Abstract: Improved method and apparatus for making finned tubing from difficult to work materials such as titanium and stainless steel uses spaced sets of finning discs on a plurality of arbors to form a tube against a mandrel having different diameters under each set of discs. By forming the tube fin tips to their final O.D. in a first disc set and by deepening their roots to bring the fins to their final height in a second disc set, tubes with higher fin counts and/or higher fin heights can be achieved than were formerly possible. The process of separately cold working the tips and roots also permits tubes to be made which are dimensionally identical to prior art tubes but with higher quality and productivity since tube stresses are greatly reduced. An improved titanium tube is also disclosed which has at leasts 26 fins per inch, a fin height of at least 0.034" and an outside to inside surface area ratrio of at least 3.0.

Abstract: Improved heat transfer tube and method of making same has mechanical enhancements which can individually improve either the inner or outer surfaces or which can cooperate to increase the overall efficiency of the tube. The internal enhancement, which is useful on either boiling or condensing tubes, comprises a plurality of closely spaced helical ridges which provide increased surface area and are positioned at an angle which gives them a tendency to swirl the liquid. The external enhancement, which is applicable to boiling tubes, is provided by successive cross-grooving and rolling operations performed after finning. The finning operation, in a preferred embodiment for nucleate boiling, produces fins while the cross-grooving and rolling operation deforms the tips of the fins and causes the surface of the tube to have the general appearance of a grid of generally rectangular flattened blocks which are wider than the fins and separated by narrow openings between the fins and narrow grooves normal thereto.

Abstract: Improved method and apparatus for making finned tubing from difficult to work materials such as titanium and stainless steel uses spaced sets of finning discs on a plurality of arbors to form a tube against a mandrel having different diameters under each set of discs. By forming the tube fin tips to their final O.D. in a first disc set and by depending their roots to bring the fins to their final height in a second disc set, tubes with higher fin counts and/or higher fin heights can be achieved than were formerly possible. The process of separately cold working the tips and roots also permits tubes to be made which are dimensionally identical to prior art tubes but with higher quality and productivity since tube stresses are greatly reduced. An improved titanium tube is also disclosed which has at least 26 fins per inch, a fin height of at least 0.034" and an outside to inside surface area ratio of at least 3.0.

Abstract: Improved heat transfer tube and method of making same has mechanical enhancements which can individually improve either the inner or outer surfaces or which can cooperate to increase the overall efficiency of the tube. The internal enhancement, which is useful on either boiling or condensing tubes, comprises a plurality of closely spaced helical ridges which provide increased surface area and are positioned at an angle which gives them a tendency to swirl the liquid. The external enhancement, which is applicable to boiling tubes, is provided by successive cross-grooving and rolling operations performed after finning. The finning operation, in a preferred embodiment for nucleate boiling, produces fins while the cross-grooving and rolling operation deforms the tips of the fins and causes the surface of the tube to have the general appearance of a grid of generally rectangular flattened blocks which are wider than the fins and separated by narrow openings between the fins and narrow grooves normal thereto.

Abstract: Improved method and apparatus for making finned tubing from difficult to work materials such as titanium and stainless steel uses spaced sets of finning discs on a plurality of arbors to form a tube against a mandrel having different diameters under each set of discs. By forming the tube fin tips to their final O.D. in a first disc set and by deepening their roots to bring the fins to their final height in a second disc set, tubes with higher fin counts and/or higher fin heights can be achieved than were formerly possible. The process of separately cold working the tips and roots also permits tubes to be made which are dimensionally identical to prior art tubes but with higher quality and productivity since tube stresses are greatly reduced. An improved titanium tube is also disclosed which has at least 26 fins per inch, a fin height of at least 0.034" and an outside to inside surface area ratio of at least 3.0.

Abstract: In the manufacture of tubing, and particularly finned tubing, for use by the heat transfer industry in the manufacture of heat exchangers, annealed ends and lands are desirable in certain applications to facilitate the assembly of the tubes to headers and baffles by expanding techniques. Such spot-annealed portions can be produced on a continuous basis by the described apparatus and method in which the moving tube is passed through a heating chamber which reciprocates on a carriage in the direction of tube movement. The heating chamber has a pair of power-actuated, current-carrying clamps which grip spaced portions of the tube so as to resistance-heat the tube portion between the clamps. The heating chamber and carriage move with the tube while it is clamped to provide sufficient heating time. The carriage then returns to its starting position. If desired, an inert gas can be supplied to the heating chamber to prevent oxidation and/or discoloration.

Abstract: Improved double wall tubing assembly which is especially useful in heat exchangers of the "coil-in-can" type for solar applications has a double wall construction which insures that a leak developing from a failure in either of the walls will not result in a mixing of fluid external to the outer tube with the fluid flowing internally of the inner tube. An outwardly projecting helical fin configuration formed on the outer surface of the inner tube provides an effective heat transfer medium between the inner and outer walls of the tube assembly while defining a spiral flow channel through which leakage entering through either wall can flow and be detected. A method of making the double wall tube assembly is disclosed wherein a finned outer tube is assembled over a previously finned inner tube. The assembled tubes are then brought into firm mechanical contact by the step of forming the assembled tubes into a coil and/or by expanding the inner tube.

Abstract: In the manufacture of tubing, and particularly finned tubing, for use by the heat transfer industry in the manufacture of heat exchangers, annealed ends and lands are desirable in certain applications to facilitate the assembly of the tubes to headers and baffles by expanding techniques. Such spot-annealed portions can be produced on a continuous basis by the described apparatus in which the moving tube is passed through a heating chamber which reciprocates on a carriage in the direction of tube movement. The heating chamber has a pair of spaced, power-actuated clamps which grip the tubing at the ends of a discrete length portion. The heating chamber and carriage are moved with the tube while it is clamped to provide sufficient heating time to anneal the discrete length portion. The carriage then returns to its starting position. Heating of the discrete clamped tubing portion can be by a resistance technique through the clamps or by other techniques such as induction heating or gas radiant heat.

Abstract: Improved double wall tubing assembly which is especially useful in heat exchangers of the "coil-in-can" type for solar applications has a double wall construction which insures that a leak developing from a failure in either of the walls will not result in a mixing of fluid external to the outer tube with the fluid flowing internally of the inner tube. An outwardly projecting helical fin configuration formed on the outer surface of the inner tube provides an effective heat transfer medium between the inner and outer walls of the tube assembly while defining a spiral flow channel through which leakage entering through either wall can flow and be detected. A method of making the double wall tube assembly is disclosed wherein a finned outer tube is assembled over a previously finned inner tube. The assembled tubes are then brought into firm mechanical contact by the step of forming the assembled tubes into a coil and/or by expanding the inner tube.

Abstract: Improved heat transfer tube has radial longitudinal fins on a central core and radial transverse fins on its exterior surface. The composite tube is made by the steps of inserting a longitudinally finned core member inside a smooth surfaced outer tube and then subjecting the outer tube to an external finning operation which produces external fins on the tube while reducing the internal tube diameter of the tube sufficiently that the tube will be firmly mechanically bonded to the finned core member.