Temperature Analysis And Numerical Simulation Of Shrimp Freezing Process

Because of its advantages of easy preservation, convenient and health, frozen food has become the world’s fastest growing processed foods and its consumption is also the largest. Our country has the highest aquaculture production in world and frozen seafood is the largest export agriculture industry. Southern white shrimp has great commercial values. However, there is little reseach on its freezing process. The data and parameters are often estimated from fish processing technology in actual production. Accurate calculation of the temperature during shrimp freezing process can guide the production control and design of quick-frozen equipment, which is very important to ensure the quality of frozen shrimp.Taking southern white shrimp for research object, the temperature profile and its numerical simulation during freezing process were studied in this paper. The main research contents and conclusions are as follows.The size, composition, specific heat capacity, water content, ice content, density of shrimp and surface heat transfer coefficient of the refrigeration system were determined by experiment measuremnets or analysis. Meanwhile, the core temperature of shrimp body was measured continuously to analyse temperature curve during freezing process, which laid a foundation for the design and build of freezing model.Freezing effect at different positions of freezer was analysed by thermal infrared imaging technology. Being higher placed, the samples had a smaller freezing rate and cost more time to reach initial freezing point. The freezing rate was greater in both sides of the freezer than the middle position. However, shrimp freezed in middle position had a more uniform temperature distribution.Based on above research, a two-dimensional finite element numerical model was built, and the calculated core temperature of shrimp body was validated by experiment measurements. Results showed that the established two-dimensional model can effectively predict the temperature trend and accurately reflect values of each point in time. The calculated values are very close to standard freezing curve in references. Temperature profile of shrimp and its change under different freezing conditions were analysed. Caculation results showed that phase change range and temperature of cooling air had significant effect on the results. Without regard to the latent heat, there was no stable temperature period in figures generated by the model and the cooling rate calculated was faster than the reality.A2D numerical model was used to predict temperature change of shrimp freezed in plate freezer. Comparing the predicted values and the actual measured results, the basic trends were consistent, which showed that the numerical model had a certain reference meaning for analysing the actual shrimp freezing process.