This work describes a procedure for the numerical calculation of third virial coe±cients of simple linear molecules. The method is applied to nitrogen using a site-site model pair-potential and the triple dipole term. Values of volumetric and acoustic second and third virial coe±cients of nitrogen are reported over a wide range of temperature and compared with experimental data of several authors. The e®ect of including the quadrupole-quadrupole energy to the pair potential is investigated and the results suggest that the contributions of the quadrupole moment to second and third virial coe±cients are non-negligible at low temperatures.
A fourth-order virial equation of state was combined with the Lennard-Jones potential and the Axilrod-Teller triple-dipole potential to determine the thermodynamic properties of argon in the gas phase. The fourth virial coefficient is exact at the level of graphs with at most three non-additive three-body potentials. The model parameters were determined in a fit to the speed-of-sound data. The equation of state predicted the second (volumetric and acoustic) and the fourth acoustic virial coefficients of argon, but failed to give quantitative predictions of the third (volumetric and acoustic) and the fourth volumetric virial coefficients. For the third and fourth volumetric virial coefficients in which the equation of state failed to provide quantitative predictions, it nevertheless provided qualitatively accurate information on the variation of thesefunctions with temperature.In the region of the critical point, the model can be used for exploratory calculations at densities up to about 0.9ρ c .
Anaerobic digestion of goat dung and pawpaw seed and the fitness of some kinetic models in predicting the rate and cumulative production of biogas were investigated in this study, to compare biogas potential of plant and animal based wastes as well as evaluate the effect of co-digestion on biogas production. The results revealed that the goat dung produced higher volume of biogas (4943 mL) than the pawpaw seed (4329 mL). The mixture of both produced the highest volume (5871 mL) of biogas in comparison with the mono-substrates. Polynomial regression model gave the best correlation with R2 value ranging from 0.9650 - 0.9810 for the three experiments when compared with linear regression model for the ascending limb with R2 values ranging from 0.9210 – 0.9500. For descending limb, polynomial regression also gave a better fit with R2 value in the range of 0.9690 – 0.9770 than the linear regression (R2: 0.9560 – 0.9700).
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