Bells and whistles fridgeador (was First simple fridgeador)

[Julesgf]

Hi All

My small humidor is bursting with sticks.

Just bought one of these. Budget wine fridge

Been thinking a little about condensation control. I love Ray's thinking with his active humidification but...

I cant see why beads and dew point control shouldn't do the job just as well. If one was to expose the cold coil and add a significant fan to circulate huge amounts of air over the cold coil while the compressor runs (and a while after) that alone should prevent condensation, given it's only coming down to 18C and so long as one has beads spread over a large surface area.

If it still condenses you could add a simple condensation sensor to cut power to the compressor until the moisture has been driven off by the fan. Even something simple like this should do the trick Sensor (you can tell the product works judging by the website) jk

What do the experienced experimentors here think? totally bonkers or just regular bonkers?

Cheers

JF

[Julesgf]

Hi All

Thought I'd update this thread with my tinkering.

Well who would have thought it's actually quite tricky, hehe

What started as a "quick" job has ballooned into a really interesting project and I cant stop playing with it!

In this fridge, and I assume it's a typical compressor based bar fridge, the cold coil is built into the back wall of the fridge. ie the upper portion of the rear wall gets cold and cools the fridge contents.

Unmodified this causes lots of water vapour to condense on it and drain out of the drain hole below the cold coil.

I started by getting hold of a humidity and temp logger http://www.lascarelectronics.com/temperaturedatalogger.php?datalogger=102 and putting some cedar boxes, 2lb of 65% RH beads, covering the condensate drain hole with a small volume of beads to slow airflow but allow it to drain (which it never does with the big fan running) and a few bottles for thermal mass in the fridge and testing. (I've taken 6 hour slices from the logs for this post)

First thing I noticed is that it's damn hard to do this kind of testing with a regular humidor hygrometer, I was checking on mine as I was testing and I didn't realise there was anything like this much variation going on, you just cant see the pattern when your only seeing one figure.

You can see the compressor running for about 12 minutes every 2 hours, humidity is all over the place and temperature was not much better.

Because the compressor is running for a long time it's sucking a huge amount of water from the air and that's to be expected really, it's just something to compare later results to.

Ok, so I wanted to keep the humidity in the air rather than allowing it to condense on the cold coil and later drain out of the fridge. I also want to encourage the heat in the fridge to migrate to the cold coil faster.

I figured we should be able to help this by installing a powerful fan inside the fridge aimed at the cold coil to circulate air over it while the compressor is running.

This works! to the extent that it reduces condensation to about 5% of the unmodified state. However the humidity level still drops radically while the compressor is running.

So the compressor is only running for about 3 minutes at a time now and humidity is varying less, though still too much and too humid on average (68.5%).

Maybe we should run the fan all the time to smooth things out even more... well it's a powerful fan so maybe we don't want to run it all the time because it's stirring things up to much and will actually be heating up the air in the fridge (its a 8 watt fan at full blast), ok so I tried running it at 50% power while compressor is off and 100% while compressor is on...

Better in terms of stability but now we are to humid, from playing around it appears that too much air movement leads to the beads giving off too much moisture, at least that's my theory at the moment. It's also cycling faster than before due to the heating effect of the fan and also the slightly increased rate that heat migrates in from the sides of the fridge as they now have more circulation against them.

It's a bit frustrating because as you a running a test and checking the hygrometer you'd swear it's nice and stable, it's only when you look at the logging that you see the real story!

I'd been meaning to spread out the beads so I made a tray from stainless mesh just a bit smaller than the shelf size and spread the beads out on that which gives them much more exposure to the airflow.

I decided now to go back to only running the fan when the compressor and test the actual conditions the cigars are exposed to. The following is a log from inside a box with the lid deliberately left ajar to simulate a leaky box.

Pretty damn good! the chart is stretched to exaggerate the variation as the humidity is now held within +/-1%,

It's still to humid but the boxes were a little to moist to start with and that's dropping over the course of days.

The weather then swung cooler and I ran another test in a closed box...

This is over about 19 hours as it's the longer trend that was interesting here. (you can also see where I opened the box about 22:00)

The last 2 charts show the most interesting thing to me, the relationship between humidity and temp is reversed, now when the temp drops, the humidity rises because inside the box there is no condensation.

As I'd been playing with all this I'd been learning a bit about the physics involved, I knew that 1kg of hot dry air could hold much more water than 1kg of cold dry air but what really floored me was by how much!

To give an example if you start with a bag of air at 18C and 65% RH and gently cool that air to 17C you will have a RH of 69.2% !!! because the colder air cant hold as much moisture. Conversely if you were to warm that air to 19C it would have an RH of 61%

In a large humidor with no active heating or cooling the beads have quite some time to respond to the changes in temperature so can do a better job of it. In our fridgeadors the drop in temp INSIDE the boxes is quite sudden and typically about 1 degree C, there is also typically no beads in the box itself.

However it seems that we have a happy coincidence in that when the compressor runs there is a huge drop in RH outside the boxes which helps to largely offset the increase in RH as a result of temp drop inside the boxes. The boxes will be sucking this low RH air into them as a result of the colder air shrinking which is perfect!

The remaining problem is shown in the last chart, how to combat the winter effect of climbing RH.

Well I'd come this far so decided to go the extra mile and add heating to the mix. I've just received this thermostat http://www.robertshawtstats.com/modules/catalog/Product.aspx?singlePart=false&prodID=67487 which will allow me to hold the temp to +/- 0.5F and automatically switch between cooling (compressor) or heating (might just use the 8 watt fan as the heater).

I've have a super high efficiency 1 watt fan coming which will reduce the heating effect when circulating air in the cooling mode.

So it seems the outcome is to make any changes to the temperature VERY gradual ie weeks as would be the case in a cellar or to keep the temperature changes as small as you can.

My feeling is that controlling RH is really best done by controlling temperature very tightly and using beads to settle the RH. After all if the temp is held very tight and condensation is kept to an absolute minimum then the beads don't have to work hard at all

This has been loads of fun and no doubt I'll keep playing with it when I should be doing some real work. :-)

Hopefully all this is of interest to others and if anyone has made it this far through the post and would like to know how I go from here let me know and I'll do another post when I've installed the new thermostat.

I'm also interested to discover whether it will tend to pickup or drop moisture from the enviroment over a long time with all the door opening etc.

The spot my fridgeador is in is probably pretty bad in terms of the room temperature variation compared to other peoples but, hey it makes it interesting.

Cheers

JF

[thechenman]

Piggy? Is that you...?

[NMJoe]

Fantastic post! Nice work!

I would be interested in hearing how this experiment works out for you, especially if you continue with a much longer sample period.

[CanuckSARTech]

Piggy? Is that you...?

LOL!!!!!!!!!!

GOOD GAWD, THE EVIL SITH LORD DONE HAS AN APPRENTICE NOW!!!!!! RUN FOR THE HILLS!!!!! SAVE THE WOMEN AND CHILDREN!!!!!

[Wil]

Great stuff

[Julesgf]

I've just received everything I need for the new thermo etc

Will have a go this weekend if I get a chance

JF

[ZinZan]

LOL!!!!!!!!!!

GOOD GAWD, THE EVIL SITH LORD DONE HAS AN APPRENTICE NOW!!!!!! RUN FOR THE HILLS!!!!! SAVE THE WOMEN AND CHILDREN!!!!!

Julianf, what your opinion EL?

[LeafLover]

That is a lot of man hours. It's great to see that you are well immersed in your hobby and passion.

At the end of the day, hope your cigars are treating you well.

[Wil]

Julianf, what your opinion EL?

[Julesgf]

Julianf, what your opinion EL?

To pinch a turn of phrase...

A lot of flattering things have been written about LE's. Perhaps the authors have the advantage that their opinions are printable.

I would definitely go along with the complaint that it's short sighted to limit supply of a desirable item that benefits from ageing, just to drive up demand in the short term! Clearly only an idiot would buy them, which goes a long way to explaining why I have so many.

JF

[ZinZan]

To pinch a turn of phrase...

A lot of flattering things have been written about LE's. Perhaps the authors have the advantage that their opinions are printable.

I would definitely go along with the complaint that it's short sighted to limit supply of a desirable item that benefits from ageing, just to drive up demand in the short term! Clearly only an idiot would buy them, which goes a long way to explaining why I have so many.

JF

Ahhhh its not you piggy, i thought its piggy in disguise.

[SuprHasan]

How's the progress with this. Interested to hear.

[Julesgf]

I installed the new thermostat 2 weekends ago and it's working very well

there's 6 days worth, first half shows cooling cycles second shows heat cycling

I calibrated all my gear and it turns out the logger reads high by 1.5% RH. I'm more interested in stability though.

the cooling cycle tends to overshoot so that may be worth tinkering with

I'll do a proper write up when I get some time, but I'm very happy with where it's heading.

I'm resisting switching to PID control as that is a fair investment in time and really is going a bit too bonkers.

Cheers

JF

[socapots]

thats some good info, thanks for all the legwork!

its been about a year now..

How is it all working out now?

any changes?

[Julesgf]

No changes really

It's nearly full now which has evened out the cycling quite a bit. More timber / cigars = more porous and thermal mass... less $ in the pocket, less circulating air and bigger surface area of boxes also means faster heat / water transfer during heating / cooling, although there is now more mass to heat / cool.

It handled the summer really well. I've been comparing the humidity inside and outside the boxes and it's at least 6-8% wetter inside, regardless of location.

It would be really interesting to know if that's the same for other humidors. Assuming it is, I'm assuming the recommended conditions are for outside the box.

I can't work out what causes this, perhaps the drying effect of the cooling cycle, but the fact it returns to 63% outside every time you would think would leave inside and out the same, perhaps the hygroscopic cedar retains wetter air inside. hmmm maybe I'll try putting a plastic box in there with a small breather hole to compare.

Anyway, I'm happy with the cigars coming out of it, and they are, as far as I can tell consistent in water content.

Here's some pic's (globes on fan are used as the heating element, 12V globes running at 6V so very long life)

Cheers

JF

[socapots]

i gotta say.

Thats a good looking install.

Nice attention to detail.