Importance

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Abstract

A water-condensing heat exchanger recovers heat from a hot flue gas, subjecting tubes of the heat exchanger to substantial thermal expansion and contraction, and corrosive constituents in the flue gas require that metal tube sheets be thoroughly insulated from the flue gas during operation in a water-condensing mode. The heat exchanger is constructed by heat-forming edge portions of holes in plastic sheets through holes in tube sheets, temporarily plugging the plastic-lined holes to limit diametrical reduction, and entering tubes through the plastic-lined holes sufficiently shortly after unplugging the holes that further diametrical reduction of the holes causes them to grip and fixedly locate the tubes relative to the tube sheets. The method of manufacture also concerns providing a fluroplastic coating, e.g., polytetrafluoroethylene, on the interior elements of the heat exchanger to inhibit corrosion thereof; such coatings are hydrophobic thus allowing falling condensate to be washed away easily.

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First Claim