What is heat exchanger efficiency?

Heat exchanger efficiency, more accurately termed heat exchanger effectiveness (ε), is the ratio of actual heat transfer rate to the maximum possible heat transfer rate. It quantifies how closely the exchanger approaches ideal thermodynamic performance.

How do you calculate heat exchanger effectiveness?

Effectiveness is ε = Q_actual / Q_max, where Q_actual = ṁ·cp·ΔT and Q_max = C_min·(T_hot,in − T_cold,in).

Heat Exchanger Efficiency Calculator

Professional heat exchanger effectiveness calculator using the NTU method. Analyze shell and tube, plate, counterflow, parallel flow, and HVAC heat exchangers. Includes formulas, charts, and worked examples.

🔧 Heat Exchanger Performance Calculator

Enter known parameters. The calculator computes effectiveness (ε), NTU, heat duty, and capacity ratio.

🔥 Hot Fluid

Mass Flow (kg/s)

Specific Heat (kJ/kg·K)

Inlet Temp (°C)

Outlet Temp (°C)

❄️ Cold Fluid

Mass Flow (kg/s)

Specific Heat (kJ/kg·K)

Inlet Temp (°C)

Outlet Temp (°C)

⚙️ Configuration

Flow Arrangement

Overall U (W/m²·K)

Area (m²)

Fouling Factor (m²·K/W)

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Heat Duty Q_actual (kW)

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Max Q_max (kW)

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Effectiveness ε

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NTU

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Capacity Ratio C_r

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Theoretical ε (NTU)

Effectiveness (ε) vs NTU

Counterflow (Cr=0.6) Parallel (Cr=0.6) Shell&Tube (Cr=0.6)

📐 Effectiveness Formula & NTU Method

ε = Q_actual / Q_max

Q_actual = C_hot(T_hot,in−T_hot,out), Q_max = C_min(T_hot,in−T_cold,in). NTU = UA/C_min.

🔬 ε‑NTU Relationships

ε = [1−exp(−NTU(1−Cr))]/[1−Cr·exp(−NTU(1−Cr))]

ε = [1−exp(−NTU(1+Cr))]/(1+Cr)

ε = 2/[1+Cr+√(1+Cr²)·(1+e⁻ᴳ)/(1−e⁻ᴳ)]

🧹 Fouling Impact

Fouling adds thermal resistance. A factor of 0.0005 m²·K/W can reduce effective U by 30%.

📝 Worked Examples

Default values demonstrate a counterflow water-water exchanger with 66.7% effectiveness.