From: mung_me@att.net   
      
   On 2/3/2013 6:17 PM, Morris Dovey wrote:   
   > On 2/3/13 11:53 AM, j wrote:   
      
   OT for a moment...   
      
   My sewer line here is blocked, I've tracked it with great difficulty, by   
   digging and looking. It takes a right into my backyard and then another   
   right so it circles the house.   
      
   So, I found the line is blocked between the sidewalk and the street. So,   
   we dug down and struck... the new (and unused) gas line, 6" under that   
   the crushed sewer pipe.   
      
   I call the city at 3PM and they tell me to file a damage report with the   
   gas company. However at 5PM someone from the city shows up and says the   
   city will fix it by Sunday.   
      
   Just now, someone came out and marked the water and sewer lines, the   
   ones that I had no idea where. I've never seen anything like it, he had   
   a collapsible metal divining rod and just walked across the pavement. It   
   snapped to the side and he marked. In fact, he marked all the water and   
   sewer lines, just like that, in no time. And it matches exactly.   
      
   So, I am thoroughly impressed with the speed and psychic powers of this   
   city!   
      
      
      
   >   
   >> It seems to me that you must be close to optimum, as far as getting the   
   >> amount of heat out of this. That you can generate heat with so little   
   >> light is striking.   
   >   
   > I don't think I'm as close as I'd like to be - but future improvements   
   > are likely to be in smaller increments.   
      
   It would seem so, the base heater designer is very good.   
   >   
   > Coating the back plenums with high gloss paint might make a significant   
   > improvement to air flow. Back when I was building panels I didn't think   
   > so, but I'm still learning - and think this worth trying.   
      
   small increments, as you said.   
   >   
   > The shape and spacing of the fins can almost certainly be improved, but   
   > I think that'll need to be done by someone with the right combination of   
   > physics/math/geometry skills - which I don't have. There's a gentleman   
   > who lives in southern France who might be able to nail this down, but   
   > all my contact info for him was lost when my old HP machine   
   > self-destructed. :-(   
      
   Ouch.   
   >   
   >> A few notes.   
   >>   
   >> I notice that you said a thin coat of gloss worked better than flat   
   >> black. This strikes me as similar to the way selective coatings work.   
   >> The absorption is slightly lower but the re-radiative losses are much   
   >> less. Certainly important in a cold climate.   
   >   
   > There's a lot of room for exploration here. By the time I'd built my   
   > last panel I'd realized that what I'd been calling an absorber shouldn't   
   > /be/ an absorber - that's just the word everyone wants to hear. Ideally   
   > it's purely a reflector. :-)   
      
   Perhaps, re-radiator...   
   >   
   >> I note the distance from the absorber fins to the glazing and the back   
   >> is on the order of a half inch. Larger distance seem to create their own   
   >> air currents and are counter productive, that was not obvious to me!   
   >   
   > Now you're sounding a lot like me. :-) It turns out that there's a lot   
   > of behavior that's best labeled counter-intuitive. My favorite joke on   
   > myself was that my level of ignorance was colossal and growing at an   
   > exponential rate!   
   >   
   >> I also note your point that the object is to heat the air and not the   
   >> absorber! I've made some progress here, IR measurements of my absorber   
   >> (black felt) show it be a good bit cooler than the air between it and   
   >> the glazing. In my collector I'm pulling air from the collector and   
   >> pushing it into the old air vents.   
   >   
   > I think this notion of (as much as possible) heating only the air is a   
   > key concept. AFAICT a hot collector is necessarily a lossy collector.   
      
   That makes sense.   
   >   
   >> The fin rolling "machine" is very interesting. I made a series of jigs   
   >> to form aluminum around the copper risers. That and riveting it all   
   >> together was extremely exhausting. Perhaps some details of the machining   
   >> would be useful.   
   >   
   > It's just a forming press with a cutting blade on the infeed end. My   
   > thought was to use a stepper to pull ribbon from the spool, an empty   
   > spool to ballast a loop of ribbon, and another stepper to measure ribbon   
   > from the loop into the press. A pair of LED/photodetectors would let the   
   > controller sense when to feed from the spool and when to stop feeding   
   > (all copied from some of the early computer tape devices).   
      
   Yowza.   
      
     The inset   
   > detail in the sketch shows the ribbon positioning I actually used with   
   > my manual press.   
      
   I'm struck by the amount off the shelf and cheap technology available.   
   And the Arduinos and the like to control them. Anything is possible,   
   parts you can't get you can send off to the 3D service bureau to get made.   
   >   
   >> I've altered my own solar air collector several times as money and   
   >> experience has allowed. The current geometry is too much depth, but that   
   >> was largely determined by the geometry of the house and the jalousie   
   >> windows. On the plus side the cats love to spend time inside the   
   >> collector (the house side).   
   >   
   > (I'm imagining some very contented cats!)   
      
   Oh yeah, on a cold day it is "the" spot.   
      
      Cheers,   
   Jeff   
   >   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)