7 replies to this topic

[learner]

Hello everyone

i hope somebody solve this problem.i want to chill water with butane.but even i use temperature approach but still i get temperature cross in hysis.

here are data:

water: T in=9.5 C

Pin=500 kpa.

F=110,000 kg/hr

Comp.=20% MEG,80%H2O

T out =? to be calculated by Hysis,preffered 5 degree C

P out=430 Kpa

Butane:T=-4 C to -2 C

Comp=0.01w/w propane,0.59w/w n-butane, 0.40w/w i-butane

F=5000-6000 kg/hr

P= pump discharge=6-8 barg, it can be entered to the shell by every pressure,

the butane exit from the shell should have 500 mbar pressure too, because i need to send it back to the tank which has a pressure about 150 mbarg.

i tryed +5 C butane as it has more vapour pressure but still temperature cross remain.

i hope to find a way to use butane.

thanks for your attention 

Edited by learner, 14 March 2013 - 11:31 PM.

[thorium90]

Its obvious why it wont work. The amount of heat to be removed from the chilled water I estimate about 580 kW. The amount of heat to add to the butane is <30 kW. Think the answer is obvious why there is a temperature cross

Edited by thorium90, 13 March 2013 - 08:46 AM.

[Art Montemayor]

Learner:

 

It is quite apparent that you haven’t learned yet how to deal with a simulation program.  All simulation programs are basically STUPID.  They can’t logically determine or guess what you want to do if you don’t feed them the correct and total input data.  If you put in garbage, they will spit it out as garbage.  You must learn engineering first before trying to feed HySys garbage.

 

Additionally, your data is all screwed up.  How can you reasonably expect us – and much less, HySys – to know what you are putting into the proposed heat exchanger if you give input stream data like:

 

Butane:T =-4 C to -2 C

Comp = 0.01%w/w propane, 0.059w/w n-butane, 0.40w/w i-butane

F = 5000-6000 kg/hr

 

Do you expect us to believe that you are putting in a stream that has a total of (0.01+0.059+0.40) = 0.469 %w/w hydrocarbons and 99.531 % of NOTHING???  This doesn’t make any sense and I can see why HySys is having problems trying to figure out what you want.

 

As thorium90 also infers, you probably haven’t even done a simple, preliminary heat balance to figure out if indeed the proposed 6,000 kg/hr of refrigerant can do the job.  No one (especially HySys) can tell if you have a temperature cross in an exchanger if you don't state the type of exchanger.  For example, a true counter current exchanger will not produce a temperature cross.  HySys is giving a warning signal that something is not correct; in this case it is throwing out temperature cross for one reason or another - but your data are screwed up.

 

Why don’t you start all over again, generate and submit a simple sketch and basic preliminary calculations in a spreadsheet so that we can all understand what you are trying to do with/to Hysys?

[Pilesar]

Refrigeration cooling is due to refrigerant boiling. Specify your heat exchanger so that the cold side outlet is 100% vapor. The inlet temperature of your refrigerant is not the level where the bulk of the cold side heat transfer takes place. Check the dew point temperature of your refrigerant stream at the outlet pressure you require. You will probably find it very close to the inlet water temperature. Reduce your refrigerant outlet pressure and you should be fine.

[thorium90]

I forgot to add, I assumed he had a typo and he meant 0.59 and not 0.059, so 0.01+0.59+0.40=1.00.

 

Still, the heat balance needs some work

[learner]

thorium90:

Thanks,your assumption is correct,you utilized your engineering sense,it was my mistake during typing.as butane is refrigerant,so n-butane and i-butane are dominant.the composition is: 1%w/w propane, 59%w/w n-butane, 40%w/w i-butane

Edited by learner, 15 March 2013 - 12:20 PM.

[learner]

Art Montemayor:

You said above how can I expect you to answer,Well I better tell you that I never expected YOU to answer,as I got to know you by reading some of your posts in this forum,but never get any usefull word in them. you just complaining the lack of data,and what people should include in their post,while the other people trying to figure out and help.If you need more data,well you can ask.look at thorium90 reply,he undrestood what I meant,as he has engineering sense.So the only thing that you have to do,is not to say anything when you don't know about something.

I have read another reply of yours that you blame someone for his misspelling or mistake in writing I by small letter.

Please when you don't know anything ,just stay away, you don't need to answer every posts.

When somebody make a post and asks something,you are always the first one answering that,writing a book of nonscence.

Just look at what  Pilesar and thorium90 wrote.Did they blame? they answered and really helped.  

Thank you

Edited by learner, 15 March 2013 - 02:05 PM.

[thorium90]

learner, I understand what you mean, but you shouldnt make it a habit to miss out data or make mistakes on the numbers. Even putting the wrong units can create incidents, just google Mars orbiter.

https://www.google.c...iw=1920&bih=863

 

I understand because as a student, I also made such mistakes before, like converting Pa to Bar, there are so many digits in Pa, sometimes I counts the digits wrongly, haha.

I also understand not providing enough data because if one doesnt understand the problem, one would not understand what information was relevant anyway and would therefore be unable to provide the relevant information. To a more experienced person, it would be obvious what information would be needed to solve a particular problem. But to someone who has not understood the problem, he would have difficulty even understanding what is required.

 

Take for example some of the following threads. (No offense intended to the OP's concerned). These are clear examples of someone who has no idea what he is looking at. Some characteristics are; very short questions (one or two sentences), lack of spelling and grammatical accuracy.

http://www.cheresour...ner-is-cleaned/

http://www.cheresour...-vacuum-column/

 

Some are based on real concerns but demonstrate clear lack of understanding of the problem at hand. Some characteristics are; relatively short questions (about 3 to 10 lines), any information provided has a poor link to what is required

http://www.cheresour...ng-feed-limits/

http://www.cheresour...l-distillation/

http://www.cheresour...-of-condensate/

http://www.cheresour...e-calculations/

http://www.cheresour...o-hydrocracker/

http://www.cheresour...harge-pressure/

 

But thats not to say that being more specific means you will get a good reply. Sometimes, the problem is just too specific and/or complicated and requires someone with the specific expertise to answer. However, such a person might not be reading that thread or be interested in registering just to reply.

http://www.cheresour...ribution-input/

http://www.cheresour...a-gas-pipeline/

http://www.cheresour...p-in-dnv-phast/

http://www.cheresour...-dl-methionine/

http://www.cheresour...on-calculation/

 

To summarise, it is important to be clear and concise in the description of a problem statement. Try to avoid ambiguity statements or arcane acronyms. As this is an engineering forum, pressure, temperature, flow and composition information should be some of the foremost information to provide.

 

Some examples of clear, descriptive and well posed questions.

http://www.cheresour...mpressor-power/

http://www.cheresour...rties-in-excel/

http://www.cheresour...al-degradation/

http://www.cheresour...-on-equipments/

http://www.cheresour...f-storage-tank/

http://www.cheresour...rs-application/

 

 

Hope this is not too lengthy, its just an extremely brief personal psychological analysis of the people who frequent this forum and my thoughts on the extension of human factors engineering in this aspect.

Edited by thorium90, 16 March 2013 - 11:27 AM.