ChemCalc implements the ε-NTU (effectiveness–Number of Transfer Units) method for heat exchanger rating and sizing. Given the stream capacities, NTU (or UA), and inlet temperatures, it computes outlet temperatures, heat duty, and effectiveness for five standard flow arrangements.
Supported Flow Arrangements
Counter-flow Parallel-flow (co-current) Shell-and-tube 1-2 (TEMA E) Cross-flow, both streams unmixed Cross-flow, C_max mixedInputs
| Parameter | Notes |
|---|---|
| Hot stream capacity C_h (W/K) | = ṁ · Cp for the hot side |
| Cold stream capacity C_c (W/K) | = ṁ · Cp for the cold side |
| NTU or UA (W/K) | NTU = UA / C_min |
| Hot inlet T_hi (°C) | Hot stream entering temperature |
| Cold inlet T_ci (°C) | Cold stream entering temperature |
| Flow arrangement | Select from the five types above |
Outputs
- Effectiveness ε — Q / Q_max
- Hot outlet T_ho (°C)
- Cold outlet T_co (°C)
- Heat duty Q (kW)
- Capacity ratio C_r = C_min / C_max
ε-NTU Formulas (per Incropera 7th Ed. §11)
| Arrangement | ε formula |
|---|---|
| Counter-flow | ε = (1 − e−NTU(1−Cr)) / (1 − Cr·e−NTU(1−Cr)) |
| Parallel-flow | ε = (1 − e−NTU(1+Cr)) / (1 + Cr) |
| Shell-tube 1-2 (TEMA E) | ε = 2 / (1 + Cr + √(1+Cr²) · coth(NTU√(1+Cr²)/2)) |
| Cross-flow, unmixed | ε ≈ 1 − exp(NTU0.22(e−Cr·NTU0.78−1)/Cr) |
| Cross-flow, C_max mixed | ε = (1/Cr)(1 − e−Cr(1−e−NTU)) |
Also Available: LMTD and HX Area
ChemCalc also includes an LMTD calculator (log mean temperature difference, counterflow and parallel-flow, with R and P factors) and a quick Q = U·A·ΔTlm area estimator with typical U-value references for common fluid pairs.