Thermal analysis on a criterion for interaction of secondary vortices with primary flow field under parallel mode rotation

Abstract

In this paper, the effects of rotational forces such as centrifugal buoyancy and Coriolis forces caused by parallel mode channel rotation on turbulent air flow through tubes with different aspect ratios are investigated numerically. However, rotational effects does not necessarily increase heat transfer and pressure loss since a number of parameters such as main flow condition and channel aspect ratio must be regarded. This paper discusses rotational effects and establishes novel criteria that illustrate how the aspect ratio affects the formation of secondary vortices and thus convective heat transfer coefficient on different rotational conditions. The numerical modeling results are validated by the available experimental and numerical data in literature and it is shown that the normalized Nusselt number (Nu/Nu0) result points for each aspect ratio collapses on a single curve if it is plotted against GrΩα/Re which it is revealed that α depends on aspect ratio only. However, it is demonstrated that once the GrΩα/ Re < λ the effects of rotation may be neglected and thus Nusselt number is equal to stationary case counterpart while λ is also determined as a function of aspect ratio only. The variation of α and λ with respect to channel aspect ratio is discussed as well.