GB901321A - Improvements in or relating to finned tubes for heat-exchangers - Google Patents

Abstract

901,321. Finned tubes for heat exchangers. BROWN & CO. Ltd., JOHN, and ROBERTSON, G. D. Feb. 9, 1961 [Nov. 9, 1959], No. 23624/59. Class 64 (3). [Also in Group XXVIII] An aluminium tube for use in a heat exchanger has fins formed by passing the tubes through holes in a number of metal sheets, those parts of the tube between the fins each being encircled by a number of metal collars having nested abutting faces. Preferably, the collars are of materials having different tensile strengths and thus different resistances to radial distortion. In the embodiment shown in Fig. 1, a tube 10 is encircled between adjacent fins 12 by an aluminium or aluminium alloy collar 17 having an outer conical face of 45 degrees angle, said face being embraced by an internal conical face of a collar 20 of mild steel. A washer of aluminium may be disposed between the mild steel collar 20 and the adjoining fin in order to prevent electrolytic corrosion between these parts, Fig 2 (not shown). In a further embodiment, see Fig. 3, each part of the tube between adjacent fins is encircled by a mild steel collar of channel section, the conical inner faces 26 of which converge as they extend towards the web portion 7 and abut the inner faces of a mild steel ring 27. In a further embodiment, Fig. 4, not shown, the channel section ring is replaced by two aluminium rings of triangular crosssection. In these embodiments, the angle of conicity of the abutting faces is in such a relation to the angle of friction that the faces slide over one another when the collars are subjected to radially-directed pressure. In a further embodiment, Fig. 5, each part of the tube between adjacent fins is encircled by an aluminium collar 30 of rectangular cross-section which abuts against each fin and which is itself encircled by a mild steel collar 31 of smaller axial width. The tube 10 is expanded against the encircling collars and fins, which are lightly pressed together, by the passage through the tube of a drift of larger diameter than the internal diameter of the tube. The final assemblage comprises two header tanks 35, 36 between which extend a number of tubes 10 threaded through the fins 12. The main portion of each fin may be slotted and the metal bent out as shown at 42 so that air flowing between the fins is subjected to a scrubbing effect.