Filling Tanks - How Hot is Too Hot?

[captain]

One factor I've not seen mentioned is agitating the water to increase thermal cooling.

Anyone that doubts the effectiveness in cooling a block of aluminum or steel with water, I suggest draining the coolant from your car and seeing how far you can drive before your engine overheats. Bet you won't get far...

If you didn't notice look back at my system, it provides a continious flow of cool water up the sides of the tank.

 

[pescador775]

Captain, it was hard to miss. Nice setup.

 

[Web Monkey]

When I fill my steel 77s, steel 100s and aluminum 80s, I notice that the tanks (cylinders) heat up very quickly regardless of whether I'm filling Nitrox or just air, especially as they get more and more full. I expect a certain amount of heat from them, but have been wondering how hot they are actually supposed to get when being filled at such a slow r

First, I don't own a SCUBA compressor, however I did spend about 15 years doing refrigeration and air conditioning.

I looked at the picture of the compressor on their website, and it doesn't appear to have any significant (any at all?) cooling coils after the last stage.

I'm guessing that the reason your tanks get hot is most likely because you're filling them with hot air. Can you hold your hand on the connection from the compressor to your fill whip?

If you bank the air, it generally has time to cool down to ambient. If you're filling directly, the SCUBA tank will get almost as hot as the compressor outlet.

Terry

 

[dannobee]

BTW, the liquid cooled engine ultimately dumps all the heat into the air via the radiator.

Not quite accurate. The vast majority of the heat (~70%)goes out the tailpipe. A small percentage is radiated via various surfaces of the engine, ie, oil pan, valve covers, engine block, etc, even though the engine is liquid cooled.

If we could just recapture that heat that goes out the tailpipe, we'd solve a lot of the world's oil problems.

 

[Luis H]

My compressor is 3 to 3-/12 cfm depending on temperature and humidity. Usually in the summer air temps are in the mid 90's.
I use the setup pictured. It is a 26" length of 8" OD PVC pipe with a cap on one end. At the bottom is a connection for a garden hose and at the top are three 1" holes that allow the water to overflow and also act as finger holes to carry it. I turn on the water so there is a small amount overflowing the three holes while filling so there is a continous flow of cool water from botton to top.
As you can see there is no way the valve or filler can get below the water's surface.

I agree that this is an excellent set up for filling directly from a compressor. This is not the same as a quick fill situation.

As I mentioned above, with a longer fill external cooling becomes much more significant.

 

[Luis H]

Not quite accurate. The vast majority of the heat (~70%)goes out the tailpipe. A small percentage is radiated via various surfaces of the engine, ie, oil pan, valve covers, engine block, etc, even though the engine is liquid cooled.

If we could just recapture that heat that goes out the tailpipe, we'd solve a lot of the world's oil problems.

You are correct…I was mostly thinking and referring about the heat that goes into the liquid cooling system (since that is what we were referring to). I should have said that all the heat ends up in the surrounding air in one form or another.


Yes, we don’t have combined cycle cars like we have in some combined cycle power plants…to recapture some of the combustion waist heat.

 

[pescador775]

One of the bragging points made by Airtex is that their compressors have a couple miles of cooling tube. I don't know if the compressor in question has an after cooler but it should. I don't understand the origin of comments that compressors produce "hot" air. The air coming from my Capitano and DIY portable compressors exits the final filters at about room temp. All of these machines are equipped with after coolers and back pressure valves which cause heat of compression to be dissipated in the cooling coils and filters. People who decant from HP cascades can rightfully say that their gas does not heat up a scuba tank as much or as fast and that is due to the cooling effect of expanding gas. However, the heating effect of compression takes over as the SCUBA tank is being filled and thus the temp of the incoming gas should be secondary to the heat of compression by far. Compressor manufacturers would have us believe that their particular product produces cooler air and thus the SCUBA tank remains cooler during filling but really, such effects are minor compared to the physics of compression in the tank itself. Oh, there might be a ten degree difference in discharge temps between some types and some brands of compressors but what is that compared to an inevitable rise of some 70 degrees inside the SCUBA tank due to compression? The only thing that can handle that kind of spike is a water bath.

First, I don't own a SCUBA compressor, however I did spend about 15 years doing refrigeration and air conditioning.

I looked at the picture of the compressor on their website, and it doesn't appear to have any significant (any at all?) cooling coils after the last stage.

I'm guessing that the reason your tanks get hot is most likely because you're filling them with hot air. Can you hold your hand on the connection from the compressor to your fill whip?

If you bank the air, it generally has time to cool down to ambient. If you're filling directly, the SCUBA tank will get almost as hot as the compressor outlet.

Terry

 

[realdiver7]

Update on hot tanks.......I shortened my fresh air intake hose by about 6 feet and started pumping air from inside of my garage, which is cooler than the outside air. Since I'm starting the process with cooler air, the air going into my tanks is now warm like it should be instead of hot. My guess is that I was working the compressor too hard by having an air intake hose that was way too long, and this may have been a contributing factor to my problems.

In addition to the above, I installed a second whip to fill two tanks at once very slowly which also reduces heat build up. Even when using just one whip, my tanks are not heating up as bad as they were before.

Another change I made was to add double accumulator filter towers from Jim at Shelden Sporting Goods, Inc., which was an extremely good choice for extra filtration. I don't know if that had anything to do with having cooler tanks downstream, but I must be doing something right by making at least the first two changes.

Thanks!

 

[oxyhacker]

Not sure if we have just gone complete circle, but i am too lazy to reread the whole thread. But not sure what you mean by using air from inside a garage, but do be careful because air in houses and especially garages can get pretty contaminated, even without engines running. I would rather put up with warmer air than risk contaminated air.

Update on hot tanks.......I shortened my fresh air intake hose by about 6 feet and started pumping air from inside of my garage, which is cooler than the outside air.
Thanks!

 

[realdiver7]

Not sure if we have just gone complete circle, but i am too lazy to reread the whole thread. But not sure what you mean by using air from inside a garage, but do be careful because air in houses and especially garages can get pretty contaminated, even without engines running. I would rather put up with warmer air than risk contaminated air.

Oxyhacker...I appreciate the reminder and have thought of that myself. My compressor intake is just inside of my side garage door where a shelf-mounted fan blows fresh air from outside to the inside of the garage. When pumping air, the large two-door garage door is open and the side door next to the fan is open.

I'm going to keep a very close eye on CO levels with the new CO monitor I just ordered. I agree, if there is the slightest hint of problems, I will move my intake back outside.

Thanks!