Designing a Heat Exchanger Network
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- เผยแพร่เมื่อ 26 ส.ค. 2024
- Organized by textbook: learncheme.com/
Using MER targets and pinch point determined in prior screencast, setup a heat exchanger network with utilities. Made by faculty at the University of Colorado Boulder Department of Chemical and Biological Engineering. Reviewed by faculty from other academic institutions.
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All I need to know for the exam in 5 minutes. You saved for me time, nervousness and a good grade. Thank you... really.
Actually, that rule only applies at the pinch. Heat exchange between H2 and C1 do break the convention of Ch>Cc on the cold side but this is okay since the other exchanger is internal to this at the pinch. The minimum approach temperature dTmin is not broken.
what if the dTmin is also broken ?
does it mean that we cannot apply heat exchanger like you did and there are no solution ?
My professor took more than 6 lec still no output but from this video..work like a charm
Great video 👏 small correction at 8:15 is required cold stream can be heated to 75°C not 35°C
No, it 35 deg only, i think you took temperature difference as (t-30) instead of (80-t).
This is very helpful. As mentioned by another viewer, I would really appreciate a video on the heat loops. Thanks!
While evaluating in the cold side, the connection is made between H2 and C1. but the rule specifically says that Ch>=C1. In this case 1!>2. How can one connect these two streams? and what did you exactly mean by crossing over at that point?[8:12]
same doubt here
For those who are still wandering: If you look at the derivation at 2:50, we say that DeltaT2 corresponds to DeltaTmin. So we know that DeltaT1 needs to be bigger than that hence, c_c has to be smaller than c_h. But at 8:12, DeltaT2 does NOT correspond to DeltaTmin, but is (90-35=55K) and DeltaT1 is (80-30=50K). So if you look at the derivation at 2:50 you would only be allowed to do this transfer if c_c is bigger than c_h even though we are at the cold side of the pinch. So always check if the temperature difference after the transfer is bigger or smaller than before than check if c_c has to be bigger or smaller than c_h according to the two formulas mentioned around 2.50.
I've watched both screen casts, this helped a lot. Thank you very much
For the hot pinch, what do you do if the hot energy is greater than the cold? I guess it means the hot has enough energy to cool the hot stream to its target temp, but how does it change the way I draw this? Do I add a utility on the hot stream? do i write the cold stream energy under the circle instead of the hot stream energy?
This is a great material of explanation basics of pinch approach. Very clear and helpful.
Thanks for the educative screen cast. i think the estimated temperature of C1 in the cold side of the pinch should be 90/2 + 30 = 75. Pls check
Yes, i fully agree
Where is the video that follows this about the heat loops to minimise the amount of heat exchangers?
At 5:10 u said we can't go from 80 to 140 degree celsius for C2 , why ?
In cold side networking you have to remove heat from H1 and add heat to C2 . 90kW Adding to C1 heats it from 30 degrees to 75 degrees. How can you get 35 deg , you are not cooling down the cold stream i suppose, and the remaining 10kW is supplied by H2 making the cold utility 50kW.
+Srihas Velpuri
yeah your right i caught that also, its just a mistake
Yeah, it's 90 = 2 (x - 30), not 90 = 2 (80 - x).
Yes if you start from 30 DegC cold water inlet and match C2 with H3 you will get cold water outlet as 75 degree but then there will be a discontinuity in stream temperature at the pinch point which is 80 degC.. So how do you account for the the temperature rise of cold water from 75 deg to 80 deg C. You have to add a hot utility then which is against the rules of pinch analysis as one should not add hot utilities in cold section and vice versa because they in turn increase utility requirements on the other side to maintain energy balance. So one should always start from the pinch temperature. The theory on the web cast is correct. Moreover if you do that you may not be able to utilise 10 kw of C1 to cool H2.
@@mustafak4b Nope, that's not a mistake. He is right. In his case, the 90kW from H1 can heat up C2 completely to 80 celcius only if the starting temperature starts from 35 celcius. That is why he calculated the 35 celcius there. So from 30 celcius to 35 celcius in C2, you will need additional 10kW heat which he took from stream H2. This is why he linked H2 with C2 (In between 30-35 celcius)
Is that possible to have multiple pinch point? And how to solve the problem if it has two pinch?
after all these years i keep coming back
This is an excellent video, however you make a slight error in your final exchanger. You can't have a heat exchanger going from a hot stream with a lower specific heat to a cold stream with a higher specific heat on the cold side of the pinch.
Keep up the good work and I can't wait for the heat loop breaking video!
Could you explain a little bit why?
Hi there.. Was wondering how do you calculate the estimated temperatures at the pinch points; i.e. 90 deg for H1 and H2 as well as 80 deg for C1 and C2?
its actually from the last video, taken reference from that.
Question: Is it possible to use this method with 3 streams to be heated and 3 streams to be cooled?
how do you determine the minimum heat lost to a heat sink :(
Hi you mentioned you would post a video of identifying heat loops and minimizing the amount of heat exchangers. Do you know where can I find the video?
Im still trying to find it
Hi, I just wondering if one temperature change is exactly between the two pinch temperature, how to deal with this situation?
Question at around 5:00. Why can't we increase the cold stream from 80 C to 140 C? (@C2) I didn't understand the reasoning behind that :)
Great question! So the duty to cool the hot stream from 180 to 90 C is 270kW as shown in the video. This means that it can only take 270kW of out of another stream. However, the duty required to heat the cold stream from 80 to 140 is 300kW. This means that the duty of 270 kW from the hot stream is not enough to completely heat the cold stream.
Please let me know if I can clear this up any more!
Well done. Is it possible to calculate a flash with 5 components the same way?
Dear Prof,
I have the following discrepancies in your presentations
1.In Step 1 procedure, you actually swap the values of H1 and H2 streams.
1.In HEN Network Formation, You would not be able to connect H2 with C1 because, C of H2 is less than C of C2
Swami Nathan On the hot side, you need to connect ones where C of the cold stream is greater than or equal to the hot stream. As for swapping the values of the H1 and H2 streams, I think you are referring to the previous screencast that is linked to this one. Yes, that is a problem and we hope to correct it soon.
LearnChemE Thanks for your reply. I still agree with your comments, But I was referring for cold side section. Please kindly check the second connectivity ie H2 with C1.
Hello, if our temps. are between pinch temps., how should we do? For example, pinch temps. are 90C-80C and we have from 120C to 80C in the table. How is it possible?
Such an amaing video, really made my concepts clear , thanks a lot, subscribed!
Can you please tell how can I design a heat exchanger network whose delta T min at the threshold ..like the minimum cold utility requirement is zero..
There will be no pinch matches right?
This screencast has been reviewed by faculty from other academic institutions.
+LearnChemE shouldn't the temperature on the cold side of the pinch be 75 rather than 35? 90=2(x-30) instead of 90=2(80-x)
+Tu mi You are incorrect. 90kW added to C1 is 80 - (90/2) = 35.
yeah but aren't you actually heating C1from 30 to 75 not cooling it from 80 to 35?
Yes if you start from 30 DegC cold water inlet and match C2 with H3 you will get cold water outlet as 75 degree but then there will be a discontinuity in stream temperature at the pinch point which is 80 degC.. So how do you account for the the temperature rise of cold water from 75 deg to 80 deg C. You have to add a hot utility then which is against the rules of pinch analysis as one should not add hot utilities in cold section and vice versa because they in turn increase utility requirements on the other side to maintain energy balance. So one should always start from the pinch temperature. The theory on the web cast is correct. Moreover if you do that you may not be able to utilise 10 kw of C1 to cool H2.
Thanks a lot! Excellent explanation. Have you done the heat loop video already?
What if there are is only one feasible match for the hot side?
at 8:20 i thought it is a must for Ch >= Cc at the cold site? can anyone explain
Hello, I'm a Chemical Engineering student. I have a question, we are required to design a heat exchanger network based on an already reported process, what I don't really know is if we can only apply this method to the flows of the heat exchangers that we already have, or if we can also include the flows coming from other equipments (like reactors o flash separation devices)
Quick Question. On the hot side, can you have a heat exchanger where Ch>Cc but part of the Ch stream has already been cooled by another Cc stream?
you saved me. Thanks a alot
Sir, why you took ∆T1 as a hot side and ∆T2 as a cold side ?
Where is the next video about the minimisation of heat ex and identify heat loop? I can't find it..
Thanks for video, it helps me a lot though the exam :)
how or where do you get the values for c (kw/°C)?
is the order of the temperature must be from large to small in each stream?
Your video is really helpful for my task, thank you so much❤️
On the cold side of heat exchanger network
Ch>= Cc
Then how did you do the last heat exchanger
Yes if you start from 30 DegC cold water inlet and match C2 with H3 you will get cold water outlet as 75 degree but then there will be a discontinuity in stream temperature at the pinch point which is 80 degC.. So how do you account for the the temperature rise of cold water from 75 deg to 80 deg C. You have to add a hot utility then which is against the rules of pinch analysis as one should not add hot utilities in cold section and vice versa because they in turn increase utility requirements on the other side to maintain energy balance. So one should always start from the pinch temperature. The theory on the web cast is correct. Moreover if you do that you may not be able to utilise 10 kw of C1 to cool H2.
i already watched this video and this helped me alot... but i asked you for the Network Optimization
Unfortunately, optimization of these networks is more of an art than a science, other factors like equipment cost are important to truly optimize a system. At this time we only have to two videos on the the subject of heat intrgration
ok, thanks alot for your response
what if one stream dosent reach pinch temperatures at all?
what is the following screencast to this please?
What if you don't get a pinch point?
How to design HEN away from pinch?
Amazingly helpful. Prof u made my life easier in just 10min
I made the same mistake, you need to use the 1kW/deg C not the 2 kW/deg C. Then you can get 80 deg C. The 2 kW/deg C is used to obtain the excess 10 kW.
Is there any vidoe of stream splitting and loop breaking, i really understand on this video , i hope so there is screencast on what i mention before
Check nptel lec on process integration
How do are go to previous class
can u pls upload the screencast showing how 2 minimize heat exchangers like u promised? thx
Hello! I've a question over here. We know that AspenTech Plus has this utility to execute pinch analysis. Does Aspen works exactly like what u've expained? It's just for making sure of what Aspen does exactly. Thank you :)
This is made by Aspen Energy Analyzer. This program takes data from simulation and can perform pinch analysis interactively.
Did you ever make the video explaining the loops and paths?
I'm very sorry. We still do not have this screencast.
LearnChemE Did you already do this? I would be very, very grateful!
How do you say that the C1 to H2 is 10 kw, in Cold section. Is the pinch temperature of C2 is changed is from 80 to 35 deg C in Cold Station?...... Then It make sense.
Kindly share your feedback.
Swami Nathan For the first exchange of that stream, the temperature of the cold stream is lowered from 80 to 35 deg C. The remaining 5 deg C difference is then used to cool the H2 stream to 80 deg C, but a further cooling utility is needed to bring H2 down to 30 deg C. Thank you for your questions.
LearnChemE . Do you have any additional videos on Heat exchanger networks (Pinch Technology). If possible can you pass your website so that I can follow it effectively.
Thanks
Nice explained
thanks a lot for saving my time
another great watch!
Are some videos hidden from channel page? I can't seem to find this video on the video tab of your channel page.
+Kieran Nurmi I'm sorry. We're not intentionally hiding anything. How were you able to locate this one? I found it when I searched on the video section of the LearnChemE TH-cam channel. If you can give me some further information, I'd love to fix this. Thanks!
I originally found this episode via the search function as I was looking for a tutorial on pinch analysis. The videos that were previously missing are on the list now it seems. Must have been a glitch with youtube. Sorry for any inconvenience this has caused.
+Kieran Nurmi Great. And thanks, we appreciate the input when our site isn't properly functioning, even if it turns out to be a youtube glitch.
Thanks! Very clear and helpfull
thank you
How do we find pinch temperature?
This video might help explain this...
th-cam.com/video/7PpysQMD0WE/w-d-xo.html
Thanks!
hello has the loops and path video been made?
No, I'm afraid it hasn't yet. Let me move that up on the list. Thanks for asking!
@@LearnChemE please make it!
Did you make a video on identifying heat loops? I can't seem to find it on your video list.
We should posting that soon this week.
Working on heat loops video
Sweet! This stuff is still confusing me hehe. Thanks for your help!
LearnChemE was the heat loops video ever posted? cant seem to find it, thanks.
Sorry for the delay. Hope to have it up this summer.
Links to the heat loop video?
Unfortunately we don't currently have a screencasts regarding heat loops at this time. This is however a topic we are considering.
Okay :( any alternative links I really needed some insight into breaking loop and stream splitting methods
Unfortunately this kind of analysis is based a lot more on the intuition of the person doing it than a specific procedure. In general, a heat loop occurs when there is a clear circular connection between multiple heat exchangers. Alternative exchanger configurations can break them, stream splitting, or replacing an exchanger that is part of a loop with one or more utilities. How these loops are broken, or if they are broken at all, typically has a lot to do with the cost of doing or not doing so. I'm not aware of any specific links that offer more detailed guidelines. I hope this is at least somewhat helpful!
Thks sir
😍
thanks a lot for this.. :)
sorry dude but NPTEL makes hands down better videos