摘要 |
A gas delivery pipe for transmitting a gas, the pipe comprising: a wall defining a lumen of the pipe; an inlet aperture through which gas flows into the pipe; an outlet aperture through which gas flows out of the pipe; wherein the pipe has an index, SI, characterizing a degree to which the pipe is serpentine that is equal to an integral of an absolute value of changes in angle of direction that a unit vector tangent to a midline of the lumen undergoes in moving along the midline from the inlet to the outlet aperture, which integral has a value greater than or about equal to 180°.
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