摘要
The majority of this paper is to investigate effects of injection angles and velocity ratios (Vr) on thermal-hydraulic characteristics and thermal striping in a T-junction since the thermal striping is one of main degradation mechanisms for piping wall. Experimental measurement and observation are applied in the in-house T-junction. Considering the injection angle, a modified momentum ratio (M R *) is proposed to discriminate the flow pattern and to reveal the reverse flow phenomenon from the branch injection. The reverse flow upstream a T-junction can occur if M R * is less than approximately 0.05. The experimental results also reveal that strong thermal stratification exists near the intersection of a T-junction (x/D = 1) and uniform temperature distributions can be achieved as the mixing fluid passes through x/D = 4. The thermal striping in a T-junction can be investigated using the power spectrum density (PSD) versus frequency. Two distinct characteristics are revealed in these PSD spectra. The frequency for distinguishing these two regions is 9.0 Hz, which is similar to the value of 10 Hz in the previous work. In addition, PSD spectra are slightly higher for 90° injection than 45° injection and these spectra are insignificant to the Vr values.