The effect of the Reynolds number on the velocity and temperature distributions of a turbulent condensing jet

摘要

In this study, we investigated the effect of the Reynolds number (Re) on the velocity and temperature distributions of a turbulent condensing jet from a long pipe nozzle. The Re of the condensing jet ranged from 78,000 to 170,000. Jet velocity was measured using a Phase Doppler Particle Analyzer (PDPA) system and temperature was measured with a K-type thermocouple. We used the effective radius to investigate the effect of Re on the velocity and temperature distributions and compared our results with previous results on air (single phases) jet. From the experimental results, it was found that distributions of velocity and temperature show a self-similarity state in the far-field. The condensation more occurred at low Re. Thus, from momentum conservation, the velocity decay rate decreases by 18.2% as the Re increases from 78,000 to 170,000. Compared to air jet issuing from the pipe nozzle, velocity of condensing jet decays more rapidly due to the condensation of water vapor. The velocity spread rate also falls by 8.1% as the Re increases from 78,000 to 170,000. The temperature decay rate decreases by 11.1% and temperature spread rate increases by 7.4% as the Re increases from 78,000 to 170,000 since jet entrainment decreases at higher Re. The latent heat was released at the condensing jet by condensation of vapor. Thus, the temperature decay rate of condensing jet is smaller than that of air jet while the temperature half width of condensing jet is larger than that of air jet. (C) 2017 Elsevier Inc. All rights reserved.