摘要 |
A series of tubes wound in spiral, spaced relation in pressure contact with the next inner tube or a central cylinder to form, between them, a spiral path for one liquid flowing upwardly in the space between the tubes, while another liquid flows downwardly in the tubes. The outermost tube may be enclosed by a sheath in pressure contact therewith, while several sets of tubes, separated by corresponding sheaths, may be utilized. The diameter of the tubes may be varied for the sets to compensate for the greater length of tubes at an outer position, so that an approximately equal time of travel from one end of the tubes to the opposite ends may be obtained. The spacing between the successive turns of the coils is preferably a distance corresponding to one half the diameter of the tubes.
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