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 (ΔS) is calculated using heat transfer (δQ) from the peripheral skin and finger skin temperature (Tf). 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 (ΔS) is postulated as entropy damage (ΔSD), which is a metric for measuring the aging or system degradation. The aging-ratio, Aaging-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 t-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.
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.
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.
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.
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 (l/D, LR = 0.30, 0.44, 0.78, and 0.88) and twisted ratios (y/D, 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.
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.
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, N 2 , CO 2 , and CH 4 . 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%.
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 (ΔSBP) due to blood pressure, heart rate, and skin temperature and (b) entropy change (ΔSEMG) 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.
The paper deals with the calculation of molar refraction (RM) and polarizability (α) of antibiotic drug ciprofloxacin hydrochloride (c= 0.001–0.029 mol·dm−3) solutions in ethanol-water mixtures of different compositions (30, 50, and 70% v/v) from measured density (ρ) and refractive index (n) 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.
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.
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.
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.
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, Tc while the bottom wall is maintained at hot temperature, Th where Th>Tc. 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.
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.
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.
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.
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.
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.
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 (Wcp%) 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 (Qevap%) 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.
The universal scaling concept is applied to the low-temperature range of any liquid states and substances located between the melting (Tm) and normal boiling (Tb) 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 T-dependent density and isobaric heat capacity taken from the standard measurements at atmospheric pressure.
