| With the deepening of China’s reform of economic system and the supply-front economics structural reform,the living standard of the residents had been increasing,and the demand for high nutritional value and perishable seasonal fruits and vegetables products were getting higher and higher.In the storage process due to the reasons of technical level and design ideas,cold air flow organization was unreasonable,inhomogeneous temperature distribution leads to spoilage of fruits and vegetables,that was why the annual refrigerating cabinets storage results in huge losses and waste.In recent years,the refrigeration industry and the academic session began to study how to optimize the air flow organization within the cold storage effectively,jacketed cold storage,as a new way of supplying the efficient air flow organization,concerned gradually.In this paper,the characteristics of the air flow organization in the jacketed-cold storage were studied in detail.The numerical simulation and experimental study were used to explore the effect of a variety of working conditions on the distribution of airflow on the air temperature of 0℃ in the jacketed-cold storage,such as different air supply speed,hydrostatic pressure box height and two kinds of return air modes,and the optimum air flow condition was used to study the pre-cooling time and storage quality of green cabbage.In the process of studying the subject,the numerical simulation software CFX was used to build the geometric model according to the real size of the jacketed-cold storage,the unstructured grid was built,and boundary conditions were set up,such as the jacket wall,the air outlet and the return air outlet.The air velocity and the temperature distribution of the jacketed cold storage in different working conditions were calculated,and the temperature distribution and flow field of the jacketed cold storage under different working conditions were explored.In the subsequent experiment,in the design of the jacketed cold storage,according to the numerical simulation of the corresponding conditions the experimental program were set,applying paperless recorder and T-type thermocouple on the jacket,the temperature of measuring point of the plane was collected and sorted,and the distribution of airflow in the jacketed library under various working conditions was explored.Through the comprehensive analysis of the simulation and experiment,the optimal air flow condition was obtained.Through the comprehensive analysis of the simulation and experiment,the optimal air flow condition is obtained.Under the optimum conditions,the fresh green cabbage was added into the jacketed cold storage,and the low temperature pre-acclimation experiment and storage quality experiment of green cabbage were carried out,and the effect of temperature distribution on the quality of green cabbage in the best condition was verified.The following conclusions are summarized:(1)In the working condition of applying the side of the return air outlet to return air,under the distance from the outlet distance was far and close to the floor position of the plane,the temperature at the center of the reservoir was lower than the temperature of the measuring point,and the temperature distribution from the upper part of the reservoir(z = 1.4m)to the height of the bottom of the reservoir(z = 0.2m)was gradually increasing.With the increasing height of the static pressure box,the uniformity of the temperature distribution in the jacket library was gradually enhanced,and the continuous increase of the jet velocity at the air outlet caused the uniformity of the airflow in the static pressure box,resulting in uniform distribution of the temperature distribution in the central area of the reservoir.The average difference of the maximum and minimum temperature in the library was 0.11°C,and the temperature distribution in the jacketed cold storage was better.(2)In the working condition of applying the bottom of the return air outlet to return air,under the distance from the outlet distance was close and away from the floor of the location of the measuring point,the temperature at the center of the reservoir was lower than the temperature of the measuring point,and the temperature distribution from the upper part of the reservoir(z = 1.4m)to the height of the bottom of the reservoir(z = 0.2m)was gradually increasing.With the increasing height of the static pressure box,the uniformity of the temperature distribution in the jacket library was gradually enhanced,and the continuous increase of the jet velocity at the air outlet caused the uniformity of the airflow in the static pressure box,resulting in uniform distribution of the temperature distribution in the central area of the reservoir.Under the G3 condition,the average difference of the maximum and minimum temperature in the library was 0.09°C,and the temperature distribution in the jacketed cold storage was better.(3)Compared to the bottom of the return air way and the side of the return air way,applying the bottom of the return mode,the central area of the library of air supply jet in the fruit and vegetable storage area could produce adherence rapidly,and the heat of the central area of the storage of green cabbage quickly was took away.The temperature of the core storage area was 0.27°C,which was lower than the temperature at the wall of the jacket.When the side of the return air way was applied,the wind speed of the return air in the reservoir was greater than the wind speed in the central area of the reservoir,and the average temperature of the storage core area was 0.31°C,which was higher than the average temperature at the wall of the jacket.(4)Through the experiment,it was found that under the conditions of the different height of static pressure box,the temperature distribution in the reservoir was similar to that of the two kinds of return air,and the temperature distribution in the bottom of the reservoir was decreasing,The temperature of the measuring point closer to the outlet was lower than the temperature of the measuring point near the return air outlet.There was a temperature difference between the center of the library and the temperature of the measured wall.Among them,the temperature distribution in the storage area of G3 was the most uniform,it was 0.09°C and the average temperature difference between the central point and the wall point was smallest.(5)The results of experiment and simulation showed that the static pressure box device and the even return air outlet in the jacket could effectively improve the airflow structure in the jacket library,compared with the traditional air storage organization,the temperature inside the jacket.The distribution was more uniform,the difference between the highest and lowest temperatures in the reservoir was small.(6)Analyzing and comparing of the simulation results and experimental data,the simulation results and experimental data between the error was small,the trend was basically the same,and verify the correctness of numerical simulation in this subject.(7)In the study condition of this subject,when the air supply temperature was 0°C,the air supply speed was 2 m/s,the height of the static pressure box was 200 mm,the air outlet area was 0.102 m2.The bottom of the layout of the return air return air,that was G3 condition,the air flow organization and temperature distribution was the best in the jacketed-cold storage,green cabbage basically was not bad basically,blade tip a small amount of browning,weight loss rate was 1.9%,and the quality of green cabbage was highest.(8)When the temperature was 0°C,the temperature in the jacket was higher than the freezing point temperature of green cabbage,and the temperature distribution in the jacket was uniform,which was beneficial to improve the storage quality and edible value of green cabbage. |
PDF Full Text Request