Article pubs.acs.org/jced
An Estimation Method for Thermal Conductivity in the Fluid Phase Karsten Müller* and Wolfgang Arlt Friedrich−Alexander−University of ErlangenNuremberg, Institute of Separation Science and Technology, Egerlandstrasse 3, 91058 Erlangen, Germany S Supporting Information *
ABSTRACT: An estimation method for thermal conductivity in the gas as well as in the liquid phase is presented in this work. The models are based on group contributions of the second-order. Temperature dependence could be described well if a valid reference temperature is used as an additional input parameter. For the gas phase the critical temperature was chosen as the reference temperature, and for the liquid phase the normal boiling temperature was chosen. Relative errors are within a magnitude of 10 % for the gas phase and 7 % to 14 % for the liquid phase. Estimation quality is high for small as well as for high absolute values of the thermal conductivity and independent of substance class or molecule size.
1. INTRODUCTION Knowledge of heat transfer characteristics is crucial in process design, for example, for the control of exothermal chemical reactions. Data concerning heat transfer in the respective media are often missing for new reactions (and substances). An important property in this context is the thermal conductivity. Thermal conductivity in the near-critical region can be correlated to the density of the respective substance.1 In the gas phase it can be estimated using the kinetic gas theory.2,3 However, these approaches require a huge number of additional input parameters such as the acentric factor, the dipole moment, and the association parameter, which are not available for all compounds. Furthermore, the correlation equation for one of the parameters is only valid for unpolar substances. In the case of polar substances, this parameter has to be known for the respective substance and therefore no prediction is possible. Group contribution methods are a route for estimation that is easier to handle. A further advantage of these approaches is the fact that they require few input parameters besides the molecular structure. Group contribution methods concerning the thermal conductivity of liquids have been proposed by Nagvekar and Daubert4 and Sastri and Rao.5,6 Roy and Thodos7,8 have proposed a method for gases that is based on simplified molecular structures. This method can be seen as a predecessor of higher group contribution methods. Its main drawback is its applicability to only a limited number of substances. However, to the best of our knowledge, no more advanced group contribution method has been proposed for the gas phase so far. Since thermal conductivity strongly depends on temperature a respective estimation method has to account for this fact. The thermal conductivity λgas/W·m−1·K−1 in the gas phase increases © XXXX American Chemical Society
with increasing temperature T as expected from the kinetic gas theory: 4·10−5 W·m−1·K−2
