I am trying to simulate condensation of water vapor using cooling water in a heat exchanger. However, I am not getting the expected results when I use the calculation type "Shell and Tubes Exchanger Rating".
I have performed the design calculations analytically and obtained a global coefficient U=2980W/m2 and a heat exchange area A=0,0984m2, which gave me a total of 3-4 pipes needed for my design specifications. When I use "Shell and Tubes Exchanger Rating" and input this number of pipes and their dimensions, however, DWSIM returns a much lower U value than expected, meaning that I get no condensation.
Is there an issue with this calculation type for heat transfer involving phase change? Or am I doing something wrong?
Any input is much appreciated. Thank you.
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Thank you for your quick answer. I have corrected the pressure drop on the hot side so that the pressure of the hot stream leaving the condenser is 4820Pa, but my problem remains. At this pressure the fluid should liquefy at 31,5ºC. But I still get an unexpectedly low U...
What could be the issue? It seems that I cannot get the U to increase, whatever I do.
Thank you.
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Marta it seems you are dealing with Absorption Chillers (preheaters) ! Don't use S&T plainly in this case. Almost all chillers employ P&F HXchangers or spiral tubes (if S&T)
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Hello,
I am trying to simulate condensation of water vapor using cooling water in a heat exchanger. However, I am not getting the expected results when I use the calculation type "Shell and Tubes Exchanger Rating".
I have performed the design calculations analytically and obtained a global coefficient U=2980W/m2 and a heat exchange area A=0,0984m2, which gave me a total of 3-4 pipes needed for my design specifications. When I use "Shell and Tubes Exchanger Rating" and input this number of pipes and their dimensions, however, DWSIM returns a much lower U value than expected, meaning that I get no condensation.
Is there an issue with this calculation type for heat transfer involving phase change? Or am I doing something wrong?
Any input is much appreciated. Thank you.
Here is my simulation file.
Hi Marta,
Please check the pressure of the vapor stream, as it will never be a liquid at the specified conditions.
Hi,
Thank you for your quick answer. I have corrected the pressure drop on the hot side so that the pressure of the hot stream leaving the condenser is 4820Pa, but my problem remains. At this pressure the fluid should liquefy at 31,5ºC. But I still get an unexpectedly low U...
What could be the issue? It seems that I cannot get the U to increase, whatever I do.
Thank you.
Use the solution inspector to check the internal calculation results, it should help.
Marta it seems you are dealing with Absorption Chillers (preheaters) ! Don't use S&T plainly in this case. Almost all chillers employ P&F HXchangers or spiral tubes (if S&T)