ISRN Thermodynamics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Partition Function in One, Two, and Three Spatial Dimensions from Effective Lagrangian Field Theory Tue, 11 Mar 2014 14:40:58 +0000 The systematic effective Lagrangian method was first formulated in the context of the strong interaction; chiral perturbation theory (CHPT) is the effective theory of quantum chromodynamics (QCD). It was then pointed out that the method can be transferred to the nonrelativistic domain—in particular, to describe the low-energy properties of ferromagnets. Interestingly, whereas for Lorentz-invariant systems the effective Lagrangian method fails in one spatial dimension , it perfectly works for nonrelativistic systems in . In the present brief review, we give an outline of the method and then focus on the partition function for ferromagnetic spin chains, ferromagnetic films, and ferromagnetic crystals up to three loops in the perturbative expansion—an accuracy never achieved by conventional condensed matter methods. We then compare ferromagnets in , 2, 3 with the behavior of QCD at low temperatures by considering the pressure and the order parameter. The two apparently very different systems (ferromagnets and QCD) are related from a universal point of view based on the spontaneously broken symmetry. In either case, the low-energy dynamics is described by an effective theory containing Goldstone bosons as basic degrees of freedom. Christoph P. Hofmann Copyright © 2014 Christoph P. Hofmann. All rights reserved. Thermodynamic Analysis of Ethanol Dry Reforming: Effect of Combined Parameters Tue, 04 Mar 2014 09:10:17 +0000 The prospect of ethanol dry reforming process to utilize CO2 for conversion to hydrogen, syngas, and carbon nanofilaments using abundantly available biofuel—ethanol, and widely available environmental pollutant CO2 is very enthusiastic. A thermodynamic analysis of ethanol CO2 reforming process is done using Gibbs free energy minimization methodology within the temperature range 300–900°C, 1–10 bar pressure, and CO2 to carbon (in ethanol) ratio (CCER) 1–5. The effect of individual as well as combined effect of process parameters such as temperature, pressure, and CCER was determined on the product distribution. Optimum process conditions for maximising desired products and minimizing undesired products for applications such as gas to liquids (GTL) via fischer tropsch synthesis, syngas generation for Solid oxide fuel cells, and carbon nanofilament manufacture were found in this study. Ganesh R. Kale and Tejas M. Gaikwad Copyright © 2014 Ganesh R. Kale and Tejas M. Gaikwad. All rights reserved. Application of COSMO-RS Method for the Prediction of Liquid-Liquid Equilibrium of Water/n-Dodecane/1-Butanol Wed, 05 Feb 2014 11:49:22 +0000 The liquid-liquid equilibrium (LLE) for the system water-dodecane-butanol was estimated using the UNIQUAC model. In the UNIQUAC model interaction parameters were estimated from the vapor-liquid equilibrium (VLE) and LLE data of their constituent binary pairs. The water-dodecane-butanol LLE was experimentally measured at 298.15 K. Phase stability constraints were taken into account while calculating the binary interaction parameters from the mutual solubility data. The COSMO-RS method was used to estimate the activity coefficient in the miscible binary pair. The ternary LLE composition was predicted using the experimental VLE data as well as using the COSMO-RS calculated activity coefficient data along with the experimental mutual solubility data. In the latter case the root mean square deviation (RMSD) for the distribution of butanol between aqueous and organic phase is 0.24%. The corresponding UNIFAC model prediction is 7.63%. S. Balasubramonian, Shekhar Kumar, D. Sivakumar, and U. Kamachi Mudali Copyright © 2014 S. Balasubramonian et al. All rights reserved. Thermodynamic and Interfacial Properties of DTABr/CTABr Mixed Surfactant Systems in Ethanolamine/Water Mixtures: A Conductometry Study Tue, 17 Dec 2013 11:08:33 +0000 Mixed-micelle formation in the binary mixtures of dodecyltrimethylammonium bromide (DTABr) and cetyltrimethylammonium bromide (CTABr) surfactants in water-ethanolamine mixed solvent systems has been studied by conductometric method in the temperature range of 298.1 to 313.1 K at 5 K intervals. It was observed that the presence of ethanolamine forced the formation of mixed micelle to lower total surfactant concentration than in water only. The synergistic interaction was quantitatively investigated using the theoretical models of Clint and Rubingh. The interaction parameter β12 was negative at all the mole fractions of DTABr in the surfactant mixtures indicating a strong synergistic interaction, with the presence of ethanolamine in the solvent system resulting in a more enhanced synergism in micelle formation than in water only. The free energy of micellization values was more negative in water-ethanolamine mixed solvent system than in pure water indicating more spontaneity in mixed micelle formation in the presence of ethanolamine than in pure water. Olaseni Segun Esan, Medinat Olubunmi Osundiya, Christopher Olumuyiwa Aboluwoye, Owoyomi Olanrewaju, and Jide Ige Copyright © 2013 Olaseni Segun Esan et al. All rights reserved. Thermodynamical Analysis of the Flow and Heat Transfer over a Static and a Moving Wedge Tue, 29 Oct 2013 14:03:03 +0000 The first and second law characteristics of fluid flow and heat transfer over a static and a moving wedge are investigated. With the help of suitable similarity transformations, the governing boundary layer equations for the velocity and temperature fields are transformed into ordinary differential equations and are solved numerically. The velocity and the temperature profiles are obtained for various parameters and are utilized to compute the entropy generation number Ns and the Bejan number Be. The effects of various physical parameters on the entropy generation number and the Bejan number are depicted through graphs and are discussed qualitatively. It is observed that the entropy production rate is less in case of wedge moving in the opposite direction to flow as compared to static wedge. Adnan Saeed Butt and Asif Ali Copyright © 2013 Adnan Saeed Butt and Asif Ali. All rights reserved. Wavelength Width Dependence of Cavity Temperature Distribution in Semiconductor Diode Laser Sun, 27 Oct 2013 11:48:54 +0000 The study of heat distribution in laser diode shows that there is nonuniform temperature distribution in cavity length of laser diode. In this paper, we investigate the temperature difference in laser diode cavity length and its effect on laser bar output wavelength width that mounted on usual CS model. In this survey at the first, laser was simulated then the simulations result was compared with experimental test result. The result shows that for each emitter there is difference, about 2.5 degree between the beginning and end of cavity. S. P. Abbasi and A. Alimorady Copyright © 2013 S. P. Abbasi and A. Alimorady. All rights reserved. A Derivation of the Main Relations of Nonequilibrium Thermodynamics Mon, 21 Oct 2013 15:37:36 +0000 The principles of nonequilibrium thermodynamics are discussed, using the concept of internal variables that describe deviations of a thermodynamic system from the equilibrium state. While considering the first law of thermodynamics, work of internal variables is taken into account. It is shown that the requirement that the thermodynamic system cannot fulfil any work via internal variables is equivalent to the conventional formulation of the second law of thermodynamics. These statements, in line with the axioms introducing internal variables can be considered as basic principles of nonequilibrium thermodynamics. While considering stationary nonequilibrium situations close to equilibrium, it is shown that known linear parities between thermodynamic forces and fluxes and also the production of entropy, as a sum of products of thermodynamic forces and fluxes, are consequences of fundamental principles of thermodynamics. Vladimir N. Pokrovskii Copyright © 2013 Vladimir N. Pokrovskii. All rights reserved. Analytical Solution of Nonlinear Boundary Value Problem for Fin Efficiency of Convective Straight Fins with Temperature-Dependent Thermal Conductivity Sun, 08 Sep 2013 15:15:13 +0000 We have employed homotopy analysis method (HAM) to evaluate the approximate analytical solution of the nonlinear equation arising in the convective straight fins with temperature-dependent thermal conductivity problem. Solutions are presented for the dimensionless temperature distribution and fin efficiency of the nonlinear equation. The analytical results are compared with previous work and satisfactory agreement is noted. K. Saravanakumar, V. Ananthaswamy, M. Subha, and L. Rajendran Copyright © 2013 K. Saravanakumar et al. All rights reserved. Perturbation Solution for Radiating Viscoelastic Fluid Flow and Heat Transfer with Convective Boundary Condition in Nonuniform Channel with Hall Current and Chemical Reaction Tue, 03 Sep 2013 13:33:24 +0000 A mathematical analysis has been performed for heat and mass transfer of a time-dependent MHD flow of an electrically conducting viscoelastic fluid in nonuniform vertical channel with convective boundary condition. The fluid flow is considered between a vertical long wavy wall and a parallel flat wall saturated with the porous medium. The effects of thermal radiation, heat absorption, chemical reaction, and Hall current are taken into account. The prevailing nonlinear partial differential equations are derived by considering Boussinesq approximation, and the same equations are solved analytically using perturbation technique. Further the expressions for skin friction, Nusselt number, and Sherwood number are presented. The effects of various pertinent parameters on different flow fields are analyzed graphically and tabularly. It is found that effects of Hall parameter and Biot number are unfavorable on velocity profiles, but this trend is reverse for the effect of thermal and solutal Grashof numbers. The expressions of different flow fields satisfy the imposed boundary conditions, which is shown in all graphs; this implies accuracy of the solution. B. J. Gireesha and B. Mahanthesh Copyright © 2013 B. J. Gireesha and B. Mahanthesh. All rights reserved. Analytical Solution of MHD Stagnation-Point Flow and Heat Transfer of Casson Fluid over a Stretching Sheet with Partial Slip Mon, 05 Aug 2013 09:48:48 +0000 This paper investigates the hydromagnetic boundary layer flow and heat transfer of a non-Newtonian Casson fluid in the neighborhood of a stagnation point over a stretching surface in the presence of velocity and thermal slips at the boundary. The governing partial differential equations are transformed into nonlinear ordinary differential equations using similarity transformations. The analytic solutions are developed by a homotopy analysis method (HAM). The results pertaining to the present study indicate that the flow and temperature fields are significantly influenced by Casson parameter (), the magnetic parameter , the velocity slip parameter , and the thermal slip parameter . An increase in the velocity slip parameter causes decrease in the flow velocity, while an increase in the value of the thermal slip parameter causes increase in the temperature of the fluid. It is also observed that the velocity at a point decreases with increase in . Samir Kumar Nandy Copyright © 2013 Samir Kumar Nandy. All rights reserved. Similarity Solution of Heat and Mass Transfer for Natural Convection over a Moving Vertical Plate with Internal Heat Generation and a Convective Boundary Condition in the Presence of Thermal Radiation, Viscous Dissipation, and Chemical Reaction Mon, 29 Jul 2013 09:59:35 +0000 Steady laminar natural convection flow over a semi-infinite moving vertical plate with internal heat generation and convective surface boundary condition in the presence of thermal radiation, viscous dissipation, and chemical reaction is examined in this paper. In the analysis, we assumed that the left surface of the plate is in contact with a hot fluid while the cold fluid on the right surface of the plate contains a heat source that decays exponentially with the classical similarity variable. We utilized similarity variable to transform the governing nonlinear partial differential equations into a system of ordinary differential equations, which are solved numerically by applying shooting iteration technique along fourth-order Runge-Kutta method. The effects of the local Biot number, Prandtl number, buoyancy forces, the internal heat generation, the thermal radiation, Eckert number, viscous dissipation, and chemical reaction on the velocity, temperature, and concentration profiles are illustrated and interpreted in physical terms. A comparison with previously published results on the similar special cases showed an excellent agreement. Finally, numerical values of physical quantities, such as the local skin-friction coefficient, the local Nusselt number, and the local Sherwood number, are presented in tabular form. S. Mohammed Ibrahim and N. Bhashar Reddy Copyright © 2013 S. Mohammed Ibrahim and N. Bhashar Reddy. All rights reserved. A New Cryogenic Air Separation Process with Flash Separator Thu, 27 Jun 2013 15:02:31 +0000 A new cryogenic air separation process with flash separator is developed. A flash separator is added to the conventional double-column cryogenic air separation process. The flash separator is used to replace the turbine required to recover a portion of the energy in the double-column air separation process. The flash separator served dual purposes of throttling and separation. Both the conventional and the new processes are simulated using Aspen Plus version 11.1 the model air flow rate and compositions are taken as 50000 Nm3/h of air at standard conditions of 1 atm and 25°C and feed composition of 79.1% N2 and 20.9% O2. The new process decreases the energy consumption and increases the productivity. Zeinab A. M. Khalel, Ali A. Rabah, and Taj Alasfia M. Barakat Copyright © 2013 Zeinab A. M. Khalel et al. All rights reserved. Effects of Binary Chemical Reaction and Activation Energy on MHD Boundary Layer Heat and Mass Transfer Flow with Viscous Dissipation and Heat Generation/Absorption Thu, 07 Mar 2013 09:11:04 +0000 We study an unsteady MHD free convection heat and mass transfer boundary layer incompressible fluid flow past a vertical porous plate in the presence of viscous dissipation, heat generation/absorption, chemical reaction, and Arrhenius activation energy. The plate is moving with uniform velocity. The chemical reaction rate in the function of temperature is also considered. The governing partial differential equations are reduced to ordinary differential equations by introducing local similarity transformation (Maleque (2010)) and then are solved numerically by shooting method using the Nachtsheim-Swigert iteration technique. The results of the numerical solution are then presented graphically as well as the tabular form for difference values of the various parameters. Kh. Abdul Maleque Copyright © 2013 Kh. Abdul Maleque. All rights reserved. Radiation and Mass Transfer Effects on MHD Free Convection Flow of a Micropolar Fluid past a Stretching Surface Embedded in a Non-Darcian Porous Medium with Heat Generation Thu, 21 Feb 2013 15:10:25 +0000 A comprehensive study of mass transfer and thermal radiation on a steady two-dimensional laminar flow of a viscous incompressible electrically conducting micropolar fluid past a stretching surface embedded in a non-Darcian porous medium in the presence of heat generation is analyzed numerically. The governing equations of momentum, angular momentum, energy, and species equations are solved numerically using Runge-Kutta fourth order method with the shooting technique. The effects of various parameters on the velocity, microrotation, temperature and concentration field as well as skin friction coefficient, Nusselt number and Sherwood number are shown graphically and tabulated. It is observed that the micropolar fluid helps in the reduction of drag forces and also acts as a cooling agent. S. Mohammed Ibrahim, T. Sankar Reddy, and N. Bhaskar Reddy Copyright © 2013 S. Mohammed Ibrahim et al. All rights reserved. Influence of Variable Permeability and Radiation Absorption on Heat and Mass Transfer in MHD Micropolar Flow over a Vertical Moving Porous Plate Mon, 18 Feb 2013 11:56:25 +0000 An analysis of unsteady free convection with heat and mass transfer flow for a micropolar fluid through a porous medium with a variable permeability bounded by a semi-infinite vertical plate in the presence of heat generation, thermal radiation, first-order chemical reaction, and the radiation absorption is reported. The plate is assumed to move with a constant velocity in the direction of fluid flow. A uniform magnetic field acts perpendicular to the porous surface which absorbs micropolar fluid with a suction velocity varying with time. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and nonharmonic functions. To observe physical insight and interesting aspects of the problem, the velocity, angular velocity, temperature, and concentration field are numerically studied and displayed graphically for pertinent parameters. D. Harish Babu and P. V. Satya Narayana Copyright © 2013 D. Harish Babu and P. V. Satya Narayana. All rights reserved. MHD Flow and Heat Transfer in a Channel Bounded by a Shrinking Sheet and a Porous Medium Bed: Homotopy Analysis Method Thu, 17 Jan 2013 08:03:37 +0000 MHD flow of viscous conducting fluid is considered between a shrinking sheet and a porous medium bed. Suction is applied at the upper shrinking sheet and its surface temperature is always maintained higher than the temperature of the lower porous bed surface. Similarity transformations and HAM are used to solve the governing equations for velocity and temperature fields. The effects of various pertinent parameters on the results are discussed graphically. Dileep Singh Chauhan and Rashmi Agrawal Copyright © 2013 Dileep Singh Chauhan and Rashmi Agrawal. All rights reserved. Heat Transfer due to Magnetohydrodynamic Stagnation-Point Flow of a Power-Law Fluid towards a Stretching Surface in the Presence of Thermal Radiation and Suction/Injection Thu, 20 Dec 2012 11:42:02 +0000 An analysis is made on the study of two-dimensional MHD (magnetohydrodynamic) boundary-layer stagnation-point flow of an electrically conducting power-law fluid over a stretching surface when the surface is stretched in its own plane with a velocity proportional to the distance from the stagnation-point in the presence of thermal radiation and suction/injection. The paper examines heat transfer in the stagnation-point flow of a power-law fluid except when the ratio of the free stream velocity and stretching velocity is equal to unity. The governing partial differential equations along with the boundary conditions are first brought into a dimensionless form and then the equations are solved by Runge-Kutta fourth-order scheme with shooting techniques. It is found that the temperature at a point decreases/increases with increase in the magnetic field when free stream velocity is greater/less than the stretching velocity. It is further observed that for a given value of the magnetic parameter , the dimensionless rate of heat transfer at the surface and decreases/increases with increase in the power-law index . Further, the temperature at a point in the fluid decreases with increase in the radiation parameter when free stream velocity is greater/less than the stretching velocity. Tapas Ray Mahapatra, Sabyasachi Mondal, and Dulal Pal Copyright © 2012 Tapas Ray Mahapatra et al. All rights reserved. On the Thermal Effusivity of Bovine Milk Thu, 20 Dec 2012 09:32:35 +0000 Thermal diffusivity, conductivity, and effusivity are parameters that can be measured using photoacoustic techniques. Both thermal diffusivity and conductivity have already been measured for bovine milk. To complete its thermal characterization, this paper deals with the thermal effusivity of commercial bovine milk with a different fat content. The thermal effusivity ε obtained for skimmed, partly skimmed, and whole milks is 0.153 W cm−2 s1/2 K−1, 0.144 W cm−2 s1/2 K−1, and 0.140 W cm−2 s1/2 K−1, respectively, with the uncertainty being less than 5%. It was observed that the thermal effusivity decreases with the increase in the fat content. For the first time, it is observed that the thermal effusivity is a linear function of the logarithm of the fat content. The comparison of our results with previous results for milk from Slovakia revealed different thermal effusivity values. This might be due to regional differences in the milk composition and could be used as a criterion to identify the milk provenience. Daniel Acosta-Avalos and Daniel Soares Velasco Copyright © 2012 Daniel Acosta-Avalos and Daniel Soares Velasco. All rights reserved. Thermodynamics and Oxidation Behaviour of Crystalline Silicon Carbide (3C) with Atomic Oxygen and Ozone Thu, 13 Dec 2012 19:32:31 +0000 Thermodynamics of oxidation of crystalline silicon carbide (cubic form) by atomic oxygen (O) and ozone (O3) was derived to understand the thermodynamic stability of SiC in the upper atmosphere. Equilibrium constants and equilibrium partial pressures were computed for each of eight possible reactions of SiC with O and O3. Equilibrium activity diagrams were derived, showing the most stable oxidation products of SiC, represented in temperature-oxygen pressure 2D diagrams. Programs were developed in Mathematica. The diagrams provide an understanding of the oxidation routes of SiC under changing levels of O/O3 and temperature, as encountered during reentry of space vehicles. At high levels of the volatiles, CO2, CO, and SiO and temperatures between 1000 and 1500 K, oxidation by atomic oxygen or ozone first produced SiO2 + C followed by SiO2 + CO and finally SiO2 + CO2. When volatiles were at very low pressures, the sequence of oxidation was SiO + CO followed by either SiO2 + CO or SiO + CO2 and finally SiO2 + CO2. Stability of SiC in ozone was much lower than in atomic oxygen. With both oxidants, the oxidation of the Si in SiC occurred prior to the oxidation of C. Implications for mechanisms of thermal protection are discussed. Chandrika Varadachari, Ritabrata Bhowmick, and Kunal Ghosh Copyright © 2012 Chandrika Varadachari et al. All rights reserved. Entropy Generation Analysis of Human Thermal Stress Responses Thu, 13 Dec 2012 11:51:46 +0000 The present study involves application of an open system entropy generation formulation to analyze human thermal stress responses. The time-series human thermal stress response data are obtained by conducting a simulation using a validated finite-element human thermal model (FEHTM). These simulated human thermal response data are used as an input to the entropy generation expression to obtain human entropy generation (HEG) values. The effects of variables such as air temperature, relative humidity, physical activity, and clothing on entropy generation are examined. A design of experiment (DOE) approach is utilized to study the interaction effects of air temperature and relative humidity on entropy generation. The study establishes the importance and utility of entropy generation as a holistic measure of human thermal physiological reaction to external and internal changes. This novel study has great potential for use in military medicine, rehabilitation, sports, and related applications. Satish C. Boregowda, Robert E. Choate, and Rodney Handy Copyright © 2012 Satish C. Boregowda et al. All rights reserved. Conjugate Effects of Radiation Flux on Double Diffusive MHD Free Convection Flow of a Nanofluid over a Power Law Stretching Sheet Thu, 06 Dec 2012 11:36:45 +0000 This study theoretically investigates the conjugate effects of radiation flux and magnetohydrodynamic (MHD) on free convection boundary layer flow of a nanofluid over a nonlinear stretching sheet. It is assumed that the magnetic Reynolds number is small enough and the sheet is stretched with a power law velocity under the effects of the magnetic field, the buoyancy parameter, and the solutal buoyancy parameter. The model used for the nanofluid incorporates the effects of Rosseland approximation, Brownian motion, and thermophoresis parameters. By using appropriate similarity transformations, the governing nonlinear partial differential equations are transformed into dimensionless form and numerically solved using an implicit finite difference scheme known as the Keller-box method. It is found that the variations of magnetic field, buoyancy parameter, solutal buoyancy parameter, and the power law velocity parameter have strong influence on the motion. Muhammad Imran Anwar, Sharidan Shafie, Ilyas Khan, and Mohd Zuki Salleh Copyright © 2012 Muhammad Imran Anwar et al. All rights reserved. Effects of Thermal Diffusion and Radiation on Unsteady MHD Free Convection Flow Past an Infinite Heated Vertical Plate in a Porous Medium Wed, 28 Nov 2012 12:39:41 +0000 We have explored the influence of thermal diffusion and radiation on unsteady magnetohydrodynamic free convection flow past an infinite heated vertical plate in a porous medium. The governing boundary layer equations are written into a dimensionless form by similarity transformations. The transformed nonlinear differential equations are solved numerically with finite element methods. Numerical calculations are carried out for different values of dimensionless parameters. The results are presented graphically for velocity, temperature, and concentration profiles and show that the flow field and other quantities of physical interest are significantly influenced by these parameters. S. Sivaiah, K. Anitha, and S. Venkataramana Copyright © 2012 S. Sivaiah et al. All rights reserved. Theoretical Investigation of Thermodynamical and Structural Properties of 3d Liquid Transition Metals Using Different Reference Systems Mon, 19 Nov 2012 14:37:04 +0000 The present paper deals with the theoretical investigation of thermodynamical and structural properties like internal energy , entropy , Helmholtz free energy , isothermal compressibility , specific Heat , structure factor and long wave length limit of structure factor of 3d liquid transition metals. To describe electron-ion interaction we have used our newly constructed parameter free model potential. To perform this task, we have used different reference systems like Percus Yevick Hard Sphere (PYHS), One Component Plasma (OCP), and Charged Hard Sphere (CHS) reference systems. We have also seen the influence of different local field correction functions like Hartree (HR), Taylor (TR), and Sarkar et al. (SR) on thermodynamical properties of 3d liquid transition metals. Finally we conclude that the proper choice of the model potential along with reference system plays a vital role in the study of thermodynamical and structural properties of 3d liquid transition metals. Y. A. Sonvane, P. B. Thakor, and A. R. Jani Copyright © 2012 Y. A. Sonvane et al. All rights reserved. Application of the Pippard Relations to Cyclohexane near the Melting Point Mon, 19 Nov 2012 09:30:07 +0000 The Pippard relations are verified near the melting point for cyclohexane. The experimental data for the thermal expansivity is analyzed according to a power-law formula using the critical exponent and the thermodynamic quantities are calculated close to the melting point for this molecular organic compound. This applies to those compounds showing a second order transition prior to melting. Hamit Yurtseven Copyright © 2012 Hamit Yurtseven. All rights reserved. Radiative Boundary Layer Flow in Porous Medium due to Exponentially Shrinking Permeable Sheet Wed, 14 Nov 2012 19:34:24 +0000 This communication pertains to the study of radiative heat transfer in boundary layer flow over an exponentially shrinking permeable sheet placed at the bottom of fluid saturated porous medium. The porous medium has permeability of specified form. The fluid considered here is Newtonian, without phase change, optically dense, absorbing-emitting radiation but a nonscattering medium. The setup is subjected to suction to contain the vorticity in the boundary layer. The radiative heat flux in the energy equation is accounted by Rosseland approximation. The thermal conductivity is presumed to vary with temperature in a linear fashion. The governing partial differential equations are reduced to ordinary differential equations by similarity transformations. The resulting system of nonlinear ordinary differential equations is solved numerically by fourth-order Runge-Kutta scheme together with shooting method. The pertinent findings displayed through figures and tables are discussed. Paresh Vyas and Nupur Srivastava Copyright © 2012 Paresh Vyas and Nupur Srivastava. All rights reserved. Mixed Convection Heat Transfer for Nanofluids in a Lid-Driven Shallow Rectangular Cavity Uniformly Heated and Cooled from the Vertical Sides: The Cooperative Case Wed, 14 Nov 2012 11:37:44 +0000 A study of mixed convection, in a shallow lid-driven rectangular cavity filled with water-based nanofluids and subjected to uniform heat flux along the vertical side walls, has been performed numerically by solving the full governing equations via the finite volume method and the SIMPLER algorithm. In the limit of a shallow enclosure, these equations have been considerably reduced by using the parallel flow approximation. Solutions, for the flow and temperature fields, and the heat transfer rate, have been obtained as functions of the governing parameters, namely, the Reynolds (Re) and the Richardson (Ri) numbers and the solid volume fraction of nanoparticles (Φ). A good agreement has been obtained between the results of the two approaches for a wide range of the governing parameters. Moreover, it has been found that the addition of Cu-nanoparticles, into the pure water, leads to an enhancement or a degradation of heat transfer depending on the values of Re and Ri. Hassan Elharfi, Mohamed Naïmi, Mohamed Lamsaadi, Abdelghani Raji, and Mohammed Hasnaoui Copyright © 2012 Hassan Elharfi et al. All rights reserved. Rayleigh-Bénard Convection of Non-Newtonian Power-Law Fluids with Temperature-Dependent Viscosity Wed, 14 Nov 2012 11:11:37 +0000 Two-dimensional steady-state Rayleigh-Bénard convection of thermodependent power-law fluids confined in a square cavity, heated from the bottom and cooled on the top with uniform heat fluxes, has been conducted numerically using a finite difference technique. The effects of the governing parameters, which are the Pearson number , the flow behaviour index , and the Rayleigh number , on the flow onset, flow structure, and heat transfer have been examined. The heatlines concept has been used to explain the heat transfer deterioration due to temperature-dependent viscosity effect that m expresses. Mourad Kaddiri, Mohamed Naïmi, Abdelghani Raji, and Mohammed Hasnaoui Copyright © 2012 Mourad Kaddiri et al. All rights reserved. Polymorphic Forms of Lamivudine: Characterization, Estimation of Transition Temperature, and Stability Studies by Thermodynamic and Spectroscopic Studies Wed, 14 Nov 2012 10:05:08 +0000 The present study is focused on estimation of transition temperature and stability of various forms of lamivudine. The forms were recrystallized from variety of solvents and preliminarily identification on the basis of SEM revealed existence of three forms (Forms I, II, III). DSC scans of Forms I and III show that these are metastable and undergo heat mediated transformation to Form IH and Form IIIH, respectively. Form II is phase pure with single sharp melting endotherm at 178.6°C. The thermal events are visually observed by hot stage microscopy. Enthalpy of solution of the forms is endothermic and magnitude varies in the order Form II > Form IL > Form IIIL suggesting Form IIIL to be least crystalline which is well correlated with XRPD data. The transition temperature of the polymorphic pairs IL/IH and IIIL/IIIH derived from enthalpy of solution and solubility data revealed monotropy whereas enantiotropy exists in IIIH/II. The slurry experiments showed Form II to be thermodynamically most stable. Forms IL and IIIL though stable in water are converted to Form II in ethanol, acetonitrile, and propanol after 1 day. Form IIIL is converted to Form IL in water after 7 days and the observation is of importance as this instability can effect the pharmaceutical preparations whereas Form IL shows a balance between stability and solubility. Renu Chadha, Poonam Arora, and Swati Bhandari Copyright © 2012 Renu Chadha et al. All rights reserved. The Effect of Geometrical Parameters on Heat Transfer Characteristics of Compact Heat Exchanger with Louvered Fins Wed, 14 Nov 2012 09:29:42 +0000 Compact heat exchangers (CHEs) have been widely used in various applications in thermal fluid systems including automotive thermal management systems. Among the different types of heat exchangers for engine cooling applications, cross-flow CHEs with louvered fins are of special interest because of their higher heat rejection capability with the lower flow resistance. In this study, the effects of geometrical parameters such as louver angle and fin pitch on air flow and heat transfer characteristics on CHEs are numerically investigated. Numerical investigations using five different cases with increased and decreased louver angles (+2°, +4°, −2°, −4°, and uniform angle 20°), with a fixed fin pitch and using three different fin pitches (1.0 mm, 2.0 mm, and 4.0 mm), and with the fixed louver angle are examined. The three-dimensional (3D) governing equations for the fluid flow and heat transfer are solved using a standard finite-volume method (FVM) for the range of Reynolds number between 100 and 1000. The computational model is used to study the variations of pressure drop, flow temperature, and Nusselt number. P. Gunnasegaran, N. H. Shuaib, and M. F. Abdul Jalal Copyright © 2012 P. Gunnasegaran et al. All rights reserved. Heat Generation and Thermal Radiation Effects over a Stretching Sheet in a Micropolar Fluid Thu, 23 Aug 2012 10:24:09 +0000 The effects of radiation and heat generation on steady thermal boundary layer flow induced by a linearly stretching sheet immersed in an incompressible micropolar fluid with constant surface temperature are investigated. Similarity transformation is employed to transform the governing partial differential equations into ordinary ones, which are then solved numerically using the Runge-Kutta fourth order along shooting method. Results for the local Nusselt number as well as the temperature profiles are presented for different values of the governing parameters. It is observed that the velocity increases with an increase in the material parameter. It is seen that the temperature profile is influenced considerably and increases when the value of heat generation parameter increases along the boundary layer. Also, the temperature distribution of the fluid increases with an increase in the radiation parameter. Comparisons with previously published work are performed and the results are found to be in very good agreement. M. Gnaneswara Reddy Copyright © 2012 M. Gnaneswara Reddy. All rights reserved.