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Old 12-19-2010, 07:47 AM
omerizm omerizm is offline
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Quote:
Originally Posted by GpsFrontier View Post
omerizm
Although for my situation I would be concerned with amount of electricity a refrigerator uses (even a small one). I am wondering if you built one like that, and if so how well it worked. How big the reservoir was, what the temp was before and after using it etc.. I have considered using such a refrigerator to cool nutrients, but modifying it in a different way. But as I mentioned the cost to run another refrigerator was the factor that led to me not even trying it. Especially the used older models that are most likely not even energy efficient.
Hello GPSFrontier,

No, to be honest I did not built this one, the only cooler I built and used was the one described in this thread, that I posted pictures of. And it was successful, I mean it did the job.

As you know I used the cool water coming from the evaporative cooling pads, circulating it through a coil that I inserted in the nutrient tank. Running costs are cheap with this setup, just an additional small aq. pump running. Now there is no apparent reason for a "modified dorm fridge cooler" not to work, it most certainly will, but as you said it will be much more expensive to run. Actually I guess "modified dorm fridge coolers" will be more effective than most commercial chillers because they use more powerful compressors. What really matters here is the power of the compressor.

If you are concerned about the running costs, I would suggest that you stay away from all kinds of vapor compression refrigeration units. The most efficient refrigiration cycles in the world are about 60% efficient. (cooling power/electricity used). And most commercially available units are between 40%-50% efficient.

To raise the temperature of 1gr of water by 1 degrees, you need 1 calorie. 1 calorie = 4.18 joules and 1 watt = 1 joules per second. Now if you know how many liters of water you need to cool in a certain amount of time and the temperature difference required, you can easily calculate the cooling power. Divide this by 0.6 and there you have the power of the most efficient cooler that will get the job done. If this is too much for you, than no vapor compression refrigeration unit is suitable.

I suggest you try to use some kind of evaporative cooling, or even better, use some kind of heat sink such as the earth and run your solution through it. Or as I did you can use an already available source of cool water and run it in your reservoir.

Evaporative cooling requires much less power than compressive ref. coolers. I guess a counterflow chiller of closed type will be suitable for NS cooling.

Cheers
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