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MrReds
09-09-2011, 10:02 PM
Hello,
I have red a lot of posts, increasing my knowledge of NH3 systems.
Nonetheless, I am dealing with the dimensioning of a NH3 flooded evaporator.
I have two design evaporating temperatures:
The first one is @ 18 F, with air @ 33F
While the second one is @ -13 F with air @ 33F
I am utilizing a software that provides me the pressure drop.
I was wondering if someone could suggest me which is the most suitable pressure drop value I have to dimension the evaporator or some literature to refer to concerning this topic.

Thanks in advance !

josei
10-09-2011, 11:49 PM
Hello Reds , your options are:



ta-tr = 33-18= 15°F is good Dt if room relative humidity is low.
ta-tr =33-(-13)°F = 46°F too high DT. Donīt use it , any way.
ta-tr =8°F maximun if your roomīs r.h. is high; so then tr must be 25°F o high

If 3 is your case , it will need suction regulator.
Pressure drop. It depend of your sistem, isnīt your choice. Do you have duct conected to evaporator ? (PD must be estimated) or it has free discharge of air? (then PD is zero)

MrReds
18-09-2011, 11:16 AM
Hello Mr Josei,
many thanks for your answer. and apologizes if I have not been clear enough.
The pressure drop I was referring to was NH3 pressure drop, not air pressure drop !
In shorts, is there an advisable pressure drop ? Is there an advisable kW per circuit ?

Thanks !

Magoo
19-09-2011, 04:14 AM
Hi MrReds.
you are attacking the problem from the wrong end. First establish the coil duty. and amount of steel required. Then work out the length of each circuit per pass. By dual passing halves the loss, treble pass apply similarly.

josei
19-09-2011, 02:43 PM
Hi MrReds:
My figures given in response, were consulted from manufacturer catalogs. Usually the flow capacities for flooded and recirculated flow evaporators has low refrigerant pressure drop compared with the head of ammonia pump or column of NH3 in the case of flooded.
7830

Magoo
20-09-2011, 01:34 AM
Hello Josei.
can you explain the ESP.

MrReds
21-09-2011, 06:29 AM
Many thanks Mr. Magoo and Mr. Josei.

Mr Magoo
Many thanks
Indeed the capacity is determined. The question I have got is: now which is the correct number of feedings for the evaporator ? which is the max pressure drop I can afford for every refrigerant circuit ?
Please, do you know if exists some tables or some references to know:
- which is the capacity to assign to each circuit (typically total capacity/number of circuits) ?
- which is the length of each circuit ?

Mr Josei
Please, could you post more pieces of information concerning your last post ?
Indeed I would be interested in these figures: how to determine the correct number of passes in an evaporator given working conditions and capacity determined.

Indeed these figures is what I am looking for.

Thanks for your help.

MrReds
29-09-2011, 11:05 PM
Hello, please, can anybody help me or are my questions too strange ?

many thanks

josei
30-09-2011, 05:22 PM
Hello, please, can anybody help me or are my questions too strange ?

many thanks
What u are looking for is design to produce a flooded evaporator with NH3, right?.
Well, I'm in accordance with you, here this is a strange subject, because RE primarily deals with themes for application, operation, maintenance and repair of equip and sys. if u are lucky, could find a technician or engineer who has produced evaporation equipment and is willing to design for free. That's it, I think.:confused:

MrReds
01-10-2011, 03:35 PM
Mr Josei,
I apologize if you think I have misunderstood the forum contents.
Nonetheless, in other sections, as fundamentals, I have found several request similar to mine.
Moreover, I think that the forum is a place where pieces of information can be exchanged.
If there is some specific literature, I am not asking it for free, but a literature reference would be useful to help me in my task.
Since it was a specific question relative to NH3, I thought to post it in NH3 section.

that's all.

Josip
01-10-2011, 06:43 PM
Hi, dear MrReds :)


Hello,
I have red a lot of posts, increasing my knowledge of NH3 systems.
Nonetheless, I am dealing with the dimensioning of a NH3 flooded evaporator.
I have two design evaporating temperatures:
The first one is @ 18 F, with air @ 33F
While the second one is @ -13 F with air @ 33F
I am utilizing a software that provides me the pressure drop.
I was wondering if someone could suggest me which is the most suitable pressure drop value I have to dimension the evaporator or some literature to refer to concerning this topic.

Thanks in advance !


Your question is not easy to answer, I know that because as a young engineer I was working in construction department constructing HE, liquid separators, evaporative condensers, receivers, etc .... Each manufacturer has own secrets regarding construction of heat exchangers and other equipment ... you just need to calculate required capacity and application ... then manufacturer will offer you HE with needed capacity, furthermore with possibility to choose: wall or ceiling mounting, one or two air inlet and one or two air outlet, with electrical or hot gas defrosting system, top or bottom feeding, etc .... then we can have forced or gravity circulation of air through the evaporator depending on room application ... to install one ore more HE is also one of questions depending on the room size .... of course if your evaporator is custom made you need to provide all requested data regarding installation ...

I'm trying to help you with some specific literature as you requested ...

Here is the link to Wolverine tube exchanger data book II ...
http://www.wlv.com/products/databook/databook.pdf

and here is Wolverine engineering data book III
http://www.wlv.com/products/databook/db3/DataBookIII.pdf

and some other links
http://www.wlv.com/products/databook/ch1_2.pdf
http://www.wlv.com/products/databook/ch2_5.pd
http://www.wlv.com/products/databook/db3/data/db3ch6.pdf

here you can find a lot of knowledge....
http://www.swep.net/index.php?tpl=page0&lang=en&id=113

Handbooks, Refrigerant applications, Heating applications, Industrial applications ... all free to download....

Hope this will be of some help to you.

Best regards, Josip :)