Abstract: A pin fin heat exchanger including a pin fin heat pipe. A main tube of the heat pipe may divide at the evaporator end into a number of pin fin evaporators, each having fluid entrances and exits to the main tube; and at the condenser end into a number of pin fin condensers, each having fluid entrances and exits to the main tube.

Abstract: A circlip (8) comprises a band of material forming an incomplete ring, and has curved bearing surfaces (10, 11) at opposite ends of the major transverse dimension of the band. The major transverse dimension is generally oriented at less than 90°, and preferably a small acute angle &agr;, to the central axis A of the ring in the unstressed state of the circlip (8).

Abstract: A heat exchanger element comprises an outer tube (11), an inner tube (12) within the outer tube and a first fluid flow path for a first heat exchange fluid formed between the inner and outer tubes. A second heat exchange fluid is in heat transfer relation to the outer surface of the outer tube and/or the inner surface of the inner tube. A sleeve (13) is provided within the first fluid flow path between the inner and outer tubes. The sleeve defines an outer interface (16) with the inner surface of the outer tube and an inner interface (14) with the outer surface of the inner tube. Generally longitudinal grooves (16,17) are provided at each interface to provide together the first fluid flow path.