Isobaric Specific Heat Capacity Research Articles

Modified Landau model for fluids: A rethink of pseudoboiling theory for supercritical fluids

A new model based on Landau theory is proposed that can quantitatively predict the density, isobaric specific heat capacity distortions of supercritical fluids. Unifying supercritical fluids into classical Landau gas-liquid transition theory, this model gives reasonable explanations for subcritical gas-liquid transition and critical/pseudo-critical phenomena. The results indicate that as inner fluctuations diminish away from the critical point, macroscale mean field approximations are valid, although microscale inhomogeneity exists. Based on the model, disputable pseudoboiling theory is reanalyzed. The thermodynamic stabilities of the supercritical and subcritical transitions are essentially different. Although transitions between the gas-like regime and liquid-like regimes exist, the separation and coexistence of these two regimes on a macroscopic scale never occur in supercritical fluids. For most applications, supercritical fluids can be regarded as single-phase fluids with anomalous properties. In the vicinity of the critical point, the classical description is invalid as the correlation length is on the macroscopic scale.

Thermodynamic Aspects of Pavement Engineering

Scientific and practical calculations on the thermal stability of typical automobile road surface (semi-limited objects) with fluctuations in air temperatures, transitions from positive to negative, with actual heat transfer coefficients, thermal conductivity of components, specific mass isobaric heat capacities, material densities, periods of regular fluctuations are presented. The study shows that temperature fluctuations occur in road surfaces, therefore deformations are brought about in them, generating thermal cracks. Thermal deformations include free, proportional to temperature gradients, stressed deformations due to temperature stresses, characterized by linear thermal expansion coefficients. In road materials, physical and mechanical properties change over time: strength, moduli of elastic longitudinal deformations, shear, transverse deformation coefficients. Thus, the temperature of pavement materials depends on the coordinates, time, and thermophysical characteristics of the materials. Thermal engineering calculations have shown that many road surfaces have limited thermal stability; under the influence of relatively small external influences, they are more stable (supercooled water vapor exists for a short time, turning into a liquid, saturated, supersaturated steam into a superheated liquid, this depends on the radiation characteristics of the surfaces, the presence of external disturbances, etc.). Thus, a complex non-stationary thermal regime takes place, when the temperature fields of the coatings, their gradients of temperature potentials, and masses depend on the boundary conditions of the 1st–4th kind. A citation analysis of the data of the Journal Citation Reports of world scientific serial publications has been developed to carry out research on heat and mass transfer in road surface. The analysis shows that in order to improve the reliability and durability of pavements, fundamental studies of both the physical and technical and thermal properties of all components of road construction mixtures are of great importance.

Способ модификации конструкции хлебопекарной печи на основе принципов принудительной конвекции

The problem of producing environmentally friendly and harmless food products requires not only high-quality raw materials, but also the modification of technological equipment for baking. The main direction of the modification is to reduce the loss of nutritional value of the feedstock in the production of bread, resource saving and environmental friendliness. The implementation of these directions when modifying the design of bread machines is possible based on the application of the principles of desegregation and forced convection. In order to ensure the required parameters of the technological process for the production of bread from whipped yeast-free dough in a modified design of the apparatus, onstructive solutions for improving the baking chamber are proposed. The obtained density indicators of specific isobaric heat capacity, thermal conductivity and dynamic viscosity with an infrared heating system for a dough piece made from whipped yeast-free dough make it possible to determine and correct the characteristics of technical devicesincluding the design of the apparatus. The results of experimental studies of the proposed designs of devices for the production of whipped yeast-free dough and bread baking allow us to conclude that the proposed technical solution provides a reduction in baking time by 27–32 %, heat loss by 23–25 %, energy resources by 17–19 %, material consumption by 20–25 %. The proposed design changes ensure the production of environmentally friendly bakery products through the use of physical principles that do not destroy the molecular structure of the feedstock.

Thermodynamic and Transport Properties of Biomass-Derived Furfural, Furfuryl Alcohol and Their Mixtures

The limited reserves and well-known disadvantages of using fossil energy sources have increased the need for appropriate renewable substitutes in the production of various chemicals and materials. Biomass has been shown to be worthy of attention since it can be converted to biofuels and value-added chemicals relatively easily. The design of biomass valorisation process requires knowledge on the thermodynamic behaviour of the biomass-derived compounds, such as furfural and furfuryl alcohol. The thermodynamic and transport properties of the binary system furfural + furfuryl alcohol were studied at various temperatures and pressures. Density, speed of sound and refractive index were measured in the temperature range T = (288.15–345.15) K and viscosity was measured at temperatures up to 373.15 K, all at atmospheric pressure. Further, the density of pure components was obtained in the temperature range (293.15–413.15) K for furfural and (293.15–373.15) K for furfuryl alcohol at pressures up to 60.0 MPa. The obtained density values were correlated using the modified Tammann–Tait equation with an average absolute deviation lower than 0.009% for furfural and furfuryl alcohol. The optimised parameters were used for the calculation of the isothermal compressibility, the isobaric thermal expansivity, the internal pressure and the isobaric and isochoric specific heat capacities. The reported data are a valuable source of information for the further application of the investigated compounds.

Thermophysical properties of the paramagnetic ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate over an extended range of temperature and pressure

The paramagnetic ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate [BMIM][FeCl4] was subject to multiple high-precision thermophysical property measurements under both ambient and high pressure. Density ρ(p0,T) / kg·m−3 and speed of sound u(p0,T) / m·s−1 data at ambient pressure were recorded at temperatures T = (278.15 to 343.16) K using a DSA 5000 M combined vibrating tube densimeter and speed of sound analyser with a standard uncertainty of Δρ(p0,T) = ±0.001 kg·m−3 and Δu(p0,T) = ±0.1 m·s−1, respectively. High-pressure volumetric (p,ρ,T) data were measured on an Anton Paar DMA HPM vibrating tube densimeter at T = (273.16 to 413.15) K and at pressures up to p = 140 MPa with an estimated experimental relative combined average percentage deviation (APD) of Δρ(p,T) / ρ(p,T) = ±(0.01 to 0.08) %.The specific isobaric heat capacity cp(p0,T) / J·kg−1·K−1, a caloric property, was determined at T = (273.15 to 413.15) K with an uncertainty Δcp / cp = ±0.5 % using a Perkin Elmer Pyris 1 DSC differential scanning calorimeter. To gain knowledge of transport properties, the dynamic viscosity η(p0,T) / mPa·s at ambient pressure was recorded at T = (275.03 to 413.18) K by an Anton Paar SVM 3000 Stabinger viscometer and additionally an Anton Paar rheometer MCR 302 device with uncertainties of Δη / η = ±0.35 % and Δη / η = ±1 %, respectively.The obtained data were first correlated by empirical polynomial equations of state and further processed by the application of classic thermodynamic potentials to determine isothermal compressibility κT(p,T) / MPa−1, isobaric thermal expansivity αp(p,T) / K−1, thermal pressure coefficient γ(p,T) / MPa⋅K−1, internal pressure pint(p,T) / MPa, specific heat capacity at constant pressure cp(p,T) / J⋅kg−1⋅K−1 and at constant volume cv(p,T) / J⋅kg−1⋅K−1, the difference of isobaric and isochoric heat capacity (cp–cv)(p,T) / J⋅kg−1⋅K−1, speed of sound u(p,T) / m⋅s−1 and ultimately isentropic exponent κs(p,T).This work extends knowledge about the thermophysical properties of [BMIM][FeCl4] particularly to high temperatures and pressures.

Thermal conductivity factor for beef of NOR and DFD grades at the subcryoscopic temperatures

Thermal conductivity factor and specific isobaric heat capacity of food products are currently the most important parameters in the development of mathematical models for food freezing and thawing and in improving production technology. There is significant variance among the existing experimental data for the thermal conductivity factor in meat. Most of the modern calculated relationships are based on the nutritional approach, which favorably differs by the ability to calculate the thermophysical characteristics of any food products. However, the calculation error at the subcryoscopic temperatures may be 15% to 20%. The development of superchilling as a way of storing meat requires high accuracy of freezing time calculation, including vacuumpacked boneless meat. In the presented article, the authors investigated hydrogen index, cryoscopic temperature, frozen moisture proportion and thermal conductivity factor for beef M. longissimus dorsi samples of NOR and DFD grades. It was found that DFD beef is characterized by 10% to 12% higher values of thermal conductivity factor in comparison with NOR grade. Using the method of regression analysis, the authors developed empirical relationships for calculating the thermal conductivity factor of meat depending on its temperature and pH level. Unlike cryoscopic temperature and frozen moisture proportion, pH is easy to measure and may be easily used on a conveyor belt for more accurate assessment of meat thermophysical properties. With an increase in pH from 5.3 to 7, an increase in cryoscopic temperature is observed from minus 0.94 °C to minus 0.72 °C. It has been shown that one of the factors for the higher cryoscopic temperature and higher pH level of DFD beef is higher water-holding capacity with less strongly bound moisture.

The isobaric heat capacity of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) at temperatures from (230 to 285) K and pressures up to 8 MPa using a new flow calorimeter

In this paper, a new flow calorimeter was developed to measure the isobaric specific heat capacity (cp) of liquids. The uncertainties of temperature, pressure, and cp were estimated to be less than 11 mK, 0.02 MPa and 1.26%, respectively. The pure 1,1,1,2-tetrafluoroethane (R134a) was measured at temperatures from (230 to 285) K to quantitatively calculated the heat leakage at different temperatures. In order to verify the reliability of apparatus, the cp for R134a and difluoromethane (R32) were obtained at temperatures from (230 to 285) K and pressures up to 8 MPa. Measurements of R134a and R32 show good agreement with the reported data and the high-precision Helmholtz energy equations of state (EoSs). Finally, a total of 33 cp data for 2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) were obtained at temperatures from (230 to 285) K and pressures up to 8 MPa. The presented cp data show good agreement with the published data and two Helmholtz energy EoSs developed by Akasaka et al. and Richter et al. with the average absolute relative deviations (AARDs) of 0.92% and 1.80%, respectively. The Helmholtz energy EoS developed by Akasaka et al. gives a better prediction performance for the cp of R1234yf at low temperature than the other EoS.

Isobaric Specific Heat Capacity for Al2O3/Water Ethylene Glycol Mixture Nanofluid

Abstract Specific heat is a vital characteristic of nanofluids. The present work is an experimental assessment for the isobaric specific heat measurements for the Al2O3 nanoparticle dispersed in a base fluid of different mixture of ethylene glycol and water at 30, 40, 50, and 60 vol% based. The experiments were conducted over temperature range from 35 to 105 °C with nanoparticle concentrations of 0.5–2.5 vol%. The results indicated that the specific heat of nanofluid decreases as the nanoparticle volume increases and percentage of ethylene glycol in base fluid increases but increases as the temperature increases. This characteristic demonstrates that the use of nanofluids should be at as high temperature as possible to fulfill a good beneficial effect. A new correlation from the measurements with maximum deviation of 2.2% was found to estimate the specific heat for these nanofluids.

Thermodynamic Study of Energy Consumption and Carbon Dioxide Emission in Ironmaking Process of the Reduction of Iron Oxides by Carbon

Carbon included in coke and coal was used as a reduction agent and fuel in blast furnace (BF) ironmaking processes, which released large quantities of carbon dioxide (CO2). Minimizing the carbon consumption and CO2 output has always the goal of ironmaking research. In this paper, the reduction reactions of iron oxides by carbon, the gasification reaction of carbon by CO2, and the coupling reactions were studied by thermodynamic functions, which were derived from isobaric specific heat capacity. The reaction enthalpy at 298 K could not represent the heat value at the other reaction temperature, so the certain temperature should be confirmed by Gibbs frees energy and gas partial pressure. Based on Hess’ law, the energy consumption of the ironmaking process by carbon was calculated in detail. The decrease in the reduction temperature of solid metal iron has been beneficial in reducing the sensible heat required. When the volume ratio of CO to CO2 in the top gas of the furnace was given as 1.1–1.5, the coupling parameters of carbon gasification were 1.06–1.28 for Fe2O3, 0.71–0.85 for Fe3O4, 0.35–0.43 for FeO, respectively. With the increase in the coupling parameters, the volume fraction of CO2 decreased, and energy consumption and CO2 output increased. The minimum energy consumption and CO2 output of liquid iron production were in the reduction reactions with only CO2 generated, which were 9.952 GJ/t and 1265.854 kg/t from Fe2O3, 9.761 GJ/t and 1226.799 kg/t from Fe3O4, 9.007 GJ/t and 1107.368 kg/t from FeO, respectively. Compared with the current energy consumption of 11.65 GJ/t hot metal (HM) and CO2 output of 1650 kg/tHM of BF, the energy consumption and CO2 of ironmaking by carbon could reach lower levels by decreasing the coupled gasification reactions, lowering the temperature needed to generate solid Fe and adjusting the iron oxides to improve the iron content in the raw material. This article provides a simplified calculation method to understand the limit of energy consumption and CO2 output of ironmaking by carbon reduction iron oxides.

Study on thermophysical properties of alumina nanoparticles enhanced ionic liquids (NEILs): A modeling approach

In the present work, artificial neural networks have been developed to predict the relationship and influence of shear rate/temperature and particle loading on the viscosity, density, thermal conductivity and isobaric specific heat capacity of Al2O3 nanoparticles dispersed in a binary mixture of water and ionic liquid ([C2mim][CH3SO3]/water). The properties of the alumina nanoparticles enhanced ionic liquids with respect to the base fluids have been modeled using feed-forward back-propagation (BP) ANNs. The study has disclosed that the developed models predict the thermophysical properties of NEILs with reasonable accuracy. The regression coefficient (R) of developed models is noted to be greater than 0.99. Moreover, the root mean square errors for the developed models were found to be in the range of 0.0007–0.081, revealing an excellent compliance between the experimental and calculated thermophysical properties of NEILs.

Thermophysical Properties of Mixtures of Titanium(IV) Isopropoxide (TTIP) and 2-Propanol (iPOH)

The present work provides thermophysical data on binary mixtures of titanium(IV) isopropoxide (TTIP) and 2-propanol (iPOH), which are important precursor solutions in spray flame synthesis of nanoparticles. The specific density, viscosity, thermal conductivity, and molar isobaric heat capacity were measured at 101.3 kPa and temperatures ranging from 293.15 to 333.15 K. The vapor–liquid equilibrium (VLE) was measured at pressures ranging from 20 to 80 kPa. Furthermore, self-diffusion coefficients of pure iPOH were measured at 101.3 kPa and temperatures ranging from 293.15 to 333.15 K. A qualitative study using 1H NMR spectroscopy provides evidence for a cross-association between TTIP and iPOH in the mixture. Correlations for all studied thermophysical properties are provided. The results establish a rational basis for the design of spray flame synthesis processes.

Theoretical study of the size dependencies of the thermodynamic properties of tungsten at various pressures and temperatures

The parameters of the paired 4-parametric interatomic potential of Mie-Lennard-Jones for bcc-W were obtained. The equation of state, baric and size dependencies of the coefficient of thermal volume expansion, elastic modulus, specific isobaric heat capacity and also specific surface energy of tungsten macro- and nano-crystal were calculated using obtained parameters of interatomic potential. The pressure derivatives of these dependencies were studied also.

Selected water thermal properties from molecular dynamics for engineering purposes

Water is the most commonly used fluid in most heat transfer applications. Estimating water thermal properties in an efficient and reliable way is thus important. We propose here molecular dynamic simulations for this purpose and explore a methodology for calculating water thermal properties from such simulations. This is significant, particularly to compare fluids to design an efficient working fluid for heat exchangers or cooling microelectronic devices. Lammps and Moltemplate models have been used in this study to calculate selected water properties. The atomistic model of water is the extended simple point charge (SPC/E) model. The thermal properties are thermal conductivity, viscosity, density, specific isochoric heat capacity, specific isobaric heat capacity, Prandtl Number, and Volumetric thermal expansion coefficient. These results are compared with experimental published results for water at temperatures 288 K, 300 K, 312 K, and 324 K and pressure 1 atm. The simulated values are sufficiently close to reliable published values, this demonstrates the usefulness of molecular dynamics simulations., which can thus be used as an effective and relatively cheap tool to investigate thermal and dynamic properties of working fluids in thermofluid design.

Experimental study on isobaric specific heat capacity of subcritical and supercritical fluids using flow calorimetry

Accurate measurement of isobaric specific heat capacity of supercritical fluids is essential for many scientific researches and engineering applications. Based on the flow calorimetry method, an online experiment system for measuring isobaric specific heat capacity for subcritical and supercritical fluids was established. The relative expanded uncertainty of isobaric specific heat capacity was estimated to 2.44%–2.70% (coverage factor k ​= ​2). Based on the verification of the reliability of the measurement system by using pure water, cyclohexane and pentane, the isobaric specific heat capacity of carbon dioxide (CO2) in the temperatures range of (25.0–60.0) °C and pressures range of (6.7–12.0) MPa was measured. The experiment platform can provide accurate data measurement support for further scientific investigations and engineering designs.

Thermophysical Properties of Solutions of Iron(III) Nitrate Nonahydrate in Mixtures of 1-Propanol and Water

The simulation of spray flame processes for the production of high-quality nanoparticles relies on thermophysical properties of the precursor solutions, for which literature data are scarce. Here, we report experimental thermophysical data of solutions of iron(III) nitrate nonahydrate (INN) in (1-propanol + water) mixed solvents. The specific density, viscosity, thermal conductivity, and isobaric heat capacity of the solutions were measured at 101.3 kPa between 288.15 and 333.15 K, solvent compositions ranging from 0.73 mol mol–1 1-propanol to pure water, and INN molalities up to 1.3 mol kg–1. Empirical correlations of the experimental data are provided.

A comprehensive numerical model for the thermodynamic and transport properties of H2O-NaCl fluids

Saline fluids are common to a variety of geologic settings in Earth's crust and upper mantle. The binary system H2O-NaCl is commonly used to interpret data obtained from fluid inclusions, and for geochemical modeling of mass and energy transport and fluid-rock interaction. Modeling of fluid properties in this binary system has generally relied on piecemeal compilations from available models specific to certain properties, whereas a standalone, comprehensive tool has been lacking. Here, we present a new computer package, entitled ProBrine (Properties of Brine) to evaluate the thermodynamic and transport properties of H2O-NaCl fluids over the range of temperatures from 0 to 1000 °C, pressure from 1 to 5000 bar, and salinity from 0 to 100 wt% NaCl. ProBrine is designed to calculate a wide range of thermodynamic and transport properties, including (but not limited to): phase equilibria (liquid, vapor, and halite); molar volume, density, specific enthalpy, and viscosity. The program is also equipped to calculate derived properties such as: 1) the coefficient of isobaric thermal expansion; 2) the coefficient of isothermal compressibility; 3) the reduced susceptibility; 4) the isobaric specific heat capacity, and the fluxibility. In addition, the model will calculate solubility of the following six minerals: fluorapatite, calcite, corundum, fluorite, rutile, and quartz, as well as the respective temperature and pressure derivatives, which can be used to predict mineral dissolution and precipitation along a flow path. Moreover, the program is equipped to interpret fluid-inclusion data. The program is written in Visual Basic (VBA) in Microsoft Excel and is released open-source, allowing a user full scope to review, copy, modify and expand the program code.

Analytical Determination of the Nucleation-Prone, Low-Density Fraction of Subcooled Water.

Subcooled water is the primordial matrix for ice embryo formation by homogeneous and heterogeneous nucleation. The knowledge of the specific Gibbs free energy and other thermodynamic quantities of subcooled water is one of the basic prerequisites of the theoretical analysis of ice crystallization in terms of classical nucleation theory. The most advanced equation of state of subcooled water is the IAPWS G12-15 formulation. The determination of the thermodynamic quantities of subcooled water on the basis of this equation of state requires the iterative determination of the fraction of low-density water in the two-state mixture of low-density and high-density subcooled water from a transcendental equation. For applications such as microscopic nucleation simulation models requiring highly frequent calls of the IAPWS G12-15 calculus, a new two-step predictor-corrector method for the approximative determination of the low-density water fraction has been developed. The new solution method allows a sufficiently accurate determination of the specific Gibbs energy and of all other thermodynamic quantities of subcooled water at given pressure and temperature, such as specific volume and mass density, specific entropy, isothermal compressibility, thermal expansion coefficient, specific isobaric and isochoric heat capacities, and speed of sound. The misfit of this new approximate analytical solution against the exact numerical solution was demonstrated to be smaller than or equal to the misprediction of the original IAPWS G12-15 formulation with respect to experimental values.

Viscosity and isobaric specific heat capacity of alumina nanoparticle enhanced ionic liquids: An experimental approach

Temperature and loading dependences on the rheological behavior and isobaric specific heat capacity of several suspensions of alumina nanoparticles in a binary mixture of [C2mim][CH3SO3] ionic liquid and water were experimentally determined to assess its potential condition of enhanced heat transfer fluids. Rheological tests show a clear Newtonian behavior for the base fluid and the NEILs with lower Al2O3 concentrations while higher amounts of alumina nanoparticles entail non-Newtonian fluids and increase in viscosity up to 78%. The heating-cooling viscosity tests reveal that no significant viscosity hysteresis occur and VFT equation adequately describe the temperature dependence. Isobaric specific heat capacities decrease (<10%) with nanoparticle mass fraction and increase (<10%) with temperature. The goodness of the Raud et al. correlation for predicting the isobaric specific heat capacity of nanoparticles enhanced fluids is discussed.

Behavior of Isobaric Heat Capacity of 2,3,3,3-Tetrafluoroprop-1-ene in the Gas Phase

The isobaric specific heat capacity cp of 2,3,3,3-tetrafluoroprop-1-ene was measured in the gaseous state and the behavior was presented in cp–T and cp–p diagrams. A total of 62 cp data were obtain...

Remarkable Thermal Conductivity Enhancement in Carbon-Based Ionanofluids: Effect of Nanoparticle Morphology.

Transfer of the excellent intrinsic properties of individual carbon nanoparticles into real-life applications of the corresponding heat transfer fluids remains challenging. This process requires identification and quantification of the nanoparticle–liquid interface. Here, for the first time, we have determined geometry and properties of this interface by applying transmission electron cryomicroscopy (cryo-TEM). We have systematically investigated how the particle morphology of carbon-based nanomaterials affected the thermal conductivity, specific isobaric heat capacity, thermal diffusivity, density, and viscosity of ionanofluids and/or bucky gels, using a wide range of fillers, especially single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs), both with extreme values of aspect ratio (length to diameter ratio) from 150 to 11 000. Accordingly, hybrid systems composed of various carbon nanomaterials and ionic liquid, namely 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN], were prepared and characterized. Most of the analyzed nanodispersions exhibited long-term stability even without any surfactant. Our study revealed that the thermal conductivity could be remarkably improved to the maximum values of 43.9% and 67.8% for ionanofluid and bucky gel (at 1 wt % loadings of MWCNTs and SWCNTs), respectively, compared to the pristine ionic liquid. As a result, the model proposed by Murshed and co-workers has been improved for realistic description of the concentration-dependent thermal conductivity of such hybrid systems. The obtained results undoubtedly indicate the potential of ionanofluids and bucky gels for energy management.