Methane coefficients

CASH CBM CBO CBPC CC CCB CCM CCP CDB CEC CFBC CFC CFR CMM COP CSH CT Calcium aluminosilicate hydrate Coal bed methane Carbon burn-out Chemically-bonded phosphate ceramics Carbonate carbon Coal combustion byproducts Constant capacitance model Coal combustion product Citrate-dithionate-bicarbonate Cation exchange capacity Circulating fluidized bed combustion Chlorofluorocarbon Cumulative fraction Coal mine methane Coefficient of performance Calcium silicate hydrate Collision theory... 

Table 3 shows results obtained from a five-component, isothermal flash calculation. In this system there are two condensable components (acetone and benzene) and three noncondensable components (hydrogen, carbon monoxide, and methane). Henry s constants for each of the noncondensables were obtained from Equations (18-22) the simplifying assumption for dilute solutions [Equation (17)] was also used for each of the noncondensables. Activity coefficients for both condensable components were calculated with the UNIQUAC equation. For that calculation, all liquid-phase composition variables are on a solute-free basis the only required binary parameters are those for the acetone-benzene system. While no experimental data are available for comparison, the calculated results are probably reliable because all simplifying assumptions are reasonable the... 

For methane-air fireballs, Hardee et al. (1978) found an of 469 kW/m. If an extinction coefficient of k = 0.18 m (as measured in LNG fires) is used, the curve shown in Figure 6.8 can be obtained from the equations given by Hardee et al. (1978). Equation (6.2.3) overstates emissivity as determined through experiments. Possible explanations are... 

Fig. 13. Activity coefficients for the n-propane (2)-methane (3) system at 100°F. (O) Data of B. H. Sage and W. N. Lacey, Some Properties of the Lighter Hydrocarbons, Hydrogen Sulfide, and Carbon Dioxide. American Petroleum Institute, New York, 1955.

Kinetic studies on the nitration of nitrobenzene by nitronium borofhioride in the polar solvents sulphuric acid, methane-sulphuric acid, and acetonitrile show the reaction to be first-order in both nitronium salt and aromatic110. With the first two solvents, the rate coefficients are similar for nitration by nitric acid and by the nitronium salts, indicating a common nitrating entity. With acetonitrile the rate coefficients are very much lower, consistent with a much lower concentration of free nitronium ions in this medium and thus with the nitronium salts existing as ion pairs in organic solvents (see Table 25). 

Ionic Reactions in TD/D2 Methane Mixtures. Previous investigation of the radiolysis of D2 containing small quantities of CH4 demonstrated that at low conversions all products anticipated from the H atom abstraction sequence except CH3D are absent from 125° to —196°C. and that the temperature coefficient of the rate of CH3D formation between 25° and 125 °C. is much too small for a purely atomic and free-radical reaction sequence (8). These observations are confirmed by new data presented in Table I. The new data also demonstrate the initial value of G(CH3D) is independent of temperature at 25°C. and below. 

In the next section we derive the Taylor expansion of the coupled cluster cubic response function in its frequency arguments and the equations for the required expansions of the cluster amplitude and Lagrangian multiplier responses. For the experimentally important isotropic averages 7, 7i and yx we give explicit expressions for the A and higher-order coefficients in terms of the coefficients of the Taylor series. In Sec. 4 we present an application of the developed approach to the second hyperpolarizability of the methane molecule. We test the convergence of the hyperpolarizabilities with respect to the order of the expansion and investigate the sensitivity of the coefficients to basis sets and correlation treatment. The results are compared with dispersion coefficients derived by least square fits to experimental hyperpolarizability data or to pointwise calculated hyperpolarizabilities of other ab inito studies. 

Table 1 Coefficients for 7[ (a ) for third harmonic generation (THG), degenerate four wave mixing (DFWM), electric field induced second harmonic generation (ESHG), and Kerr effect in methane at the experimental geometry rcH = 2.052 a.u. A CCSD wavefunction and the t-aug-cc-pVDZ basis were used. (Results given in atomic units, the number in parentheses indicate powers of ten.)...

The dispersion coefficients for the mixed-symmetry component 7 5 which describes the deviation from Kleinman symmetry are for methane more than an order of magnitude smaller than coefficients of the same order in the frequencies for 7. Their varations with basis sets and wavefunction models are, however, of comparable absolute size and give rise to very large relative changes for the mixed-symmetry dispersion coefficients. 

The CC2 model performes very different for static hyperpolarizabilities and for their dispersion. For methane, CC2 overestimates 70 by a similar amount as it is underestimated by CCS, thus giving no improvement in accuracy relative to the uncorrelated methods CCS and SCF. In contrast to this, the CC2 dispersion coefficients listed in Table 3 are by a factor of 3 - 8 closer to the CCSD values than the respective CCS results. The dispersion coefficients should be sensitive to the lowest dipole-allowed excitation energy, which determines the position of the first pole in the dispersion curve. The substantial improvements in accuracy for the dispersion coefficients are thus consistent with the good performance of CC2 for excitation energies [35,37,50]. 

Table 4 Comparison of various ab initio results and experimental estimates for the dispersion coefficients of the electronic hyperpolarizabilities 7jj and 7 of methane. (All results in atomic units. Results for the dispersion coefficients refer to single point calculations at the equilibrium geometry. Where available, dispersion coefficients for the vibrational average are given in parentheses.)...

Heat Release Rate From Fuel Gas. The fuel gas used in these tests was a mixture of natural gas supplied by the local gas company. This gas mixture contains approximately 90 percent methane and small fractions of ethane, propane, butane, C02, and nitrogen, as analyzed by Brenden and Chamberlain (6). Although composition of the gas changes with time, the changes were small in our case. A statistical sample of gross heat of combustion of fuel gas over several months showed a coefficient of variation of 0.7 percent. Also, the gross heat of combustion of natural gas reported by the gas company on the day of the test did not vary significantly from test to test. Thus, we assumed that the net heat of combustion was constant. 

---