Reasons for local pressure loss in pneumatic conveying
? ? Local pressure loss plays an important role in the total pressure loss of pneumatic conveying. Next, let's work with the manufacturer of the pneumatic conveying system to understand the reasons for local pressure loss during the pneumatic conveying process. Overcoming local resistance will result in energy loss, and the resulting pressure loss can be understood as local pressure loss. Therefore, if we know the cause of local resistance, we will know the cause of local pressure loss. For specific pneumatic conveying devices, the manufacturer of the pneumatic conveying system has described in "What are the components of pressure loss in pneumatic conveying. Feeders, elbows, unloaders, and dust collectors are all sources of local pressure loss.
? ? The reason for this resistance can be summarized as follows: during the transportation process, the solid boundary undergoes rapid changes (such as rotation, contraction, fragmentation, etc.), and expands or passes through local obstacles (such as gate valves) due to the rapid changes in the internal velocity, direction, and distribution of the fluid. This local resistance can be divided into two types. One is to change the direction of flow, but maintain the same flow velocity, just like flowing through an elbow. Another type is the change in flow velocity. In practical applications, this change is often caused by changes in the geometric conditions of the pipeline, resulting in changes in the distribution of fluid velocity, the influence of fluid micro mass, and the exchange of mass between the main flow and vortices. Local resistance has various forms, such as: when the fluid passes through the expansion pipe, it flows from a small section to a large section, and the fluid particles do not suddenly rotate due to inertia. The fluid boundary gradually expands, and a vortex zone is formed at the expansion pipe; The friction between particles in the vortex zone will consume some energy; In the process of material exchange, friction and impact also consume some energy; In addition, when the fluid enters a large cross-section pipeline, the velocity changes and the velocity distribution reorganizes, which can also interfere with the fluid's movement and consume energy. These energy losses are actually the essence of local resistance.
? ? In other forms of local resistance, elbows, reducers, or tees are essentially the same. They are all caused by the viscosity of the gas, but the local resistance coefficient is different in the calculation. In addition, the size of the vortex region is related to the magnitude of local losses. The larger the vortex area, the greater the energy loss. Therefore, how to reduce the local pressure loss caused by local resistance is generally achieved by changing the geometric shape of the pipeline to avoid the impact of vortex zones and particles.