Recent developments in the modelling of imperfectly mixed airspaces

This paper discusses the Data-Based Mechanistic (DBM) approach to modelling the micro-climate in agricultural buildings. Here, the imperfect mixing pr ocesses that dominate the system behaviour during forced ventilation are fi rst modelled objectively, in purely data-based terms, by continuous-time tr ansfer function relationships. In their equivalent differential equation fo rm, however, these models can be interpreted in terms of the Active Mixing Volume (AMV) concept, developed previously at Lancaster in connection with pollution transport in rivers and soils and, latterly, in modelling the mic ro-climate of horticultural glasshouses. This can be compared with the inco mplete mixing and control volume concepts that have been investigated previ ously at Leuven. The data used in the initial stages of the research projec t, as described in the paper, have been obtained from a series of planned v entilation experiments carried out in a large instrumented chamber at Leuve n. The overall objectives of this collaborative study are twofold: first, t o pain a better understanding of the heat transfer and micro-climate dynami cs in the chamber. and second, to develop models that can form the basis fo r the design of optimal Proportional-Integral-Plus (PIP-LQ) climate control systems for livestock buildings of a kind used previously for controlling the micro-climate in horticultural glasshouses. Although not specifically d irected at glasshouse systems, the techniques described in the paper can be applied straightforwardly within a glasshouse context. (C) 2000 Elsevier S cience B.V. All rights reserved.