A numerical study on entropy generation and optimization for laminar forced convection in a rectangular curved duct with longitudinal ribs

The effects of longitudinal ribs on laminar forced convection and entropy generation in a curved rectangular duct are investigated in the present paper by numerical methods. The major concern is to explore the optimal rib number and arrangement of the mounted rib based on the minimal entropy generation principle. The detailed information of local distributions of entropy generation due to frictional and heat transfer irreversibility as well as the overall entropy generation in the whole flow field are analyzed separately. The results show that the flow features in the curved duct, including the secondary flow motion, and the distributions of velocity and temperature, are considerably influenced by the number and arrangement of mounted ribs. Through the comparison of the cases with none to four ribs mounted on duct walls with various arrangements, it is found that a single rib on the heated duct wall is the most effective way to reduce entropy generation, whereas additional ribs can not give further reduction in entropy generation. The rib arrangement is suggested to be used in practical applications so that the irreversibility due to the laminar forced convection in the curved duct would be minimal and the best exergy utilization could be achieved.