Instructables

Dew Bucket : Evaporative Drink Cooler

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Step 8: Finish

Picture of Finish
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That's it! This Dew Bucket is ready for testing. Just jam three bottles into their slots and add water, warm water works fine. Evaporative coolers perform best in hot, windy environments with low humidity.

At moderate humidity and a light breeze, this bucket cooled 90*F water(room temperature) to 69*F in one hour. The lining was soaked in 90*F tap water.

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dataphool3 years ago
I suspect that the Relative Humidity inversely affects the cooling ability of this device, can you confirm? I live in an area with humidity over 90 % for weeks at a time. At that time the temperature climbs above 35 degrees (95 degrees fahrenheit). Good idea, but possibly of little use here.
JamesRPatrick (author)  dataphool3 years ago
That's right. Evaporative coolers work best in hot, dry environments.
@ dataphool and JamesRPatrick.  At almost 70 yoa, except for some moving around during my work years,I have spent most of my life in SE Texas on the border with Louisiana, and about 8 miles inland from the Gulf Coast.  We DO HAVE HIGH HUMIDITY!!!!!

To answer dataphool's question, yes, the Relative Humidity DOES inversely affect the cooling ability, and yes, evaporative systems do work better in dryer environments, BUT... it DOES COOL at all humidity levels.

Our humidity here ranges from about 70% to 95% most of the spring, summer and fall.  As a child and before mechanical [Freon] A/C poor folks like us had NO cooling other than table fans and wet sheets.  And it did cool us somewhat.  The biggest problem was having to get up several times during the night to re-wet and wring out the sheet!!!!

Only rich folks, or at least the affluent, could afford whole-house air conditioning, and in those days even theirs WAS EVAPORATIVE! 

A house would have a REDWOOD COOLING TOWER [about 4 feet by four feet square and about 5 or 6 feet tall].  At the bottom was a water reservoir about a foot deep, and at the top was a set of "spray" nozzles.  A pump circulated the cool reservoir water into the house and through a "radiator" in the central heating air handler and returned the warmed water to the sprinkler heads at the top of the tower.

The falling water droplets evaporated some of the water thus cooling it.  Depending on the relative humidity, the water in the reservoir would be 25 to 45 degrees cooler than the ambient air.  They had a toilet float/fill valve to automatically maintain water level because a LOT of water was lost to evaporation.

EVEN on a 100 degree 90% humidity day, the house interior would be down around 68 to 70 degrees, and the reservoir water temp [before circulation in the house] would be like 54 to 57 degrees.

So, even in high humidity, some evaporative cooling DOES occur.

As proof of that I suggest that any doubters do a test:  on a day of high humidity in your area; pour ambient temperature [NOT hot or cold] water on your forearm, and then hold the wetted area in front of a table fan.   You WILL FEEL the evaporative cooling effect. And I assure you that this will occur even at high Relative Humidities.

Since we now know that evaprative cooling occurs, and even in high Relative Humidity, the only issue in effectively using it is to make the "chilling" tower system LARGE ENOUGH to transfer enough heat.

About 10 years back I made a small test cooling tower out of a 55 gallon plastic drum into which I cut dozens of vent openings, and on days of 90 degrees and 80 to 90% relative humidity, my reservoir water would run about 55-58 degrees. 

Of course in that test set-up I was not adding any heat to the water by trying to cool the interior of a building.  The amount of water in my system was about 10 gallons captured in the unlouvred bottom of the louvered barrel. 

I never got around to up-sizing the test system and trying to cool my house interior, but I'm convinced that sized properly it would have worked.
j574sbi3 years ago
making one tomorrow, thx
JamesRPatrick (author)  j574sbi3 years ago
Great! Be sure to post some pictures of your build.
bessboo3 years ago
This is a great idea. I'm always amazed by the old forgotten technology that you are able to bring back to all of us. Thanks so much for your efforts.