Numerical study of mixed convection nanofluid in an annulus enclosure between outer rotating cylinder and inner corrugation cylinder

Numerical investigations are presented for mixed convection problems in a concentric inner sinusoidal cylinder and an outer rotating circular cylinder, which were kept at constant hot and cold temperatures, respectively. The free space between the cylinders and the enclosure walls was filled with a water‐Cu nanofluid. The governing equations are formulated for velocity, pressure, and temperature formulation and are modeled in COMSOL5.2a, a partial differential equation solver based on the Galerkin finite element method. The governing parameters considered are the solid volume fraction, [0, 0.02, 0.04, and 0.06], Re (1, 25, 100, 200, and 300), and Ra (less than 10⁴), and the inner cylinder corrugation frequencies varied from (N = 3, 6, and 9). According to the calculations, the Reynolds number, the Rayleigh number, the nanoparticle volume fraction, and the number of corrugations play an important role of forming the stream and isothermal lines, the local and the average Nusselt number inside the annulus enclosure. The average Nusselt number decreases with increasing Reynolds number and the number of corrugations, while it increases as the Rayleigh number and the volume fraction increase.     

Inhomogeneous flow model of natural convection,entropy generation,and heatlines visualization in wavy I-shaped enclosure with rectangular heater

The present investigation is on examination of the natural convection and entropy generation considering the heatlines visualization of nanofluid I-shaped enclosure with two corrugated walls considering inner rectangular heater of three different heights. The influence of Brownian motion along with thermophoresis had been implemented using Inhomogeneous two-phase model of nanofluid. The governing equations were solved numerically using COMSOL software. Influence of Rayleigh number $$, Buoyancy ratio number $$, Lewis number $$, heater length $$. The results indicate that the influence of Lewis number on heat transfer bettering is stronger at high Rayleigh number $$ while its impact is negligible at a lower value of Rayleigh number (conduction mode). In addition, the total entropy generation gets its highest value at Lewis number $$. Bejan number, fluid flow strength and heat rate increase as the rectangular heater height increases. Also, higher heat transfer augmentation is taken when the heater height is $$ while increasing the heater height to $$ leads to more total entropy generation. The impact of heater height on total entropy generation is highly affected by Rayleigh number as increasing the heater height from $$ into $$, total entropy generation increases by $$ at $$ while it increases by $$ at $$.     

Analysis of double-diffusive hydrothermal flow in a domestic stack: The effect of side walls patterns

Domestic stack is considered to investigate the double-diffusive laminar natural convection. The working fluid is a gaseous mixture that has similar physical properties to carbon dioxide. Knowing the patterns of gaseous mixture distribution and determining the carbon deposit regions can help in carbon capture problems. The present study uses the finite element method to numerically examine the double ratio-diffusive physical phenomena in a rectangular-trapezoidal enclosure and to simulate the stack under a wide range of dimensionless parameters, such as buoyancy ratio $1\le N_{\mathit{BR}}\le 7$, Lewis number $2\le \mathit{Le}\le 8$, and Rayleigh number ${10}^3\le \mathit{Le}\le {10}^5$ for different aspect ratios. Nine different cases of the geometrical ratio are selected to cover most possible design configurations. The results indicate that increasing the Lewis number leads to augmented solutal transport but reduces heat transfer. However, both heat and mass transfer are observed by increasing the buoyancy ratio. It is worth mentioning that increasing the ratio of upper side length to base length $\left(\frac{d}{D}\right)$ from $\left(\frac{1}{4}\right)$ to $\left(\frac{3}{8}\right)$ leads to a significant increase in mass transfer by 75% and heat transfer enhancement ratio by around 50%.     

Optimizing the Roadside Unit Deployment Mechanism in VANET with Efficient Protocol to Prevent Data Loss

Wireless Personal Communications - RTS/ CTS protocol serves multihop wireless networks poorly due to its single-hop design. TDMA protocol surpasses RTS/ CTS but unable to solve the dynamic needs of...     

Green synthesis of silver nanoparticle by cauliflower extract: characterisation and antibacterial activity against storage

Green synthesis of silver nanoparticles (AgNPs) was accomplished using different volumes of cauliflower extract and 0.001 M silver nitrate solution at 80°C for 15 min. A brownish‐red solution of AgNPs formed was tested by ultraviolet–visible absorption spectroscopy, Fourier‐transform infrared (FTIR), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). Surface plasmon resonance of AgNPs appeared at 416 nm. Also, the kinetic of AgNPs formation was studied and follows a sigmoidal pattern. Storing time was studied for the freshly prepared AgNPs after 60 days. FTIR analysis shows the adsorption of active components on AgNPs surface, and these components are responsible for reduction besides working as a stabiliser like a capping agent, also FTIR analysis of AgNPs after storage showed no change in peaks location. The SEM exhibited a globular shape of AgNPs, and the particle size ranged from 25 to 100 nm, while the XRD particle size calculation was 25 nm with cubic phase lattice. The antibacterial activity was tested against Gram‐positive and ‐negative bacteria showed an inhibition zone of 16–27 mm and the antibacterial activity tested for the same bacteria after storage for about 10 months showed an inhibition zone of 6–10 mm.Inspec keywords: microorganisms, reduction (chemical), nanofabrication, surface plasmon resonance, silver, transmission electron microscopy, nanoparticles, particle size, visible spectra, ultraviolet spectra, adsorption, antibacterial activity, scanning electron microscopy, X‐ray diffraction, Fourier transform infrared spectra, nanomedicineOther keywords: antibacterial activity, green synthesis, silver nanoparticle, brownish‐red solution, surface plasmon resonance, FTIR analysis, active components, silver nitrate solution, ultraviolet‐visible absorption spectroscopy, AgNP surface, cauliflower extract, Fourier‐transform infrared spectroscopy, scanning electron microscopy, SEM, X‐ray diffraction, XRD, sigmoidal pattern, storing time, adsorption, stabiliser, capping agent, globular shape, particle size, cubic phase lattice, Gram‐positive bacteria, Gram‐negative bacteria, inhibition zone, reduction, time 60.0 d, temperature 80.0 degC, time 15.0 min, wavelength 416.0 nm, Ag     

Experimental and numerical study on the heat transfer enhancement over scalene and curved-side triangular ribs

The present study examines the turbulent flow of mixed convection heat transfer enhancement within a rectangular channel considering three different novel shapes of ribs (smooth, scalene, and curved-side triangular). The investigations were conducted experimentally by developing a new test facility, while the numerical computations were carried out using the finite volume method. The experimental work involves constructing of the channel, ribs, and all equipment and measurement instruments. The numerical work is based on ANSYS FLUENT considering the k–ε turbulent model. The results are presented and compared in terms of Nusselt number, friction factor, and performance factors for Reynolds numbers ranging between 3000 and 12,000. By comparing the average values of the numerically obtained Nusselt number with experimental measurements, the data showed a close agreement with a maximum difference of 5%. It also found that scalene triangular ribs (STRs) provide better performance in terms of heat transfer, although introducing a slight increase in friction losses. STRs showed (20%) increase in Nusselt number compared with smooth channel, and 3%–6% increase in Nusselt number compared with curved-side triangular ribs (CTRs). In contrast, CTRs have a lower friction factor value of 5% compared with STRs at a low value of a Reynolds number of 3000. Furthermore, the Nusselt number changes significantly (250% increase) by increasing the value of the Reynolds number from 3000 to 12,000. A thermal performance factor of up to 1.28 was achieved for the STRs at the lowest range of Reynolds' number of 3000. The findings from the present study are of practical importance for industries requiring heat transfer enhancement techniques to improve heat transfer equipment performance.