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Transformers are crucial equipment in electrical distribution systems but have a significant potential for failure. Insulation materials, including transformer oil (TO), play a primary role in transformer failures. A fire involving the TO can lead to a large explosion, causing the main tank to rupture and resulting in extensive damage to the entire transformer and the surrounding area. Mineral oil (MO) is the most widely used type due to its availability and relatively low cost compared to other types of oil. However, MO has a critical disadvantage, which is its very low flash point. The low flash point makes MO highly flammable. When the oil fires in an enclosed space, such as a transformer tank, the pressure inside the tank increases, leading to a large explosion. Therefore, research on increasing the flash point of MO is highly necessary. The application of nanotechnology is a promising approach to increasing the flash point of base fluids. Research on the effect of nanoparticles (NPs) on flash points is very limited in the literature; thus, there is significant potential for further research in this field. The majority of studies indicate an increase in flash points with the addition of NPs to MO. There is only one study that shows a decrease in flash point, which is −1.33% compared to MO. From all the reviewed studies, it can be concluded that NPs are a potential solution to increase the flash point of MO. Despite their benefits, NPs require a thorough examination of health and environmental impacts, along with proper waste management, to ensure their advantages. [ABSTRACT FROM AUTHOR]

This manuscript explores the application of nanofluids in helical microfin tube concentric heat exchangers and investigates the potential for improved heat transfer performance. Helical microfin tubes offer enhanced heat transfer characteristics due to increased surface area and improved fluid mixing. When combined with nanofluids, which are base fluids with suspended nanoparticles, the thermal conductivity and convective heat transfer properties can be further enhanced. The objective of this present work is to investigate experimentally on heat transfer enhancement Al2O3/distilled water (0.05 vol.%) flowing through a helical microfin concentric heat exchanger in both parallel and counter flow in the vertical direction. The result is revealed that Al2O3/water nanofluids has enhanced thermal evaluation performance to water as base fluid. Counter flow might exhibit a more balanced performance, with a moderate enhancement in heat transfer while considering the pressure drop compared to parallel flow.

In this study, the potential usage of hybrid nanofluids for brushless direct current (BLDC) motor cooling was compared. Due to their efficiency, durability, and small size, brushless direct current (BLDC) motors are a type of electric motor that are frequently employed in electric vehicles (EVs). In order to maintain appropriate operating temperatures and ensure long-term durability, cooling systems must be taken into account throughout the design of brushless direct current (BLDC) motors. Because excessive heat can shorten a motor's lifespan and affect its performance, effective cooling is crucial. Systems for cooling liquids need more parts and upkeep than those for cooling air. taken into account to get the maximum cooling effectiveness. The effectiveness and dependability of the liquid cooling system are greatly influenced by the system's correct design and implementation, including hose routing, sealing, and coolant choices. There are several approaches to improve a BLDC motor's hybrid nanofluid/nanofluid cooling system. In order to achieve the highest cooling efficiency, fluid flow velocity, nanoparticle concentration, and cooling system design should all be carefully taken into account.

AbstractThermal performance of Al2O3-TiO2/water hybrid nanofluids for cooling system using a helically coiled tube in a brushless direct current motor has been investigated numerically. The numbers of helical coils number were varied by 4, 6, 8, and 10 in coils and represented by Helical numbers 362, 355, 352, and 350, respectively. To solve the velocity and pressure discretization, the SIMPLE (Semi Implicit Method for Pressure Linked Equations) method was applied whereas to solve the energy and momentum equations, second order upwind was used. The result revealed that Nusselt number of Al2O3-TiO2/water hybrid nanofluids is greater than water, with an increased Nusselt number of 3.7% and 10.42% for 1 vol.% and 2 vol.%, respectively. The added nanoparticles concentration of Al2O3-TiO2/water hybrid nanofluids could not reduce significantly the stator temperature. Al2O3-TiO2/water hybrid nanofluids can reduce the stator temperature by 0.92% and 1.82% for 1 vol.% and vol.2%, respectively compared to water. However, the increased Reynolds number can reduce the stator temperature for all the observed working fluids. Helical number can affect the Nusselt number due to the influence of the helical geometry on the fluid’s flow behavior, heat transfer properties, and turbulence levels. Nusselt number of Al2O3-TiO2/water hybrid nanofluids at 1 vol.% has a higher value than water in each variation with an average increase in Nusselt number of 4.12% for all helical numbers. [ABSTRACT FROM AUTHOR]

Sengon wood beams are widely used as a wood packaging material. According to the International Standards for Phytosanitary Measures (ISPM), wood packaging materials must be pests-free. One method for eliminating problems with wood is by heat treatment or drying. This research aims to determine the kinetics of isothermal drying of sengon wood blocks using a combination of infrared and hot air heating. The drying process is carried out at temperatures of 70, 80 and 90 °C, air velocity of 1, 2 and 3 m/s until the final moisture content of the wood reaches 19%. The experimental data were fitted to four drying models, and analyzed using non-linear regression to determine the most suitable model and evaluated through the coefficient of determination (R2), chi-square (X2), and root mean square error (RMSE). The research results revealed that the temperature of the wood core reached 56 oC the fastest at a temperature of 90 oC and an air velocity of 3 m/s in 45 minutes. The highest R2 coefficient 0.9998 is found on the model page at a drying temperature of 70°C and an air velocity of 3 m/s with the lowest X, RMSE values of 0.00001 and 0.0025 respectively. The effective moisture diffusivity of sengon wood particles increased from 1.80x10-6 to 2.47x10-6 m2/min due to the increase in temperature treatment from 70 to 90 °C. The largest diffusion activation energy at an air velocity of 3 m/s is 23.92 kJ/mol. [ABSTRACT FROM AUTHOR]

Abstract This present work investigated the thermal characteristics and hydrodynamics behavior of TiO2-CNTs/water hybrid nanofluids for laminar and turbulent conditions. Assuming hybrid nanofluids as Newtonian fluids, simulation-based evaluation was conducted using a single-phase approach. Various nanoparticles loading and Reynolds number were employed to characterize the observed hybrid nanofluids’ convective heat transfer coefficient and friction factor. The ratio between heat transfer performance and pressure drop enhancement was analyzed to understand thermal performance. Constant heat flux of 6500 W/m2 and low nanoparticle concentration from 0.10 to 0.20 vol.% were applied in this simulation. The results revealed that adding CNTs nanoparticles did not significantly affect friction factor enhancement at very low concentrations due to their good tribological properties. For the thermohydraulic characteristics, the observed hybrid nanofluids were better than those of water. The thermal performance factor magnitudes of hybrid nanofluids were above 1.0 even though they did not have significant magnitudes at very low concentrations, 1.01 and 1.07 for laminar and turbulent flow, respectively. [ABSTRACT FROM AUTHOR]