JANAF Tables Research Articles

Reduced order design and investigation of intakes for high speed propulsion systems

Ramjet propulsion is commonly preferred to power supersonic and hypersonic vehicles for cruising faster than Mach 3. This is an elegant solution owing to the lean architecture which does not embody any rotating parts. Although the geometry of the engine is simple as compared to turbine based configurations, the flow physics through the engine duct is quite complex and the flow speeds modulate between the supersonic and subsonic regimes multiple times. The design and performance analysis of ramjet engines are vital to ensure that propulsion system can satisfy the flight trajectory requirements. Therefore, this study introduces a reduced order holistic approach for design and assessment of the flow development in high-speed propulsion systems composed of generic elements of ramjet/scramjet engine configurations. Accordingly, the intakes designed based on axisymmetric flow templates are used to provide the necessary freestream flow modulation prior to the isolator through which a normal shock assumption is applied. The resultant flow properties are utilized for the combustion module where the flow expansion within the combustor and nozzle components are computed based on 1D steady inviscid flow equations coupled with detailed chemistry approach and JANAF tables. The module was validated and verified with the experimental and numerical data obtained for a dual-mode ramjet/scramjet combustor. Consequently, the parameters such as thrust, fuel consumption and specific impulse are calculated to quantify the engine performance for each design. Finally, the employment of the low fidelity model is demonstrated over a family of ramjet flow paths where the design space is confined based on the requirements of a high-supersonic cruise vehicle.

Simulation and Modeling of Compression Stroke in Diesel Engines

The objective of this study is to simulate the compression stroke in diesel engines by using computational fluid dynamics (CFD), and to model the compression stroke by using thermodynamic equations for Ideal gases and polynomial function that fits thermodynamic data of JANAF tables. The most important parameters to be simulated and modeled during the compression stroke are temperature and pressure of cylinder gases because of their important effects on mixture formation inside the engine combustion chamber. The simulation part will be performed using ANSYS ICE software. The modeling part will be performed using a MATLAB program composed by the corresponding author. Simulation and modeling process will be carried out between the intake valve close (IVC) and top dead center (TDC), the results of simulation and modeling will be compared and discussed.

Use of JANAF Tables in Equilibrium Calculations and Partition Function Calculations for an Undergraduate Physical Chemistry Course

The usefulness of the JANAF tables is demonstrated with specific equilibrium calculations. An emphasis is placed on the nature of standard chemical potential calculations. Also, the use of the JANAF tables for calculating partition functions is examined. In the partition function calculations, the importance of the zero of energy is highlighted.

Analysis for the Syngas Composition of Gasifier

A simple and convenient model to analyze the composition of the syngas has been implemented. We collect thermodynamic properties data from JANAF tables and Turns’ book. By regression analysis the Gibb’s energy functions of temperature were got. Through these functions, the equilibrium constants as functions of temperature can be deduced for the related chemical reaction in gasification process. With the equilibrium constants, the model to calculate the equilibrium composition for pure carbon gasification has been established. The model was improved from considering only isothermal reaction to including reaction heat balance and then finally with fully energy balance consideration. Since the model has been implemented on general software Excel, it will be very easy for users to apply in further study. Finally, we show how precise the estimation could be by doing comparison with early study and utilize this tool to analyze the heat balance for a specific IGCC cogeneration power plant.

Selection of thermodynamic data for a novel carbothermic smelting process for aluminum

For the carbothermic production of aluminum, thermodynamic data are required for the condensed compounds and gas phase involved in the Al2O3-C or Al2O3-Al4C3 systems. The data for Al2O3(s, l), Al4C3(s), CO(g), C(s, g), Al(s, l, g), Al2O(g) and AlO(g) in different databases is in accord. For a novel carbothermic aluminum smelting process, currently in development, the published JANAF Thermochemical Tables were selected for calculations. However, the JANAF Tables do not include data for oxycarbides. Thus a literature review was conducted. Data from different sources was collated and found to be in accord for Al4O4C over the 1,600–2,200 K temperature range. These data, together with the data from JANAF Tables, agree very well with the experimental results obtained during the carbothermic process. However, a commercially available computational thermodynamic software package called HSC provides results which contradict the experimental results obtained, while its thermodynamics data is also significantly different from other data available in the literature.

Solubility Product for Lithium Metaborate in Acid Solutions to Extreme Temperatures and Pressures

A recently developed model for predicting the thermodynamic properties of electrolytes to high temperatures and pressures, the unified theory of electrolytes, is used to calculate the solubility product of lithium metaborate in acid solutions from 298.15 K to Tc. The results are compared with the available high temperature experimental data in the literature. This study also establishes a value of ΔfH○ (298.15 K,0.1 MPa) for LiBO2(cr) that is in good agreement with the JANAF tables value.

The gas phase hydrogen-bonded dimers of HOCl: A high-level quantum chemical study

The O···HO and Cl···HO hydrogen bonding interactions were analyzed for HOCl dimers by using B3LYP, MP2, CCSD, and MP4(SDTQ) methods in conjunction with the various basis sets. Five isomers were found for the HOCl dimer. The ZPE and BSSE corrected binding energies were computed at the different levels of theory. At the optimized geometries obtained at CCSD/AUG-cc-pVDZ level, energies were re-evaluated at MP4(SDTQ)/AUG-cc-pVTZ and CCSD(T)/cc-pVTZ levels of theory. We found an average of −20.9 and −9.6 kJ/mol for the strength of the O···H and Cl···H hydrogen bonding interactions, respectively. Excitation and vertical ionization energies as well as rotational constants were computed at different levels of theory. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis were used to elucidate the nature of the interactions of HOCl dimers. The interaction energies were decomposed by Morokuma methodology. We have computed ΔfH°(HOCl) and ΔfH°(HOCl+) using the atomization reactions. The ΔfH°298(HOCl) values are −17.85 and −18.05 kcal/mol by using CBS-Q and CBS-QB3 extrapolation models, respectively, in good agreement with the results given in JANAF tables. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

Investigation of thermodynamic properties of gaseous SiC(X [formula omitted] and a [formula omitted]) with accurate model chemistry calculations

Density functional theory, high-level model chemistry at G3(MP2), CBS-Q, G3//B3LYP, G3(QCI) and QCISD(T)/aug-cc-pv5z levels of theory combined with statistical thermodynamics have been employed to explore the thermodynamic properties of gaseous SiC(X 3 Π ) and SiC(a 1 Σ ). The heat capacities and entropies are obtained via statistical thermodynamics with the structure, vibrational frequency and the electronic excitations calculated at B3PW91/6-31G(d) and B3PW91/6-311G(d) levels. The importance of the anharmonic corrections and the electronic excitations is examined. The reliability of the electronic excitation energies calculated with the time dependent density functional method is tested. The heat capacities and entropies of the ground state SiC ( X 3 Π ) calculated in this work are consistent with other theoretical work but different from those in the JANAF Tables. The enthalpies of formation and the Gibbs free energies of formation are in excellent agreement with the calculated results from one experiment but are higher than another observation.

Accurate vibrational-rotational partition functions and standard-state free energy values for H2O2 from Monte Carlo path-integral calculations.

Accurate quantum mechanical partition functions and absolute free energies of H(2)O(2) are determined using a realistic potential energy surface [J. Koput, S. Carter, and N. C. Handy, J. Phys. Chem. A 102, 6325 (1998)] for temperatures ranging from 300 to 2,400 K by using Monte Carlo path integral calculations with new, efficient polyatomic importance sampling methods. The path centroids are sampled in Jacobi coordinates via a set of independent ziggurat schemes. The calculations employed enhanced-same-path extrapolation of trapezoidal Trotter Fourier path integrals, and the paths were constructed using fast Fourier sine transforms. Importance sampling was also used in Fourier coefficient space, and adaptively optimized stratified sampling was used in configuration space. The free energy values obtained from the path-integral calculations are compared to separable-mode approximations, to the Pitzer-Gwinn approximation, and to values in thermodynamic tables. Our calculations support the recently proposed revisions to the JANAF tables.

Determination of standard gibbs energies of formation of Cr2N and CrN

The standard Gibbs energies of formation of Cr2N and CrN have been measured by an equilibration technique and by using thermogravimetry and differential thermal analysis (TG-DTA) at temperatures ranging from 1232 to 1523 K. The results are expressed as follows: $$\begin{gathered} 2Cr(s) + \frac{1}{2}N_2 (g) = Cr_2 N(s) \hfill \\ \Delta G^ \circ = - 104,000( \pm 1300) + 47.7( \pm 5.9)T({J \mathord{\left/ {\vphantom {J {mol}}} \right. \kern-\nulldelimiterspace} {mol}}) (1362 to 1523 K) \hfill \\ Cr(s) + \frac{1}{2}N_2 (g) = CrN (s) \hfill \\ \Delta G^ \circ = - 117,000( \pm 1000) + 71.9( \pm 4.9) T({J \mathord{\left/ {\vphantom {J {mol}}} \right. \kern-\nulldelimiterspace} {mol}}) (1232 to 1354 K) \hfill \\ \end{gathered} $$ The standard Gibbs energies of formation of Cr2N and CrN determined by the present work are more negative than the values in the JANAF Tables by about 14 and 5 kJ/mol, respectively, in the measured temperature range.

Laminar Burning Velocity of Methane–Air–Diluent Mixtures

An experimental facility for measuring burning velocity has been designed and built. It consists of a spherical constant volume vessel equipped with a dynamic pressure transducer, ionization probes, thermocouple, and data acquisition system. The constant volume combustion vessel allows for the determination of the burning velocity over a wide range of temperatures and pressures from a single run. A new model has been developed to calculate the laminar burning velocity using the pressure data of the combustion process. The model solves conservation of mass and energy equations to determine the mass fraction of the burned gas as the combustion process proceeds. This new method allows for temperature gradients in the burned gas and the effects of flame stretch on burning velocity. Exact calculations of the burned gas properties are determined by using a chemical equilibrium code with gas properties from the JANAF Tables. Numerical differentiation of the mass fraction burned determines the rate of the mass fraction burned, from which the laminar burning velocity is calculated. Using this method, the laminar burning velocities of methane–air–diluent mixtures have been measured. A correlation has been developed for the range of pressures from 0.75 to 70 atm, unburned gas temperatures from 298 to 550 K, fuel/air equivalence ratios from 0.8 to 1.2, and diluent addition from 0 to 15 percent by volume.

A study of the formation of Ti(CN) solid solutions

The phase stability of Ti(CN) solid solutions was investigated based on the accurate first principles method, the Debye model and the rigid band model beyond a simple ideal mixing model. The Gibbs free energy of formation was calculated using the results from the above models and the standard state energies for the formation of pure TiC and TiN from JANAF tables at varying temperatures. The predicted phases for highest stability at 1700 and 2100 K are in the range of 0.6 and 0.3, whereas those obtained experimentally were near 0.7 and 0.4 nitrogen contents at 1700 and 2100 K, respectively. From the calculation results it can be safely concluded that Ti(CN) solid solutions have higher stability than that predicted by the ideal mixing model.

Energy requirements for ablation or decomposition of ceramics during CO2 and Nd:YAG laser machining

In order to assess a priori the outcome of a laser machining process using either simplistic ad hoc or sophisticated models, knowledge is needed of the energy required to remove a unit mass of material. Since laser–material interactions involve vaporization, decomposition, ejection of fragments, plasma initiation, expansion, etc., extrapolating enthalpy data from JANAF tables will result in significant uncertainty. In this article, an experimental setup to measure this “heat of removal” is described. The apparatus mainly consists of an integrating sphere for the sample and a second integrating sphere for reference. The specimen is mounted at the center of the sample sphere, and is heated by a CO2 or Nd:YAG laser, whose beam is split, with a part of the beam going into the reference sphere, to monitor the temporal laser power. The energy reflected by the specimen inside the sample sphere is recorded by a second detector. Combining these data, the total absorbed energy may be deduced. For this type of measurement, energy losses by convection and radiation are generally negligible, while conduction losses may be substantial. In order to minimize conduction losses, the specimens are manufactured to a thickness of less than 500 μm. Still, conduction losses may account for up to 10%–20% of the total laser energy for continuous wave and conventionally pulsed lasers even for such thin samples. Thus, a numerical model is also employed to estimate the conduction losses and to correct the measured value of the “heat of removal.” Experimental data have been obtained for CO2 and Nd:YAG laser irradiation on graphite, hot-pressed silicon nitride, and sintered α-silicon carbide.

Oxidation mechanism of Si3N4-bonded SiC ceramics by CO, CO2 and steam

This paper presents a theoretical and experimental investigation into the oxidation reactions of Si3N4-bonded SiC ceramics. Such ceramics which contain a small amount of silicon offer increased oxidation and wear resistance and are widely used as lining refractories in blast furnaces. The thermodynamics of oxidation reactions were studied using the JANAF tables. The weight gain was measured using a thermogravimetric analysis technique to study the kinetics. The temperature range of oxidation measurements is from 1073 to 1573 K and the oxidation atmosphere is water vapour, pure CO and CO–CO2 gas mixtures with various CO-to-CO2 ratios. Thermodynamic simulations showed that the oxidation mechanism of Si3N4-bonded SiC ceramics is passive oxidation and all components contribute to the formation of a silica film. The activated energies of the reactions follow the sequence Si3N4>SiC>Si. The kinetic study revealed that the oxidation of Si3N4-bonded SiC ceramics occurred in a mixed regime controlled by both interface reaction and diffusion through the silica film. Under the atmosphere conditions prevailing in the blast furnace, this ceramic is predicted to be passively oxidized with the chemical reaction rate becoming more dominant as the CO concentration increases. © 1998 Chapman & Hall

Thermochemistry of Iron Chlorides and Their Positive and Negative Ions

The iron chlorides FeCl, FeCl2, and FeCl3 and their ions FeCl+, FeCl2+, FeCl-, FeCl2-, and FeCl3- were investigated using MP2 and QCISD(T) calculations with double- and triple-ζ basis sets augmented with multiple sets of diffuse and polarization functions. The dissociation enthalpies for FeCl → Fe + Cl, FeCl2 → FeCl + Cl, and FeCl3 → FeCl2 + Cl are predicted to be 82.5, 109.6, and 59.6 kcal/mol at 298.15 K, respectively. The calculated heats of formation of these species in the gas phase at 298.15 K are +45.3 kcal/mol for FeCl, −35.8 kcal/mol for FeCl2, and −66.8 kcal/mol for FeCl3. The calculated heat of formation of FeCl is 15 kcal/mol lower than the estimated value of +60.0 (±20.0) kcal/mol reported in the JANAF tables, but is in reasonably good agreement with a recent experimental determination (+49.5 ± 1.6 kcal/mol). The calculated ionization potential of FeCl is 7.89 eV and that of FeCl2 is 10.10 eV. The electron affinities are 1.54 eV for FeCl, 0.99 eV for FeCl2, and 3.90 eV for FeCl3. Comparison o...

Nonideal thermoequilibrium calculations using a large product species data base

Thermochemical data fits for approximately 900 gaseous and 600 condensed species found in the JANAF tables (Chase et al. 1985) have been completed for use with the TIGER non-ideal thermoequilibrium code (Cowperthwaite and Zwisler 1973). The TIGER code has been modified to allow systems containing up to 400 gaseous and 100 condensed constituents composed of up to 50 elements. Gaseous covolumes have been estimated following the procedure outlined by Mader (1979) using estimates of van der Waals radii for 48 elements and three-dimensional molecular mechanics. Molecular structures for all gaseous components were explicitly defined in terms of atomic coordinates in A (Hobbs and Baer 1992a). The Becker-Kistiakowsky-Wilson equation of state (BKW-EOS) has been calibrated near C-J states using detonation temperatures measured in liquid and solid explosives and a large product species data base. Detonation temperatures for liquid and solid explosives were predicted adequately with a single set of BKW parameters. Values for the empirical BKW constants α,β, κ, and θ were 0.5, 0.174, 11.85, and 5160, respectively. Values for the covolume factors, κi, were assumed to be invariant. The liquid explosives included mixtures of hydrazine nitrate with hydrazine, hydrazine hydrate, and water; mixtures of tetranitromethane with nitromethane; liquid isomers ethylnitrate and 2-nitroethanol; and nitroglycerine. The solid explosives included HMX, RDX, PETN, Tetryl, and TNT. Color contour plots of HMX equilibrium products as well as thermodynamic variables are shown in pressure and temperature space. Similar plots for a pyrotechnic reaction composed of TiH2 and KClO4 are also reported. Calculations for a typical HMX-based propellant are also discussed.

Thermochemical heat of ablation of solid carbon

The thermochemical heat of ablation of carbon, HA, is usually set equal to 32 kJ/g as derived from the JANAF tables. There is, however, some uncertainty since JANAF-recommended values for heats of vaporization and partial vapor pressures differ from the results of a detailed analysis that was carried out at the Lawrence Livermore National Laboratory (LLNL). We find that the LLNL model yields carbon-vaporization enthalpies that are appreciably lower than the JANAF-based values. In this light, we examine experimental data generated in the course of a comprehensive investigation of laser-interaction effects in graphite and conclude that our experiments are indicative of an HA equal to 31.0±1.6 kJ/g.

The kinetics and thermodynamics of the reaction H+NH3⇄NH2+H2 by the flash photolysis–shock tube technique: Determination of the equilibrium constant, the rate constant for the back reaction, and the enthalpy of formation of the amidogen radical

Equilibrium constants K1 for the reaction H+NH3⇄NH2+H2 were measured over the temperature range 900 to 1600 K using a flash photolysis–shock tube apparatus. The experimental values of K1 ranged from 1.0 at 900 K to 2.2 at 1620 K with an estimated experimental error of about ±10%. The value obtained from the third law analysis for the enthalpy of formation of the amidogen radical, ΔH0f298 (NH2), is 45.3 kcal/mol (ΔH0f0 =46.0). The corresponding value for the bond dissociation energy, D0(NH2–H), is 107 kcal/mol. These values are in good agreement with the data tabulated in the revised JANAF tables (1982), with those derived from new measurements of the photoionization threshold for the amidogen radical, and with those from independent measurements of the rate constants of the forward and back reactions. The Arrhenius rate expression derived for reaction (−1), NH2+H2→NH3+H, is k−1(T)=5.38×10−11 exp(−6492/T) cm3 molecule−1 s−1 for the temperature range 900–1620 K. The estimated error in k−1(T) is about ±25%.

Thermodynamic Equilibria in the Si‐H‐Cl and Si‐H‐Br Systems

Equilibrium calculations were performed for the Si‐H‐Cl and Si‐H‐Br systems. Gibb's free energy of formation data from the JANAF tables were used for all species, with the exception of that for . Three conditions of interest to the electronics industry were examined: epitaxial silicon deposition, polysilicon deposition, and conversion of to. Calculated results are presented graphically: partial pressures as a function of temperature; and silicon content of the gas phase as a function of initial starting concentrations. For the Si‐H‐Cl system, higher gas phase concentrations of silicon‐containing species, and consequently, lower yields of deposited silicon were observed compared to past results. There is considerable similarity between the Si‐H‐Br and Si‐H‐Cl systems. This similarity is predicted to be greater if standard enthalpy of formation data were known more accurately for and .

Measurement of Gibbs energies of formation of CoF2 and MnF2 using a new composite dispersed solid electrolyte

Gibbs energies of formation of CoF2 and MnF2 have been measured in the temperature range from 700 to 1100 K using Al2O3-dispersed CaF2 solid electrolyte and Ni+NiF2 as the reference electrode. The dispersed solid electrolyte has higher conductivity than pure CaF2 thus permitting accurate measurements at lower temperatures. However, to prevent reaction between Al2O3 in the solid electrolyte and NiF2 (or CoF2) at the electrode, the dispersed solid electrolyte was coated with pure CaF2, thus creating a composite structure. The free energies of formation of CoF2 and MnF2 are (± 1700) J mol−1; {fx37-1} The third law analysis gives the enthalpy of formation of solid CoF2 as ΔH° (298·15 K) = −672·69 (± 0·1) kJ mol−1, which compares with a value of −671·5 (± 4) kJ mol−1 given in Janaf tables. For solid MnF2, ΔH°(298·15 K) = − 854·97 (± 0·13) kJ mol−1, which is significantly different from a value of −803·3 kJ mol−1 given in the compilation by Barinet al.