liquid level in Shell and Tube flooded evaporators

[cygbob]

i know in the ammonia flooded evaporators design there are two methods for liquid and vapor to separate. one is the separation is provided above the tubes in the shell, another is with an auxiliary vessel above the main evaporator.

the questions are:
1. if i take the first one, how to decide the liquid level and the tube arrangement in the shell.
2. if there is an auxiliary vessel, should the tubes arrange all of the shell or also need some space? and the liquid level?
3. how to calculate the auxiliary vessel?

is this ok with Froen??

thanks

cygbob

[Josip]

Hi, cygbob :)


i know.....
..... the questions are:
1. if i take the first one, how to decide the liquid level and the tube arrangement in the shell.
2. if there is an auxiliary vessel, should the tubes arrange all of the shell or also need some space? and the liquid level?
3. how to calculate the auxiliary vessel?

is this ok with Froen??

thanks

cygbob

your question is not easy to answer....just opposite;)
please, download and read this...

http://neatbook.org/w/wolverine%20tube%20heat%20transfer%20data%20book.php

this one will tell you a lot....almost all :eek:
http://www.engr.iupui.edu/me/courses/shellandtube

some theory needed in practice...updated 2007... good for learning...

http://www.wlv.com/products/databook/databook.pdf

www.wlv.com/products/databook/db3/DataBookIII.pdf (http://www.wlv.com/products/databook/db3/DataBookIII.pdf)

...hope you will find all answers you need and some more;)

....hope you will find those links useful....enjoy:p

... of course if this is not enough ..... you can do Google or Google chrome browser ...


Best regards, Josip :)

[TXiceman]

No real easy answers...

In TEMA (Tubular Exchanger Manufacturers Association) terms,
BEM is a typical shell and tube design wher you use a separation drum over the exchanger. Typically you will leave the top 2 or 3 rows out of the shell. The vessels will have 2, 3 or 4 risers to connect the shells. Riser design is critical.

One that has the disengaging area in the sheell can be a BEM that is only 1/2 full of tubes. Ans alternate design is a BEU or BKU, often refered to as a kettle type evaporator. The disadvantage of this type design is the extra refrigerant charge required to flood the tubes.

On either design, you set the liquid level controller to operate about 2 or 3 rows of tubes below the top of the tubes. The agitation from boiling keeps the top row of tubes wetted at full load and at reduced load, the slight loss of wetter surface doe not matter.

Next issue is the proper liquid entry into the evaporator...lots written on this, but I prefer a perforated distributor plate below the tubes. Larger vessels may require multiple entries.

Next is the proper number and design of vapor outlets from the exchanger.

There is very little written on the design of flooded evaporators and vendors guard their designs. You will probably need to hire an consultant to do the initial designs for you.

Ken

[cygbob]

thanks all for the useful information.

i think some of the questions need the experiential knowledge such as in which case you use the auxiliary vessel but not leave many space in the evaporator.

thanks again!
cygbob