Tuesday, March 3, 2009

Flow Fraction

Flow fraction usually deal with the vapor fraction and liquid fraction. However, here is something different will be discussed which is related to shell and tube heat exchanger. There are bunch of criteria that need to be considered but flow fraction on the shell side flow fraction will be highlighted since this criteria is not really taken into consideration when designing a new shell and tube heat exchanger, (STHX).

As illustrated above, there are about five main flow in the shell side where only one (B) out of five is cross flow and the remaining (A, C, E, and F) are leak-flow or bypass. There are proposed calling for these streams; main cross-flow stream (B), a tube-to-baffle-hole leakage stream (A), a bundle bypass stream, a pass-partition bypass stream (F), and a baffle-to-shell leakage stream (E).
As vapor and liquid fraction, there is a requirement to meet the specification of any particular product before sell it off. So, same goes to the shell side flow fraction of the STHX where the minimum design criteria is that B fraction must be greater than 40% and for E is less than 20%. So, it’s not necessary yet to increase the size of the heat exchanger if this specification not met. There are couple of optimization can be done to get the desired temperature for any particular stream.
The tricky part of the optimization of STHX will be elaborated in detail in next article. Those will explain the areas that can be used to challenge design engineer during design review. In the meantime, design engineer can use that info also to enhance the design

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