Reference Correlations of the Thermal Conductivity of Cyclopentane, iso-Pentane, and n-Pentane

New, wide-range reference equations for the thermal conductivity of cyclopentane, iso-pentane, and n-pentane are presented. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. In the critical region, the enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter, estimated by a predictive scheme. The thermal-conductivity equations behave in a physically reasonable manner over a wide range of conditions that correspond to the range of validity of the most accurate equations of state for each fluid. The estimated uncertainties of the correlations are dependent on the availability of accurate experimental data for validation, and are different for each fluid, varying from 1% (at the 95% confidence level) for the liquid phase of iso-pentane over the temperature range 307 K < T < 355 K at pressures up to 400 MPa (where high-accuracy data are available) to a more typical 4% for the liquid phase of cyclopentane over the temperature range 218 K < T < 240 K at pressures to 250 MPa. Estimated uncertainties in the gas phase are typically on the order of 3%-5%. For all three fluids, uncertainties in the critical region are much larger, since the thermal conductivity approaches infinity at the critical point and is very sensitive to small changes in density. (C) 2015 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved.