It was hot that day. Very hot. So hot that the cats were getting all melty. They also were seeking out the coolest spots they could find: lying on the wood floor instead of on the rug.
Suddenly, I thought, hey--- wouldn't it be nice to give them an especially cool-feeling place to lie down on? Here was my first idea:
Important points include:
- roughly cat-sized
- resting surface has high heat transfer coefficient (Al is good, Cu is better but way more expensive), and thus "feels cool" even when it's the same temperature as the room air
- room for air circulation underneath, which allows
- evaporative cooling from the "wick" (dishtowel), which cools the resting surface further
A quick trip to Crate And Barrel outfitted me with the materials I needed for a prototype: an uninsulated baking sheet, dish towel, and a "cooling rack".
Once home, I began construction immediately. I wet the dish towel with cold water and wrung it out so it wouldn't drip. I put the cooling rack on the floor, placed the damp towel on top of it, and then put the cookie sheet on top of the towel. The top of the cookie sheet felt cool to the touch.
It was time to start Phase I Clinical Trials.
Phase I Clinical Trials
In Phase I, I wanted to test the cat cooler on small group (one cat) for the first time to evaluate its safety and identify any side effects. The Phase I cat was selected, lifted up from where he was lying on the hardwood floor, and placed on the cat cooler.
The cat cooler seemed safe, and no side effects were observed. Subjectively, the cat seemed to respond positively to the treatment. Time for Phase II Clinical Trials.
Phase II Clinical Trials
In Phase II, my goal was to try the cat cooler on a larger sample (a slightly larger cat), to determine the efficacy of the treatment. This time, the cat cooler was placed under the coffee table -- an area that the cats normally do not like in hot weather, but do like in moderate or cool weather. I theorize that this is due to the low heat transfer coefficient of the carpeting; even if the rug is the same temperature as the hardwood floor in the dining room, or the tiles on the bathroom floor, the rug feels hotter.
Luckily, the Phase II cat is more adventurous than the Phase I cat, and the Phase II cat immediately investigated the cat cooler, climbed onto its surface, and settled down right there.
The Phase II cat remained on the cat cooler for quite some time, perhaps half an hour. Given that the cat would not have stayed on the rug under the coffee table given the heat, but that he did stay on the cat cooler under the coffee table, I believe that the cat cooler was at least somewhat effective. Admittedly, there were no "control" cats, but if you've ever lived with a cat, you understand why.
Ongoing: Phase III Clinical Trials
In Phase III, we'll be using an even larger sample (a very large cat), to confirm the effectiveness of the cat cooler treatment, and to compare the current design of the system with some alternatives as well as other commonly used treatments.
I now find myself wondering how much of a difference the evaporative cooling (towel, water, cooling rack, air gap) actually makes. Perhaps simply putting down an aluminium or copper baking sheet by itself would be sufficient; either material would feel cooler than a rug, a wood floor, or even bathroom tiles. On the other hand, the evaporative cooling mechanism also actually lowers the temperature of the surface. I definitely want to try offering the cats their choice of both conventional and liquid-cooled cookie sheets, and see which they prefer.
I have subsequently also tried more extreme cooling. In one case, I placed ice chips between two damp towels between the cooling rack and the cookie sheet. In another case, I set a small fan blowing under (and over, and around) the cat cooler, to force more evaporation, and thus more cooling. In both cases, exactly zero cats were interested in participating in the trials. The ice chips seemed to make the resting surface too cold, and the fan was too loud, forceful, and fur-ruffling. I suspect that a small (solar powered?) hobby motor with a small fanblade, could be placed under the cooling rack to force some evaporation without causing the fur to fly.
I'll post more results as I get them, but I'm optimistic.