An experimental investigation for the effect of pulsation on heat transfer characteristics in pipes

摘要

Heat transfer characteristics of pulsated turbulent pipe flow under different conditions of pulsation frequency, amplitude and Reynolds number was experimentally investigated. The pipe wall was kept at uniform heat flux. Reynolds number was varied from 5032 to 28,984 while frequency of pulsation ranged from 1 to 8 Hz. The displacement amplitude of pulsation inducing mechanism was varied between 0.0127 m to.0381 m. The behavior of local Nusselt number under the influence of pulsation parameters was studied. The results show enhancement in the local Nusselt number at the entrance region for low Reynolds number. The rate of enhancement decreased as Re increased. However, reduction in the heat transfer coefficient was observed in the fully developed region. Reduction in the mean Nusselt number was observed in the fully developed region. Reduction in the mean Nusselt number was observed at all pulsation frequencies and the effect of pulsation is shown to be more significant at high Reynolds numbers. Maximum reduction of about 13% was observed at Re = 20,138 and f = 6 Hz. It can be concluded that the enhancement in the local heat transfer coefficient is more pronounced in the thermally developing region than in the fully developed region. The effect of pulsation on the mean Nusselt number is insignificant at low values of Re. Also, the effect of amplitude on the mean Nusselt number is insignificant.