Abstract :
In the present study, successively increased or decreased louver angle patterns are proposed and 3-D numerical analysis on heat and fluid flow are carried out. Five different cases of successively increased or decreased louver angles (+2°, +4°, −2°, −4°, and uniform angle 20°) are investigated: case A (20°, 22°, 24°, 26°, 24°, 22°, 20°), case B (20°, 24°, 28°, 32°, 28°, 24°, 20°), case C (26°, 24°, 22°, 20°, 22°, 24°, 26°), case D (32°, 28°, 24°, 20°, 24°, 28°, 32°), case E (uniform angle 20°) . For case A (+2°), case B (+4°), case C (−2°) and D (−4°), the maximum heat transfer improvement interpreted by j/j0 are 115%, 118%, 109% and 107%, and the corresponding friction factor ratio f/f0 are 116%, 119% 110% and 108%, respectively, where j/j0 and f/f0 are the Colburn factor ratio and friction factor ratio between successively variable louver angles and uniform angle, respectively. It is also shown that the maximum area reduction for case B can reach up to 25.5% compared to a plain fin surface. The present results indicated the successively variable louver angle patterns applied in heat exchangers could effectively enhance the heat transfer performance.
