Recently, the combination of hybrid nanofluids with microchannel heat sinks (MCHSs) has led to superior heat removal from high heat flux electronics chips. The present work aimed to evaluate numerically the first and second law performances of MCHSs using the new cost‐effective binary/ternary hybrid nanofluids. Water‐based binary and ternary hybrid nanofluids include the MgO/TiO₂ nanocomposite and the CuO/MgO/TiO₂ nanocomposite, respectively. The effects of the hybrid nanofluid volume concentration (vol.%) and Reynolds number (Re) on the heat transfer, pressure drop, combined thermohydraulic characteristics, and entropy generation characteristics of the MCHSs are discussed. The results show that higher values of the convective heat transfer coefficient, pressure drop, and frictional entropy generation rate are obtained when using hybrid nanofluids with high Re and vol.% values. Furthermore, by increasing the Re and vol.% values of the hybrid nanofluids, the bottom wall temperature, total thermal resistance, and thermal entropy generation rate decreased, and an increased temperature uniformity was obtained on the bottom surface of the MCHSs. In conclusion, the applied hybrid nanofluids are considered to be more promising heat transfer fluids when compared with conventional fluids such as water. Particularly, the CuO/MgO/TiO₂‐water ternary hybrid nanofluid exhibited a better heat transfer efficiency than did the MgO/TiO₂‐water binary hybrid nanofluid.

With the development of high-power fuel cell vehicles, heat dissipation requirements have become increasingly stringent. Although conventional cooling techniques improve the heat dissipation capacity by increasing the fan rotating speed or radiator dimensions, high energy consumption and limited engine compartment space prevent their implementation. Moreover, the insufficient heat transfer capacity of existing coolants limits the enhancement of heat dissipation performance. Therefore, exploring novel coolants to replace traditional coolants is important. Nanofluids composed of nanoparticles and base liquids are promising alternatives, effectively improving the heat transfer capacity of the base liquid. However, challenges remain that prevent their use in fuel cell vehicles. These include issues regarding the nanofluid stability and cleaning, erosion and abrasion, thermal conductivity, and electrical conductivity. In this review, we summarize the nanofluid applications in oil-fueled, electric, and fuel cell vehicles. Subsequently, we provide a comprehensive literature review of the challenges and future research directions of nanofluids as coolants in fuel cell vehicles. This review demonstrates the potential of nanofluids as an alternative thermal management system that can facilitate transition toward a low-carbon, energy-secure economy. It will serve as a reference for researchers to focus on new areas that could drive the field forward.

During an airborne infectious disease outbreak, bus passengers can be easily infected by the dispersion of exhaled droplets from an infected passenger. Therefore, measures to control the transport of droplets are necessary, such as a mask or purifier. The current research examined aerosol transport in a bus with air-conditioning. To determine the dispersion path, deposition distribution, and droplet escape time, the computational fluid dynamics were used to predict the flow field and the dispersion of droplets considering the effects of droplet size, location of the infected person, and purifier type. In addition, based on the viability and the number of virus particles in a droplet, the total number of virus particles inhaled by passengers over a 4-h journey was obtained by the superposition method. The Wells–Riley equation was then used to assess the infection risk of the passengers in the bus cabin. The results showed that droplets with a size of 1–20 μm have essentially the same deposition characteristics, and the location of the infected passenger affects the distribution of droplets' transport and the effectiveness of a purifier in removing droplets. A purifier can effectively remove droplets from passengers' coughs and reduce the infection risk of passengers. The performance of the smaller purifiers is not as stable as that of the larger purifiers, and the performance is influenced by the airflow structure where the infected passenger is located.