Journal of Thermodynamics The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Effect of Longitudinal-External-Fins on Fluid Flow Characteristics for Wing-Shaped Tubes Bundle in Crossflow Thu, 05 Nov 2015 06:55:36 +0000 A numerical study is conducted to clarify fluid-flow characteristics, pressure drop coefficient (), and the average skin friction coefficient () for wing-shaped-tubes bundle with longitudinal fins at downstream side of the tube using the commercial CFD FLUENT software package. The air-side ranges from 1800 to 9700. The tubes are employed with various fin heights () and fin thicknesses () such as 2 mm ≤ ≤ 12 mm and 1.5 mm ≤ ≤ 3.5 mm at the considered range. Results indicate that increases with for all . decreases with for all values for 1800 ≤ ≤ 4200 and then increases for 4200 ≤ ≤ 10000. Lowest values of , , and pumping power (PP) occurred at = 6 mm. Values of for = 6 mm are lower than those of NOF and = 2 mm by about 73 % and 32 %, respectively, at = 4000. decreases with . has negligible effect on . increases for 1.5 mm ≤ ≤ 2.5 mm while decreases with 2.5 mm < ≤ 3.5 mm for the considered range except for = 1850. Sayed Ahmed E. Sayed Ahmed, Osama M. Mesalhy, and Mohamed A. Abdelatief Copyright © 2015 Sayed Ahmed E. Sayed Ahmed et al. All rights reserved. Thermodynamic Modeling of Surface Tension of Aqueous Electrolyte Solution by Competitive Adsorption Model Mon, 02 Nov 2015 12:18:10 +0000 Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other temperatures in binary and ternary system of aqueous electrolyte solution are predicted. The average absolute deviations for calculation of surface tension of binary and mixed electrolyte systems by new model are 1.98 and 1.70%, respectively. Mohamad Javad Kamali, Zakarya Kamali, and Gholamhossein Vatankhah Copyright © 2015 Mohamad Javad Kamali et al. All rights reserved. Thermoacoustic Instability in a Rijke Tube with a Distributed Heat Source Tue, 27 Oct 2015 09:48:58 +0000 A Rijke tube with a distributed heat source is investigated. Driven by the widely existing thermoacoustic instability in lean premixed gas turbine combustors, this work aims to explore the physicochemical underpinning and assist in the elucidation and analysis of this problem. The heat release model consists of a row of distributed heat sources with individual heat release rates. The integrated heat release rate is then coupled with the acoustic perturbation for thermoacoustic analysis. A continuation approach is employed to conduct the bifurcation analysis and capture the nonlinear behaviour inherent in the system. Unlike the conventional approach by the Galerkin method, the acoustic equations are originally discretized using the Method of Lines (MOL) to build up a dynamic system. The model is first validated and shown to yield good predictions with available experimental data. Influences of multiple heat sources, time delay, and heat release distribution are then studied to reveal the extensive nonlinear characteristics involved in the case of a distributed heat source. It is found that distributed heat source plays an important role in determining the stability of a thermoacoustic system. Xiaochuan Yang, Ali Turan, and Shenghui Lei Copyright © 2015 Xiaochuan Yang et al. All rights reserved. The Influence of the Punched Delta Wings on Flow Pattern and Heat Transfer Characteristic in a Fin-and-Oval-Tube Heat Exchanger Mon, 26 Oct 2015 08:57:41 +0000 3D numerical investigations are performed to study the heat transfer, friction factor, and thermal performance of a fin-and-oval heat exchanger with punched delta wings for a range of 500 ≤ Re ≤ 2500 (based on the hydraulic diameter). The influences of the punched angles, 20°, 30°, and 45°, flow directions, wing tips pointing downstream and upstream, and pitch ratios, 2, 3, 4, 5, and 6, are investigated. The results show that the use of the punched delta wings in the fin-and-oval-tube heat exchanger leads to an enhancement in the heat transfer and friction loss as compared to the plain fin for all cases (/ and higher than 1). The enhancements of the heat transfer and friction factor are around 1.01–1.22 and 1.37–2.65 times higher than the base case, respectively. The punched delta wings create the vortex flows through the test section that helps enhance the strength of the impinging flow on the tube walls. The impingement of the fluid flow is an important key to augment the heat transfer rate and thermal performance in the heat exchanger. Amnart Boonloi Copyright © 2015 Amnart Boonloi. All rights reserved. Influence of Exhaust Gas Recirculation, and Injection Timing on the Combustion, Performance and Emission Characteristics of a Cylinder Head Porous Medium Engine Mon, 12 Oct 2015 11:03:36 +0000 Homogeneous combustion has the potential of achieving both near-zero emissions and low specific fuel consumption. However, the accomplishment of homogeneous combustion depends on the air flow structure inside the combustion chamber, fuel injection conditions, and turbulence as well as ignition conditions. Various methods and procedures are being adopted to establish the homogeneous combustion inside the engine cylinder. In this research work, a highly porous ceramic structure was introduced into the combustion chamber (underside of the cylinder head). The influence of operating parameters such as exhaust gas recirculation (EGR) and injection timing on the combustion, performance, and emission characteristics of such developed engine was investigated in this research work. Chidambaram Kannan and Thulasi Vijayakumar Copyright © 2015 Chidambaram Kannan and Thulasi Vijayakumar. All rights reserved. Effect of Condenser Fouling on Performance of Vapor Compression Refrigeration System Mon, 05 Oct 2015 08:54:08 +0000 Effect of condenser fouling is evaluated on the performance of a vapour compression system with refrigerants HFO1234yf and HFO1234ze as an alternative to HFC134a. The condenser coolant temperature has been varied between 35 and 40°C to evaluate the effect of fouling at different condenser temperatures. A simulation model is developed in EES for computing the results. The results have been computed by varying condenser conductance. The same has been validated with literature available before calculating the results. It is observed that the condenser fouling has larger effect on compressor power (%) as it increases up to 9.12 for R1234yf and 7.41 for R1234ze, whereas for R134a its value increases up to 7.38. The cooling capacity (%) decreases up to 13.25 for R1234yf and 8.62 for R1234ze, whereas for R134a its value decreases up to 8.76. The maximum percentage of decrease in value of COP is up to 19.29 for R1234yf and 14.47 for R1234ze, whereas for R134a its value decreases up to 14.49. The second-law efficiency is also observed to decrease with decrease in the condenser conductance. The performance of HFO1234ze is found to be better under fouled conditions in comparison to R134a and R1234yf. Naveen Solanki, Akhilesh Arora, and S. C. Kaushik Copyright © 2015 Naveen Solanki et al. All rights reserved. Volumetric Behavior of Binary Mixtures of Alkoxyethanols and Some Selected Amines at 298.15 K Mon, 23 Feb 2015 12:49:40 +0000 Densities of binary mixtures of 2-methoxyethanol (2-MeO-EtOH) and 2-ethoxyethanol (2-EtO-EtOH) with hexylamine (HLA), diethylamine (DEA), triethylamine (TEA), tert-butylamine (TBA), aniline (ANL), and benzylamine (BLA) have been determined at varying compositions of the alkoxyalkanols at 298.15 K. The excess molar volumes, VE, of the binary mixtures were calculated from the experimental density data of the mixtures and the component single solvents. The calculated excess molar volumes were fitted into the Redlich-Kister polynomial to obtain the fitting coefficients and standard deviations. The excess molar volumes of the binary mixtures of all the solvent systems investigated were negative over the entire range of the solvents composition. The negative values were attributed to stronger hydrogen bond formations between the unlike molecules of mixtures than those between the like molecules of the pure components. The magnitude of the excess molar volumes of the binary mixtures of 2-methoxyethanol and the aliphatic amines were in the order TBA > TEA > DEA > HEA. For the two aromatic amines, the magnitudes were in the order BLA > ANL. For binary mixtures of the amines and 2-ethoxyethanol, the magnitudes were in the order DEA > TEA > TBA > HEA at compositions where the mole fraction of 2-EtO-EtOH was ≤0.5 and TBA > TEA > DEA > HEA above 0.5 mole fraction of 2-EtO-EtOH. Ayasen Jermaine Kemeakegha, Grace Agbizu Cookey, and Welford-Abbey Lolo Izonfuo Copyright © 2015 Ayasen Jermaine Kemeakegha et al. All rights reserved. Symmetry Properties of Reciprocity Relations and Conditions for Minimum Entropy Production Law (In)validity Mon, 23 Feb 2015 12:21:41 +0000 Consequences of symmetry properties of the phenomenological kinetic coefficients in Onsager-Casimir reciprocity relations for the minimum entropy production law validity are studied. The usually accepted symmetry requirement of the all cross kinetic coefficients for the validity of this law is found to be too strict. Marian Štrunc and Milena Kheilová Copyright © 2015 Marian Štrunc and Milena Kheilová. All rights reserved. Gibbs Thermodynamics of the Renninger-Wilemski Problem Wed, 11 Feb 2015 11:32:01 +0000 The Renninger-Wilemski problem in nucleation is analyzed. The Gibbs dividing surfaces method with external parameters is used to enrich the initial model. It is shown that both the traditional (Doyle) model and the Renninger-Wilemski model are not complete ones and, namely, the Gibbs dividing surface approach can solve this problem. It is shown that the application of the Gibbs approach also requires some model constructions. The simplified Gibbs model is proposed. It is shown that the simplified Gibbs model gives for the height of activation barrier the same numerical results as the Renninger-Wilemski model. Victor Kurasov Copyright © 2015 Victor Kurasov. All rights reserved. Shear Thickening in Concentrated Soft Sphere Colloidal Suspensions: A Shear Induced Phase Transition Thu, 08 Jan 2015 06:33:05 +0000 A model of shear thickening in dense suspensions of Brownian soft sphere colloidal particles is established. It suggests that shear thickening in soft sphere suspensions can be interpreted as a shear induced phase transition. Based on a Landau model of the coagulation transition of stabilized colloidal particles, taking the coupling between order parameter fluctuations and the local strain-field into account, the model suggests the occurrence of clusters of coagulated particles (subcritical bubbles) by applying a continuous shear perturbation. The critical shear stress of shear thickening in soft sphere suspensions is derived while reversible shear thickening and irreversible shear thickening have the same origin. The comparison of the theory with an experimental investigation of electrically stabilized colloidal suspensions confirms the presented approach. Joachim Kaldasch, Bernhard Senge, and Jozua Laven Copyright © 2015 Joachim Kaldasch et al. All rights reserved. Thermoacoustic, Volumetric, and Viscometric Investigations in Binary Liquid System of Cyclohexanone with Benzyl Benzoate at T = 308.15, 313.15, and 318.15 K Mon, 29 Dec 2014 09:42:26 +0000 Ultrasonic velocities (), densities (), and viscosities () of binary liquid mixtures of cyclohexanone with benzyl benzoate, including pure liquids, over the entire composition range have been measured at 308.15 K, 313.15 K, and 318.15 K. Using the experimental results, parameters such as molar volume (), isentropic compressibility (), intermolecular free length (), acoustic impedance (), internal pressure (), enthalpy (), Gibbs free energy of activation of viscous flow (), and excess/deviation properties of these including partial molar volumes ( and ), excess partial molar volumes ( and ), partial molar volume of the components at infinite dilution (, ), and excess partial molar volume at infinite dilution (and ) have been computed. The observed negative values of , , , and and positive values of , , , , and for all the liquid mixtures studied clearly indicate the presence of strong dipole-dipole-type interactions, fitting of smaller molecules into bigger molecules. Further theoretical values of sound velocity and viscosity in the mixtures have been evaluated using various theories and have been compared with experimental values to verify the applicability of such theories to the systems studied. Sk. Md Nayeem, M. Kondaiah, K. Sreekanth, and D. Krishna Rao Copyright © 2014 Sk. Md Nayeem et al. All rights reserved. Towards the Equation of State for Neutral (C2H4), Polar (H2O), and Ionic ([bmim][BF4], [bmim][PF6], [pmmim][Tf2N]) Liquids Tue, 16 Dec 2014 13:31:51 +0000 Despite considerable effort of experimentalists no reliable vapor-liquid coexistence at very small pressures and liquid-solid coexistence at high pressures have been until now observed in the working range of temperature / for ionic liquids. The measurements of high-pressure properties in low-temperature stable liquid are relatively scarce while the strong influence of their consistency on the phase equilibrium prediction is obvious. In this work we discuss the applicability of fluctuational-thermodynamic methodology and respective equation of state to correlate the properties of any (neutral, polar, ionic) liquids since our ultimate goal is the simple reference predictive model to describe vapor-liquid, liquid-liquid, and liquid-solid equilibria of mixtures containing above components. It is shown that the inconsistencies among existing volumetric measurements and the strong dependence of the mechanical and, especially, caloric derived properties on the shape of the functions chosen to fit the experimental data can be resolved in the framework of fluctuational-thermodynamic equation of state. To illustrate its results the comparison with the known experimental data for [bmim][BF4] and [bmim][PF6] as well as with the lattice-fluid equation of state and the methodology of thermodynamic integration is represented. It corroborates the thermodynamic consistency of predictions and excellent correlation of derived properties over the wide range of pressures /. Vitaly B. Rogankov and Valeriy I. Levchenko Copyright © 2014 Vitaly B. Rogankov and Valeriy I. Levchenko. All rights reserved. Entropy Growth Is the Manifestation of Spontaneity Sun, 07 Dec 2014 08:22:59 +0000 Every student of thermodynamics grasps entropy growth in terms of dissipation of energy. The real nature of energy and entropy is subtle. This critical review of the evolution of thermodynamic thought uncovers the remarkable advance on our understanding of energy made by Kelvin with his dissipation of energy proposition. Maxwell and Planck, however, pointed out that dissipation of energy does not exhaust growth of entropy (i.e., the idea of spontaneity), and in fact, as it is shown here, Kelvin’s proposition of dissipation of energy (1852) is subsumed under the principle of the increase of entropy (Clausius, 1865). It is necessary, therefore, for thermodynamics to become a coherent conceptual system, to introduce spontaneity as an independent concept. Instead of the heat-work dyad framework, the introduction of spontaneity entails energy transformation to be viewed in terms of a triad framework of heat (from the reservoir)-work-spontaneity. Spontaneity is the new energy in the triad framework, and it is also clear that energy commodity (fungible energy or energy carriers) is only one kind of spontaneity, stock spontaneity; the other kind is ongoing spontaneity, the consideration of which is necessary for comprehending problems of homeostasis in both the organic and inorganic worlds. Lin-Shu Wang Copyright © 2014 Lin-Shu Wang. All rights reserved. Separation of Methylene Blue Dye from Aqueous Solution Using Triton X-114 Surfactant Tue, 02 Dec 2014 12:55:39 +0000 In this study, the interaction energy between Triton X-114 surfactant + methylene blue or water and methylene blue + water was investigated using Hartree-Fock (HF) theory with 6- basis set. The results of structures and interaction energies show that these complexes have good physical and chemical interactions at atom and molecular levels. However, the Triton X-114 surfactant + methylene blue complex shows stronger molecular interaction compared to other complexes systems. The order of the interaction energy is 4303.472023 (Triton X-114 surfactant + water) > 1222.962 (methylene blue + water) > 3573.28 (Triton X-114 surfactant + methylene blue) kJ·mole−1. Subsequently, the cloud point extraction was carried out for 15 ppm of methylene blue in a mixture at 313.15 and 323.15 K over the surfactant concentration range from 0.01 M to 0.1 M. From the measured data, the excess molar volume was calculated for both phases. The results show a positive deviation in the dilute phase and a negative deviation in the surfactant rich phase. It is confirmed that the interaction between Triton X-114 and methylene blue is stronger than other complex systems due to the presence of chemical and structural orientation. The concentration of dyes and surfactant in the feed mixture and temperature effect in both phases has been studied. In addition, the thermodynamics feasibility and efficiency of the process have also been investigated. Arunagiri Appusamy, Prabisha Purushothaman, Kalaichelvi Ponnusamy, and Anantharaj Ramalingam Copyright © 2014 Arunagiri Appusamy et al. All rights reserved. Thermohydraulic Performance of a Series of In-Line Noncircular Ducts in a Parallel Plate Channel Sun, 21 Sep 2014 09:21:24 +0000 Heat transfer and fluid flow characteristics for two-dimensional laminar flow at low Reynolds number for five in-line ducts of various nonconventional cross-sections in a parallel plate channel are studied in this paper. The governing equations were solved using finite-volume method. Commercial CFD software, ANSYS Fluent 14.5, was used to solve this problem. A total of three different nonconventional, noncircular cross-section ducts and their characteristics are compared with those of circular cross-section ducts. Shape-2 ducts offered minimum flow resistance and maximum heat transfer rate most of the time. Shape-3 ducts at Re < 100 and Shape-2 ducts at Re > 100 can be considered to give out the optimum results. Siddharth D. Mhaske, Soby P. Sunny, Sachin L. Borse, and Yash B. Parikh Copyright © 2014 Siddharth D. Mhaske et al. All rights reserved. Second Law Analysis for Third-Grade Fluid with Variable Properties Mon, 08 Sep 2014 00:00:00 +0000 This paper investigates the entropy generation in a third-grade fluid flow with variable properties through a channel. Approximate solutions to the nonlinear boundary-value problem are obtained using Adomian decomposition method (ADM). Variation of important parameters on the fluid velocity, temperature distribution, entropy generation and irreversibility ratio are presented graphically and discussed. Samuel O. Adesanya Copyright © 2014 Samuel O. Adesanya. All rights reserved. Effect of Initial Stress on the Propagation Characteristics of Waves in Fiber-Reinforced Transversely Isotropic Thermoelastic Material under an Inviscid Liquid Layer Tue, 26 Aug 2014 05:16:48 +0000 The present investigation deals with the propagation of waves in fiber-reinforced transversely isotropic thermoelastic solid half space with initial stresses under a layer of inviscid liquid. The secular equation for surface equation in compact form is derived after developing the mathematical model. The phase velocity and attenuation coefficients of plane waves are studied numerically for a particular model. Effects of initial stress and thickness of the layer on the phase velocity, attenuation coefficient, and specific loss of energy are predicted graphically in the certain model. A particular case of Rayleigh wave has been discussed and the dispersion curves of the phase velocity and attenuation coefficients have also been presented graphically. Some other particular cases are also deduced from the present investigation. Rajneesh Kumar, Sanjeev Ahuja, and S. K. Garg Copyright © 2014 Rajneesh Kumar et al. All rights reserved. Thermodynamic Properties of Vapors from Speed of Sound Mon, 21 Jul 2014 07:46:46 +0000 A numerical procedure for deriving the thermodynamic properties , , and of the vapor phase in the subcritical temperature range from the speed of sound is presented. The set of differential equations connecting these properties with the speed of sound is solved as the initial-value problem in domain . The initial values of and are specified along the isotherm with the highest temperature, at a several values of [0.1, 1.0]. The values of are generated by the reference equation of state, while the values of are derived from the speed of sound, by solving another set of differential equations in domain in the transcritical temperature range. This set of equations is solved as the initial-boundary-value problem. The initial values of and are specified along the isochore in the limit of the ideal gas, at several isotherms distributed according to the Chebyshev points of the second kind. The boundary values of are specified along the same isotherm and along another isotherm with a higher temperature, at several values of . The procedure is tested on Ar, N2, CH4, and CO2, with the mean AADs for , , and at 0.0003%, 0.0046%, and 0.0061%, respectively (0.0007%, 0.0130%, and 0.0189% along the saturation line). Muhamed Bijedić and Sabina Begić Copyright © 2014 Muhamed Bijedić and Sabina Begić. All rights reserved. Pedagogical Visualization of a Nonideal Carnot Engine Mon, 21 Jul 2014 06:32:05 +0000 We have implemented a visualization tool for the demonstration of a nonideal Carnot engine, operating at finite time. The cycle time can be varied using a slide bar and the pressure-volume, temperature-entropy, power-time, and efficiency-time diagrams change interactively and are shown on one screen. We have evaluated the visualization tool among engineering students at university level during an introductory course on thermodynamics and we review and discuss the outcome of the evaluation. Jonas Johansson Copyright © 2014 Jonas Johansson. All rights reserved. Studies on Thermophysical Properties of CaO and MgO by -Ray Attenuation Tue, 15 Apr 2014 00:00:00 +0000 The study on temperature dependent γ-ray attenuation and thermophysical properties of CaO and MgO has been carried out in the temperature range 300 K–1250 K using different energies of γ-beam, namely, Am (0.0595 MeV), Cs (0.66 MeV), and Co (1.173 MeV and 1.332 MeV) on γ-ray densitometer fabricated in our laboratory. The linear attenuation coefficients (μl) for the pellets of CaO and MgO as a function of temperature have been determined using γ-beam of different energies. The coefficients of temperature dependence of density have been reported. The variation of density and linear thermal expansion of CaO and MgO in the temperature range of 300 K–1250 K has been studied and compared with the results available in the literature. The temperature dependence of linear attenuation coefficients, density, and thermal expansion has been represented by second degree polynomial. Volume thermal expansion coefficients have been reported. A. S. Madhusudhan Rao and K. Narender Copyright © 2014 A. S. Madhusudhan Rao and K. Narender. All rights reserved. Performance Evaluation of Refrigeration Units in Natural Gas Liquid Extraction Plant Tue, 25 Mar 2014 09:24:29 +0000 This paper has applied thermodynamics principles to evaluate the reliability of 390 m3/hr natural gas processing plant. The thermodynamics equations were utilized in the evaluation, characterization, and numerical simulation of key process parameters in natural gas liquid extraction plant. The results obtained show the comparison of the coefficient of performance, compression ratio, isentropic work, actual work, electrical power requirements, cooling water consumption in intercoolers, compressor power output, compressor capacity, and isentropic, volumetric, and mechanical efficiency of the two-stage refrigeration unit with a flash gas economizer and these were compared with the designed specifications. The second law of thermodynamics was applied in analyzing the refrigeration unit and the result shows that exergetic losses or lost work due to irreversibility falls within operating limit that is less than 1.0%. Similarly, the performance of expansion turbine (expander) parameters was monitored and the results indicate a considerable decrease in turbine efficiencies as the inlet gas pressure increases resulting in an increased power output of the turbine leading to a higher liquefaction rate. Awajiogak Anthony Ujile and Dirina Amesi Copyright © 2014 Awajiogak Anthony Ujile and Dirina Amesi. All rights reserved. Acoustic and Volumetric Properties of Mixture of (N,N-Dimethylacetamide + Ethyl Acrylate) with 1-Butanol or iso-Butanol or t-Butanol at 308.15 K Thu, 27 Feb 2014 07:03:26 +0000 Densities, , and ultrasonic speeds, of mixtures of 1-butanol or iso-butanol or t-butanol with equimolar mixture of (N,N-dimethylacetamide + Ethyl acrylate) over the entire composition range have been measured at  K. Using the experimental results, deviation in ultrasonic speed, , deviation in isentropic compressibility, , excess molar volume, , excess intermolecular free length, , and excess acoustic impedance, , have been calculated. The variation of these properties with composition of the mixtures has been discussed in terms of molecular interactions in these mixtures. The deviation/excess properties have been fitted to Redlich-Kister type polynomial and the corresponding standard deviations have been calculated. Negative values of , , and and positive values of , and are observed over the entire composition range. The observed negative and positive values of deviation/excess properties are attributed to the strong interactions between the unlike molecules of the mixtures. Further theoretical values of sound velocity in the mixtures have been evaluated using various theories and compared with experimental sound velocities to verify the applicability of such theories to the systems studied. Theoretical ultrasonic velocity data has been used to study molecular interactions in the systems investigated. M. Kondaiah, K. Sreekanth, D. Sravana Kumar, and D. Krishna Rao Copyright © 2014 M. Kondaiah et al. All rights reserved. Thermophysical Properties of Binary Mixtures of Dimethylsulfoxide with 1-Phenylethanone and 1,4-Dimethylbenzene at Various Temperatures Mon, 24 Feb 2014 13:40:56 +0000 This research article reports the experimental results of the density, viscosity, refractive index, and speed of sound analysis of binary mixtures of dimethylsulfoxide (DMSO) + 1-phenylethanone (acetophenone) and + 1,4-dimethylbenzene (para-xylene) over the whole composition range at 313.15, 318.15, 323.15, and 328.15 K and at atmospheric pressure. The excess molar volumes (), viscosity deviations (), excess Gibbs energy of activation (), deviations in isentropic compressibility (), deviations in speed of sound (), and deviations in the molar refraction () were calculated from the experimental data. The computed quantities were fitted to the Redlich-Kister equation to derive the coefficients and estimate the standard error values. The viscosities have also been correlated with two, and three-parameter models, that is, Heric correlation, McAllister model, and Grunberg-Nissan correlation, respectively. Harmandeep Singh Gill and V. K. Rattan Copyright © 2014 Harmandeep Singh Gill and V. K. Rattan. All rights reserved. Thermal Performance and Economic Analysis of 210 MWe Coal-Fired Power Plant Wed, 12 Feb 2014 11:10:02 +0000 This paper presents the thermal and economic performance of a 210 MWe coal-fired power plant situated in North India. Analysis is used to predict coal consumption rate, overall thermal efficiency, mass flow rate of steam through boiler, and Net present value (NPV) of plant for given load. Thermodynamic analysis was carried out using mass and energy equations followed by empirical correlations. Predicted mass flow rate of steam, coal consumption rate, and thermal efficiency give fair agreement with plant operating data. The economic analysis includes operational activities such as equipment cost, fuel cost, operations and maintenance cost, revenue, and plant net present value. From economic point of view, the effect of condensate extraction pump redundancy on net present value is observed to be sensitive than boiler feed pump redundancy. Ravinder Kumar, Avdhesh Kr. Sharma, and P. C. Tewari Copyright © 2014 Ravinder Kumar et al. All rights reserved. Second Law Analysis of Laminar Flow in a Circular Pipe Immersed in an Isothermal Fluid Tue, 31 Dec 2013 12:31:34 +0000 Entropy generation and pumping power to heat transfer ratio (PPR) of a laminar flow, for a circular tube immersed in an isothermal fluid, are studied analytically in this paper. Two different fluids, namely, water and ethylene glycol, are chosen to study the influence of fluid properties on entropy generation and PPR. The expressions for dimensionless entropy generation, Bejan number and PPR are derived in a detailed way and their variations with Reynolds number, external Biot number, and the dimensionless temperature difference are illustrated. The results of the analysis are compared with those for a laminar flow in a circular tube with uniform wall temperature boundary condition. Finally, a criterion is established to determine which type of thermal boundary conditions is more suitable for a particular fluid, with respect to its influence on entropy generation. Vishal Anand and Krishna Nelanti Copyright © 2013 Vishal Anand and Krishna Nelanti. All rights reserved. Nonlinear Closure Relations for Electron Transport in Hydrodynamical Models Mon, 23 Dec 2013 09:29:15 +0000 Closure relations problem of hydrodynamical models in semiconductors is considered by expressing third- and fourth-order closure relations for the moments of the distribution function in terms of second-order Lagrange multipliers using a generalized Maxwell-Boltzmann distribution function within information theory. Calculation results are commented and compared with others to justify the accuracy of the approach developed in this paper. The comparison involves, in the first part with good agreements, the closure relations results obtained within extended thermodynamics which were checked by means of Monte Carlo simulations, in the second part, the results obtained by Grad's method which expands the distribution function up to fourth-order in Hermite polynomials. It is seen that the latter method cannot give any restriction on closure relations for higher-order moments, within the same conditions proposed in our approach. The important role of Lagrange multipliers for the determination of all closure relations is asserted. A. Salhoumi Copyright © 2013 A. Salhoumi. All rights reserved. MHD Stagnation-Point Flow of Casson Fluid and Heat Transfer over a Stretching Sheet with Thermal Radiation Thu, 10 Oct 2013 18:42:04 +0000 The two-dimensional magnetohydrodynamic (MHD) stagnation-point flow of electrically conducting non-Newtonian Casson fluid and heat transfer towards a stretching sheet have been considered. The effect of thermal radiation is also investigated. Implementing similarity transformations, the governing momentum, and energy equations are transformed to self-similar nonlinear ODEs and numerical computations are performed to solve those. The investigation reveals many important aspects of flow and heat transfer. If velocity ratio parameter (B) and magnetic parameter (M) increase, then the velocity boundary layer thickness becomes thinner. On the other hand, for Casson fluid it is found that the velocity boundary layer thickness is larger compared to that of Newtonian fluid. The magnitude of wall skin-friction coefficient reduces with Casson parameter (β). The velocity ratio parameter, Casson parameter, and magnetic parameter also have major effects on temperature distribution. The heat transfer rate is enhanced with increasing values of velocity ratio parameter. The rate of heat transfer is enhanced with increasing magnetic parameter M for B > 1 and it decreases with M for B < 1. Moreover, the presence of thermal radiation reduces temperature and thermal boundary layer thickness. Krishnendu Bhattacharyya Copyright © 2013 Krishnendu Bhattacharyya. All rights reserved. Two Temperature Magneto-Thermoelasticity with Initial Stress: State Space Formulation Mon, 30 Sep 2013 10:27:12 +0000 Magneto-thermoelastic interactions in an initially stressed isotropic homogeneous elastic half-space with two temperatures are studied using mathematical methods under the purview of the L-S model of linear theory of generalized thermoelasticity. The formalism deals with the state space approach with the purpose of counteracting the difficulties of handling the displacement potential functions. Of specific concern here is the propagation of waves owing to ramp type increase in temperature and load. The medium is considered to be permeated by a uniform magnetic field. The expressions for different field parameters such as displacement, temperature, strain, and stress in the physical domain are obtained by applying a numerical inversion technique. Results of some earlier workers have been deduced from the present formulation. Numerical work is also performed for a suitable material with the aim of illustrating the results. Sunita Deswal and Kapil Kumar Kalkal Copyright © 2013 Sunita Deswal and Kapil Kumar Kalkal. All rights reserved. Effect of Size and Shape on the Vibrational and Thermodynamic Properties of Nanomaterials Thu, 19 Sep 2013 13:13:45 +0000 A simple theoretical model is developed to study the size and shape dependence of vibrational and thermodynamic properties of nanomaterials. To show the real connection with the nanomaterials we have studied Debye temperature, Debye frequency, melting entropy, and enthalpy in different shapes, namely, spherical, nanowire, and nanofilm of -Fe, Sn, Ag, and In. The results obtained are compared with the experimental data. A good agreement between the model predictions and the experimental data supports the theory developed in the present paper. R. Kumar, G. Sharma, and M. Kumar Copyright © 2013 R. Kumar et al. All rights reserved. Batch Sorption Experiments: Langmuir and Freundlich Isotherm Studies for the Adsorption of Textile Metal Ions onto Teff Straw (Eragrostis tef) Agricultural Waste Tue, 17 Sep 2013 10:48:03 +0000 Adsorption of heavy metals (Cr, Cd, Pb, Ni, and Cu) onto Activated Teff Straw (ATS) has been studied using batch-adsorption techniques. This study was carried out to examine the adsorption capacity of the low-cost adsorbent ATS for the removal of heavy metals from textile effluents. The influence of contact time, pH, Temperature, and adsorbent dose on the adsorption process was also studied. Results revealed that adsorption rate initially increased rapidly, and the optimal removal efficiency was reached within about 1 hour. Further increase in contact time did not show significant change in equilibrium concentration; that is, the adsorption phase reached equilibrium. The adsorption isotherms could be fitted well by the Langmuir model. The value in the present investigation was less than one, indicating that the adsorption of the metal ion onto ATS is favorable. After treatment with ATS the levels of heavy metals were observed to decrease by 88% (Ni), 82.9% (Cd), 81.5% (Cu), 74.5% (Cr), and 68.9% (Pb). Results indicate that the freely abundant, locally available, low-cost adsorbent, Teff straw can be treated as economically viable for the removal of metal ions from textile effluents. Mulu Berhe Desta Copyright © 2013 Mulu Berhe Desta. All rights reserved.