The chilled-water plant at the University of Pennsylvania sends chilled water to the buildings at \(42^{\circ} \mathrm{F}\) and receives warmed water at \(55^{\circ} \mathrm{F}\). A refrigerant is vaporized in the refrigerant condenser at \(38^{\circ} \mathrm{F}\) as it removes heat from warmed water. The refrigerant is condensed to

a saturated liquid at \(98^{\circ} \mathrm{F}\). The condensing medium is water at \(85^{\circ} \mathrm{F}\), which is heated to \(95^{\circ} \mathrm{F}\) as it absorbs heat rejected from the refrigerant. The warmed condenser water is cooled in a cooling tower in which it is sprayed over a stream containing ambient air. Assume that the ambient air is at \(100^{\circ} \mathrm{F}\) and \(95 \%\) humidity on a hot summer day and is rejected at 100\% humidity. For Phase I of the plant, the cooling capacity is 20,000 tons.

(a) Calculate the flow rates of the chilled water and condenser water in \(\mathrm{gal} / \mathrm{min}\).

(b) Select a refrigerant and its operating pressures. Assuming an isentropic efficiency of \(70 \%\) for the compressor, determine the refrigerant flow rate and the brake horsepower for the compressor.

(c) Calculate the lost work and thermodynamic efficiency.

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100F. CW 100F Distillate 40.0 lbmol/hr Feed 70 mol% Vaporized lbmol/hr Liquid Side Stream 30.0 lbmol/hr nC6 40 nC8 30 nC10 30 100 Figure 10.38 Thermally coupled distillation process for Exercise 10.18. Steam 425F 425F 30.0 lbmol/hr