[en] For the purpose of studying the processes in fast reactor heat exchangers the nonuniformly heated liquid flow in a rectangular volume limited by solid side walls and inlet and outlet lattices is numerically simulated. The liquid temperature and its change on solid walls and inside the volume are calculated. At the inlet a parabolic velocity profile has been prescribed for each of the openings. At the outlet the flow rate through each of the lattice openings has been calculated by the boundary layer equation. As calculations show the values of local flow rates through a single opening may vary in wide limits from negative (liquid inflow) to large positive values. In order to evaluate the effects of flow rate and velocity pulsations on the temperature variations in the lattice system the thermal and hydrodynamic problems have been solved. A nonstationary pulsating solution is obtained. The thermal problem with temperature burst at an inlet is considered as well. The outlet temperature spot variation and jet temperature equalization are analyzed. It is shown that the temperature profiles repeat liquid jet oscillations. For the system of lattices with five inlet openings and four outlet ones temperature variations constitute approximately 25%. Pulsations are of periodic character