Thermophysical Property Data Research Articles

Characterization of the molten salt FMgNaK through ab initio molecular dynamics and experimental density measurements

The selection of a salt species for use in a molten salt reactor MSR is a key part of any MSR design. However, many salts have sparse or no thermophysical property data sets, especially those with higher melting points . One such salt is the eutectic mixture of (NaF)0.345(KF)0.59(MgF 2 )0.065, or FMgNaK, and is explored here through ab initio molecular dynamics (AIMD) simulation (1023-1273K) as well as experimental measurement of the liquid density using the Archimedean method (973-1223K). Predicted densities from AIMD are similar to experimentally-measured densities, though with more noise, suggesting that the small scale necessitated by AIMD simulations may be problematic for simulating FMgNaK in particular. The coefficient of thermal expansion is predicted from simulation, and salt structure is characterized. Mg-F-Mg chaining is observed in the salt network, though the low concentration of Mg inhibits chaining on the scale that is observed in (LiF) 0.67 (BeF 2 ) 0.33 , or FLiBe.

On the role of orifice wetting for Al and Al22.5 wt%Cu with Al2O3 in the discharge crucible method

The demand to develop Materials Genomics and Integrated Materials Computation requires the availability of high temperature liquid metals property data. As computing power and algorithms are constantly being improved, the accuracy of thermophysical property data has emerged as one of the limiting factors. Knowledge of these properties for materials such as Al and Al-alloys is a critical factor in numerical simulations and modelling of a wide array of industrial processes. This work reports on the measurement of viscosity, surface tension and density of liquid Al and Al-22.5wt.%Cu using the discharge crucible method. While viscosity and surface tension proved to be in good agreement with other published experimental data, as well as various theoretical and empirical models, density was found to be significantly lower than expected or previously measured. With further analysis, it was determined that wetting of Al or Al-Cu at the orifice of the Al2O3 crucible had a significant effect on flow rate; ergo, violating some of the key assumptions in the model used to calculate the thermophysical properties. Dimensionless number analysis identified that wetting had an immediate effect on the flow rate due to the formation of a meniscus, with the effect becoming more dominant as Capillary number decreased or drain time increased. In looking at the sensitivity of the model, it was determined that density had the largest influence on flow rate, explaining the unique link between the role of orifice wetting and density measurement accuracy (as opposed to viscosity or surface tension). Future research will aim to extend the discharge crucible model and method to account for wetting at the orifice, particularly at high temperatures.

Design of Composites by Infiltration Process: A Case Study of Liquid Ir-Si Alloy/SiC Systems.

The design of processing routes involving the presence of the liquid phase is mainly associated with the knowledge of its surface and transport properties. Despite this need, due to experimental difficulties related to high temperature measurements of metallic melts, for many alloy systems neither thermodynamic nor thermophysical properties data are available. A good example of a system lacking these datasets is the Ir-Si system, although over the last fifty years, the structures and properties of its solid phases have been widely investigated. To compensate the missing data, the Gibbs free energy of mixing of the Ir-Si liquid phase was calculated combining the model predicted values for the enthalpy and entropy of mixing using Miedema’s model and the free volume theory, respectively. Subsequently, in the framework of statistical mechanics and thermodynamics, the surface properties were calculated using the quasi-chemical approximation (QCA) for the regular solution, while to obtain the viscosity, the Moelwyn-Hughes (MH) and Terzieff models were applied. Subsequently, the predicted values of the abovementioned thermophysical properties were used to model the non-reactive infiltration isotherm of Ir-Si (eutectic)/SiC system.

Numerical investigation of heat transport in Alumina–Silica hybrid nanofluid flow with modeling and simulation

The current numerical study investigates the thermal performance of four mono-component (i.e., blade-shaped Al2O3, brick-shaped Al2O3, cylinder-shaped Al2O3 or platelet-shaped Al2O3 nanoparticles in 50:50 water–ethylene glycol (EG) base fluid) and four bi-component nanofluids (i.e., blade-shaped Al2O3+SiO2/EG–water, cylinder-shaped Al2O3+SiO2/EG–water, brick-shaped Al2O3+SiO2/EG–water, and platelet-shaped Al2O3+SiO2/EG–water hybrid nanofluids) with the help of mathematical modeling. The non-Newtonian nature of these nanofluids is modeled using second grade viscoelastic fluid model accompanied by the energy equation. The highly non-linear coupled differential equations are solved by shooting method accompanied by 4th order Runge–Kutta method in MATLAB software. The numerical simulations are performed by procuring the data for thermophysical properties from the experimental studies. The effective thermal conductivity and viscosity of the four distinct alumina nanofluids are calculated by the models obtained from the experimental studies. The numerical results reveal that the nanofluid with platelet-shaped Al2O3 nanoparticles is the best heat transporter among the four alumina nanofluids The addition of SiO 2 nanoparticles further accelerates the rate of heat transfer in all four alumina nanofluids. The numerical results that illustrate the influence of nanoparticle volume fraction and thermofluidic parameters on the heat transport phenomenon are also discussed. The MATLAB code developed for the numerical solution is validated against the substantial published literature.

Liquid metals: Thermophysical properties of alloys from the Ga-Sn-Zn system

Liquid metals are a group of functional materials of growing importance in the recent years. In this work, the density, viscosity and surface tension of liquid Ga-Sn-Zn alloys for compositions with the Sn/Zn ratio of 3/1, 1/1 and 1/3 with Ga additions have been determined by the discharge crucible method. An attempt was done to describe the abovementioned properties as a function of temperature and composition. The new thermophysical property data were compared to the values predicted by models. The Moelwyn-Hughes, Kozlov-Romanov-Petrov, Sato, Schick and Gasior models for viscosity, and for density, the Brillo and Egry and ideal solution models were applied. The surface tension of binary liquid alloys was analysed in the framework of the Butler and Quasi Chemical Approximation for regular solution (QCA), while to describe the surface tension of ternary melts, the models of Butler, Toop, Kohler and Muggianu were used.

Effect of Multi-Walled Carbon Nanotubes-Based Nanofluids on Marine Gas Turbine Intercooler Performance.

Coolants play a major role in the performance of heat exchanging systems. In a marine gas turbine engine, an intercooler is used to reduce the compressed gas temperature between the compressor stages. The thermophysical properties of the coolant running within the intercooler directly influence the level of enhancement in the performance of the unit. Therefore, employing working fluids of exceptional thermal properties is beneficial for improving performance in such applications, compared to conventional fluids. This paper investigates the effect of utilizing nanofluids for enhancing the performance of a marine gas turbine intercooler. Multi-walled carbon nanotubes (MWCNTs)-water with nanofluids at 0.01–0.10 vol % concentration were produced using a two-step controlled-temperature approach ranging from 10 °C to 50 °C. Next, the thermophysical properties of the as-prepared suspensions, such as density, thermal conductivity, specific heat capacity, and viscosity, were characterized. The intercooler performance was then determined by employing the measured data of the MWCNTs-based nanofluids thermophysical properties in theoretical formulae. This includes determining the intercooler effectiveness, heat transfer rate, gas outlet temperature, coolant outlet temperature, and pumping power. Finally, a comparison between a copper-based nanofluid from the literature with the as-prepared MWCNTs-based nanofluid was performed to determine the influence of each of these suspensions on the intercooler performance.

What the Thermophysical Property Community Should Know about Temperature Scales.

Temperature scales have evolved through many decades in order to more accurately represent the thermodynamic temperature. This creates challenges for those who study thermophysical properties, because the temperatures given for literature data may not correspond to the latest international scale. The resulting differences are small, but not necessarily negligible, especially for reference-quality work. Here, we describe the temperature scales that might be encountered in the literature and give guidance for converting them to the International Temperature Scale of 1990 (ITS-90). We pay special attention to the liquid-helium scales used for cryogenic work, where a potentially confusing number of different scales has been used. Advice is given for avoiding common mistakes in dealing with temperature scales in the context of thermophysical property data, including the responsibility of experimentalists to fully document their reported temperatures and the responsibility of modelers to document their handling of any temperature-scale issues.

Sensitivity of the Non-Equilibrium Approach for Mixture Condensation to Heat and Mass Transfer Correlations and Thermophysical Properties

Abstract The prediction of mixture condensation is still complex due to the coupled heat and mass transfer and insufficient data of thermophysical mixture properties. This article analyzes the impact of various heat and mass transfer correlations on the non-equilibrium approach for mixture condensation in a vertical plain tube. Furthermore, the influence of thermophysical properties from different databases is investigated. The results are shown for ethanol-water, but allow conclusions to other fluid mixtures. They indicate that the liquid heat transfer coefficient in the non-equilibrium approach dominates the qualitative behavior of the condensation process, but the vapor mass transfer coefficient can only decrease or increase the quantitative level of the effective heat transfer with minor impact. More importantly, the logarithm in the vapor mass transfer term is central for the prediction of the condensation heat transfer. As this logarithm contains vapor-liquid equilibrium (VLE) data, it proves that there is a strong connection between VLE and overall prediction of mixture condensation. A demonstration of available data for thermophysical mixture properties of ethanol-water shows significant deviations, which affect the calculations as well. Besides, data from our own experiments are presented for mixture viscosity of ethanol-water. It is recommended to focus not only on improved heat and mass transfer correlations but also on thermophysical properties and VLE data for a precise prediction of mixture condensation.

Review and characterisation of high-temperature phase change material candidates between 500 C and 700°C

Latent heat thermal energy storage, by using phase change materials (PCMs), is considered as a promising technology that can be integrated into concentrated solar power (CSP) applications to mitigate the load and electricity supply. Multiple PCMs connected in series has attracted considerable research attention as this configuration has the potential to improve the thermal performance compared to single PCM storage. However, this technology has not yet been deployed in commercial CSP plants. One of the major restrictions is the lack of reliable thermophysical property data for high temperature PCMs. This study gives a broad review of the experimentally verified PCMs with melting temperatures from approximately 500 °C–700 °C, applicable to CSP systems. A further twelve PCM candidates, containing low-cost sodium and/or potassium salts, were identified in this study and their thermophysical properties were experimentally evaluated. It was found that nine of the new candidates can be used as PCMs.

Transient testing of uranium silicide fuel in zircaloy and silicon carbide cladding

Using the newly restarted Transient Reactor Test (TREAT) facility at Idaho National Laboratories, fresh (unirradiated) U3Si2 fuel pellets were tested under reactivity-initiated accident conditions in dry helium capsules. These tests were performed with total energy depositions sufficient to induce melting of the U3Si2 fuel pellets based on available thermophysical property data. The instrumented experiments utilized in-pile thermocouples and infrared pyrometers to measure the cladding temperature during the transient, which are in reasonable agreement with predicted peak cladding temperatures using a simple BISON fuel performance model. This same model is then used to predict expected cladding stresses during the transients in areas where pellet cladding interaction is expected. It was shown that for transient energy depositions up to 528 J/g rod like geometry of the test articles was maintained. While it is acknowledged that more confirmatory testing is required in more prototypic environments, these first of their kind experiments have demonstrated that unirradiated U3Si2 fuel and unirradiated SiC-SiC claddings can likely retain a “rod like” geometry for transient energy depositions up to 528 J/g.

Study of the thermophysical properties for aqueous alkanediols binary mixtures

The thermophysical properties data as densities, speeds of sound, and refractive indices for aqueous binary mixtures of 1,2-hexanediol and 1,5-pentanediol, have been measured at several temperatures in the range of (298.15–318.15) K, atmospheric pressure, and in the whole domain (0 to 1) of diol molar fractions.From the obtained experimental values, the related excess and deviation quantities, namely the excess molar volumes, the partial/apparent molar volumes, the isentropic compressibilities, the excess isentropic compressibilities and the deviation in refractive indices were calculated.The excess thermodynamic properties were correlated with the Redlich-Kister polynomial equation. The experimental excess molar volumes values have been also used to test the applicability of the Prigogine-Flory-Patterson theory and the results were analyzed in terms of molecular interactions between the components of the mixture.Discussions concerning the experimental and calculated results in relation to the molecular interactions and structural effects between components of mixtures are presented.In the dilute range, at (0 to 0.3) diol mole fractions, the characteristic behavior of the excess and partial molar quantities was related to the structural changes in the mixtures as observed by neutron scattering.

Experimental evaluation of the thermal conductivity for additive manufactured materials. New test facility concept and preliminary tests

Items for heat transfer made by metal foams or additive manufactured structures allow to create special components for several applications (i.e. fast response PCM, complex and light HEXs working at high temperatures for the aerospace sector). For their design thermo-physical properties data are required, such as thermal conductivity. To accurately measure this parameter with conventional procedures for metallic items (e.g. flash methods), the specific heat and density should be measured each time depending on the actual composition of the porous media (estimation is not yet reliable and porosity not known). The scope of this paper is to validate a test facility and the relative method for the data reduction to proof the possibility to measure directly the thermal conductivity with samples of small size. The experiments, carried-out with square samples (30×30 mm2), allow to measure a range of thermal conductivity between 5 and 50 W/m K. The main aspect of the experimental method is the calibration of the heat losses towards the environment by means of a reverse technique. The assessment of the results against samples of known materials was good.

Good Reporting Practice for Thermophysical and Thermochemical Property Measurements (IUPAC Technical Report).

Scientific projects frequently involve measurements of thermophysical, thermochemical, and other related properties of chemical compounds and materials. These measured property data have significant potential value for the scientific community, but incomplete and inaccurate reporting often hampers their utilization. The present IUPAC Technical Report summarizes the needs of chemical engineers and researchers as consumers of these data and shows how publishing practices can improve information transfer. In the Report, general principles of Good Reporting Practice are developed together with examples illustrating typical cases of reporting issues. Adoption of these principles will improve the quality, reproducibility, and usefulness of experimental data, bring a better level of consistency to results, and increase the efficiency and impact of research. Closely related to Good Reporting Practice, basic elements of Good Research Practice are also introduced with a goal to reduce the number of ambiguities and unresolved problems within the thermophysical property data domain.

Experimental Data of Thermophysical Properties of Mixtures of Oxygenated Additives + Hydrocarbon in Fuels and Biofuels: Application of Perturbed Chain-Statistical Associating Fluid and Peng–Robinson Equations of State

Experimental data of excess enthalpy, (HE), density, (ρ), speed of sound, (u), and the refractive index, (nD), are reported in this work for ternary and binary mixtures composed of diethylene glyco...

Investigating Thermophysical Properties Under Microgravity: A Review

The cover page shows micrographs of the titanium Ti64 alloy, solidified in space, in the electromagnetic levitator ISS-EML on board the international space station ISS and solidified on ground. The thermophysical property data measured in the absence of gravity on board the international space station serves as benchmark data for processes simulation models of casting and additive manufacturing. Micrographs are taken after heat-tinting. Courtesy of Prof. David Jarvis, HIPtec AS, Oslo, Norway. For more details, refer to the article, number 2001223, by Markus Mohr and co-worker.

Liquid thermal conductivity of three biodiesel compounds: Methyl myristate, methyl laurate and methyl caprate

In order to provide the basic thermophysical property data for the research of alternative clean fuels, the liquid thermal conductivity of methyl myristate, methyl laurate and methyl caprate which are considered as the main compounds of biodiesel was reported. The measurements of three fatty acid esters, covering a temperature range from (292 to 372) K and pressure up to 15 MPa, have been performed by a transient hot-wire technique with a bare platinum hot wire. The relative uncertainty of the experimental results was estimated to be ± 2.0% (in the 0.95 confidence level). The present thermal conductivity data were correlated as a polynomial function of temperature and pressure for the purpose of interpolation.

Macrosegregation in the Weld Pool in Metal Inert-Gas Welding of Aluminium

• Arc welding of Al alloys is modelled in lap and bead-on-plate geometries • Detailed thermophysical properties are given for aluminium–silicon–magnesium alloys • The filler metal is concentrated near the bottom of the fusion zone • A more vertical electrode orientation reduces macrosegregation in lap welds • The model is validated against measurements of weld cross-section composition A computational model of metal–inert-gas arc welding, in which the arc plasma, the wire electrode and the workpiece are included in the computational domain, is used to investigate the macrosegregation of the filler metal (the wire electrode alloy) and the base metal (the workpiece alloy) in the weld pool. The aluminium–silicon alloy AA4043 is used for the wire electrode, and the aluminium–magnesium alloy AA5754 for the workpiece. Detailed thermophysical property data for aluminium–silicon–magnesium alloys are given. Modelling results are presented for lap geometry, including different electrode angles, and for bead-on-plate geometry. It is found that the filler metal is concentrated in the region near the boundary of the fusion zone and the base metal. This concentration occurs because of the convective flow of the filler metal towards this boundary, which is in turn driven by the momentum transferred to the weld pool by the droplets. This mechanism is consistent with one of several macrosegregation mechanisms proposed in the literature based on experimental observations. The macrosegregation in lap welds is predicted to be reduced when the electrode orientation is closer to vertical. Measurements of the concentration of silicon and magnesium in weld cross-sections for bead-on-plate and lap geometry were used to confirm the distribution of filler metal predicted by the model are consistent with experiment.

Thermodynamic and thermophysical properties of holmium orthovanadate

The current paper reports thermodynamic and thermophysical property data on holmium orthovanadate over a wide temperature range. The heat capacities of HoVO4 have been measured using precision adiabatic calorimetry and differential scanning calorimetry over the temperature ranges of 7–343 K and 337–1097 K, respectively. A broad heat capacity anomaly, centred at 15 K, has been observed. The standard entropy of HoVO4 at 298.15 K, derived from low-temperature heat capacity data, has been estimated. This value, in conjunction with available thermodynamic data, has been used to evaluate the standard Gibbs energy of formation of HoVO4 from the elements. The temperature dependences of standard thermodynamic properties have been calculated from 0 K to 1100 K. Thermal diffusivity measurements for HoVO4 have been conducted from ambient temperature to 1073 K, using a laser flash method. The thermal conductivity has been evaluated on the basis of the heat capacity and thermal diffusivity data obtained.

Experimental and theoretical study of a vertical tube in shell storage unit with biodegradable PCM for low temperature thermal energy storage applications

This article presents the experimental investigations of the coconut oil-based TES module for HVAC applications in the ambient and-sub ambient temperature range. To properly study this problem modular experimental module and test loop were developed. Special attention has been paid to study the physical mechanism of the melting/solidification process for natural substance (coconut oil) which has perspectives to be used in thermal energy storage systems. It has been a highlight that the melting/solidification process is much more complex for non-eutectic mixtures and there are limited analytical models witch could be used to design TES working with such substances. Due to the limit of literature data for thermophysical properties of coconut oil own experimental data has been conducted.The article presents both visual and thermal characteristics of the melting and solidification process. It has been confirmed the strong influence of natural convection phenomena at the melting process. What is more, it has been observed that in the case of coconut oil it is better to talk about appearance melting temperature than melting temperature. The experimental analysis confirmed that appearance melting temperature is a function of radial distance from the heat source. In the case of solidification, the influence of natural convection is reduced quickly due to the increasing domination of the conduction heat transfer mechanism. For the solidification temperature profiles are characteristic of the occurrence of subcooling temperature. The level of temperature drop in sub cooling is a function of radial distance from the heat source. It has been also confirmed that in case of melting as well as solidification process the shape of the phase-change profile seems to form a truncated cone (in case of melting inverted).To validate the engineering approach to vast discrepancies in the literature data own experiment has been evaluated with a simple mathematical model to verify the applicability of the literature data in system behavior prediction. Based on the best-fit approach the parameters thermal resistance of the module R = 1.3 W/K was found. Additionally the latent heat of the coconut oil of 178 kJ/kg with Gaussian distribution (σ=1.1) for melting in temperature of 25 °C and solidification at 21 °C. The proposed correlation can be easily used to optimize latent thermal energy storage cooperated with the HVAC system.

DETECTION OF DENSE, OVERLAPPING, GEOMETRIC OBJECTS.

Using a unique data collection, we are able to study the detection of dense geometric objects in image data where object density, clarity, and size vary. The data is a large set of black and white images of scatterplots, taken from journals reporting thermophysical property data of metal systems, whose plot points are represented primarily by circles, triangles, and squares. We built a highly accurate single class U-Net convolutional neural network model to identify 97 % of image objects in a defined set of test images, locating the centers of the objects to within a few pixels of the correct locations. We found an optimal way in which to mark our training data masks to achieve this level of accuracy. The optimal markings for object classification, however, required more information in the masks to identify particular types of geometries. We show a range of different patterns used to mark the training data masks, and how they help or hurt our dual goals of location and classification. Altering the annotations in the segmentation masks can increase both the accuracy of object classification and localization on the plots, more than other factors such as adding loss terms to the network calculations. However, localization of the plot points and classification of the geometric objects require different optimal training data.