A node structure (12, 14) for connecting two or more convergent members (16, 26) of a lattice frame to each other and to one or more other members of the lattice frame. The node structure (12, 14) comprises a pair of opposed spaced-apart faces (30) that are substantially planar and substantially parallel to each other. At least one pair of root formations (32) with respective central longitudinal axes define an interior angle between them, those axes diverging outwardly for alignment with respective members of the lattice frame and converging inwardly between the faces (30). An inner connecting wall (34) between the root formations (32) of the pair connects concave-curved inner edges (36) of the faces and extends in a concave curve around the interior angle to join the root formations (32) of that pair.

The present invention discloses a stainless-steel tee-pipe moulding process, cutting out a main pipe and a secondary pipe from the stainless-steel pipe to replace the copper tee-pipe to resolve the problem that the copper tee-pipe is easy to corrode and causes water pollution; meanwhile, the moulding process of the stainless-steel tee-pipe of the invention is different from the traditional integral forming process, and saves more materials and reduces the production cost compared with the traditional integral forming process.

A heat exchanger tube has a tube end having two extended portions substantially opposite the other around the periphery of the tube end, and two shortened portions, each positioned between the two extended portions and substantially opposite the other around the periphery of the tube end. The tube end may be formed by removing opposite portions of the tube by cutting a disc-shaped portion with a generally smoothly curving periphery along a major portion of the width of the tube. Each tube is oriented within an opening in the header wall of a heat exchanger assembly having a header portion integral with a tank portion, such that the tube end two extended portions are oriented substantially perpendicular to the direction of fluid flow within the header and the tube end two shorter portions are oriented substantially in the direction of fluid flow in order to reduce interference with fluid flow.