There seems to be a lower size limit for conventional, compressor-based refrigeration. The result is that portable cooling devices are always simple fans, or at best, evaporative cooling units. What prevents conventional refrigeration and air conditioning from working at sizes much smaller than a dorm refrigerator?
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There are relatively small portable AC with compressors.
Here is a [12 pounds compressor AC](https://www.amazon.com/Zero-Breeze-Mark-2/dp/B08Z3HNXH1/ref=sr_1_3?dchild=1) that has a built-in battery pack for power.
A major problem with them is that cooling requires an enormous amount of energy so a large part of the weight is the battery. Its cooling capacity and operational time are also quite limited so it is not especially practical.
There is a nice video debunking the claim of that AC. It is a working product that can produce cool air. The problem is that it is not practical for the shown usage cases. [https://www.youtube.com/watch?v=zol–A-CT8M](https://www.youtube.com/watch?v=zol–A-CT8M)
A major problem with them is that cooling requires an enormous amount of energy so a large part of the weight is the battery. Its cooling capacity and operational time are also quite limited so it is not especially practical. There is a nice video debunking the claim of that AC. It is a working product that can produce cool air. The problem is that it is not practical for the shown usage cases.
There are AC build to be used with batteries for campervans and similar applications, [like this 12V 9500 BTU AC](https://www.campervan-hq.com/products/nomadic-cooling-2000-12v-rv-air-conditioner-9500-btu) It draws 40 A in normal operation with a weight of 61 pounds The batteries you need to run if for any reasonable amount of time will weigh a lot. A 270 Ah 12V lithium phosphate battery weighs around 80 pounds and costs over $2000. It could run the AC for 270/40=6.75 hours.
The result is that portable “AC” are evaporative cooling units because the weight vs power usage is a lot higher. Even if you could make very small compressors for an AC the power requirement will be so high that if you like to get a lot of cool is you need very large batteries and they are not longer portable. If you need an outlet there is not a lot of reason for very small size, you need cooling capacity.
For refrigerators, the size limitation will be because you need an internal storage volume. Ther are [11-liter compressor coolers](https://www.dometic.com/en-us/food-and-beverage/coolers/electric-coolers/dometic-cdf-11-139583) , It weighs 18 pounds and needs an external power source. There will always be a base cost for compressors so most will be larger because the more internal volume is required.
The result is that the smallest you find is for car usage. They can operate for quite a long time with quite small battery packs.
There is not a marker for battery power refrigerators intended to be carried around, The cost and weight time that would be used will not compare favorably to just an isolated container and icepacks. So if you carry them the time then need work is a few hours and then ice and isolation is cheaper and lighter.
So the market for a portable refrigerator is for car and similar usage where it needs to keep cool for multiple-day and you need enough volume in them.
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