Compact Heat Exchangers for Ammonia
Here is a new thread for the subject.
Re: Compact Heat Exchangers for Ammonia
Since we have a new subject, let's add some material for everyones review. If others find some interesting material, please go ahead and post it.
http://www.eng.hawaii.edu/ME/Weilin%...due/P-C-03.pdf
http://www.xpedio.carrier.com/idc/gr...f?SMSESSION=NO
I believe if this technology is to be used for refrigeration (especially industrial refrigeration) we have to be aware of certain limitations, i.e., surface fouling and low temperature oil circulation.
Under the topic of surface fouling I can see two distinct problems with this; ice/frost when used as an evaporator, and, mineral precipitation if used in an atmosphere containing dissolved minerals (such as an evaporative condensing function).
Secondary surface such as fins are cheap heat transfer surface, but the use of fins also includes the awareness that restriction of air flow will rapidly decrease the exchanger capacity. For this reason, wide fin spacing is a requirement for frost forming surfaces.
If the fin spacing is increased to compensate for this continous requirement of potential fin bridging, what would the expected performance increase be for a microchannel exchanger when compared to tube & fin exchangers?
An additional similar problem also relates to the fins. It can be difficult enough to keep prime surface tubes clean in an evaporator condenser. Adding secondary surface to evaporative condensers would make for some interesting maintenance issues I believe.
I'm not trying to say we should not be investigating new technologies. Only that we should be prudent in the application of those.
I have a feeling this thread will generate some interesting observations and comments.
Best Regards,
US Iceman
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
US Iceman
Thanks a lot for above reading materials.
Quote:
Originally Posted by
US Iceman
I believe if this technology is to be used for refrigeration (especially industrial refrigeration) we have to be aware of certain limitations, i.e., surface fouling and low temperature oil circulation.
. . . . .
I'm not trying to say we should not be investigating new technologies. Only that we should be prudent in the application of those.
I have learned early in life that we need to ask lots of questions to be able to learn more. Also, the shortest way to learn is asking guys that have the experience to share.
I hope somebody who have experimented, applied & installed these products will come forward and share their knowledge. :)
Re: Compact Heat Exchangers for Ammonia
Good afternoon Darshi,
Thank you for the link. I would be grateful if you could let me know the name of the manufacturers so that I may contact them and try using them in my future projects.
With best wishes,
Re: Compact Heat Exchangers for Ammonia
Thank you US Iceman for the link. I shall be thankful if you could kindly elaborate on the constructional features of these heat exchangers.
I was planning to use Gasketted Type PHEs as ammonia condensers. But now with Darshi coming up with this type, I would like to learn more about it.
As Fredy as has said it that if some one who has used these could please come forward and explain more in detail, it would be helpful.
With best wishes,
Re: Compact Heat Exchangers for Ammonia
Well, to be honest I do not have any first hand knowledge of these exchanger types (other than my vehicles radiator).
I tend to approach new technology cautiously and lean on my background doing weird applications for various refrigeration systems.
The first thing I always look for is; "what can go wrong"? That helps to keep happy customers as no one wants to be used for experimentation purposes.
I've used the gasketed PHE's before with good success and also the brazed PHE's. Both are a good product.
Obviously, Darshi does have some exerience with these and I do not mean to prevent him from offering comments. That is certainly not my intention. I'm only suggesting we need to carefully review the application parameters to make sure we do not create other problems, that might not have been recognized.
Re: Compact Heat Exchangers for Ammonia
Hi,
Quote:
Originally Posted by
US Iceman
The first thing I always look for is; "what can go wrong"? That helps to keep happy customers as no one wants to be used for experimentation purposes.
I've used the gasketed PHE's before with good success and also the brazed PHE's. Both are a good product.
Obviously, Darshi does have some exerience with these and I do not mean to prevent him from offering comments. That is certainly not my intention. I'm only suggesting we need to carefully review the application parameters to make sure we do not create other problems, that might not have been recognized.
Yes, it is better to use known HE instead to make very expensive mistakes;)
Best regards, Josip :)
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
Samarjit Sen
Good afternoon Darshi,
Thank you for the link. I would be grateful if you could let me know the name of the manufacturers so that I may contact them and try using them in my future projects.
With best wishes,
Hi Samarjit,
is this the link you need?
w . idalex. com / applications / Mcondenser. htm
regards :)
Re: Compact Heat Exchangers for Ammonia
Thank you Handyman 1. I have visited the idalex web site and gone through the details.
It appears that as far as of now there has not been many users of this system. The gasketed PHEs would be a better deal in our country, as generally the water is pretty hard and they have to be treated to make it useful. With gasketed types, we can clean it if required.
However it would be nice if some users of the condensers which Drashi has said provides us with his experience with such type of units.
Re: Compact Heat Exchangers for Ammonia
Hi:)
I would think finned surfaces cooled by evaporation would only work if the water treatment was perfect:)
otherwise scale would build.
The question is not where it is a more effective way of cooling, but whether water treatment is up to the task of looking after the heat exchanger in the long term.:)
Kind Regards Andy:)
1 Attachment(s)
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
Andy
Hi:)
I would think finned surfaces cooled by evaporation would only work if the water treatment was perfect:)
otherwise scale would build.
The question is not where it is a more effective way of cooling, but whether water treatment is up to the task of looking after the heat exchanger in the long term.:)
Kind Regards Andy:)
Dear Andy ,
You are right about the water treament if one sprays the liquid water but not true for adiabatic evaporation.
I am attching a note ,I prepared for evaporative condensing .
It will be self explainatory :)
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
Darshi
Dear Andy ,
You are right about the water treament if one sprays the liquid water but not true for adiabatic evaporation.
I am attching a note ,I prepared for evaporative condensing .
It will be self explainatory :)
Darshi:)
can you please explain the differance between Adiabatic cooling and the cooling we associate with evaporative bare tube condensers:)
Thank you:)
Andy:)
Re: Compact Heat Exchangers for Ammonia
Dear Andy
May be the attached document with my last post will explain the process, however a quick reply to your quarry is here:-
Bare tube evaporative condensing:
Water is sprayed on high temperature bare tube surface for heat exchange.
The pure water evaporates and cools the rubes and impurities (salts) remain stuck to the surface as scales ..The heat exchange takes place between water at wet bulb temperature of the location
Compact Mass Exchangers(CME):
These exchangers are made of large surface area matrixes like brass wire mesh., paper or plastic corrugated surfaces which are wetted with water . The simple example will be an evaporative cooler fill or cooling Tower fill.
Air for cooling the condenser is first passed over the wetted surface and cooled evaporativily to near the wet bulb temperature and this cooled air now passes over the finned condenser heat exchanger to transfer heat. The air touching the fins and tubes has water in vapour state and ca not carry salts like the liquid water. Hence there is very little chance for corrosion.
Generally, the wet bulb temperature never exceeds 300 C .In tropical climates, the coincident wet bulb may be often as low as 18 -230 C at temperatures exceeding 400 C.
Re: Compact Heat Exchangers for Ammonia
Now I have a better idea of what's being described as an evaporative condenser. The process shown in the brochures is not what we would typically refer to as an evaporative condenser.
The product is an evaporative process to pre-cool the air stream on an air-cooled condenser. If the micro-channel heat exchanger was used with this technology it might make for an interesting study or trial.
But I would emphasize I would not make the trial as part of a normal project, UNLESS, the client fully understood what was being attemped and agreed to bear the risks, in writing.
I still feel there might be some additional risk with using this type of heat exchanger in a potentially dirty service (and outdoor air is dirty with a high potential for air borne debris).
I know from past experience it is very difficult to keep air-cooled condensers clean, mostly due to the fin spacing and coil depth.
The new heat exchanger surface would not appear to correct any of those problems.
It's an interesting experiment, and I could see how it would have a lot of merit for high dry bulb/low wet bulb environments, such as the Middle East.
I have spent considerable time as an application engineer too, so I'm not too crazy about the pen pushing type mentioned. Although, I do know the type you are describing. These usually revolt at the first mention of thinking outside the box.
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
US Iceman
I have spent considerable time as an application engineer too, so I'm not too crazy about the pen pushing type mentioned. Although, I do know the type you are describing. These usually revolt at the first mention of thinking outside the box.
Hi US Iceman,
When this particular product was mentioned in this thread, i also inquired from idalex.com with the purpose of purchasing the Idalex Refrigerant Condenser. I intend to use it in my prototype unit for a marine application.
The product is not yet available. Am sharing here a portion of their email:
Quote:
Thank you for your interest in Idalex. From your comments, it looks as though you are interested in HVAC applications of our technology, which for now is limited to Coolerado. The Idalex refrigerant condenser is at least a year away from commercialization.
There are always those that wanted to use new products but it always equate to giving the 3 Ts (Time, Treasure, Talent). Very few have the luxury of giving all those 3, especially the TIME.
As an application engineer, we always know that TIME (to make a prototype and gathering the test data) is the hardest one to find.
With RE forum, we can make the TIME somewhat shorter by asking some members to share their experiences.
For this, i am thanking those that share their experiences.
Of course, as we always know: giving ideas are great but then talk is cheap. . . :).
That's why application engineers always loathe those pencil pushers. . . . :)
Regards & Thanks.
Winfredy
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
US Iceman
Now I have a better idea of what's being described as an evaporative condenser. The process shown in the brochures is not what we would typically refer to as an evaporative condenser.
The product is an evaporative process to pre-cool the air stream on an air-cooled condenser. If the micro-channel heat exchanger was used with this technology it might make for an interesting study or trial.
But I would emphasize I would not make the trial as part of a normal project, UNLESS, the client fully understood what was being attemped and agreed to bear the risks, in writing.
I still feel there might be some additional risk with using this type of heat exchanger in a potentially dirty service (and outdoor air is dirty with a high potential for air borne debris).
I know from past experience it is very difficult to keep air-cooled condensers clean, mostly due to the fin spacing and coil depth.
The new heat exchanger surface would not appear to correct any of those problems.
It's an interesting experiment, and I could see how it would have a lot of merit for high dry bulb/low wet bulb environments, such as the Middle East.
I have spent considerable time as an application engineer too, so I'm not too crazy about the pen pushing type mentioned. Although, I do know the type you are describing. These usually revolt at the first mention of thinking outside the box.
US Iceman,
Yes, if I can sum up what you have said very rightly .
The different condensing processes used are as follows
1. Conventional Evap condensers use evaporativily cooled water
2. Shell and tube/shell and coil use water cooled in a cooling Tower or Pond or use river water once thru.
3. Conventional air cooled condensers having typically 9 to 11 fins per inch use hot and dirty ambient air at the dry bulb temperature. The result is often condensers clogged by debris and system tripping on high temperature.
4. The net result is increased power use / lowered COP
5. CME s cool the high temperature ambient air, closer to ambient wet bulb temperature depending on the effectiveness of the mass exchanger .The cooling is achieved by surface evaporation .
Additional advantages of CME cooled condenser are as under.
1. Air filtered down to 5 micron or better by the process known as air washing
2. Low parasitic pumping power use due to low head requirements of surface evaporation system when compared with high pressure pumping used in nozzle based system
3. No water carry over due to “low velocity over matrix” design
4. Nearly No corrosion
Multiport Flat tube heat exchangers use different fin design and need less fins per inch as the primary surface are is considerably more compared to round tube systems without addition cost burden.. Please see the car air con condenser for reference. You will notice the difference and the fouling in automotive application is more critical.
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
winfred.dela
Hi US Iceman,
When this particular product was mentioned in this thread, i also inquired from idalex.com with the purpose of purchasing the Idalex Refrigerant Condenser. I intend to use it in my prototype unit for a marine application.
The product is not yet available. Am sharing here a portion of their email:
There are always those that wanted to use new products but it always equate to giving the 3 Ts (Time, Treasure, Talent). Very few have the luxury of giving all those 3, especially the TIME.
As an application engineer, we always know that TIME (to make a prototype and gathering the test data) is the hardest one to find.
With RE forum, we can make the TIME somewhat shorter by asking some members to share their experiences.
For this, i am thanking those that share their experiences.
Of course, as we always know: giving ideas are great but then talk is cheap. . . :).
That's why application engineers always loathe those pencil pushers. . . . :)
Regards & Thanks.
Winfredy
Dear Winfredy,
I have always done prototypes myself spending my own money.
Winfredy, We seem to have a lot in common, having run our own companies and being application engineers, to start with.
(No offence intended, if you are an application engineer, you must have met your share of the pen pushing types, I referred),
Sure, we are not inventors but as application engineers, we are innovators.
Our job is to use the applied science in an innovative way. Otherwise what way are we different than any other practicing refrigeration engineer.
We use time tested components /techniques in an innovative manner to create either a new application or a new product.
During the design process we do not invent new processes but use the existing knowledge to leverage a commercial advantage.
Because in private industry it is never people s money (it is your own or you are accountable ) so we learn to minimize losses and expenses (including our professional reputation) to our own self/ our companies.
(The practice of doing for the sake of being the first is for the scientist that use people's money in the product development or in prototypes)
I wonder where our applied science will be without fundamentals,
The research painstakingly pursued by scientists. (Many good ones were paid salaries less than our assistants, so much for people‘s money)
I think let us not undermine the contribution of science in our profession.
I seem to have touched some raw nerve to make you respond like my Grandpa.
My answers to your questions are :
-Yes , I have done prototypes always with my own money and sold all of them to intelligent customers and Believe me they do exist .
- This second comment is a bit offensive, without knowing some one‘s capability.
Incidentally, Idalex does not make this product .The do Indirect/Direct Evaporative Cooling (IDEC)systems. These are also called Dew point coolers.
Which are commercially not viable for this application at the moment?
No doubt the talk is cheap. Unfortunately, Knowledge is exchanged only by discussing and asking questions but one must have the substance for that not merely semantics.
Any way, thanks for making me work overtime without paying
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by
Darshi
- This second comment is a bit offensive, without knowing some one‘s capability.
Hi Darshi,
Sorry for the comment then, i apologized . . .
Just got a little off my regular tone, maybe because i had a not so good day.
Sincerely,
Winfred :)
Re: Compact Heat Exchangers for Ammonia
Winfred
It is fine .
Let us keep exchanging views.
We learn more from each other's mistakes.
Have a very nice day .
Re: Compact Heat Exchangers for Ammonia
Quote:
Originally Posted by Darshi
Multiport Flat tube heat exchangers use different fin design and need less fins per inch as the primary surface are is considerably more compared to round tube systems without addition cost burden.
The increase in primary surface makes sense. But, what's the surface ratio of the flat tube exchanger compared to a round tube and fin exchanger.
In the tube and fin exchanger the secondary to primary surface ratio is usually quite high. Fins make cheaper heat transfer surface than primary surface.
I could also see the flat tubes having slightly lower static pressure losses, since you would not have staggered tube banks (like in a tube & fin exchanger).