Viscosity and Density of Isobutane Measured in Wide Ranges of Temperature and Pressure Including the Near-Critical Region

摘要

Accurate pT data for isobutane were measured for nine isotherms between 298.15 and 498.15 K using simultaneously a vibrating-wire viscometer and a single-sinker densimeter. The maximum pressure was 93% of the saturated for subcritical isotherms and 30 MPa for supercritical isotherms. The density measurements are generally characterized by an uncertainty of 0.1%. Allocation errors for temperature and pressure influence significantly their uncertainty in the near-critical region. A comparison with the equation of state by Bucker and Wagner shows agreement normally within +/- 0.1%. The near-critical isotherm 410.15 K reveals differences to -3.7% exceeding the uncertainty of 1.9%. The uncertainty in viscosity is 0.3%. The comparison with the correlation of Vogel et al. yields deviations exceeding the uncertainty of the correlation (3%). The critical enhancement becomes evident for the near-critical isotherm amounting to 1.4%. The new data will improve the viscosity surface correlation. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 3116-3137, 2015