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From Experiment to Theory: Why do fluids prefer straight pipes to side pipes?
In most industrial processes, the flow behavior of fluids is important in many aspects. This is particularly common when large fluid flows need to be distributed into multiple parallel flow paths and recycled into a single discharge stream. , such as fuel cells, plate heat exchangers, radial flow reactors and irrigation systems, etc. In these systems, the manifold is not only an important component, but its flow distribution and pressure drop uniformity are always key issues of concern.
Traditionally, most theoretical models are based on Bernoulli's equation, taking friction losses into account.
The types of headers can usually be divided into four types: diverging headers, converging headers, Z-shaped headers and U-shaped headers. To a large extent, the performance of these header designs affects the efficiency of the fluid. In past studies, including controllable flow types and T-joints, to address fluid flow in headers, researchers have often used control volumes to understand friction losses, which has a long history in fluid dynamics. .
The conservation laws of mass, momentum, and energy must work together to describe flow in a header.
In recent years, Wang has conducted a series of studies on flow distribution and unified the main models into a theoretical framework to develop the most general model, focusing on how to integrate experimental observations into theoretical derivation. In fact, when the flow rate is too fast, the flow of fluid in the straight pipe shows obvious advantages, while the split flow in the side pipe is not as expected. From many experimental results, it is not difficult to find that the pressure of the fluid at the T-shaped joint increases precisely because of the inertial effect of the fluid, which makes the fluid prefer the straight direction.
Therefore, the higher the flow rate, the greater the fluid component in the straight pipe may be.
In flow theory, an interesting observation is that as the flow velocity increases, due to the influence of the boundary layer, most of the lower energy fluid will tend to pass through the side tubes, while the high-speed fluid will stay in the tube center. This phenomenon leads us to rethink the discrepancy between actual and predicted behavior of fluids in multi-inlet collective piping systems.
For the flow in the header, under different configurations and flow conditions, we found that it can be described by a series of equations, and the flow characteristics of each structure also reflect its unique design requirements. Wang's research results provide a complete mathematical model showing how to predict and analyze fluid flow in these multi-inlet systems and develop effective design criteria and guidelines.
Today's models have been extended to more complex configurations, demonstrating the critical role fluid engineering plays in modern industry.
Overall, these new discoveries not only add important theoretical foundations to our basic understanding, but also promote the application of fluid mechanics in complex systems. Through these studies, we may be able to better design parallel flow paths or systems with more complex conditions, such as single or multiple zigzag configurations, and straight parallel layouts. As the thinking of fluid design becomes more perfect, the relationship between fluid flow and system efficiency will be more established.
In the world of fluid flow, how many unknown mysteries are waiting for us to explore and understand?
