Simulations are performed to study the heat transfer behaviour of an equilateral triangular section duct following a tortuous path for fully-developed laminar flows with Reynolds numbers below 200. The enhancement of heat transfer and the increase in pressure drop are compared with those for ducts of circular, semi-circular and square section following the same serpentine path. For this flow regime, the triangular duct is shown to be the optimum choice (best heat transfer augmentation compared with increased pressure drop) amongst those studied. The effects of changing the path shape, the apex angle for an isosceles triangular cross-section and rounding of a corner of the equilateral triangular duct are also considered. (c) 2007 Elsevier Ltd. All rights reserved.