Determination of an effective heat transfer coefficient for immersion water cooling of canned foods

Transient temperature measurement inside cans packed with tomato purees were used to estimate can surface heat flux as a function of time during the immersion cooling cycle of the thermal processing of canned foods. The estimation was carried out using a developed computer program based on a sequential function specification algorithm. The estimated heat fluxes were used to solve the direct heat conduction problem for the cans' internal temperature distributions at any position and time including internal surface temperature. The accuracy of the calculated heat flux was verified using the root mean square error for the temperatures at the sensor position. An effective heat transfer coefficient as a function of time was calculated from the knowledge of surface temperatures and heat flux history. A time-averaged effective heat transfer coefficient of 137 ± 7 (W/m²·C) was obtained in this study, which was comparable to a published value obtained using pilot scale data. This research work provides a systematic approach for estimating heat transfer coefficients during food processing operations. The method was based on both the inverse and the direct solution of heat conduction in cylindrical geometry. The experimental setup showed that with a single transient temperature measurement, an accurate estimate of an effective heat transfer coefficient can be achieved. This research also showed how heat transfer coefficient changes with time during immersion cooling. The effective heat transfer coefficient accounts for the internal lacquer coating and external polymeric printing coating thermal resistances. The heat transfer coefficient obtained in this research is an addition to scarce data on such an important parameter, which will help in the optimization of the thermal processing of canned foods by accounting for the cooling phase lethality.