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Old 31-10-2008, 18:49   #106
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Just to revive this thread.. and to say that in the past week I have managed to get 4 more from Outlet stores..

One guy at an outlet store said that whenever they do sell out.. more come in from the warehouse.. so if you want one.. call around.

Louis
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Old 06-11-2008, 20:21   #107
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Finding a solution to the freezer/s problem

Good day all,
I have been following this thread for some time now and at last here I am hat in hand to see if I can find some assistance. Vega works with WHO supported programs to provide help with child immunization and other public health programs for developing island nations. That means we need dependable freezers and cold boxes to carry medical supplies often for months at a time. Right now we are refitting our cold boxes and can use all the help available on what and how to get the most dependable and energy efficient systems. The three boxes average about 130 liters each and are all side by side in the same construction. The insulation is 6" at the bottom and an average of 4" around the sides ( back and one side is 6") there is 4" between each box. I like the idea of the Stirling units but can't seem to get an answer out of them. That seems to leave the old Danfoss compressor route as the only one on offer. Any ideas? I would prefer not to use water cooled as the waters we work in are warm and full of life that tends to block strainers and pipes quite often. Any chance we could convert our existing house hold 220VAC deep freezers to this application? Not the best I know but at least available. Thanks in advance for the help.
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Old 06-11-2008, 21:27   #108
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H/V Vega

Did you try this guy?

jedwards@globalcooling.com

Very helpful individual. Another good outfit is fridgefreeze.com

The US gov and medical industry uses their units. Not Stirling, but very efficient.
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Old 06-11-2008, 23:04   #109
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Thanks but still looking.

Thanks Minggat that seems a good tip. I have sent him an email in hopes he will answer. Checked the site you mentioned but those are portable units and ours are fixed ( very much so). Then again every bit of information is always useful so thanks again.
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Old 13-11-2008, 19:40   #110
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Originally Posted by H/V Vega View Post
Thanks Minggat that seems a good tip. I have sent him an email in hopes he will answer. Checked the site you mentioned but those are portable units and ours are fixed ( very much so). Then again every bit of information is always useful so thanks again.

You really need to get in touch with mr edwards at Global Cooling.. I have talked to him in the past, and your application is EXACTLY the application that they developed the Stirling cooler for.

If you have looked at their website (global cooling) you can see that there are products designed for just what you are doing.

I will say that the stirling cooler is THE MOST EFFICIENT way of cooling that is currently available hands down.

On here we only talk about the portable coolers that TwinBird had made (specifically the one marketed by Coleman here in the U.S.) but from what I know about the portable cooler, they could absolutely work for your application... One thought is to use the portable cooler to freeze water or cold packs, then use those to keep your medical supplies cool.

When I talked to Mr. Edwards, we discussed the possibility of running the stirling cooler on solar panels only in the day.. running them with as much output as they could make while the sun shines, then using frozen water or cold packs to carry thru the night.

The small cooling unit only draws about 40 watts of power when it is running at its maximum output, so a reasonably sized solar array could run it easily. If you wanted to have it operate at lower power 24hrs a day you would need a much larger solar array and a storage battery.

Again,, the people over at global cooling would be able to help you. Like I said.. the application that you describe is the reason they developed the stirling in the first place.

Louis
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Old 14-11-2008, 01:47   #111
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Cooling for Historical Vessel Vega

Thanks I agree completely that their kit might be the best answer but have yet to have any real reply from them. Could you send me this Mr. Edwards email? I would love to get this going. We really must do something as we are scheduled to start our mission to the Solomon Islands soon and that requires freezers we can depend on. Oh and it would be nice to have the odd cold one too!
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Old 14-11-2008, 01:54   #112
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I am just wondering if we might be able to use those units with eutectic ( how ever its spelled) holding plates. If so that could be a real bonus and reduce the power burn at the same time.
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Old 20-07-2009, 23:40   #113
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Sterling cooling in rough offroad conditions: vibrations & off-camber

Hello dear Group,

Let me be the one to revive this thread again, this time possibly for the longest time since it's last hartbeat....)


Several years ago, I added the GlobalCooling link (both .nl and .com) on my website....at that time, I contacted the Dutch office by email more than once, but never got any answer....so I more or less rated it as either 'vaporware', or industrial prices equalling that of gold.

Only today, while adding & updating a bunch of fridge/freezer links on my homepage, I got distracted once again with this intrigueing product (also because I recently came across a German Thermocon medical box with -28C specification), and wandered into this forum, with it's lovely discussion.
Of course, after the first excitement I was heartbroken to hear that there *was* a consumer-grade product out there, but that it didn't sell, and vanished from the market at rockbottom prices....without me having a chance to grab one (despite high shipping cost from USA to NL).

That said, the note on this max-12-degree-angle raises 2 more, similar offroad-related, questions:

1) at steeper angles (give and take the specific orientation), does the Stirling unit just quit operating, binary-style, complety off, or does it keep working, with degraded output and/or efficiency?
(note that worst-case offroad is more than just a steep angle, it can also mean a vehicle completely tipping over, 90 degree or more)
(also note that there is only one compressor type that can stand such abuse, the Kissmann half-hermetic unit, because it is an oil-free concept (stock Danfoss (with oil) can take only 30 degree, Kissmann-modified Danfoss 45 degrees (although there are conflicting notes whether that is allowed continuously or only briefly), and Engel/Sawafuji 60 degrees (which I learned only recently, not many sites mentioning it))
(actually, I have been pondering about adding an emergency tipp-over detector (mercury level switch), into/onto the compressor's electronics box....just not sure how vibration-sensitive such mercury switches would be, in offroad-context (vibrations))
(alternatively, I would just create an on/off switch at the dashboard, to avoid at least the non-emergency extremes (steep uphill/downhill trajects))

2) which leads me to the second question: can the Stirling concept operate under continuous harsh vibrations?
I have been told the stock Danfoss and even the Kissmann-modified Danfoss don't like a worst-case vibration scenario, because of the oil starting to foam....not sure how the Engel/Sawafuji would rate though.
Kissmann Sr. himself says their oil-less half-hermetic, until production ended, sold as hot-cakes in the middle east, as OEM equipment on Mercedes dump trucks for construction sites....apparently this type of compressor was the only one to survive that harsh environment over time)
(that said, automotive airconditioning doesn't suffer from worst-case vibrations either, and that one contains oil too....)

Thanx for any information, opinion or clarification on both subjects!

PS: anyone seen a Colemand for sale recently?.... )
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Old 21-07-2009, 00:06   #114
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Well now, it has come alive again...

About the vibration I don't have any exact data. I do know, however, that the stirling cooler uses CO2 as an intermediate, which is in a thermosyphon around the chamber. This means that the cooled CO2 slowly drops down by gravity (higher density when it's colder), and the slightly warmer CO2 on top is going back to the cooling. This is the reason for the 12 degree slope restriction. I can imagine that an excess of vibration will not help the process. On the other hand, it is (widely?) used in vehicles.... and they all vibrate. Also, in the Past, research has been done about putting a Stirling engine in a car. It's responsiveness kept it from getting any further at the time.
I think that, at the least it will keep running, but the cooling will be worse.

on the PS: last year i bought one from the NL office of Global Cooling (yes, I am in NL too). They do sell it as an "Engineering Sample". If it's still on the website, it should still be available.
It ain't exactly a bargain, though. As I recall, it was about €485 excl. BTW.

I hope this helps...


Hope this helps.
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Old 21-07-2009, 09:58   #115
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It's always nice to hear more people wanting our stuff.

Now, just to clarify one misconception:

The "Coleman" box (SC-C925) was never discontinued by the manufacturer. In fact not only does Global Cooling still sell the unit but even Coleman Japan still sells it. The main reason for Coleman US to stop selling, was not because of slow sales. Shortly after they took their first delivery of Stirling Coolboxes, their parent company, Sunbeam, declared bankruptcy. The new management decided not to continue the project for "internal" reasons. As you know the demand for the SC-C925 has never really fallen since it release and we are always looking for distribution outlets in new markets.

Now, to answer your questions:

1) As I have mentioned in earlier posts, the angular restriction is a function of the CO2 thermosiphon. This device is used to transport heat from the cold chamber and is completely independant of the FPSC (Free-Piston Stirling Cooler). THe two units are simply 'bolted' together. The FPSC itself couldn't care less what angle it is running. Horizontal, vertical, inverted or anywhere in between. The Stirling will never "quit running" even if the cooler is upside down but that is the crux of the problem. Without a load on the FPSC (remember that the thermosiphon is what tranports the heat from the chamber to the FPSC) the temperature on the cold head will plummet to as low as -100 deg C. This can cause the CO2 in the thermosiphon the freeze solid and block the flow of heat to the cold head, for a while, even if you turn the cooler back over. Short duration (a few minutes) inversion is unlikely to cause noticable problems and off camber operation will only decrease the amount of heat being transported to the FPSC decreasing efficiency. The flow reduction in off camber situations is because of weakened forces (rememeber your trigonmetry) drawing the more dense, liquid, CO2 to its proper location. Once the unit is righted the CO2 plug will eventually 'defrost' and the untit will work as if nothing had happened. In extreme instances, you may have to remove power to the cooler for a short time to allow the cold head of the FPSC to 'warm' up to more reasonable temperatures to encourage the frozen CO2 to defrost. Again, as I mentioned in earlier posts, in some orientations, the thermosiphon will operate, with no degradation at all, even when the unit is rotated 90 degrees (mechanical side up, with the door out like an upright refrigerator).

2) As for vibration, the FPSC itself is virtually immune to the effect of external vibration. a close cousin to the unit in the SC-C925 was the only cooling technology to ever be operational during the launch of the Space Shuttle. Unless the FPSC in the SC-C925 is subjected to a continuous and high amplitude, steady, axial vibration of 79.1Hz it will not likely even have to throttle back from full capacity (assuming that is has to operate there anyway) to minmize the slight risk of contacting its internal bump-stops. In fact steady random vibration will enhance the performance of the thermosiphon by 'jiggling' the liquid CO2 down the slope to where it can pick up more heat.

Feel free to contact me by phone or email if you still have questions.
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Old 22-07-2009, 10:30   #116
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Originally Posted by ericb View Post
Well now, it has come alive again... About the vibration I don't have any exact data. I do know, however, that the stirling cooler uses CO2 as an intermediate, which is in a thermosyphon around the chamber.
Yes, read that, only later I started pondering about this concept, in a different context, 'what if I build a box/system from scratch, where does the 'evaporator' go, how does it connect to the Stirling'....of course, I can use any heat-transfer system, even use (energy-consuming) electric pumps and ordinary fluids (but of course, for the most extreme temperatures (and worst-case fluid/solid expansions!), fluids have their limits (I believe the glycol-dilution table (eutectica) ends at -60F). Btw, what would the smallest fluid pump option be in this context? I guess the largest variety can be found in the PC-(water)cooling industry? (gambling a bit with glycol-compatibility of course)
Quote:
This means that the cooled CO2 slowly drops down by gravity (higher density when it's colder), and the slightly warmer CO2 on top is going back to the cooling. This is the reason for the 12 degree slope restriction. I can imagine that an excess of vibration will not help the process. On the other hand, it is (widely?) used in vehicles.... and they all vibrate. Also, in the Past, research has been done about putting a Stirling engine in a car. It's responsiveness kept it from getting any further at the time. I think that, at the least it will keep running, but the cooling will be worse.
Lack of responsive/reactiong-time is the territory of hybrids....)
Quote:
on the PS: last year i bought one from the NL office of Global Cooling (yes, I am in NL too). They do sell it as an "Engineering Sample". If it's still on the website, it should still be available.
Never saw any product for sale on the .NL site, not now either....was it really actively marketed online, or did you ask by phone? (send them another email yesterday, again no response)
Quote:
It ain't exactly a bargain, though. As I recall, it was about 485 excl. BTW.
Not a bargain as in the Coleman-sell-out context, but the higher-end compressor fridges are not much cheaper....only thing they offer more, in that price range, is an eutectic element....a shame that this isn't even optional with the Coleman/Twinbird.... (yes, I know that with a Stirling, the thermodynamics don't benefit from eutectica, but it would make the box more portable, plus absolutely silent at night) I should also note though that, being Dutch, I have never bought any compressor fridge above 130 euro, and I am on #5 now, after 4x Kissmann/IndelB TR825....) (the 3 with Kissmann half-hermetic all need a refill, but none is younger than 15-20 years, and only one cost more than 50 euro's, so they have no blame....) (and that 130 was only recently, for a Waeco RHD-85, BD35F/eutectic (currently being tested, lovely research project, given all the optional Danfoss settings/wiring....) (the fun part with eutectic fridges, at least those who have the evaporator hidden/untouchable under the eutectic element, is that some owners, clearing out their basement, test it too shortly, and then think/state that it is broken....)
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Old 22-07-2009, 11:05   #117
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Originally Posted by jedwards View Post
It's always nice to hear more people wanting our stuff.

Now, just to clarify one misconception:

The "Coleman" box (SC-C925) was never discontinued by the manufacturer. In fact not only does Global Cooling still sell the unit but even Coleman Japan still sells it.
Ah yes, never claimed that Twinbird stopped making them; it's just that Japan is one of the least 'overseas-customer-friendly' countries to deal with, even excluding the issue of shipping cost (which, by itself, is adding insult to injury....even ordering rare/exotic offroad literature is a pest). Never got a good insight in the Coleman conglomerate/policies either....already send a note to Coleman Holland, to see if they might have had some of these boxes, if only for testing/sampling....it only takes one freak high in the foodchain to get them across the border/pond....) Btw, perhaps you should interpret my earlier 'heartbroken' also in particular Dutch context, having missed such a nice bargain....) (even though shipping USA->NL wouldn't have been cheap either (not since USPS cancelled the option economy/sea) (my usual approach, trying to find exotic hardware only as used/surplus (gotta love the military btw....), would fail in this case anyway, just because there never were any large-scale sales, not even for more than a few years, and those who bought one knew and know darn well what they have, and probably will even clutch them with their nails when entering the grave....)
Quote:
The main reason for Coleman US to stop selling, was not because of slow sales. Shortly after they took their first delivery of Stirling Coolboxes, their parent company, Sunbeam, declared bankruptcy. The new management decided not to continue the project for "internal" reasons. As you know the demand for the SC-C925 has never really fallen since it release and we are always looking for distribution outlets in new markets.
Okay, good to hear....but I also must conclude that there is no active (consumer) marketing/distribution in Holland, of all places/subsidiairies, either? Nor in any European country? (there isn't much of that for most of the compressor boxes in NL either, only in the truck-segment (and even those for decades sourced abroad, while on international trips)....market is completely different in Germany/Italy)
Quote:
Now, to answer your questions:

1) As I have mentioned in earlier posts, the angular restriction is a function of the CO2 thermosiphon. This device is used to transport heat from the cold chamber and is completely independant of the FPSC (Free-Piston Stirling Cooler). THe two units are simply 'bolted' together. The FPSC itself couldn't care less what angle it is running. Horizontal, vertical, inverted or anywhere in between. The Stirling will never "quit running" even if the cooler is upside down but that is the crux of the problem. Without a load on the FPSC (remember that the thermosiphon is what tranports the heat from the chamber to the FPSC) the temperature on the cold head will plummet to as low as -100 deg C. This can cause the CO2 in the thermosiphon the freeze solid and block the flow of heat to the cold head, for a while, even if you turn the cooler back over. Short duration (a few minutes) inversion is unlikely to cause noticable problems and off camber operation will only decrease the amount of heat being transported to the FPSC decreasing efficiency. The flow reduction in off camber situations is because of weakened forces (rememeber your trigonmetry) drawing the more dense, liquid, CO2 to its proper location. Once the unit is righted the CO2 plug will eventually 'defrost' and the untit will work as if nothing had happened. In extreme instances, you may have to remove power to the cooler for a short time to allow the cold head of the FPSC to 'warm' up to more reasonable temperatures to encourage the frozen CO2 to defrost. Again, as I mentioned in earlier posts, in some orientations, the thermosiphon will operate, with no degradation at all, even when the unit is rotated 90 degrees (mechanical side up, with the door out like an upright refrigerator).
Okay, temporarily suspended cooling isn't bad at all....only relevant worst-case offroad scenario left is tipping over sideways, without having eutectic elements to take over the cooling process (doesn't have to be serious damage either, sliding slowly into a ditch/rut and hours of extraction attempts is enough to kill some good food....)
Quote:
2) As for vibration, the FPSC itself is virtually immune to the effect of external vibration. a close cousin to the unit in the SC-C925 was the only cooling technology to ever be operational during the launch of the Space Shuttle.
Just for fun, something I learned only recently: the Kissman TR825(EN) box (their oldest design, starting in 1964(!!), with proprietary/half-hermetic compressor was the only one ever *onboard* of a shuttle....being oilless, and orientation-independant, it was the only one NASA could use (at least at that time, not sure exactly which year(s) this was)....and this gravity-deprived application would be a no-go for a gravity-operating Twinbird too of course....)
Quote:
Unless the FPSC in the SC-C925 is subjected to a continuous and high amplitude, steady, axial vibration of 79.1Hz
Good to know, for any future problem-analysis....) (I believe there are very basic (mechanical) instruments that can detect the typical/main frequency of a vibration, so this would even be rather easy trouble-shooting....) (or even dash-mounted, when rattling over washboard desert roads....adjust vehicle speed accordingly....)
Quote:
it will not likely even have to throttle back from full capacity (assuming that is has to operate there anyway) to minmize the slight risk of contacting its internal bump-stops. In fact steady random vibration will enhance the performance of the thermosiphon by 'jiggling' the liquid CO2 down the slope to where it can pick up more heat.
In the earlier context of compressor fridges and off-camber sensitivity (btw, they completely fail/break/seize-up in such a scenario, due to lack of oil/cooling, overheating, more than just quit functioning!), I had already pondered about some exotic overengineered cardanic suspension, at least for the compressor itself (of course, that would require flexible hoses too)....) Btw, checking your previously posted pricelist: there is a rather steep price-jump for the most expensive (deepest-freezing/-70C) 25L box ULH-025, between 1 unit and 6 units....just because there is hardly any stock of those, and production being so much more efficient with 6 than with 1? (perhaps it is in the highest-end VIP-panels too?)
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Old 22-07-2009, 14:37   #118
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I got mine thru info@globalcooling.nl
Response time, as i recall, was allright.
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Old 22-07-2009, 16:43   #119
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Whew!

WJM

We are working to expand our direct presence in Europe and expect to have distributors there begin offering our portables before the end of 2010. The intital products will likely be the ULT25 and SC-DF25 with others following.

There are so many options with a FPSC system that I am not even sure where to begin with my answers as it is difficult to explain all of the nuances of Stirling theory in this format. For each answer I provide, you seem to have three questions. If you have more questions about the technical aspects of FPSC based cooling products and systems and how they work and can be integrated into custom insulated chambers, I would be happy to discuss them with you. PM me and I will give you my contact info.

Only the SC-C925 and its variants use the CO2 thermosiphon for secondary heat transport. The FPSC itself is also available seperately and can be integrated in several ways (see attachments). We also offer units that use forced convection which have no orientation limitations (SC-JS04 and SC-JS05)

As for a eutectic based systems, A FPSC system can take advantage of phase change materials just as much as compressor based system or any cooling system for that matter. Eutectic evaporator or plate based refrigerator systems use phase change materials as an energy storage method (think ice) in order to minmize energy consumption. Most FPSC systems don't worry so much about energy consumption (it's already about half of the compressor systems in our lowest efficiency system) and don't use phase change materials except in cases where the driving energy is being extracted from sunlight and it needs to stay cold overnight with out battery backup. Probably the biggest disadvantage to eutectic systems is that you are locked into a single temperature without using a phase change material with a eutectic temperature as low as you will ever need to set the unit combined with a secondary thermal regulation circuit/fan and many people seem to prefer the ability to change the temperature of their box from freezer to refrigerator and back. A very simple alternative would be to put eutectic material inside the box. If you want a temperature right about 0degC then use blue ice if you want it warmer there are several waxes that can be used. Just match the temperature set point you are using to the phase change material. If you really want to get fancy, fill the defrost catch tray on the SC-JS04/JS05 with your eutectic and set the temperature of the system acordingly to match and voila you have a FPSC refrigeration system with eutectic backup.

Space Shuttle mission STS-60 in 1994. M223 Stirling Freezer used to provide low temperature storage for expeiments and crew rations. ONLY cooling technology approved for operation DURING launch, at least up to that time. Who knows what they have tried since.

That said, a LOT has changed over the last year or so, especially WRT pricing and availability.

I'm not sure why you are not getting a response from GCBV, but when you get my email from the above mentioned PM or from a couple of posts up, copy me to your request for info to GCBV and I will try to figure out what is going on. Since I'm not 100% sure of exactly what is allowed in this forum (Moderators: I'm just trying to help. I am not attempting to sell anything. I do not get anything like commision. In fact, it is a pain in my butt to sell to anyone but our distributors. However, if they want it and I can help, I'll give it a go but there is zero, maybe even negative, pressure), lets just say that GCBV gets their inventory from me and I ship inventory all over the world.
Attached Files
File Type: pdf heat exchange.pdf (109.0 KB, 283 views)
File Type: pdf FPSC_Application_Examples.pdf (102.0 KB, 234 views)
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Old 22-07-2009, 17:57   #120
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look for the prices on SC-jso4 Refrig unit and coolers

I am looking to add something to my 27 ft. Hunter Cherubini. At present it has and icebox. I can't find prices any where on these Sterling units
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