External Application Wine Cooler

[mikesado]

Hello all!

I am not in any way technologically savvy, I am actually a Pre-Medical student. Right now I am working on a microbiology project, and I am looking for a genius way (excluding a fan) to cool a 105 Quart container.

So I came up with this idea that maybe I could rig up a wine cooler and attach it to this 105 Qt. tub in order to cool it.

The ideal temperature for me is approximately 65F, or slightly cooler, and the room temperature is 75F. So I need to lower the temperature about 10F, and since this is definitely in the climate control range of a wine cooler it seems like a plausible idea.

MY QUESTION THEN:

What kind of wine cooler am I going to need to keep a 105 Qt. tub at 65F when room temp. is 75F? Is there some kind of electronic specification I need to be looking for? Like Watts, MHz, or will I just need to find a certain size such as a 9 wine bottle cooler? I figure you engineering specialists will know more than us doctors for this application :P

[PinkertonD]

Welcome to the forum. Yes there is a direct correlation between volume to cool and degrees of temperature drop per minute/hour/whatever.

There will be a coefficient of thermal conductivity to consider for the losses between inner and outer temps. Unless you have the perfect insulation, (not yet invented) there will be a small, but steady heat gain to compensate for.

Yes, you will need to ascertain a size to contain 105-Qt. That could range from a piece of 1" PVC pipe 14-feet long (internal volume 105-Qt) to a small cubic container that would contain 105-Qt. More importantly, what are you trying to contain? Is it a liquid you just pour into the "box" is it in some form of container? Are there multiple containers?

Converting an existing cooler wold be very difficult as you would need to bend and manipulate the evaporator coils and they are not built with that in mind.

If you can find an evaporator from a conventional refrigerator at will fit neatly inside the box YOU have designed to fit the contents, then you may be on the way.

This is not a trivial design project unless it is all theoretical.

Finally, MHz will almost certainly not figure into any of your design considerations.

Don't give up, but there is a ton of research you need to do to understand the refrigeration design and principles.

[mikesado]

Thank you very much for your response Pinkerton.

I am referring to a 105 Qt. sterilite plastic tub (probably polyethylene) that comes from Walmart. The dimensions of this box are ~32'' x 19'' x 13'' which means that this is essentially a small tub. There will be 80% RH, room temperature (75F) air in the plastic tub. There are lots and lots of holes to provide frequent air exchange in this tub as well, so the air will need to be cooled at a fairly constant rate.

What my plan is to do for this project is to literally remove the door to the wine cooler, saw a hole equal in size to the sterilite plastic container, and make a seal. Since most wine coolers can keep temperatures down to 45F, I figured that while a smaller 9 bottle wine cooler is made for only 9 bottles worth of volume, it will be powerful enough to lower the temperature down to a mere 65F in a larger container since it has the capacity to work 3X that temperature change.

"If you can find an evaporator from a conventional refrigerator at will fit neatly inside the box YOU have designed to fit the contents, then you may be on the way."

Ahah. I like this idea. It seems as though this may be the way to go? Problem is, where can I find one of these for cheap and will it have a temperature regulator, or will I need to purchase some type of Rancostat or something to control the temperature ?

[Kelly_Bramble]

Ok, not that I am totally familiar with wine coolers, but here are my thoughts.

First, what you are trying to build is an environmental chamber. These are commercially available for $$$$$ - so, I like your approach.

Walmart or any other wine coolers are not likely to have precision control thermostats so you will need a secondary method to understand what the real temperature is within your apparatus. I suggest getting an accurate thermometer and chart wine cooler setting vs. actual temperature.

The humidity control part should be challenging as you will need a method of measuring and controlling the humidity. The wine coolers refrigerate evaporators will condensate water during operation. Refrigerate systems have a low point drain to remove the water so you will need a method and add and control humidity.

If you extend a box beyond the cooler as suggested, you are going to need to insulate everything. I doubt consumer wine coolers have very much heat removal capacity. So, every time you open this thing you will affect the chambers temperature.

You do have a camera?

All my thoughts for now…

wine-cooler.jpg

environmental-chamber-57744.jpg

[PinkertonD]

Kelly has covered it all for you, so +1 Kelly.

Although, now adding RH into the mix certainly can complicate things fast for temp/humidity balance and replenishment. You are off to a good start with a tub though as heat ingress will be at a minimum compared to a side opening door. Do you have to open the lid? How small a hole can you get away with?

[mikesado]

Yes, thank you guys for your support with this project. For this project, frequent air exchange is going to be necessary so insulation would make that difficult. I will be providing humidity with a cool mist humidifier, which is already rigged up and ready to go for the project. I will also manually open the container from time to time to mist for increased humidity.

@Pinkerton:

I can make as small a hole as I would like, as long as the tub will be cooled effectively. This tub can be modified and cut to make the temperature control work as needed, as it is pretty high priority compared to other aspects. FAE (frequent air exchange) is more important, however. There are hundreds of holes in the tub that are smaller than the diameter of your pinky finger, and these are for frequent air exchange. Those holes will likely make it more difficult to keep the container cooled well, obviously.

So.. does this information help narrow down the work capacity the wine cooler must provide for this application? Any ideas on that?

Will this not work without insulation?

[PinkertonD]

Will this not work without insulation?

Hate to say it, but most likely not. To stabilize the temp and allow the thermo-control to maintain a reasonable swing, maybe 0.5-deg up/down or whatever is your allowable spread, you will need insulation. The thermo-control will not maintain a steady temperature as it will have to trigger on at a "Low" and off at a "High." These refrigeration units operate on an average temp, not an ideal temp, well, not unless your pockets are deep. Check you beer fridge at home it will be on for about 15 minutes then off for about the same.

Without the stability afforded by the insulation the control will hunt, meaning it will be off for a second then on for a second then off -- ad nauseum. By the time it shuts off it will be over temp and similar for cutting back in.

The thermal mass you have in the container might help stabilize temps, but it will not be a consistent temp throughout the mass unless you have some means of normalizing that mass. If it is liquid then you will need a stirring pump to balance the temp. Insulation to help stabilize the on/off cycle will be imperative.

You will need to define that on/off spread to protect whatever the microbes are supposed to be doing.

What is the range of temp you can tolerate? Are we talking plus/minus 0.5-deg or 15-deg? The courser that range, the better chance you will have of doing this cheaply. The converse also applies.

[mikesado]

OH I can withstand probably up to 10-15F temperature changes, in fact temperature fluctuations are certainly even better than a constant temperature. As long as this would keep the temperature 65F on average that would be perfect, doesn't have to be constantly 65F.

Likesay - room temperature is 75F and the ideal temperature is 65F so I want to keep the temperature near 65F (lower would be fine, also)

[PinkertonD]

Mike, I am not sure where to go from here. This is a complicated thing to design in just theory and even more difficult to relay thoughts and ideas to you via the Internet.

Given that you have an acceptable temperature spread that includes (even exceeds) room temperature, and fluctuations are acceptable, even desired, you probably can get away without using insulation.

Having said that, if the spread is that great then why not just put the thing in a conventional small bar-fridge?

I modified the thermostat control on a bar-fridge to use as a red-wine cooler. I bought a 4-cf bar-fridge for $15 at a swap meet. I bent (curved) the bi-metal strip up a little further from the contacts so I could use the mid scale range of the control and get temps in the 65deg range. It holds 62-64 degrees Summer Winter etc.

{edit}
p.s. Great place to store the butter. Cold enough to keep it safe, warm enough to spread nicely.
{/edit}

The only problem for you, with that, is, I don't need or desire air-exchange circulation. You could also try doing similar and leaving the door ajar for circulation.

A 1" x 2" stick with several nails would allow adjusting of the door opening by engaging the appropriate nail in the leading edge of one shelf.