In the present study, the performance characteristics of the conical-ring turbulators are determined by means of the entropy-generation minimization method based on the second law and enhancement efficiency based on the first law of thermodynamics. The relations between these performance and flow-induced vibration characteristics have been examined. The maximum entropy generation, at the same Reynolds number, occurs in sequence by the conical rings with 10, 20 and 30 mm pitches, respectively. The conical rings are thermodynamically advantageous (N-s,N-a < 1) UP to 8000 Reynolds number with respect to entropy generation. The enhancement efficiency increases as the pitch decreases and varies between 0.86 and 1.16. The turbulators with 20 and 30 mm pitch, especially, produce vortices having low amplitudes up to a Reynolds number of 12,000. (C) 2003 Elsevier Ltd. All rights reserved.