| With the development of human society,global energy consumption has risen rapidly,and the contradiction between environmental pollution caused by fossil energy and sustainable economic development has become increasingly acute.In 2021,China put forward the development concept of "carbon peaking and carbon neutrality",aiming to achieve a green and low-carbon economic development system.In addition,due to the improvement of consumption level,the public has higher requirements for food freshness,so ice is becoming increasingly important in people’s lives.In this paper,numerical simulation is used to simulate the addition of spray bubbles to assist ice production,and the phase transition process of heat and mass transfer during water freezing is simulated and analyzed.The experiment uses the level set method for gas oscillation to simulate gas-liquid two-phase flow.Finally,a test bench was built for experimental research,and the rate and quality of ice making under different experimental conditions were obtained by changing different temperatures,gas flow rates and nozzle diameters.The main conclusions of this paper are as follows:(1)The simulation results show that the overall change trend of the velocity field is related to the height of the nozzle from the bottom surface of the container and the size of the pipe diameter.The higher the height of the nozzle from the bottom surface of the container,the larger the pipe diameter,and the more significant the overall trend change of the velocity field.However,the velocity field change is slightly delayed when the pipe diameter is D=2 cm.The oscillation intensity and velocity in the gas pipe increase with the increase of ice thickness.The gas volume fraction variation increases with temperature,pipe diameter,and gas flow parameters.In the simulation,the temperature field change is not significant,but it can be observed that the change trend of the temperature field with the working conditions is basically consistent with the velocity field.Compared with the temperature field,the water freezing phase transition process changes more obviously,the phase diagram shows a "U" shape change,and its change accelerates significantly with the change of distance and pipe diameter.(2)The influence of different working conditions on the ice making rate is as follows:under the condition that other parameters are the same,the influence of temperature on the ice making rate is that the lower the temperature,the faster the cooling rate,and the shorter the icing time.The influence of gas flow on ice rate was that the icing time decreased with the increase of gas flow at-8 °C and-10 °C.At-12 °C,the icing time decreases and then increases with the increase of gas flow,the shortest time is the most when the gas flow Q=3L/min,and then the icing time gradually increases with the increase of gas flow,and the icing time is equal to that of-8 °C when Q increases to 5 L/min.When the pipe diameter was D=1 mm,it was observed that the freezing process of water without adding bubbles was the longest,and the freezing time was the shortest when the gas flow Q=5 L/min.(3)The influence of different working conditions on transparency is as follows: when the gas flow Q=0 L/min,Its K value is minimum and always 0 when the gas flow rate Q =0 L/min;When T=-10 °C and Q=1 L/min,the highest value of transparency K value was0.8;when the pipe diameter and temperature were constant,the overall change trend of K value was to increase first and then decrease with the increase of Q value;the influence of pipe diameter on transparency K value showed irregularity,and the peak value alternately appeared. |
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