Peltier cooling, cooling pump vs cooling water

[Navyblue]

I have a skimmer pump that would push my water from 28ºC (82ºF) to 31ºC (88ºF). The pump is currently run outside of the water and is hot to the touch. Total water volume is around 10G, which I believe is small enough to use peltier cooling.

Would it be more efficient to put the peltier element on the pump itself, instead of in the water with heat sink since the pump is pretty much the sole heat source? It is a good deal hotter than ambient which would make cooling more efficient. And the pump is solid so heat conduction would be more efficient.

On the other hand I can see he argument against it, since I would be cooling through the plastic casing, which wouldn't be efficient. And I wouldn't be able to cool the water past ambient, since cooling the pump itself to much lower than ambient seems impractical enough to be impossible, if not dangerous. That said I would be content if I can just bring the water temperature back to ambient.

 

[jamie1981]

This is on a 10 gallon tank? IMO a skimmer isn't necessary on a 10 gallon tank just do regular water changes. And if you nee to cool it just use a ice probe chiller. I think your over thinking it.

 

[Navyblue]

This is a DIY forum, I am thinking of building a pelting cooler, I am asking where should I place it for optimal efficiency, how is it over thinking?

 

[jamie1981]

Wowa What I am saying is that for a 10 gallon IMO a skimmer is not necessary which would make trying to figure out how to cool a skimmer pump also unnecessary.

To answer your question you would be best cooling the water directly not the pump (assuming the pump is designed to run at the temperature it is) because you will still get the benefit of natural air cooling around the pump PLUS the pelter cooling the water directly. Your going to be using electricity to remove heat some of which would naturally dissipate around the pump on it's own anyway. Your pump is going to generate the same BTU's of heat regardless if you are cooling it directly or indirectly.

 

[Navyblue]

Peltier cooling, cooling pump vs cooling water

There are those who grow corals in a jar with next to no equipment and just rely on tonnes of water changes, but that is not my idea of fun.

While the pump will generate the same amount of heat, increasing ambient cooling will result in less heat transfer to the water. And while the heat will dissipate anyway, the rate of dissipation will be different.

First law of thermodynamics, the rate of heat transfer is proportional to delta T. At the pump itself is where delta T is the highest (and way higher than the water). Second highest delta T would be at the skimmer affluent, and in theory the slowest heat transfer occurs when the heat exchanger is placed everywhere else in the water.

But the catch is, the flow rate of skimmer affluent is fixed , where as else where in the tank it could be higher and potentially increasing the rate of thermal exchange. If I were to use a water block, I also won't be able to use a large pump for the task.

Of course I am no expert in thermodynamic, I am hoping to hear from the expert.

 

[jamie1981]

But we don't care how hot the skimmer pump is in this situation. Were only concerned with the tank water temperature.

Never seen anyone try to cool a small skimmer pump with a thermal electric chiller. That is probably consuming more power that the pump it's trying to cool is, just doesn't seem necessary IMO

If your looking for the most efficient (and cost effective) way to cool the tank use a small fan blowing across the surface of the water.

But good luck with it...

 

[Navyblue]

In my climate, we care how hot every single piece of equipment is in the tank because that is what decides our tank temperature, and yes we are no stranger to fan cooling.

 

[perkint]

The actual calculations to work out which is best are probably scarilly complex. You are both right. The pump will dissipate heat better than the water due to the higher temp differential. But the water temp is the thing you care about. Not sure about the efficiencies (with respect to Watts per °C) of a peltier cooler (probably pretty rubbish, same as any other direct cooling). Most efficient is probably evaporative cooling, but not sure.

Try both and take some measurements

Tim

 

[Gorgok]

I don't think the difference of the temp between the water outlet of a pump running and across the tank will be significant enough to really care in this case... While water isn't good at conducting heat you are moving it so much convection will disperse it pretty quick.

 

[Legot]

A pretty safe estimate is that you'll need a 100w peltier to cool 10 gallons of water 5F in a reasonable amount of time with absolutely minimal heat dumped into the tank. Since you're dumping a good amount of heat into the tank and you need to cool more than 5F bump it up to a 300W peltier and you'll be good as long as it's cooled well.

The most thermally conductive metal that would be reef safe is aluminum, either as a heat sink attached to the cold side inserted into the tank, or a waterblock/heatsink combo inserted into the tank. Aluminum, especially if its anodized, will be safe in a reef tank as long as the pH stays above 5 or so.

 

[Navyblue]

Thanks guys for the info.

 

[Windy2]

Get a more efficient pump. Your pump is generating heat and now you are going to find a way to cool it. What a waste of energy and time.

 

[RocketEngineer]

Do you have an ATO and if so have you tried evaporative cooling? You would be amazed at how effective a fan blowing across the surface of the water can be at dropping the temperature of a tank.

 

[Navyblue]

I used to do fan cooling in the MH days, which was non optional and switched to a compressor chiller later on. But now I downsized to a small tank and sold my chiller. My guess is I will run a fan regardless I build this peltier cooler or not. I still have FW tank that is fan cooled but salinity is no issue there.

 

[ReefWreak]

I saw your comment/post in the nano forum too. Have you seen this peltier cooler? You just would have to drill your tank (or they make one already installed in an HOB filter).

 

[Navyblue]

I have not physically seen it but I have heard of it. Thanks.

 

[zachts]

I would say, one your skimmer/pump is too large for the tank, that not withstanding maybe there is a need for it, heck I've got a sebae nem that fills a ten gallon, skimmer absolutely required.

I would however try fan cooling the pump first, a small pc fan should be pretty much silent and be able to keep the pump body at near ambient significantly reducing heat transferred to the tank, that combined with an ATO and some added evaporation cooling should be all you need for a ten gallon to keep it easily at ambient temperature or even a degree or two below.

 

[Navyblue]

I actually considered sticking a CPU heatsink on the pump. I found the heat is concentrated on top of the pump behind the outlet. While the bottom isn't nearly as warm. But just the fan without the heatsink would probably work as well.

That is if I keep the pump or the skimmer, I am having a hard time coming to term with replacing a German made product that had worked well for me for a long time for me with a Chinese made one. The world seems to have changed.