Low-cost Heat Exchanger Thermal Design Options? 1

[Christine74]

Are there any good, inexpensive software packages out there for shell-and-tube heat exchanger thermal design/evaluation? Which would you recommend, and about how much does it cost?

I think we need something that's more advanced than the Kern/Bell-Delaware method, but it doesn't need to have a built-in database of all the fluid transport properties as we would be using it infrequently. What do you suggest?

Thanks,

-Christine

 

[Montemayor]

Christine:

What do you identify as “inexpensive software”? How much are you willing to pay someone to design a heat exchanger for you? The least expensive program I’ve heard about was approximately $600 and I don’t believe my employers or clients would have put 100% faith on its results.

There’s no way to avoid the inevitable question that is put forth the moment a process design is put on the table for analysis: who (or what program) did the calculations and what is the experience and dependability factor supporting it? The facts are that if you or I don’t have sufficient experience and a recognized track record in designing heat exchangers, no self-respecting engineer is going to put much faith in our calculation results. That’s the bottom line. For an enterprise to invest hard cash on a design, it is going to demand credentials and warranties on the results. That is the principal reason why people working in production, process plants, or anywhere other than a Heat Exchanger design/fabrication shop are never seriously put to the task of designing or building a heat exchanger. You may be able to specify a terrific heat exchanger, but unless you’ve had at least 10 – 20 years designing and building them I wouldn’t attempt to apply your product to a multi-million $ process plant investment. It just doesn’t make for common sense. Recognized computer software for the design of heat exchangers costs a lot of money to write, advertise, sell, test, and warrant. All this money has to be recovered with sufficient additional return on the investment. And all of this is based on getting acceptable results with repeatability and accuracy. I don’t think you’re going to find such a computer program for under several thousand dollars.

Contrary to what you infer, Don Kern did not contribute directly to the Bell-Delaware method of calculating the shellside pressure drop and heat transfer in a heat exchanger. I’ve taken Dr. Kenneth J. Bell’s seminar course on exchanger design and I’m also familiar with the history of the method in question. It was first introduced at the University of Delaware in 1947 where the principal investigators were professors Olaf Bergelin and Allan Colburn. Even Ken Bell, who has done a lot of work with the method, calls it The Delaware Method. This method is based on sound, logical algorithms that are still in use in today’s computer algorithms. I know of no “better” advanced methods than the logic that went into this method.

I am aware of several instances where large operating process companies took on the design and fabrication of “special” heat exchangers. All of these experiences resulted in total failures. And I’m talking about some really large capital enterprises. The last one I remember happened at a not-to-be-identified world-scale chemical company’s corporate engineering where they got the bright idea that they knew enough to design a very large overhead condenser on a nitric acid vacuum tower in a world-scale process plant in China. The result was an expensive and embarrassing abortion that had to be explained away. I know because 2 years later I came along and instead of following suit, I went directly to the experts I knew who had done this before and would warrant the results: Graham Vacuum Systems. They did the design and supplied the equipment for the budgeted price and time (which was 40% of the China job) and it worked like a Swiss watch. I have learned from other people’s mistakes and failures – something I was taught to always follow while I was in school.

Unless you have extensive experience designing heat exchangers, I would advise you to stick to the estimates at the viability and proposal stages and leave the hard, final design to the experts who do it for a living -and competitively. Any exchanger evaluation done before hard quotes are solicited is just at the estimate (or "best guess") level. The real truth about what is required, what size it will be, and what it will cost will only be revealed when the experts turn in their quotations based on your specifications.

I hope this experience is of some help to you.


Art Montemayor
Spring, TX

 

[Shmulik]

I completely agree with Mr. Montemayor.
Old thumb rule is you don't pay you don't play.

There is a free non-guarantied calculator. I would not use it for more then a first shut evaluating:

http://www.freecalc.com/hxfram.htm

In case the situation is you have a specific heat transfer process, you may find a high reliability solution in a relatively low cost at the following:

http://www.lv-soft.com/software/fachbereiche/waermeuebertrager/index.htm

 

[lengould]

For estimations you might consider this site:

http://www.processassociates.com/process/tools.htm#heat

but keep in mind Montemayer's inputs.


Pechez les vaches.