Método NUT

El Método del Número de Unidades de Transferencia (NUT) se usa para calcular la velocidad de transmisión de calor en Intercambiadores de calor (especialmente en contracorriente) cuando no hay información suficiente para calcular la Diferencia de Temperaturas Media Logarítmica (DTML).

The method proceeds by calculating the heat capacity rates (i.e. flow rate multiplied by specific heat) C_h and C_c for the hot and cold fluids respectively, and denoting the smaller one as C_min.

A quantity

$q_{max}\equiv C_{min} (T_{h,i}-T_{c,i})$

is then found. This value of q_max is the maximum heat which could be transferred between the fluids.

The effectiveness, E is then defined in terms of that maximum:

$E \equiv \frac{q}{q_{max}}$

where

q = C_h(T_h,i − T_h,o) = C_c(T_c,o − T_c,i)

is the actual heat transferred between the fluids..

For given geometries, E can be calculated using correlations in terms of the 'heat capacity ratio'

$C_r \equiv \frac{C_{min}}{C_{max}}$

and the number of transfer units, NTU

$NTU \equiv \frac{U A}{C_{min}}$

where U is the overall heat transfer coefficient and A is the heat transfer area.

Referencias

[1] heat- exchanger performance by the LMTD and -NTU methods.

2. F. P. Incropera & D. P. DeWitt 1990 Fundamentals of Heat and Mass Transfer, 3rd edition, pp. 658–660. Wiley, New York

Enlaces externos

• Script de Calor y Frío de Ingeniería Mecánica, 1º Tema Métodos numéricos de Transferencia de Calor.

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