Study of the effects of noisy data on the determination of the enthalpy of vaporization from a vapor pressure equation

Abstract

Chemical engineers use software tools everyday to aid them in solving complex problems. Software packages simulate virtually every aspect of a chemical process, including the use of source vapor pressure data to fit empirical constants of a vapor pressure equation. The slope of the vapor pressure is used in the calculation of the enthalpy of vaporization. Some multi-parameter vapor pressure equations are sensitive to noisy data which causes errors in the expression for the relationship between temperature and vapor pressure. These errors propagate through the calculation of the latent heat of vaporization and any design equation in which the enthalpy of vaporization appears. The enthalpy of vaporization is important in the design of multiphase reactors, heat exchangers, distillation columns and numerous other unit operations. Errors in its computation can lead to compounding errors, which gone unchecked, can lead to the construction of a chemical plant doomed to explode or otherwise fail. To avoid the errors sometimes introduced by multi-constant vapor pressure equations a vapor pressure equation restricted to yield results that more closely mirror natural phenomena should be used. The Asymptomatic equation studied is an example of a naturally constrained and very accurate vaport pressure equation.