Homemade refrigerated air dryer?

[SecondMonkey]

I have a little hotel sized fridge that works fine, however the door seal is bad and the hinges are coming off. I was thinking of taking it down to my shop, and make a new door out of plywood and foam insulation, and, inside run several lengths of 1/2" copper pipe with appropriate water traps at the bottom. Then I could run all my hot, wet compressed air though it and hopefully get dry air on the other side?

I know that's basically how industrial refrigerated air driers work, but would a small fridge like that be able to keep up with all that hot air? Maybe it would work better if I used something like an automotive heater core instead of copper pipe? Or maybe I could just go with a full sized fridge - there's no shortage of old free ones on craigslist.

Anybody ever try that before?

 

[tom slick]

how are you going to seal it up?

 

[SecondMonkey]

You mean the pipes through the fridge? I'd probably attach all the inputs/outputs through the new door I'd have to build and seal around them with that expanding foam that comes in a can. Otherwise I could probably drill through the top of the fridge and do the same thing, as long as I don't hit any refrigerant lines.

I guess it would be sort of like a "keggerator". (except without the fun)

 

[JTK]

I don't think you'd have enough capacity in that fridge for proper heat exchange through the copper tubing. An aluminum heat exchanger and lower airflow might work.

Joel

 

[tom slick]

I figured out your plan, disregard my previous post. Sounds like it is a good project to tinker with. I think you'd probably want to use large tubing so the air spend some time in the cold area as it flows through. Too much tubing will cut down flow significantly.

 

[SecondMonkey]

Does anybody have any idea how many BTUs a small refrigerated air drier would be rated for, and how many a small fridge would be rated for?

I'm starting to think maybe I could keep ~5 gallons of water in the fridge to act as sort of a "cold reservoir", and run the air pipes through that. Obviously it wouldn't be continuous duty for a long time like some sort of industrial machine...

If it doesn't work I can always take out the pipes and fill it with beer.

 

[benjamming]

How many cfm?
Have any Freon around so you can get really cold & substantially decrease the residence time?

 

[SecondMonkey]

Originally Posted By: benjamming
How many cfm?

I have no idea really, but I have four seperate compressors that probably come to 4-5 CFM each, I want to plumb the output of each compressor directly to the fridge. From there I want it to be dry and stored in my 125 PSI tanks, where it is taken out by yet another compressor (used to be an air conditioner!) and stored in propane tanks at 250 PSI. I just got a big huge old round 250 gallon propane tank I'm going to use for air storage, this thing looks like some sort of Russian space capsule.

Originally Posted By: benjamming
Have any Freon around so you can get really cold & substantially decrease the residence time?

No, but I hear ebay has some

What would I be doing with it though, adding it to the fridge?

And yes, my air system is over complicated and rediculous, but I like it that way.

 

[benjamming]

You could use the freon to make a heat exchanger.

 

[SecondMonkey]

My my, how quickly things change. I think my neighbor got arressted...his shop has just become available overnight. Anyway there's a creek right out back with plenty of cold water so I might just move there and run a heat exchanger down to the creek.

 

[wapacz]

Originally Posted By: SecondMonkey
My my, how quickly things change. I think my neighbor got arressted...his shop has just become available overnight. Anyway there's a creek right out back with plenty of cold water so I might just move there and run a heat exchanger down to the creek.

count down until the cops stop by thinking your running a moonshine operation.

 

[labman]

No electric usage.

If you still go with the fridge, you could get a rough idea of the fridge vs industrial dryer capacity by looking at the power draw.

I doubt the creek will keep your beer that cold.

 

[Carbon]

Automobile heater cores and radiators are not designed to handle 100 PSI. They are more like 15 PSI. Maybe they will do it.... but I guess I would want to overpressure test them.

For the fridge, used big fridges are often cheap. More room for the piping to serve as your heat exchanger. Even steel pipes should act as a good enough heat exchanger if you have enough length I expect. The ability to keep the fridge insides cool enough is going to be more of a problem than exchanging the heat IMHO.

You will want a petcock to drain water at each low point.

 

[benjamming]

Is this a combo fridge/freezer or simply a fridge. I had assumed a combo, but I don't think it is after reading again.

 

[SecondMonkey]

Originally Posted By: Carbon
Automobile heater cores and radiators are not designed to handle 100 PSI. They are more like 15 PSI. Maybe they will do it.... but I guess I would want to overpressure test them.

Probably right...maybe an AC evaporator core would be better.

Originally Posted By: benjamming
Is this a combo fridge/freezer or simply a fridge. I had assumed a combo, but I don't think it is after reading again.

It's a combo, but the "freezer" is just a little sectioned off area in the corner of the fridge. After the door seal started leaking it started acting like a dehumidifier, and the freezer would literally freeze solid.

That's why I wanted to use this little fridge in the first place, it seems to run well under continuous duty use.

 

[Dualie]

sounds like your making a bomb to me. DO NOT underestimate the amount of kinetic energy involved in storing large amounts of compressed air.

You plan sounds like a Darwin award in the making.

 

[SecondMonkey]

Originally Posted By: Dualie
sounds like your making a bomb to me. DO NOT underestimate the amount of kinetic energy involved in storing large amounts of compressed air.

You plan sounds like a Darwin award in the making.


You clearly do not understand compressed air systems as well as I do. Just because it's a bit unusual does not in any way make it a "bomb".

If you think a propane tank full of air is dangerous how dangerous is it when it's actually full of propane? Do you happen to have any clue that propane tanks can withstand about 4 times the pressure of a standard air tank?

 

[ac_tc]

It will work..but the capacity will be limited.
You can expand it by cooling the incoming air with
the outgoing. Putting a bucket of water inside will be a good idea if the airconsumption is periodically. The heat exchanger
is crucial for the function, i like the idea of an ac condenser inside, also wound some tubing down in the bucket.
Cool the air toroughly before the drier.

 

[Dualie]

DO you understand how to properly purge a pressure vessel before welding? If you want to compare certifications i can battle. All im saying is 250 PSI in any pressure vessel is tremendous.

Can you tell me what the pressure relief valve is set at on a LPG storage tank of that size?

(I already know the answer to that question)

 

[SecondMonkey]

Originally Posted By: Dualie
DO you understand how to properly purge a pressure vessel before welding?

Certainly, but what does welding have to do with anything?

Originally Posted By: Dualie
All im saying is 250 PSI in any pressure vessel is tremendous.

It's a whole lot less dangerous than the same tank filled with propane. And I guess all those guys that use oxygen/acetylene/co2/argon/scuba tanks etc better go get all those 3000 PSI+ bombs out of their shops.

(have you seen the Mythbusters episode where they shot one of those tanks and almost nothing happened?)

Originally Posted By: Dualie
Can you tell me what the pressure relief valve is set at on a LPG storage tank of that size?

250 PSI. (with a BIG margin of error)