KAPLEVENT
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Questionnaire

Flow velocity: face, free and vane channels

v_face ≠ v_free ≠ velocity in the channels: three velocities and when each is needed

Face and free areaRectangle of the W × H section; the free area A_free = A_face × k_open is shown dashed.W, mmH, mmA_face = W × H — the whole face areaA_free = A_face × k_open — air passagek_open depends on the profile and pitch of a specificmodel — there is no universal value.
Sections: face A_face and free A_free = A_face × k_open

Short answer: mist eliminator documentation uses three different “velocities”: face, free area and local in the channels. They must not be mixed up.

Three velocities

  • v_face = Q / (3600·A_face) — the average over the face section of the pack; computed by the “Airflow velocity” tool.
  • v_free = v_face / k_open — the average in the free area (the openings between vanes/mesh). k_open is a parameter of the specific model, entered manually.
  • Local velocity in the channels — a data sheet parameter: maximum velocities and efficiency are referenced to it.

In practice

  1. Checking the existing geometry: v_face from Q, W, H — fast and sufficient for a sanity check.
  2. Sizing a section: set a target v_face — the “Required section size” tool.
  3. Comparison with the maximum velocity of a model — only per the data sheet, in the section to which the coefficient is referenced.