Condensor fan cfm

[SexyMF]

Ok I've had a search and not found too much regarding CFM for the condensor. It would seem that it is a matter of how large/oversized the condensor is. I'm going DD with a Kayl block, NL11F compressor.

I would like to get some of these fans. Ideally I'd like 1 on the condensor and 1 to vent the case. I'm wondering if I may need 2 on the condensor.

http://www.trademe.co.nz/Computers/Components/Cooling-fans/auction-51547022.htm

This is a condensor I'm more than likely going to use. I'm not sure about it's size.

http://i20.photobucket.com/albums/b224/Unxious/landroverevap.jpg

It's from a landrover. Part number RTC6720

Thanks

[Marvin]

I think 2 fans and a shroud would be great. But the condensor ia a bit overkilll to a dd system..

[SexyMF]

Yeah I just picked it up. It's a lot larger than I thought. I might cut it in half and replumb it.

[[XC] MarioMaster]

Have fun :D That might take a while

[SexyMF]

I'm not going to cut it. But I definitely have to reroute it. It's actually and evap so there is to much uphill going on.

[Stelios]

I dont think it will work with the NL11F as it's too big . I'm having problems with a condenser that is 17x12x15cm .

[Fhqwhgads6680]

I dont think it will work with the NL11F as it's too big . I'm having problems with a condenser that is 17x12x15cm .


What problem could you have with a condenser thats "too big"? That'd just give you more capacity and remove the need for a desuperheater (other than vibration dampening :) ) I think it'd work just fine with 2 fans and a shroud on it.

[epion2985]

What problem could you have with a condenser thats "too big"?

The size will attribute to the drop in refrigerant velocity. The up downw up design will as well, as well as cause pooling, which in turn will cause a very uneven supply of the refrigerant to the metering device. I tried an oversized condenser, does not work well.

[SexyMF]

Ok, I also picked up a proper condensor. It is about 30 x 40cm with a small depth of about 40mm. I'll use that instead. I am surprised at how small a condensor you can get away with.

However using a slimer taller condensor makes for a larger unit.

Should I then use 2 fans vertically centre or, 2 fans horizontally at the bottom?
I also have the possibility of a single large suction fan (250mm or so). But that will require more room.

[Stelios]

I agree with epion2985 . :)
The motor i used was the Danfoss NL11F with R507 .
In order to make low temps below -40C , I have to pump more and more refrigerant as the highside pressure is low . All the time the condenser is cold , except the first "U" .
When i turn the motor off , the pressure rises up to 11-12 bars and after 10 hours it settles at 8-9 bars . That's a static pressure of 8+ bars and the NL11F is UNABLE to start with that pressure . I don't know if the problem comes from the liquid in the condenser .:confused:
Other thing i noticed is that when i turn off the unit , the condenser starts to cold ... below room temp . Do you call this "pooling" ???

And that's with a condenser with dimensions : 17x22x15cm . It has 15 "U" . 3 colums with 5 "U" each one . The refrigerant goes down , then up , and finally down and exits from the condenser .

[Xeon th MG Pony]

you guys just don't grasp the concept of volociety in a closed system do you!

NO it WILL NOT effect gass volosity, short of puting it in a tank it will get at an equal rate to all other gasses in the system, it has too, other wise it would be called a plug or restriction (And pressures will rise, the same in water cooling)


You will need to plumb it to work as a condencer, yes pooling will be a real issue as with correct system charge, as for the compressor the system should equilize after X amount of time allowing no load starts

[SexyMF]

Harsh Xeon.

I'm not going to cut it. But I definitely have to reroute it. It's actually and evap so there is to much uphill going on.

^^^^^ "reroute it" I said.

[Xeon th MG Pony]

on the volociety point yes, I get driven up the wall about it due to the watercooling crowed geting all neurotic about it, no patients left. in a closed system volocity is all ways equal no mater what when dealing with liquids, in gass systems it is the same unless a diameter change occures then it is slowed due to the higher volume but once expanded volocity pics up rapidly as new fluid flashes to gass so we can safely ignor it unless they intend on running several feet of 1 1/2inch tubing! then volocity will become an issue (Again this only concerns oil return not how the refrigerant functions), then again if you have a high mass flow of refrigerant then the plumbing isn't even an Issue as all large scale systems use up/down 3 or more row condencers often of 3/8s tubing! all the systems I have ever dealt with use 1/4 liquid line with only flares and 3/8 to 1/2 inch return lines, again all flared and unless it's doing a larg verticle rise we ignore gass volocity for any thing other then accustice noise! I'll try and dig up a nifty chart/PDF for you

On the bottom point it was blunt, sory if it sounded harsh, I am usualy very direct with things and oft don't sugar coat it as it where..

[Xeon th MG Pony]

crap I deleated it, I'll try and find it again, but needless to say gass valocity never became an issue till you started hiting the 1-1/2inch and higher sized tubing, for the small common systems I'd worry more about accidently breaking it by handiling then gass velocity!

[yngndrw]

in a closed system volocity is all ways equal no mater what when dealing with liquids,

So you're saying that if you have a 1" bore tube with x water flow, which you then reduce to 1/2" .. The water velocity will be the same through both diameters of pipe ?

I think not. The same volume of water is flowing through both pipes., however to get the same volume through the 1/2" bore pipe it must be traveling at a higher velocity than through the 1" bore pipe. :stick:

[epion2985]

Velocity is a speed in a direction, meaning if there is no change in velocity then the speed of the gas nor the direction of the flow change, which it does. Also I never said it wont equilize. In my system the condenser piping is bigger then the piping before and after, so the magnitude of velocity does drop across the coil but picks up later. The problem is where it dropps, in the coil, then you get pooling in it. And the up down up down design where you have to drive the refrigerant up all the time doesnt help. That was my expirience with an oversized coil of simmilar design.

[Xeon th MG Pony]

Ok now you elaberated thanks, that makes more sense.

@yngndrw I know, I wanted to keep it relitivly simple, thats why I said unless they intended to use overtly larg pipes, the diamiter change we are enforcing is realitivly small delta there for a small impact over all, I could bore you out of your skull amd map out all the volocity changes down to the laminar flows, but what will this achive to a use full end? Nicht! so some simplification is indeed called for no? This way we do not burden the licener with un-needed info, we must use simplification care fully as to not confuse the licener but all so not to leave him with a lacking in the needed info!

See what I mean?

[Xeon th MG Pony]

Yes in a larger coil we trade gass speed for current, but with suficient charge there is enough liquid to flush it through with out issue & due to this quoting just velocity is incorrect. But you'd be suprissed how fast that gase realy is moving inside that pipe! so unless he was (Again) using very larg diameter pipe it is a non issue, he just has to use more gass. I will admit, such small systems are not my strength.

[epion2985]

Yes in a larger coil we trade gass speed for current, but with suficient charge there is enough liquid to flush it through with out issue

When the system would be turned off would the pressure rise to where the compressor may not be capable of starting up? Doesnt it make more sence to just size the condensing coil properly rather then deal with excessive pressures?

[Xeon th MG Pony]

pressur would rais but it would be equall across the system, the loop could be 1trillion PSI but as fare as the compressor sees it, it's still 0psi and starts with no load you have to remember this is a closed system, unless you are activly restraining the pressur with a velve (As in my design) the compressor will all ways see no starting load unless short cycling, and if your short cycling load pressure is thee least of your worries!

[SexyMF]

As far as I'm aware Xeon, you are book smart but haven't built anything. I trust experience. Your control method for your chiller is going to destory the compressor by starting it under max load every cycle.

Please keep to the topic here. About fan placement and CFM. Especailly since I'm not going to have pooling as an issue since I'm replumbing for all downhill, and without any pipe size changes.

[Xeon th MG Pony]

I haven't built any thing? LOL nice Assumption but very very wrong I am afraid. I do not know where you got that idea.

I only trust first hand experiance too. That controll methode is widely used, in fact it is mandatory for semihermetic systems! but works just fine on hermetic ones as well

As for the main toppic that IS what is being discused, I see no majour issue with the unit other then a possible pooling issue with out enough mass flow, but that can be corrected by using a larger charge of refridgerant and doing some slight replumbing...

[epion2985]

pressur would rais but it would be equall across the system, the loop could be 1trillion PSI but as fare as the compressor sees it, it's still 0psi and starts with no load you have to remember this is a closed system, unless you are activly restraining the pressur with a velve (As in my design) the compressor will all ways see no starting load unless short cycling, and if your short cycling load pressure is thee least of your worries!

you are right, thanks.

[SexyMF]

I haven't built any thing? LOL nice Assumption but very very wrong I am afraid. I do not know where you got that idea.

A search of all threads started by you and your joining date. I can only talk about your contribution to these forums.

If you are a veteran then join up for the Autocascade competition (if you already have not).

[SexyMF]

and CFM hasn't been mentioned in any of your responses.

[epion2985]

Well he is not talking about CFM because I stated that the condenser is to big and CFM is not his problem right now. First he needs to size things properly. All things given and said I am sure Xeon as a seasoned hvac engineer knows all too well that sizing components correctly for the system is very important to preformance, and energy and or cost efficiency.

[Xeon th MG Pony]

well not hvac spacificly, but fluid systems in general, and yes properly sized units are ideal, but in the hobbiest world one must make stufe work that is less then ideal, if he can do it then yes, this is the beter plan, if not he can "make" it work satifacteraly.

[epion2985]

I guess it depends on how well you want things to work and your definition of "well" :)

[Xeon th MG Pony]

for my self I want it perfect, but I some times lower my standerds to make it work with what I have on hand, personaly I find thoughs systems fare more impressive then the engineered ones as they are closer to art then a run-of-the-mill type boxed system. there is no chalang in using all the "right" parts :)

Half the fun and chalange is making all non standerd parts work togeather IMO.

[epion2985]

:toast: toast to fellow perfectionist

[Xeon th MG Pony]

:toast:

[SexyMF]

I'm going to use this one. Still debating about 1 or two fans though.
Maybe one in the middle?

http://i20.photobucket.com/albums/b224/Unxious/Direct%20Die/Condensor36x40Medium.jpg

[epion2985]

Thats perfect. If you have room for it two thumbs up. And on your fan question, unlese you have a fan to cover all that make a shroud, you wont regret it.

[Xeon th MG Pony]

Exxxxcelent *Rubs hands togeather* [\r.Burns mode off]

That is much beter mate :)

[SexyMF]

I've cleaned this scrap metal up. It will become my shroud.

http://i20.photobucket.com/albums/b224/Unxious/Direct%20Die/MetalforshroudMedium.jpg

[[XC] MarioMaster]

Or you could make a shroud like i did.....ghetto cardboard shouds FTW :)

[SexyMF]

I've gone back on my word and have cut that original evaporator in 2. Have pulled it apart and will make a smaller compact unit. A little bigger than a 120mm fan. That should be fine judging on what others use.

[epion2985]

pictures please :)