A numerical modelling approach for biomass field drying

Abstract

In grass conservation systems, the field drying process of cut grass is an important function since it determines subsequent losses and possible hazardous effects of during silage. The drying process of harvested grass was evaluated using two different numerical approaches. Firstly, an existing experimentally-verified analytical model was used. Several parameters were improved from previous studies such as the evaluation of stomata conductance from outside climate variables. Secondly, a CFD modelling approach was applied to open field drying process of the biomass. The cut biomass in the field was simulated using the equivalent macro-porous medium approach. Experimental values were used to obtain realistic and accurate boundary conditions. The developed CFD model was validated using the existing analytical model that is based on evaporations as estimated from the Penman equation. An acceptable agreement between simulated and measured values of water content was obtained. The mean difference in the estimated outputs from the two models was 8%. Condensation occurred during the night and was correctly simulated by both types of models. In general, a good correspondence was found between the two approaches. The use of the CFD model reveals the climate heterogeneity in the grass area and also, creates the possibility of applying the model as a decision support model for an enhanced treatment of the grass after cutting.