| A study has been conducted to provide an understanding of the flow fields and the effects on nitrogen solubility of heat-processing moist alfalfa herbage and large round bales. Field and laboratory experiments were conducted on standard soft-centre bales as well as on prebaled alfalfa samples. Along with the experimental results, a general one-dimensional mathematical model based upon the concept of fluid flow in porous media for predicting pressure gradient-apparent velocity relationships was developed.;Global viscous and inertial coefficients were predicted from the general and reduced models in planes across bale axial lengths. Porosity values were synthesized from the global viscous coefficients in the various planes based upon knowledge of alfalfa characteristic particle diameter and length using Newton Raphson's numerical method. The effects on nitrogen solubility of heat-processing bales by a means developed in this study and by other methods were investigated.;The models predicted the experimental data in the planes reasonably well except around the axial centres. Viscous forces dominated in planes around bale axial centres with inertial forces pronounced in planes near inlet and outlet faces. Predicted porosity in the planes by the general and reduced models were 0.4608 to 0.7456 and 0.4602 to 0.7450, respectively.;Higher moisture removal and temperature increases were obtained during heat-treatment of bales in a fan/heater unit developed in this study compared to heating in a Danish Ammonia Chamber. Repeatability of heat-processing large round bales in the fan/heater prior to ensiling was found to be feasible since hot water soluble nitrogen was not significantly different between 1989 and 1990 experiments.;Hot water soluble nitrogen was affected by duration of treatment, form of treatment, position (radial) and axial distances across the bales. Heat-processing large round bales prior to ensiling significantly decreased the concentration of hot water soluble nitrogen or, conversely, increased the concentration of hot water insoluble nitrogen. Heat-treatment prior to ensiling reduced proteolysis by 29.64 and 35.95% in ensiled and frozen samples, respectively, compared to the controls. |
