Log Mean Temperature Difference (LMTD)

LMTD for counter-flow / parallel-flow heat exchangers. The design temperature difference that goes into Q = U·A·LMTD.

Heat transfer

Hot fluid in°CHot fluid out°CCold fluid in°CCold fluid out°CFlow arrangement

ΔT at one end: 38.00K

ΔT at the other: 27.00K

LMTD: 32.19K

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

LMTD = \frac{\Delta T_1 - \Delta T_2}{\ln(\Delta T_1 / \Delta T_2)}

Symbol	Meaning	Unit
$\Delta T_1$ , $\Delta T_2$	Temperature differences at exchanger ends	K
$LMTD$	Log-mean temperature difference	K

Source: Incropera - Fundamentals of Heat and Mass Transfer

In short

LMTD for counter-flow / parallel-flow heat exchangers.

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