The need for accurate thermophysical property prediction for diverse formulation mixtures is expected to grow, as next-generation formulations with low global warming potential (GWP) are introduced and as usage of predictive simulation increases during pMDI development. This need can be supported by appropriate experimental measurement campaigns for formulation mixtures, spanning the full range of temperature, pressure and composition that will be encountered by pMDI internal flows and aerosols. A promising set of methods for representing and predicting many of these mixture thermophysical properties is a framework of physically-based models that use activity coefficients to describe non-ideal molecular interactions in the liquid phase, which can affect such properties. These models are particularly useful for solution formulations containing ethanol.
Propellant and formulation properties for next-generation pMDIs: Measurement, representation and prediction
In this article, the fundamental thermophysical properties that control the complex internal flow and aerosol formation process in a pMDI will be examined, from the perspective of their measurement, representation and prediction. Activity coefficient models that enable simultaneous description and prediction of important formulation thermophysical properties will also be presented. The performance of these models is demonstrated using existing data for HFA134a/ethanol mixtures, to show their potential application alongside experimental property data collection involving future propellants.