In the hypothesis of a severe accident on a pressurized water nuclear reactor, the aerosols created and carried by a gas flow consist of steam and incondensable gases which can settle by different mechanisms on the walls of the primary circuit. In particular, in the tubular bundle of steam generator, on contact with the wall cooled by the water flowing at the outside of the bundle, the aerosols are transferred and fixed on the wall by thermo and diffusiophoresis. A model of the deposition on a vertical cylindrical tube based on the mass and energy balances allows us to show that the efficiency of the deposit depends only on two thermohydraulic parameters. The theoretical relations of the efficiency applied to the Institut de Protection et de Surete Nucleaire experimental program "Tuba diffusiophoresis" agreed with experimental results and confirm that the efficiency of deposition by thermo and diffusiophoresis must be evaluated simultaneously rather than independently.