Abstract: The effect of fluid flow and heat transfer caused by fins in plate-fin heat exchanger is investigated, and then a new kind of fins, called shark gill fin, is proposed. The main functions of this kind of fins include enlarging fluid turbulence effect, changing flow direction in the same layer of fins, promoting fluid flow among channels, decreasing fluid temperature difference in the same cross-section and finally promoting heat exchange efficiency. The temperature, velocity, pressure and turbulence field under twelve conditions are analyzed by changing cocking-up structure and opening size in shark gill fin and finally, the distribution of fluid flow, temperature, dynamic pressure and turbulent intensity under steady state conditions are achieved. It can be concluded that when the opening size is 1 mm, the fluid velocity difference can reach by 47.38%, the temperature difference can reach by 0.7 ℃/m, the turbulent intensity difference can reach by 0.816%. When cocking-up structure is 10°, the fluid turbulent intensity can reach by 3.162%, the temperature difference can reach by 1 ℃/m. The results demonstrate that, in view of fluid flow, the effect of opening size is more important than cocking-up degree while, in view of temperature field, the opening size is less important than the cocking-up degree, besides, the cocking-up degree has less effect on fluid velocity and dynamic pressure.

Key words: cocking-up structure, plate-fin heat exchanger, shark gill fin, turbulence effect