Basic SMALL refigeration system

[M@@Home]

Hello!

I am a fourth year Student at Warwick University and I’m building a cooling system for my Thesis Project. Ill start by telling you all that I’m NOT a refrigeration engineer, and I’ve never looked into this before so I have no idea what I’m talking about:

To cut the story short I have a box which needs a cooling element on the inside (max size of element: 400mm x 200mm) and a radiator on the outside (same max dimensions) and the most compact & lightweight compressor/control system (basic thermostat) possible.

(For the purposes of this assume it is roughly the same as making one of those small beer fridges from scratch. 600mm x 600mm interior etc (2ftx2ft) cooling 25DegC down to 5DegC)

Does anyone have any ideas where to get the parts from in the UK?? (Don’t worry I will have help assembling it etc from a proper engineer, I just need to source the parts.)

Also the refrigerant cannot be flammable or harmful, any ideas what to use with it?

Thanks Very much for your help


Matt

(A poor and desperate student!)

p.s. Im not sure if this is the right forum to post in, so sorry if its not

[star882]

Could you use Peltier (TEC) devices? Very easy to use and no special tools necessary.

[Targ]

i did a very similar thing for my 3rd projecy @ cardiff uni

www.dean-wood.co.uk
http://www.climatecenter.co.uk/cont/default.html

was where i got most of my stuff.

you need to work out the exact load in watts before you can plan on refrigerants or components.

but assuming a load of sub 1kw, at that temperature, *R134a is non toxic and non flamable.
*1/3hp hermetric (spelling, its early) compressor
*suitably sized condenser
*finaly a metering device your choice of cap tube/tev/cpev

should do ok, but like i said, more spesific detail on the load and situation before too much planning.

targ

[M@@Home]

Hi,

Thanks for the speedy reply. I have included a full specification below:

Basically the internal diamensions of the 'fridge' are 510mm (Wide) x 900mm (Deep) x 260mm (Tall) (looking at the front, strange shape I know ).

Its as close to perfect insulation as I can get: the walls are made of a super low conductive composite of:

3mm Mild Steel, 40mm Vermiculite, 6mm Mild Steel
(Inside, Middle, Outer casing)

The inside temprature has to be kept between 10DegC and 35 DecC (my values in my first post were wrong ).

There is a heat source inside producting
3100 BTU/hr (908 Watts) .

Any ideas about what size/make/model of compressor I need (as dimensionally small as possible, doesnt matter how much electricity it consumes).


Thanks Very Much


Matt


(p.s. A fan system would work better, but it has to be refigerated, thats the task I have grrr)

[frank]

As a 4th year student at University (supposedly about to graduate) I think that you should have at least researched your project in more detail, i.e. determined the cooling load, insulation factors etc.

Your question seems to be geared more towards a college student level.

If you were just after refrigeration parts I would have expected questions like - " where can I purchase an evaporator rated at 800w @ -5deg C"

Are you trying to get some of us to do your project calcs for you? or are you really struggling to understand the basics?

[M@@Home]

(not taking offence to the last reply).

I am a comp sci student that is simulating a micro computer cluster in convection free environments. (i.e. A computer in a box with no fans - sterile environment computing).

I have to build my own test rig as one doesnt already exist. This rig wont be included as part of the project that I submit, just the computer inside and the test data.

The only reason I included so much detail is that I have no idea what I am doing and I have never studied engineering (or refigeration systems) before. To be honest I dont need to know anything about the calculations, and it would make my life more complicated if you told me the calcs, so to stop me cheating, dont tell me.

therefore ignore my other posts, i will start again:



---------------------------------------------------

Hi all,

I need details of the parts needed to cool a box (with almost perfect insulation) to between 10 and 35 DegC when there is a computer inside producing 3100BTU of heat.

I dont know anything about these systems, I am guessing that I need a compressor, internal element, external radiator, some copper pipe and a thermostat. (excuse my ignorance on the parts list).

Also it needs to be light and small (and pref cheap).

Thanks Very Much


Matt

[star882]

Find a used but working window A/C and modify it to your needs.

[M@@Home]

Yeah I was thinkin along those lines...

Would a beer fridge be powerfull enough? (the little 2ftx2ft ones).

Could I just lengthen the pipes and solder it back together and get some one to re-gas it, or are they not that powerfull for what I want?

Thanks

Matt

[star882]

Would a beer fridge be powerfull enough? (the little 2ftx2ft ones).

3100 BTU/hr (908 Watts)

Not even close.
http://www.ocforums.com/showthread.php?t=373263
BTW, that figure is quite high. Is it for an 8 way Britney?

[frank]

(not taking offence to the last reply).

I am a comp sci student that is simulating a micro computer cluster in convection free environments. (i.e. A computer in a box with no fans - sterile environment computing).

I didn't mean any offence - it's maybe the way your question was asked

If the requirement is only to keep the insulated box between 10C and 35C then you could simply do this with cold water.

If you buy some soft coiled copper pipe from a refrigeration wholesalers, say 1/2", then you could wrap this around a cylinder of suitable size to form a coil that will fit snuggly inside your box.

Run cold tap water, which should be at about 10C this time of the year, through the coil via a hand valve so you can regulate the flow.

If you wanted to control to a tighter tolerance, say 10 - 15C then you would maybe want to use refrigerant. With a heat load of 0.908kw, water entering temperature of 10C leaving at 12C you would need a flow rate of 0.108 l/s.

[M@@Home]

Dont worry frank! cheers for the reply,

I didnt know you could get temps that low with water cooled!

Ill have a go with that idea thx! (costs be about £20 compared to alot more for a refigerator that wont work!)



(BTW Star 882: Its a 4way Itanium Cluster with 2x 18GB 15k SCSI, RAID 1 & 8GbDDR. Its for processing VR models in the medical sector. (thats the sterile environment bit!) The processors are all on one board, quite tightly compacted)

[The MG Pony]

I run a dual Xeon 3.2GHz @ 32C on Water. the system is closed loop and uses a 240mm Radiator to cool the water. I usualy put the rad, out side for even better temps. fyi it is OCed from 2.8 to 3.2GHz

Water is definatly the way to go, and you could even use a chiller to go sub ambiant.

[frank]

fyi it is OCed from 2.8 to 3.2GHz

I don't understand this - could you elaborate please ??

[The MG Pony]

as in I have both my processors overclocked to 3.2 Gigahertz from their normal operating clock of 2.8GHz thats an increase of 400MHz I concentrated on driving the front side buss up more then raw proc speed, as the buss is what effects your over all speed. Thank fully I managed to get over 40% of the OC on the bus and that really got things going nicely.