Heat exchanger calculation (relationship between shell-side cooling water flow rate and number of tubes)
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While using HTFS+ to perform calculations for shell-and-tube heat exchangers, I noticed that when the inner diameter of the shell remained constant, increasing the flow rate of the cooling water in the shell side resulted in a decrease in the number of tubes suggested by the software. Could anyone among you experienced this issue and tell me why it happens?
As the flow velocity increases, the convective coefficient of the shell fluid increases, thereby reducing the heat exchange area
It is the maximum number of pipes that is allowed to be reduced, not the actual number of pipes. At the first flow rate, the maximum number of pipes allowed is 22. After increasing the shell-side flow rate, the maximum number of tubes allowed is only 18
Has the actual number of pipes decreased? It can’t be that only the maximum number of pipes is allowed to decrease, while the actual number of pipes remains unchanged, right?
This post was last edited by xyq1983 on 2012-1-29 at 21:23. Please upload the examples as well so we can take a look. With the increased flow rate of cooling water, the logarithmic temperature difference changes (it should increase in the counterflow condition); the driving force increases, and a smaller area is required. By increasing the water volume, the flow rate rises as well; consequently, the K value increases, the heat transfer efficiency improves, and the required area decreases. However, the number of pipes allowed is specified in the mechanical design rules of the TEMA standard; even in design modes, the angle of the pipes and the pipe spacing are fixed. The shell side diameter remains unchanged, and the number of tubes is fixed; I think it has nothing to do with heat transfer calculations! I would appreciate some guidance from those who know more!
The actual number of pipes I selected is even the maximum number of pipes. My question now is: an increase in the shell-side fluid flow rate allows for a reduction in the number of tubes. What limits this phenomenon? Is there a relationship between the allowed maximum number of pipes and the flow velocity?
The source file is on the company’s virtual shared drive, so it cannot be exported. I’m sorry. Will the piping be restricted by the fluid flow velocity?
Take a look at GB151 or TEMA – there are requirements regarding piping. The software can calculate any flow rate as long as the pressure drop is acceptable; the number of pipes falls within the scope of mechanical design