The Summer Comiket can be one of the more severe experiences in terms of heat. The organisers of the event constantly caution participants to regularly rest and hydrate to avoid heat stroke. The 2013 Summer Comiket was hands down the hottest, most uncomfortable experience of my life. At one point, there was a literal fog formation in the hall due to the heat and humidity.
As I was there on the third day helping a friend sell books, I was going to be there for an entire day. While many people use different methods to keep cool/comfortable from ice cold drinks to personal portable electric fans, this year I decided to go the extra mile. Taking inspiration from the concept of computers that use a circulation system of liquid coolant to keep their CPUs from overheating, I played around with the idea of having some kind of suit with piping inside it that would similarly circulate coolant to keep the wearer cool.
After some research, I discovered that such suits do exist on the commercial market. Unfortunately, generally used by professional athletes, such cooling suits are much too expensive for the casual everyday Joe. Undeterred, I considered the DIY option of making such a suit myself.
The essential idea was simple: Have a pump that would circulate ice water through tubing that would be sewn to the inside of a shirt. A cheap electric aquarium pump would probably suffice, but that led to my first big hurdle; the power system.
Electrical outlets are not provided at Comiket, that and, with the possibility of having to move around, something portable was preferable. I looking into getting a portable battery with a standard power socket that could also carry enough juice to power a pump for an extended period of time. (My engineering skills are not enough that I could fashion such a battery myself)
The problem was solved, however, when I went to my local hardware store to look at potential pumps to use. Among the gardening equipment, I found a bunch of battery-powered weed-killer sprays. Not only were they relatively affordable, but if I could find a way to switch out the tubing, I would solve my power issues, pump, and coolant containment all at once. I looked around until I found one that was cheap and offered both adequate tank volume and could be used continuously for several hours. Finding one that matched my criteria, I purchased it and about 20m of tubing and went to work.
The first thing I did was void the warranty and disassemble the spray to remove the spray tube and nozzle. Next, I attached the tubing I have bought. Although the tubing wasn't a 100 per cent perfect fit, I managed to get it on and secured.
Next was the hard part -- sewing the tubing into a suit. I took an old tattered shirt and loosely sewed the tubing inside so that it coiled around for maximum surface area. I then poked a hole in the fluid containment cap and fed the end of the tube back into the tank to create a circulation system.
My contraption complete, I set about running experiments to see if it would work. Pumping ice water through it worked fine and indeed had an almost immediate cooling effect. However, the Comiket event lasts for 6 hours, and there was no way that my cooling shirt would be able to continuously keep me cool for that long without eventually returning to room temperature.
To maximise the effectiveness, I filled the tank about two-thirds to three-quarters with water and put it in the freezer to create a large block of ice. I then filled the remainder of the tank with cold water and then ran the pump continuously in a room that was about 30C. The ice melted and the water warmed to room temperature after about two and a half hours. Without a secondary cooling system to maintain the water temperature, this was about the best that I could hope for.
Another unfortunate setback was the sound of the pump, which was noticeably loud. It wasn't overbearing or anything, but just enough to be annoying. I worked around this by wrapping the device in tin foil and towels and then stuffing it in a small carrying case. This served to not only muzzle the noise, but also to act as insulation and hopefully extend the effective duration of the cooling.
The day of Comiket, I took my cooling device and headed to the battleground.
Shortly before 10am when the doors open, the hall was around 29C with 55 per cent humidity. It was hot, but not unbearably so. Not enough to warrant artificial cooling.
Shortly after 10am, the halls were filled with thousands of otaku, rushing to buy books. The temperature rose only slightly to about 29C. The humidity, however, shot up to 70 per cent, making for a somewhat uncomfortable environment.
By 11.30am, the temperature had inched up to 30C with a humidity nearing 80 per cent. This made for a very, very uncomfortable combination. While the heat alone may not sound too horrifying, the high humidity means that sweat cannot evaporate, rendering the body's natural cooling function useless. By noon, it was time to bring out the DIY cooling shirt.
Switching on the pump, the initial feeling I felt was cool soothing relief making its way across my body. While little could be done about the humidity, I was almost instantly rescued from the sweltering marshlands and whisked away to... a frozen tundra.
The cooling shirt worked very well. One could almost say it worked TOO well. The ice cold water pumping through the tubing that surrounded my body was soothing at first, but after a few minutes, was quite freezing. I was forced to turn the pump off and on again at extended intervals to prevent it from getting too cold. While fortunately I was wearing a t-shirt underneath which ironically acted as a buffer between the cold, if the tubing had been in direct contact with my skin, I believe it would have been almost shockingly cold upon use.
Another setback occurred in that due to the gap between freezing the ice block in the tank and actually using the pump, the cooling only lasted for about an hour and 45 minutes. Fortunately, despite the shortened effective time, it allowed me to survive the worst of the heat of Comiket. By 3pm, the crowds had lessened and the relative humidity dropped to about 65 per cent.
All in all, despite the setbacks of being unable to adjust the temperature and the shortened effective period, I would say the cooling shirt was a success. I'm already considering the possibility of adding a condenser to maintain the coolant temperature and other potential under-armour-esque fabrics to use to keep the tubing from being too cold. At the end of the day, my friend I was helping said I was like Iron Man. I'm rather proud of that comparison.
Until next year.