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10-58) An air preheater for a power plant consists of a cross-flow heat exchanger with hot exhaust gases used to heat incoming air at I atm and 300 K. The gases enter at 375°C with a flow rate of 5 kg/s. The airflow rate is 5.0 kg/s, and the heat exchanger has A = 110 m2 and U = 50 W/m2 oC. Calculate the heat-transfer rate and exit temperatures for two cases, both fluids unmixed and one fluid mixed. Assume the hot gases have the properties of air.
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