LAUSR

Abstract The effects of jar geometry and % starch on heat transfer and fluid flow in food models were studied. Five jars (high cylinder, short cylinder, square, flared and hexagonal) and six (0%, 2%, 3%, 4%, 5% and 6%) starch concentrations were investigated. Mathematical models were validated against experimental data and used to compare heat transfer and fluid flow. Overall heat transfer coefficient (OHTC) resulted influenced by jar geometry and, at low starch concentration, flared one showed the highest values while at 5 and 6% the high cylinder resulted the most favourable. Regarding natural convection, square gave the highest mean velocity probably due to the higher external surface while flared gave the lowest. CFD models allowed identifying the location of slowest heating/cooling zone (SHZ/SCZ) and pasteurizing values at geometric centre resulted higher than those at the SHZ (+15%), unacceptable as an overestimation could cause serious safety problems. In addition, the highest overestimation was observed for samples with 3%, 4% and 5% of starch which gave high viscosity products that could be easily confused with purely conductive ones and could bring to consider geometric centre as the SHZ.