3 replies to this topic

[Engineers Are The Best]

I want good answer to these three simple questions:
1.Why heat transfer dont take place in the bend of a double pipe heat exchanger?
2.How Pressure Is controlled in a Distillation Column?
3.why a level of liquid is kept at the bottom of a distillation column.
I would be very glad if you answer these problems in a simple and concise manner.

[Art Montemayor]

First, I recommend that you not simply assume that these questions have not been asked, addressed and answered in the past in these very Forums. Now, let me address each point you bring up:

1. Why heat transfer don't take place in the bend of a double pipe heat exchanger?
You are making a very big mistake by simply asserting what you believe as a true and factual happening. It just so happens that what you state is NOT TRUE. You are laboring under a wrong belief which you don't identify as to origin. Heat transfer DOES take place in the bend of a double pipe heat exchanger. And that is a physical, hard, fact. How much heat transfer takes place depends on how you design the double pipe exchanger.

2. How Pressure Is controlled in a Distillation Column?
I have not only addressed this subject more than once on our Forums, but I have gone into deep detail as to how this is done. Please use your fingers to select our Forum SEARCH engine and key in the correct key word(s) and you will find my detailed explanation. Don't be lazy.

3. why a level of liquid is kept at the bottom of a distillation column.
This is a good, basic question which I have been waiting for a long time. I like this question because many young engineers and students almost always avoid using their common sense to figure out that you must keep a liquid SEAL (liquid level) at the bottom of a vessel where you are separating vapor from liquid continuously. Common sense tells us you need to do this in order to SEAL off the vapor (or gas) phase away from the liquid drain. If you don't, the vapor (or gas) phase will exit out the bottom – where you don't want it to go! By maintaining this seal as a liquid level, you also identify the location of the seal and control the discharge of the liquid out the bottom by keeping the level constant. This is the GENERAL ANSWER.

The more specific answer as to why you keep a liquid level at the bottom of a distillation column is also due to the need to keep your reboiler immersed with liquid in order to create distillation vapors. Yet another reason is to control the suction liquid flow rate into the bottoms pump. You do this by controlling the column's liquid level. I would have hoped that YOU could have figured that out.

[Allen]

Mr Montemayer has been very kind in giving his usual helpful response but may I ask, have you posed these questions to you heat transfer lecturer and your unit operations lecturer? Also have you checked your text books for information on these issues.

The first question really raises the question of appreciation of heat transfer processes. If I can invert the question - What physical process would prevent heat transfer taking place at the bend? If you consider that question the answer to the original question should be obvious. I believe that 10 minutes consideration of heat transfer principles will answer this question.

I don't want to sound miserable or unhelpful but I've always been a firm believer that people should try and exhaust all lines of enquiry before seeking help. I regularly get phone calls from clients/stakeholders who want help or advice on compliance or technical matters. My first response is always to point them at the available guidance either on our web site or as published material with the advice "Read that advice, it should answer your questions. If after reading it you still have questions, THEN call me."

[Qalander (Chem)]

I want good answer to these three simple questions:
1.Why heat transfer dont take place in the bend of a double pipe heat exchanger?
2.How Pressure Is controlled in a Distillation Column?
3.why a level of liquid is kept at the bottom of a distillation column.
I would be very glad if you answer these problems in a simple and concise manner.

Dear Sir/Madam Hello/Good afternoon,
Should I suggest that we ought to input our best effort and struggle through our nearby guiding curiculum textbooks, seniors/fellow colleagues, peers and then enter for seeking helps at forums.

This I consider a positive/contructive and opimizing of resources approach.
As by profession engineers we must resort to this approach.
Best regards
Qalander