Method of making an internally grooved and expanded tubular heat exchanger apparatus

摘要

Heat exchanger tubes and heat pipes are simultaneously radially expanded into engagement with heat transfer fins and provided with internal spiral grooving by a generally spherical shaped tool disposed on the end of an elongated mandrel. The tool comprises a spherical segment having helical teeth formed on the exterior thereof and the tool is mounted for free rotation on the end of the mandrel. In forming a finned tube type heat exchanger a series of platelike fins are disposed in alignment with each other with tube receiving openings formed slightly oversize with respect to the outside diameter of the tube prior to expansion. The tube is supported by the fins and is secured at one end by a suitable device such as an expanding jaw collet connected to a hydraulic cylinder for extending the mandrel through the tube. The tube wall is simultaneously radially expanded into forcible engagement with the fins and spiral ridges with intervening grooves are formed on the interior wall surface of the tube to provide enhanced heat transfer characteristics.