Modélisation et optimisation énergétique de procédés

Abstract

The agro-foodstuffs products drying is an essential operation to ensure optimal preservation conditions. This operation, often carried out using highly energy-consuming techniques. Therefore, it's important to dispose a high energy efficient drying process. The aim of this study is the development and validation of a complete numerical tool for the design of a heat pump assisted dryer. The studies carried out concern the potato drying. The physical, water and thermal properties required for numerical simulation have been determined; and a drying bench within the IRDL was instrumented to have the drying kinetics a product placed in a chamber. The analysis and comparison of the experimental results make it possible to observe the impact of the operating parameters (temperature, humidity and air speed) and the product thickness on the rate drying. A unidirectional numerical model of coupled mass and heat transfers has been developed in a Lagrangian referential to overcome the structural changes. It enables to access the moisture content field and the temperature within the product, while taking into account the shrinkage phenomenon. The estimation of the evaporation surface and the convective transfer coefficient by inverse method allowed us a satisfactory representation of drying kinetics. A second unidirectional numerical model that takes into account the air characteristics evolution is combined with a global model of a trays dryer. Simulations allow the drying kinetics prediction of each particles tray and of air characteristics leaving the dryer. Meanwhile, an additional computing module has been developed with a view to designing the heat pump system.