# Simulation-Based Analysis of the Effect of New Immersion Freezing Equipment on the Freezing Speed
## 3 Results and Discussion
### Effect of Refrigerant Flow Rate on Freezing Time and Freezing Effect of Pork  
The temperature distribution in the freezing chamber of the immersion refrigeration equipment simulated by Fluent software was mainly shown by the overall three-dimensional structure diagram. In order to better analyze and study the internal flow field, different sections were in different directions for research and analysis when the stereoscopic diagram could not be used for better analysis. Due to the simplicity and symmetry of the model in this paper, the \(x\)-\(y\) plane is selected randomly for temperature field analysis. Fluent was used to simulate the temperature change of pork in the immersion freezing equipment. Two variables, namely, the flow rate of refrigerant (v = 1, 2, 3, 4, 5 m/s) and the speed of pork with the hopper (r = 0, 2, 4, 6, 8, 10 rad/s), were set. Thirty groups of comparative simulation analyses were conducted. The freezing data were obtained through temperature program, velocity program, velocity vector graph, and pork center temperature detection curve. Through comparative analysis, the influence of flow rate and rotation speed on freezing time and freezing effect was analyzed. When the rotation speed of pork with the rotating hopper r = 0 rad/s, the temperature cloud diagram in the freezing bin at the flow rate of refrigerant (v = 1, 2, 3, 4, 5 m/s) is shown in Figure 5.  
Figure 5 shows the temperature distribution in the freezer. Different colors correspond to different temperatures, and blue represents the lowest temperature in the freezer. The middle area represents the temperature distribution of pork in the refrigerant, and the red area represents the highest temperature in this temperature field. See the legend on the left for the specific temperature. It can be seen from the three-dimensional temperature program that the temperature in the freezer is kept at the pre-cooling temperature of \(-\)20 \({}^{\circ}\)C, the temperature of pork gradually increases from the outside to the inside, and the central temperature is \(-\)18 \({}^{\circ}\)C. Observing the temperature program of \(x\)-\(y\) section reveals that the temperature gradient of pork is divided into five layers. From outside to inside, the temperature gradually rises, and the central temperature reaches \(-\)18 \({}^{\circ}\)C. The overall regional freezing effect shows an oval shape, with a large temperature gradient, and an uneven freezing effect. Comparing the five groups of simulated temperature programs of refrigerant flow rate (v = 1, 2, 3, 4, 5 m/s), it can be clearly seen that there is no obvious difference between the three-dimensional temperature program and the \(x\)-\(y\) section temperature program. In general, the temperature clouds were similar to those described by [PERSON] et al. [19]: the freezing process does not proceed at a uniform rate, and the freezing effect changes gradually from the outer layer to the center. The adjustment of external freezing conditions can improve the freezing effect. Figure 5: _Cont._Figure 5: _Cont._  
The following information can be obtained from Figure 6. (1) When freezing starts, the central temperature drops rapidly, but at a certain time, there will be an inflection point, and the slope of the curve of the central temperature decline gradually becomes flat. (2) With the increase of refrigerant flow rate, the inflection point will move left along the coordinate axis. This is because when the food is frozen, the free water molecules in the cell will condense into small ice crystals, and the small ice crystals will gather slowly to form ice crystal bands. The freezing time before the inflection point is the time when the largest ice crystal band is formed. The shorter the period, the higher the frozen quality of the food [20].