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Handbook of air conditioning and refrigeration / Shan K

Handbook of air conditioning and refrigeration / Shan K

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REFRIGERATION SYSTEMS: RECIPROCATING, ROTARY, SCROLL, AND SCREW 11.45<br />

FIGURE 11.26 (a) Scroll compressor <strong>and</strong> (b) scroll compression processes. (Source: ASHRAE <strong>H<strong>and</strong>book</strong> 1996,<br />

HVAC Systems <strong>and</strong> Equipment. Reprinted with permission.)<br />

In one type <strong>of</strong> radial compliance, the orbiting scroll is mounted on the sliding unloader bushing<br />

that is fitted onto the eccentric pin <strong>of</strong> the motor shaft <strong>and</strong> thus directs the radial motion <strong>of</strong> the<br />

orbiting scroll in <strong>and</strong> out to accommodate variations in orbit radius due to discrepancies. Radial<br />

compliance allows the scroll members to separate in the presence <strong>of</strong> liquid refrigerant or debris <strong>and</strong><br />

increases system reliability.<br />

Axial compliance is accomplished by an adjustable axial pressure that provides sealing contact<br />

between the scroll tips <strong>and</strong> bases when the scroll is orbiting. This pressure is released when the<br />

orbiting scroll ceases to operate. As the scroll tip bears directly on both the baseplates <strong>and</strong> the lubrication<br />

oil between the scroll <strong>and</strong> the plates, both form an effective oil seal.

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