Temperature measurements inside the melting ice bead in a hot shear flow by utilizing molecular tagging thermometry technique

Abstract

In the present study, we report for the first time the temperature measurements inside the melting ice bead in a hot shear flow by utilizing Molecular Tagging Thermometry (MTT) technique. A parameter study of the airflow temperature and airflow speed was carefully performed. Moreover, the melting process of an ice bead under the natural convection condition was also measured for comparisons. One CCD camera and an intensified CCD camera were used to record the ice bead melting process. The results showed that, based on the phosphorescence images, the temperature distributions within the melting ice bead could be obtained by the MTT technique. For all the cases, the average temperature within the melted water region increased gradually from an initial value of about 1.0 ℃ to a final value of approximately 4.0 ℃. Besides, the ice beads melted at a much faster rate under the forced convection conditions than that of the natural convection condition. Furthermore, when subjected to a hot shear flow, the melting time of ice bead decreased as the increase of the airflow temperature and the airflow speed. In addition, as for the cases of relatively higher airflow speed and higher airflow temperature, the vertical movement coefficient of the windward three-phase junction point was increasing at a much faster rate than that of the leeward three-phase junction point. Besides, we proposed an equation to estimate the total melting time for the ice bead under the influence of the hot shear flow. Good agreements were found between the experimental and theoretical values of the total melting time for the ice beads under different conditions.