V.A.F. Costa

On the rate of evaporation of water into a stream of dry air, humidified air and superheated steam, and the inversion temperature

The concept of inversion temperature was developed in order to assess the effectiveness of superheated steam as a drying agent when compared with dry or humid air above a given temperature. The inversion temperature can be defined in different ways, for different physical situations, thus leading to strong discrepancies between its reported numerical values. A clear understanding of such definitions and its consequences over the inversion temperature values is of major importance, as well as the way to estimate the inversion temperature of interest for a given practical evaporation process. Analytical expressions are proposed for some possible definitions of the inversion temperature. Special emphasis is devoted to the physical reasoning on the existence of the inversion temperature and how its value is affected by other variables such as humidity level, mass flow rate and geometry of the evaporative system.

An alternative approach to the inversion temperature

Abstract Above a given temperature, referred to as the inversion temperature, superheated steam is a more effective drying agent than humid air or even than dry air. However, no agreement has been reached in what concerns the definition of both the inversion temperature and its numerical value. Recent works attempted to clarify the different definitions of the inversion temperature, taking into account the obtained different numerical values. In this work, some of the ideas presented recently are developed and worked out in such a way that new graphical presentations of data are obtained, leading to a better understanding of the inversion temperature and of its value. The issues concerning the influence of the steam content of the drying agent on the evaporation rate, for different drying conditions and for a given inlet temperature of the drying agent, are clarified. The present results provide useful information on what concerns the influence of the convective drying conditions and parameters over the evaporation rate.

Modeling and Simulation of Resin Filling and Cure Processes in Molds Partially Filled with Porous Media

The complete and simultaneous simulation of the overall filling and curing processes is presented. Fluid flow in the porous medium is described by the Brinkman-Forchheimer flow model, and fluid flow in the clear fluid domain is described by the Navier-Stokes equations. The flow front is captured using the volume fraction concept and a compressive convective scheme. Energy conservation equation and resin conversion equation give the equations to obtain the temperature and degree of cure, respectively. The physical model is solved using a control volume based finite element method. A limited set of results is presented, showing the usefulness of the information obtained from the complete and simultaneous simulation of the overall real process.