| In the first part of this study, the interrelationships between steam consumption and production factors, such as can size, food consistency, retort temperature, initial food temperature and target lethality, were studied statistically. It was observed that food consistency, retort temperature and target sterilizing value have strong influence on steam consumption. It was also observed that a high level of retort temperature increases nutrient retention when the target sterilizing value is high.;A method was developed to determine the thermophysical properties, such as the thermal diffusivity and thermal conductivity of the insulation, and contact conductance, surface heat conductance and emissivity of the insulation surface. These properties were used in the above model to determine heat loss through the insulated wall.;Three general types of retort temperature policies, namely, a standard process, ramp functional and square wave types, were examined theoretically and experimentally for nutrient retention and steam consumption. From these studies, it was observed that a profile with ramp function or a single square wave produces slightly higher nutrient retention while using about 60% less heat compared to that required by a process using a standard retort temperature profile.;In the second part of the study, computer models were developed to estimate heat loss through the insulated wall of a vertical still retort and its component parts, namely, the uninsulated flange, clamp supports (extended bodies) and blister. Also, a model was developed to estimate heat loss with the steam-air mixture passing through a vent and a bleeder. All these models were developed on the basis of unsteady heat transfer considering radiative and convective boundary conditions. |
