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This study examines the turbulent heat transfer characteristics of Al2O3–Cu hybrid nanofluids in circular ducts with triangular rib configurations. Numerical simulations were conducted for a 25 cm long, -cm high duct with walls maintained at 313 K. Hybrid nanofluids enter at 298 K, with triangular ribs on the internal surface at three attack angles (45°, 60°, and 90°) spaced 20 mm apart. Al2O3–Cu/H2O hybrid nanofluids at concentrations of 0.1–2 vol.% were investigated for Reynolds numbers between 20,000 and 60,000. The study aimed to determine the optimal rib configuration and nanofluid concentration for enhancing heat transfer while minimizing friction losses. Key findings include: (1) the 60° rib configuration produced the highest local heat transfer coefficient, with the maximum occurring at the rib centers. (2) Increasing nanofluid concentration and Reynolds number enhanced heat transfer but reduced skin friction. (3) The optimal performance was achieved with 2 vol.% Al2O3–Cu at Re = 60,000. (4) Velocity contours revealed larger recirculation zones for 60° ribs compared to 45° and 90° configurations. (5) Turbulent kinetic energy was highest for 60° ribs, contributing to enhanced thermal performance. These findings have implications for improving the efficiency of heat exchangers, cooling systems, and other thermal management applications. [ABSTRACT FROM AUTHOR]

The flat-plate solar collector (FPSC) three-dimensional (3D) model was used to numerically evaluate the energy and economic estimates. A laminar flow with 500 ≤ Re ≤ 1900, an inlet temperature of 293 K, and a solar flux of 1000W/m² were assumed the operating conditions. Two mono nanofluids, CuO-DW and Cu-DW, were tested with different shapes (Spherical, Cylindrical, Platelets, and Blades) and different volume fractions. Additionally, hybrid nanocomposites from CuO@Cu/DW with different shapes (Spherical, Cylindrical, Platelets and Blades), different mixing ratios (60%+40%, 50%+50% and 40%+60%) and different volume fractions (1 volume%, 2 volume%, 3 volume% and 4 volume%) were compared with mono nanofluids. At 1 volume% and Re = 1900, CuO-Platelets demonstrated the highest pressure drop (33.312 Pa). CuO-Platelets achieved the higher thermal enhancement with (8.761%) at 1 vol.% and Re = 1900. CuO-Platelets reduced the size of the solar collector by 25.60%. Meanwhile, CuO@Cu-Spherical (40:60) needed a larger collector size with 16.69% at 4 vol.% and Re = 1900. CuO-Platelets with 967.61, CuO -- Cylindrical with 976.76, Cu Platelets with 983.84, and Cu-Cylindrical with 992.92 presented the lowest total cost. Meanwhile, the total cost of CuO -- Cu -- Platelets with 60:40, 50:50, and 40:60 was 994.82, 996.18, and 997.70, respectively. [ABSTRACT FROM AUTHOR]

This study aims to investigate the thermal behavior and aerodynamic phenomena in a heated channel with varied rib configurations using computational fluid dynamics (CFD) simulations. Incorporating ribs in such systems enhances heat transfer and increases flow resistance and manufacturing costs. Understanding heat exchanger theory, measurement methods, and numerical calculations are crucial for creating efficient heat exchangers. The current research employs numerical analysis to assess the impact of hybrid ribs on heat transfer enhancement in forward-facing contracting channels (FFS). A two-dimensional forced convection heat transfer simulation under turbulent flow conditions was performed, considering the presence and absence of ribs with dimensions of 1 cm by 1 cm and spaced 11 cm apart. The arrangement of the ribs causes symmetrical temperature and flow distribution after and before each rib. The results demonstrate that the use of hybrid ribs outperforms the use of individual rib configurations in terms of thermal performance. This is due to the distinct flow patterns generated as the fluid passes through each rib. The triangle ribs had a more significant impact on the pressure drop than other rib configurations, while the cross ribs showed a lesser effect. The ribs improve the heat transfer coefficient while increasing the pressure drop, and the values of the Reynolds number were found to be directly proportional to the heat transfer coefficient and the pressure drop. The study concludes with a qualitative and quantitative analysis demonstrating the accuracy and coherence of the obtained computational results. [ABSTRACT FROM AUTHOR]

Global technological advancements drive daily energy consumption, generating additional carbon-induced climate challenges. Modifying process parameters, optimizing design, and employing high-performance working fluids are among the techniques offered by researchers for improving the thermal efficiency of heating and cooling systems. This study investigates the heat transfer enhancement of hybrid "Al2O3-Cu/water" nanofluids flowing in a two-dimensional channel with semicircle ribs. The novelty of this research is in employing semicircle ribs combined with hybrid nanofluids in turbulent flow regimes. A computer modeling approach using a finite volume approach with k-ω shear stress transport turbulence model was used in these simulations. Six cases with varying rib step heights and pitch gaps, with Re numbers ranging from 10,000 to 25,000, were explored for various volume concentrations of hybrid nanofluids Al2O3-Cu/water (0.33%, 0.75%, 1%, and 2%). The simulation results showed that the presence of ribs enhanced the heat transfer in the passage. The Nusselt number increased when the solid volume fraction of "Al2O3-Cu/water" hybrid nanofluids and the Re number increased. The Nu number reached its maximum value at a 2 percent solid volume fraction for a Reynolds number of 25,000. The local pressure coefficient also improved as the Re number and volume concentration of "Al2O3-Cu/water" hybrid nanofluids increased. The creation of recirculation zones after and before each rib was observed in the velocity and temperature contours. A higher number of ribs was also shown to result in a larger number of recirculation zones, increasing the thermal performance. [ABSTRACT FROM AUTHOR]

Nanofluids are recommended to improve heat transfer in cooling and heating systems, resulting in significant benefits. This paper numerically investigates turbulent heat transfer and Al2O3-nanofluid flow over a vertical double forward-facing step. A two dimensional with three different cases of vertical DFFS is conducted using K-ε model based on finite volume method for volume fraction of nanofluids varied for 1%, 2%,3% and Reynolds number changed from 10000 to 40000. With increasing Reynolds number, there is an increase in local coefficients of heat transfer, with the highest coefficient of heat transfer detected at Re=40000. For volume fractions of Al2O3= 3% and Reynolds numbers of 40000, the effects of step height on surface coefficients of heat transfer are described. In addition, the findings have discovered that as the volume fraction of Al2O3 nanofluids has increased, the coefficient of heat transfer has increased as well, with the maximum coefficient of heat transfer occurring at a volume fraction of Al2O3 nanofluids of 3%. Furthermore, the first step-case 2 local coefficient of heat transfer has been higher than the first step-cases 1 and 3. Increased Re number causes a sharp drop in local static pressure at the first and at the second steps. Due to the recirculation flow, there has been a reduction in velocity profile near the first and second steps, indicating an increase in heat transfer rate. Moreover, velocity counters are shown in order to demonstrate how Reynolds number affects the size of the recirculation zone. In addition, the turbulence kinetic energy counter has been shown in order to demonstrate how to achieve thermal efficiency in the second step in all the cases. [ABSTRACT FROM AUTHOR]