NTU–Effectiveness Method

Effectiveness ε of a heat exchanger from NTU and capacity-rate ratio Cr, for counter-flow and parallel-flow.

Heat transferNTU

Overall UAkW/K

C_{\text{min}}

(smaller capacity rate)kW/K

C_{\text{max}}

kW/KFlow arrangement

NTU: 4.000 -

Capacity ratio C_r: 0.600 -

Effectiveness ε: 0.908 -

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\varepsilon_\text{counter} = \frac{1 - e^{-NTU(1 - C_r)}}{1 - C_r \cdot e^{-NTU(1-C_r)}}

Symbol	Meaning	Unit
$UA$	Overall conductance × area	kW/K
$C_\text{min}$	Smaller of (m·cp) on each side	kW/K
$NTU$	Number of transfer units
$ε$	Effectiveness

Source: Kays & London - Compact Heat Exchangers

In short

Effectiveness \u03b5 of a heat exchanger from NTU and capacity-rate ratio Cr, for counter-flow and parallel-flow.

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