Teardrops n Tiny Travel Trailers

I suggest another test , first thing on a cold morning, start the heater and see how much it warms up,the interior in 15 minutes, and then see how long to make a 20 degree temp difference.
Also it would be good to know how warm the water in the tank is after an hour of cooling.
The questions to answer are, is the constraint the radiator or the water heater. You will also get a better idea of how much real impact it will have on a cold night. ( also keep in mind that a couple of warm bodies will also add some heating). Personally I think it is probably fine as is, but it would be nice if it didn't have to run all night.
Tom

MtnDon,
Last night I was thinking that maybe a 10 gal tank would help by increasing the volume (mass) of heated water, thereby maybe reducing the number of heating cycles that would take place. But then again, one would have to understand how much more propane (energy) was used to heat up that extra 4 gals. Then you could compare the operation costs and efficiency for both tanks.

And I agree with the question, "would a larger radiator help..." with the heat transfer?

MtnDon, your usage tests will help with the analysis.

Here is a wild,thought. What would it be like to have this sysem in place to have a lowered heat (say about 60 degrees) for sleeping and having the NuWay stove run all the other times you are awake. To me, that low cost level of redundancy, would be quite viable. The NuWay could bring up the cabin temps quickly in the morning. All this for an added $130.

MtnDon wrote:Further note: It may be that a larger radiator would work better, dissipate more heat. However, (1) that is the one I had on hand. (2) it's size, or at least the 6" dimension is ideal for placing it in front of the shower lip as earlier described.

And two other considerations could be:
1. See page 4 of this link. It suggests for home systems using our discussion project concept, that it uses 140-160 degree water. From the Suburban operating instuctions I see that the optimum temperature is 130 degrees and the relief valve is designed to open at 210 degrees. Therefore we should be able to reach the necessary temps in the RV for this concept to work quite adequately.
http://www.king-electric.com/pdfs/King- ... ochure.pdf

2. Second idea.
See the model of the water to air exchanger for home use. See the way the airflow is over the fins the long way. If we build a sheet metal housing which blew the air across the fins instead of through them, wouldn't the outcoming air be warmer; because it is over heated fins longer.
http://www.king-electric.com/pdfs/King- ... ochure.pdf

I wouldn't go over 130F as you still want to be able to use the hot water without worrying about getting scalded:



Bruce

Point noted Bruce.
And adding an anti scalding valve for other water usage would just add to the complexity of the system.

The default on the Atwood and non adjustable water temperature on gas is 140 degrees, the 120V Hot Rod heater is at 120 degrees but is adjustable to 150. The hot Rod is 675W so about 2200 BTU per hour the gas is about 10,000.

The Suburban gas heter is also not adjustable. It is set at 130 degrees F.

Perhaps there has been some recent change but the manual for our 6 gallon pilot light Suburban water heater states, on page 12... "CAUTION: Temperature setting on control was factory set at low (120F/49C) to reduce risk of scald injury. Setting the temperature dial past the low position will increase the risk of scald injury......."

There is a black plastic adjuster that has settings with Low at one end, Medium in the center and High at the other end of the quadrant range of movement. That does permit adjustment of temperature to quite high temperatures. That's for the basic pilot light model. I have no idea about the other models. Ican easily get the water hot enough to cook fish by immersion.

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Re: the direction of blowing air over the radiator. It might be worthwhile to set up a test and blow air lengthwise. The air would still have to enter at one end and one side and make it through the fins to exit on the other side at the other end. Have to see what difference there is. After all auto cooling systems, my home A/C and other devices like the liquid cooling system on my son's souped up computer all have the air flow directed through the fins. There will likely be an optimum flow rate for best heat transfer. Add to that different fans have better or worse ability to push air through and around obstructions. If the air path is too difficult the air flow can suffer more with some fans than others. Check the static pressure rating of fans as well as their CFM rating (and the dB and amperage). Choosing the best fan can be a challenge.

I will let folks know what I discover , but that may take until next weekend at the soonest.

That is interesting MtDon.
This 2007, (page 6) instruction manual
http://www.livinlite.com/pdf/service/wh ... lation.pdf
says it is not adjustable. But then again, it is 7 years old.
I suppose if this is really that important, one could call Suburban. It is not that important for me right now to make that call.
Hopefully you got a later model and the new ones do have the adjusting knob.

The manual you listed appears to be for a direct ignition version, no pilot flame, just spark ignition. That may be the difference. ??? I have had pilot models in various RV's since the mid 80's. They all had the adjuster like the one I bought a year ago.

That is the only one I could find. Guess I will call the Suburban folks this week afterall. It is something worth knowing.

MtnDon wrote:Re: the direction of blowing air over the radiator. It might be worthwhile to set up a test and blow air lengthwise...<snip>

I don't think that will help. The heat transfer efficiency is all about surface area and you'll have maximum fin area with the air blowing through the radiator.

Bruce

MtnDon,

You mentioned water cooled computers. Several years ago, my stepson and I built several computers with both cpu and gpu cooling. Computer fans don't flow well with much static pressure and the radial fan creates turbulent - non-linear - airflow. The most effective coolers we built had a radiator shroud that spaced the fans away from the radiator. Another time we had fans on both sides of the radiator in a "push-pull" configuration to overcome static pressure. Maybe one or both of these techniques would increase heat transfer.

Take care,
Tom

lrrowe wrote:MtnDon,
Last night I was thinking that maybe a 10 gal tank would help by increasing the volume (mass) of heated water, thereby maybe reducing the number of heating cycles that would take place. But then again, one would have to understand how much more propane (energy) was used to heat up that extra 4 gals. Then you could compare the operation costs and efficiency for both tanks.
.

For us there would be no advantage to the extra 4 gallons. Reason being that the hot water tank has extra foam insulation around 5 sides (can't put extra insulation on the outside face. The extra foam prevents heat transfer from the water to the trailer interior; prevents virtually all heat transfer. The thickness varies from 2 extra inches under the tank to 4 inches on the other sides. The idea was to keep cooler in hot weather. This interior space heating would work about the same as with a 3 gallon tank; the propane would fire up a little more frequently is all the difference. IMO.

aggie79 wrote:MtnDon,

...... The most effective coolers we built had a radiator shroud that spaced the fans away from the radiator. Another time we had fans on both sides of the radiator in a "push-pull" configuration to overcome static pressure. Maybe one or both of these techniques would increase heat transfer.

Take care,
Tom

Thanks Tom. I would like to space the fan away from the radiator with a plenum of some size. I do believe that would be beneficial to air flow. I may try a test. One of my issues with that is the available space, or rather the amount of space I want to use. Compromises will have to be made. We'll soon enough know. Another couple of days and I will hopefully have the new fan and the temperature controller at hand.