International Journal of Thermophysics最新文献

This paper is a combined experimental and modeling study aimed at exploring the densities, sound speeds, and refractive indices of the ternary system MTBE + n-hexane + cyclohexane and its binary subsystems at a temperature of 298.15 K under ambient pressure conditions. Experimental data were used to derive essential properties such as excess molar volumes, excess isentropic compressibilities, and refractive index deviations. The excess and deviation properties provided invaluable insights into the interactions occurring among the mixture components. Redlich–Kister and Cibulka's equations were employed to correlate these properties for binary and ternary systems, respectively. Remarkably, the standard deviations consistently fell below the estimated uncertainties associated with the corresponding properties, attesting to the robustness of the correlations. Additionally, the Perturbed Chain Statistical Associating Fluid Theory was applied to model the density of both binary and ternary mixtures. The study also compared Schaaff’s collision factor theory and Nomoto’s relation in their ability to predict sound speeds for the investigated mixtures. Various mixing rules, including Lorentz-Lorenz, Gladstone-Dale, Laplace, and Eykman, were employed to model the refractive indices of the mixtures. The efficacy of these models in predicting the properties was evaluated using the average absolute percentage deviation between the experimental and calculated values. The modeled densities matched well with the experimental data, with overall deviations of 0.19 %, 0.38 %, and 0.25 % for the binary systems MTBE + n-hexane, MTBE + cyclohexane, and n-hexane + cyclohexane, respectively, and 0.21 % for the ternary system MTBE + n-hexane + cyclohexane. Notably, Nomoto’s relation exhibited superior performance in predicting both binary (overall deviation of 0.65 %) and ternary (deviation of 1.10 %) sound speeds. In contrast, any of the four tested mixing rules performed equally well for predicting binary and ternary refractive indices. This work contributes to the understanding of interactions between components in mixtures. It also provides valuable data for petrochemical and environmental engineers involved in designing extraction processes, processing equipment, and formulating gasoline blends that meet the industry's rigorous standards and align with environmental sustainability goals.

Mass and thermodiffusion are transport phenomena in fluid mixtures important in many applications. In this paper it is argued that these transport phenomena have even become more interesting in view of some surprising discoveries from fluctuating hydrodynamics leading to possible new emerging issues in non-equilibrium thermodynamics. A short review of the history of this subject is presented. The paper then addresses the problem that the conventional mass and thermodiffusion coefficients depend on the frame of reference. A simple solution to this problem is elucidated.

A comprehensive discussion/analysis of the published viscosity data of ethylene glycol, EG, in the temperature range from 260 (just above the freezing point) to 465 K was recently reported in this journal. It was found that some of the reported data sets significantly deviate from each other, and the largest discrepancies were found at the lower end of the temperature interval examined (Mebelli et al. in Int. J. Thermophys. 42:116, 2021). Hence, in this work, the densities and viscosities of EG were measured in the temperature interval starting in the supercooled region at 248 and extending up to 313 K. Well-established experimental techniques were employed, that is, pycnometry and laminar flow viscometry, the relative precision of which were better than 0.5 and 0.5 %, respectively. The density was found to linearly depend on temperature in the temperature range studied; the cubic expansion coefficient was found to be γ = (5.20 + 3.99 × 10⁻³ T K^− 1) × 10⁻⁴ K⁻¹. When our experimental density data were applied to calculate the dynamic viscosity values using the correlation dependence published in the aforementioned review (Mebelli et al. in Int. J. Thermophys. 42:116, 2021), the discrepancy between our experimental data and the calculated values is less than 2 % above the freezing point; however, in the supercooled region, the discrepancy increases up to 4 % at 248 K. When the cooling rate is higher than 10 K min^− 1 and the sample mass is less than 5 mg, EG does not freeze; it undergoes glass formation (Tg =  − 121 °C) as revealed in our DSC experiments. The Arrhenius plot for viscosity data was found to be nonlinear; from the Angell plot, it was concluded that EG is a moderately fragile liquid with the fragility index = 70.

The potential of hybrid nanofluids to boost thermal efficiency of heat exchanger systems is the focus of this review study. The primary focus is on addressing the associated issues of nanoparticle clumping, system obstruction, and reduced efficacy of heat exchanger due to increased fluid thickness. Accordingly, this review intends to demonstrate the innovative practices (experimentally and theoretically) that helps improving the heat transfer and thermal performance of heat exchangers. In this regard, a critical analysis is conducted to appraise the experimental and numerical simulations, which introduce the impact of different nanoparticle concentrations and compositions on heat exchanger thermal performance. The findings of this review has shown that the hybrid nanofluid of CuO–Cu/water has the greatest thermal performance factor (1.065), following Al₂O₃–Cu/water (1.055), and Cu–TiO₂/water (1.039). Also, the utilization of turbulator heat exchangers has enabled improving the thermal performance by 126 % with a 6 % rise in volume fraction at the maximum Reynolds number. This study underlines the need for further research into novel nanomaterial combinations, fine-tuning of fluid characteristic, and comprehensive stability assessments to enhance the utilization of hybrid nanofluids in heat exchanger systems. Finally, discussions of limitations associated with such systems and proposed potential solutions will lead to a valuable contribution in the possible future development of cost-effective heat exchanger systems.

A method is described to measure the thermal expansion coefficient of fused quartz glass. The measurement principle is to monitor the change in resonance frequency of a Fabry–Perot cavity as its temperature changes; the Fabry–Perot cavity is made from fused quartz glass. The standard uncertainty in the measurement was less than 0.6 ((textrm{nm}{cdot } textrm{m}^{-1}){cdot }textrm{K}^{-1}), or 0.15 %. The limit on performance is arguably uncertainty in the reflection phase-shift temperature dependence, because neither thermooptic nor thermal expansion coefficients of thin-film coatings are reliably known. However, several other uncertainty contributors are at the same level of magnitude, and so any improvement in performance would entail significant effort. Furthermore, measurements of three different samples revealed that material inhomogeneity leads to differences in the effective thermal expansion coefficient of fused quartz; inhomogeneity in thermal expansion among samples is 24 times larger than the measurement uncertainty in a single sample.

The aim of the present work is to draw the attention to an unusual object of study, namely, heat transfer in short-term superheated hydrocarbons with micro-additives of moisture. We discuss the reasons for effect of the increase in the heat transfer coefficient to samples of saturated hydrocarbons having a moisture content of 15 mg⋅kg⁻¹ to 35 mg⋅kg⁻¹, which is unexpectedly strong (up to 10 %) with respect to pure hydrocarbons. This effect was discovered in experiments on pulse heating of a wire probe in a substance with characteristic times of 1 ms to 10 ms. We have developed a model based on the assumption of the role of dissolved water clusters in initiating fluid motion in the course of short-term superheating of the base fluid with respect to the liquid–vapor equilibrium temperature. Depending on the degree of superheating and pressure, the values predicted by the model for the increment of the heat transfer coefficient due to micro-additives of moisture are qualitatively consistent with the data obtained from the pulse experiments. The results of this study clarify the specific features of the superheated states of composite fluids, as well as contribute to developing methods for controlling the heat flux by micro-additives of a partially soluble component to the heat carrier.

The equilibrium solubility of sulfadiazine (SD, 3) in several {acetonitrile (MeCN) + ethanol (EtOH)} mixtures at nine temperatures from T/K = (278.15 K to 318.15) has been determined by following the shake flask method. SD solubility increased with temperature-arising as well as with the MeCN proportion-increasing in the mixtures. Thus, x₃ increased from 7.74 × 10⁻⁵ in neat EtOH to 6.20 × 10⁻⁴ in neat MeCN at T/K = 298.15. SD solubility was adequately correlated with a second-order multivariate equation as function of both mixtures composition and temperature. Moreover, two models including the Jouyban–Acree and Jouyban–Acree–van’t Hoff models were applied to mathematical SD solubility data modeling in solvent mixtures. The accuracy of each model is investigated by the mean relative deviations (MRD%) of the back-calculated solubility. A full predictive model was provided by training the Jouyban–Acree–van’t Hoff model with only seven experimental solubility data which provided excellent predictions with the MRD% of 3.7 %. All used models show a low MRD% values (< 4.0 %) for the calculated data indicating a good correlation of SD solubility data with the given mathematical models. By means of the van’t Hoff and Gibbs equations, the apparent thermodynamic quantities relative to SD dissolution and mixing processes, namely Gibbs energies, enthalpies, and entropies, were calculated and reported. Apparent dissolution quantities of SD were positive in all cases indicating endothermic and entropy-driven behaviors. A non-linear enthalpy–entropy relationship was observed for SD in the plot of SD dissolution enthalpy vs. Gibbs energy. Observed trend exhibits negative slope in the composition from neat EtOH to the mixture of 0.05 in mass fraction of MeCN indicating entropy-driving mechanism for this SD transfer process. Moreover, variant but positive slopes were found in the composition interval of 0.05 < w₁ < 1.00 indicating enthalpy-driving mechanism for these SD transfer processes. Furthermore, the preferential solvation of SD by MeCN or EtOH was analyzed by using the inverse Kirkwood–Buff integrals. Thus, SD is preferentially solvated by EtOH molecules in EtOH-rich mixtures but preferentially solvated by MeCN in MeCN-rich mixtures. In this way, this research expands the literature investigations about the solubility of SD in some non-aqueous cosolvent mixtures conformed by MeCN and other alcohols.

In physical foaming processes of thermoplastics, a liquid mixture consisting of a molten polymer with a dissolved blowing agent is extruded through a die or injected into a mold. The morphology of the foam matrix strongly depends on the mutual diffusion coefficient D₁₁ of the liquid polymer-blowing agent mixture. For a better understanding of the underlying physical mechanisms during the foaming process and the development of corresponding models, accurate knowledge of D₁₁ is needed. This work reports on the simultaneous measurement of D₁₁ and the thermal diffusivity a of liquid mixtures consisting of polystyrene melts with dissolved nitrogen (N₂) or carbon dioxide (CO₂) at mass fractions w_solute up to 0.003 or 0.02 and temperatures T between (433 and 533) K using dynamic light scattering (DLS). The determined D₁₁ range is between (1 and 4) × 10⁹ m²⋅s⁻¹ and are slightly larger for the mixtures containing N₂ at a given T and w_solute. D₁₁ could be determined with an average expanded relative uncertainty of 18%. Considering all investigated state points and the achieved experimental uncertainties, both D₁₁ and a are independent on the amount of dissolved gas, despite relatively large mole fractions of the dissolved blowing agents x_solute of 0.997 and 0.93.

Measurement of the thermophysical properties of liquid metals is a highly challenging task due to numerous problems encountered above the fusion point. Properties such as density and surface tension have been widely investigated, while few studies address thermal diffusivity. In this paper we describe an original methodology for estimating the thermal diffusivity of metals in the liquid state. The proposed experimental setup is based on the traditional flash method. Its design ensures that samples of liquid metal are self-contained, preventing contamination and allowing measurements at high temperature. Results for both solid and liquid iron and 304 stainless steel are presented and compared to data suggested by the literature for validation. Then, for the first time, thermal diffusivity measurement of liquid zirconium is performed giving results up to 2450 K. Giving the high sensitivity of the results to the thickness variation we propose a numerical approach to deal with this issue.

A single-temperature-based dew-point generator (DPG), capable of producing air with dew point temperatures ranging from 25 °C to 60 °C, has been developed at SNSU-BSN Indonesia. The air flows through the saturator in a single pass and is controlled by a flow meter to have a maximum flow rate of 1 lpm. The air saturation process is carried out using a bubble aerator capable of producing bubbles ranging in size from below 0.5 mm to several mm in diameter. A heat sink, placed inside the saturator, is used to prevent water splashes from entering the gas outlet and to stabilize the dew point temperature. The impact of the saturator load is also modeled and simulated. The saturator is then placed into a thermostatic bath where heating of the gas outlet tube is performed starting from 5 cm below the water surface to prevent condensation due to environmental temperature influences. This developed saturator system is simple and low cost. The performance test includes a comparison with a high-precision dew-point hygrometer (DPH) and an evaluation of saturator efficiency. The accuracy of the generated dew point temperature is determined by referencing the reference value from the APMP.T-K8 comparison results. The test results are presented in graphical and tabular format along with an example uncertainty budget.