The air heaters used for heating blast furnace blast have recently undergone a number of design changes, which has affected their key thermal performance indicators. There are established temperatures at which settled operating conditions show sufficient technical and economic performance. Deviation from the conditions by increasing the temperature of the hot blast entails negative consequences of a different nature, which ultimately makes it unfeasible from an economic point of view. New design solutions for air heaters must be determined by maximum temperatures, which affects the service life of the equipment and system. Consequently, the development of the heat transfer surface of the nozzle plays an important role in solving the problem. Increasing the reliability of the apparatus and achieving high thermal performance indicators will result from improving the design of regenerative devices. By applying a mathematical model to the calculation of flows in a system of channels of an arbitrary given structure, calculations of coolant flows through the channels of a blast furnace heater nozzle were obtained. Modeling of flow non-uniformity at the inlet to the nozzle was carried out for different pressure fields at the inlet to the nozzle with horizontal channels. The results of the specified pressure fields at the entrance to the system and the results of calculating the mass flow rates of the coolant through vertical and horizontal channels are presented. It has been confirmed that the pattern of the pressure field at the inlet to the nozzle and the velocity field in the supply vertical channels are different due to the mutual influence of adjacent vertical channels because of their being connected into a single system by horizontal channels. Calculations have confirmed that horizontal channels do not actively participate in the heat exchange process. For better efficiency, it was proposed to make horizontal channels not along the entire height of the nozzle, but only in its upper and lower layers.