Thermophysical Properties Research Articles

Experimental investigation of thermophysical properties of propylene glycol based secondary fluids for ground source heat pumps and indirect refrigeration systems

More than 1.7 million ground source heat pumps are currently in operation in the European Union and a large majority of systems is using propylene glycol as secondary fluid. In this study the thermophysical properties of propylene glycol solutions with specific freezing points between −5 and −50 °C are investigated at low temperatures of interest for refrigeration and heat pump applications. The experimentally determined data are compared to a large number of data from the literature. It has been found that the freezing point results for all concentrations were in very good agreement with both Melinder (2010) and ASHRAE (2021) data. Moreover, the literature data and present study for concentrations above 40 wt-% have different density curve slopes compared to ASHRAE data. The viscosity results for concentrations below 40 wt-% were up to 21.5 % higher than ASHRAE data and the viscosity results for solutions with concentrations above 40 wt-% were lower by up to 9.7 %. The thermal conductivity results for concentrations above 40 wt-% were 10 % higher than ASHRAE (2021) data. The experimental specific heat capacity curves and other studies do not have the same linear trend as Melinder (2010) and ASHRAE (2021) data. This difference indicates that currently available ASHRAE data have been indirectly computed from thermal conductivity data or that they have not been fully experimentally validated. Finally, more studies are required to investigate concentrations below 25 wt-% to identify solutions with higher specific heat capacity than water that could be of interest for specific applications.

Heat and mass transfer analysis of conducting non-Newtonian nanofluid flows over an elongating sheet with a non-uniform heat source

Nanofluids help in many fields to improve the performance of thermal systems by augmenting heat transfer rates through their thermophysical properties. The performance of the nanofluids with various base fluids may be different. Therefore, the study and comparison of behaviors of various nanofluids are useful in several applications such as fuel as a coolant in automobiles, and in medical and electronic equipment to reduce the thermal resistance. This research proposed a novel model to investigate the flow behavior of three different nanofluids over an elongating surface in the presence of a non-uniform heat source and thermal radiation effects. This investigation describes how the considered nanofluids behave in the presence of a transverse magnetic field, and other effects. The proposed governing boundary layer partial differential equations (PDEs) are reformed into a system of nonlinear ordinary differential equations (ODEs) by introducing the proper similarity transformation. The finalized equations are solved numerically with the help of the ND solve package in Mathematica software. We intended how the fluid flow and heat transfer are affected by non-dimensional controlling factors with the help of graphics. Further, the calculations and discussions are accompanied by the numerical values of the skin friction coefficient and heat and mass transfer rates. According to the current findings, the Maxwell nanofluid exhibits superior performance in velocity, and the Oldroyd-B nanofluid shows more concentration and less temperature. As a special case, the results of this investigation are compared with the existing results, and found a good agreement between the results.

Effects of thermal boundary conditions on Stokes' second problem

In this investigation, an infinite flat plate is employed to examine the flow behavior of Casson fluid and the associated heat transfer phenomena. The plate undergoes an initial acceleration with a constant velocity until it eventually decelerates to rest. The energy equation incorporates the effects of viscous dissipation. An appropriate similarity transformation transforms the governing equations into coupled nonlinear ordinary differential equations (ODEs). A closed-form solution for the velocity profile is obtained, while the energy equation is solved using the built-in function NDSOLVE in Mathematica. The study investigates the influence of governing parameters on dimensionless velocity, temperature, skin friction, and local heat transfer rate under two thermal boundary conditions: Newtonian heating and convective boundary conditions. The fluid's thermophysical properties remain constant throughout the study, with the surface temperature of the plate assumed to be fixed at a constant value. A graphical analysis examines the flow behavior and temperature distribution, revealing the impact of non-dimensional parameters. This study reveals that thermal boundary conditions significantly influence heat transfer rates, with Newtonian heating leading to an increase and convective heating causing a decrease. This is attributed to the direct application of heat at the boundary in Newtonian heating, which enhances thermal energy transfer. In contrast, convective heating disperses heat through fluid motion, limiting transfer rates.

Effect of Calcium Addition on the Aluminum Alloy A201 Foam

To study the effect of calcium on the porosity, sphericity, and microstructure of Al–Cu foams, a gradient calcium content (0.5, 1.0, 1.5, and 2.0 wt%) is added into aluminum A201 alloy (Al–Cu alloy) for the cellular aluminum foam preparation via the melt foaming method (TiH2 is used as a bubbling agent). Thereafter, the porosity of the prepared Al foams and their pore size are found to increase, and the sphericity of pores tends to approach to unit with calcium addition. This phenomenon is then explained through the modified thermophysical properties (i.e., surface tension and viscosity) of A201 alloy melts caused by the calcium addition. After the microstructure analysis, a bunch of secondary phases in the A201 + Ca alloy foams, e.g., CalAl2Si2, Al2Cu, and Al20CaTi2 as well as an eutectic phase with a great copper content Al8CaCu4 are detected by means of scanning electron microscopy/energy‐dispersive X‐Ray spectroscopy and X‐Ray diffraction analysis.

Agricultural Waste Valorization for Nanoparticles Synthesis and Enhancement of Vapour Compression Refrigeration System’s Performance

Waste management has been a major concern in the society and agricultural wastes can be utilized in the synthesis of nanoparticles and deployed in the vapour compression refrigeration system (VCRS) to enhance its performance. This study analysed the thermophysical properties, performance, energy consumption, pull-down time, and capacities of VCRS using bio-nanoparticles produced from orange and pineapple peels. Eco-friendly refrigerants R600a and R134a with pure polyolester (POE) as the lubricating oil for the compressor were used. The nanolubricants were dispersed in three volume fractions of 0.05%, 0.10% and 0.20% concentration in the lubricant using the two-step method. The degradation of nanolubricants were analysed by examining the thermophysical properties of the nanolubricants before and after use in the VCRS. At 0.2% volume concentration, optimum COP of 6.31 and 5.01 were obtained for pineapple and orange peels respectively for R600a. The nanolubricants of orange peels with the volume fraction of 0.2% had the best pull-down time with a temperature of-2oC. The lowest power consumption was observed for 0.1% volume concentration of pineapple nanolubricants while 0.2% volume concentration of orange nanolubricants was observed to have the least power consumption. Considering the R134a refrigerant, the volume concentration with the optimum COP was 0.1 vol% concentration for the orange bio-based nanolubricants with an increase in the COP of 36.3% when compared with pure R134a while 0.2 vol% had the best pull-down time with a temperature of-3oC. There was a 14.2% drop in the power consumption of 0.1 vol% concentration of pineapple nanolubricants when compared to the various concentrations of the bio-based nanolubricants. From this study, the optimum performance was observed at 0.20 vol% concentration for the orange and pineapple nanolubricants with a relatively less power consumption. R600a refrigerant can completely replace R134a in its use in refrigeration systems and achieve similar pull-down time and coefficient of performance when bio-nanolubricants are utilized in the systems.

Средства реализации языкового смысла «признак предмета» в профессиональной сфере «военное строительство»

<p>The article examines the linguistic means of expressing the linguistic meaning of the «feature of the subject» in the military engineering sublanguage. Relative adjectives describing various properties of building materials and their single-root nouns are relevant for the construction sector. Adjectives denoting hydrophysical, thermophysical, physico-chemical, mechanical, chemical, technological, operational and special properties are used to characterize building materials. Quantitative numerals are less likely than ordinal adjectives to participate in the expression of the linguistic meaning of the «feature of the object» and are inconsistent, non-morphologized definitions, however, in the military engineering field they are active in characterizing the quantitative parameters of temperature, thickness, depth, height and other characteristics of construction objects. The onomasiological correlation between relative adjectives and participles in the construction sector is observed in constructions, «adjective name» is «an object with a certain quality»; «adjective name is an object made of a certain material»; «adjective name is an object built of a certain material». It was revealed that speakers prefer the use of relative adjectives to denote the construction materials used; participles — to denote construction technological processes; quantitative numerals — to denote the nomenclature of construction mechanisms. Adjectives and participles as part of terminological combinations represent a contamination of the linguistic meanings of «subject attribute» and «subject».</p>

Experimental investigation of thermophysical properties of synthesized Mg–Al bimetal oxide/water nanofluid

Experimental investigation of thermophysical properties of synthesized Mg–Al bimetal oxide/water nanofluid

Application of Caputo fractional approach to MHD Casson nanofluid with alumina nanoparticles of various shape factors on an inclined quadratic translated plate

The present study aims to examine the effect of convective heat transfer of nanofluid past an inclined plate. This paper scrutinizes heat transfer over an inclined surface of alumina nanofluids under the influence of radiation and magnetic fields with temperature-dependent thermophysical properties. The mathematical findings of velocity and temperature distributions are examined and visualized using non-dimensional flow parameters. The core of the research is to know the impact of using shape effects of alumina nanoparticles with a variety of base fluids like water, ethylene glycol, and engine oil. The outcomes concluded that the friction of the non-Newtonian viscous fluid decreased with increasing the inclination of the surface. The governing equations of the flow have been developed by using a few approximations such as Boussinesq's, and Roseland's. Using the dimensional analysis, the initial governing equations are simplified to dimensionless partial differential equations. A fractional model is developed using the Caputo fractional derivative. The solution of the proposed fractional partial differential equations is obtained in terms of special functions, Wright function, and Mittag-Leffler function by using the Laplace transformation method. Based on the interpretation, it is found that a reduction in velocity is observed with an increase in the angle of inclination i.e., γ = π/3 to γ = π/2. From the analysis, it is found that alumina/engine oil can carry higher temperatures than compared to other nanofluids and thus is a good option for heat transfer devices.

Identification of the surface heat flux of charring ablative materials using dynamic Bayesian network based on multisource information fusion

In order to solve the dual uncertainty problem between heat flux and thermophysical properties in the identification of the heat flux of charring ablative materials, a dynamic Bayesian network (DBN) based on multisource information fusion is proposed. The method is divided into two stages, with thermophysical properties identified in the former stage and the heat flux identified in the latter stage. A one-dimensional pyrolysis layer model is adopted to characterize the ablation process of materials. In the DBN, the multisource information of surface recession and temperature history data are considered as observation nodes. Sensitivity analysis is used to determine the key parameters in each time step in the DBN, and only key parameters are identified in the corresponding time step. Thus, with the increase of types of information and the decrease of the number of simultaneous identification parameters, the identification accuracy can be improved. The method was verified by numerical and experimental cases. In the numerical cases with noise and experimental cases, the maximum error of using the proposed method was 3.27% and 2.55%, respectively. Compared with only considering the temperature information, the relative errors of the identification results considering multisource information fusion were reduced by 83.95% and 47.53%, respectively.

Statement of Retraction: Synthesis of Nanocrystalline Polycalix[4]amides Containing Mesogenic Triazole Units and Investigations of Their Thermo Physical Properties and Heavy Metal Sorption Behavior

Statement of Retraction: Synthesis of Nanocrystalline Polycalix[4]amides Containing Mesogenic Triazole Units and Investigations of Their Thermo Physical Properties and Heavy Metal Sorption Behavior

Thermophysical properties and geochemical characteristics of granites in the Tengchong area: Indications for resource potential of hot dry rocks

Ascertaining regional radiogeochemical characteristics and lithospheric thermal structure characteristics is paramount for identifying the resource potential of hot dry rocks (HDRs). This study conducted thermal conductivity testing and whole-rock analyses of outcrop granites of different formation epochs from the Tengchong area. Moreover, combined with the previously published whole-rock data and the data related to radioactive heat production rates, this study conducted geological, geophysical, and geothermal analyses. Key findings are as follows: (1) Granites in the Tengchong area exhibit an average radioactive heat generation rate of 5.54 μW/m 3 . Among them, the Late Cretaceous granites have an average radioactive heat generation rate of 8.08 μW/m 3 , suggesting high heat production granites; (2) Granites in the Tengchong area present an average thermal conductivity of 3.135 W/(m·K), relatively akin to the average values of granitic rocks worldwide. Compared to granites of other epochs, the Late Cretaceous granites manifest significantly higher thermal conductivities, with an average of 3.28 W/(m·K); (3) There is a negative correlation between the mica content and the thermal conductivity of the granites in the Tengchong area; (4)The Tengchong area holds potential for HDR exploitation and is inferred to have a lithospheric structure characterized by hot mantle and cold crust.

Influence of Subcooling and pressure on flow boiling in a vertical mini-channel: Heat transfer analysis using inverse method

The background of this study is the problem of thermal runaway in the battery cells of electric vehicles. Increasingly powerful and compact battery packs require highly efficient thermal management. One potential solution is the direct liquid cooling of lithium-ion battery cells using a dielectric liquid which boils over a safety limit temperature. This approach intends to prevent in a first step the cell thermal runaway and if it fails in a second step its propagation to its neighbors: the liquid boiling helps to mitigate the cell temperature rise and to transport and spread the heat. The arrangement of the cells in the pack and their close spacing induce a scientific problem of convective boiling in a mini-channel. To enhance designs using this solution, a comprehensive understanding of flow boiling and a precise local heat transfer quantification is essential. The HFE-7100 has been selected as a working fluid for its attractive thermophysical properties and a suitable saturation temperature.The present paper introduces new experimental results of flow boiling dielectric fluid, the HFE-7100, in a vertical rectangular mini-channel. Measurements are carried out from start of boiling to dry-out. Boiling curves are obtained for a mass flux of 391 kg/(m².s), at different pressures (0.7, 1, 1.5 bar) and at different subcoolings (ΔTsub=0;15;30;45∘C). The test section is an aluminum block instrumented with three lines of five K-type thermocouples located all along the flow. The visualization of the flow is achieved through a glass pane with a high-speed camera to identify different flow patterns. The local heat transfer coefficient is calculated by a resolution of a 2D inverse heat conduction method.The experiment mainly aims at determining the heat transfer coefficient, the critical heat flux (CHF) and the pressure drop and at characterizing both the flow regimes and the dry-out phenomenon. The influence of subcooling and pressure on flow boiling is analyzed. An increase in subcooling enhances the CHF and the heat transfer coefficient, and delays the dry-out. Subcooling has an impact on the flow pattern and modifies the type of CHF. In the operating conditions tested, a decrease in pressure enhances CHF and delays dry-out. On the other hand, the heat transfer coefficient increases with rising pressure. Similarly, pressure drops are lower with higher pressure.

A comparative ab-initio investigation of the physical properties of cubic Laves phase compounds XBi2 (X = K, rb)

In this study, we looked into a number of physical properties of alkali-bismuth compounds XBi2 (X = K, Rb), in the cubic Laves phase (symmetry Fd 3¯ m) using the density functional theory (DFT). The structural, elastic behavior along with Pugh's ratio, Poisson's ratio, Cauchy pressure, anisotropy indices, micro- and macro-hardness, thermo-physical properties such as Debye temperature, sound velocities, Grüneisen parameter, and melting temperature, electronic band structure, and optoelectronic properties has been explored. The computed ground-state lattice parameters and unit cell volume are in close accordance with the known theoretical and experimental findings. The elastic, thermo-physical, and optoelectronic properties of XBi2 (X = K, Rb) are investigated for the first time in this study. The computed elastic constants satisfied the mechanical stability criteria. The estimated Pugh's ratio, Poisson's ratio, and Cauchy pressure signify the ductility of the compounds. In order to understand the electronic properties, band structures and electronic energy densities of states have been explored. These compounds exhibit metallic characteristics in their electrical band structures. We have done a complete investigation on the reflectivity, absorption coefficient, refractive index, dielectric function, optical conductivity, and loss function of these metals. These compounds possess a low Debye temperature, thermal conductivity, and melting point. The optical absorption, reflectivity spectra and the refractive index of XBi2 (X = K, Rb) show that they can be used as solar reflector and ultraviolet absorber. The majority of the findings in this study are novel.

Effect of Bubbling on Ignition of PMMA Slab: Change in Thermo-Physical and Thermo-Radiative Properties

In semi-transparent polymers, ignition is not only dependent on conductive thermal transfer into the material but also on in-depth absorption of the radiation. The aim of this work was to investigate the influence of bubbling on the thermo-physical and thermo-radiative properties of PMMA and how it may affect its ignition. PMMA plates of varying thickness were exposed to the heat flux of two radiative sources with different emission spectra. Exposure was stopped after different periods of time to study bubbling kinetics and bubble size distribution by optical microscopy. Front and back surface temperatures of samples were recorded during heat exposure. The results indicate that the bubble size distribution is closely related to the temperature gradient within the sample. Steep thermal gradients lead to small-sized bubbles underneath the exposed surface, while weak thermal gradients generate a wider size distribution with in-depth bubbling. All thermo-physical quantities k, ρ and Cp were shown to decrease with increasing bubbling degree. Likewise, it was highlighted that bubbling modifies the thermo-radiative properties of PMMA, especially in the near-infrared range. Transmittance decreases while absorbance increases with a bubbling degree. The increase in the absorption coefficient was attributed to multiple scattering by bubbles that expand the pathway of radiation into the materials. It was concluded that changes in both the thermo-physical and thermo-radiative properties with bubbling were likely to account for the delay in ignition observed when using the near-infrared heating source.

MULTIFACTOR ANALYSIS OF THE EFFICIENCY OF THE FERROALLOY PROCESS

Ore-reducing ferroalloy processes must be considered as a relationship of parameters and characteristics of subsystems and elements. The maximum energy capacity of the furnace and its productivity is achieved both due to the design parameters of the bath, the short network, the power of the furnace transformer, the diameter of the self-ignition electrodes, as well as the electrotechnological and thermophysical properties of the initial charge materials, ore-slag melt and final ferroalloy. The amount of carbon is one of the most significant technological parameters of the carbon reduction process for the production of manganese ferroalloys. In the work, the most significant final indicators are adopted and their correlation with electrical characteristics and technological parameters is determined.

Effects and mechanism of thermal insulation materials on thermal runaway propagation in large-format pouch lithium-ion batteries

The large heat transfer area of large-format lithium-ion batteries primarily facilitates conduction heat, which is responsible for triggering the thermal runaway of adjacent cells. Therefore, the primary consideration is to utilize thermal insulation materials between cells in order to slow down or prevent the process of thermal runaway propagation. In this study, three varieties of thermal insulation materials were employed to insulate individual cells within a module comprising three large-format pouch cells. These materials include pre-oxygenated wire aerogel (AG-ST-POF), polymer-coated pre-oxygenated wire aerogel (PC-AG-ST-POF), and silicone (SI). The study experimentally examined the thermal runaway propagation (TRP) behavior of the battery module under conditions without insulation materials and with various types of insulation materials. The impact of thermal insulation materials on the TRP among cells was analyzed. The study revealed that none of the three materials completely suppressed the propagation of thermal runaway, although they did impede its progress. The overall impact of AG-ST-POF surpassed that of SI and PC-AG-ST-POF. Furthermore, the mechanism by which thermal insulation materials influence TRP was explored. The results of the thermophysical properties testing suggest that evaluating the impact of materials on TRP solely through thermal conductivity is not a reliable approach. Alternatively, the maximum service temperature and thermal diffusion coefficient are critical parameters for the selection of thermal insulation materials. This study can provide a valuable reference for process engineering design and application in the context of lithium-ion batteries, with the aim of mitigating the risk of TRP.

ПРОГНОЗУВАННЯ ВЛАСТИВОСТЕЙ ЛЕГУЮЧИХ ДОБАВОК – ВАЖЛИВА СКЛАДОВА ОДЕРЖАННЯ ЯКІСНОГО МЕТАЛУ

The main goal of the work is to predict the complex of physicochemical and thermophysical properties of additives from the standpoint of their contribution to the directed formation of the quality of steels. As a scientific basis for the development of analytical dependencies, the work uses the original concept of directional chemical bonding, the core of which is the consideration of metal melts as chemically unified systems, and not a mechanical mixture of constituent elements, and taking into account the contribution of all components, even in small concentrations, as well as the accumulated experience of creating information and analytical systems for forecasting and management of iron and steel smelting processes at the Iron and Steel Institute of Z.I. Nekrasov National Academy of Sciences of Ukraine. The information component is a database on the properties of metallurgical melts, namely the "Ferroalloys" database chosen as the starting point for modeling, which is continuously updated with modern data. A successful combination of information and scientific resources ensured the development of stable models with high forecast accuracy (R2 ≥ 0.95) for domestic brands of ferroalloys (ferromanganese, ferrosilicomanganese, metallic manganese). The findings presented in this work are recommended for integration into the automated technological process management systems of steelmaking with the aim of further forming a competitive final product.

Prandtl and Ohnesorge numbers dependent of ultrasonic horn energy in Newtonian liquid under batch and continuous flow

The level of knowledge on the non-thermal contribution of ultrasonic wave’s energy to perform physico-chemical phenomena is one of the bottlenecks for the commercialization purposes. Under constant nominal power of transducer (Pn), the input electrical power (Pin) is less and sensitive to the medium’s physical properties. This study attempts to assess the conversion of acoustic to thermal power experimentally and numerically using COMSOL Multiphysis@ for a 24 kHz horn-type sonicator through a medium without any sono-chemical effect. Single- and homogeneous two-phase Newtonian mixtures of sunflower oil and water (o/w) with a relatively wide range of density (914–998 kg/m3) and viscosity (0.5–63.5 mPa.s) were irradiated in a lab-scale vessel (1 L) under batch and continuous flow configuration. The direct influence of Pn (80–400 W) and o/w ratio (0–1) on temperature rise and subsequent thermo-physical properties of liquid and the indirect influence on Pin and thermal energy conversion (TEC) were investigated employing calorimetric method. A new engineering concept including a power factor correlation was proposed and validated for prediction of Pin as a function of liquid space velocity (ϑ), temperature, Prandtl (Pr) and Ohnesorge (Oh) dimensionless groups. The results showed that under constant temperature and Pn, increasing Pr and Oh increased Pin with a similar trend for both modes of operation. An increase in temperature directly led to a decrease in Pin with a power factor closed to “-1”. The Pin in continuous flow was higher compared to batch configuration at similar temperature, liquid properties, and Pn. This effect was more significant with increasing ϑ. An increase in ϑ at constant Pn led to a decrease in the inlet/outlet temperature difference in continuous flow and an increase in Pin. Increasing Pn resulted in higher TEC for both configurations; however, TEC was relatively lower in continuous flow than batch configuration indicating more efficient sonication in continuous flow.

Elevating thermal comfort with eco-friendly concrete roof tiles crafted from municipal solid waste

Developing eco-friendly construction materials is imperative from an energy and environmental standpoint. This technical study investigates the sustainable utilization of municipal solid waste incinerated fly ash (MSWIFA) as a substitute for M-sand in construction materials. This study primarily focuses on reducing landfill waste and promoting waste reuse in the construction sector. This study evaluates various thermo-physical properties of MSWIFA-based concrete, including solar reflectance index, slip and skid resistance, straightness, flatness, rectangularity, water absorption, wet transfer, and thermal performance metrics such as heat flow values for thermal comfort and solar emissivity. The proposed concrete tiles have suitable thermal emissivity (0.87), solar reflectance (0.8), and solar absorption (0.26), which are appropriate for eco-friendly building techniques. The use of MSWIFA tiles lowered the indoor temperature by 2 °C when compared to conventional roof tiles at similar ambient conditions. MSWIFA-based concrete roof tiles are promising in terms of thermal comfort, energy efficiency, environmental conservation and waste reduction and promote a more sustainable approach in the construction industry. This research emphasizes the potential of waste-to-resource strategies in achieving sustainable development goals and reducing the ecological footprint of construction materials.

Numerical study of the use of shear-thinning nanofluids in a microchannel heat sink with different pin densities and including vortex generator

This article numerically investigates the thermal and hydraulic performance of shear-thinning nanofluids when used as heat-conducting fluids in a microchannel heat sink device. Five geometries are evaluated: four with different pin densities and one with vortex generators. Six Reynolds numbers are studied, ranging between 200 and 1200. Numerical experiments show a comparison of using a water/ethylene-glycol mixture with and without alumina nanoparticles and multiwalled carbon nanotubes. Two different concentrations of nanoparticles were evaluated, both given shear-thinning nanofluid behavior. The viscous properties of the fluids are fitted from previously reported experimental data. The other thermophysical properties are modeled using single-phase expressions adjusted to consider hybrid nanofluids. Numerical results show that the heat transfer rates and pressure drop increase when the pin density increases, resulting in thermal blocking in the case of higher pin density. These key findings are a result of the increase in the heat transfer of shear-thinning nanofluids and the reduction of the pressure drop when compared with Newtonian fluids. Apparent viscosity contours are used to understand the thermal and hydraulic performance. Between the two nanofluids studied, the one with the lowest power-law index was the best in terms of heat extraction and pressure drop, indicating that fluids with thinning rheology may be recommended for heat transport in microchannel heat sink devices.