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Handbook of air conditioning and refrigeration / Shan K

Handbook of air conditioning and refrigeration / Shan K

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10.54 CHAPTER TEN<br />

FIGURE 10.19 Thermostatic characteristics <strong>of</strong> sensing bulb: (a) limited liquid charge; (b) straight charge; (c)<br />

cross-charge.<br />

approximately equal. This prevents the refrigerant from flooding back to the compressor at higher<br />

evaporating temperatures.<br />

Hunting <strong>of</strong> Thermostatic Expansion Valve. Hunting is the quick cycling <strong>of</strong> maximum <strong>and</strong> minimum<br />

output <strong>of</strong> a controlled device. For the thermostatic expansion valve, hunting results from the<br />

over- or underfeeding <strong>of</strong> refrigerant to the evaporator. It causes temperature <strong>and</strong> pressure fluctuations<br />

<strong>and</strong> may reduce the capacity <strong>of</strong> the <strong>refrigeration</strong> system.<br />

The time lag <strong>of</strong> refrigerant flow through the evaporator to the sensing bulb may cause a continuous<br />

overshooting <strong>of</strong> the valve position. The overfed refrigerant may form unevaporated slugs. These

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