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Two interesting cooling solutions - Printable Version

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Two interesting cooling solutions - Paul Foster - 10-06-2019

One uses evaporation. The other uses ice water and heat exchangeBoth are economical if you have access to water and in one case ice. You can purchase ice makers for $100+.

https://www.youtube.com/watch?v=0LTdGjirNj8

https://www.youtube.com/watch?v=nSA1OGhB-WI


RE: Two interesting cooling solutions - debit.servus - 10-19-2019

DesertSun02! I follow him and love some of the concepts he built.

(03-29-2019, 01:45 PM)lenny flank Wrote:  Neither of those will work very well. Swamp coolers use a LOT of water, and ice fans use a LOT of ice. They will be logistical nightmares.

Some math ... One pint of water will, as it evaporates, extract roughly 1000 BTU of heat energy from the surrounding air. So in order to get the same cooling effect from an evaporative cooler as from a small 2500 BTU portable air conditioner, you would need to evaporate around 2.5 pints per hour. This comes to 20 pints for each 8-hour period--roughly 2.5 gallons of water. For cooling equivalent to a typical small window AC unit of 5000 BTUs, double those figures--you would need to evaporate about 5 pints per hour, or roughly 5 gallons of water a day.

Some more math.... As a pound of ice melts, it absorbs roughly 150 BTUs of heat energy from the surrounding air. A common size of small portable air conditioner that can be run in a van from a generator or shore power is around 2500 BTUs. That means if you want to get the same cooling energy from an ice fan, you need to be able to melt 16.7 pounds of ice per hour, which would require roughly 128 pounds of ice for each eight-hour period. For cooling equivalent to a typical small window AC unit of 5000 BTU, double those figures--you'd need almost 34 pounds of ice per hour, or roughly 250 pounds per day.
Lenny Flank did an excellent write up on the math and physics involved with both water and ice cooling. The short answer is the amount of ice a $130 icemaker makes per day, you'll get spot cooling at best. Don't forget to keep the icemaker away from the space to be cooled.

What I have thought for low-power spot chilling is to take a 40 quart 12v compressor-based fridge/freezer, find a cubic water container with an inch off the sides, and dedicate it to freezing a block of ice overnight. You could get a couple hours of spot chilling with this, and be able to timeshift power loads. This is a small scale version of the thermal storage systems some commercial buildings have, they freeze giant ice tanks on cheaper nighttime electricity to cool during the day.

https://www.cheaprvliving.com/forums/showthread.php?tid=33530

Or if stealth isn't an issue get yourself this Frigidaire [https://www.homedepot.com/p/Frigidaire-5000-BTU-115-Volt-Window-Compact-Air-Conditioner-with-Mechanical-Controls-FFRA051WAE/311120672] (it's the smallest traditional window A/C I've found)

On vandweller evaporative cooling:
If 2.5 gallons for 8 hours of cooling is A LOT of water, you need to change your perception. Scarcity, does not create Abundance.

For Burning Man 2018, I drove a small sedan, and decided if I’m going to have to tent it, Im going to be as comfortable as I can be inside it. So I brought a 5 gallon bucket cooler and ended up running it 12 hours a day, and ducted through 4” flexible vinyl duct so It spot cooled me under the sheets in a dark blue colored tent. The fan in the twin bucket stack cooler (pad in top, water in bottom) was a 4” marine bilge blower powered by about 120 pounds of batteries which were fully charged prior to leaving.

Even if someone planted a device that changed the laws of physics inside the swamp cooler and it suddenly needed 60 gallons for the same cooling as 20 gallons used to do, and I had to pay $1 a gallon for the water I still consider it a worthwhile trade to not be miserable, getting a few hours of poor sleep while salty and clammy, and being able to actually enjoy my time in Black Rock City because I had a bubble of cool air to retreat to.

Using the bigger number you calculated, 5 gallons a day X 14 days is 70 gallons, which is 10 reliance 7 gallon water containers of water, which take up a footprint of 10 square feet on a van floor. Even if you had to pay 25 cents a gallon for all 70 gallons of water, that is $17.50 to keep cool in the desert for 2 weeks. If you can’t carry Seven gallons at a time, you will need 14 Five gallon plastic jerry cans which will have a footprint of about 2.5×4.5 feet. If you rig is anything less than a minivan you will need to prioritize, you will need to decide if being this cool is worth the overhead in space and strain on a small car. If your rig is a regular cab van this amount of space is doable depending on your layout. When you arrive at your spot you put the containers outside. On the return trip these containers should be empty, and you’ll be able to tie them to the exterior of the van, if you’re concerned about the few percent increase in wind resistance of having them strung on the roof – string them to the back.

You will need to haul this water to your spot, and it will weigh in at about 560 pounds. 560 pounds IF you’re not resupplying for 14 days – I’m using this number because this is the maximum duration you can stay on most BLM land in the United States. Don’t feel like you’re overloading your CARGO van, even if it’s an extended cab van built to be a micro-roadtrek – the van is designed to haul this load all day everyday!

Less than $20 to stay cool for 2 weeks of Vandweller boondocking in the desert, and that’s if you have to pay for the water.

The water containers are the most expensive part of this equation.