冷库空气幕的实验研究及数值模拟
发布时间：2018-10-07 19:21
【摘要】：冷库是对货物进行低温贮藏用以保证库内货物品质的一类特殊建筑物。在冷库运行的过程中,考虑到人员进出、货物装卸等一系列的原因,进出口处因门的频繁开启,将产生强烈的热、质交换,外界热空气的侵入,势必会造成冷库内部温度的升高,冷量的损失,进而影响贮藏货物的品质。另外,大量的热湿交换也会使冷库内部蒸发器排管结霜,传热效率降低并最终导致库房温度上升。因此,我们通常会在冷库库门处设置一个空气幕装置,空气幕的组成包括通风机、风管、空气处理设备以及空气分布器等,贯流风机运转产生的射流,形成一道无形的门帘,用于阻隔外界环境和内部环境热质交换的发生,可以保证冷库内温度稳定,所形成的的空气幕还能起到防尘、防虫、防蝇的效果。然而现阶段对于冷库的试验研究都局限在空库的基础上,对实际装配货物的冷库的研究很少,导致很多试验结果应用到实际工厂后效果并不理想。因此,有必要对装配有货物的冷库内部气流组织进行研究,并对冷库流场优化。对于冷库研究的方法都是通过实际测量以及工程经验开展的,这种方式实际操作起来会比较麻烦,所测出来的结果也不准确,并且也不能得到完整且直观的内部流场图。随着计算机技术的普及,计算流体力学(Computational fluid dynamics,简称CFD)被渐渐应用于冷库空气幕的实验研究中,它具有低成本、高精度以及快速获得预测结果等优点,可以较准确地预测出冷库内部气流分布以及整个冷库的温度场、速度场。本课题研究主要通过计算流体力学对有货物的冷库进行数值模拟,并结合实验测量得出冷库气流分布以及内部流场的速度图、温度图,在此基础上验证空气幕能有效阻隔冷库门外热气流的侵入,保证货物的品质,旨在为今后冷库实际应用方面提供一定的参考依据。(1)以上海海洋大学食品学院C楼的小型冷库为模型,并在冷库内堆放货物堆垛,模拟冷库实际运行生产,选用标准k-ε双方程模型,将自然对流考虑在内,并采用更为精准的二阶迎风格式,冷库内货物则引入Ergun方程建立三维货物堆垛的多孔介质模型对其进行建模。稳态模拟出冷库内的气流分布、温度场以及速度场。(2)将冷库门开启,通过计算流体力学对小型试验冷库进行库门开启后1min内的非稳态模拟,预测冷库内部流场分布情况。结果表明:库内气流温度场及速度场都处于稳定状态,此时随着库内开启,外界热气流不断入侵到库内,和库内冷气流发生热量交换,导致冷库气温升高2-4℃,影响货物品质。(3)在冷库门开启1min后,热量大量充斥冷库内,此时将冷库门上的空气幕开启,对空气幕开启后1min内进行非稳态模拟。研究验证了空气幕确实能隔绝冷库内外气流热量交换的作用,随着空气幕的开启,侵入的冷库的热气流被隔绝在门外,约50 s后整个冷库逐渐恢复到理想状态。
[Abstract]:Cold storage is a kind of special building which can store the goods at low temperature to ensure the quality of the goods in the store. During the operation of the cold storage, taking into account a series of reasons, such as the entry and exit of persons, cargo handling, etc., because the doors are frequently opened, there will be intense heat and mass exchange, and the external hot air will invade. It will cause the increase of internal temperature and the loss of cold quantity, which will affect the quality of storage goods. In addition, a large amount of heat and moisture exchange will cause frosting of the evaporator in the freezer, which will reduce the heat transfer efficiency and eventually lead to the rise of the temperature in the storage room. As a result, we usually install an air curtain at the door of the freezer. The air curtain consists of a fan, a duct, an air handling device, an air distributor, and so on. The jet produced by the running of the tubular fan forms an invisible curtain on the door. It can be used to prevent the heat and mass exchange in the outside environment and the internal environment, which can ensure the stability of the temperature in the cold storage, and the air curtain can also play the effect of dust, insect and fly control. However, at present, the research on cold storage is limited on the basis of empty storage, and there is little research on the cold storage of the actual assembled goods, which leads to a lot of test results being applied to the actual factory and the effect is not satisfactory. Therefore, it is necessary to study the internal airflow organization and optimize the flow field of the cold storage. The methods of cold storage research are carried out through actual measurement and engineering experience. The practical operation of this method will be more troublesome, the measured results are also inaccurate, and can not obtain a complete and intuitive internal flow field diagram. With the popularization of computer technology, Computational fluid Dynamics (Computational fluid dynamics,) has been gradually applied to the experimental research of air curtain in cold storage. It has the advantages of low cost, high precision and fast prediction results. The airflow distribution in the cold storage and the temperature field and velocity field of the whole cold storage can be predicted accurately. In this paper, the numerical simulation of the cold storage with cargo is carried out by computational fluid dynamics, and the velocity diagram and temperature diagram of the air flow distribution and the internal flow field of the cold storage are obtained by combining the experimental measurements. On this basis, it is verified that the air curtain can effectively prevent the invasion of the hot air flow outside the freezer and ensure the quality of the goods. In order to provide some reference for the practical application of cold storage in the future. (1) taking the small cold storage in C Building of Shanghai Ocean University as the model, and stacking goods in the cold storage, simulating the actual operation and production of the cold storage, The standard k- 蔚 two-equation model is used to take natural convection into account, and a more accurate second-order upwind scheme is adopted. The Ergun equation is introduced into the freezer to establish the porous media model for three-dimensional cargo stacking. The airflow distribution, temperature field and velocity field in the cold storage are simulated in steady state. (2) the cold storage door is opened, and the unsteady state simulation in the 1min after the opening of the cold store is carried out by computational fluid dynamics to predict the distribution of the flow field in the cold storage. The results show that the temperature field and velocity field of the air flow in the reservoir are in a stable state. At this time, with the opening of the reservoir, the external heat flow continuously invades into the reservoir, and the heat exchange occurs with the cold flow in the reservoir, which results in the temperature of the cold storage rising 2-4 鈩，
本文编号：2255383
[Abstract]:Cold storage is a kind of special building which can store the goods at low temperature to ensure the quality of the goods in the store. During the operation of the cold storage, taking into account a series of reasons, such as the entry and exit of persons, cargo handling, etc., because the doors are frequently opened, there will be intense heat and mass exchange, and the external hot air will invade. It will cause the increase of internal temperature and the loss of cold quantity, which will affect the quality of storage goods. In addition, a large amount of heat and moisture exchange will cause frosting of the evaporator in the freezer, which will reduce the heat transfer efficiency and eventually lead to the rise of the temperature in the storage room. As a result, we usually install an air curtain at the door of the freezer. The air curtain consists of a fan, a duct, an air handling device, an air distributor, and so on. The jet produced by the running of the tubular fan forms an invisible curtain on the door. It can be used to prevent the heat and mass exchange in the outside environment and the internal environment, which can ensure the stability of the temperature in the cold storage, and the air curtain can also play the effect of dust, insect and fly control. However, at present, the research on cold storage is limited on the basis of empty storage, and there is little research on the cold storage of the actual assembled goods, which leads to a lot of test results being applied to the actual factory and the effect is not satisfactory. Therefore, it is necessary to study the internal airflow organization and optimize the flow field of the cold storage. The methods of cold storage research are carried out through actual measurement and engineering experience. The practical operation of this method will be more troublesome, the measured results are also inaccurate, and can not obtain a complete and intuitive internal flow field diagram. With the popularization of computer technology, Computational fluid Dynamics (Computational fluid dynamics,) has been gradually applied to the experimental research of air curtain in cold storage. It has the advantages of low cost, high precision and fast prediction results. The airflow distribution in the cold storage and the temperature field and velocity field of the whole cold storage can be predicted accurately. In this paper, the numerical simulation of the cold storage with cargo is carried out by computational fluid dynamics, and the velocity diagram and temperature diagram of the air flow distribution and the internal flow field of the cold storage are obtained by combining the experimental measurements. On this basis, it is verified that the air curtain can effectively prevent the invasion of the hot air flow outside the freezer and ensure the quality of the goods. In order to provide some reference for the practical application of cold storage in the future. (1) taking the small cold storage in C Building of Shanghai Ocean University as the model, and stacking goods in the cold storage, simulating the actual operation and production of the cold storage, The standard k- 蔚 two-equation model is used to take natural convection into account, and a more accurate second-order upwind scheme is adopted. The Ergun equation is introduced into the freezer to establish the porous media model for three-dimensional cargo stacking. The airflow distribution, temperature field and velocity field in the cold storage are simulated in steady state. (2) the cold storage door is opened, and the unsteady state simulation in the 1min after the opening of the cold store is carried out by computational fluid dynamics to predict the distribution of the flow field in the cold storage. The results show that the temperature field and velocity field of the air flow in the reservoir are in a stable state. At this time, with the opening of the reservoir, the external heat flow continuously invades into the reservoir, and the heat exchange occurs with the cold flow in the reservoir, which results in the temperature of the cold storage rising 2-4 鈩，
本文编号：2255383
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