evaporator

[ah fai]

Hello all,

what is the difference between ammonia and ***** fan blower type evaporator???
and it is possible to change the ammonia type to ***** ???
the ammonia system using pump and ***** system using expansion device on the evaporator.

Thanks in advance

[danny_s_pike]

Hi Ah Fai, the design concept of both evaporators are basically the same, however, there are some very big differences. When you are talking about an ammonia evaporator using a pump, you are talking about a high capacity, forced system. Although ***** evaps can be quite effective, they cannot match the refrigeration capacity of a similar sized ammonia evap, because of the system attached to it.

Many ***** evaps use copper fittings, or even the tubes in the evap itself may be made of copper. You won't find any copper on an ammonia evap, as ammonia, especially when moisture is present, quickly destroys copper.

[The MG Pony]

Allot of ***** (HFC/Hcfc, CFC) Use aluminium and copper or all aluminium Evap! NH3 will distroy both in very very short order.

To swap over will requier the whole system to be re-engineered aqnd sized from scratch

The amonia system will be a flooded type evap made of all carbon steel or Stainles steel, Now I have heard of flooded ***** systems befor but am unsure of their prevalence in the field, again how ever to impliment this system you will need a compleat redesign and rebuild of the whole plant.

[ah fai]

IC, actually i have some used aluminium make ammonia flooded type evap but i just want to get some advise if i plan to use for ***** system.

can you please share some formula, calculation for flooded type ammonia evap application and expansion type ***** evap ..
Thanks

[Josip]

Hi, ah fai :)


Hello all,

what is the difference between ammonia and ***** fan blower type evaporator???

and it is possible to change the ammonia type to ***** ???

the ammonia system using pump and ***** system using expansion device on the evaporator.

Thanks in advance

main difference is in construction ...

construction of ammonia evaporator must be to allow to collect oil at the bottom collector and drain it out from time to time i.e. when is needed ... what is opposite to ***** systems where we need evaporator construction to return oil back to compressor ...

... then very important is fin spacing to use evaporator for positive or negative temperature or for freezing ...

of course it is possible to adopt ammonia evaporator for ***** system, but that can be very hard and expensive .... it will have reduced capacity due to expansion device ...

my suggestion is to think all about before final decision ...

further, it is possible to pollute new system with oil residues or with corroded steel particles from evaporator if it is too old and if there were water present within ammonia system ...



Hope this is of some help to you ...

Best regards, Josip :)

[Josip]

Hi, ah fai :)


IC, actually i have some used aluminium make ammonia flooded type evap but i just want to get some advise if i plan to use for ***** system.

can you please share some formula, calculation for flooded type ammonia evap application and expansion type ***** evap ..
Thanks

Are you sure ... probably only aluminum fins .... pipes are made of steel ....

use this link where you can find out more about evaporators

http://www.luve.it/cms/view/home/s4

Best regards, Josip :)

[Magoo]

Aluminium tubed ammonia coils are common, conversion to ***** is possible but need to be thoroughly cleaned internally. You may loose some performance in capacity by converting to a ***** based refrigerant

[ah fai]

Ic, correct me if i am wrong, in my side, for what i see in the ammonia flooded type coldstorage at -25deg C all the evap dont have drain valve under the evap, but the oil is return to low temp receiver and oil collector under the low receiver.

the evap in fully made of aluminium (fin or tube), and use for low temp sprial freezer at -45 deg C.

[The MG Pony]

Amonia eats aluminium! I can assure you the tubes will NEVER be aluminium!

There can be a couple of methodes to return the oil out of amonia systems pending on design of the evap.

[Josip]

Hi, ah fai :)


Ic, correct me if i am wrong, in my side, for what i see in the ammonia flooded type coldstorage at -25deg C all the evap dont have drain valve under the evap, but the oil is return to low temp receiver and oil collector under the low receiver.

the evap in fully made of aluminium (fin or tube), and use for low temp sprial freezer at -45 deg C.

First, ammonia is harmless to aluminum ... all pistons within reciprocating refrigeration compressors are made of aluminum, also metal gaskets for refrigeration compressors (STAL) are made of aluminum ... it is harmful to cooper due to chemical reaction between cooper and ammonia, but there are some bronze for shaft seal rings resistant to ammonia ...

we are not able to correct you, we can believe ... evaporators can be hot galvanized (it is common for ammonia evaporators made of black steel, both pipes and fins) but it is looking like made of aluminum in case if you are far from evaporator... can you give us some info regarding brand and type of evaporators you saw, please?

there are some big problems to weld aluminum pipes and that is the main obstacle for wide use of aluminum in refrigeration .... you can find more about on internet ...

it is possible to have evaporator construction together with headers to have a slope back to low temperature separator where we can collect oil and drain it from oil separator with heater located beneath the separator ...

Best regards, Josip :)

[The MG Pony]

really? when ever we have had amonia near alu it is disintigrated, and that is just ambient, Alu is sensitive to alkyline substances.

well then if Alu can be used with NH3 then that makes things allot easier on a scaled down system

[ah fai]

Anyway, i will collect and share with your guy about the evap. Between, can your guy show me about how to sizing the compressor, condensor, evap for NH3 flooded system ? or how should i start learning from cause i am interesting in NH3.

[Josip]

Hi, The MG Pony :)


really? when ever we have had amonia near alu it is disintigrated, and that is just ambient, Alu is sensitive to alkyline substances.

well then if Alu can be used with NH3 then that makes things allot easier on a scaled down system

I'm ammonia guy for 30+ years and no problem with ammonia and aluminum ... maybe I had a good luck ;)


Aluminium and chemicals

Thanks to the protective properties of the natural oxide layer, aluminium shows good resistance to many chemicals. However, low or high pH values (less than 4 and more than 9) lead to the oxide layer dissolving and, consequently, rapid corrosion of the aluminium. Inorganic acids and strong alkaline solutions are thus very corrosive for aluminium.


Exceptions to the above are concentrated nitric acid and solutions of ammonia. These do not attack aluminium.



link is here http://www.aluminiumdesign.net/design-support/aluminiums-corrosion-resistance/

http://www.achrnews.com/articles/aluminum-evaporators-for-ammonia

http://books.google.hr/books?id=iEeiQEeLOmYC&pg=PA157&lpg=PA157&dq=ammonia+corrode+aluminum&source=bl&ots=EIp8UXP_Vj&sig=d0jtYJ0ndn8CnUrAcSk6ABRr_UA&hl=en&sa=X&ei=3hXgUdnNJsm74ASKn4DgDw&ved=0CD0Q6AEwAg#v=onepage&q=ammonia%20corrode%20aluminum&f=false


but for sure there is more on the net ....

Best regards, Josip :)

[The MG Pony]

I am not arguing with you, and I do trust you, I know your experience! I was just surprised based off just what I have observed with evaps around small amounts of ammonia and all ways thought it had been the ammonia doing the damage, then to hear they are compatible makes me wonder what the real issue was all that time ago.

Just means I need to rethink a whole area of understanding when it comes to that now!

[Josip]

Hi, The MG Pony :)


I am not arguing with you, and I do trust you, I know your experience! I was just surprised based off just what I have observed with evaps around small amounts of ammonia and all ways thought it had been the ammonia doing the damage, then to hear they are compatible makes me wonder what the real issue was all that time ago.

Just means I need to rethink a whole area of understanding when it comes to that now!

Please, sorry ... my mistake if I sound arguing ... lost in translation ... English is not my mother tongue and sometimes can sound rough ... I was trying to say ... during all my experience 30+ years I never ever saw any problem using aluminum in contact with ammonia ...

maybe you are right ... because there are a lot of aluminum alloys for casting ... mixed with cooper, magnesium and others not resistant to ammonia vapors and some other gases present ... seems only pure aluminum is OK to be used with ammonia ...


Best regards, Josip :)

[ah fai]

Hello
Cant get any details for the evap cause it made from china and about 8 years ago.

anyway, how to sizing a evap from a coldstore,

Thanks.