What is the definition of a flow dead zone?
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What is the definition of a flow dead zone?
In short, it means there is no flow.
The fluid flows slowly in this area or is unable to flow out due to rotation. The fluid in the dead zones contributes nothing to heat transfer, and scaling tends to occur in the flow channels under low flow rates. Therefore, the presence of dead zones in the equipment should be minimized as much as possible.
A local region within a flow system, in which the fluid does not essentially participate in the main flow but only moves locally in place. The residence time of the fluid at the dead zone is infinitely long. Dead zones should be avoided in chemical processing equipment, as they not only reduce the available space for effective use of the equipment but can also lead to accidents. For example, the material at the reactor dead zone may undergo excessive reaction, leading to incidents such as coking.
A dead zone arises due to the design of pipes or valves, resulting in liquid swirling or very limited flow within them; in most cases, it is liquid swirling that causes this issue. Under normal pressure conditions, clean fluids do not cause excessive damage to equipment. However, as temperature and pressure increase, their destructive effects become significant. For example, in 60MW supercritical units, where the main steam operates at 25 PMa and a temperature of around 575 degrees, a significant dead zone can cause pipes or valves made of F92 material to wear out and burst within a few hours