Wine-O-Dor tweaking

[B.HOBS]

Hey all. Hope someone can help me out here.

My custom wine-o-dor fridge died on me awhile back. After buying a replacement unit that ended up being too small for my custom trays, I just swapped the new peltier unit and PCB into the old unit. Now I'm good to go, and all is cooling perfectly. I have a Ranco temp controller on its way from Bill Baker, which will help me out even further in terms of controlling temps.

SO heres where I start over-analyzing the setup. I want this unit to cycle as little as possible to prevent the 10-15% drop in RH that cycling creates. In order to do this, the humidor would need to insulate well enough to maintain that temp or stay within the differential set on the temp controller, over a period of time. Being a wine cooler/fridge, it is already fairly well insulated as it is. But...plastic, cigars, and wood are very poor thermo conductors relative to other materials, say copper or aluminum. My idea, which I am not sure will work(this is where the smart people come in), would be to install decent sized aluminum "coldsinks" evenly within the humidor to help maintain that specified temp. The aluminum would hold that cold temp longer than the cedar or plastic, but would it be effective enough to help maintain the fridge at that specified temp, or would I be wasting my time without any forced air over the coldsinks?

In short, I would hope this modification would passively help maintain the air temp inside when the unit is not cycling. I am not expecting it to have a long term effect, just prolong the period between cycles. Any help would be much appreciated. Thanks for reading everyone!!!

~Billy

 

[SamuraiJack]

I had a similar idea. To avoid buying a wine cooler I was thinking of keeping my humi near an AC vent in something that retains some coolness.

 

[Ginseng]

But...plastic, cigars, and wood are very poor thermo conductors relative to other materials, say copper or aluminum. My idea, which I am not sure will work(this is where the smart people come in), would be to install decent sized aluminum "coldsinks" evenly within the humidor to help maintain that specified temp. The aluminum would hold that cold temp longer than the cedar or plastic, but would it be effective enough to help maintain the fridge at that specified temp, or would I be wasting my time without any forced air over the coldsinks?

In short, I would hope this modification would passively help maintain the air temp inside when the unit is not cycling. I am not expecting it to have a long term effect, just prolong the period between cycles. Any help would be much appreciated. Thanks for reading everyone!!!

~Billy

Billy,

First, I have to say that this is a really cool, novel idea. I love it!

Second, just to provide an engineering geek's clarification, the property of interest to you is not thermal conductivity but heat capacity. As you can read in this simple little page, either copper or aluminum would be ok. Basically it comes down to your particular balance between cost and volume of the chunk you can tolerate in your fridge. I will say that ingots or billets of aluminum are going to be a bunch cheaper than copper.

Third, you'd need to be concerned with condensation. I think you could cut this problem by wrapping the piece in some saran wrap or a heavy ziploc to prevent the direct contact of air with the surface.

Let us know how this works out.

BTW, the calculations to figure out how much the additional thermal mass would slow down warming up are pretty straightforward. Alas, it has been a ton of years since I've done them.

Wilkey

 

[B.HOBS]

But...plastic, cigars, and wood are very poor thermo conductors relative to other materials, say copper or aluminum. My idea, which I am not sure will work(this is where the smart people come in), would be to install decent sized aluminum "coldsinks" evenly within the humidor to help maintain that specified temp. The aluminum would hold that cold temp longer than the cedar or plastic, but would it be effective enough to help maintain the fridge at that specified temp, or would I be wasting my time without any forced air over the coldsinks?

In short, I would hope this modification would passively help maintain the air temp inside when the unit is not cycling. I am not expecting it to have a long term effect, just prolong the period between cycles. Any help would be much appreciated. Thanks for reading everyone!!!

~Billy

Billy,

First, I have to say that this is a really cool, novel idea. I love it!

Second, just to provide an engineering geek's clarification, the property of interest to you is not thermal conductivity but heat capacity. As you can read in this simple little page, either copper or aluminum would be ok. Basically it comes down to your particular balance between cost and volume of the chunk you can tolerate in your fridge. I will say that ingots or billets of aluminum are going to be a bunch cheaper than copper.

Third, you'd need to be concerned with condensation. I think you could cut this problem by wrapping the piece in some saran wrap or a heavy ziploc to prevent the direct contact of air with the surface.

Let us know how this works out.

BTW, the calculations to figure out how much the additional thermal mass would slow down warming up are pretty straightforward. Alas, it has been a ton of years since I've done them.

Wilkey

Thank you, Wilkey. I appreciate your input greatly!

The one thing I am becoming skeptical about, is the sinks being effective at all if there is no movement of air over the aluminum/copper. I would like to think that it would passively cool the unit if it was a large enough chunk of material, but I haven't such room for a large piece of aluminum. This would be several smaller pieces dispersed throughout the humidor to try and balance the output of the coldsinks throughout, which makes me doubt they would be as effective as I want after thinking this through. Also, without being supercooled before the unit turns off, I'm not sure they would put out a noticeable amount of cold to make the unit any cooler.

I'm not sure if this is even worthwhile trying, as I think more and more about it. It seems the thermal mass of the aluminum coldsinks would not be great enough to offset the ambient air without being super cooled or having movement of air over the blocks. I guess what I'm hoping is it would act exactly like a peltier junction, but passively. AIN'T GONNA HAPPEN, unfortunately.
:whistling:

I will think about it some more and do a little more research.

~Billy

 

[Ginseng]

Thank you, Wilkey. I appreciate your input greatly!

The one thing I am becoming skeptical about, is the sinks being effective at all if there is no movement of air over the aluminum/copper. I would like to think that it would passively cool the unit if it was a large enough chunk of material, but I haven't such room for a large piece of aluminum. This would be several smaller pieces dispersed throughout the humidor to try and balance the output of the coldsinks throughout, which makes me doubt they would be as effective as I want after thinking this through. Also, without being supercooled before the unit turns off, I'm not sure they would put out a noticeable amount of cold to make the unit any cooler.

I'm not sure if this is even worthwhile trying, as I think more and more about it. It seems the thermal mass of the aluminum coldsinks would not be great enough to offset the ambient air without being super cooled or having movement of air over the blocks. I guess what I'm hoping is it would act exactly like a peltier junction, but passively. AIN'T GONNA HAPPEN, unfortunately.
:whistling:

I will think about it some more and do a little more research.

~Billy

Hi Billy,

I think your misgivings about the overall effect have merit. From an engineering perspective, there is no doubt that the extra thermal mass will serve to keep things cooler longer, however, the practical questions are how big will the effect be and will it make a sensible difference to you sufficient to offset the space the chunks take up.

I would like to offer a conceptual clarification. Cold is not something that is produced or output. Heat is energy and it is extracted to make things colder and added to make things warmer. Your point about the pieces not being supercooled is astute indeed. Lack of subcooling will reduce the effect of the chunks.

In the final analysis, I think this idea, while intriguing, may fail on practical considerations.

Wilkey

 

[bimmer635csi]

If you run a humidification device that uses a large water tank, the water would serve the same effect.

I forget the exact numbers, but liquid water is orders of magnitude higher conductivity and heat capacity than air. This is why when you swim in a 70 degree pool of water, you get cold, but in 70 degree air you feel dandy.

Also, assuming a perfectly sealed humidor (which is a bit of a stretch), no matter what you do, when you cool the air, the RH will go up. This is because water vapor is less soluble in cold air. This is how fog is made on cool mornings and the fog goes away when the sun comes out and heats the air up.

So, I guess the short summary: Try a 1 quart jug of water. Sealed if you are using another humidification method, or open and kept filled if you are using it to humidify your unit.


Hope that helps a little.

Cheers,
Chris

 

[Ginseng]

A quart jug of water will take up quite a bit more space than a piece of either metal though. The heat capacity is about twice that of water.

Your observation about the relative humidity makes sense though, however, with cigars and boxes in the humidor, the excess humidity will be taken up by the goods. And if temperature varies by no more than +/- 10 degrees from 65F, the RH swing will probably be minimal.

Wilkey

 

[rectifythis]

I've been thinking about actually putting 4 bottles of wine in my 2nd wine cooler (who would've thought!) To buffer the cold. What got me thinking on this was the fact that they tell you to put liquids in an empty refrigerator to keep it from constantly cycling on.

 

[Boomer52]

I'm no rocket scientist, but wouldn't the unit run much longer when it did cycle on? When the interior of the unit does warm enough to cycle on, there will be more heat to remove due to the additional mass thus causing a longer run time and longer run time would cause more condensation on the cooling element and lower RH even more than without the metal mass. Wouldn't this defeat the purpose? Am I making sense here?