Orifice Size and the Dual Scale Design for the Nonlinear Alum Doser

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h5. Figure 1: Doser Overview

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Abstract:

During the fall semester of 2009, the Nonlinear Chemical Dosing Team developed the dual scale, orifice-based doser in order to be able to deliver both turbulent and laminar alum flow. Like its linear predecessor, this doser must automatically increase or decrease the alum solution to maintain a target dosage set by the operator as the plant flow changes. As an additional feature, the two different scales provide the operator with additional precision through a low dosage (5-25 mg/L) and a high (20-100 mg/L) alum dosage range. Refer to attached file Doser Diagrams and Dual Scale for editable files for diagram and dual scale.

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Head loss through orifices:

{latex}$$
h_{1Orifice}  = K_{DoseOrifice} {{V_{DoseTube}^2 } \over {2g}}
$${latex}

Other Head Losses:

Major Head Losses:

{latex}$$
h_{Lmajor}  = f {L\over {D}}{{V^2} \over {2g}}
$${latex}

Entrance Head Loss:

{latex}$$
h_{1Entrance}  = K_{Entrance} {{V^2 } \over {2g}}
$${latex}

The analysis of the head losses in the system can be seen in Nonlinear Theory.
The orifice equation, shown below, demonstrates the nonlinear relationship between flow rate and the change in head loss.

{latex}
\large
$$
Q = K_{vc} A_{or} \sqrt {2gh}
$$
{latex}

Where

{latex}\large$$Q $${latex}

= Flow Rate

{latex}\large$$h $${latex}

= Head Loss

{latex}\large$$A_{or} $${latex}

= Area of the Orifice

{latex}\large$$K_{vc} $${latex}

= Orifice Constant

Head loss in the plant after the entrance tank occurs in the rapid mixer, the flocculation tank, and the launders. The flow of water through the AguaClara plant can be effectively represented as a series of flow expansions, a subset of minor losses. . The table below lists the major sources of head loss in the plant.

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