Steam purging of U-tube heat exchangers
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Guys, in a U-tube heat exchanger, both the tube side and the shell side are filled with phenol. Why is steam purging carried out first on the shell side, and only after the temperature of the shell side rises is purging done on the tube side?
When purging the shell side first, almost the entire heat exchanger is heated; conversely, in this case almost only the tube side is heated. Therefore, the purging procedure specifies the former approach
What if it is purged at the same time? How to understand it.
The requirement to purge the shell side first during steam purging is specific to exchangers with fixed tube sheets, aimed at preventing damage at the joints between the heat exchange tubes and the tube sheet due to thermal stress. In fact, for U-tube heat exchangers, it doesn’t really matter whether steam is used to purge the shell side or the tube side first; it’s just that people are accustomed to the practice of purging in fixed-plate heat exchangers. If there is an adequate supply of steam, it is not a problem to purge both the tube side and the shell side simultaneously.