21 replies to this topic

[Art Montemayor]

Kay:

All our senior / professional members want to help you - that I can assure you. But your first post was extremely long!!! I took about 15 minutes to copy it into Word for Windows and it is contained in 54 pages!! That is absurd. We can't possibly handle that much verbiage. We want (and need) specific and detailed basic data and scope of work in order to help you and guide you as much as possible - but 54 pages is ridiculous. (look at the attached copy of your initial post)

Now I see that as I was copying your first post, you returned and submitted an attachment with a reduced post. Thank you! However, I don't see how we can much use all the stuff you crammed into 54 pages. What I've gleaned through reveals that most - if not all - of the data does not apply to what you refer to: a shell and tube condenser.

Please be concise and relevent in giving us the detailed data we require:

• a sketch of the the process;
• description of the type of TEMA condenser you are proposing to use;
• a heat and mass balance showing the total heat transferred - broken down into sensible and latent heat loads;
• a full description of the pressures, temperatures, compositons, and phase of each stream in your process (the condenser); this includes the utility fluid you intend to use as the coolant.
• use an Excel Workbook to submit all your information.

we will check your calculations and review your proposed method of resolving the problem. You should be ready to make detailed references of the textbooks, jounals, or literature that you are using as your source of information to resolve the problem.

As you can see by what I have described as the essential information, we don't need 54 pages of writeup. Our responses will probably be done right on your Excel workbook - in the form of remarks, sample calculations, and comments on your work.

If you are in a hurry because you have waited a long time before asking for help and guidance, then please tell us your timetable and schedule for finishing this assignment. In order to help you, we need to know ALL the facts.

Attached Files

•  Copy of Shell And Tube Condenser Design.doc   213.5KB   560 downloads

[Art Montemayor]

Kay:

Thank you for the detailed explanation. Now we are getting down to the "meat" of the assignment. I haven't had the time to go through all your submitted documents, but after reading your post, I believe I can “translate” what your supervisor is stating.

I think he (or she) is trying to give you a “heads up” (a hint) on what is expected. I think he/she already knows that the heat load to be calculated is going to be rather small. This is a nice gift (the hint), and the advice should be followed – if it has been given in good faith. The advice alludes to the use of what is called an old-fashioned, “double-pipe” heat exchanger. Mr. Donald Q. Kern, in his great book – “Process Heat Transfer” – describes this type of simple, small exchanger and gives examples of how to design it. I highly recommend you obtain a copy of this book either through your tech library or a used source – like the Internet.

This should be a “fun” project because it is rather direct and simple to apply. The basics in heat transfer should be known and applied as well as a design of a vapor-liquid separator after the latent heat exchange in order to effect a phase separation between the resulting cooled gases and the condensate.

I (and probably other Forum members) will work on your submitted documents and keep you informed on our comments, guidance, and recommendations.

[Art Montemayor]

Kay:

I've been on a 3 day trip and see that you are lagging on this subject.

I've tried to accelerate your action(s) on this topic by working on your submitted spread sheet. The simple (and downloaded simulator - Hysis?) and not-applicable Process Flow Diagram does not explain what you write. Note that my PFD is SPECIFIC to the topic at hand. This is the kind of data you should be generating in order to communicate clearly and specifically. Downloading a Hysis simulator diagram (that is NOT A PFD) is just a student's lazy way of avoiding the necessary work involved in communicating your problem. All too many engineering students are refusing to invest time and effort in resolving their own problems. They always look for the "easy" way out of doing work. In this case see how simple the answer is depicted and illustrated.

Also note the comments I've added to your submitted data sheet.

I hope these comments and PFD clearly tell you how to resolve this problem - together with the Don Kern instructions in his book.

Attached Files

•  Mass Balance for Cooler-CondenserRev1.xls   76.5KB   359 downloads

Edited by Art Montemayor, 17 March 2012 - 02:29 PM.
Revision to PFD

[fessy]

Dear Art Montemayor,

Thanks for your reply. You have been very helpful but to be honest i am very confused on what to do next. I am thinking if you have a Skype account and you are free, we could run the design together while on Skype. If you let me know the time and day you will be free that could help. My Skype name is steve Oladimeji. I am based in the United Kingdom. I don't know the time difference of your location and mine. If you let me know, then we could resolve this as soon as possible. If you can add me please. Look forward to your reply. Thanks

Dear Art Montemayor,

I have attached a more coincise mass balance for this condenser design. The unit for every data in the excel is kg/week. Look forward to your reply. Thanks

Kay

Attached Files

•  Excel for design.xlsx   12.68KB   366 downloads

Edited by fessy, 12 March 2012 - 08:57 AM.

[Art Montemayor]

Fessy / Kay Richard (?):

I am also very confused. This thread was started by Kay Richard (male) and now I’m getting a post from “fessy” (female). I don’t know who to address and, to make it even more confusing I’m told a Skype name of “Steve Oladimeji”. How many people are involved here?

I am sorry that “fessy” is also very confused, but I thought my recommended calculation procedure was very direct and simple to follow. I would – as always – be glad to help out any student that needs it, but at present I just returned from a long engineering trip that I took last Wednesday and find myself immersed in a lot of deep problems at work (Yes, I still hold down an engineering position as technical advisor, 10 hours per day at the age of 75). The project that I am advising on has a lot of problems that must be resolved as soon as possible and the only free time I can spare is during my lunch breaks and when I get home for supper – which is monopolized by my wife. Additionally, l do not help other engineers on our Forums on a one-on-one basis. I help a lot of young engineers – especially students – but only on the Forums because that way, the information can be shared with others in a quick and efficient manner. One-on-one help is very efficient; but it only helps out ONE student. The Forum can help a much greater amount of students by being open to all members.

Additionally, you are approximately 8 hours ahead of me. That means that your nighttime is my daytime and vise-versa. Without your detailed engineering calculations, drawings, and scope of work already in place and thoroughly reviewed, a Skype session would, in my opinion, be only a social exchange and not a technical solving session.

You have submitted a couple of tables that show a balance of what is coming out of the furnaces. This is probably only a simulator output – not engineering calculations. You need to calculate the heat load on the condenser, select the cooling medium for the condenser, and calculate the flow rate of the cooling medium. With the heat load, you calculate the required heat transfer area for the condenser. All these calculations should already have been made in the submitted workbook.

I hope this helps you generate your calculations.

[fessy]

Dear Art Montemayor,
Sorry for the confusion. Fessy is my classmate and she has access to my account and so does i have access to her account and we both study chemical engineering.

I really think the best way you can help me is if you can send me an example of an excel spreadsheet for a double pipping condenser design as you have suggested and i can follow it all through as a guideline in designing with my own specifications. I hope that make more sense to you.

Thanks


Kay

[srfish]

This is getting a little weird. Why do you keep ignoring Art Montemayor's advice on getting a copy of "Process Heat Transfer" by Kern? If you can't obtain a copy, there are several other books that have the same title but different authors

[Art Montemayor]

Kay:

I would never rely on Copper as a material of construction for high temperatures. Have you checked the allowable stress value for Copper at your 600 oC?? I think you will find that it will be very weak.

For this type of application I would use Stainless Steel (316 ELC grade) first - if that is OK with the fluids involved.

For my comments on your "calculations" refer to my attached Rev1 of your workbook.

Where is the requested PFD?

Did you read and study the material in Chapter 12 of Kern's "Process Heat Transfer" as I recommended? Those 50 pages are full of calculations examples for your condenser.

Attached Files

•  Double Pipe Heat Exchanger Design Rev1.xls   48KB   238 downloads

[DB Shah]

dear kay,
just had a glance of your worksheet, waste gas of 600 C cooled to 20C with the help of 25C cooling water. You donot have heat sink to cool waste gas to 20C. To achieve 20C waste gas outlet, you must have cold fluid below 20C.

[Art Montemayor]

Kay:

DB Shah can't address your question because you haven't followed prior requests about furnishing a detailed PFD. In fact, you haven't answered most of the questions raised.

Where is the requested PFD? There is no detailed PFD on this thread to date.

[Art Montemayor]

Kay:

I empathize with your confusion. However, it is my humble opinion that this confused situation is caused by your lack of reading and heeding prior comments and recommendations. This now makes the 19^th posting on this topic and we are no closer to closure on this topic than the first post. Please read my comments on my first, initial post:

“Please be concise and relevent in giving us the detailed data we require:

• a sketch of the the process;
• description of the type of TEMA condenser you are proposing to use;
• a heat and mass balance showing the total heat transferred - broken down into sensible and latent heat loads;
• a full description of the pressures, temperatures, compositons, and phase of each stream in your process (the condenser); this includes the utility fluid you intend to use as the coolant.
• use an Excel Workbook to submit all your information.

we will check your calculations and review your proposed method of resolving the problem.”

Now read and heed the comments on the workbook I issued over the last weekend:

“Perceived steps to cool, condense, separate, and control the two Furnaces' flue products stream are as follows:

1) Calculate and identify the size, composition, and conditions (temperature, pressure) of the furnaces' flue exhaust gas stream;
2) Identify the conditions of the cooling fluid (cooling water?) used to cool and condense the flue gases;
3) Fix the outlet temperature of the flue products exiting the cooler condenser;
4) Calculate the cooling and condensation load of the required cooler-condenser;
5) Calculate the required size (heat transfer area) required by a cooler-condenser;
6) Calculate the amount of liquid water condensed and the amount left in the saturated vapor state with the non-condensables;
7) Design the required 2-phase separator required to separate the condensed water from the saturated non-condensable gases going to Nox abatement.”

Without your submittal of a detailed PFD and the basic data requested, it is very difficult for outstanding, professional Forum members – such as SRFISH and DBShah to help and assist you through the simple condenser design and application. SRFISH is considered an outstanding expert in heat exchanger design and his willingness to read this thread and try to help is something that would be all to your benefit if only you furnished him and other members with the information and effort requested.

You (and your colleagues) did not create a PFD. As I told you, all you sent is a simulator sketch that is designed to follow the simulator’s programming steps – it is NOT A PFD. You can (and should have) generate a PFD such as I did. You also could have done the very same thing I did in 45 minutes. It is simple, straightforward, and with the process data tells the reader all that is needed to start the formal calculated process design of the cooler-condenser. You obviously have opted not to do that and you have not responded to my questions and recommendations. That, in my humble opinion, is why you are confused – by your own admission. This cooler-condenser design is a very easy and fun project that is being wasted because of a lack of attention span and willingness to heed experience and recommendations.

You have not stressed me with all the paperwork related to your part I of the project. As I pointed out, all that information is useless to resolving the topic at hand: the process design of a gas cooler-condenser. Your project Part I is not relevant to what you have described as your assignment. Your assignment, as described by you, is a rather simple and direct one. I hope that you can see and admit that and that we can help you in reviewing, critiquing, and commenting on your generated project work such as the PFD, the specification sheet, and your generated, logical calculations.

Do not despair; as I stated, this should be a fun project and if you have studied the material thoroughly in the past you should be prepared to do a good job.

[Zubair Exclaim]

Woooh hold your horses

• You are cooling your process from 500 °C to 20 °C. You should consider two separate condensers one running on cooling water and another on chilled to give a more practical design.
• However You are coming up with a 44 m tube length for the jacketed pipe heat excanger you are considering.. Note that with these lengths you are probably looking at many tubes that fit into a design similar to shell and tube heat exchanger with cooling water on shell side or you are looking at something similar to a convection section of a fired heater with flue gas on box side.
• Also note that you have missed adding heat of condensation load. Use the latent heat of water and its mass flow to calculate it and add to the total duty.
• Also very important: you came up with heat loads by manually inputting mass flow for both streams thats...wrong. For flue do that (plus point 3 above). for cooling water use the duty of flue gas, put in equation q = (m)(cp)(dt) and come up with mass flow . (don’t use that goal seek option in your sheet)
• Your cell in which you calculated length is not clear. I am seeing LN in there; what have you done there? This one should be a simple one......

What you can do is make a tentative PFD and send because there is an option that you guys have missed. 500 °C comiing from furnace is already very high. There should be some process stream available that can bring down those temperature down to a reasonable 250 ~ 260 °C range before coming to you for cooling.

[Bali]

What about usage of shell grade oils as coolant? They are usable for a very long period.. And the amount of heat that can be removed is large