Kihara parameters and second virial coefficients for cryogenic fluids and their mixtures



The volumetric properties of sixteen fluids of interest in cryogenic engineering have been used to calculate second virial coefficients over as large a temperature range as possible. These coefficients were then fitted to theoretical expressions based on the Kihara potential function. For helium, hydrogen, and neon quantum corrections were applied. For nitrogen, carbon dioxide, and acetylene corrections for quadrupole interactions were made. It was found that the theoretical expressions give an extremely good fit of all reliable experimental datu. The theoretical expressions may therefore be used with confidence to predict volumetric behavior at very low temperatures where data are frequently unavailable.

With the aid of semiempirical mixing rules the theoretical expressions may be used to predict second virial coefficients for mixtures. Agreement with the very limited amount of experimental mixture data is satisfactory. Finally it is shown that calculations based on the Kihara potential may be employed to make useful predictions of phase equilibria such as the solubility of a solid in a compressed gas.