Heat transfer enhancement in oscillatory two-phase flow of Casson and ferrofluid comprising differently shaped nanoparticles in a horizontal composite channel

The most commonly discussed topic at the present time is the fluid flow in a channel having a porous area, as it is of practical importance for petroleum extraction, frequently isolated irrigation, coolant circulation, biofluid transportation in living organisms, and industrial cleaning systems. An investigation of heat transfer characteristics of unsteady magnetohydrodynamics oscillatory two-immiscible fluid flow of Casson fluid (CF) and ferrofluid (FF) in a long-infinite horizontal composite channel is performed analytically. The channel is divided into two regions. Region I is occupied by a porous region with CF, while Region II is a clear region filled with FF. The mathematical system of coupled partial differential equations is solved analytically considering the two-term periodic and nonperiodic functions. The influences of physical parameters such as CF parameter, porosity parameter, nanoparticles volume fraction, Hartmann number, periodic frequency parameter, oscillations amplitude, and pressure on momentum as well as heat transfer are presented through graphical illustrations (two-dimensional along with three-dimensional) and in tabular form using the MATHEMATICA program. Four different shaped nano-size ferroparticles are used in this study. The investigation of four different nanosized ferroparticles exhibits that the momentum transfer is higher when brick-shaped nanosized ferroparticles are added to the base fluid, water. It is also observed that thermal performance enhances in the case of brick-shaped nanosized ferroparticles compared to the blade, cylinder, and platelet-shaped nanosized ferroparticles. It is observed that the dispersion of brick-shaped nanosized ferroparticles is recommended in base fluid water for greater thermal performance through a horizontal channel.     

Marangoni convective nanofluid flow over an electromagnetic actuator in the presence of first‐order chemical reaction

The present study aims to investigate Marangoni‐forced convective nanofluid flow over an electromagnetic actuator (Riga plate). A first‐order homogeneous chemical reaction is considered. The thermocapillary and solutocapillary Marangoni effect developed by the surface tension is considered as a driving force for the nanofluid. In addition, Grinberg‐term is accounted to involve the impact of Lorentz force impinged by the actuator in the model. A set of nonlinear ordinary differential equations is obtained via suitable transformations for a nonsimilar analysis. Series solutions are achieved through homotopy to discuss the behavior of the velocity field, thermal distribution, and concentration of the nanoparticles graphically. The variation in Nusselt and Sherwood numbers is discussed. The outcomes declared that the flow parallel to the surface of the plate is assisted by the Lorentz forces generated by electromagnetic bars of the actuator resulting in an enhancement in the fluid motion. Furthermore, the stronger Marangoni effect resulted in the declining trend of the temperature profile. The concentration of nanoparticles near the surface reduced intensive chemical reaction inside the nanofluid.     

Magnetohydrodynamic flow of a nanofluid due to a non‐linearly curved stretching surface with high order slip flow

This article numerically scrutinizes magnetohydrodynamic flow of a nanofluid due to a nonlinearly curved stretching surface with third order slip flow conditions. The third order slip flow condition has not yet been discussed in fluid dynamics research. The mathematical modeling of the flow problem is given in partial differential equation form. The governing partial differential equations are transformed to high order ordinary differential equations using the similarity transformation and then solved numerically using a boundary value problem solver, bvp4c from Matlab software. The effect of the governing parameters on the flow of the velocity profile, concentration, and heat transfer characteristics are studied. Also graphs of the skin friction coefficient, local Nusselt number, and Sherwood number are drawn and their numerical values are tabulated. The numerical results of the study are compared with previously published articles in the limiting condition. The velocity of the flow field is reduced as the third order slip parameter and the first order slip parameter rises, but the velocity grows as the values of the second order slip flow parameter are elevated. The findings also indicate that the local Nusselt number is depreciated but local Sherwood numbers are elevated when the Soret and Dufour numbers are larger.     

Investigation of MHD Go-water nanofluid flow and heat transfer in a porous channel in the presence of thermal radiation effect

In this paper, flow and heat transfer of MHD Go-water nanofluid between two parallel flat plates in the presence of thermal radiation are studied. One of plates is externally heated and cooled by coolant injection through the other plate, which also expands or contracts with time. A similarity transformation is used to transmute the governing momentum and energy equations into non-linear ordinary differential equations with the appropriate boundary conditions. The obtained non-linear ordinary differential equations are solved by Duan–Rach Approach (DRA). This method allows us to find a solution without using numerical methods to evaluate the undetermined coefficients. This method modifies the standard Adomian Decomposition Method by evaluating the inverse operators at the boundary conditions directly. The impacts of various parameters such as the Reynolds number, the expansion ratio, the magnetic parameter, the power law index, the solid volume fraction and the radiation parameter are investigated on the velocity and temperature. Furthermore, the value of the Nusselt number is calculated and presented through figures. The results indicate that the temperature profile and the Nusselt number have a direct relationship with the solid volume fraction and have an inverse relationship with the radiation parameter. In addition, the limiting cases are gained and found to be in an excellent agreement with the previous works.     

Experimental investigation of heat transfer enhancement in helical coil heat exchangers using water based CuO nanofluid

The present work deals with the study of heat transfer enhancement using water based CuO nanofluids in the helical coil heat exchanger. Nanofluids were prepared using two-step method by using wet chemical method. Nanofluids with various volume percentage between 0 and 0.5 of CuO nanoparticles and their flow rate between 30 and 80 LPH (Reynolds number ranging from 812 to 1895, Laminar flow regime) were considered in the present study. The setup consists of a test section (helical coil), cooler, reservoir, pump, flow meter, thermocouples and flow controlling system. The temperature measurements were carried out with the help of thermocouples. The investigation was carried out to study the effect of particle loading and flow rate on heat transfer coefficient and Nusselt number. It has been found that the increase in the loading of CuO nanoparticles in base fluid shows a significant enhancement in the heat transfer coefficient of nanofluid. In the present study, at 0.1 vol% concentration of CuO nanoparticles in nanofluid, enhancement in heat transfer coefficient was 37.3% as compared to base fluid while at 0.5 vol%, it is as high as 77.7%. Also with the increase in the flow rate of the CuO nanofluid, significant increase in heat transfer coefficient was observed.     

Dual Branches of MHD Three-Dimensional Rotating Flow of Hybrid Nanofluid on Nonlinear Shrinking Sheet

In this study, magnetohydrodynamic (MHD) three-dimensional (3D) flow of alumina (Al₂O₃) and copper (Cu) nanoparticles of an electrically conducting incompressible fluid in a rotating frame has been investigated. The shrinking surface generates the flow that also has been examined. The single-phase (i.e., Tiwari and Das) model is implemented for the hybrid nanofluid transport phenomena. Results for alumina and copper nanomaterials in the water base fluid are achieved. Boundary layer approximations are used to reduce governing partial differential (PDEs) system into the system of the ordinary differential equations (ODEs). The three-stage Lobatto IIIa method in bvp4c solver is applied for solutions of the governing model. Graphical results have been shown to examine how velocity and temperature fields are influenced by various applied parameters. It has been found that there are two branches for certain values of the suction/injection parameter b: The rise in copper volumetric concentration improved the velocity of hybrid nanofluid in the upper branch. The heat transfer rate improved for the case of hybrid nanofluid as compared to the viscous fluid and simple nanofluid.     

CFD analysis of employing a novel ecofriendly nanofluid in a miniature pin fin heat sink for cooling of electronic components: Effect of different configurations

This research aims to study the thermal and hydraulic attributes as well as energy efficiency of a new ecofriendly nanofluid including functionalized graphene nanoplatelets in a mini heat sink with three different pin fins. The circular, triangular and drop-shaped pin fins are investigated and compared with each other. The effects of nanoparticle fraction and flow velocity on the thermal resistance, temperature uniformity, convective heat transfer coefficient, maximum surface temperature, average surface temperature, pressure loss and pumping power are assessed. Increasing the concentration or velocity reduces the temperature on the heated wall, and also improves the temperature distribution uniformity. At both constant velocity and invariant pumping power, the heat sink fitted with the circular pin fins leads to the best performance while that equipped with the triangular pin fins results in the worst efficiency. In addition, the Figure of Merit (FoM) is greater than 1 for all conditions, which proves that the nanoparticle suspension possesses a greater merit to be employed as the coolant in the heat sinks compared to the base fluid.     

Numerical investigation of temperature increment effect on bubble dynamics in stagnant water and Al2O3 nanofluid column

Formation, growth, and detachment of injected air bubble from a submerged needle in stagnant liquid at the different temperature of fluid, investigated numerically. Experiments have been done for validation of numerical simulation results. The injection flow rate of air was varied between 600 and 1200?mL/h in experimental study. Bubble formation, growth, and detachment information were obtained using high speed camera and visual photography technique. Young–Laplace equation that was derived from the force balance on the bubble, was utilized in numerical simulation. A novel method was used for solution of Young–Laplace equation. The bubble diameter, instantaneous contact angle, volume, and other characteristics of bubble were studied at different temperature of operating condition. Also, the enhancement of temperature in Al₂O₃ nanofluid with 0.01% volume concentration (φ?=?0.01%) was compared with deionized water results. The results reveal that by increasing the Al₂O₃ nanofluid and the deionized water temperature, the diameter, volume, and center of gravity of bubble decrease; however, the instantaneous contact angle increases. Meanwhile, the size of bubble at Al₂O₃ nanofluid is larger than of that in deionized water at same temperature. Also, the bubble aspect ratio is almost senseless to temperature increment in both deionized water and Al₂O₃ nanofluid. Eventually, the variation of operating temperature and adding of nanoparticle to the deionized water have significant influence on behavior of growing bubble.     

Investigation of the effect of magnetic field on mass transfer parameters of CO2 absorption using Fe3O4‐water nanofluid

In this study, the enhancement of physical absorption of carbon dioxide by Fe₃O₄‐water nanofluid under the influence of AC and DC magnetic fields was investigated. Furthermore, a gas‐liquid mass transfer model for single bubble systems was applied to predict mass transfer parameters. The coated Fe₃O₄ nanoparticles were prepared using co‐percipitation method. The results from characterization indicated that the nanoparticles surfaces were covered with hydroxyl groups and nanoparticles diameter were 10–13 nm. The findings showed that the mass transfer rate and solubility of carbon dioxide in magnetic nanofluid increased with an increase in the magnetic field strength. Results indicated that the enhancement of carbon dioxide solubility and average molar flux gas into liquid phase, particularly in the case of AC magnetic field. Moreover, results demonstrated that mass diffusivity of CO₂ in nanofluid and renewal surface factor increased when the intensity of the field increased and consequently diffusion layer thickness decreased. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2176–2186, 2017