Heat transfer and flow friction characteristics of dimple-type heat exchanger in axial piston pump

Abstract

The heat exchanger is widely applied to many axial piston machines, and its structure significantly affects the flow and heat transfer characteristics. The fluid flow and heat transfer characteristics of a dimple-type heat exchanger in the axial piston pump are numerically investigated. The variations of the Nusselt number, friction factor and heat transfer performance with the Reynolds number, and the dimple radius to depth are obtained. The results show that both the Nusselt number and the resistance coefficient of the spherical dimple channel are higher than those of the triangle dimple one. Thus, from the view of the heat transfer performance, the spherical dimple channel is better. Furthermore, the friction factor increases as the dimple radius to depth increases. With the increase in the dimple radius to depth ratio, the shear stress at the wall of the spherical dimpled channel gradually decreases and then reduces the wall friction resistance. Comparing with the triangle dimple channel, the friction factor in the spherical dimple channel is 0.044-0.022, which reduces about 9%. When the radius-depth ratio is set to 0.1, the effectiveness factor for the spherical dimpled channel has better performance.