However, I cannot find any information on how effective evaporative cooling is in an aquarium. Will the fans lower the temperature below the ambient room temperature? For example your house does not drop below 80 degrees will the fans be able to keep the aquarium at 78 degrees?
When are fans not enough and people should think about chillers to cool their aquariums?
Thanks.
Later,Adam
Your question is a complicated one (whether fans will be enough). Here is a bit of thermodynamic information to get you started:
Water's enthalpy of vaporization is 2260 kilojoules/kg water vaporized. This figure can be converted to watts if one knows or can estimate the rate of evaporation. For example, if one gallon evaporates in an 8 hour period, then using the above enthalpy of vaporization one obtains a rate of heat removal as 297 watts.
The rate of evaporation from the tank is a complex function of the relative humidity of the air that is blown across the tank, the surface area exposed to evaporation, the temperature of the tank water and the air, and the air flow rate. While engineering equations are available to estimate evaporative mass transfer given the value of these factors, the math is complex. It's far easier to do some empirical experiments - buy a cheap temperature/relative humidity indicator, set your fan to the preferred speed setting, and carefully measure the evaporation rate of your tank over a defined number of hours.
Generally speaking, "swamp cooling" is effective at relative humidities of less than about 50%. If you live in the southwest or western US, then evaporative cooling is probably all you need assuming you have the tank in a reasonably cool location.
For the Central Plains states, the South and the East Coast, the solution is more complicated. Temperatures in these locations can go well above 95 degrees
and have a dew point well in excess of 70 deg F. If the indoor air is not conditioned or only lightly conditioned, evaporation will be slow, and the relative humidity in the house/apartment will rise very quickly as tank water gets pumped into the air. Under these conditions, it's far less expensive to cool the room that the tank is in if it can be closed off than it is to run a chiller.
If the tank is over 100 gallons or so, the house is less than 2500 square feet and is relatively modern with good insulation and a high SEER central AC unit, it still may be less expensive to air condition the whole house and simply use evaporative cooling to cool the tank into the desired range.
But - if the tank is large (and so needs a big chiller), the house is over 2500 sq. ft., the tank has special heat gain considerations, such as metal halide lighting, an enclosed hood, is in sunlight part of the day or has a lot of high-wattage submersible pumps, then a chiller may be the least expensive and most reliable/controllable way of regulating tank temp. Ideally, the heat from the chiller should be vented outside or into a basement. But as long as the air in the room that the tank/chiller is in is well-mixed with the air in the rest of the house, a chiller will work very well.
Kidding..
