SC21 in LeChuck Case

Hi!

Over the last time I tried to pack as much condensing power as possible into a 60cm LeChuck case. I ended up with two Cold_Ice deluxe condensors, each one in push-pull configurations with two Delta Fans. As I tried with a SC12, it soon became clear that it could handle much more power, so I switched to a SC21G that was lurking on the shelf for the last months...

If it pays off against a good designed NL11 singlestage may be open for discussion, the unit now makes -38.2°c AT 275W load at 25°C ambient temperature. At least more than enough for a quad core...

Components:

SC21G compressor
2x Cold_Ice Deluxe condensors
4x Delta fans
LeChuck 60cm Case with specially designed front and rear
230cm 0,9er captube
R507
oven-brazed Cold_Ice evaporator

PS: The first one complaining about the run/start cap mounting will be put on ignor ;) In this tight space the mounting proofed solid, the starting relais is screwed to the bottom of the case and the cable ties hold perfect...

PPS: No, it is NOT silent...

Regards,

Philipp

http://www.abload.de/img/sc210043b3.jpg
http://www.abload.de/img/sc21005cpt.jpg
http://www.abload.de/img/sc210097d4.jpg
http://www.abload.de/img/sc210102o5.jpg
http://www.abload.de/img/sc21012gqh.jpg
http://www.abload.de/img/sc21013gjt.jpg

Very professional job. Well done Phillip. German quality!

Ps.Thank god another one that is not spending useless his time in polishing the filter and pipes :rolleyes:

I prefer soldering with Harris Dynaflow. It makes the joints to look dark, but it has two advantages: If the joint looks tight, it is, and there is no flux needed that could compromise the inside and get into the refrigerant. Therefore the joints dont look as nice as with silver solder. I Remove copper oxide with a grinding sponge after cooling, but I dont polish the joints...

Regards,

Philipp

You couldn't double up the condensers? The back condenser will get all the heat dump from the compressor and not help much. It looks beautiful though!

maybe u wanna change de design of the flow inside the case:
enters at front and rear end, and comes out at the midle on the sides;)
no minimal spiral to dump the vibration frrom compresor?

succes,
q

i think in regards to his temps and wattage there is no point in suggesting he change anything...

Very nice, I would have most likely avoided the heat dump that way, however still beautiful work. Maybe consider doing dual condenser at the front on the sides of the case, to get fresh air on both. Or pull fresh air along the compressor as well to avoid that heat dump.
Either way, beautiful, and very good looking work, the performance is definitly there as well. Question for you however, hows it do for floodback considering what seems to be a straight suction.

check a p/t chart! how much is the presure for r507 at a temperature like 50C or more? yeap, the heat dumped by the compresor back to the first condenser from the loop! 50 or more... with your airflow maybe 60? and because the back presure is so high temp of compresor is going higher.

Quote:

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Originally Posted by n00b 0f l337

Very nice, I would have most likely avoided the heat dump that way, however still beautiful work. Maybe consider doing dual condenser at the front on the sides of the case, to get fresh air on both. Or pull fresh air along the compressor as well to avoid that heat dump.

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Hmmm. Interesting... I didnt think of it that way. My theory was that if I put the condensors both in front of the compressor, the compressor gets even hotter air and also gets hotter.
My thought of this setup was that the rear condensor (the first one to pass for the refrigerant) acts as a desuperheater and the real condensing happens in the second condensor (in the front).

Quote:

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Originally Posted by n00b 0f l337

Question for you however, hows it do for floodback considering what seems to be a straight suction.

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The suction line makes a loop in the top of the case, length is around 80cm inside the case (12mm diameter). I tested a long time idle and I can hear a little splash sometimes but nothing to worry about.

Quote:

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Originally Posted by quintus

check a p/t chart! how much is the presure for r507 at a temperature like 50C or more? yeap, the heat dumped by the compresor back to the first condenser from the loop! 50 or more... with your airflow maybe 60? and because the back presure is so high temp of compresor is going higher.

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I am sorry, but I cant follow you at all...
All in all, I have about 3K superheat and max. 1.5K subcooling at max. load. Dont know how to improve that anymore...

Quote:

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Originally Posted by quintus

no minimal spiral to dump the vibration frrom compresor?

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The HP line from the comp outlet to the condensor inlet makes a 90 degree bend and both parts (before and after the bend) are long enough to give enough space for vibrations I think.


Regards,

Philipp

About fan orientation/configuration :

In every case you will have a hot part, the desuperheater or the compressor and finally the heat exchanged (condenser + desup + compressor) will be ~ the same.

And he won't condense @ 50+°C because air inside the case is @50°C, that's non sense, you can't see anything on the P/T chart if you don't have the condenser's capacity. Assuming the configuration (one condenser behind the other) the total condenser's capacity must be >700w as both condensers are 500w rated (15K CTD). It would be ~1kW if he could have set both of them side-by-side, it's not the case here.

@ 275w cooling capacity and -40°C evaporating temperature, you've got less than 700w to reject, so the condensing temperature won't be over ambiant + 15K

Its more like 8K over ambient.

simple as that: i had the same fan and condensers configuration, same concept, and i had 24bar presure after desuperheater and before 1st condenser because of hot air from compresor. if u wanna work with 24bar or more head presure...

The pressure should be more or less the same throughout all of the HP tubing. Its all 6mm tubing.

In my humble opinion, what happens, is the following: The hot superheated gas from the compressor gets out with about 95°C, then its cooled down on its way through the first condensor. As soon as the hot gas reaches about 33°C it stays at this temperature and gets condensed along the way though the rest of the first and most part of the second condensor. As soon as everything is condensed, on the last part of the second condensor, it gets subcooled by around 1.5K. As this is not very much, there should be not much of the second condensor be involved in subcooling. Ans since in the first condensor the tubings after two or three loops can be touched easily, I think there is not much of the first condensor involved in desuperheating. So I think most of the condensors surface should do what it should do: condensing...

Regards,

Philipp

Condensing and subcooling. Did you measure the discharge pressure to know about this exactly?

@quintus: Compressor or desuperheater doesn't make much difference : in the end all the heat will be removed (compressor + desuperheater + condenser), wherever the heat is located, it must be rejected and finally air will have same temperature. More over, the heat rejected through the shell is way lower than the heat rejected in the desupperheater (assuming 40°C gas temp in the outlet, it is even more in the reallity as you can easily get ~30°C at the outlet as PhilippF said). If you got 24 bar discharge pressure, then all the discharge part (condenser + desupperheater) is underestimated, it's not because air needs to pass the compressor first that it will lead to such a high discharge pressure. And btw : the pressure is the same in the entire discharge line (excluding tiny pressure drop), unless it is changing phase, you can't match the pessure and the temperature.

Heat rejected from compressor is dumped in the first condenser, that one at the back.

That condenser it useless!!!

This is after 20minutes when the compressor it's going to normal runing temperature. The heat rejected through the shell is as high as 70%! Sooo air enters at the front, it's taking heat from second condenser, ''washes'' off the compressor, so it has something like 50c and goes to the first condenser at the back to take heat from this one. How can it do that when it has 50 or more degrees???

How much time have you let the unit run? Let it run for 2 or 3 hours take the side off and touch if u can the condensor at the back! it will have 60C or more on all surface!!!

Have you seen big units like 10KW or soo, or bigger? The usual and normal design is: air gets pulled thru condenser and blasts the compresor. There is never hot air from compresor pushed thru condenser, never ,never, never!!!

Everything looks good! and compresor is doomed to have a short life!

Quote:

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Originally Posted by quintus

Heat rejected from compressor is dumped in the first condenser, that one at the back.

That condenser it useless!!!

This is after 20minutes when the compressor it's going to normal runing temperature. The heat rejected through the shell is as high as 70%! Sooo air enters at the front, it's taking heat from second condenser, ''washes'' off the compressor, so it has something like 50c and goes to the first condenser at the back to take heat from this one. How can it do that when it has 50 or more degrees???

How much time have you let the unit run? Let it run for 2 or 3 hours take the side off and touch if u can the condensor at the back! it will have 60C or more on all surface!!!

Have you seen big units like 10KW or soo, or bigger? The usual and normal design is: air gets pulled thru condenser and blasts the compresor. There is never hot air from compresor pushed thru condenser, never ,never, never!!!

Everything looks good! and compresor is doomed to have a short life!

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DOOMED! :explode:

At least he tried something new.

Dear quintus,

actually this unit has run for about two hours under foll load. I strongly disagree that the compressor in it will have a short life. The ressure stays under 16 barg, the compressor shell stays under 80°C and discharge temperature stays under 100°C. So all criterias run well inside the specified parameters given from Danfoss.

I agree that perhaps the condensor performance could have been improve a little by making the air move through the two condensors first and then pass the compressor, but hey: It condenses about 8K over ambient! That way it is still very much oversized!
If (like you say), the heat from the compressor is removed 70% over the shell, my first thought might have been correct to place the compressor not in the total hot air stream but in the "middle" hot...

But to stray all doubts, I will measure exhaust temperature tomorrow after a two hour run under full load....


Regards,

Philipp

80c is still pretty hot for a reciprocating compressor, it would be more normal if it were a rotary

Have you ever touched the compressor of your fridge?

Depends on your discharge pressure as well, it is a R134a compressor is it not?

Quote:

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Originally Posted by OVERDRIVER

Hi all i dont quite understand here in order to see what is for sale here you have to post like 500 times ?
what difference do that make or are you not allowed to ask questions?

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please stop trolling

It is. That is why I have to stay below 16 barg HP...

EDIT: And when I draw a R134a cycle compressing from 0.2 barg to 16 barg with a isentropic efficiency of 0.6, the discharge temp is about 105 °C...

Have pitty for the compressor and change the air flow to: in from the front and back and exits at the sides. This way the compresor will have a long and happy life:)

Trust me i did this 2 years ago;)

You have only 230 cm of 0.9mm captube ? such short ? :eek:

Quote:

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Originally Posted by quintus

Have pitty for the compressor and change the air flow to: in from the front and back and exits at the sides. This way the compresor will have a long and happy life:)

Trust me i did this 2 years ago;)

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omfg. you wrote so much bull:banana::banana::banana::banana: in this thread...
Do you guys think that his fans are off? Or running at 3V? Man... he has a massiv airflow in this case.

Doesn't look like that much, one input one output, so not that much, there only 25mm thick fans as well it would seem. Unless there like 160cfm, and even then that's not a whole lot.

These are Delta AFB1212SH, 0.80 Ampere, 113 cfm, altogether 4 of them. I even had to use two power supplies as one delivers only 2.1 amps. In push-pull-configuration on each condensor they make a lot of wind...

Quote:

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Originally Posted by piotres

You have only 230 cm of 0.9mm captube ? such short ? :eek:

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Yep, I started with 330 cm and started cutting off 20cm each time. Goal was to have less than 2K of subcooling at 275W. I did not use a SLHX with which the cap tube would have to be much longer.

Regards,

Philipp

Quote:

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Originally Posted by PhilippF

It is. That is why I have to stay below 16 barg HP...

EDIT: And when I draw a R134a cycle compressing from 0.2 barg to 16 barg with a isentropic efficiency of 0.6, the discharge temp is about 105 °C...

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What is the suction temperature in this cycle? Without Qloss I have 205°C @ 0°C suction temperature, and 133°C @ 0K superheat (-5x°C suction temperature).

A recip can run with high discharge temp, the isentropic efficiency of SC serie is near from 0.45 so running with 100+ discharge temp won't lead to death ;)

Suction temp should be about 5K above evaporation temperature. There is not much heat transfer along the suction line as I didnt use a SLHX.

What is really interesting: Where did you get the info about the isentropic efficiency of the compressor? I didnt find it anywhere and from my previous experiments, I guessed around 0.6 ?

Regards,

Philipp

Danfoss data, they give you the operating conditions so you can set them in coolpack and find it. But its extrapolation here since you're not using the proper refrigerant with the compressors but in both cases (SC21G, SC21CLX) it is about 0.45 at low pressures.