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Several different designs for a header type were numerically studied to achieve uniform distribution of gas phase flow in the header of a shell-and-tube heat exchanger. The different geometries included the position and shape of the inlet nozzle, number of outlet tubes, and length. In numerical calculations, the k-epsilon realizable turbulent model was employed. Standard deviation was used to evaluate the uniformity of the velocity distribution among the whole outlets of the header. As a result, flow patterns in the header could be visualized by using post-processing of numerical results. The uniformity of flow distribution increased with header length, whereas it decreased with gas flow rate. Furthermore, the optimum position and shape of the inlet nozzle could be proposed for a uniform distribution of a 1.3 m-length header, the very same used for the heat exchange of the commercially viable allyl chloride process.

In this study we examine the relationship between the social participation in the early adolescents and school adjustment as well as the mediating effects of a sense of community. Findings provide ways of intervention that can increase a youth's school life. Based on samples of 2,351 first grade middle school students from the data in the 'Korea Youth Panel Survey' administered by the National Youth Policy Institute, we analysed the correlation among the variables. The results are as follows. First, the social participation of youths showed a major influence on school adjustment, and was identified as: the more the students participate in social activities, the better the students get adjusted to school. Second, the social participation has a significant effect on sense of community. In other words, the more the students participate in social activities, the more the students get a sense of community. Third, a sense of community mediated the process of social participation on school adjustment. These findings indicate that in order to increase a youth's school adjustment, a promotion of social participation and an effort to increase a sense of community are required. The implications of these findings suggest that by intervening social welfare and policy, can improve the integrity of a youth's school life.