LMTD Calculator — सूत्र
## Log-Mean Temperature Difference
The LMTD is the effective average temperature difference between the hot and cold streams across a heat exchanger. It accounts for the fact that the temperature difference varies along the length.
### Formula
**LMTD = (delta_T1 - delta_T2) / ln(delta_T1 / delta_T2)**
For counter-flow: delta_T1 = T_hot_in - T_cold_out, delta_T2 = T_hot_out - T_cold_in.
For parallel-flow: delta_T1 = T_hot_in - T_cold_in, delta_T2 = T_hot_out - T_cold_out.
Counter-flow always gives a higher LMTD (and thus smaller exchanger area) than parallel-flow.
The LMTD is the effective average temperature difference between the hot and cold streams across a heat exchanger. It accounts for the fact that the temperature difference varies along the length.
### Formula
**LMTD = (delta_T1 - delta_T2) / ln(delta_T1 / delta_T2)**
For counter-flow: delta_T1 = T_hot_in - T_cold_out, delta_T2 = T_hot_out - T_cold_in.
For parallel-flow: delta_T1 = T_hot_in - T_cold_in, delta_T2 = T_hot_out - T_cold_out.
Counter-flow always gives a higher LMTD (and thus smaller exchanger area) than parallel-flow.
हल किया गया उदाहरण
Hot fluid: 150→90°C, Cold fluid: 30→70°C.
- Counter-flow: delta_T1 = 150 - 70 = 80°C, delta_T2 = 90 - 30 = 60°C
- LMTD = (80 - 60) / ln(80/60) = 20 / ln(1.333) = 20 / 0.2877 = 69.52°C
- Parallel-flow: delta_T1 = 150 - 30 = 120°C, delta_T2 = 90 - 70 = 20°C
- LMTD = (120 - 20) / ln(120/20) = 100 / ln(6) = 100 / 1.7918 = 55.80°C