Module RBSA

Program features

Both shell-and-tube heat exchangers with two fixed tube plates and U-tube heat exchangers are investigated. The calculation is performed according to TEMA (Tubular Exchanger Manufacturers Association). However, due to the complexity of the problem, the TEMA warranty does not cover vibration damage.

RBSA calculates the vibration excitation of the tubes and the tube bundle by the following mechanisms:

Fluid-elastic instability

The individual tubes of the tube bundle are fluid-elastically coupled to each other via the fluid in between like via springs. Characteristic is a sudden, very large increase in amplitude at a critical flow velocity. The result is short-term damage due to damage to the tube-tube sheet joint, impact of the tubes against adjacent tubes and impact of the tubes against the baffles.

Vortex excitation

Vortex shedding in the interstitial space between the tubes of bundles constitutes a narrow band excitation and is treated in the literature as a periodic excitation at the vortex resonance frequency. The consequences are long-term damage due to the impact of the tubes against the baffles, damage to the tube-tube sheet joint and fatigue fractures.

Turbulence excitation

A fully developed turbulent flow normally prevails in the tube bundle, which leads to a constantly changing application of force to the tubes by spatially and temporally fluctuating pressures. The tubes react to the turbulent excitation with irregular low amplitude vibrations. This can result in long-term damage due to abrasion and wear of the tubes on the baffle plates.

Amplitudes as a function of flow velocity
Source: VDI Heat Atlas, chapter O2

Price: on request

The module RBSA can be used stand-alone, but is also part of the programs WTS, KOND and VERD. It is used for shell-and-tube heat exchangers with U-tube and with 2 shell-side passes (heat exchangers with shell-side longitudinal baffle).

For shell-and-tube heat exchangers with two fixed tube sheets, the vibration calculation is carried out with the GVLV module according to Prof. Gelbe as an addition on the basis of the VDI Heat Atlas .

You cannot use RBSA for heat exchangers with Disc and Doughnut baffles

see also:

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