Heat Mass Transfer (2015)51:1061-1066 D0I10.1007/s00231-014-1477-z CrossMark ORIGINAL Boundary layer flow past a stretching sheet with fluid-particle suspension and convective boundary condition Reddy Gorla Abstract The steady two-dimensional boundary Mass of the dust particles the bo the sheet b ching sm the fuid (K a hot fluid is Hot Auid te ure (K) Temperature at large distance(K) T Temperature of the dust Particles(K) numerically by a Runge-Kutta-Fehlberg fourth-fifth order Velocity components of the fluid along x and y method (RKF45 Method)with the help of MAPLE.The directions (ms-) effects of convective Biot number,fluid particle interaction Velocity components of the dust particle alongx parameter,and Prandtl number on the heat transter charac andy directions(ms-1) teristics are disc sed.It is found that the temperature of x.y Cartesian co-ordinates (m) and dus ihed and pre mpara excellen Density of the fuid (k Density of the dust particles (kgm) Li过t of symbols Relative density Bi Biot number Similarity variable(m) Stretching rate Dimensionless fluid temperature Specifie heat of the particles Dimensionless dust phase temperature s Specific heat of the fluid (Jkg-K) Viscosity of the fluid(Ns m-) ess stream function Relaxation time of the particle phase Thermal re axation time Density ratio The tivity (Wm-K) 1 Introduction G.K.Ramesh Boundary laver flow and heat transfer over a stretched sur face has received considerable attention in recent years. The problem has scientific and engineering applications such as aerodynamic extrusion of plastic sheets and fibers B.J.Gire ineering.Cleveland State University.Cleveland. drawing,annealing and tinning of copperwire,paper pro OH44U5 USA duction.crystal growing and glass blowing.Such applica- c-mail:r.gorla@csuohio.cdu tions involve cooling of a molten liquid by drawing it into a Springer
1 3 Heat Mass Transfer (2015) 51:1061–1066 DOI 10.1007/s00231-014-1477-z ORIGINAL Boundary layer flow past a stretching sheet with fluid‑particle suspension and convective boundary condition G. K. Ramesh · B. J. Gireesha · Rama Subba Reddy Gorla Received: 23 December 2013 / Accepted: 15 December 2014 / Published online: 8 January 2015 © Springer-Verlag Berlin Heidelberg 2015 m Mass of the dust particles Pr Prandtl number T Temperature of the fluid (K) Tf Hot fluid temperature (K) T∞ Temperature at large distance (K) Tp Temperature of the dust Particles (K) u, v Velocity components of the fluid along x and y directions (ms−1 ) up, vp Velocity components of the dust particle along x and y directions (ms−1 ) x, y Cartesian co-ordinates (m) Greek symbols β Fluid particle interaction parameter ρ∞ Density of the fluid (kg m−3 ) ρp Density of the dust particles (kg m−3 ) ρr Relative density η Similarity variable (m) θ Dimensionless fluid temperature θp Dimensionless dust phase temperature μ Viscosity of the fluid (Ns m−2 ) τ Relaxation time of the particle phase L0 Thermal relaxation time ω Density ratio 1 Introduction Boundary layer flow and heat transfer over a stretched surface has received considerable attention in recent years. The problem has scientific and engineering applications such as aerodynamic extrusion of plastic sheets and fibers, drawing, annealing and tinning of copperwire, paper production, crystal growing and glass blowing. Such applications involve cooling of a molten liquid by drawing it into a Abstract The steady two-dimensional boundary layer flow of a viscous dusty fluid over a stretching sheet with the bottom surface of the sheet heated by convection from a hot fluid is considered. The governing partial differential equations are transformed into ordinary differential equations using a similarity transformation, before being solved numerically by a Runge–Kutta–Fehlberg fourth-fifth order method (RKF45 Method) with the help of MAPLE. The effects of convective Biot number, fluid particle interaction parameter, and Prandtl number on the heat transfer characteristics are discussed. It is found that the temperature of both fluid and dust phase increases with increasing Biot number. A comparative study between the previous published and present results in a limiting sense is found in an excellent agreement. List of symbols Bi Biot number c Stretching rate cs Specific heat of the particles cp Specific heat of the fluid (J kg−1 K) f Dimensionless stream function F Particle velocity component hf Heat transfer coefficient K Stokes’ resistances k Thermal conductivity (Wm−1 K) G. K. Ramesh · B. J. Gireesha Department of Studies and Research in Mathematics, Kuvempu University, Shankaraghatta, Shimoga 577 451, Karnataka, India e-mail: gkrmaths@gmail.com B. J. Gireesha · R. S. R. Gorla (*) Mechanical Engineering, Cleveland State University, Cleveland, OH 44115, USA e-mail: r.gorla@csuohio.edu
1062 Heat Mass Transfer (2015)51:1061-1066 cooling system.In drawing the liquid into the cooling sys- lunar surface erosion by the exhaust of a landing vehicle and tem it is sometimes stretched as in the case of a polymer dust entrainment in a cloud formed during a nuclear explo- extrusion process.The fluid mechanical properties s desired sion.Chakrabarti 19]analyzed the boundary layer formed for the outcome of such a process depends mainly on the by a dusty gas.Datta and Mishra[1]studied the two phase 0 ue to th heat is ne to d th dusty s at the desired nr operties for the outcome.In view of the applications Sakiadis [was the first mathematician who of Datta and Mishra [14]and studied the hydrodynamic studied boundary layer flow over a stretched surface mov stability of a particle-laden flow over a flat plate boundary ing with a constant velocity.Crane [2]initiated the analyti- eoodtetoaswc layer.Palani and Ganesan [17]studied heat transfer effects dusty gas flow pa mi-innnite transfer studie dusty d When modeling the boundary laver flow and fer of stretching surface,the boundary conditions that are stretching sheet with the effect of suction recently ramesh usually applied are either a specified surface temperature et al.[21]investigate the MHD flow of a dusty fluid near layer flow and heat tra on-unifor rce e epen d wh ng s PST onian heat o of the c the dusty fluid behavior on boundary la n in there is Neu flow and hea the surface.Newtonian heating occurs in many important transfer over a stretching sheet with convective boundar engineering devices,for example,inheat exchangers,where condition.Appropriate similarity transformations are used the conduction in a solid tubewall is greatly influenced by to reduce the govering partial differential equations into a the convection in the fluid f wing over it.On the basis o set of nonlinear ordinary differential cquations.The resul he ea on Aziz n The with ctive heat transfer associated with the hot fluid on the lower surface in detail. of the plate is proportic onal tox Makinde [5]extend the work of Aziz [4]by including hydromagnetic 1.1 Flow analysis of the problem icad mi Ola Consider er a ary condition on the laminar boundary layer flow a stretching sheet.The sheet is coinciding with the plan plate.Ishak et al 7]obtained the dual solution for lamina y=0,with the flow being confined toy>0Two equal and boundary layer flow over a moving plate in a moving fluid opposite forces are applied along the xaxis,so that the with con ec ive surface boundary condition in the pres sheet is stretched,keeping the origin fixed.The tempera of the radi Apart fro these var of shee s the res ich ce [8-1cond All the above investigations are concerned with single in equilibrium and are assumed to be at rest.The dust or phase flows.In nature,the fluid in pure form is rarely avail- particle-phase volume fraction is assumed to be small and ble.Air and water contains impurities such as dust particles suspension is assumed to be dilute in the senses that nd efore the study ase now hich The dust particles sp toof the pe al f i niform size and the fow Under the fo mptions the basic two etc.Other ortant applications involving dust particles dimensional boundary laver equations of motion for clean in boundary layers include soil salvation by natural winds. fluid and dust fluid with usual notation are [see20]. Springer
1062 Heat Mass Transfer (2015) 51:1061–1066 1 3 cooling system. In drawing the liquid into the cooling system it is sometimes stretched as in the case of a polymer extrusion process. The fluid mechanical properties desired for the outcome of such a process depends mainly on the rate of cooling and the stretching rate. It is important that a proper cooling liquid is chosen and flow of the cooling liquid due to the stretching sheet is controlled so as to arrive at the desired properties for the outcome. In view of these applications Sakiadis [1] was the first mathematician who studied boundary layer flow over a stretched surface moving with a constant velocity. Crane [2] initiated the analytical study of boundary layer flow due to a stretching sheet. Grubka and Bobba [3] carried out heat transfer studies by considering the power-law variation of surface temperature. When modeling the boundary layer flow and heat transfer of stretching surface, the boundary conditions that are usually applied are either a specified surface temperature or a specified surface heat flux. However, there is boundary layer flow and heat transfer problems in which the surface heat transfer depends on the surface temperature. This situation arises in conjugate heat transfer problems and when there is Newtonian heating of the convective fluid from the surface. Newtonian heating occurs in many important engineering devices, for example, inheat exchangers, where the conduction in a solid tubewall is greatly influenced by the convection in the fluid flowing over it. On the basis of above discussions and application Aziz [4] investigated the heat transfer problems for boundary layer flow concerning with a convective boundary condition and exhibit that similarity solution it is possible if the convective heat transfer associated with the hot fluid on the lower surface of the plate is proportional to x−1/2. Makinde [5] extend the work of Aziz [4] by including hydromagnetic field and mixed convection heat and mass transfer over a vertical plate. Olanrewaju et al. [6] examined the combined effects of internal heat generation and a convective boundary condition on the laminar boundary layer flow over a flat plate. Ishak et al. [7] obtained the dual solution for laminar boundary layer flow over a moving plate in a moving fluid with convective surface boundary condition in the presence of thermal radiation. Apart from these works, various aspects of flow and heat transfer of viscous fluid over a stretching surface with convective boundary condition were investigated by many researchers (see [8–13]). All the above investigations are concerned with single phase flows. In nature, the fluid in pure form is rarely available. Air and water contains impurities such as dust particles and foreign bodies. Therefore the study of two-phase flows in which solid spherical particles are distributed in a clean fluid are of interest in practical applications such as petroleum industry, purification of crude oil, physiological flows, etc. Other important applications involving dust particles in boundary layers include soil salvation by natural winds, lunar surface erosion by the exhaust of a landing vehicle and dust entrainment in a cloud formed during a nuclear explosion. Chakrabarti [19] analyzed the boundary layer formed by a dusty gas. Datta and Mishra [14] studied the two phase boundary layer flow over a semi-infinite flat plate in the region of high and small slip velocities. Evgeny and Sergei [15] discussed the stability of a dusty gas laminar boundary layer on a flat plate. Further Xie et al. [16] extended work of Datta and Mishra [14] and studied the hydrodynamic stability of a particle-laden flow over a flat plate boundary layer. Palani and Ganesan [17] studied heat transfer effects on dusty gas flow past a semi-infinite inclined plate. Agranat [18] studied dusty boundary layer flow and heat transfer, with the effect of pressure gradient. Vajravelu and Nayfeh [20] analyzed the hydromagnetic flow of dusty fluid over a stretching sheet with the effect of suction. Recently Ramesh et al. [21] investigate the MHD flow of a dusty fluid near the stagnation point over a permeable stretching sheet with non-uniform source/sink and studied for two types of heating process PST and PHF cases. The present study has been undertaken in order to study the dusty fluid behavior on boundary layer flow and heat transfer over a stretching sheet with convective boundary condition. Appropriate similarity transformations are used to reduce the governing partial differential equations into a set of nonlinear ordinary differential equations. The resulting equations are solved numerically using the fourth-fifth order Runge–Kutta method with the help of Maple. The effect of variations of several pertinent emerging parameters on the flow and heat transfer characteristics is analyzed in detail. 1.1 Flow analysis of the problem Consider a steady two dimensional laminar boundary layer flow of an incompressible viscous dusty fluid over a stretching sheet. The sheet is coinciding with the plane y = 0, with the flow being confined to y > 0 Two equal and opposite forces are applied along the x-axis, so that the sheet is stretched, keeping the origin fixed. The temperature of sheet surface (to be determined later) is the result of a convective heating process which is characterized by a temperature Tf and a heat transfer coefficient hf . Far from the surface, both the fluid and the dust particles are in equilibrium and are assumed to be at rest. The dust or particle-phase volume fraction is assumed to be small and the suspension is assumed to be dilute in the senses that inter particle collision is neglected. The dust particles are assumed to be spherical in shape and uniform in size and number density of these are taken as a constant throughout the flow. Under the foregoing assumptions the basic two dimensional boundary layer equations of motion for clean fluid and dust fluid with usual notation are [see 20]
Heat Mass Transfer (2015)51:1061-106 1063 Substituting (8)into(1)(7).we obtain the following non- quations: (+）=驴+-n m+开"-(f2+BHIF-的=0 (10) (2)GF+(F)2+F-f1=0. 1) 0+,警=华u- (3) GG+BU+G]=0. (12) 驶+费=-w以 HF+HG+GH'=0. (13) (4) 0”+0+26,-1=0 (14) 2w+aw-0 (5) Gp+LoB[@p -0]=0. (15) (识+）=票+-n where a prime denotes differentiation with r (6) phsee the uid particle interaction param 股+要=-n eter and p=Pp is the relative density.Pr=vla is the (7) Prandtl number,Bi=(v/a)h/is the Biot number and of will take the form. and m are the co-efficient of viscos ity of the uid,density of the uid,mass of dust particles f=0.f=1. '=-Bi(1-0)atn=0. per unit volume of the fluid.mass of the dust particle.K f→0.F→0.G→-f,H→w is the Stokes'resistance (drag co-efficient)respectively. 8→0.8。→0a5n→0o (16) dust ice are the specific heat o If 8- the relaxation time of the of dust particle.is the thermal conductivity.In deriving these equations,the drag force is f(n=1-e- (17) considered for the interaction between the fluid and dust The wall shear stress is given by: phases. The boundary conditions of the problem are ==0 (18) u=Uw(x).v=0. -=-n aty=0 The friction factor is given by (8) Co=pU =-2Re1/2f"(0) (19) u→0，p→0.p→，pp→ope The surface heat transfer rate is given by: T→Te,Tp→Too as y→o stretching she ==0 (20) h is th heat y tauo. To convert the The local Nusselt number may be written as: ing equations into a set of similarity equations,now we introduce the following transformation as, )=(0) (21) 2 Results and discussion Ty-Too ==GA=h= ntial Eqs.(1(15)subjec Tr-To 16 9 using Runge-Kutta-Fehlberg fourth-fifth order method Springer
Heat Mass Transfer (2015) 51:1061–1066 1063 1 3 where (u,v) and (up,vp) are the velocity components of the fluid and dust particle phases along x and y directions respectively. μ, ρ∞, ρp and m are the co-efficient of viscosity of the fluid, density of the fluid, mass of dust particles per unit volume of the fluid, mass of the dust particle, K is the Stokes’ resistance (drag co-efficient) respectively. T and Tp is the temperature of the fluid and temperature of the dust particle, cp and cs are the specific heat of fluid and dust particles, γT is the temperature relaxation time, τ is the relaxation time of the of dust particle, k is the thermal conductivity. In deriving these equations, the drag force is considered for the interaction between the fluid and dust phases. The boundary conditions of the problem are where Uw(x) = cx is the stretching sheet velocity, c > 0 is stretching rate, ω is the density ratio, Tf is the hot fluid temperature and hf is the heat transfer coefficient. To convert the governing equations into a set of similarity equations, now we introduce the following transformation as, (1) ∂u ∂x + ∂v ∂y = 0, (2) ρ∞ u ∂u ∂x + v ∂u ∂y = µ ∂2u ∂y2 + ρp τ (up − u), (3) up ∂up ∂x + vp ∂up ∂y = ρp τ (u − up), (4) up ∂vp ∂x + vp ∂vp ∂y = 1 τ (v − vp), (5) ∂ ∂x (ρpup) + ∂ ∂y (ρpvp) = 0, (6) ρ∞cp u ∂T ∂x + v ∂T ∂y = k ∂2T ∂y2 + csρp γT (Tp − T), up (7) ∂Tp ∂x + vp ∂Tp ∂y = − 1 γT (Tp − T), (8) u = Uw(x), v = 0, −k ∂T ∂y = hf(Tf − T) at y = 0 u → 0, up → 0, vp → v, ρp → ωρ∞, T → T∞, Tp → T∞ as y → ∞, (9) u = cxf ′ , v = −√vc f , η = Uw νx y, θ = T − T∞ Tf − T∞ up = cxF, vp = √vc G, ρr = H, θp = Tp − T∞ Tf − T∞ Substituting (8) into (1)–(7), we obtain the following nonlinear ordinary differential equations: where a prime denotes differentiation with respect to η and ρr = ρp/ρ∞, τ = 1/K is the relaxation time of the particle phase, β = 1/cτ is the fluid particle interaction parameter and ρr = ρp/ρ is the relative density, Pr = ν/ α is the Prandtl number, Bi = (v/a)1/2hf /k is the Biot number and L0 = τ/γT is the temperature relaxation parameter. The boundary conditions defined as in (8) will take the form, If β = 0, the analytical solution of (10) was given by Crane [2] as The wall shear stress is given by: The friction factor is given by: The surface heat transfer rate is given by: The local Nusselt number may be written as: 2 Results and discussion The nonlinear ordinary differential Eqs. (10)–(15) subject to the boundary conditions (16) are solved numerically using Runge–Kutta–Fehlberg fourth-fifth order method f (10) ′′′ + ff ′′ − (f ′ ) 2 + βH[F − f ′ ] = 0, GF (11) ′ + (F) 2 + β[F − f ′ ] = 0, GG (12) ′ + β[f + G] = 0, HF + HG (13) ′ + GH′ = 0, (14) 1 Pr θ′′ + f θ′ + 2Hβ 3 [θp − θ] = 0 Gθ (15) ′ p + L0β[θp − θ] = 0, (16) f = 0, f ′ = 1, θ′ = −Bi(1 − θ ) at η = 0, f ′ → 0, F → 0, G → −f , H → ω, θ → 0, θp → 0 as η → ∞. f(η) = 1 − e (17) −η. τw = µ (18) ∂u ∂y |y = 0 Cfx = (19) 2τw ρU2 w = −2Re−1/2 x f ′′(0) qw = k (20) ∂T ∂y |y = 0 (21) Nux = qw k(Tf − T∞) = −Re1/2 x θ′ (0)
1064 Heat Mass Transfer (2015)51:1061-1066 R1 Table 1 Co rature gradient -0(0)in Wang [22] Errors Bf=I0,P=30 091 0911 0910 0.00 1805 180 1804 0001 30 0.4 B=0.0l.0.1.1.0 3.353 3.353 3352 0.00 706.462 6.462 6.457 0.008 2 (RKF45 Method).To solve these equations we adopted n are M which is descnibe ed by those reported by Wang 22]and Gorla and Sidawi 23] in Table I for special case of the present problem and an excellent agreement between the results is found.Further. 0.6 the impact of some important physical parameters on the 0.5 surface par B-10,-30 all tempe ty,surface heat trans nal wa 03 (0).resr analyzed from Table.It may 0.2 B-001.0L.10 be noted that the effect of increasing fluid particle inter action parameter.B is to decrease the wall shear stress f"(0).surface heat transfer rate -0'(0)and increase the erature proportional 3 In order to study the behaviour of velocity (f,F)and Effect of on velocity and temperature distribution (ds temperature ()fields for dusty fluid,a comprehensive numerical computation is carried out for various values of the parameters that describe the flow characteristics.and the results are reported in terms of Figs. ( and and ultimately as0,the fluid phase and dust phase By analyzing the g als that the will be the same theis to decrease the velocity and temperature dis The effect of Prandtl number Pr on both fluid and dust tribution.This is due to the fact that for a large value of B tat th uid-ph ons are displayed in Fig..I the relaxation time of the dust particle decreases.Figure 2 represents the effect of B on the velocity and temperature which implies momentum boundary layer is thicker than dust phas ca tha the thermal boundary layer.This is due to the fact that for ith higher Prandtl number.fluid has a relatively low thermal th ariation can he found in fluid phase and when comnar diffusivity,which reduces conduction.We note that,the velocity to dust phase.Further observation shows that if the dust Pr gives nc ndary layer Tle2Coputiog B P fo FO) 0.01 -1.0014 0.0099 -0.5380 04610 0.0027 0.5 3 -1.0048 0.3402 -0.5383 0.4616 0.1403 1.0 3 -1.0067 0.5216 -0.5385 0.4614 0.263 Springer
1064 Heat Mass Transfer (2015) 51:1061–1066 1 3 (RKF45 Method). To solve these equations we adopted symbolic algebra software Maple which is described in [4]. The accuracy of the employed numerical method is tested by direct comparisons with the values of θ′ (0) with those reported by Wang [22] and Gorla and Sidawi [23] in Table 1 for special case of the present problem and an excellent agreement between the results is found. Further, the impact of some important physical parameters on the friction factor, surface particle velocity, surface heat transfer rate, wall temperature and dust phase wall temperature which are proportional to f ′′(0), F(0), −θ′ (0), θ (0) and θp(0), respectively, may be analyzed from Table 2. It may be noted that the effect of increasing fluid particle interaction parameter, β is to decrease the wall shear stress f ′′(0), surface heat transfer rate −θ′ (0) and increase the surface particle velocity, wall temperature and dust phase wall temperature proportional to F(0), θ (0) and θp(0), respectively. In order to study the behaviour of velocity (f ′ , F) and temperature (θ, θp) fields for dusty fluid, a comprehensive numerical computation is carried out for various values of the parameters that describe the flow characteristics, and the results are reported in terms of Figs. 1 and 2. Figure 1 exhibits the velocity and temperature profiles (fluid phase) for several values of fluid-particle interaction parameter β. By analyzing the graphs it reveals that the effect increasing the β is to decrease the velocity and temperature distribution. This is due to the fact that for a large value of β the relaxation time of the dust particle decreases. Figure 2 represents the effect of β on the velocity and temperature (dust phase) distribution. It is noticed that the velocity and temperature increases with the increase of β. From these figures we noted that when increasing the values of β small variation can be found in fluid phase and when compare to dust phase. Further observation shows that if the dust is very fine, that is, mass of the dust particles is negligibly small, then the relaxation time of dust particle decreases, and ultimately as τ → 0, the fluid phase and dust phase will be the same. The effect of Prandtl number Pr on both fluid and dust phase temperature distributions are displayed in Fig. 3. It can be seen that the fluid-phase temperature and dust-phase temperature decrease with increase of Prandtl number, which implies momentum boundary layer is thicker than the thermal boundary layer. This is due to the fact that for higher Prandtl number, fluid has a relatively low thermal diffusivity, which reduces conduction. We note that, the Pr gives no influence to the development of the velocity boundary layer, which is clear from Eqs. (10)–(13). Table 1 Comparison results for the temperature gradient −θ′(0) in the case of L0 = 1, β, ω = 0 and Bi = 1,000 Pr Wang [22] Gorla and Sidawi [23] Present study −θ′(0) Errors 2 0.911 0.911 0.910 0.001 7 1.895 1.890 1.894 0.001 20 3.353 3.353 3.352 0.001 70 6.462 6.462 6.457 0.008 Table 2 Computations of f″(0), F(0), θ′(0), θ(0) and θp(0) for different values of Biot number (Bi) with ω = 0.02 β Pr Bi f″(0) F(0) θ′(0) θ(0) θp(0) 0.01 3 1 −1.0014 0.0099 −0.5380 0.4619 0.0027 0.5 3 1 −1.0048 0.3402 −0.5383 0.4616 0.1403 1.0 3 1 −1.0067 0.5216 −0.5385 0.4614 0.2637 Fig. 1 Effect of β on velocity and temperature distribution (fluid phase) Fig. 2 Effect of β on velocity and temperature distribution (dust phase)
Heat Mass Transfer (2015)51:1061-106 1065 (0)for different value 三因 -0 0.1 0.0921 0.0789 0.0240 0.5 0.3499 0.3001 0.0912 ((4)e =1030,70 20 0.736 0.6317 0.1919 0.9145 0.810 0.246 1.04 0.892 0.2721 0.977 0.2970 633 .000 1.1646 09988 0.3035 Fig.3 Effect of Pr on temperature distribution 5.000 11657 000g7 0.3038 10000 1.1659 0.998 0.3038 100000 1.1660 0.999 0.3039 1.0 1.000.000 1.1660 0.9999 0.303 5.000.000 1.1660 0.9999 0.3039 0-1.0.Pm-3.0 We ed the gove et Bi.Pr Bi=0L.1.0.10 tics.Form the Table 3 it is found that when Bi in ses from 0.1 to 50.the heat transfer rate-).surface temperature function of both fluid (0)and dust (0)phases increase sig nifcantly.However,a further in rease in Br has only minor effect on the valu sof-0(0(0)a dp(0).When B ant change is observed for the Fig Effect of on temperature distribution A(0 Following are cnclusions drawn from the investigation: Figure 4 depict the variation in the temperature dis tribution of()and(for different values of Bi.It is Increase of fluid-particle interaction parameter reduces tempe (an ,(）incre the velocity and temperature distribution(fluid phase). the hermal bound f"(0)increase with the values of fuid particle inter layer thickne action parameter considered table 3 indicates that the heat ase of Biot number is to increase the thermal transfer rate increases with the Biot number Bi.Figures 1 boundary layer. 2.3 and 4.it is observed that the fluid phase velocity and are sin 1a o that or dust p city and temperature are higher References 3 Conclusions 1.Sakiadis BC (1961 In this paper.the of fluid partick 2.Crane LI (97 ove ng sheet nave a stretching sheet.Z Angew Math tive boundar othe development of the ther Bobba KM(1985)Heat tra mal boundary layer flow has been taken into consideration
Heat Mass Transfer (2015) 51:1061–1066 1065 1 3 Figure 4 depict the variation in the temperature distribution of θ (η) and θp(η) for different values of Bi. It is observed that temperature field θ (η) and θp(η) increases rapidly near the boundary by increasing Biot number (Bi). Form Table 2, we can see that the values of the friction factor, −f ′′(0) increase with the values of fluid particle interaction parameter considered. Table 3 indicates that the heat transfer rate increases with the Biot number Bi. Figures 1, 2, 3 and 4, it is observed that the fluid phase velocity and temperature fields are similar to that of dust phase and also the fluid phase velocity and temperature are higher than the dust phase values. 3 Conclusions In this paper, the heat transfer characteristics of a fluid particle suspension over a stretching sheet have been studied numerically. Different from previous investigations, the effect of convective boundary condition on the development of the thermal boundary layer flow has been taken into consideration. We discussed the effects of the governing parameters Biot number, Prandtl number and fluid particle interaction parameter Bi, Pr and β, respectively, on the heat transfer characteristics. Form the Table 3, it is found that when Bi increases from 0.1 to 50, the heat transfer rate −θ′ (0), surface temperature function of both fluid θ (0) and dust θp(0) phases increase significantly. However, a further increase in Bi has only minor effect on the values of −θ′ (0), θ (0) and θp(0). When Bi → ∞ (i.e., for large value), no significant change is observed for the values of −θ′ (0), θ (0) and θp(0). Following are brief conclusions drawn from the investigation: • Increase of fluid-particle interaction parameter reduces the velocity and temperature distribution (fluid phase), opposite effect can be seen in dust phase. • Increase of Prandtl number reduces the thermal boundary layer thickness. • Increase of Biot number is to increase the thermal boundary layer. Acknowledgments The authors wish to express their very sincere thanks to all the reviewers for their valuable comments and suggestions. References 1. Sakiadis BC (1961) Boundary layer behaviour on continuous solid surface. AIChE J 7(1):26–28 2. Crane LJ (1970) Flow past a stretching sheet. Z Angew Math Phys 21:645–647 3. Grubka LJ, Bobba KM (1985) Heat transfer characteristics of a continuous stretching surface with variable temperature. J Heat Transfer 107:248–250 Fig. 3 Effect of Pr on temperature distribution Fig. 4 Effect of Bi on temperature distribution Table 3 Computations of −θ′(0), θ(0) and θp(0) for different values of Biot number (Bi) with β = 0.5, Pr = 3.0 and ω = 0.02 Bi −θ′(0) θ(0) θp(0) 0.1 0.0921 0.0789 0.0240 0.5 0.3499 0.3001 0.0912 2.0 0.7365 0.6317 0.1919 5.0 0.9455 0.8108 0.2464 10 1.0442 0.8955 0.2721 50 1.1394 0.9772 0.2970 100 1.1526 0.9884 0.3004 500 1.1633 0.9976 0.3032 1,000 1.1646 0.9988 0.3035 5,000 1.1657 0.9997 0.3038 10,000 1.1659 0.9998 0.3038 100000 1.1660 0.9999 0.3039 1,000,000 1.1660 0.9999 0.3039 5,000,000 1.1660 0.9999 0.3039
Heat Mass Transfer (2015)51:1061-1066 4.DallSK)d nd l plate th Olan PO.Ar K(2)Intemal heat ity of a Dyn 2(1)conv 18 VM( .()The ction flow of a unifor ppl Math 20. the B nd Sak 21 wadi CS 2012)MHD fo 10.Makina OD,Azi 22.w 89)F 11.15hakA2010o rm Se rtical stretching surface s83-1820 i heat transfer convective boundary conditio 217-83784 laver in a dusty gas Springer
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