Micro swamp cooler

[flapdoodle]

I made the first practical test this morning on a trip to town. The cooler kept the temperature in the cab to 91 or less the whole time, in spite of 99 degree ambient temperature. However, it made it so humid I shut it off and rolled the window down. I don't do well with humid. The device does shine when there is no sunlight. If I really wanted it to work in the hot summer sun it would require a much more robust unit. Oh, well. It WAS an experiment.

[flapdoodle]

It was 111?F today. I had a few ideas and just HAD to try them.

1. There is no question the water pump has ample volume and pressure.When the engine gets up to speed the voltage goes from 12 to 14 volts, the increase in speed is obvious by the sound. Foam comes out of the evap pads and water splatters onto the new upholstery leaving white calcium spots.

I cut the aluminum drier hose down to ~4 feet (it was 20. Longer hoses have more resistance), then cut a length of porous 1/4" drip line and replaced the single dripper that came with the humidifier pad. The porous tube minimizes the amount of water so the there cant be so water logged only a little air can pass. I.E., the pad doesn't get flooded and block the air flow.

I have two smaller fans 1/4 the size if regular fans, they turn at trice the speed using .66 amps each. and really scream. Those two fit nicely between two regular size fans.

With switches, I can run 2 or 4 fans, OR 4 fans with the center two running twice the speed.

I now believe the evaporator pads should be larger the the motors by a lot, because wet pads have less flow than dry pads. In other words, even if the pad are quite wet, there will be plenty of spaces for the air to go through.

Tests so far had the cool air blowing at the passenger seat, making calcium deposits on my new upholstery. The whole time I have been writing this I had a 6" fan down on the floor blowing upward. Nice, it cools my legs, crotch, belly and chest and face. From that I hope to pipe the air from the cooler to the drivers side and blow upward toward the drivers face. (I would rather it blow on me than to the passenger seat and roof.)

[GasSavers_JoeBob]

Does your truck have any kind of flow-through ventilation? If so, that may be all the ventilation you need, and you won't need to crack the windows open.

Maybe restrict the water flow through the pads? If you have too much, and it continues to spit water like it is now, it'll really annoy any female passengers you carry! Had that problem with one of those old window coolers on a Nash Rambler many years ago! My wife made me throw the thing away!

For the folks living on the east coast, you can do what my grandmother and mother did on a vacation in the mid '30s...put dry ice down by the vent. Crack open a window (that is carbon dioxide...) and it kept the car comfortable.

[flapdoodle]

There is a vent built in to each door with a check valve (sort of a flap). I noticed that my feet were cool, likely because the cold air sinks. Cracking the window was an attempt to flush the hot air out. It needs more flow when the truck is not moving.

If I rebuild it it will have a much larger pad area. I experimented with porous tubing used for drip irrigation last night. So far it looks like just the thing for wetting the pads. I also gathered all the 12 volt fans I have scattered about. The best are two small (1.5 x 1.5 x 1 inch) high speed fans. They draw .66 amps each. More than I wanted, but it takes energy to move air. They are noisy, but really push air. I would have to be careful I don't run the battery down. Maybe a switch to cut one out when it is not so hot, or at night.

Thanks for your ideas and input. Those old window coolers sell for a bundle on eBay now.

[GasSavers_Erik]

Rather than cooling the air in the entire truck cab. How about having a nice sized fan pointing at the driver's seat and using a single tiny misting nozzle to spray into the airstream. Could that produce a blast of cool air?

If you do need to cool the air in the cab, how about placing the moist pads in the air inlet duct under the grille between the windshield and hood and using a windshield washer pump to periodically moisten them. Then you could just use the stock blower for air circulation and you'd be drawing in fresh air all of the time. But if you live in a dusty area, I could see how the moist pads would be pretty nasty after a few hours...

[flapdoodle]

Some very good ideas. Thanks Eric. Yes, a very dusty area. We have not had measurable precip here since last August.

[flapdoodle]

I started from scratch on a second version now that I am sure it does have some advantage. Weather is predicted to be more normal after the insane 112 degree temperatures.

The float is a small pill bottle with a plastic drinking straw glued into a hole in the cap. It resides in a modified spray paint cap. Holes are drilled in the sides of the cap to let water in.

Once I have the water level filled to max (just below the bearings in the pump) I will mark the level on the straw. Them pump it dry and make a second mark.

[flapdoodle]

It looks like my camera is not storing all the photos and I have to retake a few.
The level indicator float guide and the 12 volt pump are attached to the bottom with Shoe Goo, which is an adhesive similar to Goop. It holds great but can be removed easily if necessary. However, in this case the solvents warped the bottom of the container. Not a problem since I was considering a better base to make it more stable in a fast stop or turn.

I made a pump pickup from a scrap of curved steel tubing so it would pick up water close to ther bottom. That also increases the stored water capacity a little.

I cut a new pad that is twice as wide as the last one. Should allow for better air flow.

[flapdoodle]

Second version is now done. I worked almost through the night, though much of that was waiting for paint to dry. The paint is Glidden polyurethane Floor & Porch. I have used it on boats successfully, so fairly confident it will work okay here.

The pad area is exactly twice the previous experiment. It can be seen in innardstop.jpeg Note the black splotch on the left side. This is put on at Honeywell to indicate the top of the humidifier pad. This is because the aluminum mesh is designed to keep the dripping water toward the center. It is a used pad I cleaned up a bit. A new pad has what looks like paper laminated to the aluminum mesh. (not absolutely certain of that, but it is not shiny aluminum colored.

I had planned to use two rows of the Rainbird porous hose, but there is not enough room. Instead, I punctured the hose in a dozen or so places. I may add more as I bench test. Those added holes dropped the temperature from 67 to 62 degrees. A nice to have feature might be a switch to run the pump alone to pre-wet the pads.

The pump was the only item purchased just for this project. This is one just like it, but I got mine for $6 (if I remember correctly)

http://cgi.ebay.com/Mini-12V-Water-P...item35af3f9e32


One thing I changed before it was even finished was to move the float level indicator to the front.

Note the front is semi-finished. This is in case I want to mount a 90? PVC joint to aim the airflow more toward the driver.

Still thinking about Eric's suggestion for a mister in front of the driver, but in earlier tests, my feet were comfortable since cold air sinks. Maybe a small fan and short hose to blow air up from the floor toward the drivers chest and face.

Forecast for the next 5 days says a high of 94-95 ?F so should be able to get some decent testing. Highs of 112 suck!

[flapdoodle]

The first test of the latest version showed the porous tube was not enough. I drove about 6 miles with ambient temp at 94. The cooler kept it at 87 or less and used a surprising amount of water. It stopped cooling shortly before I got back to the shop. The 90 degree elbow at the drip tube was clogged. A filter screen may be required.

I drilled a row of 1/64 holes in the trip tube. LOTS of water but not enough to spit on the upholstery, so should be close to optimum. Temp at the pad fell immediately to 72.

A family emergency and now an oil pan gasket leak has slowed testing down, but so far this looks like a practical experiment for moderate high outside temperatures. Not practical when it is 112 outside. But that isn't too surprising. The heat pump for the house wasn't able to cope either.