8-548.74 (cont’d) Energy balance on cooler-reheaterReferences: Same as Fig. 8.4-2 [including H2O(l, 32oF)] Substance ininˆmH±outoutˆ±Fresh air feed 10.93 45.5— — DAmin lb dry air/minm±Recirculated air feed 65.57 26.2— — airmˆin Btu/lb dry airHDelivered air — — 76.5 21.4 2HO(l)min lb /minm±Condensed water (49oF) — — 0.165 17.02(l)mˆin Btu/lbHiioutin575.3 Btu60 min1 ton coolingˆˆ2.9 tonsmin1 h-12,000 Btu/hQHmHmH−=Δ =−==∑∑±±±±Percent saved by recirculating = (9.1 tons2.9 tons)100%68%9.1 tons−×=Once the system reaches steady state, most of the air passing through the conditioner is cooler than the outside air, and (more importantly) much less water must be condensed (only the water in the fresh feed). c. Total recirculation could eventually lead to an unhealthy depletion of oxygen and buildup
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This note was uploaded on 01/07/2012 for the course CH E 210 at Pennsylvania State University, University Park.