A concise review on the role of nanoparticles upon the productivity of solar desalination systems

In recent years, nanofluids have been widely used to improve the performance of various energy systems due to their favourable thermo-physical and optical characteristics. In particular, solar distillation, as an affordable and reliable technique to provide freshwater, has benefited from nanofluid technology. This article performs a review of the literature on the implementation of nanofluid technology in active and passive solar distillation systems. The progress made and the existing challenges are discussed, and some conclusions and suggestions are made for future research. The review indicates that the daily productivities of solar distillation systems enhance by using nanofluid and increasing the volume fraction of nanoparticles. However, long-term operational stability and life cycle assessment remain critical issues. These factors should be considered for future research in this field

COVID-19 spread in a classroom equipped with partition – A CFD approach

In this study, the motion and distribution of droplets containing coronaviruses emitted by coughing of an infected person in front of a classroom (e.g., a teacher) were investigated using CFD. A 3D turbulence model was used to simulate the airflow in the classroom, and a Lagrangian particle trajectory analysis method was used to track the droplets. The numerical model was validated and was used to study the effects of ventilation airflow speeds of 3, 5, and 7 m/s on the dispersion of droplets of different sizes. In particular, the effect of installing transparent barriers in front of the seats on reducing the average droplet concentration was examined. The results showed that using the seat partitions for individuals can prevent the infection to a certain extent. An increase in the ventilation air velocity increased the droplets’ velocities in the airflow direction, simultaneously reducing the trapping time of the droplets by solid barriers. As expected, in the absence of partitions, the closest seats to the infected person had the highest average droplet concentration (3.80 × 10−8 kg/m3 for the case of 3 m/s)

Measurement of Similarity in Academic Contexts

We propose some reflections, comments and suggestions about the measurement of similar and matched content in scientific papers and documents, and the need to develop appropriate tools and standards for an ethically fair and equitable treatment of authors

Nanofluids Effects on the Evaporation Rate in a Solar Still Equipped with a Heat Exchanger

In this paper, the performance of a solar still equipped with a heat exchanger using nanofluids has been studied both experimentally and theoretically through three key parameters, i.e., freshwater yield, energy efficiency and exergy efficiency. First, experiments are performed on a set-up, which is mainly composed of two flat plate solar collectors connected in series, and a solar still equipped with a heat exchanger. After heated in the collectors, the nanofluid enters the heat exchanger installed in the solar still basin to exchange heat with brackish water. The research question is to know how much the effect of nanofluids on the evaporation rate inside the solar desalination system is. The experiments are conducted for different nanoparticle volume fractions, two sizes of nanoparticles (7 and 40 nm), two depths of water in the solar still basin (4 and 8 cm), and three mass flow rates of nanofluids during various weather conditions. It is found that the weather conditions (mainly the sun radiation intensity) have a dominant influence on the solar still performance. To discover the effects of nanofluids, a mathematical model is developed and validated by experimental data at given weather conditions. The results reveal that using the heat exchanger at temperatures lower than 60 oC is not advantageous and the corresponding yield is smaller than that of solar still without the heat exchanger; although in such a case, using nanofluids as the working fluid in the heat exchanger can enhance the performance indices about 10%. At higher temperatures (e.g. 70 oC), the use of heat exchanger is beneficial; however, using nanofluids instead of water can augment the performance indices marginally i.e. just around 1%. In addition, it is found that in high temperatures using SiO2/water nanofluids, which have a lower effective thermal conductivity than that of Cu/water nanofluids, provides higher performance indices

Nano-engineered pathways for advanced thermal energy storage systems

Nearly half of the global energy consumption goes toward the heating and cooling of buildings and processes. This quantity could be considerably reduced through the addition of advanced thermal energy storage systems. One emerging pathway for thermal energy storage is through nano-engineered phase change materials, which have very high energy densities and enable several degrees of design freedom in selecting their composition and morphology. Although the literature has indicated that these advanced materials provide a clear thermodynamic boost for thermal energy storage, they are subject to much more complex multiscale governing phenomena (e.g., non-uniform temperatures across the medium). This review highlights the most promising configurations that have been proposed for improved heat transfer along with the critical future needs in this field. We conclude that significant effort is still required to move up the technological readiness scale and to create commercially viable novel nano-engineered phase change systems

A numerical study of magnetohydrodynamic transport of nanofluids from a vertical stretching sheet with exponential temperature-dependent viscosity and buoyancy effects

In this paper, a mathematical study is conducted of steady incompressible flow of a temperature-dependent viscous nanofluid from a vertical stretching sheet under applied external magnetic field and gravitational body force effects. The Reynolds exponential viscosity model is deployed. Electrically-conducting nanofluids are considered which comprise a suspension of uniform dimension nanoparticles suspended in viscous base fluid. The nanofluid sheet is extended with a linear velocity in the axial direction. The Buonjiornio model is utilized which features Brownian motion and thermophoresis effects. The partial differential equations for mass, momentum, energy and species (nano-particle concentration) are formulated with magnetic body force term. Viscous and Joule dissipation effects are neglected. The emerging nonlinear, coupled, boundary value problem is solved numerically using the Runge–Kutta fourth order method along with a shooting technique. Graphical solutions for velocity, temperature, concentration field, skin friction and Nusselt number are presented. Furthermore stream function plots are also included. Validation with Nakamura’s finite difference algorithm is included. Increasing nanofluid viscosity is observed to enhance temperatures and concentrations but to reduce velocity magnitudes. Nusselt number is enhanced with both thermal and species Grashof numbers whereas it is reduced with increasing thermophoresis parameter and Schmidt number. The model is applicable in nano-material manufacturing processes involving extruding sheets

Natural convection in an inclined cavity with time-periodic temperature boundary conditions using nanofluids: Application in solar collectors

Natural convection of alumina-water nanofluid inside a square cavity with time-sinusoidal temperature is studied numerically. The domain of interest is an inclined square cavity having isothermal wall at , while temperature of the wall is changed as a sinusoidal function of time, other walls are adiabatic. Dimensionless governing equations formulated using stream function, vorticity and temperature have been solved by finite difference method of the second order accuracy. The effects of Rayleigh number, oscillating frequency, cavity inclination angle and nanoparticles volume fraction on fluid flow and heat transfer have been analyzed. It has been found that a growth of boundary temperature oscillating frequency leads to an increase in the average Nusselt number oscillation amplitude and reduction of oscillation period. At the same time, the boundary temperature oscillating frequency is a very good control parameter that allows to intensify convective flow and heat transfer

Natural convection in an inclined cavity with time-periodic temperature boundary conditions using nanofluids: Application in solar collectors

Natural convection of alumina-water nanofluid inside a square cavity with time-sinusoidal temperature is studied numerically. The domain of interest is an inclined square cavity having isothermal wall at , while temperature of the wall is changed as a sinusoidal function of time, other walls are adiabatic. Dimensionless governing equations formulated using stream function, vorticity and temperature have been solved by finite difference method of the second order accuracy. The effects of Rayleigh number, oscillating frequency, cavity inclination angle and nanoparticles volume fraction on fluid flow and heat transfer have been analyzed. It has been found that a growth of boundary temperature oscillating frequency leads to an increase in the average Nusselt number oscillation amplitude and reduction of oscillation period. At the same time, the boundary temperature oscillating frequency is a very good control parameter that allows to intensify convective flow and heat transfer

Fame bias in editorial choice: Yes or No?

Recently, Scientometrics has published a paper titled “Is there bias in editorial choice? Yes” (Moustafa 2015) in which some comments are given on our published paper in Nature titled “Is there fame bias in editorial choice?” (Mahian et al. 2015). Unfortunately, the author of above mentioned paper and many other readers might misunderstand the main aim of our correspondence. Here, we try to give some explanations to clarify the main goal of analysis presented in the paper