| Freezing is an effective food preservation method,which can significantly improve the commercial value and edibility of food by inhibiting the growth of microorganisms,slowing down the activity of enzymes,preserving the original flavor and nutrients of food and other advantages.However,the formation of ice crystals during freezing can lead to mechanical damage to food tissue,compromising its morphological integrity,nutritional content and taste,thereby reducing its quality and safety.Quick-freezing technology is an effective method to improve the quality of frozen food,which can significantly reduce the time of maximum ice crystal formation zone,reduce the harm and damage of residual water to cell tissue,so as to effectively reduce the loss of food quality caused by freezing.Therefore,in order to improve the quality and economic benefits of frozen food,it is necessary to conduct in-depth research on the influence of quick-freezing technology on the spatial distribution of internal temperature during the freezing of food,so as to provide reliable theoretical support.Computational fluid dynamics is a quantitative and qualitative method used to analyze complex transport phenomena such as airflow,heat and material transfer in fluid dynamics.It has been widely used in the field of food cold chain logistics.Through the continuous improvement of numerical simulation technology,it can provide reliable technical support and scientific basis for freezing production.In addition,CFD can optimize the parameter design and operation control of the freezing process,improve the freezing efficiency and temperature uniformity of frozen foods,reduce the rate of water loss after thawing,and improve the economic benefits of the overall cold chain logistics.The main research content of this paper is divided into the following three parts:(1)Taking tilapia as an example,firstly,3D scanning reverse engineering technology is used to achieve near-real 3D physical modeling of the fish body,and at the same time,experiments of different quick-freezing methods are carried out based on industrial quick-freezing scenes.Secondly,combined with numerical simulation of computational fluid dynamics,the temporal and spatial distribution rules of temperature of tilapia under different freezing methods were analyzed to explore the influence mechanism of different freezing methods on the freezing rate,uniformity and water loss of tilapia.Finally,the accuracy of CFD model was verified combined with experimental measurements and related quick-freezing optimization schemes were proposed,in order to provide effective reference for the selection of the best quick-freezing methods for fish and the improvement of quick-freezing efficiency.The results showed that the maximum deviation between the simulated value and the measured value was1.81 ℃,the maximum root mean square error and the average absolute percentage error were 1.017 ℃ and 18.9%,respectively,and the maximum relative deviation between the simulated value and the measured value was only6.89% when the temperature of tilapia dropped to-15 ℃ during freezing process.Secondly,the freezing rate of tilapia under sodium chloride and calcium chloride immersion is basically the same.Compared with cold air freezing,the freezing time is reduced by about 73%,and the freezing uniformity is improved by about 10-40 times.The water loss rate of tilapia thawed under the two dipping and freezing methods was only 3.89 % and 3.92 %,which decreased by 10.37 %and 9.68 % compared with the cold air freezing method,respectively.(2)Based on sodium chloride immersion quick-freezing,a solution of tilapia sodium chloride liquid fluidization quick-freezing was proposed,and the effects of different inflow velocity and fish body orientation on the fish quick-freezing efficiency were comprehensively compared and analyzed,so as to optimize the solution design of sodium chloride liquid fluidization quick-freezing.In the simulation process,five different velocity inlet velocity were used to determine the optimal inlet velocity of tilapia during the freezing process according to the relationship between energy consumption and freezing rate growth,as well as the change of freezing uniformity.Secondly,three different tilapia placement modes were simulated,and the best placement mode was obtained by combining quick-freezing efficiency and freezing uniformity.The results showed that the flow rate of tilapia sodium chloride liquid was2.5m/s,and it was best to place the tilapia sodium chloride liquid horizontally facing the entrance.(3)In order to realize the intelligent control of quick-freezing technology of agricultural products,it is necessary to analyze and study the temperature field inside the quick-freezing device and the freezing efficiency of tilapia more deeply.Based on CFD numerical simulation results,Visual Studio Code 1.75.1 and My SQL 8.0.32 were used as development tools to develop a query system for tilapia temperature and freezing efficiency under different quick-freezing methods under mac OS environment.The system can effectively master the changing law of temperature field in the freezing process by displaying the three-dimensional image of temperature field inside the freezing device and the changing process of freezing time of tilapia,and analyzing and querying it.In addition,the system can also dig and analyze the numerical simulation results in depth,and explore the relationship between the temperature field and freezing rate,physical parameters and other factors in the quick-freezing process,so as to provide a more accurate and reliable theoretical reference for the intelligent control of the quick-freezing technology of agricultural products.In this paper,tilapia was taken as the research object,3D scanning reverse engineering technology was used to achieve near-real 3D physical modeling of the fish body,and the influence mechanism of different quick-freezing methods on the freezing rate,uniformity and water loss of tilapia was analyzed in combination with computational fluid dynamics numerical simulation,so as to determine a quick-freezing method conducive to the freezing rate and quality maintenance.The experimental results were basically consistent with the test values.It embodies the rationality of the experimental process and the accuracy of the experimental results.In addition,based on the above quick-freezing method,the sodium chloride liquid fluidization quickfreezing method was proposed,and the optimal combination method was obtained by combining the experiments of different inlet velocity and fish body placement.In order to realize intelligent control of quick-freezing technology of agricultural products,a query system for temperature and freezing efficiency of tilapia under different quickfreezing methods was developed,which can effectively master the variation law of temperature field and freezing efficiency of tilapia during the quick-freezing process,and deeply dig and analyze the relationship between temperature field and freezing rate,physical property parameters and other factors.In this paper,the spatial distribution of the internal temperature field of tilapia under different quick-freezing methods was studied,and the future development trend of CFD application in the field of cold chain logistics was discussed.The research provides a reliable theoretical support and reference for improving the freezing rate and uniformity of agricultural products,reducing energy waste,ensuring product quality and realizing the intelligent control inside the quick-freezing device.This research is expected to promote the energy saving,environmental protection,intelligent and efficient development of agricultural cold chain logistics. |
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