Log Mean Temperature Difference with Correction Factors
Calculate LMTD and correction factors for various flow arrangements
Counter-current flow provides the most efficient heat transfer with the highest LMTD.
P = (t2-t1)/(T1-t1)
R = (T1-T2)/(t2-t1)
ΔT1
40.0 °C
ΔT2
60.0 °C
LMTD (Theoretical)
49.3 °C
Corrected LMTD
49.3 °C
For heat transfer calculations: Q = UA × F × LMTD
Effectiveness
0.67
Capacity Ratio
1.0
The LMTD is the logarithmic average of the temperature differences between the hot and cold streams at each end of the heat exchanger. For counter-current flow:
LMTD = (ΔT1 - ΔT2) / ln(ΔT1/ΔT2)
For flow arrangements other than pure counter-current or co-current, a correction factor (F) is applied to the LMTD. The F factor depends on the geometry and the dimensionless parameters P and R:
Counter-current flow typically gives the highest LMTD and most efficient heat transfer. Co-current flow has lower LMTD but more uniform wall temperatures. Shell-and-tube and cross-flow exchangers require correction factors typically between 0.7-0.95.
