Features of numerical modeling of a plate cross-precision air recuperator
The article deals with a study of an open-type cross-flow plate recuperator based on the ANSYS Fluent software module. The analysis of the influence of mesh detailing in the longitudinal and transverse directions on the enlarged thermophysical indicators is carried out. The author presents a comparison of the results of the software calculation of heat transfer through the recuperator plate with the data obtained in an analytical study using the one-dimensional transfer model. Within the framework of the dissertation research, the features of the formation of aerodynamic and temperature fields during the cross movement of the heating and heated air flows were revealed. The analysis of the grid convergence showed that for a plate size of 0.4×0.4 m, the rational number of grid subdivisions in the longitudinal directions is 100. A decrease to 50 cells leads to an incorrect description of heat transfer in the laminar boundary layer, when the exchange processes along the normal to the wall in mainly determined by molecular diffusion. An increase in mesh points in sections perpendicular to the flows leads to a gradual increase in the coefficient of temperature efficiency for the outside air. The author found that the use of criterion equations for solving the problem of heat transfer gives underestimated values of temperature efficiency, while the indicators obtained for different models of software calculation (homogeneous and heterogeneous binary air models) turned out to be almost identical. The use of a heterogeneous model in the future will make it possible to carry out studies of heat and mass transfer in recuperators taking into account the phase transition of steam and the release of heat of condensation. The optimality of generating a grid with prismatic cells not only in the near-wall region, but also in the developed flow zone is confirmed by the fact that temperature fields in the cross-sections of the channel of the recuperator cassette with a thickness of 5 mm develop under conditions of a thermal boundary layer.