A balanced counterflow heat exchanger has area 20 m² and overall heat-transfer coefficient 20 W/(m²·K). Each air stream has mass flow 0.4 kg/s and cp = 1000 J/(kg·K). The cold stream enters the exchanger at 280 K and the hot stream enters it at 300 K. The outlet temperature of the heated cold air, in K, is
290
Each heat-capacity rate is 0.4×1000 = 400 W/K, while UA = 400 W/K. Thus NTU = 1 and, for balanced counterflow, ε = NTU/(1+NTU) = 1/2. The cold outlet is 280+0.5(300−280) = 290 K.
Important Questions from Heat Exchanger Analysis
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