[en] Calculation technique obtained on the basis of the anisotropic porous body model for evaluation of the effect of the stationary natural convection in liquid metal heat exchangers of the BN type reactors is presented. To reveal the effects connected with the action of natural convection, the heat exchanger calculation model is idealized, namely: transition modes of heat exchangers operation are not considered, in calculations no interrelation of intertube space and the reactor vessel is indicated, only turbulent motion of the coolant in the intertube space is considered. It is shown that the effect of natural convection in the intertube space of such heat exchangers noticeably shows up at the Froude temperature number value Fr <= 0.05. This effect taken into account results in weakening of of calculation temperature non-uniformities of the tube bundle. It is shown that the complicated complex Asub(z)xFr (Asub(z)-volumetric resistance coefficient in longitudinal direction) simulation in some cases gives somewhat better results than the Froude number simulation