International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 132 Heat and mass transfer effect of chemically reactive fluid on flow over an accelerated vertical surface in presence of radiation with constant heat flux DR. ARPITA JAIN Head, Department of Mathematics, JECRC UDML College of Engineering, Kukus, Jaipur, Rajasthan, India E-mail*: arpita_252@rediffmail.com ABSTRACT. This paper aims to investigate the influence of chemical reaction and the IJOART combined effects of heat and mass transfer on laminar boundary layer flow over a moving vertical plate in presence of radiation with heat is supplied to the plate at constant rate. The governing equations for this investigations are solved analytically by Laplace-transform technique. Graph results are presented for temperature, concentration, velocity, skin friction, Nusselt number and Sherwood number. The effects of various parameters on flow variables are illustrated graphically and the physical aspects of the problem are discussed. KEY WORDS: Free convection, heat and mass transfer, chemical reaction, radiation, accelerated plate. 1. INTRODUCTION: The analysis of free convection flow near a vertical plate has been carried out as an important application in many industries. Numerous investigations are performed by using both analytical and numerical methods. The first exact solution of the NavierStokes equation was given by Stokes [1] and explains the motion of a viscous in- Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 133 compressible fluid past an impulsively started infinite horizontal plate in its own plane. This is known as Stokes’s first problem in the literature. If the plate is in a vertical direction and gives an impulsive motion in its own plane in a stationary fluid, then the resulting effect of buoyancy force was first studied by Sundalgekar [2] by Laplace transformation technique and the effects of heating or cooling of the plate by free convection cur- rents were discussed. Natural convection has been analyzed extensively by many investigators. Some of them are Revankar [3], Li et.al. [4]. Furthermore, the free convection flows together with heat and mass transfer are of great importance in geophysics, aeronautics, and engineering. In several process IJOART such as drying, evaporation of water at body surface, energy transfer in a wet cooling tower, and flow in a desert cooler, heat and mass transfer occurs simultaneously A number of investigations have already been carried out with combined heat and mass transfer under the assumption of different physical situations. The illustrative examples of mass transfer can be found in the book of Cussler [5] .Combined heat and mass transfer flow past a surface analyzed by Chaudhary et. al. [6], Muthucumaraswamy et. al. [7,8] and Rajput et.al.[9 ]with different physical conditions. Chaudhary et. al. [10] pioneered unsteady heat and mass transfer flow past a surface by Laplace Transform method. Combined heat and mass transfer problems with chemical reaction are of importance in many processes and have, therefore, received a considerable amount of attention in recent years. Chemical reaction can be codified as either homogeneous or heterogeneous processes. A homogeneous reaction is one that occurs uniformly through a given phase. In contrast, a heterogeneous reaction takes place in a restricted region or Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 134 within the boundary of a phase. A reaction is said to be first order, if the rate of reaction is directly proportional to the concentration itself which has many applications in different chemical engineering processes and other industrial applications such as polymer production, manufacturing of ceramics or glassware and food processing. Das et al. [11] considered the effects of first order chemical reaction on the flow past an impulsively started infinite vertical plate with constant heat flux and mass transfer. Muthucumarswamy et. al. [12] studied study of chemical reaction effects on vertical plate with variable temperature. In the above mentioned studies the effects of radiation on flow has not been considered. Actually, many processes in new engineering areas occur at high IJOART temperature and knowledge of radiation heat transfer becomes imperative for the design of the pertinent equipment. Nuclear power plants, gas turbines and the various propulsion devices for aircraft, missiles, satellites, and space vehicles are examples of such engineering areas. The effects of radiation on free convection on the accelerated flow of a viscous incompressible fluid past an infinite vertical plate has many important technological applications in the astrophysical, geophysical and engineering problem. Unsteady Free Convection flow past a Vertical plate with chemical reaction under different temperature condition on the plate is elucidated by Bhaben Ch. Neog et.al.[13] and Rajesh V. [14] et.al. Thermal radiation effect on flow past a vertical plate with mass transfer is examined by Muralidharan M. et. al. [15] and Rajput et.al. [16]. Natural convective flow past a plate with constant mass flux in the presence of radiation is studied by Chaudhary et. al. [17] However, it seems less attention was paid on free convection flows near a vertical plate subjected to a constant heat flux boundary condition even though this situation Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 135 involves in many engineering applications. In many problems particularly those involving the cooling of electrical nuclear components, the wall heat flux is specified. In such problems, over heating burns out and melt down are very important issues. From practical stand point, an important wall model is considered with constant heat flux. Ogulu et. al. [18] and Narahari, M. et. al. [19] examined the flow past a surface with constant heat flux. Free convection effects on flow past an infinite vertical accelerated with constant heat flux is pioneered by Chaudhary et. al. [20 ]. Hence, the objective of this paper is to study the influence of chemical reaction and the combined effects of heat and mass transfer on flow over a moving vertical plate in presence of radiation with heat is supplied to the plate at constant rate. IJOART 2. MATHEMATICAL ANALYSIS: We consider a two-dimensional flow of an incompressible and electrically conducting viscous fluid along an infinite vertical plate. The x'-axis is taken on the infinite plate and parallel to the free stream velocity and y'axis normal to it. Initially, the plate and the fluid are at same temperature T ' with concentration level C ' at all points. At time t' > 0, the plate concentration is changed to C'w with heat supplied at a Constant rate to the plate and it accelerates with a velocity U R 3t ' in its own plane. It is assumed that there exist a homogeneous chemical reaction of first order with constant rate K l between the diffusing species and the fluid. Since the plate is infinite in extent therefore the flow variables are the functions of y' and t' only. The fluid is considered to be gray absorbing-emitting radiation but non scattering medium . The radiative heat flux in the x'-direction is considered negligible in comparison with of y'-direction. Then neglecting viscous dissipation and assuming variation of density in the body force term (Boussinesq’s Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 136 approximation), the problem can be governed by the following set of equations: T ' 2T' 1 q r ' 2 C p y' C p y ' t …(1) C' 2 C' D k l C' ' 2 t y' …(2) u' 2 u' 2 g (T ' T' ) g c (C ' C ' ') t' y' …(3) with following initial and boundary conditions u' 0 , T ' T' , C ' C ' for all y', t' 0 u' …(4) IJOART U R 3 t ' T ' , y ' ' ' as y , t 0 q - , C' C 'w at y' 0, t' 0 u ' 0, T ' T' , C ' C ' The radiative heat flux term, by using the Rosseland’s approximation is given by qr 4 T'4 3 y' where UR is reference velocity, …(5) g is gravitational acceleration, C p is specific heat at constant pressure, D is mass diffusivity, is thermal expansion coefficient, C is concentration expansion coefficient, is density, is thermal conductivity of fluid, is mean absorption coefficient, is electrical conductivity of fluid, is kinematic viscosity and , qr is radiative heat flux, σ is Stefan-Boltzmann constant. We assume that the temperature differences within the flow are such that T' 4 may be expressed as a linear function of the temperature T'. This is accomplished by expanding T' 4 in a Taylor series about T ' and neglecting higher-order terms Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 137 T'4 4 T'3 T' 3T'4 …(6) By using equations (5) and (6), equation (1) gives Cp T' 2 T' 16 T'3 2 T' t' y'2 3 y'2 …(7) Introducing the following dimensionless quantities t' , y tR t Cp Pr C y' ,u LR , Sc U2 k u' , k R2 l , UR T ' T' g q 2 , ,G q U R 4 D U R g C (C 'w C ' ) C ' C ' k , Gm , k 2l , R ' ' 3 C w C UR UR 4 T'3 IJOART T Tw' T' , U R (gt)1/3 , g T LR 2 1 3 t R g T) 2 3 1 3 . …(8) where LR is reference length, tR is reference time, Gm is modified Grashof number, Pr is Prandtl number, Sc is Schmidt number and u is dimensionless velocity component, is dimensionless temperature, C is dimensionless concentration, is viscosity of fluid, t is time in dimensionless coordinate, R is radiation parameter and k is chemical reaction parameter. The governing Equations (1) to (3) reduce to the following non-dimensional form Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 Pr 138 4 2 (1 ) t 3R y 2 ...(9) 1 2C C kC t Sc y 2 …(10) u 2 u G Gm C t y 2 …(11) with the following initial and boundary conditions u 0 , 0, C 0 for all y, t 0 …(12) 1, C 1 at y 0, t 0 y u 0, 0, C 0 as y , t 0 u t, …(13) IJOART On taking Laplace-transform of Equations (9) to (11) and Boundary conditions (12, 13), we get 2 4 d (1 ) p Pr 0 3R dy 2 …(14) d2 k+p Sc C 0 dy 2 …(15) d 2u p u G ( y,p) -G m C 2 dy …(16) u 1 d 1 1 , ,C 2 p dy p p u a s y , t 0 at y 0, t 0 0, 0, C 0 …(17) Where p is the Laplace -transform parameter. Solving Equations (14) to (16) with the help of Boundary condition (17), we get (y,p) Copyright © 2013 SciResPub. H Pr exp ( y p3/ 2 pPr ) H ...(18) IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 C (y,p) exp ( y (kSc+p Sc)) p u (y,p) exp ( y p) p2 …(19) Gm exp ( y p ) H G exp ( y p ) Pr kSc Pr p 5 / 2 ( -1) p (Sc-1)(p+ ) H Sc 1 139 Gm exp ( y pSc kSc ) kSc p (Sc 1) p + Sc 1 H Pr p pr ) H p 5 / 2 (Pr/ H 1) G exp ( y IJOART …(20) On taking inverse Laplace-transform of Equations (18) to (20), we get tH - 2 Pr Pr erfc ( ) t erfc H H Pr …(21) 1 C {exp(2 kSc t )erfc ( Sc kt ) exp( 2 kSc t )erfc ( Sc kt )} 2 …(22) For Pr =Sc 1 2exp ( 2 ) 2 u t (1+2 )erfc() H G t 3/2 4 (1 2 ) exp ( 2 ) 6 42 erfc() Pr Pr 3 ( -1) H Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 140 H G t 3/2 4 Pr Pr Pr Pr Pr Gm (1 2 ) exp( 2 ) (6 42 ) erfc( ) erfc() Pr 3 (1 Pr ) H H H H H k Sc H Gm kSc t kSc t kSc t kSc t kSc t {exp( ) ((exp(2 )erfc( ) exp( 2 )erfc( ) 2k Sc 1 Sc 1 Sc 1 Sc 1 Sc 1 Sc Gm kSc t kSc t kt k Sct kt exp( ) (exp(2 )erfc( Sc ) exp( 2 )erfc( Sc ) 2k Sc 1 Sc 1 Sc 1 Sc 1 Sc 1 Sc Gm exp(2 k Sct erfc( Sc k t ) exp(2 k Sct erfc( Sc k t ) 2 k Sc IJOART Where H 1 …(23) 4 3R In expressions, erfc (x1+i y1) is complementary error function of complex argument which can be calculated in terms of tabulated functions in Abramowitz et al. [21].The tables given in Abramowitz et al. [21] do not give erfc (x1 + i y1) directly but an auxiliary function W1(x1 + iy1) which is defined as erfc (x1 iy1 W1 y1 i x 1 exp { x 1 iy1 2 Some properties of W1 (x1 + iy1) are W1 x 1 iy1 W2 x 1 i y1 W1 x 1 i y1 2 exp {-(x1 iy1 2 W2 x 1 i y1 where W2 x 1 iy1 is complex conjugate of W1 x 1 iy1 Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 141 3. SKIN-FRICTION: From velocity field , skin-friction at the plate in non dimensional form is expressed as: u y y 0 H G t Pr 1 Pr ( Pr -1) H H 2t t Gm kSc t kSc t kSc Gm ) erf ( ) kSc erf kt exp( k Sc 1 Sc 1 Sc 1 Sc k Sc Gm kSc t kt kSc ) erf ( ) exp( k Sc 1 Sc 1 Sc 1 Sc IJOART …(24) 4. NUSSELT NUMBER From temperature field, the rate of heat transfer in non-dimensional form is expressed as Nu 1 (0) y y0 1 (0) Pr tH …(25) 5. SHERWOOD NUMBER From the concentration field, the rate of concentration transfer, which when expressed in non-dimensional form, is given by Sh Copyright © 2013 SciResPub. y y 0 IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 k Sc 1 Sc (2 exp( k t)) 2 2 t 142 …(26) 6. DISCUSSION: In order to get physical insight into the problem, the values of Schmidt number are chosen to represent the presence of species by Hydrogen (0.22), Water vapor (0.60) and Carbon dioxide (0.96) at 250C temperature and 1 atmospheric pressure, the values of Pr are chosen 0.71, 7 which represent air and water respectively at 200C temperature and 1 atmospheric pressure. The values of other parameters are chosen arbitrary. Figure 1 reveals temperature profiles against (distance from the plate). It is obvious from the figure that the magnitude of temperature is maximum at the plate and then decays to zero asymptotically. Further, the magnitude of the temperature for air is IJOART greater than that of water. This is due to the fact that thermal conductivity of fluid decreases with increasing Pr, resulting a decrease in thermal boundary layer thickness. It is also seen that it decreases steeply for Pr = 7 than that of Pr = 0.71. Furthermore, it is noticed that an increase in radiation parameter to 4, 15 the temperature decreases but it increases with increasing time. The species concentration profiles verses is plotted in F igure 2. It is observed that the concentration at all points in the flow field decreases with and tends to zero as . Furthermore, an increase in the value of Sc leads to a fall in the concentration. Physically, it is true since increase of Sc means decrease of molecular diffusivity which results in decrease of concentration boundary layer. Hence, the concentration of species is higher for small values of Sc. It is also observed that concentration decreases with an increase in time. Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 143 Figure 3 illustrates the influences of Sc, t, and Pr on the velocity against η. It is noticed that at the plate, fluid velocity is equal to value of time then it increases and attains maximum velocity in the vicinity of the plate(η<0.6) after that it decreases and vanish far away from the plate for both Pr = 7 and 0.71 whereas with an increase in Sc it decreases continuously to asymptotic value. Further, it also increases with an increase in time at each point in the flow field for Hydrogen gas. The effect of time on velocity boundary layer is more dominant than Sc for both water and air. Finally, we observed that the velocity for Hydrogen(Sc=0.22) is higher than that of carbon di oxide (Sc=0.96) for both air and water. Physically, it is possible since an increase in Sc means increase in kinematic viscosity or viscosity of fluid due to which the velocity of fluid decreases. IJOART It is also obvious from figure that increase or decrease in thickness of velocity boundary layer with an increase in parameters value is greater near the plate then away from the plate and on moving away from the plate this difference is negligible Figure 4 illustrates the influences of Gm, G and Pr on the velocity. This Figure reveals that the maximum velocity attains near the plate then decreases and faded away from the plate. Further velocity for Pr=7 is less than that of Pr=0.71 since increasing Pr means increasing viscosity which in turn reduces the velocity of flow. Moreover, it is observed that an increase in G, Gm leads to an increase in velocity for both Pr=7 and Pr =0.71 when Hydrogen gas is present in the flow field. The reason is that the values of Grashof number and modified Grashof number has the tendency to increase the mass buoyancy effect. The increase in velocity due to increase in G and Gm is more near the plate than away from the plate. Figure 5 elucidates the effects of k, R and Pr on velocity profile. It is found that the velocity decreases with an increase in chemical reaction parameter k from 0.2 to 10 for both Pr=7 and 0.71. The same phenomenon is observed with an Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 144 increase in radiation parameter from 4 to 20. It is obvious since the radiation parameter defines the relative contribution of conduction heat transfer to the thermal radiation transfer. Moreover, the variation of the velocity across the boundary layer with R is found to be negligibly small. Figure 6 elucidates the effects of Sc, k, Pr, G, Gm on skin friction which is plotted against time t. The maximum value of skin friction occurs for smaller values of t and then it decreases rapidly with increasing t. It is clear from the Figure that skin-friction increases with an increase in Sc, Pr and k but reverse effect is observed with an increase in G and Gm. The Figure depicts that skin friction is higher for Sc=0.96 in comparison to for Sc=0.22. Physically, it is correct since an increase in Sc serves to increase IJOART momentum boundary layer thickness. Further, increasing Pr means increasing viscosity of fluid which increases the magnitude of skin friction. Moreover increasing value of chemical reaction parameter reflects decrease in kinematic viscosity or viscosity of fluid which results increase in the value of skin friction The boundary layer separation occurs in the fluid flow. The variation in the values of skin friction is more dominant with parameters Pr and Gm in comparison with other parameters. Figure 7 exhibits the Nusselt number against time. It is concluded from the Figure that there is a increase in it with an increase in the value of radiation parameter. Further, the value of Nusselt number for water is greater than air. It is consistent with the fact that smaller values of Pr are equivalent to increasing thermal conductivities and therefore heat is able to diffuse away from the plate more rapidly than higher values of Pr, hence the rate of heat transfer is reduced. Figure 8 depicts the effect of chemical reaction parameter k and Schmidt number Sc on Sherwood number. It is observed that Sherwood number increase with an Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 145 increase in k and Sc. Since increase in Sc means decrease in molecular diffusivity which in turn gives rise to increase in Sherwood number as Sherwood number is the ratio of convective and diffusive mass transfer coefficient. Chemical reaction parameter is the interfacial mass transfer so Sherwood number increases with an increase in k. REFERENCES: [1] Stokes GG, On the Effect of Internal Friction of Fluids on the Motion of Pendulums, Mathematical and Physical Papers 1851; 3; 8-106. [2] Soundalgekar VM, Free Convection Effects on Stokes’s Problem for a v ertical Plate, American Society of Mechanical Engineers Journal of Heat Transfer 1977; 99C; 499-501. IJOART [3] Revankar ST, Free convection effect on a flow past an impulsively started or oscillating infinite vertical plate, Mechanics Research Comm. 2000; 27; 241-246. [4] Jian L, Ingham DB and Pop I, Natural convection from a vertical flat plate with a surface temperature oscillation, Int. J. Heat Mass Transfer 2001; 44; 23112322. [5] Cussler EL, Diffusion Mass Transfer in Fluid Systems, Cambridge: Cambridge University Press; 1998. [6] Chaudhary RC and Jain A, Combined heat and mass transfer effect on MHD free convection flow past an oscillating plate embedded in porous medium, Rom.Journ.Phys.(Romania) 2007; 52;505-524. [7] Muthucumaraswamy R and Vijayalakshmi A, Effects of heat and mass transfer on flow past an oscillating vertical plate with variable temperature., Int. J. of Appl. Math and Mech. 2008; 4; 59 – 65. Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 146 [8] Muthucumaraswamy R, Sundar RM and Subramanian VSA, Unsteady flow past an accelerated infinite vertical plate with variable temperature and uniform mass diffusion, Int. J. of Appl. Math and Mech. 2009.;5; 51 – 56. 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Mech. 2006 ; 33; 245-257.ts reaction on moving i [13] Bhaben CN, Das RK, Unsteady Free Convection MHD Flow past a vertical plate with variable temperature and chemical reaction, International Journal of Engineering Research & Technology 2012; 1; 1-5. [14] Rajesh V, Radiation effects on MHD free convection flow near a vertical plate with ramped wall temperature, Int. J. of Appl. Math and Mech. 2010; 6; 60 – 77. [15] Muralidharan M and Muthucumaraswamy R, Thermal radiation on linearly accelerated vertical plate with variable temperature and uniform mass flux, Indian Journal of Science and Technology 2010; 3; 398-401. Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 147 [16] Rajput US and Kumar S, Radiation Effects on MHD flow past an impulsively started vertical plate with variable heat and mass transfer, Int. J. of Appl. Math. and Mech. 2012; 8; 66-85. 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IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 148 IJOART Figure1: Temperature profile Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 149 IJOART Figure 2: Concentration profile for k=0.2 Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 150 IJOART Figure 3 : Velocity profile for R=4, k=0.2, G=5, Gm=2 Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 151 IJOART Figure 4: Velocity profile R=4, k=0.2, SC=0.22, t=0.2 Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 152 IJOART Figure 5: Velocity profile for sc=0.22, t=0.2, G=5, Gm=2 Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 153 IJOART Figure 6: Skin-friction for R=4. Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 154 IJOART Figure 7: Nusselt number Copyright © 2013 SciResPub. IJOART International Journal of Advancements in Research & Technology, Volume 2, Issue 11, November-2013 ISSN 2278-7763 155 IJOART Figure 8 : Sherwood number Copyright © 2013 SciResPub. IJOART