PARAMETRIC EFFECT OF THE INTERRUPTED ANNULAR GROOVE FIN ON FLOW AND HEAT TRANSFER CHARACTERISTICS OF A FINNED CIRCULAR TUBE HEAT EXCHANGER

The influences of the geometrical parameters of interrupted annular groove fin mainly including the annular groove diameter, the groove arc length, and the fin spacing, on the fin side thermal-hydraulic characteristics of a finned circular tube exchanger were numerically investigated by actualizing the custom FORTRAN programing with SIMPLE algorithm in a non-orthogonal curvilinear co-ordinate system, and the regression formulas of average Nusselt number and friction factor with flow parameters and geometrical parameters were obtained. Compared with the referential plain fin, interrupted annular groove fin could significantly improve thermal performance under the same pumping power constraint, and Nusselt number is closely germane to the secondary flow, which implies that the fin side heat transfer is depended entirely on the secondary flow strength. For Nusselt number, the annular groove diameter and the groove arc length have positive effect, while the fin pitch, the groove circumferential and radial locations have negative effect. The dominant parameters influencing on friction factor in turn are the fin pitch, the groove radial location, and the annular groove diameter. The optimal annular groove diameter is screened, and found that the optimal annular groove diameter is closely related with Reynolds number under the same pumping power constraint, while under the same mass-flow rate constraint that is scarcely related with Reynolds number.