Yeah I dont see why not.
I use a solenoid so it will be automatic and stay open until the liquid line reaches a preset temperature.
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Yeah I dont see why not.
I use a solenoid so it will be automatic and stay open until the liquid line reaches a preset temperature.
I was wondering if you guys can tell me what is a reasonable price for R23. I was quoted this by one company;
Trifluoromethane CHF3 (R23)
Content : 12 kgs
Pressure (bar) : 41.8 bar
Valve Outlet : BS341 No 6
Price : £320.00
Cylinder Rental : £5.70 per cylinder per month
Delivery Charge £25.95
All pricing is subject to VAT at 17.5%
Unfortunatly they didn't offer refunds on unused gas, so i would have to pay out for the 12kg which I really dont want to do. Is it common to rent cylinders, use the gas you want, return them and just pay rental costs and the price of the gas you used? As I have no experience with buying bottled gas in cylinders of such size.
my metering device for both stages in my autocascade are just ball valves. With all the stuff i am finding out about autocascades, there is little hope of making them anywhere near the size of a promy. i will do a little report for you guys once my research is complete.
in all my autocascade books the heatexchangers are all refered to as heatexchangers. When aenigma and i talk about our autocascades it is very difficult to keep up. i mean, when i say " liquid line temp at outlet of heat exchanger for the second stage" its a real mouthfull.
Welcome to flavor country boys.
why not build a regular cascade first, just to get the feel of dealing with high pressure gas? just my 2 cents.
I suppose I could, but I feel that an autocascade would be slightly more compact with its 1 compressor and I am doing all this work in my bedroom. I dont have much work space :) Also I feel it would be easier to construct the autocascade than the classic cascade, although it may be harder to get it running which I dont mind.
I did some sums to get an idea of what the heat loads would be like across the different components in the system. I used coolpack to get the properties of the refrigerants. I used these conditions as a basis to calculation:
Refrigerants: R23 and R290
High side pressure: 11bara (32ºC R290 and -27ºC R23 sat.)
Low side pressure: 1.5 bara (-32ºC R290 and -75ºC R23 sat.)
Evap. Heat Load: 150Watts
Condensor exit temp: 25ºC
Compressor Exit: 70ºC
R23 Subcooling: 8K
R290 superheat: 10K
The results:
Condensor Duty: 312Watts
Heat Exchanger Duty: 182 Watts
Suction Line HX Duty: 17 Watts
Evaporator Duty: 150 Watts
You can check out my calculations in Excel here:Autocascade and comment if you wish :)
sorry to sound arogant, but your in for a big suprise. autocascades are the very highest on the ladder of refrigeration. its not as easy as it looks.Quote:
Originally posted by Russell_hq
Also I feel it would be easier to construct the autocascade than the classic cascade
good luck:toast: :toast:
Dont worry about it, I realise that somethings are harder to do than others :)
I only have one good compressor, and I dont want to have to hunt for another one, thats just me. The way I see it with the autocascade I will be building one system as apposed to 2 with the classic cascade. I think that oil return problems with autocascade will not be as big a problem compared to classic cascade, I could be wrong.
All I have to do for the autocascade is build the phase separator, looks easy enough, and build the heat exchanger. Building a co-axial doesnt look that difficult. The rest is just piping. Which is all doable.
How hard can it be, braze it all together. Pump in some refrigerant and away you go. ;)
As I have stated previously, I have never seen an autocascade, much less worked on one, but I will add my two cents, nonetheless. :D
It seems to me that the key is the phase separator. I would build a parallel (as opposed to serpentine) condenser, and use it for both condensing and phase separation. I can see where there would be natural separation in a condenser. Why not use it to advantage?
Actually, in my mind's eye, I can picture the entire system, including oil separator, as a tube within a tube within a tube within a tube, with tubes wrapped around it, and a fan on top. It works perfectly inside my head... LOL
Parallel like this?
http://www.russellpetrie.plus.com/im...e/parallel.bmp
Yup. And then add the high ressure refrigerant outlet at the right top of the thing.
Though I would probably start tapping off the high pressure refrigerant somewhat more down to reduce low pressure refrigerant vapour contaminating the high pressure vapour stream.
I would even use a regular serpentine condenser and replace some elbows with T-pieces.
I'd be worried that some of the uncondensed propane would run out the top with the R23.
Put the inlet center left, and outlets top and bottom, and you've got it. :D
That sounds like a plan gary :D
I've got a spare condensor that I can try it out on. This is it here, condensor , its got flat sides where I could drill into it, braze in some pipe and convert it to parallel flow
There is a huge drop in velocity, so the oil is going to drop out and travel with the liquid out the bottom of the exit header. But we can make double sure of this by stuffing steel wool in the exit header.
These arent too good... i had 2 of them and the first one leaked (brand new) and the second one isnt too good for our small systems and the gas tends to puddle there..
I've been using it on every system i've built and it works fine. Cools and condenses nicely.
Looks like i'm one stage closer. Just found a supplier for R23 for a reasonable price and quantity.
£70 for a 4.5kg returnable bottle with 6 month rental. I dont think I will get it cheaper than that.
Dont spose that supplier is able to supply small ammounts of R404a or R507 on the cheap Russell? :)
Its Dean & Wood . just give them a phone. You can also try phoning these folks, IDS. IDS They were willing to take a credit card order from me. Normally you need a trade account but if your in a rush then you might be able to pay by credit card. Just call the place at bristol and see what they can offer. If you are calling these trade places, tell them you are a new customer and you are in a rush for the refrigerant and ask if they take credit card payments. Other places you can try are HRP Online . Just phone them and see what they can offer.
I need some info on pipe bending. How do you guys construct your co-axial heat exchangers? Specifically how easy is it to get the small pipe inside the big pipe and bend them? If I want to make a tight coil, should I start by sliding the small pipe coil into the big pipe coil and then bend them around a former or bend them individually and then try and slide them together? What are your thoughs and experiences? Thanks. I'm going for 1/4" and 1/2" pipe. I was told that 3/8" would be a bit to small to try and run 1/4" inside it.
Also i dont have pipe bending tools, it will all be by hand :)
Got this today :)
http://www.russellpetrie.plus.com/im...ascade/R23.jpg
I've got it for 6 months so I better get started on this project :)
Well, when I'm trying to make a tight coil by hand. I first find a piece of thick walled piping about 80mm OD and coil my copper pipe around it. I'll heat it up with the gas touch as I go if need be.
Is that what you do when your putting a coil inside a coil?
I wanted to practice some brazing trying to connect 1/2" to 3/8" pipe. I took a small length of each and brazed them together. Then I cut the pipe, about a cm from end of 1/2" pipe, through the join to have a look inside. This is what I got.
Top of Pipe
http://www.russellpetrie.plus.com/im...g/brazing1.jpg
One Side
http://www.russellpetrie.plus.com/im...g/brazing2.jpg
Other Side
http://www.russellpetrie.plus.com/im...g/brazing3.jpg
As you can see there is a gap between the pipes, im wondering if I need to add more filler or the 3/8" pipe is too small to braze into a 1/2". What do you think?