| http://www.w3.org/ns/prov#value | - A heat exchanger of thermoplastic materials, e.g. polypropylene, comprises two spaced-apart headers interconnected by an extruded board comprising a plurality of tubular passages extending from one end of the board to the other; each header having a longitudinal groove in its exterior surface and a plurality of holes spaced along the groove, interconnecting the groove and the interior of the heade
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