Engineering tools · Free to use
ε-NTU Heat Exchanger Effectiveness Calculator
Calculate the effectiveness of an ideal exchanger from NTU and capacity-rate ratio.
Input parameters
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Result
Effectiveness is the ratio of actual to maximum possible heat transfer; dimensionless.
Equation
ε = Q / Qmax; NTU = UA / Cmin; Cr = Cmin / Cmax
Applicability
For steady single-pass parallel or counterflow exchangers with constant capacity rates and overall coefficient, no phase change and negligible heat loss. NTU ≥ 0 and 0 ≤ Cr ≤ 1. Cr = 0 is the mathematical limit as the capacity-rate ratio approaches zero, not a case with two finite positive capacity rates.
Notes
Effectiveness is the ratio of actual to maximum possible heat transfer; dimensionless.
Worked example
For a steady single-pass counterflow exchanger with equal capacity rates (Cr = 1) and NTU = 2, assuming constant capacity rates and overall coefficient, no phase change and no external heat loss, ε = NTU/(1 + NTU) = 2/3 ≈ 0.6667 (dimensionless).
Results are for engineering estimates; verify final designs against operating conditions and applicable standards.