The Baffle Length Effects on the Natural Convection in Nanofluid-Filled Square Enclosure with Sinusoidal Temperature.

The proper process of applying heat to many technological devices is a significant challenge. There are many nanofluids of different sizes used inside the system. The current study combines this potential to improve convection effects, considering numerical simulations of natural convection using Cu/water nanofluids in a square enclosure with bottom blocks embedded in baffles. The enclosure consists of two vertical walls with isothermal boundary conditions; the left wall is the sinusoidal heat source, whereas the right wall is cooled. The investigations dealt with the influences of nanoparticle concentration, Rayleigh number, baffle length, and thermal conductivity ratioon isotherms, stream functions, and average Nusselt number. The results present that, when the Rayleigh number rises, the fluid flow velocity increases, and the heat transfer improves. Furthermore, the baffle length case (Lb = 0.3) provides higher heat transfer characteristics than other baffle height cases.

Natural convection in a porous cavity filled (35%MWCNT-65% Fe3O4)/water hybrid nanofluid with a solid wavy wall via Galerkin finite-element process.

A numerical analysis of natural convective heat transfer in a square porous cavity with a solid wavy finite wall filled with (35% MWCNT-65% Fe3O4)/water hybrid nanofluid. The left wavy wall is heated to a constant temperature, the right wall is held at a low temperature, and the top and bottom walls are thermally insulated. Darcy-Brinkman-Forchheimer model is used to model porous medium with hybrid nanofluid. COMSOL Multiphasic Modeling Software via Galerkin finite element method has been used to solve the governing equations. The dimensionless parameters used in this investigation are; modified Rayleigh number (Ra* = 102, 103, 104, and 106), Darcy number (Da = 10-2, 10-4 and 10-6), Solid volume fraction (ϕ = 0.01, 0.03, and 0.05),undulation number (N = 1, 3, 5, and 7), amplitude of the wavy wall (A = 0.1, 0.2, and 0.3), and Prandtl number = 7.2 at constant high porosity. At a high Darcy number (Da = 10-2), the isotherm lines parallel to the vertical cavity walls, which means that conduction is the primary method of heat transport. At the same time, the convection mode is increasingly necessary at a lower Darcy number. The convection flow and the maximum amounts of stream function are reduced when both A = 0.1 and N = 1 increase. The average Nusselt number increases with increasing Ra*, while it decreases with increasing Darcy number and amplitude wave numbers. It has been determined that the largest improvement in heat transfer is at Ra* = 104, Da = 10-6, ϕ = 0.05, A = 0.1, and N = 1.

Investigation of mixing viscoplastic fluid with a modified anchor impeller inside a cylindrical stirred vessel using Casson-Papanastasiou model.

In process engineering as chemical and biotechnological industry, agitated vessels are commonly used for various applications; mechanical agitation and mixing are performed to enhance heat transfer and improve specific Physico-chemical characteristics inside a heated tank. The research subject of this work is a numerical investigation of the thermo-hydrodynamic behavior of viscoplastic fluid (Casson-Papanastasiou model) in a stirred tank, with introducing a new anchor impeller design by conducting some modifications to the standard anchor impeller shape. Four geometry cases have been presented for achieving the mixing process inside the stirred vessel, CAI; classical anchor impeller, AI1; anchor impeller with added horizontal arm blade, AI2 and AI3 anchor impeller with two and three added arm blades, respectively. The investigation is focused on the effect of inertia and plasticity on the thermo-hydrodynamic behavior (flow pattern, power consumption, and heat transfer) by varying the Reynolds number (Re = 1, 10, 100, 200), Bingham number (Bn = 1, 10, 50), in addition to the effect of geometry design in the overall stirred system parameters. The findings revealed an excellent enhancement of flow pattern and heat transfer in the stirred system relatively to the increase of inertia values. Also, an energy reduction has been remarked and the effect of anchor impeller shape. AI3 geometry design significantly improves the flow pattern and enhances heat transfer by an increased rate of 10.46% over the other cases.

Effect of using spirulina algae methyl ester on the performance of a diesel engine with changing compression ratio: an experimental investigation.

Diesel engine characteristics were investigated experimentally while adding different concentrations of third generation biodiesel spirulina algae methyl ester (SAME). Three volumetric blends of SAME are added to standard Iraqi diesel, namely 10% SAME, 20% SAME, and 30% SAME. The properties of the fuels were found according to the American Society for Testing and Materials standards (ASTM). Experimental work was conducted on a single-cylinder diesel engine under variable load and compression ratio. Three compression ratios are used, starting from 14.5, 15.5, and 16.5. Based on the results obtained, the presence of SAME along with diesel caused an increase in Brake specific fuel consumption (BSFC), carbon dioxide (CO2), and nitrogen oxides (NOx) while decreasing both brake thermal efficiency (BTE) and exhaust gas temperature (EGT). Hydrocarbon (HC) emissions decreased by 7.14%, 8.57%, and 10.71%, for 10% SAME, 20% SAME, and 30% SAME, respectively, compared to the original neat diesel fuel. The dramatic carbon monoxide (CO) emission reduction was at full load point. The addition of SAME from (10 to 30)% reported a decrease in CO by (6.67-20)%. NOx, as well as CO2 emission, are increased as a result of SAME addition. The compression ratio change from (14.5/1 to 16.5/1) led to increased BTE, NOx, and decreased BSFC and all carbon emissions. The experimental results are validated with other studies' findings, and minor divergence is reported.

Improvement of the aerodynamic behaviour of the passenger car by using a combine of ditch and base bleed.

The current study investigates different methods to minimize the drag coefficient (CD) without ignoring the safety factor related to the stability of a vehicle, i.e., the lift coefficient (CL). The study was carried out by employing an SUV car analyzed numerically using one of the CFD software, Ansys. Four different models such as realizable k-ε, standard k-ω, shear stress transport k-ω, and Reynolds stress model (RSM). The considered models have been validated with experimental data and found in good agreement. The considered inlet velocity varies from 28 to 40 m/s, the results showed that the drag coefficient and the stability are both improved by applying a modification on the roof of the considered car.

Improvement of the aerodynamic behavior of a sport utility vehicle numerically by using some modifications and aerodynamic devices.

The present study proposes aerodynamically optimized exterior designs of a sport utility vehicle using computational fluid dynamics analysis based on steady-state Reynolds-averaged Navier-Stokes turbulence models. To achieve an optimal design, modifications of the outer shape and adding some aerodynamic devices are investigated. This study focuses on modifying this vehicle model's upper and front parts. At the same time, the rear diffuser and spare tire on the back door as a fairing are used as aerodynamic devices for improving streamlines. All these modifications and add-on devices are simulated individually or in combination to achieve the best exterior design. A variety of Reynolds numbers are used for determining the optimization variables. Tetrahedral cells are used throughout the global domain because of the sharp edges in the geometry of the Discovery car model. At the same time, prism cells around car surfaces are adopted to improve the accuracy of the results. A good agreement between the numerical drag coefficient in the present study for the baseline models and the experimental data has been achieved. Changes in the drag and lift coefficients are calculated for all models. It is clear from the numerical results that the use of combined modifications and add-on devices has a significant effect in improving the overall aerodynamic behavior. As a result, the drag coefficient for the optimal design of the Discovery 4th generation is reduced from 0.4 to 0.352 by about 12% compared to the benchmark. Simultaneously, the lift coefficient is 0.037 for optimal design, and it is an acceptable value. It is found that combining all optimal modified configurations can improve both CD and CL simultaneously.

Influence of entropy on Brinkman-Forchheimer model of MHD hybrid nanofluid flowing in enclosure containing rotating cylinder and undulating porous stratum.

The current article aims to discuss the natural convection heat transfer of Ag/Al2O3-water hybrid filled in an enclosure subjected to a uniform magnetic field and provided with a rotating cylinder and an inner undulated porous layer. The various thermo-physical parameters are investigated such as Rayleigh number ([Formula: see text]), Hartmann number ([Formula: see text]), and the nanoparticles concentration ([Formula: see text]). Likewise, the rotational speed of the cylinder ([Formula: see text]), as well as several characteristics related to the porous layer, are examined li its porosity ([Formula: see text]), Darcy number ([Formula: see text]) which indicates the porous medium permeability and the number of undulations ([Formula: see text]). The calculations are carried out based on the Galerkin Finite element method (GFEM) to present the streamlines, isotherms, entropy generation, and average Nusselt numbers in details. The main results proved that increment of Rayleigh number and Darcy number enhances heat transfer convection within the enclosure. Whilst, the porosity presents a minimal impact. Also, the rotational speed in a positive direction has a favorable influence on the heat transfer dispersion across the cavity.