Although performance data are normally presented on a surface-by-surface basis, considerable progress has been made in prediction or correlation of surface performance. Analytical solutions exist for most possible plain fin geometries in laminar flow regions as discussed in Section 300. In the turbulent flow region, the hydraulic diameter is the significant dimension. One may predict the turbulent region j and f characteristics of plain fin geometries using the hydraulic diameter. This will generally give good results, except for isosceles triangular channels having a very small apex angle.

This section gives heat transfer and friction correlations for wavy, offset-strip, and louver fins shown in Figure 299.1 of Section 299.

A. Wavy and Herringbone Fin

The wavy and herringbone fin geometries are generically similar. Both have a “wavy” flow path, however, the herringbone wave form is that of a chevron and the wavy is in the form of a smooth wave. Dong et al. (2007) provide an empirical power law correlation for herringbone fins. Their correlation is based on data for 11 herringbone fin geometries. The j and f versus Re_Dh correlations are given by

\[\label{eq1} j=0.0836\,\mbox{Re}^{-0.2309}_{D_{h}}\left(\frac{p_{f}}{b}\right)^{\!0.1284}\left(\frac{p_{f}}{2e_{w}}\right)^{\!-0.153}\left(\frac{L}{p_{w}}\right)^{\!-0.326} \tag{1}\]