Numerical Study on Flow and Heat Transfer in Concentric and Eccentric Annuli

The narrow annular channel has been widely studied for its relatively larger heat transfer surface and structural compatibility. In this study, numerical studies have been performed on the 3D forced flow and heat transfer of water in concentric and eccentric annuli by using CFX codes. The gaps of concentric annuli range from 1.0mm to 4.0mm with the interval of 0.5mm. The eccentricity ratioes in eccentric annuli are 0.2, 0.3, 0.5 and 0.7. The radius ratioes of the eccentric annulus include 0.33, 0.5 and 0.66. The calculated results are compared with some experimental data and they agree well. The results show that the flow frictional resistance factor decreases with increasing the gap size. The impact of gap sizes on the flow frictional resistance factor decreases with increasing Reynolds number. The flow frictional resistance factor in the eccentric annuli is larger than that in concentric annuli. Furthermore, the effects of the eccentricity ratio and gap size on Nu number and the flow frictional resistance factor are also investigated.