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Can Anyone Solve This Problem On Condensation Of Mixed Vapors?


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#1 sonal gupta

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Posted 02 May 2008 - 04:02 AM

can anyone solve this problem:
2800 lb/hr of aur is saturated with wter vapor at 203 F at 5 psi, and the mixture enters a condenser where it is cooled to 100 F by water from 70 to 100 F.
Available for the service is a 27 in. ID 1-2 condenser containing 462 3/4 in. OD, 16 BWG, 12'0'' tubes arranged for four passes on 1 in. triangular pitch. baffles r placed 24 in. apart.
what is the tue temperature difference? what are the dirt factor and the pressure drop?

#2 Art Montemayor

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Posted 02 May 2008 - 08:18 AM

Sonal:

Is this your homework assignment?
What have you done to try to resolve it?
What is giving you problems?
Do you want us to do your homework?
Have you an assigned textbook for the course you are taking?
Have you looked in Coulson & Richardson’s Chemical Engineering, p. 655?
Do you know what the Logarithmic Temperature Difference is?
Do you know what the “True temperature difference is?
Do you know what the “Correction Factor” is?
Do you know what a “Dirt Factor” is?
Have you read Kern’s “Process Heat Transfer”?

Await your reply.


#3 sonal gupta

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Posted 02 May 2008 - 09:54 AM

thanks for your reply.... Actually this is my seminar problem.... I have read kern and this problem is one of the unsolved questions in the book. I have to design the cndenser on the basis of this problem. I m facing a poblem in the begining itself as the feed compasition is not give... can u help me out with this... thank you..

#4 Zauberberg

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Posted 02 May 2008 - 10:18 AM

It is not possible to cool process stream to 100F if water outlet temperature is equal to 100F - you would need infinite surface area, regardless of the type of application. A definite tube wall resistance is limiting theoretical temperature approach. Furthermore, if you are using 1-2 exchanger this means one shell pass and two tube passes (TEMA E-shell); with this design, it is not possible to have cold fluid outlet tempeature higher than hot fluid outlet temperature - in one single shell. Theoretically, you need more shells for achieving temperature cross.

And your feed composition is given: it is ambient air saturated with water, at 203F and 4psi.

#5 sonal gupta

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Posted 02 May 2008 - 10:48 AM

thanks for the reply..
so.... if it is practically not possible... how am i suppose to solve it... i have to design a condenser on the basis of this solution.. can u suggest me something...?

#6 harsh

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Posted 03 May 2008 - 12:51 PM

Hi Sonal
I think you have to change your utility criterion
Read carefully what Prof. Zauberberg has typed
and Answer ALL the questions given by Prof. Art Montemayor.
think on it, then you will get your design

#7 Qalander (Chem)

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Posted 06 May 2008 - 10:56 AM

Dear Sonal,

I don't quiet remember if your referred question has some lower than atmospheric steam side pressure i.e. psia; thereby the phase change could be sustainable at lower temperature, but i am not very sure about the accuracy in this regard.

Best Regards
Qalander

#8 Art Montemayor

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Posted 06 May 2008 - 02:18 PM

Sonal:

You have not taken the time to answer our questions. Now you return and further add more data that this is a problem from Kern's Process Heat Transfer - but you haven't had the courtesy to tell us where in Kern the problem is located.

You are turning in circles without any direction or knowledge of what confronts you. This is revealing itself through your inaction and continuing self-pity. If you had only followed what we asked and done your share of the work, you would have resolved the problem by now. You have been told that contrary to what you asserted, the problem did have a clear and definite composition of the vapor into the condenser: the air is saturated. You have not admitted that you were wrong and that you do, indeed have all the data available to you. When you ask for help from others you are already tacitly admitting that you don't know how to achieve the answer. So, why do you insist on doing it your way and not our way?

Your way is the WRONG WAY. The sooner you admit that to yourself and to others, the faster you will learn some basic engineering - learning from the experiences of others. Good luck.





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