Optimization for inner flow field of tube with nonuniform heat flux boundary condition
                                                     YU Ping1, GENG Weixuan2, Guo Huafeng1
(1.College of Mechanical and Electrical Engineering, Xuzhou University of Technology, Xuzhou 221018, China;2.Jiangsu Province Qinhuai River Water Conservancy Project Management Office, Nanjing 210000, China)

Abstract: Aiming at heat transfer enhancement of solar collector tubes, the flow field distribution based on the field synergy principle with circumferentially nonuniform heat flux boundary condition was investgated. The momentum equation with a special additional volume force was calculated with constructing Lagrange function using variational method through the numerical simulation. The relationship of longitudinal vortexes and heat transfer coefficient was established. The method of heat transfer enhancement with optimizing the flow field and improving the rate of usage for solar energy was put forward. The results show that under the condition of nonuniform heat flux the longitudinal vortexes in the heat exchange tube can enhance the heat transfer markedly and the flow resistance increase is similar to heat transfer enhancement. And the increase range of the flow resistance is less than the heat transfer enhancement. The effect of heat transfer of optimize flow field is much higher with greater longitudinal vortex intensity and larger Reynolds number.

Key words: heat transfer enhancement; nonuniform heat flux; longitudinal vortexes; field synergy principle