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Friday, January 17, 2014

CryoBUG vs Polycold's PCC Chiller

Polycold® also makes a compact chiller which they call the PCC™ (newer version of Polycold's CryoTiger™). The major differences between what they make and a CryoBUG, is that their unit uses room temperature flex lines to interconnect the Cold Head with the Compressor Unit. And they also offer a charge blend that can do liquid Argon temperatures (-186°C) at 6 watts of heat load.

Peeking under the hood, the differences become even greater. CryoBUG uses what is referred to as autocascade refrigeration to achieve its very cold temperatures, whereas the PCC is primarily based on the Joules-Thompson Effect with no inter-stage phase separation. Utilizing only the JT method tends to be rather tough on the compressor, causing it to have high differential pressures, resulting in poor cooling which can considerably shorten its life. However with an autocascade system like CryoBUG, compression ratio is low and compressor cooling is excellent, thereby promoting a longer lifespan. Also an autocascade system is generally more efficient, requiring less horsepower for a given temperature and heat load.

And if you look at the following chart you will see that CryoBUG is actually more power efficient while also taking on more load (CryoBUG has a smaller compressor then the PCC).
CryoBUG vs Polycold PCC Comparision Chart

Presently Polycold® offers 4 different gas blends for the PCC, and two different Cold Heads (Standard and High-Performance). I picked the two gas blends that came closest to CryoBUG's -150 blend for my comparison (other CryoBUG refrigerant blends are possible that would yield even higher capacity results, albeit at a warmer temperature).

The PT-16 although a great performer, tops out at 24 watts according to Polycold's literature. The PT-30 looks to be the closer match for the CryoBUG, but it is limited to 32 watts, and quickly warms up above 20 watts of heat load.

CryoBUG Demo Unit
Another noticeable difference between CryoBUG and the PCC, is that CryoBUG is equipped with a very nice tech package, including a temperature display, dual compressor pressure gauges, and a remote control/monitoring capability. Also the safety system is much more robust, having sensors for low and high pressure, and high liquid line conditions (the liquid line is the refrigerant line exiting the air cooled condenser, if it gets too hot then it's probably time to clean the condenser). All of the faults will produce a visually mapped front panel display that tells you specifically which one has occurred.

This stuff isn't just a bunch of unnecessary bells and whistles. It all serves to let the user know how well the unit is performing its job, and gives them a heads up if something is beginning to go wrong, thus allowing them time to schedule a service. And probably one of the most important additions, is the inclusion of the built-in temperature display. Kinda nice to know what temperature your chiller is producing, after all it is a refrigeration system.

The PCC unit does have an hour meter, which CryoBUG does not, but this was primarily done because the PCC has an oil absorber cartridge that needs changing after so many hours of operation (CryoBUG doesn't need this, since it has excellent oil management not reliant upon parts that need to be changed).

I think the biggest advantage that the PCC has over CryoBUG, is the flexibility of being able to place the Cold Head independently from the Compressor Unit. This could come in handy for many situations. And although it is certainly possible to provide a similar feature on the CryoBUG, it would never be quite as good as the PCC in this regard. This is  primarily due to the colder line temperature, and not being able to offer self-sealing couplings as is the case with the PCC. Also there would likely be considerable performance degradation if very long lines were utilized. However with all that said, CryoBUG's line-less, coupling-less implementation does insure trouble free operation.

I think that pretty much sums it up.

Click here for more information on CryoBUG

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