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One thing you might consider is a way to enhance the thermal transfer
efficiency by lowering the thermal resistance. If you plan to run
copper pipe through the flue consider attaching it to the surface. I
have used metal filled epoxy to glue copper tubing to stainless. It
worked well. I was using this as a condenser in a home made soxhlet.
In your case there may be a problem with mismatches in the coefficient
of thermal expansion between the copper, the epoxy and the iron of the
tank which may crack the epoxy (I am thinking outloud and do not know
for sure but it is a possiblility). I think the glass transition
temperature of the epoxy would be somewhere around 80 deg C or so but
you may be ok fer a domestic hotwater application. If I was doing this
I would line the surface of the flue with copper pipes glued in and
then fill the hollow space remaining in the center with glass fiber to
eliminate convective air currents up the middle which would rob heat
from the system.. Just a thought. Joe Zeke Yewdall wrote: On the positive side, circulating hot water through the flue should increase heat transfer rate considerably compared to the original design as an air to liquid heat exhanger. But the hot water from the collectors are also much lower temperature than flue gasses. I'm interested in hearing the results too.On 9/28/05, Tom Scheel <[EMAIL PROTECTED]> wrote:The Polaris flue is a 2" diameter heat exhanger. That is how the Polaris achieves 95%+ efficiency ratings. That is the good news. The bad news is that the source of that heat is that 100k+ BTU gas burner you tossed out. So you will not get the short recovery times. What is your square footage of collector? (you would need roughly ten 4'X10' panels to match the oringal 100k BTU (not suggesting you do that, especially given that your heat exchanger can't exchange that much heat)). You will need to move more GPM (gallons per minute) than "normal" becuase of the large flue size. And your post identified the biggest problem, your surface area per volume is low (surface area=good). All of that said, I can't say it won't work. Please update on your progress/results. Hi I have been following this thread. My plan for the heat exchange between the solar collector and the potable hot water system is to modify a discarded gas fired Polaris hotwater heater. The tank of this hotwater heater is made of stainless. I have pulled out all the gas burner guts out of it, made a plate to close off the bottom of the heater end. I hope to acheive the heat tranfer by circulating hot water from the collectors throught the flue of this tank. this setup does not leak but I am not sure how well it will work as a heat exchanger as the surface area of the flue is not all that large. stan Radiance Heating and Plumbing, Inc. (ROC 204149,204150) Tom Scheel 928-380-6294 _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/_______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/ |
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