2 Compressors In A Single Stage?

Hi, I was wondering what would happen if someone were to put to compressors in serial in a single stage unit? As in the discharge port from the first connects to the suction port of the second one. Anyone understand or should I draw a diagram?

Thanks

That'd be series, but I'd imagine you'd burn the compressor in front out with the hot discharge from the one doing most of the compressing, and you'd manage a lower low side pressure.

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Originally Posted by n00b 0f l337

That'd be series, but I'd imagine you'd burn the compressor in front out with the hot discharge from the one doing most of the compressing, and you'd manage a lower low side pressure.

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Woops, your right it is serial, i'll go edit my post. So pretty much it wouldn't work.

I'd think you'd have to desuperheat/cool the discharge. And then you'd risk sending liquid refrigerant at your other compressor.
But two stage compression does exist, so it has to work in some way, unless the systems are rated for dealing with that sort of work load.
If you want to play with two, try two in parallel. ;)

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Originally Posted by n00b 0f l337

I'd think you'd have to desuperheat/cool the discharge. And then you'd risk sending liquid refrigerant at your other compressor.
But two stage compression does exist, so it has to work in some way, unless the systems are rated for dealing with that sort of work load.
If you want to play with two, try two in parallel. ;)

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I see :up:

Sorry for a silly question, but how would I put them in parallel, instead of serial?

EDIT:

Like this?

http://i292.photobucket.com/albums/m...y1992/SS-1.jpg

danfoss make comps like this :) in condecing units
http://www.extremecooling.net/random.../danfoss/2.jpg

Thats a whole lot of cooling power you got there Carl.

Hey fatguy, that parallel Diagram looks pretty much right. You might wanna put a DSH after each comp though. Or have an enormous condensor

How do you ensure proper oil return though?

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Originally Posted by Postal Dude

Thats a whole lot of cooling power you got there Carl.

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:) there not mine it was just for illustration could not find the pic on danfoss's web so used this pic from cold_ice's thread

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Originally Posted by sjg0

How do you ensure proper oil return though?

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there will be no need to on such a small system

Looks like you could have a nice lil project there fatguy. Good luck with it. You using recip or rotary compressors?
What gas you looking to use with it?

First i'll build a normal SS with my 1 & 3/8hp compressor, then i'll try making the dual compressor unit, with another compressor from a small AC unit off ebay. Not sure on what gas to use, would have to use anything special, or just R507? Also whats a DSH?

Then if it goes all good, I might try a cascade one day.

Anyway I can't do much till I finish school this year, then i'll have heaps of time and money :D

Thanks

Still dont get the point...if your going to use 2 compressors just build a cascade and maximize your temps.

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Originally Posted by sdumper

Still dont get the point...if your going to use 2 compressors just build a cascade and maximize your temps.

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its good if you got 2 matching small comps like 6-8 cc then you can do more with them but if you got a comp bigger than 11cc like you say theres not much point:)

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Originally Posted by sdumper

Still dont get the point...if your going to use 2 compressors just build a cascade and maximize your temps.

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The only I reason I would is just for practice and for fun :)

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Originally Posted by fatguy1992

The only I reason I would is just for practice and for fun :)

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Thats cool..Id enjoy following your log on that because things have gotten pretty slow around here lately and I am too broke to start any new projects so have to live vicariously :(

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Originally Posted by sdumper

Thats cool..Id enjoy following your log on that because things have gotten pretty slow around here lately and I am too broke to start any new projects so have to live vicariously :(

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Thanks

Unfortunately I won't start any builds until October, no time or money till then :(

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Originally Posted by sjg0

How do you ensure proper oil return though?

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You could connect the service ports, if one has a little bit higher oil level for whatever reason it'll flow through the tube there, unless for whatever reason there is a pressure difference between the compressors suction sides...

If you put compressors in paralel is there any change of final temps?
If not then like sdumper said a cascade would be a better choise.

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Originally Posted by The Shooter

If you put compressors in paralel is there any change of final temps?

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It would increase capacity, allow you to have a real high load, maybe good for a 1st stage of a cascade, but you can't really push the load limits of a single compressor in a single stage, the max heat output of a CPU is what, around 200 watts or so?

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Originally Posted by [486]

It would increase capacity, allow you to have a real high load, maybe good for a 1st stage of a cascade, but you can't really push the load limits of a single compressor in a single stage, the max heat output of a CPU is what, around 200 watts or so?

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Thats @ low GHz and volts. i7's easy produce 350watts+.

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Originally Posted by fatguy1992

Thats @ low GHz and volts. i7's easy produce 350watts+.

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:shocked: That is almost 30 amps, now I see why they use an 8 pin connector! I actually think that is more wattage than my entire computer uses!
I really have been out of the computer "loop" for a while...

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Originally Posted by [486]

You could connect the service ports, if one has a little bit higher oil level for whatever reason it'll flow through the tube there, unless for whatever reason there is a pressure difference between the compressors suction sides...

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Hmm... I hadn't thought of that.

It still doesn't help though, because I think this thread is referring to the small, 7cc Rechies listed on ebay. Rotaries don't have service ports :(

With reciprocating compressors you simply drill a hole in the bottom of the case and link the two compressors with 1/4" tubing. The oil levels will equalize during operation. With rotary compressors I guess you can do the same thing.

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Originally Posted by [XC] gomeler

With reciprocating compressors you simply drill a hole in the bottom of the case and link the two compressors with 1/4" tubing. The oil levels will equalize during operation. With rotary compressors I guess you can do the same thing.

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But what happens if you have a slight difference in the suction lines or something that would cause higher pressure in the other, like a bit of brazing material at one side of the T fitting connecting the 2? If the tube was at the bottom then a lot more oil could transfer than using the service ports.

I'd assume the whole thing wouldn't matter much as the oil in the systems moves through the tubes and all, if one compressor had a little more oil it would just pull more into it's intake and put it through the system, no harm done. Besides, the valves on the recip. compressors are reed valves, so they can handle a little oil, just a cylinder full of it will wreck the con rod... I think this might be the principle that the condensing units that have 2 compressors in parallel work on...

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Originally Posted by n00b 0f l337

I'd think you'd have to desuperheat/cool the discharge. And then you'd risk sending liquid refrigerant at your other compressor.
But two stage compression does exist, so it has to work in some way, unless the systems are rated for dealing with that sort of work load.
If you want to play with two, try two in parallel. ;)

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Here is a picture of a 2-stage ammonia plant at the Technical College of Jutland (Denmark).

http://img20.imageshack.us/img20/5026/2stageammonia.jpg