High-temperature Adiabatic Calorimeter Research Articles

Automated experimental facility to investigate a complex of thermophysical properties of liquids and gases

The process of investigation of a complex of liquid and gas thermophysical properties (heat capacity, PVT) by means of the Kh.I. Amirkhanov’s high-temperature adiabatic calorimeter is described. The technique of automation of that experimental facility by means of measuring and controlling devices and a personal computer is described as well.

Experimental investigation of the isochoric heat capacity of the n-heptane–water binary system

On an automated experimental facility established on the basis of a high-temperature adiabatic calorimeter, we investigate the temperature dependence of the isochoric heat capacity of the n-heptane–water binary immiscible system containing 0.147 molar fraction of water, within the density range of 146.0–469.6 kg/m3 and the temperature range of 428.15–553.15 K, including the phase transition domain.

Isochoric heat capacity of an n-hexane + water system

The isochoric heat capacity of an n-hexane + water system at water contents of 0.121, 0.166, 0.2, 0.234, 0.256, and 0.3 mole fraction is studied along different isochors at different temperatures in the 140 to 550 kg/m3 range of densities using a high-temperature adiabatic calorimeter designed at the Amirkhanov Institute of Physics. The tabulated values of isochoric heat capacity Cv, x are presented for an H2O concentration of 0.3 mole fraction. The curves of liquid-liquid and liquid-gas phase equilibria are constructed.

Definition of parameters phase equilibria and identification of phases of system hydrocarbon

A new calorimetric method and the results of determination of binary systems phase equilibria having a region of phase stratification on the basis of calorimetric measurements are described in this paper. Isochoric heat capacity temperature dependence of binary system of hydrocarbon-water has been studied by the method of high-temperature adiabatic calorimeter. Parameters of the phase stratification region have been determined on the basis of revealed peculiarities of this dependence at phase transitions liquid-liquid and liquid-vapour and phase diagram have been made.

Azeotropic line determination from the caloric data on binary stratifying systems

The experimental isochoric heat capacity values of stratifying n-hexane-water mixtures of the compositions 0.120, 0.166, 0.200, and 0.256 H2O mole fractions were obtained using a high-temperature adiabatic calorimeter over the density ranges 244.74–498.25, 121.06–438.21, 252.02–500.00, and 208.11–398.88 kg/m3, respectively. The C V, x heat capacities were tabulated for the mixture with 0.120 H2O mole fractions. Liquid-liquid and liquid-gas phase equilibrium curves were plotted. The suggestion was made that the intersection point between these curves characterized the state of an azeotrope. The azeotropic line with the critical point at its end was constructed.

Isochoric heat capacity and coexistence curve of methyl alcohol in the neighborhood of the critical point

A high-temperature adiabatic calorimeter is used to experimentally measure the isochoric heat capacity Cυ of methyl alcohol in the temperature range from 474.39 to 531.63 K along 22 isochores which cover the density range from 136.1 to 750.1 kg/m3. The data on Cυ are used to determine the curve of liquid-vapor phase equilibrium for methyl alcohol. The thus obtained data are described by scaling equations. Comparison is made with results of other researchers.

Enthalpies of Oxidation of CaMnO3-δ, Ca2MnO4-δ and SrMnO3-δ Deduced Redox Properties

The enthalpies of oxidation of CaMnO3-δ, Ca2MnO4-δ, and SrMnO3-δ have been determined by in situ oxidation in a high-temperature adiabatic calorimeter. CaMnO3, Ca2MnO4, and SrMnO3 were synthesized by the EDTA precursor or the ceramic method, and partly reduced materials were prepared by topotactic reduction in diluted H2 (5−10%) at 290−355 °C. Unit cell dimensions and oxygen stoichiometry of partly reduced and reoxidized materials were determined by powder X-ray diffraction, thermogravimetry, and iodometric titration. The enthalpy of oxidation of SrMnO3-δ was considerably less exothermic than the corresponding value for CaMnO3-δ, and the enthalpy of oxidation of Ca2MnO4-δ was more exothermic than for CaMnO3-δ. The enthalpy of oxidation is discussed in terms of the basicity of oxides, the Goldschmidt tolerance factor, and the crystal structures of the oxidized and reduced materials. Finally, based on the enthalpy of oxidation, the oxygen defect chemistry of these materials is estimated using simple thermodynamic models. Using the measured enthalpy of oxidation and estimated entropy of oxidation, the measured oxygen nonstoichiometry is reproduced rather well. A free fit of the same models to the experimental data gives enthalpies of oxidation that are far more exothermic than the measured values. The present findings demonstrate that simple models based on point defect equilibrium may give significant errors in the enthalpy and entropy of formation of point defects, despite a good fit to the free energy.

The isochoric heat capacity of n-heptane–water mixtures

The isochoric heat capacity of mixtures of n-heptane+water with compositions of 3.0 wt.% and 11.50 wt.% of water is investigated in liquid–liquid–vapor, liquid–vapor and homogeneous states using high-temperature adiabatic calorimeter. The density of the azeotropic state was determined from the C V measurements.

High-Temperature Adiabatic Calorimeter for Constant-Volume Heat Capacity Measurements of Compressed Gases and Liquids.

A high-temperature adiabatic calorimeter has been developed to measure the constant-volume specific heat capacities (cV) of both gases and liquids, especially fluids of interest to emerging energy technologies. The chief design feature is its nearly identical twin bomb arrangement, which allows accurate measurement of energy differences without large corrections for energy losses due to thermal radiation fluxes. Operating conditions for the calorimeter cover a range of temperatures from 250 K to 700 K and at pressures up to 20 MPa. Performance tests were made with a sample of twice-distilled water. Heat capacities for water were measured from 300 K to 420 K at pressures to 20 MPa. The measured heat capacities differed from those calculated with an independently developed standard reference formulation with a root-mean-square fractional deviation of 0.48 %.

The experimental investigation of Cv, x, P, V, T properties and the equation of state of the n-hexane-water system

Experimental investigations of the C v, x , P, V, T properties in the n-hexane-water system with the different compositions ( x) 0.121, 0.200, 0.247, 0.256, 0.301, 0.345 and 0.615 molar fraction (m.f.) H 2O were made with a high-temperature adiabatic calorimeter. The mixtures with 0.256 and 0.615 m.f. H 2O were studied over the wide range of densities (ϱ) from 208.6 to 399.6 kg m −3 and from 191.4 to 416.7 kg m −3, respectively. For the description of some of the thermodynamic properties of the n-hexanewater binary system, the equation of state proposed by Jin et al. was used.

Measurements of the isochoric heat capacities C v of carbon dioxide in the critical region

We have measured the isochoric heat capacity C v of carbon dioxide in both the one-phase and two-phase regions near the critical point. Temperatures varied from 280 K to 355 K, and densities varied from 461.2 kg·m -3 to 519.2 kg·m -3. The measurements were performed in a high-temperature adiabatic calorimeter used earlier for the determination of the isochoric heat capacity of several liquids and liquid mixtures near the critical points. (1,2) The experiments were performed at eight isochores: (461.2, 464.5, 467.5, 470.1, 477.7, 499.0, 509.8, and 519.2) kg·m -3 in the neighbourhood of the critical point and the coexistence curve. Uncertainties of the heat-capacity measurements are estimated to be less than 1.2 per cent far from T c and 2.5 per cent in the immediate vicinity of the critical point. The uncertainty in temperature was less than ± 10 mK. Comparisons are made with values calculated from different scaling equation of state and with earlier measurements. The experimental results have been interpreted in terms of the modern theory of critical phenomena. The asymptotic and non-asymptotic critical behaviour of C v has been discussed. The critical exponents and critical amplitudes of C v along the critical isochore and Δ ρ on the coexistence curve are derived. We have analysed the two-phase massic heat capacities of carbon dioxide to obtain detailed information about the behaviour of (∂ 2 p /∂ T 2) and (∂ 2μ/∂ T 2) in the critical region.

Isochoric heat capacity and liquid‐gas coexistence curve of carbon dioxide in the region of the immediate vicinity of the critical point

AbstractThe paper contains the results of new experimental measurements of the isochoric heat capacity and the liquid‐gas coexistence curve of carbon dioxide in the one‐phase region near the critical point. The measurements were performed in a high temperature adiabatic calorimeter used earlier for the determination of the isochoric heat capacity of several liquids and liquid mixtures near the critical points [1, 2].The experiments have been performed at seven isochores, namely: 461.2, 464.5, 467.5, 470.1, 477.7, 499.0, and 509.8 kg·m−3 in the neighbourhood of the critical point and the coexistence curve. The measurements were made with samples of constant mass contained in a calorimeter vessel of nearly constant volume. Uncertainties of the heat‐capacity measurements are estimated to be less than 2 percent far from Tc and 3 percent in the immediate vicinity of the critical point. The uncertainty in temperature was less than ±10 mK.

Isochoric heat capacity of {xH2O + (1-x)KOH} near the critical point of pure water

The isochoric heat capacity of {xH2O + (1-x)KOH} has been measured with a high-temperature adiabatic calorimeter. The experiments have been performed at five mole fractions x, namely 0.99973, 0.99863, 0.99725, 0.99166, and 0.98595. For each mole fraction the measurements have been performed at two isochores, namely 315.5 kg·m-3 (critical isochore for pure water) and 250.0 kg·m-3. The experimental results were obtained along isochores. The Cv for the saturated liquid [xH2O + (1-x)KOH} was determined by using an extrapolation technique along each isochore fitting a simple polynomial by least squares. The total error of each experimental value of Cv is estimated to be about 0.5 per cent in the region far from the critical point, and (1.5 to 2.0) per cent in its vicinity. The uncertainly of the densities measured was estimated to be within 0.03 kg·m-3. The uncertainly in temperature was less than 10 mK.

A calorimetric study of intermediate phases in iron +, cobalt +, and nickel + molybdenum

Using a high-temperature adiabatic calorimeter, measurements have been made of the enthalpy of formation at 973 and 1573 K and the heat capacity in the range 773 to 1573 K for the phases ε-‘Fe 3Mo 2’, ε-‘Co 7Mo 6’, and δ-‘MoNi’ iron +, cobalt +, and nickel + molybdenum alloys, respectively. The results have been combined with thermodynamic values reported by other investigators to allow expressions for the standard Gibbs energy of formation of the phases to be determined.

Thermodynamic properties of α- and σ-phases in V + Fe and V + Cr + Fe

Some thermodynamic properties of α- and σ-phases in V + Fe and V + Cr + Fe have been measured with a high-temperature adiabatic calorimeter. The molar heat capacity has been determined between 1000 and 1650 K. The enthalpy of formation of α-V 0.48 Fe 0.52 at 1400 K is — (5640 ± 500) J mol −1 , and that of α-Cr 0.2 V 0.3 Fe 0.5 is — 1250 J mol −1 at the same temperature. The enthalpy of transformation for the σ to α change of the V + Fe alloy is (3230 ± 130) J mol −1 at (1443 ± 10) K, and that of the Cr + V + Fe alloy is (2300 ± 80) J mol −1 at (1360 ± 10) K. The calculated entropies of α- and σ-V 0.48 Fe 0.52 at 1600 K are 6.93 and 4.70 J K −1 mol −1 , respectively.

The Heats of Formation in the System Gold-Platinum-Palladium

Heats of formation, determined by means of a high-temperature adiabatic calorimeter, are reported for solid Pd-Pt, Au-Pd, and Au-Pd-Pt alloys. The results for these three alloy systems may be described, within the experimental error, by an equation proposed by Margules (S.B. Akad. Wiss. Wien Math. Naturwiss., Kl.II. 1895, 104, 1243), based on a single set of constants. This approach has been adopted to evaluate iso-enthalpy contours for the whole ternary system. Excess partial entropies of palladium in Pd-Pt alloys are presented, calculated from the present heat data using activity data taken from the literature.