Question
Hot and cold fluids enter a parallel flow double tube heat exchanger at 100°C and 15°C, respectively. The heat capacity rates of hot and cold fluids are Ch = 2000 W/K and Cc = 1200 W/K, respectively. If the outlet temperature of the cold fluid is 45°C, the log mean temperature difference (LMTD) of the heat exchanger is ________ K (round off to two decimal places).
Answer :
57.71
Ch = 2000 W/K
Cc = 1200 W/K
By energy equation, Ch (ΔTh ) = Cc (ΔTc )
2000 (100 – Tho) = 1200 (30)
Tho = 82°C
LMTD = {(100 - 15) - (82 - 45)}/ ln{(100-15)/(82-45)} = 57.71°C
Since LMTD is temperature difference so the answer will be 57.71 K
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