Journal of Thermodynamics The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. Using Thermodynamic Degradation Approach to Quantify Human Stress Response Mon, 11 Sep 2017 09:02:08 +0000 The present study provides a thermodynamic degradation approach to model human stress response. Finger skin temperature was used as an indicator of stress response to a stressor (or stressful event) followed by a recovery. The entropy change () is calculated using heat transfer () from the peripheral skin and finger skin temperature (). It was hypothesized that the human stress response, as evidenced by finger skin temperature change, is a quasi-static process. The entropy approach is demonstrated using data from a medical school experimental study. The finger skin temperature was measured under three conditions (relaxation, stressor task, and recovery) during the physiological test profile. The entropy change () is postulated as entropy damage (), which is a metric for measuring the aging or system degradation. The aging-ratio, , that is, the ratio of entropy change due to stressor to that of recovery, is presented for both male and female subjects. The statistical -tests demonstrate statistical significance in human stress response to stressor and recovery states within and between male and female subjects. This novel approach could be valuable to medical researchers, particularly in the field of occupational health to evaluate human exposure to stressful environments. Satish Boregowda, Rod Handy, Darrah Sleeth, and Naomi Riches Copyright © 2017 Satish Boregowda et al. All rights reserved. Thermodynamics of Low-Dimensional Trapped Fermi Gases Thu, 26 Jan 2017 09:40:51 +0000 The effects of low dimensionality on the thermodynamics of a Fermi gas trapped by isotropic power-law potentials are analyzed. Particular attention is given to different characteristic temperatures that emerge, at low dimensionality, in the thermodynamic functions of state and in the thermodynamic susceptibilities (isothermal compressibility and specific heat). An energy-entropy argument that physically favors the relevance of one of these characteristic temperatures, namely, the nonvanishing temperature at which the chemical potential reaches the Fermi energy value, is presented. Such an argument allows interpreting the nonmonotonic dependence of the chemical potential on temperature, as an indicator of the appearance of a thermodynamic regime, where the equilibrium states of a trapped Fermi gas are characterized by larger fluctuations in energy and particle density as is revealed in the corresponding thermodynamics susceptibilities. Francisco J. Sevilla Copyright © 2017 Francisco J. Sevilla. All rights reserved. Influence of Chemical Reaction on Heat and Mass Transfer Flow of a Micropolar Fluid over a Permeable Channel with Radiation and Heat Generation Wed, 07 Dec 2016 07:56:55 +0000 The effects of chemical reaction on heat and mass transfer flow of a micropolar fluid in a permeable channel with heat generation and thermal radiation is studied. The Rosseland approximations are used to describe the radiative heat flux in the energy equation. The model contains nonlinear coupled partial differential equations which have been transformed into ordinary differential equation by using the similarity variables. The relevant nonlinear equations have been solved by Runge-Kutta-Fehlberg fourth fifth-order method with shooting technique. The physical significance of interesting parameters on the flow and heat transfer characteristics as well as the local skin friction coefficient, wall couple stress, and the heat transfer rate are thoroughly examined. Khilap Singh and Manoj Kumar Copyright © 2016 Khilap Singh and Manoj Kumar. All rights reserved. The Role of Soya Oil Ester in Water-Based PCM for Low Temperature Cool Energy Storage Sun, 25 Sep 2016 10:01:51 +0000 This study focuses on the preparation of the water-based phase change material (PCM) with very small soya oil solution for low temperature latent heat thermal energy storage (LHTES). Soya oil ester is soluble very well in water and acts as nucleating agent for a novel solid-liquid PCM candidate that is suitable for low temperature cool storage in the range between −9°C and −6°C. Thermal energy storage properties of the water with very small soya oil ester solution were measured by T-history method. The experimental results show that very small amount of soya oil ester in water can lower the freezing point and trigger ice nucleation for elimination of the supercooling degree. The phase transition temperatures of the water-based PCMs with soya oil as nucleate agent were lower than those of individual water. The thermal properties make it potential PCM for LHTES systems used in low temperature cool energy storage applications. I. M. Rasta, I. N. G. Wardana, N. Hamidi, and M. N. Sasongko Copyright © 2016 I. M. Rasta et al. All rights reserved. Kelvin’s Dissymmetric Models and Consistency Conditions of Multicomponent Gas-Liquid Equilibrium and Capillary Condensation Tue, 22 Mar 2016 09:51:01 +0000 To describe phase equilibrium of mixtures, we develop a nonclassical approach based on using different equations of state for gas and liquid. We show that not all the types of EOS are admissible but only those which verify some specific conditions of consistency. We developed the mathematical theory of this new approach for pure cores and for mixtures, in presence and absence of capillary forces, which leads to explicit analytical relationships for phase concentrations of chemical components. Several examples of comparison with experimental data for binary and ternary mixtures illustrate the feasibility of the suggested approach. Mikhail Panfilov and Alexandre Koldoba Copyright © 2016 Mikhail Panfilov and Alexandre Koldoba. All rights reserved. Effect of Magnetic Field on Mixed Convection Heat Transfer in a Lid-Driven Square Cavity Tue, 15 Mar 2016 12:46:03 +0000 The effect of magnetic field on fluid flow and heat transfer in two-dimensional square cavity is analyzed numerically. The vertical walls are insulated; the top wall is maintained at cold temperature, while the bottom wall is maintained at hot temperature, where . The dimensionless governing equations are solved using finite volume method and SIMPLE algorithm. The streamlines and isotherm plots and the variation of Nusselt numbers on hot and cold walls are presented. N. A. Bakar, A. Karimipour, and R. Roslan Copyright © 2016 N. A. Bakar et al. All rights reserved. Measuring Entropy Change in a Human Physiological System Mon, 22 Feb 2016 16:46:06 +0000 The paper presents a novel approach involving the use of Maxwell relations to combine multiple physiological measures to provide a measure of entropy change. The physiological measures included blood pressure (BP), heart rate (HR), skin temperature (ST), electromyogram (EMG), and electrodermal response (EDR). The multiple time-series physiological data were collected from eight subjects in an experimental pilot study conducted at the Human Engineering Laboratory of NASA Langley Research Center. The methodology included data collection during a relaxation period of eighteen minutes followed by a sixty-minute cognitive task. Two types of entropy change were computed: (a) entropy change () due to blood pressure, heart rate, and skin temperature and (b) entropy change () due to electromyogram, electrodermal response, and skin temperature. The results demonstrate that entropy change provides a valuable composite measure of individual physiological response to various stressors that could be valuable in the areas of medical research, diagnosis, and clinical practice. Satish Boregowda, Rod Handy, Darrah Sleeth, and Andrew Merryweather Copyright © 2016 Satish Boregowda et al. All rights reserved. Analysis of Effect of Heat Pipe Parameters in Minimising the Entropy Generation Rate Wed, 03 Feb 2016 07:24:44 +0000 Heat transfer and fluid flow in the heat pipe system result in thermodynamic irreversibility generating entropy. The minimum entropy generation principle can be used for optimum design of flat heat pipe. The objective of the present work is to minimise the total entropy generation rate as the objective function with different parameters of the flat heat pipe subjected to some constraints. These constraints constitute the limitations on the heat transport capacity of the heat pipe. This physical nonlinear programming problem with nonlinear constraints is solved using LINGO 15.0 software, which enables finding optimum values for the independent design variables for which entropy generation is minimum. The effect of heat load, length, and sink temperature on design variables and corresponding entropy generation is studied. The second law analysis using minimum entropy generation principle is found to be effective in designing performance enhanced heat pipe. Rakesh Hari and Chandrasekharan Muraleedharan Copyright © 2016 Rakesh Hari and Chandrasekharan Muraleedharan. All rights reserved. Turbulent Forced Convection and Heat Transfer Characteristic in a Circular Tube with Modified-Twisted Tapes Mon, 01 Feb 2016 09:32:33 +0000 Heat transfer, pressure loss, and thermal performance assessment in a circular tube heat exchanger with modified-twisted tapes are reported. The rectangular holes are punched out from the general twisted tape to reduce the pressure loss. The influences of the hole sizes (, LR = 0.30, 0.44, 0.78, and 0.88) and twisted ratios (, TR = 1, 1.5, 2, and 4) for the single and double twisted tapes are investigated with a numerical method at turbulent regime, Re = 3000–10,000. The finite volume method and the SIMPLE algorithm are used to investigate for the current research. The numerical results are reported in terms of flow structure and heat transfer behavior and compared with the smooth tube and the regular twisted tape. It is found that the modified-twisted tape provides higher heat transfer rate than the smooth tube due to the longitudinal vortex flows, created by the twisted tape. The longitudinal vortex flows help to increase fluid mixing. The rectangular punched holes of the twisted tape can reduce the pressure loss of the heating system. In addition, the maximum thermal enhancement factor is around 1.39 and 1.31 for the double twisted tape and single twisted tape, respectively, at Re = 3000, LR = 0.78, and TR = 1. Amnart Boonloi and Withada Jedsadaratanachai Copyright © 2016 Amnart Boonloi and Withada Jedsadaratanachai. All rights reserved. Historical Prospective: Boltzmann’s versus Planck’s State Counting—Why Boltzmann Did Not Arrive at Planck’s Distribution Law Wed, 27 Jan 2016 11:15:32 +0000 Why does Planck (1900), referring to Boltzmann’s 1877 probabilistic treatment, obtain his quantum distribution function while Boltzmann did not? To answer this question, both treatments are compared on the basis of Boltzmann’s 1868 three-level scheme (configuration—occupation—occupancy). Some calculations by Planck (1900, 1901, and 1913) and Einstein (1907) are also sketched. For obtaining a quantum distribution, it is crucial to stick with a discrete energy spectrum and to make the limit transitions to infinity at the right place. For correct state counting, the concept of interchangeability of particles is superior to that of indistinguishability. Peter Enders Copyright © 2016 Peter Enders. All rights reserved. Density and Heat Capacity of Liquids from Speed of Sound Wed, 20 Jan 2016 13:22:30 +0000 Two different methods for deriving the density and isobaric heat capacity of liquids in the subcritical pressure range, from the speed of sound, are recommended. In each method, corresponding set of differential equations relating these properties is solved as the initial boundary value problem (IBVP). The initial values are specified at the lowest pressure of the range and the boundary values along the saturation line. In the first method, numerical integration is performed along the paths connecting the Chebyshev points of the second kind between the minimum and maximum temperature at each pressure. In the second method, numerical integration is performed along the isotherms distributed in the same way, with the temperature range being extended to the saturation line after each integration step. The methods are tested with the following substances: Ar, N2, CO2, and CH4. The results obtained for the density and isobaric heat capacity have the average absolute deviation from the reference data of 0.0005% and 0.0219%, respectively. These results served as the initial values for deriving the same properties in the transcritical pressure range up to the pressure approximately twice as large as the critical pressure. The results obtained in this pressure range have respective deviations of 0.0019% and 0.1303%. Muhamed Bijedić and Sabina Begić Copyright © 2016 Muhamed Bijedić and Sabina Begić. All rights reserved. Treatment of Wastewater from a Dairy Industry Using Rice Husk as Adsorbent: Treatment Efficiency, Isotherm, Thermodynamics, and Kinetics Modelling Wed, 20 Jan 2016 13:21:50 +0000 Effluent from milk processing unit contains soluble organics, suspended solids, and trace organics releasing gases, causing taste and odor, and imparting colour and turbidity produced as a result of high consumption of water from the manufacturing process, utilities and service section, chemicals, and residues of technological additives used in individual operations which makes it crucial matter to be treated for preserving the aesthetics of the environment. In this experimental study after determination of the initial parameters of the raw wastewater it was subjected to batch adsorption study using rice husk. The effects of contact time, initial wastewater concentration, pH, adsorbent dosage, solution temperature and the adsorption kinetics, isotherm, and thermodynamic parameters were investigated. The phenomenon of adsorption was favoured at a lower temperature and lower pH in this case. Maximum removal as high as 92.5% could be achieved using an adsorbent dosage of 5 g/L, pH of 2, and temperature of 30°C. The adsorption kinetics and the isotherm studies showed that the pseudo-second-order model and the Langmuir isotherm were the best choices to describe the adsorption behavior. The thermodynamic parameters suggested that not only was the adsorption by rice husk spontaneous and exothermic in nature but also the negative entropy change indicated enthalpy driven process. Uttarini Pathak, Papita Das, Prasanta Banerjee, and Siddhartha Datta Copyright © 2016 Uttarini Pathak et al. All rights reserved. Density and Optical Properties of {Ciprofloxacin Hydrochloride + Aqueous-Ethanol} Mixtures at 30°C Mon, 18 Jan 2016 12:03:34 +0000 The paper deals with the calculation of molar refraction () and polarizability () of antibiotic drug ciprofloxacin hydrochloride ( = 0.001–0.029 mol·dm−3) solutions in ethanol-water mixtures of different compositions (30, 50, and 70% v/v) from measured density () and refractive index () at 30°C. The effect of drug concentration and composition of ethanol-water mixtures on density and optical properties of drug solutions has been described. S. D. Deosarkar, S. S. Birajdar, R. T. Sawale, M. P. Pawar, and A. M. Thakre Copyright © 2016 S. D. Deosarkar et al. All rights reserved. Enhancement of Integrated Solar Collector with Spherical Capsules PCM Affected by Additive Aluminum Powder Sun, 17 Jan 2016 16:33:19 +0000 This research aims to study, analyze, design, and construct a solar air heater combined with an appropriate phase-change material (PCM) unit. This solar air heater is analogous to a collector integrating a thermal storage unit and a solar thermal collector. In this study, such single-pass solar air heater in amalgamation with PCM was constructed, and several tests were conducted on this device. During the experiments for the solar collector with PCM (spherical capsules), the temperature varied between 30°C and 35°C, and the air mass flow rate ranged between 0.03 and 0.09 kg/s. Results confirmed the predicted experimental findings. With the use of paraffin wax-aluminum composite, the thermal storage efficiency of the constructed solar air heater reached a maximum value of 71% at 0.05 kg/s mass flow rate, its charging time decreased by almost 70%, and its cooling rate increased. The thermal storage efficiency of the compound composite was 76.8% at 0.07 kg/s mass flow rate. The results also indicated that the time of charging decreased by almost 60% with the use of paraffin wax-aluminum composite. Fatah O. Al Ghuol, K. Sopian, and Shahrir Abdullah Copyright © 2016 Fatah O. Al Ghuol et al. All rights reserved. Elastodynamic Response of Thermal Laser Pulse in Micropolar Thermoelastic Mass Diffusion Medium Mon, 04 Jan 2016 13:12:37 +0000 The present investigation deals with the deformation in micropolar thermoelastic diffusion medium due to inclined load subjected to thermal laser pulse. Normal mode analysis technique is used to solve the problem. The inclined load is assumed to be a linear combination of a normal load and a tangential load. The closed form expressions of normal stress, tangential stress, couple stress, temperature distribution, and mass concentration are obtained. A computer program has been developed to derive the physical quantities numerically. The variation of normal stress, tangential stress, coupled stress, temperature change, and mass concentration is depicted graphically to show the effect of relaxation times and mass concentration. Some particular cases of interest are deduced from the present investigation. Rajneesh Kumar and Arvind Kumar Copyright © 2016 Rajneesh Kumar and Arvind Kumar. All rights reserved. Thermal-Hydraulics Study of a 75 kWth Aqueous Homogeneous Reactor for 99Mo Production Mon, 28 Dec 2015 08:47:48 +0000 is a very useful radioisotope, which is used in nearly 80% of all nuclear medicine procedures. is produced from 99Mo decay. A potentially advantageous alternative to meeting current and future demand for 99Mo is the use of Aqueous Homogeneous Reactors (AHR). In this paper, a thermal-hydraulics study of the core of a 75 kWth AHR conceptual design based on the ARGUS reactor for 99Mo production is presented. As the ARGUS heat removal systems were designed for working at 20 kWth, the main objective of the thermal-hydraulics study was evaluating the heat removal systems in order to show that sufficient cooling capacity exists to prevent fuel solution overheating. The numerical simulations of an AHR model were carried out using the Computational Fluid Dynamic (CFD) code ANSYS CFX 14. Evaluation shows that the ARGUS heat removal systems working at 75 kWth are not able to provide sufficient cooling capacity to prevent fuel solution overheating. To solve this problem, the number of coiled cooling pipes inside the core was increased from one to five. The results of the CFD simulations with this modification in the design show that acceptable temperature distributions can be obtained. Daniel Milian Pérez, Daniel E. Milian Lorenzo, Lorena P. Rodriguez Garcia, Manuel Cadavid Rodríguez, Carlos A. Brayner de Oliveira Lira, Carlos R. García Hernández, and Jesús Salomón Llanes Copyright © 2015 Daniel Milian Pérez et al. All rights reserved. Scaling Model of Low-Temperature Transport Properties for Molecular and Ionic Liquids Sun, 06 Dec 2015 09:57:14 +0000 The universal scaling concept is applied to the low-temperature range of any liquid states and substances located between the melting () and normal boiling () points far away from the critical region. The physical reason to develop such approach is the revealed collapse of all low-temperature isotherms onto the single universal one argued by the model of fluctuational thermodynamics (FT) proposed recently by author. The pressure reduced by the molecular parameters of the effective short-range Lennard-Jones (LJ) potential depends here only on the reduced density. To demonstrate the extraordinary predictive abilities of the developed low-temperature scaling model it has been applied to the prediction of equilibrium and transport (kinetic and dynamic viscosity, self-diffusion, and thermal conductivity) properties not only for molecular liquids but also for molten organic salts termed ionic liquids (ILs). The best argument in favor of the proposed methodology is the appropriate consistency with the scarce experiments prediction of transport coefficients for ILs on the base of universal scaling function constructed for the simplest LJ-like liquid argon. The only input data of any substance for prediction are the linear approximations of -dependent density and isobaric heat capacity taken from the standard measurements at atmospheric pressure. Vitaly B. Rogankov Copyright © 2015 Vitaly B. Rogankov. 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.