Heat transfer modeling of shrimp in tunnel type individual quick freezing system

Abstract

AbstractCryogenic freezers are commonly used for quick freezing of high‐value food products at a lower temperature. These freezers offer improved overall product quality and reduced dehydration and drip losses. An accurate prediction of heat transfer during the food freezing process is useful in deciding proper production, design, handling procedure, and amount of cryogen required. In this study, computational fluid dynamics (CFD) was used for numerical modeling of heat transfer phenomena in a freezing system during individual quick freezing (IQF) of shrimp. The residence time of shrimp in the developed IQF tunnel freezer was determined using modified Plank's equation and verified by experimentations. Modeling was done in two zones of the freezer: (i) Precooling zone containing cold liquid nitrogen (LN2) vapors that were utilized for precooling of incoming shrimp and (ii) freezing zone where LN2 was sprayed on shrimp before exiting freezer. Simulations of heat transfer in shrimp were performed using the Ansys CFD software at seven different locations of the IQF tunnel freezer. Results revealed that the core temperature of shrimp decreased from 304.5 K to 263 K as it passes through the freezer. In general, as compared to other segments of shrimp, core temperature of shrimp was the highest while the top portion was minimal. Dynamics of velocity distribution, thermal profile, and spray modeling results of cryogen in the freezer supported simulation model of shrimp. Overall, numerical modeling results are consistent (≤5% variation) with experimental values.Practical ApplicationsThe cryogenic freezer is widely preferred to obtain a superior quality of frozen food products owing to minimal defects (cracking and break down), drip loss, and freezing time compared to traditional mechanical freezers. The inefficient utilization of cryogen and handling issues results in a higher cost of food products frozen with IQF technology. Thus, an insight into heat transfer phenomena in cryogenic freezers may lead to improvement in the design, efficient utilization of cryogen, reduction of freezing time, and improvement in overall product quality. In conclusion, these would aid in reducing the cost of the technology.