Numerical investigation on the effects of slotted height on performance of louver and slit fins at different fin pitches

Abstract

In this paper, the effects of slotted height at different fin pitches are analyzed in detail, aiming to investigate the function and optimal ratio of slotted height to fin pitch. In the cases of high Reynolds number for louver fin, the ?bimodal phenomenon? of heat transfer coefficient begins to appear with the increasing slotted height. As the slotted height is about half of the fin pitch, the heat transfer coefficient has a local minimum value, of which there are two peaks on both sides. How-ever, the pressure drop has been increasing with the increasing slotted height. The optimal slotted height under different fin pitches is more instructive than the optimal louver angle. For slit fin, the heat transfer coefficient increases first and then decreases with the increasing slotted height, so does the pressure drop. Meanwhile, as the slotted height is about 0.3~0.45 times and 0.5~0.65 times of fin pitch for louver fin and slit fin, respectively, the comprehensive performance can reach a maximum. The optimal comprehensive performance under 1.2 mm fin pitch is greater than the optimal comprehensive performance under 1.8 mm fin pitch. For lower Reynolds numbers, the optimal comprehensive performance of louver fin is roughly similar to the slit fin. For higher Reynolds numbers, the optimal comprehensive performance of louver fin is greater than that of slit fin.