Ventilated packaging is commonly used in the horticultural industry to facilitate efficient cooling of fresh produce during forced-air cooling. The airflow patterns and heat transfer processes inside such packaging systems are complex and research is needed to aid in the thermodynamic design and testing of such packaging systems to ensure adequate cooling and maintenance of produce quality. The aim of this research program was to develop a computational fluid dynamics (CFD) modelling system of the airflow patterns and heat transfer inside ventilated packages. In Part I of this article series, we first describe the packaging systems modelled and then present the relevant mathematical models for both airflow patterns and heat transfer inside such ventilated packaging systems based on the porous media approach. In the subsequent article (Part II), the computational solution and simulation software for the solution implementation are discussed, and then simulation results are compared with experimental data for model validation. (c) 2005 Elsevier Ltd. All rights reserved.