Project ForgeHeat Transfer
Convection & Radiation
GATE 2020
Medium
In a concentric tube counter-flow heat exchanger, hot oil enters at 102°C and leaves at 65°C. Cold water enters at 25°C and leaves at 42°C. The log mean temperature difference (LMTD) is __________ °C (round off to one decimal place).
49.3 °C(± 0.5 accepted)
Explanation
ΔT1=102−42=60°C, ΔT2=65−25=40°C. LMTD=(ΔT1−ΔT2)/ln(ΔT1/ΔT2)=(60−40)/ln(60/40)=20/0.4055≈49.3°C.
Source: GATE ME 2020 Session 1 (ME-1) (2020)
This question is part of a 15-day revision cycle — sign in and Project Forge will bring it back the day before you'd forget it.