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Open Roads Forum  >  Truck Campers

 > Sleep with warm fresh air in the TC using a heat exchanger

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RickW

Sacramento CA

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Posted: 01/23/12 01:00am Link  |  Print  |  Notify Moderator

How many times has someone on RV.NET asked how to introduce fresh air to reduce condensation, remove combustion products and still conserve heat (furnace energy) when sleeping in the TC when it is cold outside? I never cared for the open the hatch and wear a hat solution.

The answer for me has always been an air to air, cross flow heat exchanger. They exist for homes in cold climates (expensive) but they don't exist for a TC. Being a typical DIY TC owner, I decided to just build one myself (actually I had to build 3 prototypes first).

The theory is that heat from the warm exhaust air is transferred to the incoming cold outside air across flat metal plates aligned in an alternating crossing pattern stack to produce cross air flow.
I made a small frame out of coroplast with the flutes aligned at a diagonal and attached aluminum foil to make one plate.

[image]

Plates are stacked in an alternating flow pattern to form the heat exchanger stack.

[image]

The heat exchanger and two 12 volt computer fans are mounted at one end of a box that fits through the slide window. One fan sucks, the other blows. [emoticon] The other end of the box has the air inlet and outlet.

[image]

[image]

Place the box through the window, turn on the fans and warmed outside air comes inside and stale inside air cools and goes outside. Short hoses can be used to position the return air inlet and supply air outlet inside the TC.

[image]

The fans both have speed controls. At high speed they measured 2 amps and at low speed, 0.2 amps (for both). I guesstimate at high speed they provide about 10-15 cfm. Low speed about 5 cfm. I estimate it would use less than 2 amp hours of battery at low speed for a night's sleep when boondocking.

I tested the system by heating the inside of the TC to about 70 degrees with an electric heater when it was 45 degrees outside. At hi speed, the system averaged 75% efficient. At low speed about 85% efficient. The warmed incoming air was between 5 to 10 degrees cooler than the camper air.

I also raised the humidity in the TC to about 58% by boiling a pan of water on the stove. After running the exchanger for 3 hours, the humidity dropped to about 32% inside. Outside was 44 degrees. Some of the humidity condensed inside the exchanger on the way out, as expected. Excess condensation should drip out the fan outlet.

None of the steps to make the exchanger were overly difficult, but fabricating the plates and assembling and sealing the exchanger was time consuming.

I left out a few boring construction details for brevity. Let me know what you think.


Rick
04 GMC 1500 4X4X4
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Francesca Knowles

Port Hadlock, Washington

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Posted: 01/23/12 01:36am Link  |  Print  |  Notify Moderator

Fascinating!
I'm especially interested in the dehumidifying effect...


" Not every mind that wanders is lost. " With apologies to J.R.R. Tolkien

sabconsulting

High Wycombe, UK

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Posted: 01/23/12 02:49am Link  |  Print  |  Notify Moderator

I love that - very clever - I always love anything I can build myself for next to no money that adds functionality to my camper. [emoticon]

The design looks slightly familiar - can it also be used to scrub CO2 in an over-manned Apollo lunar module? [emoticon]

[image]

Another location option might be to fit it to the hatch that gives access to the load bed, though I suppose the ventilation wouldn't be where you wanted it then.

Steve.


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Chief 2

Florida

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Posted: 01/23/12 05:30am Link  |  Print  |  Notify Moderator

I am confused. Where are you picking up the warm outside air when it is 45 degrees outside?


2005 Lance 1181 Loaded
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VintageRacer

Tatamagouche Nova Scotia

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Posted: 01/23/12 06:11am Link  |  Print  |  Notify Moderator

As the warm inside air is blown out, it is used to raise the temperature of the cool outside air that is blown in. it doesn't match the temp, but it raises it, in his example, from the mid 40's to around 60 degrees. That's a nice recovery, but the interesting bit is the exchange of overly moist warm air for dry outside air.

Brian


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sleepy

Oak Ridge,Tennessee

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Posted: 01/23/12 03:52am Link  |  Print  |  Notify Moderator

Well thought out, good design, nice build.... you get an "A+" on this project. This is among the "best" of the best projects.

I'd like to do it to replace the screamer exhaust fan over the stove. Kill two birds with one stone.

Congratulations... this one should be in the TC University.

BTW... please add the "boring " stuff... we all seem to like it on the TC forum.

Sleepy


2003 Lance 1161,/slideout/AGM batteries/255W Solar/propane generator/Sat dish/2 Fantastic Fans/AC/winter pkg
AirFoil, Trimetric, LED lights, Platcat vent heat

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gbopp

The Keystone State

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Posted: 01/23/12 04:37am Link  |  Print  |  Notify Moderator

Great project. Can/will you make plans available?

silversand

Montreal

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Posted: 01/23/12 04:43am Link  |  Print  |  Notify Moderator

Quote:

The answer for me has always been an air to air, cross flow heat exchanger. They exist for homes in cold climates (expensive) but they don't exist for a TC. Being a typical DIY TC owner, I decided to just build one myself (actually I had to build 3 prototypes first).


Rick:

We've got a whole house air exchange system (with the heat transfer elements) and full HEPA filtration on all 3 floors (however, the unit size itself would fill an entire bathroom in a tuck camper). This is an excellent concept for a truck camper application, especially a unit as compact as the one you are using!

Following closely,
Silver-


Silver
2004 Chevy Silverado 2500HD 4x4 6.0L Ext/LB Tow Package 4L80E Michelin AT2s| Outfitter Caribou

ticki2

NH

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Posted: 01/23/12 04:46am Link  |  Print  |  Notify Moderator

Excellent topic , much can be done in this arena . Nice work .


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skipnchar

Topeka or somewhere else

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Posted: 01/23/12 07:43am Link  |  Print  |  Notify Moderator

If I read correctly, you're using Coroplast to separate the CO laden exhaust air from the air blowing into the RV? Have you tested the CO content? Sounds like an ingenious device as long as it's very well sealed and remains so.


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2004 F-150 HD (Traded after 80,000 towing miles)
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US Govt survey shows three out of four people make up 75% of the total population


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