Method of making coils

摘要

A slit fin heat exchanger is formed by wrapping slit fin tubing into a flat coil having two spaced rows of tubing. The flat coil is located on mandrels which are rotatable about spaced parallel axes with the mandrels and axes initially being in the same plane. A piece of expanded metal is placed between the two rows. The mandrels are rotated about their axes in opposite directions which shifts the plane in which the coil is located. The shifting of the plane of the coil moves a portion of a first row of the coil into contact with a planar portion of a platen and the second row of the coil into a nesting relationship with the portion of the first row which is in contact with the planar portion of the platen and the piece of expanded metal. Continued rotation of the mandrels causes folding of the portions of the coil which extends the area of nesting. The folding takes place through up to 120 DEG and the ends of the first row of the coil contacts a portion of the platen causing the formation of a knob at the end of each coil. The piece of expanded metal serves to support the coil such that tube supports are not necessary.