Flow Control Through Branches

The flow through branches A, B, and C in Figures 1 and 4 is dependent on the individual branch characteristics. When parallel branches are connected to a pump, the resulting division of flow may not satisfy the requirements of the individual lines. If it is desired that the flow to each branch meet or exceed specified individual line requirements, it is necessary only to select a pump to provide the maximum head required by any one branch. In those branches where this head is more than required, the flow will be greater than the desired amount. A throttling valve or other flow-restricting device may be used to reduce the flow in these branches to the desired quantity. If the flow is controlled in this manner, the pump need be selected to produce only the minimum total system flow at a total head required to satisfy the branch needing the highest head at junction 1 in Figures 1 and 4.

The flow through a branch is sometimes dictated by the requirement of a component elsewhere in the system. For example, in the system shown in Figure 10, the required flow through component V could be greater than the sum of the required flows through components A, B, and C. An additional branch line and control valve F around components A, B, and C may be used to bypass the additional flow needed by component D. Individual component throttling valves may also be used, if needed, to adjust the flow in each branch.

The following example illustrates how flow through branches may be controlled and how pump total head is calculated.

FIGURE 10 Example of a branch-flow pumping system

FLOW, m3/h

O 200 400 600 800

FLOW, m3/h

O 200 400 600 800

FLOW, GPM

FIGURE 11 System-head curves required for solutions to example problems

FLOW, GPM

FIGURE 11 System-head curves required for solutions to example problems example A pump is required to circulate water at a rate of 3600 gpm (817 m3/h) through the system shown in Figure 10. The head versus flow characteristics of the system components A, B, C, D, and E (system pipe and fittings) are shown in Figure 11. The branch pipe and fitting losses from point 1 to point 2 are included in the total heads for components A, B, and C. Determine

1. The pump total head required and the individual flows through components A, B, and C

2. The pump total head required if the flow through components A, B, and C need be only 800, 700, and 1000 gpm (182, 159, and 227 m3/h), respectively, and a bypass F is installed

Calculate the individual throttling valve head drops to achieve a controlled branch flow system.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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