Isochoric Specific Heat Capacity Research Articles

Surface water in C-S-H: Effect of the temperature on (de)sorption

Thermal desorption is a critical process in cement-based materials subjected to temperature increase. C-S-H surface is the most likely surface available for thermal desorption in these materials. Here, we investigate surface thermal desorption in C-S-H. Molecular simulations are used to get systems equilibrated under two drained poromechanical conditions: liquid water-saturated and constant partial fluid pressure conditions. Suited fluctuation formulas are deployed to acquire properties at the adsorbed layer level. We show that thermal desorption is driven by thermal expansion of water and liquid-to-vapor phase transition (leading to cavitation). The potential energy, isochoric specific heat capacity, molar incremental enthalpy, bulk modulus, coefficient of thermal expansion, surface tension, and pressure tensor components exhibit a marked dependence on the distance from the C-S-H adsorbing surface. Parameters usually adopted in sorption models (e.g., BET family) such as monolayer thickness and adsorption energy need to be revisited using molecular scale evidence.

Density and isochoric heat capacity of {x trans-1,3,3,3-Tetrafluoropropene + (1-x) Propane} at temperatures from (285.45 to 349.71) K and pressures up to 10.384 MPa

The increasingly serious global warming problem has accelerated the elimination of traditional hydrofluorocarbon (HFC) refrigerants. R1234ze(E) + R290 binary mixture as a potential alternative refrigerant are expected to overcome the deficiencies of R1234ze(E) (low volumetric refrigeration capacity) and R290 (flammability and explosiveness). In this paper, the 38 density and 119 isochoric specific heat capacity data of R1234ze(E)+R290 mixtures were measured at temperatures from (285.45 to 349.71) K using an adiabatic batch calorimeter with intermittent heating. Uncertainties of temperature, pressure, density and isochoric heat capacity were estimated to be less than 12 mK, 5 kPa, 0.30% and 1.0%. The density data were correlated using the Tait equation, and good regression results were obtained, with the AARD of 0.19% and MARD of 0.83%. A comparison was conducted between the Tait equation and REFPROP 10 and Peng-Robinson equation of state (PR EoS), the Tait equation gives the best prediction performance. In addition, the isochoric specific heat capacity data were compared with the values calculated by four models (PR model, Zhong model, Sheng model and REFPROP 10). Among them, the three models, the Zhong model, Sheng model and REFPROP 10, give the same prediction performance, with AARD of 2.88%, 2.47% and 2.51%, respectively. But for the PR model, the density data has a significant impact on the result, especially for the low-temperature region. When the density data were calculated by the Tait equation, the PR model presents the best prediction performance for the heat capacity of R1234ze(E) + R290 mixtures with the AARD of 2.00%, nevertheless, when the density data were calculated from the PR EoS, the PR model showed a large deviation in the prediction of isochoric heat capacity with the AARD and MARD of 3.74% and 11.11%. An empirical equation was correlated to represent the experimental heat capacity data with the MARD of 3.07% and the AARD of 1.15%.

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.

Measurements of isochoric specific heat capacity for 3,3,3-trifluoroprop-1-ene (R1243zf) at temperatures from (250 to 300) K and pressures up to 10 MPa

In this paper, a total of 86 isochoric specific heat capacity (cv) data of 3,3,3-trifluoroprop-1-ene (R1243zf) at temperatures from (250 to 300) K and pressures up to 10 MPa were measured using an adiabatic batch calorimeter. The standard uncertainties of temperature, pressure and isochoric specific heat capacity were estimated to be 12 mK, 5 kPa and 0.95%, respectively. A comparison was conducted between the experimental cv data and values calculated by three equations including the Helmholtz energy EOS (Akasaka and Lemmon, 2019) in REFPROP 10.0, the generalized equation (Zhong et al., 2019) and the corresponding states equation (Sheng et al., 2020) with the average absolute relative deviations (AARDs) of 2.43%, 0.91% and 0.84%, respectively. Among three equations, the corresponding states equation developed by Sheng et al. gives the best predictive performance for the liquid heat capacity of R1243zf.

The isochoric special heat capacity for 3,3,3-trifluoroprop-1-ene (R1243zf) at temperatures from (299 to 351) K and pressures up to 11 MPa

In this paper, isochoric specific heat capacity (cv) of 3,3,3-trifluoroprop-1-ene (R1243zf) in compressed liquid states were measured using an adiabatic batch calorimeter with intermittent heating. A total of 64 isochoric specific heat capacity data points over temperatures from (299 to 351) K and pressures up to 11 MPa was obtained for liquid R1243zf. The standard uncertainties were estimated to be 12 mK for temperature, 5 kPa for pressure, 0.20% for density and 0.87% for isochoric specific heat capacity. The experimental heat capacity data show good agreements with a Helmholtz equation of states (EOS) from Ref. [2], and the average absolute relative deviation (AARD) is 2.42%. A comparison of the present cv data with values calculated by the generalized equation of Zhong et al. (2019) [3] was carried out as well, and the results show good agreements and the deviations vary from −0.98% to 3.62% and the average absolute relative deviation (AARD) is 0.89%. Compared with the Helmholtz EOS, the generalized equation gives a better description for the data in this work.

Uncertainty estimation of the mean specific heat capacity for the major gases contained in biogas

The paper is focused on the uncertainty estimation of the mean isobaric and isochoric specific heat capacity calculation. The differences in the data among the individual sources for the technical calculation are presented in the first part of the paper. These differences are discussed in this paper. Research of scientific work with listed values of measurement uncertainties has been carried out in the second part of the paper. Furthermore, mathematical models were calculated which describe the dependence of the specific heat capacities and temperature. The maximal error models were carried out. Two approaches were used for the calculation of the mean specific heat capacity. The first approach is the calculation with help of integration of the function which describes the dependence of the specific heat capacity and temperature. The second approach is the calculation of a simple arithmetic mean of the specific heat capacity related to the maximal and minimal value of the temperature interval. The conclusion of the work shows that the time-effective second way is applicable in the case of a narrow temperature range. A value of 5.5% (Δ<sub>t</sub> = 200 K) was reached for the relative uncertainty. This is a similar value to that in the case of using the first way.

Measurements of pρTx and specific heat capacity c for (R290 + R1243zf) binary mixtures at temperatures from (292 to 350) K and pressures up to 11 MPa

Abstract In this paper, isochoric pρTx and specific heat capacity (cv) for (R290 + R1243zf) binary mixtures were measured using an adiabatic batch calorimeter with intermittent heating. A total of 57 pρTx data points over temperatures from (292 to 350) K and 82 isochoric specific heat capacity data points over temperatures from (299 to 350) K were obtained for liquid with mole fractions of R290 at (0.788, 0.606, 0.435 and 0.170). The standard uncertainties were estimated to be 12 mK for temperature, 5 kPa for pressure, 0.30% for density and 0.96% for isochoric specific heat capacity. The experimental density and heat capacity data agree well with the Helmholtz equation of state (EOS) developed by Bell and Lemmon (2016), and the average absolute relative deviation (AARD) are 0.27% and 1.01%, respectively. Comparisons of the present cv data with values calculated by the generalized equation developed by Zhong et al. (2019a) was carried out as well, and the results show good agreements with deviations varying from −3.00% to 3.16% and the average absolute relative deviation (AARD) of 0.91%.

First-principles study on the mechanical, vibrational and thermodynamic characteristics of intermetallic compound Ni2Ta

The mechanical, vibrational and thermodynamic characteristics of Ni2Ta were systematically investigated by means of density functional theory. The fully relaxed structure parameters were agreed well with the available experimental measured datas and published theoretical results. The single crystal elastic constants， polycrystalline modulus, Possion's ratio σ and Vickers hardness Hv were obtained. The anisotropic characters were studied by plotting the 3D surface contour of shear modulus and Young's modulus. Using the finite displacement method, the phonon dispersion curves and the phonon density of states were reported for the first time. The infrared-active and Raman phonon modes at the Г point were assigned and discussed. Finally, the thermodynamic characteristics such as isochoric specific heat capacities Cv and Debye temperature θD were predicted by the phonon density of states. Based on these exceptional properties, it was expected that Ni2Ta could be a promising intermetallic compound with high temperature and corrosion resistant performance.

The isochoric specific heat capacity for R1234ze(E) at temperatures from (237 to 349) K and pressures up to 9.2 MPa

In this work, the isochoric specific heat capacity (cv) of trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) in the compressed liquid states were measured using an adiabatic batch calorimeter. The temperatures ranged from (237 to 349) K and pressures up to 9.2 MPa. Measurements were obtained for a total of 112 state conditions on 22 pseudo-isochores. The standard uncertainties of temperatures, pressures and isochoric specific heat capacities were estimated to be 12 mK, 5 kPa and 0.98%, respectively. The experimental cv values for R1234ze(E) are compared with three equations, including two Helmholtz equations of state (EOSs) and a generalized equation based on corresponding state principle. The data in this work show good agreement, and the average absolute relative deviations are 1.37%, 1.27% and 1.59% for the above three equations, respectively.

A simple generalized equation for compressed liquid isochoric heat capacity of pure and mixture refrigerants

This work aims to develop a generalized equation for compressed liquid isochoric specific heat capacity (cv). The form of the equation was proposed based on the isochoric specific heat capacity calculation equation derived by the Peng-Robinson equation of state. The generalized coefficients were determined by 1734 liquid experimental cv data from 17 refrigerants. With known critical point, acentric factor and idea gas isochoric specific heat capacity, the developed equation can represent the liquid cv of 17 refrigerants well with the average absolute relative deviation of 1.55%. Large deviations are most likely to appear near the critical point. Comparisons were made to the calculation deviations from the Peng-Robinson equation of state and the multiproperty equations in REFPROP 9.1 software. It indicates that the developed equation provide a simple and reliable method for the calculation of the liquid cv. Additionally, 9 mixture refrigerants were calculated by the proposed generalized equation with the average absolute relative deviation of 3.13%.

A Simple Method of Finding New Dry and Isentropic Working Fluids for Organic Rankine Cycle

One of the most crucial challenges of sustainable development is the use of low-temperature heat sources (60–200 °C), such as thermal solar, geothermal, biomass, or waste heat, for electricity production. Since conventional water-based thermodynamic cycles are not suitable in this temperature range or at least operate with very low efficiency, other working fluids need to be applied. Organic Rankine Cycle (ORC) uses organic working fluids, which results in higher thermal efficiency for low-temperature heat sources. Traditionally, new working fluids are found using a trial-and-error procedure through experience among chemically similar materials. This approach, however, carries a high risk of excluding the ideal working fluid. Therefore, a new method and a simple rule of thumb—based on a correlation related to molar isochoric specific heat capacity of saturated vapor states—were developed. With the application of this thumb rule, novel isentropic and dry working fluids can be found applicable for given low-temperature heat sources. Additionally, the importance of molar quantities—usually ignored by energy engineers—was demonstrated.

Thermodynamic properties of (R1234yf + R290): Isochoric pρTx and specific heat capacity cv measurements and an equation of state

In this paper, isochoric pρTx and specific heat capacity cv for (R1234yf + R290) binary mixtures were measured using an adiabatic batch calorimeter with intermittent heating. A total of 42 pρTx data points over temperatures from (254.28 to 348.30) K and 89 isochoric specific heat capacity data points over temperatures from (255.48 to 347.55) K were obtained for liquid (R1234yf + R290) with mole fractions of R1234yf at (0.825, 0.607, 0.521 and 0.285). The standard uncertainties were estimated to be 10 mK for temperature, 5 kPa for pressure, 0.3% for density and 1.0% for isochoric specific heat capacity. The experimental pρTx data were correlated by an empirical Tait equation with average absolute relative deviation of 0.19%. A Helmholtz energy equation of state based on the multi-fluid approximations model was developed for (R1234yf + R290) using the present and available experimental data. Eleven mixture rules are employed and the optimal Helmholtz energy equation of state calculates the density, VLE and isochoric specific heat capacity properties with sufficient accuracy. The compressed liquid density and isochoric specific heat capacity data in this work are well represented with average absolute relative deviation of 0.21% and 0.66%, respectively.

Adiabatic calorimeter for isochoric specific heat capacity measurements and experimental data of compressed liquid R1234yf

In this paper, an adiabatic calorimeter has been developed to measure the isochoric specific heat capacity of compressed liquid. A spherical bomb with platinum resistance thermometer inserted was used to hold the measured liquid and two adiabatic shields were arranged to reduce the heat loss of thermal radiation. The isochoric specific heat capacity of liquid propane was measured over temperatures from (236 to 340) K and pressures up to 14 MPa. Satisfactory agreement with published heat capacity data is found and the reliability of the experimental setup is verified. Moreover, the experimental isochoric specific heat capacity data of liquid R1234yf were obtained in the temperatures from (240 to 341) K and pressures up to 13 MPa. The standard uncertainties were estimated to be 10 mK for temperature, 5 kPa for pressure and 1.0% for isochoric specific heat capacity. The data of R1234yf are represented by two Helmholtz equations of state with average absolute relative deviations of 2.0% and 1.3%, respectively. Comparisons are made between the Helmholtz equations of state and the cubic equations of state for the calculation of the specific heat capacity property. The Helmholtz equations of state give a better description than the cubic equations of state, and the Peng–Robinson equation of state performs slightly better than the Patel–Teja and Soave–Redlich–Kwong equations of state.

Coefficients for the calculation of thermophysical properties of indolene/ethanol biofuels for transcritical engine simulations

Driven by fuel economy and emission control concerns, modern automotive internal combustion engines operate at increasingly higher pressures and temperatures. The development of new low emission advanced combustion concepts rely on accurate predictions of the fuel mixture formation and combustion, sometimes near or across the critical point of the fuel blend. The present work provides libraries of thermodynamic and transport properties of automotive certification fuel surrogate, indolene, and its mixtures with ethanol E5, E10, E15, E20, E25, E50 and E85, to be used in the subcritical and supercritical range, in order to make transcritical fuel predictions possible and accurate.Values of enthalpy, latent heat of vaporisation, isobaric and isochoric specific heat capacity, entropy, surface tension, thermal conductivity, density, vapour pressure and viscosity are obtained numerically through theoretical and semi-empirical correlations and given for all the specified mixtures in the form of polynomial functions of temperature. The synthesis of the coefficients was obtained by minimising the least-squares-errors through a 5th order polynomial regression fit method. This format is particularly convenient for implementing computer equations or for use in CFD numerical codes.

Effect of temperature on thermal properties of monolayer MoS2 sheet

Influences of temperature on thermal properties of monolayer MoS2 were investigated using first-principles calculations based on the density-functional perturbation theory. The calculated equilibrium vibration properties and Grüneisen parameters γ of monolayer MoS2 are in good agreement with the available experimental and theoretical values. Interestingly, γ of acoustic modes show an evidently asymmetric character due to the sandwiched structure of monolayer MoS2 while γ of optical modes display an approximate symmetry in the first Brillouin zone. Thermal properties analysis shows that temperature has a great effect on Debye temperature θD, isochoric specific heat capacity CV, relaxations time τ, mean free path l, and thermal conductivity κ of monolayer MoS2. With the increasing temperature, θD and CV increase rapidly and then reach saturation, whereas τ and l decrease sharply and then become moderate. The saturation value of θD and CV of monolayer MoS2 is 603K and 17.6cal/cellK, respectively. The κ of monolayer MoS2 illustrates the expected T−1 dependence in the range from 47 to 603K, and it is dominated by longitudinal acoustic (LA) mode which has the maximum value of τ and l. At room temperature, the calculated κ of monolayer MoS2 of 29.2Wm−1K−1 is higher than 1.35Wm−1K−1 that was obtained by Molecular dynamics, but it is in agreement with the experimental value of 34.5±4Wm−1K−1.

Isochoric Specific Heat Capacity of trans-1,3,3,3-Tetrafluoropropene (HFO-1234ze(E)) and the HFO-1234ze(E) + CO2 Mixture in the Liquid Phase

The isochoric specific heat capacity (cV) of trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) and mole fraction x = 0.489 HFO-1234ze(E) + (1 − x) = 0.511 CO2 in the liquid phase were measured with a twin-cell type adiabatic calorimeter. The sample purity of HFO-1234ze(E) and CO2 was certified to have a minimum purity of 0.9996 mole fraction and 0.99999 mole fraction respectively by gas chromatographic analysis. The measurements were obtained for temperatures ranging from (270 to 425) K and at pressures up to 30 MPa. Temperatures were measured with a platinum resistance thermometer on the bottom of each cell and were reported based on the International Temperature Scale of 1990 (ITS-90). Sample pressures were measured with a quartz crystal transducer. Densities were calculated from the volume of the calorimeter cell and the sample mass. The expanded uncertainty (with a coverage factor k = 2) of temperature measurements is 13 mK and 8 kPa for pressure measurements. The expanded relative uncertainty of density is 0.16 %. As a result, the experimental expanded relative uncertainty of the isochoric specific heat capacity (cV) is estimated to be from 3.8 % to 4.6 % in the liquid phase. The cV measurements were almost the same as the values calculated from the proposed equations of state except near the critical isochore.

Study on Isochoric Specific Heat Capacity of Liquid R-410A and HFE-347pcf2

The isochoric heat capacity (cv) of R-410A [a mixture of 49.81 mass% difluoromethane (HFC-32) + 50.19 mass% pentafluoroethane (HFC-125)] and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethylether (HFE-347pcf2) was measured at temperatures from 277 K to 400 K and at pressures up to 30 MPa. The reported density measurements for R-410A and HFE-347pcf2 are in the single-phase region and cover a density range above 0.92 g·cm−3 and 1.33 g·cm−3, respectively. The measured data of R-410A are compared with data reported by other researchers. Also, the measured data of R-410A are examined with an available equation of state. As a result, it is found that the present cv data for R-410A agree well with those by other researchers and the calculated values with the equation of state in the measurement range except near the critical isochore.

P– H and T– S diagrams of 3He from 0.2 K to 20 K

Based on the collected experimental and smoothed p– ρ– T data, isochoric and isobaric specific heat capacity data, etc., p– H and T– S diagrams of 3He are plotted in the range of temperatures from 0.2 K to 20 K and pressures from 0.0001 MPa to 20 MPa, with data calculated numerically instead of using an equation of state.

Deuterium isotope differences in 2-propanone, (CH 3) 2CO/(CD 3) 2CO: a high-pressure sound-speed, density, and heat capacities study

A new high-pressure, non-intrusive ultrasonic microcell [J. Chem. Thermodyn. 36 (2004) 211–222] was used to carry out sound-speed measurements in deuteriated 2-propanone (acetone-d 6) in broad ranges of temperature (288 < T/K < 338) and pressure (0.1 < p/MPa < 160). To the best of our knowledge, there are no data regarding speed of sound of acetone-d 6. ( p, ρ, T) data for acetone-d 6 were also determined but in a narrower T, p range (298 to 333 K; 0.1 to 60 MPa). In this interval, several thermodynamic properties were thus determined, such as: isentropic ( κ s) and isothermal ( κ T) compressibility, isobaric thermal expansivity ( α p), isobaric ( c p) and isochoric ( c v) specific heat capacity, and the thermal pressure coefficient ( γ v). Comparisons with our data for acetone-h 6 enabled us to establish the magnitude and sign of deuterium isotope effects for identical properties. These effects are a consequence of distinct vibrational mode frequencies in an isotope-invariant force constants’ field. Molar heat capacities and their isotope effects were theoretically determined by employing an Einstein-like model for the vibrational frequencies of acetone-h 6 and acetone-d 6.

A novel non-intrusive microcell for sound-speed measurements in liquids. Speed of sound and thermodynamic properties of 2-propanone at pressures up to 160 MPa

A novel high-pressure, ultrasonic cell of extremely reduced internal dimensions (∼0.8 · 10 −6 m 3) and good precision for the determination of the speed of propagation of sound in liquids was conceived and built. It makes use of a non-intrusive methodology where the ultrasonic transducers are not in direct contact with the liquid sample under investigation. The new cell was used to carry out speed of sound measurements in 2-propanone (acetone) in broad ranges of temperature (265< T/K<340) and pressure (0.1< p/MPa<160). ( p, ρ, T) data for acetone were also determined but in a narrower T, p range (298 to 333 K; 0.1 to 60 MPa). In this interval, several thermodynamic properties were thus calculated, such as: isentropic ( κ s) and isothermal ( κ T) compressibility, isobaric thermal expansivity ( α p), isobaric ( c p) and isochoric ( c v) specific heat capacity, and the thermal pressure coefficient ( γ v). Comparisons with values found in the literature generally show good agreement.