CFD software is short for Computational fluid Dynamics software, which is specially used for the analysis, calculation and prediction of flow field. Through CFD software, the phenomena occurring in the flow field can be analyzed and displayed, the performance can be predicted in a relatively short time, and the best design effect can be achieved by changing various parameters. CFD numerical simulation can enable us to have a deeper understanding of the mechanism of the problem, provide guidance for the experiment, save the manpower, material resources and time required for the experiment, and play a good guiding role in the sorting out of the experimental results and the drawing of the law.
The main purpose of using CFD simulation for this project is to verify the air flow organization, velocity field and temperature field distribution in the confined space on the basis of the preliminary design. The project adopts jet permeation air supply mode to calculate and simulate the airflow organization status of the warehouse shelf area (refer to dwg drawings for details).
Architectural overview：
The project name is a tobacco product warehouse project. In order to facilitate modeling and calculation, the real warehouse size was simplified during modeling, and only the key area of air flow organization was modeled. The size of the simulated space was length × width × height (Z×X×Y) =101m×28.7m×23.5m.
The model is shown in figure：
Figure 1 Model structure
Main parameter setting：
1． The fiber air supply pipe is round, with a total of 6, two in a row, and a total of three rows. It is installed above the shelf and below the ceiling. The diameter of the air pipe is 800mm, the length of the pipe is 46m, and the air volume is 12000CMH (m3/h). For ease of modeling, the tube length is slightly different from the actual length.
2．Choose K-E equation model, ideal incompressible gas.
4．The opening direction of the top row of air ducts is 6:00.
5．The air supply temperature is 290K (17℃).
6．The return air outlet is located at the lower part of the finished product warehouse, with a total of 6 return air outlets.
7．Setting of boundary conditions: constant heat flux boundary conditions are adopted in the adjacent non-air-conditioned area, and constant wall temperature boundary conditions are adopted in the adjacent air-conditioned area. The influence of personnel load is considered when setting the ground boundary conditions, and additional heat flow caused by personnel activities is added on the basis of maintaining the structural heat flux. The roof increases the additional heat flow from the heat dissipation of the lighting equipment.
Modelling：
Figure 2 Grid division
Computation：
Velocity field profile curve of model section：
（X=20m）
Note: Part of the value on the left is explained, for example, 0.00e+00 means 0.00×100 (i.e. 0.00); 2.00e-01 indicates 2.00 x 10-1 (that is, 0.2), in m/s. (X=50m)
(X=70m)
The above three figures show the cross section velocity distribution of cold air from the fiber air duct. After the air supply is emitted, it enters the lower warehouse through the corridor between the shelves. The air flow enters the warehouse area and begins to sink, enrolling, and rapidly attenuates, forming an induced air supply, which can increase the mixing speed between the air flow in the warehouse and reduce the vertical temperature difference. From the above three figures, the wind speed distribution in different sections along the Z direction is basically similar. On the whole, the wind speed distribution along the Z direction is more uniform.
Profile curve of temperature field in model section：
（X=20m）
Note: The value on the left side explains that the value represents the same velocity graph, for example 2.90e+02 means 2.90×102 (i.e. 290); The unit is Kelvin (K) and the unit conversion relation is (t+273.15) K=t ° C (X=50m).
(X=70m)
The above three figures are temperature distribution maps taken at different locations along the X direction. The overall temperature distribution is relatively uniform, there is not much fluctuation, and the temperature distribution in the active area below the air duct meets the temperature requirements on the whole. From the three intercepted diagrams, the temperature changes along the X direction are close, and it can be considered that the temperature distribution along the length direction of the air duct is uniform.
Velocity field profile curve of model section：
（Y=2.3m）
（Y=14.35m）
The above two pictures are the sections intercepted along the Y direction. The air flow is sent from the jet hole of the fiber air duct into the warehouse through the corridor between the shelves, and finally reaches each gap area of the shelves. Because the shelves are dense, the air flow begins to settle below the duct, the speed continues to decrease, and gradually permeates into the gaps of the shelves, the wind speed in the active area is about 0.1~0.25m/s, and the wind speed in the active area is basically the same.
From the above two figures, the wind speed distribution of each section along the Y direction of the warehouse is relatively similar, and the wind speed at the end is basically maintained at about 0.1~0.25m/s, meeting the wind speed requirements.
Profile curve of temperature field in model section：
（Y=2.3m）
(Y=14.35m)
The above two pictures show the temperature distribution sections captured along the X direction, indicating the trend of temperature change. The profile temperature gradient distribution can be seen. Overall, the temperature distribution of the shelf area is basically consistent, which can meet the environmental requirements in the warehouse.
It can be seen from the above figure that the temperature distribution of each section along the Z direction is basically similar, and the variation range is within 2℃, which meets the design temperature requirements as a whole.
The results of the above simulation are obtained at a certain indoor and outdoor initial temperature, and after the corresponding simplification (such as the hole is simplified into a slit, personnel, equipment lighting heat attached to the enclosure structure), and the simulation process considers the space closed and other conditions. The actual air supply process may vary. Different outdoor weather conditions, the number of warehouse personnel, the inventory capacity of goods, the degree of opening of doors and Windows, and the local heat flow caused by equipment heating conditions will also lead to differences in the indoor thermal environment. However, the overall speed and temperature variation trend are relatively accurate, and the simulation results can be used to assist the design of fiber air duct and provide some guidance for its effect verification.