Common heat issues : some insite :)

[jansenwrasse]

Re: Re: Now Cooling!

Re: Re: Now Cooling!

<a href=showthread.php?s=&postid=12701761#post12701761 target=_blank>Originally posted</a> by redrider911
We don't force cooler air, we remove heat. If you want to get technical. And in your terms it would be conductive cooling because warm air is passing through a cold coil.

You are correct

The warm air goes through the coil by air movement then the Refrigerant takes it outside and is then again cooled by air movement. I am not an HVAC guy but It would seem that both mechanisms are in play. Would you agree?

I.E. : The old banister heaters use convective heating to heat a room, But touching the banister would be conductive.

 

[Paradiddle7]

Good point. That's another reason why it might be important to have a chiller for emergency usage.

<a href=showthread.php?s=&postid=12701588#post12701588 target=_blank>Originally posted</a> by EllieSuz
When the thunder storm rolled through last night and the lights flickered, I was struck that there is no way to hook up the central air to my generator. So, in the event of a power outage, what can be done?

 

[SkiFletch]

<a href=showthread.php?s=&postid=12701572#post12701572 target=_blank>Originally posted</a> by thriceanangel
I'm looking for some info on Specific heat and how that plays a part, seem pertinent in the AC question...

Some other questions:

Heat= IR... True or false?

Lighting effects on heat of the tank ie, if I cut my light cycle by an hours, how much heat build up will I lose?

My basement is cool but very humid... will I need to put AC in it?

Oooh oooh (raises hand) I know this one . Assuming your "cool" basement is like mine and most others in WNY, it's prolly down in the lower 60 farenheight range this time of year. And RH down there is likely ~60% without a fishtank in there. Now, placing a heated tank in the basement will raise the temperature of that basement probably up into the 70's. In doing so, the relative humidity will actually go down because warmer air can carry more water vapor. So you all of a sudden have more room for evaporative cooling and to answer your question, yes, the tank will stay cool.

It MAY require forced convection (fans) blowing across its surface or sump to help keep it cool during a lights on timeframe, but likely would be fine without any such measures during lights off. Here however you can run into a larger problem. In order to keep the tank cool, the walls of the basement will basically be your heat exchanger and will keep the temperture down. However the humidity is going to stay very high especially in the case of big tanks (think 180+ gallons). It can stay so high that as Jansenwrasse described, you can literally make the walls and ceiling sweat and precipitate. This becomes an exceptional problem at low temperatures because you can induce rotting of your floorboards... Many here with large basement tanks or sumps have noticed this problem and turned towards basement dehumidifiers and/or ventilation to keep things from getting too wet, so beware this need.

 

[SkiFletch]

My turn to add to this cooling discussion. I often see people suggesting using Ice to cool an overheating tank down. I always tell people that ice has a very low thermal mass compared with that of the aquarium and its use as a cooling device is exceptionally limited. In order to do this, I bring you back to Jansenwrasse saying that heat is a measure of energy in a system (in our case an aquarium). So I give you this problem: "How much energy will it take to cool a reef tank of 100gallons of water volume down 1 degree C?"

The answer is in the equation for specific heat capacity Q=mCp(deltaT) where Q is the energy required, m is the mass, Cp is the coefficient of specific heat, and deltaT is the change in degrees C. So, here we have a mass of ~378kg (since water weighs 1kg/L) or 378000 grams. Our Cp is a constant (4.18joules per gram degree c) and our desired delta T is just 1degree C. giving us the equation:

Q = 378000 * 4.18 * 1
Q = 1580040 joules
Q = 439 watt hours

or perhaps a measure most AC people might know, Q = 1498 btu

So now that we know how much heat energy is required to cool that mass of water, lets think of how much Ice it would take to do that. So here, the ice only has a coefficient of specific heat of 2.050 at -10C. And our delta T of the ice will be lets say 40C (-10 to 30)

Q = mCpDeltaT
1580040joules = m * 2.050 * 40
m = 19269 grams of ice
m = 19.269 kilograms of ice

Ice is slightly less dense than water so it needs to be multipled by 0.9150 to convert to liters...

So thats 17.63 liters of water or 4.66 GALLONS of ice. So someone who wants to cool an overheating 75 or 90g tank with a typical smaller sump by 1C would need 4-5 gallons of iced RO water to add at once. In my own recent case I would have needed to cool my tank 4C which would have cost me 15 gallons of iced RO water... Tough to figure out where I could get that in there

 

[jansenwrasse]

Fletch:

19269g of Ice is 42# ... little much, but here is what happened :

Your equations are correct but, you are changing water from one degree C to 0 degrees C, and the final degree is a tough one to get!

If you want to lower the temp from 85F to 80F it would take 9870g of ice or 21# of ice (same water volume)

As the temp increases it is easier to cool the water.
453.48g = 1 u.s. pound
1 Gallon of SOLID ice weighs 7.497#/Gallon (US)

 

[belgian_waffleman]

Jansenwrasse,

2) Get a nice box fan and blow this nice cool air over the largest open surface of water. Please don't place a box fan on the tank you are asking for trouble

Are you saying that if I lay my box fan on egg crate, flat over the sump, there will be trouble? Could you elaborate?


Waffleman

 

[jansenwrasse]

Electricity + high humidity could mean a electrical problem. It is best to have the fan off to the side blowing the air away from the water. Other than that the cooling would work, I just want people to be safe

 

[SkiFletch]

Knew things would get a little dicy with the whole pounds of ice thing :lol:. Still a lot of ice to cool down a tank.

 

[jansenwrasse]

For sure, Just shows that Ice is a terrible way to cool. And on top of it I don't know anyone who keeps that much Ro/Di frozen.

Sorry to hear about your heat problems Ski. I hope all is well!