Carbon Dioxide + Fluoromethane and Nitrous Oxide + Fluoromethane: Solid−Liquid Equilibria Measurements

Abstract

A recently built experimental setup was employed for the estimation of the solid-liquid equilibria of alternative refrigerants systems. The behavior of two binaries, i.e. carbon dioxide + fluoromethane (CO 2 + R41) and nitrous oxide + fluoromethane (N 2 O + R41), was measured down to temperatures of 126.5 K. To confirm the reliability of the apparatus, the triple points of the pure fluids constituent the binary systems were measured. All triple point data measured revealed a generally good consistency with the literature. The results obtained for the mixtures were corrected by the Rossini method and interpreted by means of the Schröder equation.

Liquidus in the CO2 + and N2O + Hydrofluorocarbon Systems

“…The experimental isochoric and SLE data were obtained by experimental apparatuses presented elsewhere. [1][2][3][4][5][6][7][9][10][11][12][13][14] The information on the SLE data measurements along with the VLE data for corresponding binaries measured by the isochoric method is presented in Table 1. From the Table 1, it is easily evident that the temperatures of isochoric PVTx in two-phase region data are covering a higher temperature range than SLE data for which, obviously, the upper limit of temperature corresponds to the melting temperature of the solute or solvent, whatever is higher.…”

“…The experimental SLE results showed that the presented CO 2 + and N 2 O HFCs binaries form the eutectic. − In the above-mentioned papers, the eutectic points (temperature and composition) were estimated from a graphical interpretation of the liquidus. The accuracy of the method depends on the shape of the liquidus curve and on the experimental data point distribution; hence, in this paper previous estimates are re-evaluated.…”

“…By analyzing the SLE data of the CO 2 + HFCs and N 2 O + HFCs systems published successively by us, − we found that the liquidus representing CO 2 and N 2 O branches are well-represented by the Schröder equation in its simplified form: ln x 2 = − Δ H m R T true( 1 − T T t true) after disregarding contributions from the Δ C p and activity coefficient (γ) terms.…”

“…As the second system's component, a series of the hydrofluorocarbons (HFCs) were chosen. The systematic study covered the experimental measurements of solid−liquid equilibria (SLE) of CO 2 and N 2 O + HFCs (R32, R125, R134a, R143a, R152a, R23, and R41) − by the Rossini method and, finally, of PVTx by the isochoric method. − The PVTx data in the two-phase region enable VLE parameters to be derived using a flash method with the Carnahan−Starling−De Santis equation of state (CSD EOS) …”