Flow distribution in manifolds
The flow in manifolds is extensively encountered in many industrial processes when it is necessary to distribute a large fluid stream into several parallel streams, or to collect them into one discharge stream, such as in fuel cells, heat exchangers, radial flow reactors, hydronics, fire protection, and irrigation.
[1][2][3] A key question is the uniformity of the flow distribution and pressure drop.
Traditionally, most of theoretical models are based on Bernoulli equation after taking the frictional losses into account using a control volume (Fig.
[4][5][6] A generalized model of the flow distribution in channel networks of planar fuel cells.
[6] Similar to Ohm's law, the pressure drop is assumed to be proportional to the flow rates.
Our observations show that the greater the velocity (or momentum), the more fluid fraction through the straight direction.
The question raised from the experiments by McNown[1] and by Acrivos et al.[2] Their experimental results showed a pressure rise after T-junction due to flow branching.
Furthermore, because the lower energy fluid in the boundary layer branches through the channels the higher energy fluid in the pipe centre remains in the pipe as shown in Fig.
Thus, mass, momentum and energy conservations must be employed together for description of flow in manifolds.
[10][11][12][13][14] Wang[7][8][9] recently carried out a series of studies of flow distribution in manifold systems.
The governing equations can be obtained for the dividing, combining, U-type and Z-type arrangements.
Similarly, one can obtain the governing equations of the combining, U-type and Z-type arrangement.
The present models have been extended into more complex configurations, such as single serpentine, multiple serpentine and straight parallel layout configurations, as shown in Fig.
Wang[15][16] also established a direct, quantitative and systematic relationship between flow distribution, pressure drop, configurations, structures and flow conditions and developed an effective design procedures, measurements, criteria with characteristic parameters and guidelines on how to ensure uniformity of flow distribution as a powerful design tool.
