Influence of Fin Aspect Ratio on Heat Transfer Enhancement

An experimental investigation was conducted to determine the influence of fin aspect ratio on the heat transfer enhancement in narrow, rectangular ducts. Experiments were carried out in a transparent flow channel of rectangular cross section using an inline array of 24 short, square fins mounted on the bottom wall. The fin length-to-height aspect ratio (L/B) was varied over three values: 2, 1, and 0.67. The hydraulic diameter-based Reynolds number was varied from 800 to 8500. The experiments were conducted in water and a dielectric liquid.

The results obtained showed an increase in pressure drop as the fin aspect ratio decreases. However, the nondimensional heat transfer coefficient for the three-dimensional fins of this study was found to be independent of fin aspect ratio; this is in contrast to the expected behavior based on information in the literature for two-dimensional ribs. An empirical correlation is proposed for the heat transfer coefficient as a function of Reynolds number and fluid properties.