Oblon, Fisher, Spivak, McClelland & Maier
Heat transfer tubing for natural gas evaporator
 A heat transfer tube for a water-spray-panel evaporator for the gasification of liquefied natural gases which includes a tube having a pair of planar members each projecting outwardly from its peripheral surface, radially with respect to its longitudinal axis and extending longitudinally along such axis, and an internal fin disposed within the tube and having at least three fin members each projecting radially with respect to the longitudinal axis to provide a helical formation extending along and about the longitudinal axis, the helix of the helical formation contacting the internal wall of the tube in a pressure-fitting relationship. The heat transfer tubes can be assembled to form a panel evaporator. The method for fabricating such heat transfer tubes and assemblies is characterized in that the above pressure-fitting relationship is established by drawing the tube alone to reduce its internal diameter until the helix of the helicoid is abutted against the internal wall of the tube. 
Kobe Steel, Ltd.
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Takayoshi
Asami