1,3-Propanediol (1,3PD), 2-methyl-1,3-propanediol (2M1,3PD), 1,2-butanediol (1,2BD), 1,3-butanediol (1,3BD), and 1,4-butanediol (1,4BD), and their aqueous solutions, are commonly used as heat transfer fluids. The thermal conductivity (lambda) of these substances is a critical physical property. However, limited data are available in the literature, particularly for their aqueous solutions. In this study, lambda of the aforementioned aqueous solutions was measured using a transient hot-wire apparatus over the temperature (T) range of 293 to 373 K at ambient pressure close to 0.1 MPa, with an estimated expanded uncertainty of 1.7% (k = 2). The reliability of the experimental setup was validated by using pure water prior to measurements. Empirical correlations were developed to represent lambda of both the pure alcohols and their aqueous solutions. For the pure alcohols, the deviation between experimental and correlated values was within 0.5%, while for the aqueous solutions, the deviation was within 3.9%. A brief analysis of structure-property relationships was conducted, suggesting that the nonideality observed in aqueous solutions may be attributed to changes in hydrogen bonding and dipole-dipole interactions caused by structural rearrangement in the solution. The results presented in this work provide valuable data for industrial applications and thermal design involving these aqueous solutions.

Trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) and cis-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)) are considered as promising candidates for high-temperature heat pump applications. Nonetheless, comprehensive reference correlations capable of accurately predicting the viscosity (eta) of these fluids across broad temperature (T) and pressure (p) ranges have yet to be established. This study compiled existing experimental viscosity data from the literature and developed new correlations expressed as functions of T and density (rho). The resulting reference correlations are valid for temperatures from 240 K to 480 K and pressures up to 40 MPa. A comparative analysis was performed between the collected experimental eta and those calculated from the proposed correlations. For R1233zd(E), the maximum deviations (MD) were-8.1% for the liquid phase and-5.5% for the gas phase. Corresponding MD values for R1336mzz(Z) were 4.8% in the liquid phase and 7.5% in the vapor phase. Furthermore, the expanded uncertainty (with a coverage factor k = 2) associated with viscosity evaluation from the reference correlations was assessed, considering the range encompassing 95% of the deviations. For R1233zd (E), the estimated expanded uncertainty is 4.1% in the liquid phase below 410 K, increasing to 6.5% in the liquid phase up to 433 K, and is 4.0% in the vapor phase. For R1336mzz(Z), the estimated expanded uncertainties are 2.8% for the liquid phase and 7.8% for the vapor phase.

Under the Kigali Amendment, which promotes the phase-down of refrigerants with high global warming potential (GWP), the low-GWP azeotropic mixture R516A has been considered a promising alternative to R134a. However, experimental data on its fundamental thermophysical properties remain limited. In this work, the liquid density and viscosity of R516A were systematically measured using a vibrating-wire viscometer-densimeter over the temperature range of 243.15∼363.15 K and at pressures up to 12 MPa. Treating R516A as a pseudo-pure fluid, the Tait equation and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state were used to correlate and predict the liquid density, while the Vogel–Fulcher–Tammann (VFT) equation, extended hard-sphere (EHS) model, residual entropy scaling (RES) model, and artificial neural network (ANN) model were evaluated for viscosity prediction. The results show that the Tait equation provides an accurate representation of the liquid density, with an average absolute relative deviation (AARD) of 0.09%. For viscosity, the EHS model gives the best performance, with an AARD of 0.71%, followed by the RES model and VFT equation. In contrast, the ANN model exhibits a clear systematic deviation under the current dataset and model settings. The high-accuracy experimental data enrich the thermophysical property database of R516A and provide reliable input for property model development and the optimization of R516A-based refrigeration and heat pump systems.

The near-azeotropic mixture refrigerant R454B, composed of 68.9 % difluoromethane (R32) and 31.1 % 2,3,3,3Tetrafluoropropene (R1234yf) by mass, has been promoted as an alternative to R410A and has gained wide applications. Thermophysical properties such as density (rho) and viscosity (eta) play crucial roles in heat and mass transfer processes. In this study, a vibrating-wire viscometer-densimeter (VWVD) was used to measure the rho and eta of R32, R1234yf, and R454B within a temperature range of 254 to 362 K and pressures up to 12.3 MPa. The obtained rho and eta values for R32 and R1234yf were compared with the reference equations implemented in REFPROP 10.0, with deviations mostly within the combined uncertainty. A Tait equation was applied to represent the rho of R454B, with deviations mostly within 0.2%. A Vogel-Fulcher-Tammann (VFT) equation was used to correlate the eta of R454B, where discrepancies were mostly within 3%. To extend the temperature, pressure, and composition range of the R32 + R1234yf mixtures, an extended hard sphere (EHS) model was developed using the experimental eta data from this study and literature. Several mixing rules for the model were analyzed, but no significant improvement was found with an additional parameter. The performance of the EHS model without a binary parameter was compared with the extended corresponding states (ECS) model. The results showed that the EHS model had advantages in the high-density region. The EHS model developed in this study can reproduce the eta of the R32 + R1234yf mixture mostly within 6% in the high-density region.

In this work, an integrated system for hydrogen energy utilization system (HUS) in oil and gas fields was constructed focusing on two scenarios: hydrogen fuel cell bus and industrial combustion. The energy consumption, environmental, economic, and energy efficiency were assessed for the various HUS technological pathways associated with produced water treatment, hydrogen production, transport and storage, refueling, and utilization. The entropy weight-TOPSIS method was utilized to assess the optimal pathway. The results indicate that the pathway of alkaline water electrolysis for hydrogen production and pipeline transportation to gas-hydrogen refueling stations for hydrogen fuel cell bus shows excellent comprehensive indicators, which has an energy consumption of 197.15 MJ/kgH2, the levelized cost of hydrogen (LCOH) of 6.70 USD/kgH2, a system energy efficiency of 30.43%. For industrial combustion, the best pathway is alkaline water electrolysis for hydrogen production and pure H2 pipeline transportation. Sensitivity analyses were conducted to explore the impact of different factors on LCOH. As the electricity price decreases to 0.014 USD/kWh, LCOH will reduce by 2.50 USD/kgH2. The reduction in electricity prices will further increase the feasibility of hydrogen energy in the future.

Carbon dioxide (CO2), as a natural working fluid, is blended with hydrofluorocarbons (HFCs) or hydrofluoroolefins (HFOs) that exhibit favorable thermodynamic properties. By modifying the mixture composition, the performance of the refrigeration system can be optimized in terms of efficiency and operational conditions. However, comprehensively evaluating the thermodynamic properties of CO2-based mixtures through experimental measurements alone remains challenging due to the complexity, expense, and time involved. This highlights the critical necessity for advanced computational methods to enhance and extend experimental research. In this study, molecular dynamics (MD) simulations were employed to comprehensively investigate the vapor–liquid phase behaviors and surface tension properties of CO2, R32, and R134a in their pure, binary, and ternary components, respectively. The MD results show good agreement with our previous Gibbs Ensemble Monte Carlo (GEMC) simulations and the experiment-derived correlations from REFPROP program, demonstrating the precision and dependability of the employed force field and molecular methodology. These findings validate that molecular simulation, when coupled with a well-parameterized potential energy function, can effectively characterize essential thermophysical properties and fill data gaps where experimental measurements are limited. The methodology provides a solid foundation for subsequent research on refrigerant mixture behavior and offers valuable insights for the optimization and design of thermal cycle systems.

In this work, ZnO nanoparticle was surface modified with the PFPE-acid as ligand. The modified ZnO particle size was about 30 nm measured by SEM. The modified ZnO/HFE-7100 nano-coolants with mass fractions of 0.10 % 0.40 % were prepared and characterized, and their dispersion stabilities were evaluated by visual sedimentation and UV spectrophotometer. Then the thermal conductivities of these nano-coolants were measured using a visualized transient hot-wire system. Results show that the thermal conductivity of the modified ZnO/HFE-7100 nano-coolants increased with the increasing mass fraction of nanoparticles and temperature, and 4.94 %-16.24 % enhancement were found compared to the base fluid. Based on the experimental data, a thermal conductivity model of nano-coolant was developed, and the deviation of the calculated thermal conductivity from the experimental value was less than +/- 1.10 %.

Hydrogen (H2) solubility in liquid organic hydrogen carriers (LOHCs) is crucial for their widespread applications. This work investigates the solubility of H2 x in two promising LOHCs: Acetophenone (APO) and 1-Methylnaphthalene (1-MN). Measurements were conducted using an isochoric saturation method within a temperature range of 293 to 363 K and pressures up to 5.8 MPa. The liquid densities rho of APO and 1-MN, essential for characterizing H2 solubility, were measured using a vibrating tube densitometer (DMA5000 M) at approximately 0.1 MPa. The experimental rho for APO and 1-MN were compared with literature data and good agreement can be found. The Krichevsky-Kasarnovsky(K-K) equation was employed to correlate H2 solubility x in APO and 1-MN, with deviations of mostly within 6 % and 10 %, respectively. Following, the behavior of H2 solubility x concerning pressure along isothermal lines was analyzed. Finally, the thermodynamic parameter of dissolution of the two binary systems were studied. The enthalpy of dissolution is positive for all the systems, while the entropy of dissolution is negative. Under the same temperature, the Gibbs free energy of dissolution for the H2 + APO system is smaller than that of the H2 + 1-MN system.

In this work, n-hexane, cyclohexane and 2-methylpentane were selected to represent linear-alkane, cycloalkane and branched-alkane, respectively. Based on the dynamic light method (DLS), the viscosity, interfacial tension and diffusion coefficient of n-hexane/CO 2 , cyclohexane/CO2 2 and 2-methylpentane/CO2 2 systems under saturation condition were measured in order to explore the change trend of thermophysical properties of the systems with the same carbon atom number but different molecular structures. The experiments were conducted at the temperatures of 303, 343 and 383 K and at pressures up to 5.64 MPa. The expanded uncertainties(k k = 2)of dynamic viscosity, interfacial tension and diffusion coefficient were 3 %, 3 % and 4.4 % respectively. The experimental results show that n-hexane and 2-methylpentane with similar molecular structure have more similar value of the properties. The effects of different alkane structures on system viscosity, interfacial tension, and diffusion coefficient were explained at the molecular level through radial distribution function, interface thickness, and CO2 2 coordination number. At 303.15 K and 4 MPa, the peak radial distribution function of CO2/ 2 / cyclohexane is 1.845, which is greater than that of CO2/n-hexane 2 /n-hexane and CO2/2-methylpentane 2 /2-methylpentane molecules. It has been proven that the arrangement of CO2/cyclohexane 2 /cyclohexane is more orderly, resulting in higher viscosity and lower diffusion coefficient of the system. The interface thickness of CO2/cyclohexane 2 /cyclohexane is 6.13 nm, which is smaller than CO2/n-hexane 2 / n-hexane (7.53 nm) and CO2/2-methylpentane 2 /2-methylpentane (6.3 nm). The smaller the interface thickness, the more compact the structure, the stronger the intermolecular forces, and the greater the interfacial tension. At 303.15 K and 2 MPa, the number of CO2 2 coordination sites within 1 nm around liquid phase alkanes is 3.96, which is smaller than 4.78 for cyclohexane and 6.62 for 2-methylpentane. Prove that the coordination number is directly proportional to the diffusion coefficient and inversely proportional to viscosity and interfacial tension.

The thermophysical properties of systems with alkanes with dissolved carbon dioxide (CO2) are of importance in the aspects of carbon capture and storage (CCS), enhanced oil recovery (EOR), Fischer-Tropsch (FT) synthesis, et al. This work continues for our previous studies about the thermophysical properties of several binary systems with alkane and CO2. In this work, the liquid viscosity, interfacial tension, thermal and mutual diffusivity of normal eicosane n-C20H42 with dissolved CO2 were measured with dynamic light scattering (DLS) method from (323 to 473) K and (0.1 to 5.6) MPa. The system's liquid viscosity and interfacial tension were analyzed as a function of pressure under each isotherm line. The polynomial-based empirical correlations were developed for liquid viscosity and interfacial tension with pressure and temperature. The maximum deviations were 4.4 % for liquid viscosity and 1.1 mN center dot m  1 for interfacial tension. The experimental interfacial tension from the literature was compared with this work, and the deviations were mostly with 0.50 mN center dot m  1. The mutual diffusivity of the system was nearly a constant along the investigated composition range in this work. The mass diffusion coefficients from the literature agree with this work. The results from this work were expected to provide reliable and accurate fundamental thermophysical properties of liquid with dissolved gas systems in engineering and chemical processes.

The benzyltoluene (BT)-based liquid organic hydrogen carrier (LOHC) system currently considered for largescale applications represents a mixture of regioisomers. To characterize this complex system, a comprehensive experimental database for various thermophysical properties of synthesized BT isomers and their mixtures without and with the presence of hydrogen (H2) close to vapor-liquid equilibrium is established using optical and conventional techniques at process-relevant temperatures and pressures up to 573 K and 6 MPa. The surface tension varies by less than 4% among the dehydrogenated (H0-BT) or hydrogenated (H12-BT) isomers. The density and viscosity of mixtures of H0-BT or H12-BT isomers can be described by simple mixing rules with average absolute relative deviations of 0.022% and 0.38%. With increasing H2 pressure, the viscosity remains nearly constant, while the interfacial tension decreases by up to 5%. The thermal and mutual diffusivity of H12ortho-BT containing dissolved H2 at 6 MPa decrease and increase with increasing temperature.

In this study, the solubilities of hydrogen (H2), nitrogen (N2), and carbon dioxide (CO2) in the eutectic mixture of diphenylmethane (1) and biphenyl (2) with mass fraction w1 = 0.64947 were determined by the isochoric saturation method at pressures ranging from 0.918 MPa to 6.208 MPa, and temperatures ranging from 293 K to 363 K. The results indicate that the solubilities of the gases in the eutectic mixture follow the order CO2 > H2 ≈ N2. The gas solubility data were correlated using the Krichevsky-Kasarnovsky (K-K) equation. The absolute average relative deviations (AADs) of the experimental values from the calculated data for the H2 + eutectic mixture, N2 + eutectic mixture, and CO2 + eutectic mixture systems were 1.98

One essential aspect of the studies on the refrigeration and heat pump technology is to search for new alternative working fluids. Meanwhile, the azeotropic mixtures of hydrofluorocarbons (HFCs)/hydrofluoroolefins (HFOs) have attracted researchers not only in fundamentals research field but also in the industry fields due to its good performance and applicability. Therefore, to promote application research, this study is focused on the characteristics of viscosity for azeotrope R515B, which is widely recognized and studied from the thermodynamic aspect. Hence, the high-pressure density and viscosity in liquid phase of R515B were measured with a vibrating-wire viscosimeter within the temperature range in 253 K to 363 K when pressure changes from 1 MPa to 12 MPa. The combined expended uncertainties with a confidence level of 0.95 (k=2) of density and viscosity are 0.2% and 2%, respectively. In addition, a modified viscosity model is proposed with combining the parameterization method of thermodynamic equation of state (EoS) in previous work and the modified entropy variable as well as reduced viscosity reference term of residual entropy scaling (RES) theory. Furthermore, the systematical comparison results among this model and three benchmark viscosity models available illustrate that the RES model proposed in this research is robust and precise in a wide range of operation condition.

Hydrogen (H2), nitrogen (N2) and carbon dioxide (CO2) solubilities were measured at the temperature (313 to 363) K and the pressure (0.809 to 6.194) MPa. The reliability of the experimental system was verified by measuring the solubilities of N2 in dodecane and CO2 in decane at 344 K. The experimental data were fitted by empirical correlation x=(aT2+bT+c)(dp2+ep+f), and the relative deviations between the experimental value and the literature value for the solubilities at given pressure and temperature were less than ±5 %. Under the same temperature and pressure conditions, the solubilities of the three gases in DPM is CO2 > N2 ≈ H2. Krichevsky- Kasarnovsky (K-K) equation was used to fit the experimental data. The absolute average relative deviation (AAD) between the experimental data of H2+DPM, N2+DPM and CO2+DPM systems and the calculated values of K-K equation are 1.21 %, 1.86 % and 0.88 %, respectively. In addition, the Henry constants of three gases dissolved in DPM were calculated, and the solution enthalpy, solution entropy, solution Gibbs free energy and solution specific heat capacity were calculated. H2 and N2 solubilities showed to be endothermic, while CO2 showed the opposite trend.

Fluorene (H0-F) and perhydrofluorene (H12-F) represent process-related byproducts formed by a dehydrocyclization step in the liquid organic hydrogen carrier (LOHC) system based on diphenylmethane (H0-DPM) and dicyclohexylmethane (H12-DPM). The influence of these byproducts on the liquid viscosity, surface tension, and liquid density of the DPM-based system was experimentally determined by studying three dehydrogenated binary mixtures with H0-F mole fractions of 0.05, 0.10, and 0.20 as well as one hydrogenated binary mixture with an H12-F mole fraction of 0.10 close to 0.1 MPa from (283-573) K. The densities increase with increasing share of H0-F or H12-F by around 1% per added byproduct mole fraction of 0.1. For the surface tension, an increase relative to the values of H0-DPM or H12-DPM by up to 6% is found. The addition of H0-F to H0-DPM or H12-F to H12-DPM yields a relative increase in viscosity by up to 9% at the lowest temperature studied.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

HYPOTHESIS:The applicability of the dynamic light scattering method for the determination of particle diffusivity under confinement without applying refractive index matching was not adequately explored so far. The confinement effect on particle diffusion in a porous material which is relevant for particle chromatography has also not yet been fully characterized. EXPERIMENTS:Dynamic light scattering experiments were performed for unimodal dispersions of 11-mercaptoundecanoic acid-capped gold nanoparticles. Diffusion coefficients of gold nanoparticles in porous silica monoliths were determined without limiting refractive index matching fluids. Comparative experiments were also performed with the same nanoparticles and porous silica monolith but applying refractive index matching. FINDINGS:Two distinct diffusivities could be determined inside the porous silica monolith, both smaller than that in free media, showing a slowing-down of the diffusion processes of nanoparticles under confinement. While the larger diffusivity can be related to the slightly slowed-down diffusion of particles in the bulk of the pores and in the necks connecting individual pores, the smaller diffusivity might be related to the diffusion of particles near the pore walls. It shows that the dynamic light scattering method with a heterodyne detection scheme can be used as a reliable and competitive tool for determining particle diffusion under confinement.

This work proposes reference viscosity corrections that combine the Peng-Robinson (PR), Volume-Translated PR (VTPR), and Cubic-Plus-Association (CPA) Equation of State (EoS) with the friction theory (FT) model for carbon dioxide (CO2), hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), and their binary and ternary mixtures. The viscosity value is divided into the diluent gas term and residual friction term consisting of van der Waals repulsion and attraction forces. The established FT model employs the temperature-dependent coefficients connecting the friction forces to the Amontons-Coulomb equation. Additionally, correlations between these FT coefficients and existing experimental viscosity data were established, and the binary interaction pa-rameters (BIPs) employed in deriving vdW mixing rules were also computed for the binary blends consisting of HFOs. The PR + FT, VTPR + FT, and CPA + FT models can reasonably reproduce the viscosity for unary compounds and match the experiment viscosities with the measurement uncertainties. However, PR and CPA EoS will substantially deviate from the reference experimental densities at high temperatures and pressures. At the same time, the VTPR + VdW + FT model has a good predictive ability by comparing the experimental viscosity data of the binary and ternary potential refrigerant mixtures. These findings are expected to provide a satisfactory and appropriate theory for investigating the properties of heat and mass transfer in refrigeration systems.

In the present work, the liquid viscosity and surface tension of tris(2-ethylhexyl) trimellitate (TOTM) was determined close to 0.1 MPa over a temperature range between 273 and 523 K by surface light scattering (SLS). Such investigations were stimulated by the fact that TOTM is suggested as a potential viscosity standard of moderately high viscosity for temperatures up to 473 K and pressures up to 200 MPa. Based on the SLS experiments at macroscopic thermodynamic equilibrium, a simultaneous determination of liquid viscosity from 273 to 523 K and surface tension from 398 to 523 K with relative expanded uncertainties typically below 0.03 (coverage factor k = 2) was possible. To evaluate the results from SLS and to check possible surface orientation effects found in our previous SLS studies on liquid organic hydrogen carriers, conventional methods in the form of the pendant-drop method and capillary viscometry were used to determine the surface tension and viscosity from 273 to 573 K and from 293 to 353 K, respectively. For evaluating all experimental methods applied, the liquid density was obtained with the help of a vibrating-tube densimeter between 283 and 473 K. From a long-time SLS study at 573 K and subsequent density and nuclear magnetic resonance measurements, a clear sample degradation of TOTM was observed, which may hinder its application as an industrial viscosity standard above 523 K. For both the surface tension and the viscosity which covers a range between about 1500 and 0.9 mPa s at temperatures between 273 and 523 K, agreement between the results from SLS and the conventional methods within combined uncertainties was found, which is also valid by comparison with the literature. In summary, the experimental results from this work could not only contribute to an improved data situation for viscosity and surface tension of TOTM over a broad temperature range but also reveal that TOTM does not show pronounced molecular orientation effects at the vapor-liquid interface which would influence the dynamics of the surface fluctuations probed by SLS.

界面张力是CO2驱强化采油中的重要参数,影响着原油在岩层的运输,是区分混相驱与非混相驱的关键参数.本文采用分子动力学模拟方法,对CO2与正己烷、环己烷及2-甲基戊烷组成的二元体系的界面张力进行了研究,计算了 303.15 K、343.15 K,1～5MPa条件下,混合体系的界面张力,分析了不同分子结构对界面张力的影响.结果表明:模拟计算出的界面张力值与实验值吻合较好,在相同条件下,σCO2.环己烷＞σCO2-正己烷＞σCO2-2-甲基戊烷.二元体系两相界面厚度越小、液相CO2配位数越大,则界面张力越大.