2 replies to this topic

[ayan_dg]

Please discuss the following with respect to TEMA BEU Shell & Tube HX

Tube length is fixed say 6400 mm
Tube OD is fixed say 3/4"
Tube thickness is fixed.
Shell internal dia is fixed say 1500 mm

What will be the effect on tube count , tube & shell pressure drop, tube & shell velocity when the following are varied

1) Tube pitch
2) Baffle spacing
3) Use of segmental or double segmental baffle
4) Baffle cut

Please discuss

[Art Montemayor]

Ayan:

I am very surprised at your request for us to resolve a practical and down-to-earth engineering homework problem that does not require any theory or mathematics. I would like to think that this is the type of engineering test that brings out the real, good, practical and best logical engineering thinking that is being taught and demonstrated in all our engineering universities.

You are asking for "discussion" instead of answers, and that is what I present. I believe this series of questions are so practical and obvious in response that it depresses me to think that a clever, competitive engineering student in India can't come up with the logical responses. Why haven't you presented YOUR thinking and "discussion"? After all, it is YOUR PROBLEM. Let me give you examples of what upsets me about your lack of attacking these questions:

1) If you increase the tube pitch in a fixed diameter, how can it be that you can't VISUALIZE that the quantity of tubes in that exchanger will diminish? The next obvious "elementary deductions" (as Sherlock would say) are that the tube pressure drop INCREASES, the shell pressure drop DECREASES, and the shell velocity DECREASES!

2) The same type or kind of practical thinking applies to the rest of the questions.

The main point I want to discuss here is that how can it be that engineering instructions and training have come to a point where we can't even VISUALIZE what is happening in our proposed solutions and investigations. We are supposed to be training human engineers - not robots! We cannot rely on merely using computers to spit out "answers" that we don't even know how to interpret or check out. That is NOT ENGINEERING. The title of "Engineering" comes from the Latin; it means TO USE ONE'S INGENUITY. It is akin to being genius. In other words, we are expected to be using our MINDS - not relying on machines to do that for us.

In a way, I am very glad that you brought forth this type of "problem" because I sincerely hope that our Senior and experienced engineers on our Forums will assist me - and you - in expounding the fact that this is very type of everyday thinking that we professional engineers have to do when we are at work. We are not responding to queries and challenging problems by quickly running to a computer and seeing what comes out. We are expected by our superiors to stand there, carefully listen to the problem at hand, ask the pertinent and important questions that are focused on identifying all the needed problem inputs and then carefully think out and respond with a logical, practical, and possible solution. We may, from time-to-time employ hand calculators and even computers to confirm or check out what we already suspect. But the basic strength of our solution is our belief in our training and abilities to analyze and visualize that our answers are sound and will work. Understanding the problem is a thousand times more importnat than "crunching" out the numbers. A robot (like a computer) can easily crunch out numbers - but it CAN'T THINK or visualize.!

[djack77494]

Good topic and excellent reply by Art. Why don't you think about the likely effects of the parameters you are interested in and see if you can predict their impacts. Then write back to the forum with your opinions and solicit comments as to any logic errors that might have been commited. I'd be happy to respond, and I'm sure others would too.