Project ForgeHeat Transfer
Convection & Radiation
GATE 2019
Hard
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).
57.72 K(± 0.5 accepted)
Explanation
Q=Cc(Tc,out−Tc,in)=1200×30=36000 W. Th,out=Th,in−Q/Ch=100−36000/2000=82°C. ΔT1=100−15=85, ΔT2=82−45=37. LMTD=(85−37)/ln(85/37)=48/0.8317≈57.72 K.
Source: GATE ME 2019 Session 2 (Set 3) (2019)
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