Showing papers in "Heat Transfer Research in 2020"

Differential transform solution for hall and ion slip effects on radiative-convective casson flow from a stretching sheet with convective heating

Abstract: Magnetohydrodynamic (MHD) materials processing is becoming increasingly popular in the 21st century since it offers significant advantages over conventional systems including improved manipulation of working fluids, reduction in wear and enhanced sustainability. Motivated by these developments, the present work develops a mathematical model for Hall and Ion slip effects on non-Newtonian Casson fluid dynamics and heat transfer towards a stretching sheet with a convective heating boundary condition under a transverse magnetic field. The governing conservation equations for mass, linear momentum and thermal (energy) are simplified with the aid of similarity variables and Ohm’s law. The emerging nonlinear coupled ordinary differential equations are solved with an analytical technique known as the differential transform method (DTM). The impact of different emerging parameters is presented and discussed with the help of graphs and tables. Generally aqueous electro-conductive polymers are considered for which a Prandtl number of 6.2 is employed. With increasing Hall parameter and ion slip parameter the flow is accelerated whereas it is decelerated with greater magnetic parameter and rheological (Casson) fluid parameter. Skin friction is also decreased with greater magnetic field effect whereas it is increased with stronger Hall parameter and ion slip parameter values.

Linear stability analysis of MHD flow of micropolar fluid with thermal radiation and convective boundary condition: Exact solution

Abstract: Magnetohydrodynamic (MHD) flow of micropolar fluid by including the thermal radiation and convective condition on a shrinking surface in the presence of mass suction effects has been investigated. The momentum, angular momentum and energy equations, and the solutions of these equations are valid for whole Navier stokes, and microrotational and energy equations have been solved exactly. We obtain the solution in the form of an incomplete γ function for the energy equation. The results reveal that dual solutions exist for certain domains of different physical parameters. Furthermore, high suction produces the high effect of drag force, and as a result, coefficient of skin friction increases in the first solution. Stability analysis has been performed and determined that the first solution is more stable.

Finite element analysis of non-Newtonian magnetohemodynamic flow conveying nanoparticles through a stenosed coronary artery

Abstract: The present study considers two-dimensional mathematical modelling of non-Newtonian nanofluid hemodynamics with heat and mass transfer in a stenosed coronary artery in the presence of a radial magnetic field. The second-grade differential viscoelastic constitutive model is adopted for blood to mimic non-Newtonian characteristics and blood is considered to contain a homogenous suspension of nanoparticles. Vogel’s model is employed to simulate the variation of blood viscosity as a function of temperature. The governing equations are an extension of the Navier-Stokes equations with linear Boussinesq’s approximation and Buongiorno’s nanoscale model (which simulates both heat and mass transfer). The conservation equations are normalized by employing appropriate non-dimensional variables. It is assumed that the maximum height of the stenosis is small in comparison with the radius of the artery and furthermore that the radius of the artery and length of the stenotic region are of comparable magnitude. To study the influence of vessel geometry on blood flow and nano-particle transport, variation in the design and size of the stenosis is considered in the domain. The transformed equations are solved numerically by means of the finite element method based on the variational approach and simulated using the FreeFEM++ code. A detailed grid-independence study is included. Blood flow, heat and mass transfer characteristics are examined for the effects of selected geometric, nanoscale, rheological, viscosity and magnetic parameters i.e. stenotic diameter (d), viscoelastic parameter (), thermophoresis parameter (Ni), Brownian motion parameter (Nb) and magnetic body force parameter (M) at the throat of the stenosis and throughout the arterial domain. The velocity, temperature and nanoparticle concentration fields are also visualized through instantaneous patterns of contours. An increase in magnetic and thermophoresis parameters is found to enhance the temperature, nanoparticle concentration and skin-friction coefficient. Increasing Brownian motion parameter is observed to accelerate the blood flow. Narrower stenosis significantly alters the temperature and nano-particle distributions and magnitudes. The novelty of the study relates to the combination of geometric complexity, multi-physical nanoscale and thermomagnetic behaviour and also the simultaneous presence of bio-rheological behaviour (all of which arise in actual cardiovascular heat transfer phenomena) in a single work with extensive visualization of the flow, heat and mass transfer characteristics. The simulations are relevant to diffusion of nanodrugs in magnetic targeted treatment of stenosed arterial disease.