Heat Transfer Enhancement by Several Longitudinal Vortices in a Pipe

In this report, two ∿ eight vortex generators were inserted in the pipe in order to augment heat transfer. We show how the heat transfer coefficients along the heated pipe are affected by the several longitudinal vortices which were generated by several vortex generators. The streamwise and circumferential heat transfer coefficients in a pipe were measured for air flow over a range of Reynolds number Re ≒1.95∿4.75×(10)^4. And, both mean Nusselt number and friction factor were presented as a function of Reynolds number. Moreover, evaluation of the theamal performance ratio was carried out under the condition of fixed pumping power, and it was found that thermal performance ratio of the four type winglet vortex generator is lager than other type of the one.