Cascade Project - First Build

[Sk_rmouche]

A CPEV is dial a load and that's where it stays. Thats the issue...

For example this 3 stage cascade was a complete wreck because of the CPEV and ended up back with CAP.

You know I've a collegue who works with Sapratin, a german company, specialized in two-stage cascade for laboratory stuff ( freezer and climatic room ), they work with cap tube too. But there is several years of work to define the exact sizing, amount of each gas, etc ... And with all that stuff they still managed to install a solenoid valve that control the massflow @ the evaporator, exactly like EEV's ... ( don't know why they aren't using EEV directly ! ).

Point is : if he has access to EEV and other variable expansion device ( and I bet he is, EEV @ first stage, why not on the second ? ), cap tube is really the weakest link.

You're talking about CPU and fluctuant charge. Guess who's the expansion device that have been using since the dawn of refrigeration process, with non-fluctuant load ? Cap tube !

Cap tube is extra reliable, low cost, and easily replaced ( as long as you have the exact size obviously ), that's it IMHO.

[samsarulz]

The main problem in my country is the cost of everything related to the construction of the Cascade. Dont know if its expensive, but a regular EEV has a retail price if 110 USD and that is the same of the smallest oil separator.

By the way, I have read about one oil seps with float system, do you recommend them over the regular ones?

Thanks again

[runmc]

By the way, I have read about one oil seps with float system, do you recommend them over the regular ones?

Thanks again

yes

[Sk_rmouche]

The main problem in my country is the cost of everything related to the construction of the Cascade. Dont know if its expensive, but a regular EEV has a retail price if 110 USD and that is the same of the smallest oil separator.

By the way, I have read about one oil seps with float system, do you recommend them over the regular ones?

Thanks again

Same price here in France, maybe even a little bit more. For ~ 150$ you have complete set of a danfoss AKV ( body + orifice + gasket + filter + coil ). But you'll have to get a PID controller to get the AKV working. Obviously, electronic expansion is more expensive than cap tube

[Kevin Hotton]

samsarulz,

For simplicity and lowest cost, I would use captubes.

I calculated the captube for my presented design of 9-feet of 0.052-inch ID (2.75-meter of 1.32mm ID) for the first-stage. I would estimate the captube for the second stage to be the same diameter, but maybe 10.5-feet (3.20-meter) long.

Kevin

[samsarulz]

Ok, the captube that Im using right know is 2,5m long, but can be extended. BTW, 1,32mm isnt a bit large, well nevermind, will ask if is that diameter is available.

Thanks

[runmc]

Really no point in building a cascade and then use a low pressure gas in the second stage. You could achieve the same thing with a single stage. If you feel that you may be able to get your hands on a high pressure refrigerant in the future I can see the point. Cap tube on the second stage for sure.

[samsarulz]

Really no point in building a cascade and then use a low pressure gas in the second stage. You could achieve the same thing with a single stage. If you feel that you may be able to get your hands on a high pressure refrigerant in the future I can see the point. Cap tube on the second stage for sure.

At the moment, the best gas that I can buy (for 1st stage) is R-402a, but the 10kg tank cost too much, like 320 USD. I think that taking Kevins advice is the best decision. Then test the cascade and learn how to operate it properly. From this point, Ill look for cooler gases.

[runmc]

r402a will be a good first stage gas. I would use r507 but I also have r402a

[samsarulz]

Following what Kevin suggested, I started filling the gases. As for 1st stage I used R-404a and the Evap temperature with 180W peltier load is around -42C. Will test this week with another one of 238W. In 2nd stage I put R22+CO2 with the suggested ratio (85% and 15% respectiv.)

Testing a lot reached almost -49C in Evap with the same 180w load. It seems this is almost the maximum I can achieve. Maybe I can go a bit colder testing other pressures. Speaking of which, maybe low pressure is a bit down. I?m keeping the specs of course. As for the 2nd stage pressure I have 15-20 PSI in low pressure and 175-200 PSI for High pressure .

Last but not less important: Installed some probes (Thanks Sdumper por the PID controller link) across the Cascade, and with actual R22+CO2 specs, the HX temperature is almost -20C.

Well... anyway, those temps are not the the ones I was looking for, but they are useful in order to start in the OC Extreme Cooling World. Looking for local stores to import R-23. They sure said that will be in a few months.

[samsarulz]

Greetings,

In the end I did not get satified with those results. As a 1st cascade and the knowledge gained I appreciate it and of course oeveryone who posted here helping.

Last week I got my hands on a little cilinder (14kg) of R-1150. Will be testing the little cascade with R-507-R1150. But before that Ill buy a receiver, oil separator and mod a bit the phase change case because is very heavy jajaja.

If something happens I will post it right here. If the compressors are not capable of taking the pressure or the loads of the 4770K or other CPU Im considering switching to a 9000 BTU rotary compressor for 1st stage and at least 1/2 hp comp for 2nd stage.

Hope you all a happy new year!

Jose Luis E.