical properties by 25–30% while decreasing thermal conductivity by 35.6%. The coefficient of thermal expansion was reduced (26.15%) when the temperature increased from 100 to 500 degrees Celsius and the amount of alumina in the matrix AA2219. The developed AA2219-Alumina composite is recommended for usage in airplane fuselages, fuel tanks, I.C. engine outlet valves, and other high-temperature components.
Hierarchical polymer film for open-air atmospheric water harvesting by all-day radiative cooling Zhizhong Cheng, Yaerim Lee, A. Alperen Günay, Jiang Guo, Sivasankaran Harish, Junichiro Shiomi Cell Reports Physical Science, 2026 Passive radiative cooling coupled with atmospheric water harvesting (PRC-AWH) is a promising energy-saving technique for overcoming water scarcity issues. However, ensuring a 24-h open-air PRC-AWH operation is challenging. Here, we report a scalable, self-cleaning, and flexible polymer film with nano-/microstructured surfaces that achieves continuous open-air PRC-AWH. The film achieves high solar reflectivity (>0.95) and infrared emissivity (>0.99), resulting in an average subcooling of approximately 8°C throughout the day. Controlled environmental testing revealed that the hierarchical structure nucleates, coalesces, and transports water droplets during the condensation process in a superior manner, thereby enhancing water harvesting performance. Outdoor testing showed that the film collects a total of 358 g·m −2 ·d −1 of water from the atmosphere via its single-sided structured surface during daytime under natural weather conditions.
Large Anisotropy of Thermal Conductivity in Oriented Cellulose-Clay Composites Guantong Wang, Lengwan Li, Lilian Medina, Sivasankaran Harish, Jing Liu, Bin Xu, Rulei Guo, Cheng Shao, Takashi Kodama, Lars A. Berglund, Junichiro Shiomi ACS Omega, 2025 High Resolution Image Download MS PowerPoint Slide This study characterized the anisotropic thermal conductivity of clay/cellulose nanocomposites, an eco-friendly functional flame-retardant material exhibiting excellent mechanical properties, gas barrier properties, and biodegradability. Thermal conductivity anisotropy is important for flame-retardant materials. Low thermal conductivity in the through-thickness direction serves as a thermal barrier, whereas high thermal conductivity in the in-plane direction prevents local heat accumulation. We prepared a series of membranes of nanocomposites of montmorillonite clay platelets and cellulose nanofibrils via vacuum filtration/drying and measured their directional thermal conductivities as a function of the montmorillonite clay/cellulose nanofibril content. The results indicate that the through-thickness and in-plane thermal conductivities depend nonmonotonically on the clay content. The highest in-plane thermal conductivity reached 7.5 W m –1 K –1, exhibiting a maximum anisotropy of 30 for a clay content of 50%. Structural investigation via Raman spectroscopy revealed an enhanced planar alignment of the cellulose nanofibrils and indicated alignment of the clay platelets. The correlation between the degree of alignment and thermal conductivity anisotropy suggests that alignment increases the contact area between the cellulose nanofibrils and clay platelets, which enhances in-plane heat conduction by increasing the phonon transport path and impedes through-thickness heat conduction by enhancing phonon boundary scattering.
Enhanced High Thermal Conductivity Cellulose Filaments via Hydrodynamic Focusing Guantong Wang, Masaki Kudo, Kazuho Daicho, Sivasankaran Harish, Bin Xu, Cheng Shao, Yaerim Lee, Yuxuan Liao, Naoto Matsushima, Takashi Kodama, Fredrik Lundell, L. Daniel Söderberg, Tsuguyuki Saito, Junichiro Shiomi Nano Letters, 2022 Nanocellulose is regarded as a green and renewable nanomaterial that has attracted increased attention. In this study, we demonstrate that nanocellulose materials can exhibit high thermal conductivity when their nanofibrils are highly aligned and bonded in the form of filaments. The thermal conductivity of individual filaments, consisting of highly aligned cellulose nanofibrils, fabricated by the flow-focusing method is measured in dried condition using a T-type measurement technique. The maximum thermal conductivity of the nanocellulose filaments obtained is 14.5 W/m-K, which is approximately five times higher than those of cellulose nanopaper and cellulose nanocrystals. Structural investigations suggest that the crystallinity of the filament remarkably influence their thermal conductivity. Smaller diameter filaments with higher crystallinity, that is, more internanofibril hydrogen bonds and less intrananofibril disorder, tend to have higher thermal conductivity. Temperature-dependence measurements also reveal that the filaments exhibit phonon transport at effective dimension between 2D and 3D.
