I've try to simulate the ORC. The thermodynamics result seems okay but when I export data to calculate the exergy destroyed (every device), the evaporator show exergy efficiency above 100%. Even if I try others property package (Peng-Robinson, Coolprop, SRK), all of it is above 100% at evaporator
I used Cyclopentane as main working fluid (Dead-state temperature is 30C, 303K)
I'm not sure what's wrong with the evaporator (at first I simulate bigger cycle then I cut it off to recheck the result. When I simulate bigger cycle, others component exergy destroyed seems okay, only at this evaporator have exergy efficiency >100%)
And I wonder DWSIM have any function to calculate exergy destroyed? so I don't have to export thermodynamics data and calculate it in excel.
Thank you for your assistance in resolving this issue.
For evaporator I used :
exergy in flow =m(hin-hout)-T0(sin-sout) ; hot and cold
Edest=Ehotflow+Ecoldflow
exergy efficiency =exergy in flow(Cold)/exergy in flow(Hot)
I had a look to your ORC model ... I found something strange in the evaporator.
The heat and temperature profiles have a temperature cross that I can't understand ... even changing the data in countercurrent configuration (apparently DWsim only makes the profile only in co-current) the cold stream becomes hotter that the hot stream ...
Isn't there something wrong?
Hope it helps.
Luca
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I don't understand where is the temperature crossing in the model because
Hot stream inlet is 210.8 C and outlet is 56.3C
Cold stream inlet is 45.8C and outlet is 171.9C
and also my evaporator model is counter-current
I confused, can you please explain it more? I want to understand what's happen to the simulation.
but I really appreciate that you try to help me out, Thank you for that!
if you enable the calculate Heat Exchange Profile, run the model and look at the Evaporator Q vs t profile (see screenshot) you see a temperature cross.
Moreover this profile is always in co-current, regardless if a countercurrent flow direction is selected. I tried to chart the cold stream temperatures data in reverse order, but still a T cross appears.
I am not sure whether this is a bug in the program due to phase change in the exchanger, but I suspect that the results could not be as expected.
Hi, Luca
So DWSIM cannot simulate the counter-current flow right?
I wonder that what can we do if the temperature crossing occurred but the program report that it have no problems (Once the programs always showed the error if the temperature crossing).
Best regards,
Tanatip
Last edit: Tanatip 2024-05-22
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I've try to simulate the ORC. The thermodynamics result seems okay but when I export data to calculate the exergy destroyed (every device), the evaporator show exergy efficiency above 100%. Even if I try others property package (Peng-Robinson, Coolprop, SRK), all of it is above 100% at evaporator
I used Cyclopentane as main working fluid (Dead-state temperature is 30C, 303K)
I'm not sure what's wrong with the evaporator (at first I simulate bigger cycle then I cut it off to recheck the result. When I simulate bigger cycle, others component exergy destroyed seems okay, only at this evaporator have exergy efficiency >100%)
And I wonder DWSIM have any function to calculate exergy destroyed? so I don't have to export thermodynamics data and calculate it in excel.
Thank you for your assistance in resolving this issue.
This is my exergy calculation
For evaporator I used :
exergy in flow =m(hin-hout)-T0(sin-sout) ; hot and cold
Edest=Ehotflow+Ecoldflow
exergy efficiency =exergy in flow(Cold)/exergy in flow(Hot)
This is my whole WHRS (no cut-off) DWSIM file
Hello Tanatip,
I had a look to your ORC model ... I found something strange in the evaporator.
The heat and temperature profiles have a temperature cross that I can't understand ... even changing the data in countercurrent configuration (apparently DWsim only makes the profile only in co-current) the cold stream becomes hotter that the hot stream ...
Isn't there something wrong?
Hope it helps.
Luca
Hi, Luca
I don't understand where is the temperature crossing in the model because
Hot stream inlet is 210.8 C and outlet is 56.3C
Cold stream inlet is 45.8C and outlet is 171.9C
and also my evaporator model is counter-current
I confused, can you please explain it more? I want to understand what's happen to the simulation.
but I really appreciate that you try to help me out, Thank you for that!
Best regards,
Tanatip
Hi Tanatip,
if you enable the calculate Heat Exchange Profile, run the model and look at the Evaporator Q vs t profile (see screenshot) you see a temperature cross.
Moreover this profile is always in co-current, regardless if a countercurrent flow direction is selected. I tried to chart the cold stream temperatures data in reverse order, but still a T cross appears.
I am not sure whether this is a bug in the program due to phase change in the exchanger, but I suspect that the results could not be as expected.
Hope this helps.
Luca
Hi, Luca
So DWSIM cannot simulate the counter-current flow right?
I wonder that what can we do if the temperature crossing occurred but the program report that it have no problems (Once the programs always showed the error if the temperature crossing).
Best regards,
Tanatip
Last edit: Tanatip 2024-05-22