NTU Effectiveness Calculator

NTU Effectiveness Formula

Worked Example

UA = 3000 W/K, Ch = 4000 W/K, Cc = 2000 W/K, hot in at 120 °C, cold in at 20 °C:

1. NTU = 3000 ÷ 2000 = 1.5, Cr = 0.5
2. ε = [1 − e^(−NTU(1 − Cr))] ÷ [1 − Cr e^(−NTU(1 − Cr))]
3. ε = 0.690785, Q = 0.690785 × 200000 W = 138157 W

Capacity ratio Cr = Cmin/Cmax: 0.5 · Heat transfer Q = ε Cmin (Th,i − Tc,i): 138.157 kW · Maximum possible Qmax: 200 kW · Hot outlet Th,o: 85.4607 °C · Cold outlet Tc,o: 89.0785 °C

More Heat Transfer Calculators

• LMTD Calculator

  LMTD = (ΔT₁ − ΔT₂) ÷ ln(ΔT₁/ΔT₂)

  counter-flow ΔT₁ = Th,i − Tc,o, ΔT₂ = Th,o − Tc,i

  Example: Counter-flow: hot 150 → 100 °C, cold 30 → 70 °C, Q = 200 kW, U = 500 W/m²·K: LMTD = 74.8888 °C.

  Open the lmtd calculator →

• Heat Conduction Calculator

  Q = ΔT / R, R = L/kA, ln(r₂/r₁)/2πkL

  composite: R = 1/hᵢA + Σ L/kA + 1/hₒA

  Example: A 200 mm wall (k = 0.8 W/m·K, 10 m²) with faces at 40 °C and 10 °C: Heat transfer rate Q = 1200 W.

  Open the heat conduction calculator →

• Fin Efficiency Calculator

  η = tanh(mL)/mL, m = √(hP/kAc)

  P perimeter, Ac cross-section, Q = √(hPkAc) θb tanh(mL)

  Example: A 5 mm aluminium pin fin (k = 200), 50 mm long, h = 25 W/m²·K, base 100 °C in 25 °C air: Fin efficiency η = 92.4234 %.

  Open the fin efficiency calculator →

• Radiation Heat Transfer Calculator

  Q = εσA(T₁⁴ − T₂⁴)

  σ = 5.670374 × 10⁻⁸ W/m²·K⁴; plates: σ(T₁⁴ − T₂⁴)/(1/ε₁ + 1/ε₂ − 1)

  Example: A 1 m² surface (ε = 0.8) at 500 K in large surroundings at 300 K: Net radiation heat transfer Q = 2467.75 W.

  Open the radiation heat transfer calculator →

Frequently asked questions

Sources

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.