| Thermodynamics
Table of Contents In heat exchanger applications, the inlet and outlet temperatures are commonly specified based on the fluid in the tubes. The temperature change that takes place across the heat exchanger from the entrance to the exit is not linear. A precise temperature change between two fluids across the heat exchanger is best represented by the
log mean temperature difference (LMTD or ΔTlm), defined in Equation
below. ΔT1m = (ΔT2
- ΔT1) /
[ ln(ΔT2/ ΔT1) ] where: ΔT2 = the larger temperature difference between the two fluid streams at either the entrance or the exit to the heat exchanger ΔT1 = the smaller temperature difference between the two fluid streams at either the entrance or the exit to the heat exchanger
Reference:
DOE-HDBK-1012/1-92 JUNE 1992, THERMODYNAMICS, HEAT TRANSFER, AND FLUID FLOW
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