Structural design and optimization of refrigerated truck carriages

Structural design and optimization of the carriage
Structural design and optimization of refrigerated truck carriages
1.1 Design requirements

The designed refrigerated vehicle requires a rated load capacity of about 1 ton. The accepted chassis model is CGC1040HDD33E1, and the four walls of the carriage are required to have sufficient strength and stiffness to resist attack deformation; Has good cold and heat insulation effects; The material used in the carriage requires low density and light weight to increase the overall weight coefficient of the vehicle. The carriage has two functions: preservation and freezing. The preservation function requires a temperature inside the box of -5 ℃. The freezing function requires a temperature inside the box of -15 ℃. The refrigerated car uses a refrigeration unit for refrigeration, and the temperature field inside the entire carriage needs to be evenly distributed during refrigeration

1.2 Structural Design and Optimization

To meet the above requirements, the total size of the designed carriage is 4000 mm x 1800 mm x 1800 mm. Each wall panel and door of the carriage are made of a three-layer structure made of fiberglass steel sandwiched with hard polyurethane. To ensure the self loading and unloading requirements of the carriage, such as thermal insulation, durability, and resistance to attack and vibration, a fiberglass thickness of 3 mm is selected; The thickness of the rigid polyurethane board is tentatively set at 80 mm (the appropriate thickness will be discussed in Section 3); The whole carriage is composed of the front panel, bottom panel, side panel, door, evaporator, air guide plate, microporous film 1, and microporous film 2. The composition of the carriage and the assembly relationship of each department in the carriage are shown in Figure 1

In order to achieve assembly and coordination between the bottom plate, top plate, side plate, and front plate, a 45 ° wave mode slope is set at the edge of the plate. To enhance the overall strength and stiffness of the carriage and ensure careful adhesion between the layers of the carriage, reinforcement ribs are added between the fiberglass and polyurethane interlayers, which are divided into several U-shaped thin plates on one side of the inner and outer fiberglass plates. To ensure thermal insulation effect, The two U-shaped thin plates should be arranged in a staggered manner and set at a height of 30 mm to ensure that the total height of the two plates is less than the thickness of the polyurethane layer, in order to prevent contact and increase the thermal conductivity, thereby affecting the insulation effect.

In order to use a refrigeration unit to achieve average cooling during refrigeration, a guide structure is designed to guide the flow of cool air. The detailed structure is shown in Figure 3. The guide plate is used to guide the narrow and limited high-speed cool air at the evaporator outlet to the area with low air volume at the edge, expand the wind receiving area, and appropriately reduce the wind speed. The main function of the guide plate is to guide the cool air at the outlet to the edge of the carriage, The main function of the arc-shaped air guide plate is to concentrate the cool air above the carriage. Behind the arc-shaped air guide plate is a microporous film, which is evenly distributed by the micropores on the microporous film. This situation is suitable for fresh transportation, where the air volume does not need to be too large. The roof of the carriage can be seen as a cold plate, but due to the role of the evaporator and fan, the efficiency is higher than that of the cold plate. The microporous film material is polyethylene with an average network structure, The thermal conductivity is extremely low and it is not easy to form condensate. If the manufacturing process requirements allow, further adjustments can be made according to the actual transportation status. For example, when the carriage is long, the diffuse average microporous film will still pass through more cold air due to the large air volume near the air outlet, and the small air volume at the far air outlet will result in less or even no cold air. At this time