Autocascade Drawings

Unknown, at first it was only a few c below room temp.

I had a chat with luke on MSN and it seems i was undercharged on the propane. I have now managed to get around 0c on the pipe exiting the hx going to the captube of the evap but still i see propane temps on the evap (around -35c) at 10psi or so lowside.

It seems the r23 is not condensing, and there is not proper seperation happening but at 0c it should be condensed shouldnt it?

What I do see, is frost all the way back to the rotary coming from the evap side. but nothing from the hx side.

Im thinking maybe the captube on the hx is too long or maybe too little R23 in the loop

Well all in all, it is getting better for sure, its not easy this.

At the moment both captubes is around 2.5m

what happens now it that when the HX cools down a bit the propane in the condensor sees no reason to condens in the condensor because it has found a colder place to condens. physics law: everything wants to go to it's lowest energy state .

to prevent this you need the r23, the r23 will "block" the HX entrance for the propane (it needs to fill the HX and large part of the phase sep) and raise the high side pressure making it easier for the propane to condens.

after adding some propane up to a few bar (3 or 4 or something)
try to get a high side pressure of around 10-15 bar with the r23. Then add propane again untill your HX gets cold. The r23 will start to condens so you need to add more r23 untill your evap is getting below propane temps. More r23 is more load on the HX so maybe you need to add some propane again. Keep doing this untill it works or untill you go crazy if it doesn't work :D

Excellent, thanks!

What would you say is a expected highside pressure with no load and say 200w load?

depends on your condensor offcourse but I would expect something like, 12-13bar without load and 15-17bar with.

Quote:

---

Originally Posted by Unknown_road

after adding some propane up to a few bar (3 or 4 or something)
try to get a high side pressure of around 10-15 bar with the r23. Then add propane again untill your HX gets cold. The r23 will start to condens so you need to add more r23 untill your evap is getting below propane temps. More r23 is more load on the HX so maybe you need to add some propane again. Keep doing this untill it works or untill you go crazy if it doesn't work :D

---

Exacly, that same I told Johann :toast:

Quote:

---

Originally Posted by Unknown_road

what happens now it that when the HX cools down a bit the propane in the condensor sees no reason to condens in the condensor because it has found a colder place to condens. physics law: everything wants to go to it's lowest energy state .

to prevent this you need the r23, the r23 will "block" the HX entrance for the propane (it needs to fill the HX and large part of the phase sep) and raise the high side pressure making it easier for the propane to condens.

after adding some propane up to a few bar (3 or 4 or something)
try to get a high side pressure of around 10-15 bar with the r23. Then add propane again untill your HX gets cold. The r23 will start to condens so you need to add more r23 untill your evap is getting below propane temps. More r23 is more load on the HX so maybe you need to add some propane again. Keep doing this untill it works or untill you go crazy if it doesn't work :D

---

thats excactly how i think i should tune my auto-c, it must be a nightmare tunning if you add another stage with r14/argon!

Quote:

---

Originally Posted by esdee

thats excactly how i think i should tune my auto-c, it must be a nightmare tunning if you add another stage with r14/argon!

---

another stage with argon/R14 won`t work, you must have first something that boils at ~ -100*c, in that case ethylene, which is :banana::banana::banana::banana:ing hard to tune ;/

geuss I'm not the only one having difficulties with ethylene in my autocascade.

R23 should be good to condense r14.

Quote:

---

Originally Posted by n00b 0f l337

R23 should be good to condense r14.

---

Don`t think so NoL, under load R23 will boil at -60*C, maybe less, it`s not enough for R14. To have "normal" discharge with R14 Hx temp should be around -75*C under load...

Quote:

---

Originally Posted by Unknown_road

geuss I'm not the only one having difficulties with ethylene in my autocascade.

---

Eh...I don`t like ethylene, in autocascades...I got -85*C idle, then changed captubes to little bit longer and now "only" -75*C...god...really don`t know what I should do to get good results.:stick:

same here ;) I also reached something like -85*C idle but it was pretty unstable

I even tried condensing pressure regulators but nothing

Commercially r508a/b is used to condense r14/argon,
Or r13, is used to condense r14.

Quote:

---

Originally Posted by n00b 0f l337

Commercially r508a/b is used to condense r14/argon,
Or r13, is used to condense r14.

---

for us ethane would be a great choice!unless there is something with it that we don't know (except that its flamable)

Its very light like ethylene and has a low latent heat of vaporization sadly.
It should be a very good gas, but r508a or r23 (r23 for those who realize its half the price, just eco damaging if you people vent) should be a bit better. The big problem is to obtain temperatures neer a two stage cascade, we need r14, which is pricey as all hell and very eco damaging I"d imagine (CF4)

Quote:

---

Originally Posted by n00b 0f l337

Its very light like ethylene and has a low latent heat of vaporization sadly.
It should be a very good gas, but r508a or r23 (r23 for those who realize its half the price, just eco damaging if you people vent) should be a bit better. The big problem is to obtain temperatures neer a two stage cascade, we need r14, which is pricey as all hell and very eco damaging I"d imagine (CF4)

---

r508 is pricy as hell to, but its a great gas...

I got quoted at $78 a pound, 10 pound minimum, and $150 bottle rental that you get back later. R23 at $44 a pound, 20 pound minimum and the $150. The way I see it is I'll get r23 and have twice as much, plus the resell value on these gases at return is actually on the rise.

Quote:

---

Originally Posted by n00b 0f l337

I got quoted at $78 a pound, 10 pound minimum, and $150 bottle rental that you get back later. R23 at $44 a pound, 20 pound minimum and the $150. The way I see it is I'll get r23 and have twice as much, plus the resell value on these gases at return is actually on the rise.

---

r508b it's about the same price here, ill try to get prices on both r508 and r23
i have a huge project comming up...

damn it, gasses are more expensive than the materials of the systems.
it's like DSLR cameras, you buy the body for 600euro and then you need 1k for a good lens!

(unluckily i have both hobbies...:slapass: )

Hahahah sounds about right SD, (new name for you :P)
Luckily for me I settled for a D50 with telephoto.

Unknown_road, what gases are you using in your Auto-c ?

I`m trying with R290/R600/CO2/R1150, but in next few days Johann should send to me some R23, maybe it will help. I think that CO2 isn`t the best gas for autocascades, is it ? :p

Quote:

---

Originally Posted by n00b 0f l337

Hahahah sounds about right SD, (new name for you :P)
Luckily for me I settled for a D50 with telephoto.

---

my nick actually comes from SD :D
D50 for me too, nikon 18-200mm VR, and soon 105mm macro :D

but i need gasses too :mad:

At last I am seeing some decent progress, autocascading is happening for sure, not great but at least I know its working.

I made the Propane captube a little shorter to get more flow down there and played with charge. At the moment still not great but evap is around -65c on 5psi low, high is too high, around 15bar and the hx-out temp is around -15c

Im getting a little too much flow from the evap side, so I think I will lengthen that captube a little.

Also I have to braze up some sort of manifold for the propane and r23 bottles to connect to, I cant swap the whole time. I think then I will get the charge better.

Quote:

---

Originally Posted by LukeXE

Don`t think so NoL, under load R23 will boil at -60*C, maybe less, it`s not enough for R14. To have "normal" discharge with R14 Hx temp should be around -75*C under load...

---

IIRC, it shouldn't be a problem.....at least it isn't in my auto ;)

@latent heat of vaporization: You sure? My chart puts it at about half of that of r134a, and 3/4 of r507.

Hmmmm I think my charts wrong then!
*going to have take revise it over out of the air liquide library again!*

Quote:

---

Originally Posted by s7e9h3n

IIRC, it shouldn't be a problem.....at least it isn't in my auto ;)

---

isn't that kinda the way argon helps the situation?mixing with r14 and giving higher suction pressure with better temps (IIRC)