A computational study is presented which analyzes details of the flow and heat-transfer behaviors in a novel heat-transfer-enhancement tube with a low-Reynolds number turbulence model. The tube is constructed with a series of alternative vertically and horizontally positioned oval pipes connected by transition sections, which bridge a vertically positioned cross-section to a horizontally positioned one, or vice versa. Results are presented for local as well as overall flow and heat-transfer parameters, including skin-friction coefficient and Nusselt number. It is found that the transition sections contribute most to the promotion of heat-transfer but with the penalty of producing the largest pressure drop per unit length. The geometry of the transition section tends to provoke separation bubbles, which not only attenuate local heat-transfer rate but also result in higher pressure-loss. The study demonstrates that, within the range of Reynolds numbers investigated, this new configuration can largely enhance heat-transfer from 40% to over 100% comparing to a circular pipe. However, the price is that the pressure drop caused by the former is also generally twice as much as that of the latter. (C) 2004 Elsevier Ltd. All rights reserved.