Tank Design According to Temperature

[Scouse]

Is there a specific calculation you can use to ensure you have the right glass or acrylic thickness to prevent condensation on coldwater tanks?

Thinking for instance if a tank was to be say 14 degrees it would be blarddy blah and if 18 degrees blarddy blah..?

Cheers

 

[monty]

Is there a specific calculation you can use to ensure you have the right glass or acrylic thickness to prevent condensation on coldwater tanks?

Thinking for instance if a tank was to be say 14 degrees it would be blarddy blah and if 18 degrees blarddy blah..?

Cheers

I'd think it'd have to take into account the humidity in the air and the air temperature, too... But I have no idea about the exact formula.

 

[DHyslop]

I've never seen anyone do a calculation because I don't think I've heard of anyone chilling a home aquarium quite that much (?). If you're worried about it you might want to go acrylic just to be safe.

Dan

 

[Scouse]

Monty said:-

I'd think it'd have to take into account the humidity in the air and the air temperature, too... But I have no idea about the exact formula.

Good point actually!! Ahh what a nugget I am!! Just realised it would prob be the building calculation for interstial condensation...hmm that means you would need the thermal properties of acrylic, glass should be able to get.

Ahh dunno surley theres something online.....

Dan do you think there is less chance with acrylic of condensation than for say glass of the same thickness? Greater thermal properties?

Doesnt acrylic scratch easily?

 

[Feelers]

I think acrylic has better insulating properties (perhaps around twice as much? from memory) compared to glass. It does scratch easily - you can remove the scratches, but its a hassle.

 

[joefish84]

use a double layered acrylic tank and you wont have to worry cause the air pocket between the two will balance out the condensation with the humidity and you wont have any foggin or condensation on your tank thats how most of the public aquariums used to do theirs so they wouldnt have to worry about temp. fluxes inside the building causing massive condensation build up

 

[TidePool Geek]

Is there a specific calculation you can use to ensure you have the right glass or acrylic thickness to prevent condensation on coldwater tanks?

Hi Scouse,

I don't think you need to worry about it too much. If your tank is significantly below room temperature glass will sweat and acrylic won't.

I volunteer at a marine center in the NW United States. Our water is pumped directly from the sea and ranges from 9C to 11C. We have both glass and acrylic tanks with various wall thicknesses. On even the hottest, most humid days our acrylic tanks don't sweat. OTOH: Our glass tanks start to sweat anytime the ambient temp rises above 15C or so. In mid-summer our glass tank displays will be obscured within 5 minutes of being dried off.

Of course, acrylic is far more scratch prone. One idea I had for a planned cold water tank was to build it with a glass viewing window spec'd according to tank dimensions and with another sheet of thinner glass on the outside enclosing a dead space that would be filled with helium. Filling the void with gas should eliminate the moisture from which condensation arises. I'm planning on using helium because it's easily available compared to other inert gasses like argon.

If you're planning a cold water set-up, you might want to consider building the tank out of plywood with only one viewing surface. You can get an idea of what's involved here: http://www.garf.org/ (sorry I can't give a more precise URL - Look for articles about 500gallon tanks). Essentially, you'll enjoy lower material costs and improved insulation leading to less expense for a chiller and the electricity to run it.

Frugally yours,

Alex

 

[DHyslop]

Here is a definitive resource if you're interested in a plywood tank:

A first plywood project

Dan

 

[monty]

Of course, acrylic is far more scratch prone. One idea I had for a planned cold water tank was to build it with a glass viewing window spec'd according to tank dimensions and with another sheet of thinner glass on the outside enclosing a dead space that would be filled with helium. Filling the void with gas should eliminate the moisture from which condensation arises. I'm planning on using helium because it's easily available compared to other inert gasses like argon.

Why is it useful for the gas to be chemically inert? Wouldn't dry air be just as good? My gut reaction is that it'd be easier to put air in with a little dessicant, like those (silica?) crystals they often put in packed products that shouldn't be too exposed to moisture. Also, if it's just air, it doesn't matter if there are small leaks, beause if a bit of water vapor leaks in, the dessicant will take care of it-- you can just make it "mostly" sealed as opposed to hermetically, so probably just some caulk is sufficient...

If making it chemically inert is useful, plain nitrogen is worth considering, too-- it's not a noble gas, but it's pretty darned unreactive, and it's not nearly as prone to leaking out... I guess either He or N2 is dirt cheap, though, so there's not much of a tradeoff. I'm used to thinking of He as prone to leakage since it's such a small molecule (atom, really), but I guess it's only at atmospheric pressure, so there's not much gradient across the seals.

 

[DHyslop]

Dry nitrogen is used in aviation tires, so if you know someone at a local airport you might be able to get your hands on some if you have a way to transport it.

To be honest, I think it would be a lot easier to just go acrylic. Condensation is a symptom of a bigger problem: too much heat flux through the glass. Making the viewing side double-paned is only a band-aid fix. If you're chilling a tank you're paying $ for each drop of condensation that forms.

Dan

 

[monty]

Dry nitrogen is used in aviation tires, so if you know someone at a local airport you might be able to get your hands on some if you have a way to transport it.

To be honest, I think it would be a lot easier to just go acrylic. Condensation is a symptom of a bigger problem: too much heat flux through the glass. Making the viewing side double-paned is only a band-aid fix. If you're chilling a tank you're paying $ for each drop of condensation that forms.

Dan

Yeah, but air (or any gas, or vaccum) is a great insulator, so the double-paned version, in addition to providing dryness to avoid condensation, would almost certainly cause less heat (or cooling, if you will) loss than a single pane of anything. That's why double-pane windows are considered desirable for insulating your house... (I'm not sure what advantage the "triple-pane" ones provide over just double; I suspect it's a marketing ploy)

 

[DHyslop]

Yeah, but air (or any gas, or vaccum) is a great insulator, so the double-paned version, in addition to providing dryness to avoid condensation, would almost certainly cause less heat (or cooling, if you will) loss than a single pane of anything. That's why double-pane windows are considered desirable for insulating your house... (I'm not sure what advantage the "triple-pane" ones provide over just double; I suspect it's a marketing ploy)

AFAIK acrylic has something like 3 or 4 times less thermal conductivity than glass. I don't understand why someone would go to all the trouble of building an elaborate "tank-within-a-tank," seal it, then somehow pump in a dry gas, when they could just go buy an acrylic tank.

If you don't care about three of the side-panes, you could just put some insulating foam over them. At that point you might as well build a plywood tank.

Dan

 

[monty]

AFAIK acrylic has something like 3 or 4 times less thermal conductivity than glass. I don't understand why someone would go to all the trouble of building an elaborate "tank-within-a-tank," seal it, then somehow pump in a dry gas, when they could just go buy an acrylic tank.

If you don't care about three of the side-panes, you could just put some insulating foam over them. At that point you might as well build a plywood tank.

Dan

Yeah, and I guess if acrylic is known to be "good enough" for both insulation and non-condensation, the double-paned thing is a lot of effort for almost no benefit... I'm guessing air conducts heat at < 50% of acrylic, but half of "almost nothing" is still "almost nothing" in most applications...

 

[AquaticEngineer]

http://www.dpcalc.org/

You can use this calculator to find the dewpoint for your environmental conditions.

Set the Temperature slider to the temp of you tank, and then adjust the relative humidity slider and it will tell you on the what temp condensation will occur at.

Dual paned tanks are the best for insulation, but the most hassle. Thick acrylic is the way to go, but expensive.