Installing Fans to back of Refrigerator

[lemley]

Originally Posted by BigAl

If I remember correctly, I saw in a manual years ago that the back of the propane fridge is supposed to be close to the wall of the trailer so that the convection air current has to pass over the tubing on the back of the fridge. With the curve in the body of our trailers it is not possible. A really good fix would be to install a baffle a few inches from the tubes starting above the gas valve and extending up to near the top of the fridge. Install your fans at the bottom directing the air flow up the back of the fridge. If I pull my fridge, that is what I will try.

I agree wholeheartedly that the chimney arrangement is the best way to achieve good cooling while minimizing the amount of power used by the system. In my study to understand the operation of the absorption refrigerator, I found that the more heat that can be exchanged at the finned heat exchanger at the top of the refrigerator, the better the system will cool. The most energy efficient way to get the air to pass through the heat exchanger is with a chimney. You let convection to do work of drawing outside air over the exchanger.

In a square box trailer, it's fairly easy to achieve the chimney design that gives the convection. But in the Airstream we are driving a square peg into a round hole. In my trailer in particular, the vent on the top of the trailer is actually inboard from the plane of the back of the refrigerator. While the chimney is far to wide at the bottom, it is a bit too narrow at the top. That leaves a fairly small slot for the convection air. That's the reason I went with the fans. They burn 12 volt power and thus are less energy efficient, but they do actually get the job done. And they get it done well. At this moment, the outside air is 98 degrees, the inside temperature of the Airstream is 84. and the Airstream refrigerator is 39.

I actually gathered quite a bit of data from my setup before making the decision that I did. I have a dozen trials where I varied what I could and then measured the temperatures on the trailer skin, at 5 different points in the absorption system, and inside the refrigerator. I did not introduce a chimney. That may work equally well or better. But I went where the data led me.

For a decent discussion of the operation of the absorption refrigerator, see https://en.wikipedia.org/wiki/Absorp...itial%20states.

[lemley]

One thing this thread has made me ponder... Should I consider an air intake vent from the bottom of the trailer? If the reefer intake vent is in the sun, that side of the trailer is very hot, so the air is probably heating a bit as it enters the trailer. The air below the trailer is significantly cooler (at least the dogs thing so), so that would give a better temperature differential. There is already a 1.5" hole there for a condensate drain. Perhaps I should do a bit of experimenting and data gathering with that...

[field & stream]

It has been referred to earlier, but Airstream doesn’t always follow installation guidelines from Dometic and leaves large dead air spaces besides and above the fridge. Don’t know about other models, but these gaps were a significant issue on my 16’ International. These are quick and easy to fill with either rigid of soft insulation.

[hmthomas]

As a mechanical engineer, I started with the simplest solution without getting deep into analysis. I bought a Titan Motorhome Fridge Fan (twin 12cm waterproof) on Amazon and mounted it just inside the lower (intake) vent. I tapped into the existing fan power wires and mounted the new control next to the existing fan control behind the stove top. It runs quit at night and I can turn on both fans (old and new) on hot days in the sun.

[ITSNO60]

Originally Posted by hmthomas

As a mechanical engineer, I started with the simplest solution without getting deep into analysis. I bought a Titan Motorhome Fridge Fan (twin 12cm waterproof) on Amazon and mounted it just inside the lower (intake) vent. I tapped into the existing fan power wires and mounted the new control next to the existing fan control behind the stove top. It runs quit at night and I can turn on both fans (old and new) on hot days in the sun.

I am curious if you see any noticeable improvement. Your installation goes against the recommendation to put the fan at the top side vent pushing air out.

My understanding is that this helps somewhat to encourage the natural convection and mitigate the less than desirable venting when you have 2 side vents as opposed to one side vent and a rooftop chimney. Those with rooftop chimneys usually don't have a problem because that type of venting is superior to 2 side vents as it serves to induce a proper draft on it's own.

[Gene]

Going back into the musty archives of my mind, I recall issues with Dometic fridges having the flame blow out while traveling (or in a wind storm while parked). I think that was solved around 2007 with a baffle added and your fridge should have one. If it doesn’t, something worth checking just in case it does affect your issue. My Airstream was built in the summer of 2007 and did have the baffle, but perhaps yours does not.

[crispyboy]

When I bought my trailer used the refrigerator cooling was awful.
Here's what I did:
1.) I pulled out the refrigerator and built the interior wall out with some aluminum angle and sheeting. This gave me a continuous vertical wall behind the refrigerator. 2.) I put some batt insulation above the refrigerator to take up the dead space.
3.) I put a 6" computer fan on the interior of the roof vent. I only turn on the fan when first starting the refrigerator for quicker cool down or if that side of the trailer is parked in the sun.