scope:

Geometry and materials

The method applies for tube bundles (and some connected components) under the following conditions:

- The whole tube bundle (as the main component of a shell and tube heat exchanger) is axisymmetric.

Permitted deviations from the axisymmetry are defined and limited below.

- Each tubesheet (also called "plate", subscript P) has only one central tubed area (nearly circular).

Within the tubed area there are permitted small unperforated tubesheet areas, e.g. for pass partitions and tie-rods.

The outer boundary of the tubed area, does not need to be exactly circular, but it shall be approximately circular.

- The tubesheet thickness e_P and the pitch p are the same (constant) for the whole tubed area.

Where there is a second tubesheet, the thickness may be different, but again constant.

- Outside the perforated area the plate has an unperforated area.

The boundary of this unperforated tubesheet area and any additional areas within the tubesheet shall be circular.

- All (inner) tubes shall have the same cross section d_T.e_T and shall be manufactured from the same material.

- For tube bundles with two tubesheets all of the tubes have the same straight length L_T; no tie rod shall be connected to both tubesheets. (For a tube bundle with only one tubesheet the lengths of the curved tubes may vary. If a tube bundle with two tubesheets has curved tubes, it shall be calculated as a U-tube type, where each tubesheet is calculated separately.)

- The width of the untubed rim should not be too large:

λ_R,max ≤ 0,30

- The geometry should be approximately axisymmetric:

λ_R,min/λ_R,max ≥ 0,20

- The tubed area may be calculated as a homogeneous weakened plate:

N_T ≥ 20

- For vertical tube bundles its weight need not be taken into account, if the following formula is true:

- The tubesheet thickness should be within the range:

0,005 ≤ e_P/d₁ ≤ 0,50

With some caution, the method may be used outside of the conditions listed above.