For all of you that live in areas where humidity is somebody else's problem, evaporative cooling is a very good way of creating comfort. Here is a writeup I did on my latest upgrade for my Jeep.
Jeep Onboard Misting System
One of the primary reasons I bought my TJ ten years ago is because the lid comes off allowing me the open Colorado air all summer long. The flaw to this is that it gets hot in summer, sometimes uncomfortably hot. Usually when this happens I remind myself that the top will be on all winter, and that a little sweat is a small price to pay for the top being off. In summer I have always kept a misting spray bottle in the Jeep to spray myself when stopped at lights. If I thought running the air conditioner without a top or doors would do any good I would put one in. This year I decided to address the problem.
Among my favorite places to drive my Jeep to in summer are bars with patios. There I can enjoy a cold beer and the cool mist of the misting systems that many patios here have. It occurred to me that such a system could be mounted onboard a Jeep fairly cheaply. I researched this on the web, and found that it was not exactly an original idea. I even found a guy selling them pre-made. Unfortunately he was out of business. He is a very nice guy, and I spoke with him for a long time discussing the design of his onboard mist system.
His design pressurized a tank from a compressed air source, forcing water out of his tank at high pressure to misting nozzles. I drew up a design based on his using my 5 gallon Jerry can as a water source, and my onboard air as the propellant. After much discussion at work (bring up a project in a room full of engineers and much discussion will occur) we used a water pump instead of pressurizing the tank. It seemed quite a bit safer. We did however keep his approximate misting nozzle locations.
The project was adopted by the whole crew at work. One of the guys donated a RV water pump he had in his garage to my project. Another donated a slightly mangled garden misting system that he had laying around. We rigged up a proof of concept test, and made a wet mist mess in our shop in the middle of a very cold Colorado December. A little bit of mopping and the shop was good as new.
Just this week my top came off for the year, and work began on my misting system. The first day I did some shopping at my local hardware store for some adapters, ¼ inch hose to attach the misting nozzles, and a ½ inch feed hose. I mounted the pump behind my rear roll bar under the tonneau cover. I ran the ¼ inch output line up the roll bar, across my rear rack, and mounted the misting nozzles to the rack pointed at the cab of the Jeep. I drilled a hole for the feed hose, and a vent hole in the lid of my Jerry can, and ran the line down my roll bar to my pump.
The second day I installed a relay near my pump, and ran power from the battery. I ran a switch to my console to control the relay. With everything installed, it was time for an operational test. I filled my Jerry can with water, flipped the switch and made mist. I then took the Jeep out for a spin. Unfortunately it was 50 degrees that night, and the mist made the cab damp, and me cold, but it worked well.
The third day I worked out some bugs. It turned out the vent hole needed a small length of hose stuffed into it so the water didn’t jump out on turns and bumps. I also tried the misters when the temperature was in the low 70’s. The mist made me go from perfectly comfortable to cool, and evaporated almost instantly in the cab. I am waiting for a nice hot 90+ degree day to really test it out but my expectations are high. The aerodynamics of my Jeep are so bad that the mist is pulled from the rear of the Jeep to the cab at any speed above a full stop.
One benefit of the location of my misting nozzles is that with my tailgate open, I can turn the nozzles to point out the back of the Jeep. I can then put my folding chair behind the Jeep and stay cool when camping, or sitting in the pits at the race track.
Another benefit to developing this project at work was the advice I received from some friends of mine who are traffic patrol officers. In many areas, it is apparently against codes to carry modified gas cans, so it was suggested that I label the gas can “Water” to avoid being pulled over. I made a sticker appropriate to the advice.
2 misting nozzles
1 RV water pump. 12V. 40psi.
¼ inch ID hose
½ inch ID hose
Jerry can with feed hose
The hose running down the roll bar to the pump below
The pump mounted in the corner under the tonneau cover
The misting nozzles mounted on my Olympic rack