A theoretical study has been conducted to investigate the effect of flat bar supports on the dynamic response of a heat exchanger U-tube. The tube was modeled using 3-D, six degrees of freedom per node beam finite elements and excited at its lowest three natural frequencies. The equations of motion were integrated and the time response was analysed using a Fast Fourier Transform Algorithm. The modal frequency and dissipation contributions were determined and the effects of support friction and clearance and excitation magnitude were investigated.