Energy consumption reduction strategy for freezing of packaged food products

Abstract

On this work, a model of the process of freezing strawberries placed in boxes using forced air tunnel was studied. A strategy of operating condition modification in each stage of the process (pre-cooling, freezing step and sub-cooling) was applied, in a simulated process, regarding air temperature change. Time and energy consumption behaviors due to air temperature conditions in the tunnel were evaluated for each stage. Air temperature at different process stages affected both process times and system thermal demands. Dperating conditions for each stage, which provided the best system global performance, were chosen, aiming energy consumption reduction without damaging product final quality, once each stage minimum requirements were taken into account. The strategy proposed produced an energy economy of 5.9%, comparing to the traditional process using constant temperatures, and it showed potential to be applied in different products and equipment with appropriate changes in the methodology.

Alternative freezing: Effects on rehydration properties of freeze‐dried daikon (Raphanus sativus L.)

“…Finally, the use of modified freezing conditions is interesting in terms of energy‐saving, since previous studies showed that it is possible for vapor compression refrigeration systems to have their energy consumption reduced up to 5.9% by adopting higher temperatures at the precooling and subcooling (Gonçalves & Silveira Junior, 2018).…”

“…Once the last out of thermocouples TE01 to TE03 indicated −10.0°C, a third set point change was made, at −24°C, which was kept until the end of the process (after all thermocouples TE01 to TE03 reached −18°C). These conditions were chosen based on results from a previous study, which indicated −7°C and −24°C as potentially adequate temperatures for energy saving in the operation (Gonçalves & Silveira Junior, 2018).…”

“…In the process under variable by levels condition (CL), the initial chamber set point temperature was adjusted at −7 C. Such a temperature was kept until the first among thermocouples TE01 to TE03 showed 2.0 C. At this point, the temperature was set at −30 C. Once the last out of thermocouples TE01 to TE03 indicated −10.0 C, a third set point change was made, at −24 C, which was kept until the end of the process (after all thermocouples TE01 to TE03 reached −18 C). These conditions were chosen based on results from a previous study, which indicated −7 C and −24 C as potentially adequate temperatures for energy saving in the operation (Gonçalves & Silveira Junior, 2018).…”

“…Finally, the use of modified freezing conditions is interesting in terms of energy-saving, since previous studies showed that it is possible for vapor compression refrigeration systems to have their energy consumption reduced up to 5.9% by adopting higher temperatures at the precooling and subcooling (Gonçalves & Silveira Junior, 2018). Accordingly, as modified processes produced products of higher (CD) or similar quality (CL), as to rehydration aspects, comparing to the conventional condition (CC30), and also enabled energy saving, such methodologies are of great technological and industrial interest.…”

“…The methodology was based on the application of higher temperatures in the stages that take place before and after the ice crystals formation and growth, keeping a suitable temperature difference between the product and cooling medium, to provide an adequate heat transfer driving potential. Simulation experiments showed that this methodology allows an energy saving of up to 5.9%, comparing to an operation under constant conditions, equivalent to the lowest temperatures applied on the modified process (Gonçalves & Silveira Junior, 2018). The study focused exclusively on energetic aspects, thus, quality changes resulting from the methodology were not evaluated.…”