Just saw this thread adn I was away for a week, still am away but I brought a computer with me to check forums and such (not a laptop even).
Still laughing though that I can search for NoL and get a ton of a results in this thread!
Im wondering now, if i go ahead with this project what standards will it have to adhear(sp?) to?
The current standards of your government, basically it doesnt leak (much) and its not a fire hazard and what not.
And my teacher has kindly informed me that we arn't allowed to test and fill the thing on site. So is there anywhere i could send it to have it certified?
Dunno about your country, but generally an HVAC shop could do the filling. But even then, they probably won't let you in the door with a homemade unit since its a huge liability!
Lastly, is it worth the effort? Is it hard/costly to get the parts in the UK?
Worth the effort, if your chip doesnt have a coldbug, YES IT IS! (I love phase) but it can also be hard/costly to get the parts anywhere if you don't want to pay HUGE retail pricing. (ebay is a wonderful place)
The parts to build a phase are actually quite inexpensive and rather easy to get. You can get all of the parts required to build your own unit for about $300 your first go around (since you need to buy all of the tools and get a vacuum pump or make your own from a compressor). After that if you build more you can get all of the required parts for about $200-$250. This is if you build your own evap, it will be a bit more expensive if you buy a premade evap such as a chilly1 which runs about $100.
Sorry Frag, gotta go against this. In the USA with ebay thats possible. Though chilly1 evap is bout $110 unbrazed without anything but the copper mass. Building your own evap can also be like a $10-15 affair.
As for tools im pretty sure ive got everything id ever need at home/school. Vac pumps can be 'aquired' form the chemistry dpt.
Lots of those so called vacuum pumps, are just air pumps and won't do the job very well.
Is it diffiuclt to build the evap?
Nope but it can be dangerous
And exactly what kind of compressor am i looking for? or are they all smilialr?
They are all quite different! I'd say get a reciprocating for your project, a Danfoss if you could.
guys what about the compresser out of the back of a fridge? i think theres a few around
Bad idea, the compressor would be HUGELY undersized. Fridges use tiny compressors in the 1/10hp range becuase they really dont deal with a heat load.
The evap would be the hardest part of the project to build if that's the route you decide to take. NoL can show you how to build a very nice and very simple cap in cap evap. I was hoping that he would have already replied to this thread, I'll point him here next time I see him on. There's a lot of purging that has to be done when making an evap and such.
This involves my two favorite substances, propane and copper. Maybe I'll make a guide?
How difficult is filling?
Easy for a single stage, simply vacuum, purge, vacuum, purge, vacuum, static charge to 80 PSI or so, turn on the unit and add more charge thru the suction side unless its a r4** series gas then you need to liquid charge.
Also what kind of tubing do i need for the fliex line? Im guessing not copper and a plastic that wont freeze?
It's called stainless steel flex, sometimes used in gas lines. Its a bit hard to braze to so I suggest buying a pre-made flex. It does not have to be braided in a single stage unit.
You could get a compressor from a fridge, but your best bet is to knick one from an air conditioning unit, like a window mount. Those usually have a substantially sized compressor for the job. You can even use the condensor as well, but they're pretty big so it may not fit in with what you're trying to do..
Yes indeed, but generally those compressors will be rotary's.
The flex line is a stainless metal braided hose.
Not always braided as I said 2 pops up.
However i cant find anything that gives me a basic diagram of a very basic evap that shows more how they work, have i overlooked somthing?
Liquid enters the evaporator, and changes from a hige pressure zone to a low pressure zone. It evaporates and removes heat from the surrounding area to do so. Thus the evaporator gets cold as the gas
evaporates and then the gas is sucked back to the compressor.
So your evaporator needs space for evaporation, but its not instant so you want to make it "long" enough of a trail to make as much of the liquid evaporate in the evap and not in the suction or compressor as possible.
Next hurdle is the coolent. Frion is illegal here so what else can i use? Propane, butane, ethanol?
Propane and just abotu any other gas can be used, but not always in a single stage.
Also what kind of pressures are we looking at?
Generally our high side pressures are between 150 and 300 psi. Our lows are generally between -10 and 10. Not really a lot of pressure when you think about it.
I only want this to cool to fairly low temps if the product goes ahead. id be happy with anything sub-0.
Have you considered doing a liquid chiller? This would require just a copper spiral of tubing inside a resevoir of a liquid. An a/c could be modded to do this without any regassing.
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