Container jacket

Thread Content

Common media used in jackets include steam, heat transfer oil, cooling water, and vacuum insulation materials. The purpose of using a jacket is generally to heat or cool the container and its contents, and it can also serve as a sealed, insulated chamber for the container. 01 Overall jacket: The overall jacket comes in U-shaped and cylindrical types. A U-shaped jacket has jackets surrounding both the cylindrical section and the lower head, resulting in a large heat transfer area. The cylindrical jacket has a jacket only on the cylindrical portion, resulting in a small heat transfer area; it is suitable for applications with low heat transfer requirements. When hot and cold media flow through the jacket, their flow cross-sectional area is the annular area between the jacket and the cylinder; due to this large flow area, the flow velocity is low, resulting in relatively poor heat transfer performance. The inner cylinder requires pressure calculations for both internal and external pressures according to design requirements; for example, when the inner cylinder is under negative pressure while the jacket cylinder is under positive pressure, the pressure it must withstand is that of the jacket plus the inner cylinder. Generally, the wall thickness of the inner cylinder is increased accordingly as a result of these calculations. It is generally used in situations where the heat transfer requirement is low. The flow area inside the jacket is large, the flow velocity is slow, the temperature gradient changes little, resulting in high heat losses and poor heat transfer performance. As the volume increases, the inner tube wall must be thickened to withstand external pressures and prevent instability; however, this increased wall thickness makes the equipment bulkier and reduces its heat transfer efficiency. 02 Semi-tube jacket: The semi-tube is welded and fixed to the container body in a spiral winding manner; the spiral semi-tube can be a single semi-tube or two semi-tubes wound side by side (dual-channel). The half-tube cross-section can be a semi-circular ring cross-section or an arcuate ring cross-section. The advantage of the semi-tube jacket is that, as the container body is reinforced by the semi-tube jacket, it is possible to reduce the wall thickness of the body under jacket pressure; this results in significant material savings, especially for large-diameter containers. Furthermore, the half-tube jacket can be used in working conditions with higher pressures (the jacket pressure can reach up to 6.3 MPa). The disadvantage is that the welding seam between the jacket and the main body is long, and high precision is required for jacket shaping, which thus increases manufacturing costs to some extent. It has a superior heat transfer performance: the medium flows over a larger area within the overall jacket, resulting in a slower flow rate and an easier tendency to form short circuits; hence, its heat transfer efficiency is less satisfactory in situations where rapid cooling is required. In contrast, the semi-tube jacket has a smaller area, allowing for a faster flow rate of the medium and thus better heat transfer performance. 03 Honeycomb Jacket: The honeycomb jacket evolved from the conventional integral jacket by incorporating punching and short tube reinforcement measures. Due to the small flow area in the honeycomb jacket, the flow velocity of the fluid within it increases; under the same flow rate, this velocity is 3 to 10 times higher compared to that in a conventional jacket. Due to the numerous honeycomb pores on its outer surface, the stress conditions on the welds are complex; as a result, the inner cylinder deforms easily when welded to the jacket, leading to weld cracks and leaks. After colliding with the honeycomb points multiple times, the fluid forms local eddies. At this point, the numerous honeycomb structures within the jacket interfere with the flow of the fluid; as the fluid passes through these honeycomb points, its flow is disrupted, causing changes in both the direction and speed of the flow. This results in turbulence, which destroys or thins out the original laminar flow layer, thereby accelerating heat exchange and improving the efficiency of heat transfer. Overall jacket: It has a large heat transfer area and a large flow area, resulting in a low flow velocity; its heat transfer performance is relatively poor. Generally, the wall thickness of the inner cylinder is relatively thick, and it is used in situations where low heat transfer requirements exist. Semi-tube jacket: The advantage is that the container body is reinforced by semi-tubes, which allows the wall thickness of the body to be reduced; this results in significant material savings for containers with large diameters. The disadvantage is that the welding seam between the jacket and the main body is long. The semi-tube jacket has a small area, allowing for fast fluid flow and thus excellent heat transfer performance. Honeycomb jacket: The stress conditions on the welds are complex; the inner cylinder is prone to deformation during welding, which can lead to weld cracks and subsequent leaks. The honeycomb structure acts as a perturbation to the fluid flow within the jacket; as the fluid passes through the honeycomb cells, its flow is disrupted, which accelerates heat exchange and improves the efficiency of heat transfer.