Vacuum Cooling possible?

[Chris Beard]

An alternative would be to highly presurise the medium in the pc case. This way conduction would be higher. However - air conduction is crap so how about a highly presurised bath of amonia?

//edit: Just to note ammonia is highly caustic will melt most of the metals and your lungs so please don't try this without labratory conditions and relivent expertise available.

 

[Marse]

Who needs a vacuum - I'd go for a more conventional approach.

Lots of nice clean filtered air. Leaving the side off is optional.

 

[how random]

Who needs a vacuum - I'd go for a more conventional approach.

What is that?

 

[Marse]

A couple of large air filters intended for a car [or something bigger] with a mains operated fan inside pushing air through the duct into the PC.

Quite practical in the right circumstances/location.

I’ve no doubt it’s very effective and reasonably quiet considering the amount of air it should move.

 

[doctoe2260]

Vacuum flasks reduce heat loss by stopping heat transfer by conduction of convection, and reducing radiative losses to a minimum by using a silvered inner (inside of flask is shiney). They keep stuff cold by not letting heat in. CPU's generate a crapload of heat and it would not be able to get out if a vacuum surrounds it! The AC idea would work and indeed has been successfully implemented by many, especially in the US where AC units are common.

 

[GeX]

Harsh life for the compressor, most compressors are designed to run 24/7 all year, stop / starting a compressor will do more harm as you will be exerting stress on the motor windings and mechanical components inside the compressor.

yeah, this is why the compressors on all domestic and commercial refridgeration systems run 24/7.. oh wait, no they don't

course what you could do...

couple of high power tec's sat between some water blocks and some massive heatsinks with big fans on them, connected to a pump, then connected to a heater matrix with a big fan on it.

tecs pull the heat out the coolant flowing in the water blocks, fans on the sinks blow the air away, heater matrix temp drops and the big fan on it blows cool air into the case.

 

[JoeCooper]

i heard someone compacted their entire machine in 0% conducting oil... then stuck the thing in a fridge.. apparently cpu temp was down to 4deg

 

[MoD_Callidus]

thought I'd seen that idea before, clever things them fat playsuited gits in teletubby land !

 

[Tom|Nbk]

Guy's smoking some strong **** pass it over.

 

[mattyfez]

Use an RVK duct fan to force air into the case, with passive exhausts, that will keep the bugger cool, about 120 cubic feet per min for the smaller models ( they measure about a cubic foot in size)

quiet and very effective lol

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[satman]

U need a xclio 6030 PLUS-B (Propeller) case ....


"ENORMOUS BLUE LED 360MM FAN SIDEPANEL"

FAN SPEED CONTROL WITH ON/OFF SWITCH ... lol

 

[Denno]

All of this talk of vacuum flasks reminded me of the time I met David Beckham.

I was at a training session and he came up to me and said "what have you got there Denno"; he was of course referring to my new tartan vacuum flask. I said "well David this is a vacuum flask, and it keeps hot things hot and cold things cold."

"Wow, that's really cool I need to get Vicky to get me one of those". said David.

The next day I saw David at the training ground again and he came running across to me waving his brand new Burberry vacuum flask at me. "I've got one, I've got one" he shouted, "isn't it fantastic". I said "that's brilliant, what have you got in it?"

"Tomato soup and a choc ice" he replied.

 

[how random]

Nice joke

 

[drunkenmaster]

yeah, this is why the compressors on all domestic and commercial refridgeration systems run 24/7.. oh wait, no they don't

course what you could do...

couple of high power tec's sat between some water blocks and some massive heatsinks with big fans on them, connected to a pump, then connected to a heater matrix with a big fan on it.

tecs pull the heat out the coolant flowing in the water blocks, fans on the sinks blow the air away, heater matrix temp drops and the big fan on it blows cool air into the case.

nope, all phase change systems are really designed to run 24/7. its the same with a lot of mechanical things. once running theres no real issue, its the constant starting and stopping that kills them. you don't want to run a fridge uni 24/7 because it will use 100's and 100's of quid a year to run. you just want it to turn on every now and then to maintain a semi cold temp and insulate as well as possible to slow the heat down. the other thing thats a problem is when turning off phase change the pressure is essentially messed up, you can get the gas in the wrong pressure state in the wrong side of the system which ain't great for it. as he said it can take a long time to settle down. 100's of people rip the units out of fridges to make chillers, and a while ago to turn into 24/7 phase change units with no issues at all.

the pressure at start up with pumps, engines, most stuff really is much higher, uses more juice and is more prone to failure than the same systems while running.

 

[RJC]

nope, all phase change systems are really designed to run 24/7. its the same with a lot of mechanical things. once running theres no real issue, its the constant starting and stopping that kills them. you don't want to run a fridge uni 24/7 because it will use 100's and 100's of quid a year to run. you just want it to turn on every now and then to maintain a semi cold temp and insulate as well as possible to slow the heat down. the other thing thats a problem is when turning off phase change the pressure is essentially messed up, you can get the gas in the wrong pressure state in the wrong side of the system which ain't great for it. as he said it can take a long time to settle down. 100's of people rip the units out of fridges to make chillers, and a while ago to turn into 24/7 phase change units with no issues at all.

the pressure at start up with pumps, engines, most stuff really is much higher, uses more juice and is more prone to failure than the same systems while running.

When the comppressor stops the presures will qualize, problems occur when refigerant migrates into the oil, if been off for a while liquid refrigerant will migrate to the coldest place in some cases could be the compresor.

The old electric bill will be high when running constant.

Rob

 

[Starfall]

When the comppressor stops the presures will qualize, problems occur when refigerant migrates into the oil, if been off for a while liquid refrigerant will migrate to the coldest place in some cases could be the compresor.

The old electric bill will be high when running constant.

Rob

This is generally only a problem for air conditioning compressors when the systems static charge is in saturation, what you described can happen in this case as the liquid charge migrates to the compressor and "sloshes" around the bearings which on the next start cycle causes wash out of the bearings until the compressor body reaches a high enough temperature to evaporate the liquid. Commonly the propper means to prevent this is to use a crank case heater to warm up the compressor body before the system is started.

However generally the large shell volume of a reciprocating compressor in a CPU single stage means that the system charge is not in saturation and this problem is not present.

Most industrial sized compressors can take a maximum of 3 - 5 starts per hour which can cause a problem with hysteric control systems, smaller domestic reciprocating compressors can generally handle 10 - 12 starts per hour such as those in domestic fridges and freezers.

What drunkenmaster is saying seems to be starting a system with a high pressure difference, which will cause increased load on the start rotor windings even on high start torque compressors. Fast equalisation valves to bypass discharge to suction can be used in this case but if a system did require this precaution on a regular basis a more effective method of control could and should be used.

 

[RJC]

This is generally only a problem for air conditioning compressors when the systems static charge is in saturation, what you described can happen in this case as the liquid charge migrates to the compressor and "sloshes" around the bearings which on the next start cycle causes wash out of the bearings until the compressor body reaches a high enough temperature to evaporate the liquid. Commonly the propper means to prevent this is to use a crank case heater to warm up the compressor body before the system is started.

Other ways which split manufacturers use is an thermal jacket which helps to maintain compressor temp after operation, like you say larger comps use CCH to maintain oil temperature during the off cycle, nice big repair bill if when they do fail .

However generally the large shell volume of a reciprocating compressor in a CPU single stage means that the system charge is not in saturation and this problem is not present.

This I suspect is due l to the low charge levels in most phase change units.

Most industrial sized compressors can take a maximum of 3 - 5 starts per hour which can cause a problem with hysteric control systems, smaller domestic reciprocating compressors can generally handle 10 - 12 starts per hour such as those in domestic fridges and freezers.

I thought the figure was lower on domestic compressors for starts per/hr.

What drunkenmaster is saying seems to be starting a system with a high pressure difference, which will cause increased load on the start rotor windings even on high start torque compressors. Fast equalisation valves to bypass discharge to suction can be used in this case but if a system did require this precaution on a regular basis a more effective method of control could and should be used.

I re-read his statement again saw what his was saying, the starting bypass valve do a good job in releaving pressure on the motor, ambient temperature can also have a effect on starting currents.

Rob

 

[Amonlym]

I dont know much technically about compressors, so i defer to your knowledge.

i was always told however (and read) that running things like fridge/water chiller compressors constantly caused them to overheat, cook their bearings and sieze. im not sure if thats down to the charge or the compressors or what.

 

[RJC]

I dont know much technically about compressors, so i defer to your knowledge.

i was always told however (and read) that running things like fridge/water chiller compressors constantly caused them to overheat, cook their bearings and sieze. im not sure if thats down to the charge or the compressors or what.

Hi there, what keeps the compressor cool / at a reasonable temperature is the suction gas returning from the evaporator, the suction gas temperature depends on the application which is being cooled, for normal a/c unit for a room you will be evaporating at 0c to 4c idealy you would want 5-8c superheat so the gas temperature returning can be in the range of 5c - 9c.

If your cooling a freezer then you will be evaporating in the -temps so the gas temperature returning could be - figure, but this all depends on the design of the refrigeration plant.

Hope the above helps.

Rob

 

[Starfall]

This I suspect is due l to the low charge levels in most phase change units.

Yes, in custom units the system charge will be under 100g of refrigerant and as low as 60g for stock prometia's and vapochill's. The first stage charge for a cascaded system using capillary tube on the first stage will be more like 100g, a TEV regulated first stage with reciever is more like 200-300g.

I thought the figure was lower on domestic compressors for starts per/hr.

It realy depends on the metering device, capillary tubes like in a small beer cooler or fridge/freezer will equalise relatively quickly whereas a TEV / CPEV will be forced to equalise through its bleed hole and depending on the volume of liquid in the reciever and and low side volume this can take some time until the pressure difference is acceptable for startup.

With the last post Rob, the small low back pressure compressors like in domestic fridges and freezers rely mainly on case cooling not return gas cooling.

With larger plant like you described the compression process is very close to adiabatic and requires carefull consideration of suction superheat but in the small LBP compressors a huge amount of the heat of compression is dissipated into the shell and not the discharge.

For example these r134a compressors are specified to opperate up to +32C suction gas temperature at a saturated evaporation temperature of -30C, i.e. 62K superheat! Under these conditions a perfect compression process the discharge temperature should be ~+130C yet the observed discharge temperature is approx +70C due to this compressor shell cooling.

Tom