Effectiveness ε of a heat exchanger from NTU and capacity-rate ratio Cr, for counter-flow and parallel-flow.
Formula
$$ \varepsilon_\text{counter} = \frac{1 - e^{-NTU(1 - C_r)}}{1 - C_r \cdot e^{-NTU(1-C_r)}} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $UA$ | Overall conductance × area | kW/K | heat-exchanger design |
| $C_\text{min}$ | Smaller of (m·cp) on each side | kW/K | fluid spec |
| $NTU$ | Number of transfer units | - | derived |
| $ε$ | Effectiveness | - | result |
Sources
- Kays & London - Compact Heat Exchangers.