heat transfer plates

bill clinton_3

fin dropping tube

I had experience with this, dang!, a quarter of a century ago when I was in the process of becoming rich and famous in the solar industry. Designed, manufactured and marketed my own solar collector using aluminum snap fins very like those being discussed here. Had them extruded by Reynolds Aluminum with specific orders on maximum size of bundles for shipping. They ignored those specifications on one order and sent a huge pallet of fins all bundled together. The weight and the jouncing around created stresses that spread the channel open. When 1/2" copper tube (pex wasn't around) was inserted, it fell out.

Those problems with tube falling out may be due more to the handling the fins received along the line than to the quality of the fins themselves.

Bill

Mike T., Swampeast MO

"After talking to Dale at Thermofin, I got the impression that the heat transfer with the fin was more effective than with aluminum sheets due to better contact, so that the heat transfer by conduction is increased and that more heat is lost to inefficient convection with the sheets. What do you think?"

The more the conduction enhancing product intimately contacts the tube and the more FINAL surface (the radiant panel) it contacts and the more the tube "wants" to conduct in the first place the more heat is extracted from the water running through the tube.

ALL ELSE BEING EQUAL, in two systems of idential output, the one with greater conduction will operate at a lower temperature. In other words, it is theoretically possible to use the exact same amount of tube either bare or conduction enhanced to receive the same FINAL output by changing ONLY the temperature of the water. In reality, the difference in temperature required is impractical as the water would have to be EXTREMELY hot and under EXTREME pressure to prevent it from becoming steam.

INSTEAD, you manipulate OTHER factors as well, chiefly tube SPACING. By tightening the spacing you need more tube, but the length of a single run is limited by its pressure drop, so you wind up with more runs AND/OR larger tube.

If you reduce the tube size when using plates, you still have to keep the tubing lengths such that they can carry the same amount of heat, i.e. they become relatively shorter because there is less heat contained in the tubing to begin with. If you just think, "well, I'll just move the water through the tube faster", think again. Because of the way resistance to the flow of a fluid through a tube works, your ability to increase the velocity of the fluid is EXTREMELY limited.

As Noel said, conduction enhancement products DO allow you to use smaller tube and less of it overall--you just have to ensure that the smaller tube can carry sufficient heat to begin with. You still must move the TOTAL amount of heat required within established rules of flow.