5 stars for Siwastaja!! He explained perfectly well the pros and cons of colder temperatures and provided samples on how to achieve the right balance!It makes little sense to overengineer a ghetto cooler.
You're probably right, but overengineering is so funny!!
And yes, others are right about not needing colder temperatures. Thermal capacity of ice is crap anyway, it warms up to 0degC pretty quickly, regardless if the initial temperature is -10 or -20 or -30 degC. It's the phase change from ice to water which stores (and releases) most of the energy, and this happens at 0degC pretty exactly.
Does this applies to gel ice packs too? I know there are several variants and
here are discussed all the technical details. I tried to follow the discussion, but is very advanced stuff and I just preferred to buy mixed brands and see what are the ones that work better.
But this is not a problem at all, ice at 0degC is more than fine for cooling. Remember that temperature and energy are two different things. You can cool with material at 10degC, 0degC or -10degC equally well providing same cooling effect, just requiring some more surface area and/or airflow if the temperature isn't as low. Actually you don't want to cool with colder than 0degC material because then room humidity freezes and finally blocks whatever radiator type you are using. Another thing you don't want to do is to cool with >15degC water; even if you can cool with say +17degC water (using large enough radiator and air flow), it won't have drying effect which is often desirable in humidly hot conditions. If you just cool without drying, relative humidity just rises and it still feels uncomfortable. But if you run say +10degC water in your radiator, then it is already capable of drying the air down to dew point of approx. that 10degC (or a bit more), which is already very comfortable.
You said that I can cool with material at 10degC, 0degC or -10degC equally well providing same cooling effect, just requiring some more surface area and/or airflow if the temperature isn't as low.
Does this means that a colder temperature is not totally useless and still have the desirable advantage to require less surface area and/or airflow?
If I have understood well, on the other side, I don't want to cool with air which temperature is higher than 15C.
The guy from which I posted the amazing unit which cooled down a room temp by 10-20C got an output temperature of nearly 2C (its climate is dry):
![](https://i.ibb.co/CHjkzMr/msg.jpg)
Do you think that 2C is the correct balance (with the previous mentioned advantages included) ? Keep in mind that my climate is humid (around 50%). I don't know why didn't worked for the other 2 guys, there are to many variables that should be checked included dry vs humid climate. Plus my design is completely different, so I can't really compare.
The biggest problem in ghetto coolers is the capacity of typical household freezers. Even if the freezer was conveniently located in a far enough room so that its heat output doesn't ruin your cooling, you would still need to keep swapping ice packs nearly 24/7.
Fortunately the floor of my house where there is the room I want to cool is free from any household freezer.
The annoyance of swapping ice frequently is pretty much inexistent. That cooler, with a 28QT chest (3 days ice retention advertised), 2 frozen gallon jugs and a couple of ice-packs, latest 4 hours. Good for daytime, but not for nighttime.
Mine uses a 52QT chest (6 days ice retention advertised), it is nearly fully insulated and uses gel ice packs in higher quantities. I expect much longer duration and good even for nighttime.
The freezer compressor runs nearly non-stop and freezer's inside temperature rises; so you can't use it for storing foods at the same time, they get spoiled.
This is something that I have not considered at all. My freezer is pretty new technology, but apart from this I can't really imagine how this can happen. Freezer's inside temperature rises each time we introduce new food, but this is just how they are designed to work. Do you recommend to pre-cool the ice packs in the fridge?
Therefore these ghetto coolers tend to be good only for short demonstrations; you freeze a few liters of water and you can feel how it really works. Except that after 3-4 hours you are out of cold. Even if you did put more water bottles into the freezer, they are not frozen yet. The capacity isn't there: compressor power is some 200W and COP pretty crappy like 1.5-2 at most. Real air conditioners have higher evaporator temperature (remember: it does not try to cool anything to -20degC like a freezer does) and lower condenser temperature (it has a decent fan-cooled coil, not some tiny convection cooled grille on the back like freezer) so much smaller differential and therefore COP like 3-5, and still you would like to have at least 500W of input power for serious cooling.
Maybe with two-three typical household freezers, located on a balcony or something so that they don't heat up the house, only dedicated for ghetto cooling, you could do this continuously, sure. But if you don't have even a single dedicated freezer, it's only going to work for short demonstrations, and as such is not worth investing a lot of time and design into. But, because it's an interesting experiment, I don't want to shoot it down either: therefore, duct tape!
I have several ice packs, so while my cooler is cooling, at the same time the freezer is freezing the ice packs for the next cycle. Yes, with a cycle that lasts 3-4 hours, the next ice packs supply is not ready yet, buy given how I designed the cooler, I expect much longer duration, even more than the time needed to freeze a one cycle supply.
Now, given that all my estimations are right (and there's no guarantee), I'm correct to deduce that the only concern could be the power consumption of the freezer (which should not make much difference anyway because I'm using one freezer only with the highest energy saving rate) ?
It would be very interesting to hear the opinions of that guy about such statements especially. The results he achieved are in contrast with what stated here from several users. I'll invite him to join the discussion, I'm sure this thread will become more interesting if there are people with different opinions (which unfortunately seem to lack).