Isobaric Specific Heat Capacity Research Articles

The isobaric specific heat capacity and viscosity for 3,3,3-trifluoroprop-1-ene in liquid phase at temperatures from (230 to 293) K and pressures up to 8 MPa

In this paper, the 65 isobaric specific heat capacity (cp) and 9 viscosity (η) data of 3,3,3-trifluoroprop-1-ene (R1243zf) were measured at temperatures from (230 to 293) K and pressure up to 8 MPa using a flow calorimeter and a vibrating-wire viscometer. The uncertainty of temperature, pressure, isobaric specific heat capacity and viscosity were evaluated to be less than 11 mK, 0.02 MPa, 1.0 % and 2.7 %, respectively. Three saturated liquid viscosity (ηs) data were obtained based on the extrapolation of the viscosity data. Empirical correlations were established based on the cp and ηs data, the average absolute relative deviation for cp and ηs are 0.5 % and 1.3 %, respectively.

Highly Accurate Densities and Isobaric and Isochoric Heat Capacities of Compressed Liquid Water Derived from New Speed of Sound Measurements

Comprehensive and accurate measurements of the speed of sound in liquid water are reported. The measurements were carried out by a double-path-length pulse-echo technique and cover the temperature range from 273.65 K to 368.15 K with pressures up to 100 MPa. The relative expanded (k=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${ k}=2$$\\end{document}) uncertainties are 2.1 mK in temperature, 45 parts-per-million (ppm) in pressure, and between 40 ppm and 70 ppm in speed of sound. Furthermore, values for the density and specific isobaric and isochoric heat capacities were derived from the speed of sound data in the measured temperature range up to 100 MPa by the method of thermodynamic integration. Very accurate values for the derived properties were obtained by using density data of Takenaka and Masui (Metrologia 27:165–171, 1990) and isobaric heat capacity data of Osborne et al. (J Res Natl Bur Stand 23:197, 1939) at ambient pressure as initial values in combination with an accurate correlation of our speed of sound. The relative expanded (k=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${ k}=2$$\\end{document}) uncertainties of the derived properties are 2 ppm in density, 0.11% in isobaric heat capacity, and 0.12% in isochoric heat capacity. The experimental speeds of sound and derived properties are compared with experimental data of other authors from the literature, the IAPWS-95 (International Association of the Properties of Water and Steam) formulation for the thermodynamic properties of water, and a recent equation of state for supercooled water.

Characterization of the physical properties of the thermoresponsive block-copolymer PAGB2000 and numerical assessment of its potentialities in Forward Osmosis desalination

Forward Osmosis is a promising strategy for desalination processes, however some aspects have to be better characterized to make it competitive with other affirmed technologies. One of these aspects is the selection of the draw agent, i.e., a polymeric solution that has to fulfill different requirements to guarantee both high membrane performances and good regeneration process. Previous studies have identified a thermoresponsive copolymer known as PAGB2000 as potential draw agent. However, in the open literature there is no information on the thermo-physical properties required for a fully characterization of the polymer itself, hence, different experimental campaigns have been conducted to quantify: phase behavior, osmotic pressure, density, dynamic viscosity, thermal conductivity, thermal diffusivity and isobaric specific heat capacity. These properties were then used in a computational model to simulate the whole desalination process. Recovery ratio, specific electric consumption and specific thermal consumption were compared with the ones obtained in a previous work, showing that a detailed characterization of the thermo-physical properties is required to get accurate and realistic predictions of the system performance.

On isobaric heat capacity of ionanofluids with carbon nanotubes – An experimental study

Ionanofluids (INFs) are defined as ionic liquids (ILs) with therein dispersed nanoparticles. The addition of nanoparticles results in an increase in the thermal conductivity of INFs. In terms of specific isobaric heat capacity (cp) this influence is not yet clear due to contradictory results published up to date. In this work, we assessed the influence of carbon nanotubes (CNTs) on the cp of INFs by means of DSC. We selected 13 different types of ILs and two mixtures of them as the base for INFs. 9 different types of CNTs were chosen: (singlewalled carbon nanotubes) SWCNTs, helical CNTs, Nanocyl multiwalled carbon nanotubes (MWCNTs) and in-house 16h MWCNTs, MWCNTs functionalized with carboxylic groups (COOH), hydroxylic groups (OH), C18n-alkyl chain or polyethylene glycol (PEG). Functionalized MWCNTs have never been investigated in terms of the cp of INFs. A total of 43 INFs were obtained and studied. The influence of CNTs on the cp of INFs was critically analyzed with consideration to the cp of base liquid and its agreement with data available in the literature, and with consideration to measurement uncertainty. Also, the cp of some pristine CNTs (as a bulk material), namely Nanocyl MWCNTs and in-house 16h MWCNTs, was examined. In the most of systems, the addition of CNTs did not affect the cp of INFs. In the others, the effects were minor and not greater than 3.1 %. In the end, the model proposed to estimate the cp of nanofluid, including the existence of nanolayer of IL on the CNT, was critically examined.

Experimental observation of mesoscopic fluctuations to identify origin of thermodynamic anomalies of ambient liquid water

We report a new experimental approach for observing mesoscopic fluctuations underlying the thermodynamic anomalies of ambient liquid water. In this approach, two sound velocity measurements with different frequencies, namely inelastic X-ray scattering (IXS) in THz band and ultrasonic (US) in MHz band, are required to investigate the relaxation phenomenon with the characteristic frequency between the two aforementioned frequencies. We performed IXS measurements to obtain the IXS sound velocity of liquid water from the ambient conditions to the supercritical region of liquid-gas phase transition (LGT) and compared the results with the US sound velocity in the literature. We found that the ratio of the two sound velocities, Sf, which corresponds to the relaxation intensity, exhibits a simple but significant change. Two distinct rises were observed in the high-temperature and low-temperature regions, implying that two relaxation phenomena exist: in the high-temperature region, a peak was observed near the LGT critical ridge line, which was linked with changes in the density fluctuation and isochoric and isobaric specific heat capacities; in the low-temperature region, Sf increased toward the low-temperature region, which was linked with the change in the isochoric heat capacity. We concluded that these two relaxation phenomena are originated from critical fluctuations of liquid-gas phase transition (LGT) and liquid-liquid phase transition, respectively. The linkage between Sf and isochoric heat capacity in the low-temperature region proves that the relaxation is the cause of the well-known heat capacity anomaly of ambient liquid water. In this study, both LGT and LLT critical fluctuations were observed, and the relationship between thermodynamics and the critical fluctuations was comprehensively discussed.

Thermophysical characterization on water and ethylene glycol/water-based MgO and ZnO nanofluids at elevated temperatures: An experimental investigation

In the current work, the main objective is to investigate the dynamic viscosity, thermal conductivity and isobaric specific heat capacity of MgO and ZnO nanoparticles that are dispersed in water and mixtures of ethylene glycol and water (EG/W). The measurements were carried out with various volumetric fractions (0.25 to 1%) and temperatures varied from 40 to 120 °C. According to the experimental results, the viscosity and thermal conductivity of the investigated nanofluids rise uniformly with increasing the nanoparticle concentration. The maximum viscosity augmentation for 1% MgO-(50:50)EG/W nanofluid is 34.5%, while the maximum augmentation for 1% ZnO-(50:50)EG/W nanofluid is 45.1%. For MgO-EG/W nanofluids, the maximum percentage of thermal conductivity enhancement occurs at 1% nanoparticles fraction and is 33.1%; for 1% ZnO-EG/W, the maximum enhancement is 23%. Measurements revealed that the nanofluids’ isobaric specific heat decreases as the nanoparticles fraction and EG concentration ratio in the base fluid increase but augments as the temperature increases. New correlations for predicting nanofluids’ thermophysical characteristics were suggested depending on the current experimental results. A theoretical evaluation of heat transfer performance was carried out, and it was demonstrated that MgO and ZnO nanofluids have the potential to be used in heat transfer applications with laminar flow regimes. For the turbulent regime, it is preferable to utilize nanoparticles concentrations of <0.5% for ZnO nanofluids and ≤1% MgO nanofluids, respectively.

Prediction of speed of sound and specific heat capacity of ionic liquids using predictive SAFT-based equation of state

In this work, the predictive PC-SAFT EoS has been developed to predict the speed of sound, the isochoric and isobaric heat capacity of ionic liquids (ILs) over a wide range of pressures and temperatures. In this new methodology, the segment number and diameter of ILs have been estimated using the surface area and molecular volume of the UNIFAC model. The segment energy and association energy parameters have been obtained using an inverse relationship between dispersion/association energy and segment diameter. The results show that the predictive PC-SAFT model can predict the specific isochoric and isobaric heat capacity of ILs up to high pressure, accurately. In the case of the speed of sound, the model performance is acceptable by considering using no adjustable model parameters. To check the model capability, the new model results have been compared to the electrolyte PC-SAFT EoS.

A sound velocity method for determining isobaric specific heat capacity

AbstractIsobaric specific heat capacity (Cp) is an important parameter not only in physics but also for most materials. Its accurate measurement is particularly critical for performance evaluation of thermoelectric materials, but the experiments by differential scanning calorimetry (DSC) often lead to large uncertainties in the measurements, especially at elevated temperatures. In this study, we propose a simple method to determine Cp by measuring the sound velocity (υ) based on lattice vibration and expansion theory. The relative standard error of the υ is smaller than 1%, showing good accuracy and repeatability. The calculated Cp at elevated temperature (&gt;300 K) increases slightly with increasing temperature due to the lattice expansion, which is more reasonable than the Dulong–Petit value.image

Behavior of Isobaric Heat Capacity of trans-1,1,1,4,4,4-Hexafluoro-2-butene in the Gas Phase

The isobaric specific heat capacity cp of trans-1,1,1,4,4,4-hexafluoro-2-butene was carefully measured for temperatures T ranging from (308 to 363) K and at pressures p ranging from (0.2 to 1.0) MPa in the gaseous state. The obtained 33 cp data with a flow calorimeter were tabulated and were shown in the cp–T diagram. It is estimated that the expanded uncertainties (k = 2) of the temperature measurements U(T) and the pressure measurements U(p) are less than 37 mK and 3.6 kPa, respectively. That for cp measurements U (cp) is derived to be less than 36 J·kg–1·K–1. Based on the evaluated data, corresponding isotherms were depicted in the cp–p diagram, and the ideal-gas isobaric heat capacity and saturation in the gas phase of trans-1,1,1,4,4,4-hexafluoro-2-butene were determined.

Heat capacity measurements of conventional aviation fuels

Isobaric specific heat capacities were measured for six conventional petroleum-derived aviation fuel samples: JP-10, JP-7, JP-4, JP-TS, TS-1, and Avgas. All measurements were made using modulated differential scanning calorimetry over the combined temperature range of (213 to 442) K. Experimental data, including an assessment of the associated expanded uncertainties, have been reported. Additionally, measurement results for the six fuels were compared with one another and with available literature data and existing surrogate mixture models.

Analytical expressions for thermophysical properties of solid and liquid beryllium relevant for fusion applications

The status of the literature is reviewed for thermophysical properties of pure polycrystalline solid and liquid beryllium which constitute input for the modeling of intense plasma–surface interaction phenomena that are important for fusion applications (thermal analysis, vapor shielding, melt motion, arcing, dust generation, dust transport). Reliable experimental data are analyzed for the latent heats, specific isobaric heat capacity, electrical resistivity, thermal conductivity, mass density, vapor pressure, work function, total hemispherical emissivity and absolute thermoelectric power from the room temperature up to the normal boiling point of beryllium as well as for the surface tension and the dynamic viscosity across the liquid state. Analytical expressions are recommended for the temperature dependence of these thermophysical properties, which involve high temperature extrapolations given the absence of extended liquid beryllium measurements.

Prediction of thermal properties of phosphorus dimer – The analytical approach

In this study, modified hyperbolical-type oscillator was used to simulate the internal vibration of a diatomic molecule. By employing the expression of partition function of the system, new analytical equations for the prediction of molar entropy, enthalpy, Gibbs free energy, and isobaric specific heat capacity were derived. The thermodynamic equations were applied to ground-state phosphorus dimer. Average absolute deviations of 0.3795, 0.8939, 0.3895, and 0.6978% were obtained. The results are in good agreement with existing data on gaseous phosphorus molecules in the literature.

Measurements of isobaric specific heat capacity (cp) for pure trans-1,3,3,3-tetrafluoropropene and (trans-1,3,3,3-Tetrafluoropropene + 1,1,1,2-tetrafluoroethane) binary mixtures at temperatures from (231.84 to 338.68) K and pressures up to 8.2 MPa

Due to the increasingly serious greenhouse effect, R134a with high global warming potential (GWP) will be phased out gradually. Pure trans-1,3,3,3-Tetrafluoropropene (R1234ze(E)) and (R1234ze(E) + 1,1,1,2-tetrafluoroethane (R134a)) mixtures have become one of the most potential alternative refrigerants owing to lower GWP. The isobaric specific heat capacity (cp) is one of the most important thermophysical properties for the design of heat exchangers and the verification of the accuracy of the equation of state (EoS). In this paper, the cp of pure R1234ze(E) and (R1234ze(E) + R134a) mixtures at temperatures from (231.84 to 338.68) K was measured by a self-design flow calorimeter, and the pressures up to 8.2 MPa. A total of 160 liquid cp data are reported, including 57 data points for pure substance and 103 data points for mixtures. Uncertainties for temperature, pressure and cp were estimated to be less than 11 mK, 0.02 MPa and 1.0 %. In addition, the experimental data were compared with the pieces of literature data and the predictions of three models (Helmholtz energy EoS, Peng-Robinson (PR) EoS and corresponding states equation (CSE)). Among the three models, the Helmholtz energy EoS gives the best description, while the prediction performance of the PR EoS is the worst, especially in the low-temperature region and the near-critical region. Then, a brief investigation was performed to understand the reasons behind these discrepancies and found that the specific volume data have a significant impact on the cp prediction for PR EoS. When using the high-precision specific volume data in the cp calculation, the prediction performance of PR EoS will be significantly improved.

Density, Viscosity, Refractive Index, Isobaric Specific Heat Capacity, Ultrasonic Velocity, Molar Volume, Isentropic Compressibility, Isothermal Compressibility, and Heat Capacity Ratio for Binary Mixtures of the Organic Liquids Ethylbenzene, Ethylcyclohexane, Pentylbenzene, and Pentylcyclohexane at 298.15 K and 0.1 MPa

Density, Viscosity, Refractive Index, Isobaric Specific Heat Capacity, Ultrasonic Velocity, Molar Volume, Isentropic Compressibility, Isothermal Compressibility, and Heat Capacity Ratio for Binary Mixtures of the Organic Liquids Ethylbenzene, Ethylcyclohexane, Pentylbenzene, and Pentylcyclohexane at 298.15 K and 0.1 MPa

Effect of Silicon Fullerenes on Changes in the Heat Capacity of Nacl Electrolytes

The paper presents the results of an experimental study of the isobaric heat capacity of solutions of electrolytes of the water and NaCl system in the temperature range 288-373K. To measure the heat capacity of electrolytes, the method of monotonous heating was used (developed by Professor M.M.Safarov). The total relative error of measuring the heat capacity of this place with a confidence probability of 95% is on average equal to 3.8%. It is established that the specific isobaric heat capacity of electrolytes decreases with increasing temperature and concentration of sodium chlorine. The addition of fullerene leads to an increase in the heat capacity of solutions of the water and sodium chlorine system. On the basis of experimental data and the law of thermodynamic similarity, approximation dependences were obtained. Using the expressions obtained, it is possible to calculate the heat capacities of electrolytes at different temperatures and concentrations of fullerene nanoparticles.

A new empirical model and neural network-based approach for evaluation of isobaric heat capacity of natural gas

Isobaric heat capacity of natural gas is of prominent thermophysical property as it is directly related to thermodynamic energy functions, thereby its trustworthy prediction can open a new window for better establishment of the basis for its theoretical and engineering studies. In the present study, a new accurate and simple empirical correlation as a function of specific gravity (γg), temperature (T), and pressure (P) was developed to rapidly estimate the isobaric specific heat capacity (Cp) of natural gas without using gas composition. Due to the limitations of proposed experimental models and relations derived from gas compressibility factor (Z-factor) equations in the literature to a certain temperature, pressure and specific gravity range, an artificial neural network (ANN) based on back-propagation method was also applied for reliable prediction of Cp of natural gas. 847 sets of data from a diverse range of T, P, and γg were used to develop the neural network architecture and topology. Moreover, Genetic algorithm (GA) and Particle swarm (PS) optimization as population-based stochastic search algorithms were also utilized to optimize the weights and biases of networks to establish the best combination of input variables leading to the minimum Cp. The ANN demonstrated an accurate and promising prediction with a correlation coefficient of 0.99691 and 0.99518 for total dataset and test data, respectively.

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.