*3.3.2 Optimal number of boards*

The optimum number of boards of thickness *e*, to be assembled on a rack of length *L*, is then given by:

$$m^\* = \frac{L}{\delta^\* + \varepsilon} \tag{16}$$

Other issues of importance in rack design such as the determination of heat transfer coefficients between electronic boards and air, and the calculation of the heat flux evacuated by natural convection are discussed in Ref. [1].

<sup>3</sup> See Data Bank in Ref. [18].
