Showing papers by "Eric W. Lemmon published in 2017"

The Precise Measurement of Vapor–Liquid Equilibrium Properties of the CO$$_{}$$/Isopentane Binary Mixture, and Fitted Parameters for a Helmholtz Energy Mixture Model

Abstract: Natural working fluid mixtures, including combinations of CO $$_{2}$$ , hydrocarbons, water, and ammonia, are expected to have applications in energy conversion processes such as heat pumps and organic Rankine cycles. However, the available literature data, much of which were published between 1975 and 1992, do not incorporate the recommendations of the Guide to the Expression of Uncertainty in Measurement. Therefore, new and more reliable thermodynamic property measurements obtained with state-of-the-art technology are required. The goal of the present study was to obtain accurate vapor–liquid equilibrium (VLE) properties for complex mixtures based on two different gases with significant variations in their boiling points. Precise VLE data were measured with a recirculation-type apparatus with a 380 cm $$^{3}$$ equilibration cell and two windows allowing observation of the phase behavior. This cell was equipped with recirculating and expansion loops that were immersed in temperature-controlled liquid and air baths, respectively. Following equilibration, the composition of the sample in each loop was ascertained by gas chromatography. VLE data were acquired for CO $$_{2}$$ /ethanol and CO $$_{2}$$ /isopentane binary mixtures within the temperature range from 300 K to 330 K and at pressures up to 7 MPa. These data were used to fit interaction parameters in a Helmholtz energy mixture model. Comparisons were made with the available literature data and values calculated by thermodynamic property models.

Algorithms for the calculation of psychrometric properties from multi-fluid Helmholtz-energy- explicit models

Abstract: Psychrometric properties of humid air are widely used in the analysis and modeling of thermal systems. In this work, we present a method for obtaining these properties from the multi-fluid mixture formulation of the GERG mixture model. This mixture model was originally developed to model the thermodynamics of natural gas mixtures, and more recently has been extended to model thermodynamic properties relevant for carbon capture and storage. The primary advantage of this formulation is that the dry air composition is not fixed, and can be adjusted to suit the application, for instance for combustion flue gases, for air in submarines, for Martian atmospheres, etc. Furthermore, this multi-fluid framework employs the highest accuracy pure-fluid equations of state in the literature. We present algorithms that can be used to calculate the quantity of water in the saturated vapor in vapor-liquid and solid-vapor equilibria, and other properties that arise out of these equilibria calculations, such as relative humidity and humidity ratio. We also present algorithms for converting other common sets of independent variables (e.g., wet-bulb temperatures), to the natural variables of the mixture model. Comprehensive discussion of the developed algorithms is provided, as well as sample code in the C++ language.

Organic fluids for Organic Rankine Cycle systems: Classification and calculation of thermodynamic and transport properties∗

Abstract: Thermophysical properties (thermodynamic properties, thermal conductivity, viscosity, and surface tension) of pure fluids and mixtures are used extensively in the simulation of Organic Rankine Cycles over the entire continuum from simplified cycle analyses to detailed dynamic system modeling. This chapter provides a summary of the state-of-the-art formulations that are available in the literature and some detail about how the models can be used to evaluate thermophysical properties. Furthermore, a summary is provided of the state-of-the-art libraries that are available for the evaluation of these thermophysical properties.