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Handbook of air conditioning and refrigeration / Shan K

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5.28 CHAPTER FIVE<br />

FIGURE 5.15 Various types <strong>of</strong> control valves: (a) Double-seated two-way valve; (b) single-seated three-way mixing valve; (c) singleseated<br />

three-way diverting valve; (d) butterfly valve.<br />

1. Equal-percentage valve. This control valve changes the water flow rate by a certain percentage<br />

for that same percentage <strong>of</strong> lift in the valve stem when the upstream versus downstream water<br />

pressure difference across the valve (its pressure drop) is constant.<br />

2. Linear valve. This control valve shows a directly proportional relationship between the flow rate<br />

<strong>and</strong> the lifting <strong>of</strong> the valve stem for a constant pressure drop.

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