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Handbook of air conditioning and refrigeration / Shan K

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Therefore, from Eq. (13.12) the evaporating temperature at 50 percent part-load operation is<br />

T ev � eB T el � T ee<br />

e B � 1<br />

� e0.663 � 44 � 49<br />

e 0.663 � 1<br />

For part-load operation at a load ratio <strong>of</strong> 0.5, T ev rises 38.69 � 36 � 2.69°F (1.5°C).<br />

Temperature Lift at Part-Load Operation for Centrifugal Chillers<br />

REFRIGERATION SYSTEMS: CENTRIFUGAL 13.29<br />

� 38.69�F (3.72�C)<br />

Figure 13.12 is a diagram <strong>of</strong> temperature lift at various load ratios for a centrifugal chiller using<br />

HCFC-123 as refrigerant. The chilled water temperature leaving the chiller is maintained at 44°F<br />

(6.7°C) at all load ratios, <strong>and</strong> the outdoor wet-bulb temperature also remains constant at 75°F<br />

(23.9°C) when the load ratio varies from 0 to 1. Fouling factors for both evaporator <strong>and</strong> condenser<br />

are 0.00025 h�ft 2 �°F/Btu (0.000044 m 2 �C/W).<br />

FIGURE 13.12 Temperature lift at various load ratios <strong>of</strong> a centrifugal chiller.

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