MHD Flow and Heat Transfer Analysis in Wire Coating Process Using Elastic-Viscous Fluid

The most important plastic resins used for wire coating are Polyvinyl Chloride (PVC), Nylon, Polysulfone and Low-high density polyethylene (LDPE / HDPE). In this article,the coating process is performed using elastic-viscous fluid as a coating material for wire coating in a pressure type coating die. The elastic-viscous fluid is electrically conducted in the presence of an applied magnetic field. The governing non-linear equations are modeled and then solved analytically by utilizing an Adomian decomposition method (ADM). The convergence of the series solution is established. The results are also verified by Optimal Homotopy Asymptotic Method (OHAM). The effect of different emerging parameters such as non-Newtonian parameters α and β, magnetic parameter M and the Brinkman number Br on solutions (velocity and temperature profiles) are discussed through several graphs. Additionally, the current result also compares with the published work already available in the literature.


Introduction
Studying the boundary layer behavior of a viscoelastic fluid on a continuous stretching surface, it is important for the analysis of the extrusion of the polymer, stretching of plastic films, optical fibers and cables.The importance in industrial process applications has raised significant interest from researchers for the study of viscoelastic fluid flow and heat transfer in fiber or wire coating process.The metal coating is an industrial process for the supply of insulation, environmental safety, mechanical damage and protect against signal attenuation.The simple and appropriate process for wire coating is the coaxial extrusion process that operates at the maximum speed of pressure, temperature and wire drawing.This produces higher pressure in the particular region resulting into strong bond and rapid coating.Several studies like, Han and Rao [1], Nayal [2], Caswell [3] and Ticker [4] have focused on the co-extrusion process in which the fibers or wires are drawn inside the molten polymer filled in a die.
Wire coating provides protection against mechanical damage and penetration of moisture in microscopic defects on the surface of the wire.In coating of the wire, the rate of wire drawing, temperature and the quality of materials are important parameters to be considered in the wire coating process.Different types of fluids are used for wire and fiber optic coating which depends upon the geometry of die, fluid viscosity, temperature of the wire and that of molten polymer.Wire coating analysis has a rich literature.For instance, the power law fluid model was used by Akter et al. [5,6] for wire coating.Third grade fluid was used for wire-coating by Siddiqui et al. [7].Fenner et al. [8] investigated the wire coating in a pressure type coating die.Unsteady second grade fluid with the oscillating boundary condition was investigated by Shah et al. [9,10] for wire coating.The same author discussed the third grade fluid for wire coating.
Interest in heat transfer in non-Newtonian fluids have significantly increased the use of non-Newtonian fluids perpetuated through various industries, including processing of polymers and electronics packaging.The heat transfer analysis is significant for the technology and advancement of science and up to date instruments such as compact heat exchangers, laser coolant lines and microelectro-mechanical systems (MEMS).A comprehensive survey of the literature is thus impractical.
However, some studies are listed here to provide a starting point for wider research literature.Shah et al. [12] studied wire-coating with a temperature varying linearly.Mitsoulis [13] has studied the flow of wire-coating with heat transfer.The heat transfer problem corresponding fully developed pipe and PTT fluid flow channels was also studied by Oliveira and Pinho [14].
The post-treatment of wire coating analysis also studied by many researchers [16].Wagner et al. [17] investigated the wire coating with the effect of die design.Numerical solution for wire coating analysis using a Newtonian fluid was investigated by Bagley and Storey [18].Oliveira et al. [19] investigated PTT fluid flow in a pipe and fully developed channel and gave an analytical results for velocity and stress components.Shah et al. [20] studied the elastic-viscous fluid for wire analysis in a pressure type coating die.
The technological and industrial applications of non-Newtonian fluids, recent researchers give more attention to these fluids such as blood, soap solutions, cosmetics, paint thinners, crude oils, sludge, etc. Magneto-hydrodynamic (MHD) addresses the electrically conductive fluid flows in the existence of a magnetic field.Researchers have devoted considerable attention to the study of MHD flow problems focusing on non-Newtonian fluids because of its broad applications in the fields of engineering and industrial manufacturing.Some examples of these areas are energy generators MHD, melting of metals by the application of a magnetic field in an electric furnace, the cooling nuclear reactors, plasma studies, the use of non-metallic inclusions to the purification of molten metals, extractions of geothermal energy, etc. Abel et al. [21] studied the variation of MHD on a viscoelastic fluid on a stretching area.Sarpakaya [22] was the pioneer who at first investigated non-Newtonian fluid in the presence of a magnetic field.Subhas et al. [23] investigated the MHD fluid and heat transfer analysis to the Upper Convected Maxwell fluid examined the magnetohydrodynamic (MHD) effects.Chen [24] studied an analytical solution of MHD flow of a viscous fluid with thermal effect.Akbar et al. [25] studied Eyring-Power fluid using a stretching sheet and examined that the elastic-viscous parameter and MHD have decelerated effect on velocity field.Mabood et al .[26] investigated the nano fluid using a non-linear stretching sheet in the presence of MHD effect.Vijendra et al .[27] investigated the MHD Maxwell fluid and heat transfer analysis with variable thermal conductivity.Analytical solution was obtained for MHD flow of Upper Conveted-Maxwell fluid by Hayat et al. [28].The same author also studied two-diemensional flow of Maxwell fluid on a permeable plat in [29].More considerable work on MHD can also be seen in literature [30][31][32].
A survey of literature indicates that much attention is given to elastic-viscous, especially from polymer industry (polymer melts), particular used for wires and optical fiber coating.Being inspired from such practical applications, several authors discussed the elastic-viscous fluid flow.Hayat et al. [33] investigated fluid flow of an elastic-viscous.Ellahi et al. [34] gave the exact solution of such fluid with the conditions of non-linear slip.Bari et al [35] elastic-viscous fluid in convergent channel.Ellahi et al. [36] gave an analytical solution of elastic-viscous fluid.Recently heat transfer and fluid-structure interactions at microscales are being actively studied theoretically and numerically [37][38].
In present article, the work of Shah et al. [20] is extended by utilizing the additional effects of MHD and heat transfer.To the best of our knowledge, no one has considered the magnetohydrodynamic flow and heat transfer in wire coating analysis using elastic-viscous fluid as a coating material in a pressure-type coating die.Analytical solution of the resulting nonlinear Ordinary Differential Equation is obtained through ADM [38][39][40][41][42] and a comparison is made with OHAM [43][44][45][46] for various values of the parameters.Effect of the physical parameters on the solution is shown and discussed by using graphs of numerical values of different quantities of interest.

Modeling of the Problem
The principle of the flow geometry is schematically shown in figure 1.As shown in figure 1 the wire of radius is dragged with velocity through a pressure-type coating die of length and radius .The coordinate system is taken at the center of the wire, in which is taken perpendicular to the flow direction and − axis is along the flow.Here and represents the wire and die temperature respectively.A constant pressure gradient is acted upon the fluid direction and magnetic field of strength transversely along the axial direction.Due to small magnetic Reynold number the induced magnetic field is negligible, which is also a valid assumption on a laboratory scale.
The design of the coating die is more important because it affects the final product quality.In the current study, a pressurized coating die is considered.The impact of surrounding temperature is considered for optimal performance.
The coating die is filled with an elastic-viscous fluid.The flow is considered incompressible, laminar, axisymmetric and steady.With the assumptions mentioned above, the velocity of the fluid, stress tensor and temperature field are taken as ( ) ( ) Subject to the boundary conditions at and 0 at at and at .
For an elastic-viscous fluid, the stress tensor is: In the above η is the viscosity of the fluid, D Dt the material derivative, S the extra stress tensor, A the Rivlin-Ericksen tensor and ( ) In the above equation denotes the transpose of the matrix.
It should be noted that the model ( 4) contains several other models as: For Newtonian fluid model all 1 7 0 γ − γ = .

•
For Johnson-Segalman model all 5 The basic governing equations for incompressible flow are the continuity, momentum and energy equations are given by: .0, u ∇ = (7) .T J B, In the above equations u , ρ , T , p c , / D Dt , k , Θ , are the velocity of the fluid, density of the fluid, shear stress,specific heat, material derivative, thermal conductivity, temperature and velocity gradient respectively.
The interaction of current and magnetic field produces a body force J B × as given in Eq. ( 8).The electrostatic force produced due to charge density is negligible and we only consider the applied magnetic field 0 B normal to the flow direction.
In the above frame of reference the body force becomes.( ) In the above equationα , β are the material parameters, M the magnetic parameter, δ and the radii ratio and Br is the Brinkman number.

Solution of the Modeled Problem
To solve Equations ( 14)-( 17), we apply the Adomian decomposition method [38][39][40][41][42].The detail of the method is given in appendix, while the zero and first order solutions for the velocity field and temperature distributions are: ( ) The second component is too large, so we only give the graphical representation upto the second order approximation.
Collecting the results, we have the velocity field and temperature distribution up to a first order approximation obtained by ADM as follows: ( )

Analysis of the Results
The subject of this section is to explore the effect of different emerging parameters such as non-Newtonian parameters α and β , magnetic parameter M and the Brinkman number Br on solutions (velocity and temperature profiles) are discussed through several graphs.The convergence of the method and comparison with published results is also established in this section.The convergence of the method is also necessary to check the reliability of the methodology.The convergence of the method is given in Tables 1-3 by assigning numerical values to the physical parameters of interest given in the appendix-D.From this we concluded that for different values of material parameters we get the convergence of the series solutions.The convergence of method can also be observed from the relative error of OHAM and ADM as given in the appendix-D in Table 4. Further, Table 5 in appendix-D also shows the comparison of present and published work by taking the magnetic parameter tends to zero and good agreement is found between the present and published work.
To give a clear overview of the physical problem, Figures 2-8 are sketched.
The impact of magnetic parameter M on the velocity profile is displayed in Figure 2. It is observed that the velocity profile decreases via larger M .Physically by increasing the magnetic parameter the Lorentz force increases.Much resistance is occurring in the motion of the fluid which reduces the velocity of the fluid.The effect of magnetic parameters M and the material parameter β on the velocity profile is shown in figure 3. Larger values of the magnetic parameter increase the Lorentz force which resists the motion of the fluid and thus velocity of the fluid reduce.Figure 4 depicts the impact of of α on the velocity profile.It is remarkable to note that the parameter α has accelerated effect on the velocity profiles.Physically by increasing α would lead to reduce the friction forces and thus fluid moves with greater velocity.The effect of material parameter α and the non-Newtonian parameter β on the temperature profiles is shown in Figure 7 and 8 in the presence and absence of magnetic field, respectively.It is observed that the material parameter α decreases the temperature profile while the non-Newtonian parameter β accelerates the temperature profile significantly, both in the presence and absence of magnetic field, at all the points of the melt polymer so as to make the process faster.

Conclusion
In this work, the wire coating analysis and the heat transport phenomena corresponding to the steady flow has been studied.The fluid is electrically conducted in the presence of applied magnetic field.The problem is first modeled and then solved by utilizing ADM.The result is also verified by OHAM.Additionally, the convergence of the method is also verified.The effect of different emerging parameters on the solution is discussed.The material parameter α and the magnetic parameter M have decelerated effect on the velocity profile.The velocity profile increases with increasing β .The temperature profile increases with increases magnetic parameter M , Brinkman number Br and the material parameter β and decreases with increasingα .At the end, the present is also compare with published results already available in the literature and good agreement is found.
The function ( ), The series solution of ( ) w r using ADM we have, In view of Adomian Polynomials the nonlinear term ( ) 29) can be expanded as ( ) In view of Eq. ( 29), Eq. ( 30) can expand as ( ) ( ) ( )  (31) To determine the series components 0 1 2 3 , , , w w w w …, it should be noted that ADM suggest that ( ) f r in fact describe the zeroth component 0 w .
The recursive relation is defined as: ( ) ( ) ( ) ( ) ( ) ( ) And so on.For estimated solution, ( , ) r p ϕ is expanding with respect to p by using Taylor series.
By using Eqs.( 39) and (40) into Eq.( 37), and equating the coefficient of like power of p , the zero order problem is given in Eq. (38).The first and second order problems are as follows: The general The convergence of Eq. ( 44) depends upon the auxiliary constant and order of the problem.If it converges at , 1 = p one has: In view of Eqs.(45) and Eq. ( 36) we have: Many methods such as Ritz Method, Method of Least square, Collection and Galerkin's method are used for the solution of auxiliary constants.

Figure 1 .
Figure 1.Pressure type coating die for wire coating analysis.

Figure 3 .Figure 4 .
Figure 3. Velocity profile for various values of β when
is the non-zero auxiliary function and ( , ) r p ϕ is a unknown function.Taking 0 p = , the homotopy in Eq. (37) gives the zero component solution i.e.
equation and are constant values taking from the domain of the problem.

Table A1 .
applied this method for solving highly nonlinear boundary value problem.Convergence of the method for Preprints (www.

Table A2 .
Convergence of the method for

Table A3 .
Convergence of the method for

Table A4 .
Numerical comparison of OHAM and ADM when

Table A5 .
[20]city comparison of the present work with published work[20]when