CFD Modelling of the 3D Spatial and Temporal Distribution of 1-methylcyclopropene in a Fruit Storage Container

In this paper, a direct model based on explicit geometry of stacked products in boxes was developed and used to study the diffusion, convection and adsorption of 1-methylcyclopropene (1-MCP) gas in cool stores for apple fruit. The discrete element method was employed to generate random stacking of spherical products in a box. A three-dimensional finite volume-based computational fluid dynamics model was developed, verified and used to study the distribution and partitioning of the 1-MCP gas inside loaded container. The study addressed the gas distribution in a 500 L container with or without air circulation. For each case, 80 kg Jonagold apples at 1 °C and a 1-MCP dose of 1 μL L^?1 was used to collect validation data. In the presence of air circulation, diffusion–convection in air and diffusion adsorption in the product was applied. Simulations were performed with an unstructured tetrahedral mesh using the software ANSYS-CFX, a Reynolds-averaged Navier–Stokes solver. The case without air circulation was modelled as a diffusion problem in air and diffusion coupled with adsorption inside the product. Convection–diffusion–adsorption model parameters that were previously developed and validated were applied. The estimated equilibrium distribution of the 1-MCP gas equals 11, 34 and 55 % as unbounded in fruit, bonded in fruit and remaining in container, respectively. Profiles of free (unbounded) and adsorbed (bounded) 1-MCP concentrations inside fruit were estimated for reduced dosages: 0.5, 0.3, 0.1 and 0.02 μL L^?1.