Using numerical simulations, properties of the flow and heat transfer in multiple pipe bends composed of 90 degrees-bends are investigated for various switching angles, and the mixing performance is compared by means of various trajectory-based analyses. Although the behavior of both the secondary flow and Nusselt number show a periodic feature, they do not completely correspond with each other. The Lyapunov exponent quantitatively exhibits a distinct difference in the mixing depending on the switching angle, while the Poincare map depicts a specific aspect even in a long-term. The residence time distribution is a potential indicator reflecting the flow structure with time-information. (c) 2006 Elsevier Ltd. All rights reserved.