The heat flow across a joint formed by two concentric cylinders depends not only on the geometrical, thermophysical and surface properties of the cylinders but on the heat flux and maximum operating temperatures. An analysis is presented in which it is shown that, depending on the heat flow direction, the contact may be reinforced or completely relaxed during operation. These results are consistent with previous experimental observations of other workers in this area and recommendations of heat exchanger manufacturers. It is further shown that, because of the interdependence of the heat Aux and the contact pressure, the exact nature of the correlation used for the solid spot thermal conductance becomes relatively unimportant.