The presented study aims to experimentally investigate the potential of flash sanitation (short time exposure to hot air stream) for wheat seeds to control surface contamination and protect against fungal diseases. Experiments were conducted at the laboratory scale using very short residence times (2–4 s) and higher temperature range (150–350 °C) of dry air stream at two different flow rates (280 L/min and 557 L/min). The goal was to identify thermal conditions that provide high sanitation efficiency while maintaining seed viability. A design of the experiment approach, employing central-composite design and face-centred response surface methodology, was used to evaluate the effects of the thermal treatment on seed surface temperature, sanitation efficiency, and germination capabilities. Higher air flow rate (557 L/min) significantly increased post-treatment seed surface temperatures (42.1–122.7 °C) compared to the flow rate of 280 L/min (36.7–80.5 °C). Pronounced germination drops were observed with air temperatures above 175 °C. Satisfactory sanitation efficiency >90% was achieved only with high-temperature air >250 °C, which, however, caused unacceptable germination loss. Extending residence time beyond the experimental plan is unlikely to yield significant benefits, as the factor was identified as weak and insignificant compared to temperature. Higher flow rates improve heat transfer but require strict control to prevent variability affecting seed quality. The heating media flow rate should be considered an essential factor in thermal treatment studies. Dry air has not proven to be appropriate for seeds’ flash sanitation within the selected experimental condition framework.

Purpose – The purpose of this paper is to report a novel formulation of convective heat transfer source term for the case of flow through porous medium. Design/methodology/approach – The novel formulation is obtained by analytical solution of an idealized dual problem. Computations are performed by dedicated tool for fixed bed combustion named GRATECAL and developed by the authors. However, the proposed method can also be applied to other porous media flow problems. Findings – The new source term formulation is unconditionally stable and it respects exponential decay of temperature difference between the fluid and porous solid medium. Practical/implications – The results of this work are applicable in the simulation of convective heat transfer between the fluid and porous medium. Applications include e.g. fixed bed combustion, catalytic reactors and lime kilns. Originality/value – The reported solution is believed to be original. It will be useful to all involved in numerical simulations of fluid flow in ...