In the past few decades, we have witnessed huge transformations of every day things around us, specially in their physical sizes. A lot has changed from heavy unmovable space-eating giants into highly mobile portable things that fit well in our pockets or backpacks. Computational devices are a prime example for this transformation.
Surprisingly, refrigeration hasn’t evolved into a such highly portable form yet. There is nothing we can carry in our backpacks when we go for an outing to chill our canned beverages or bottles of water. To this end, in this project I propose a cooling mechanism which uses the compressed air as the coolant. If successful this mechanism would enable building portable cooling devices to chill beverages “on-demand” within few minutes. To complement our main theme of “Heat for good”, I decided to present this idea as solar powered chiller, which uses the power generated from solar panels to compress the air.
The cooling mechanism of this device is based on Amontons’ Law of Pressure-Temperature : The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas’s absolute temperature.
With this theoretical back ground I tested the practical feasibility of this system using a simple setup. My test setup was consisted of DC air compressor and a copper tube- one end connected to the compressor. The other end had a valve.
- Air-compressor pumps the air to the copper tube and increase the air pressure inside the tube.
- After the inside air pressure reached a desired level, user open the valve allowing the air pressure to decrease drastically resulting a temperature drop. This results a temperature difference between the liquid(beverage/water) and the air inside the copper tube. Therefore a heat transfer will happen from the liquid to air through the wall of the copper tube.
After several failed attempts I was able to use the system to reduce the temperature of water (around 750ml) from 2C degrees. But I couldn’t reproduce the same results because of the problems I had in my setup.
After this initial experiment, I realised even though the concept of the system is somewhat formidable, building a functional prototype is beyond the DIY level because of the following reasons.
- Compressor draws around 5A current which is hard to supply from Solar panels.
- Difficulties in making the copper tube air tight at the two ends
- Difficulties in re-shaping of the copper tube to have a coil shape
Even though, making of a functional system is not feasible, I believe this idea has a potential of becoming a reality at industrial level with tailor-made components and techniques. Because of this, I shifted my focus to speculate on future design possibilities through the following non-functional prototype.