I tried the heater core first and got some results that look promising but didn't have enough thermometers to get good readings. I ran the heater core/swampcooler unit and got about a 4 degree difference at 12 noon between the indirect swampcooler 84.8f and also the regular swampccoler 88.9f that I was running at the same time. I did notice running 2 swampcoolers at the same time did reduce the temp in my van to 89f from 94f, to verify I turned 1 swampcooler off and temp started to climb again, I ran the test last week when outside temp was 84f 60% humidity.
I decided to get a 8x8 air to water heat exchanger (55 dollars). This has copper tubing and should work better with water.
The only problem I had was the both that both the heater core and heat exchanger were both too large to make a indirect swamp cooler that would fit in the corner that I have setup for a swampcooler. I built a seperate container for the heater exchanger and ran my test
Todays outside temp as per weather channel at 1:30 pm 98f with 24 humidity
First I just use the water in the indirect container to run through the exhanger. From 12:03 to 1 pm, notice the water temp kept getting hotter 101f as the test went on.
At 1:30 pm I decided to use 5 feet of tubing to connect directly to the swampcooler water reservoir. Note the temperature of the water drop, and stayed consistent below 87 f.
The air intake was from the roof vent located under the solar panel, I had 4" flexible ducting to bring the air into the indirect cooler and then more flexible ducting to take it from indirect section to the swampcooler. I had 4x thermometers to measure the temperatures. The outside temp is accurate, the flexible ducting was hot to the touch and heating up the van. At 2:30pm was the hottest temp I recorded the intake was 116f, the exhanger reduced it to 102f, then it went to the evaporator pads where it got reduced to 90f. The exterior of the heat exchanger was hot to the touch but the copper tubing stayed cool. From the test, the best results from the heat exchanger was when the outside temp was the hottest.
Even though 90f seems high it felt cool to me. The inside of my van was 100 degrees but the humidity was low and the swampcooler was keeping me cool. The swamp cooler I'm using has a very small evaporator pad, so that can be improved. And the 5 feet of flexible ducting I using will heat up the air before it gets to the swampcooler, making it shorter will also improved performance. On a hot day like today the swampcooler by itself would be struggling to keep me cool, I would have to pour water on me to try and stay cool.
From the test I done, using a heat exchanger/ heater core to cool the air before it gets to the evaporator pads does work. The cooler the air before it hits the evap pads the better your results. The only drawback is the size problem but I will have to do some modifications to get it to fit in my van. One thing I found out was the small 12 volt water pumps will push water at least 5 feet without any problem, that opens the possibilities of keeping cold water in a cheap 12 volt fridge and pumping it into the indirect cooler to cool it even more.
air exhanger
time intake exhaust water swamp cooler exhaust
12:03 114f 105.7f 99.7f 90.8f
1 pm 112.4f 105.3f 101.3f 90.5f
1:30 116f 103.3f 87.7f 90.6f
2 pm 115.5f 104f 86.8f 90.3f
2:30 116.2f 102.8f 86f 90.4f
3 pm 107.5f 98.6f 85.3f 89.7f
4 pm 104.5f 96.4f 83.2f 87.1f
5 pm 95.4f 93.2f 84.8f 88.5f
temp readings
indirect section shown, actual swampcooler is 5 feet away connected with 4" flexible ducting and 5 feet of plastic water tubing.
