  Heat exchanger tube rows can influence the thermoacoustic instability
behaviour of combustion systems since they act as both acoustic scatterers and
unsteady heat sinks. Therefore, with careful tuning of their thermoacoustic
properties, heat exchangers have the potential to act as passive control
devices. In this work, we focus on (only) the acoustic scattering behaviour of
heat exchanger tubes. We present a comparison of existing acoustic models for
tube rows and slits, models for the latter having the advantage of
incorporating frequency dependence. We then propose a new model that enables
the adaptation of slit models for tube rows. This model is validated against
experiments and Linearised Navier Stokes Equations (LNSE) predictions for the
transmission and reflection coefficients, including phase information. The
model predictions show very good agreement with the experimental and numerical
validations, especially for low frequencies (Strouhal number < 0.5, based on
tube radius and excitation frequency), with mean differences less than 2% for
the transmission coefficients (the reflection coefficient errors are somewhat
larger since their magnitudes are very close to zero).
