Number of Mass Transfer Units

NTU is a dimensionless parameter used in the effectiveness-NTU analysis method.

It is defined on page 508 of the text book, in equations 11.23 and 11.24. Equation 11.24 is listed below:

Where is overall heat transfer coefficient, is area, and is the smaller heat capacity rate (pick from either the hot or the cold fluid in your heat exchanger).

As with all non-dimensional parameters we can think of this as a ratio of two things.

A heat exchanger will be better if this number is larger.

- Dr. Paul