Simplify assumptions on the mathematical calculation model of the elliptical tube condenser
Establishment of the air condenser unit structure model. Physical model. The radiator of a domestic 1000MW direct air-cooled unit is composed of 80 air-cooled units, and each air-cooled unit includes a sub-radiator and a fan. Each sub-radiator is structurally composed of several tube bundles with elliptical aluminum tubes and rectangular aluminum fins, and they are arranged in a single row. The air flow and heat transfer outside the finned tube tube have periodic characteristics along the length of the tube. The geometric unit containing the fin can be selected as the calculation area for geometric modeling. Since the finned tube is an axisymmetric figure with the long axis as the symmetry axis, the simplified model is to eliminate the influence of the inlet effect and the backflow phenomenon at the outlet boundary on the calculation results. The inlet area and outlet area are respectively extended. The mathematical model of the overall model, assuming the following simplified assumptions for the mathematical calculation model of the elliptical tube condenser, the heat transfer and flow in the calculation area are steady; the air in the calculation area is incompressible gas; the elliptical base tube is not considered Contact thermal resistance and radiation heat transfer between the fin and the fin; the top of the runner is insulated.
Boundary conditions: The physical parameters of the fin: the density is 2719kg/m, and the entrance of the calculation area for the specific pressure heat setting is the velocity entrance boundary condition, and the exit is the free exit boundary condition; the base tube and the fin adopt their own heat conduction and surface convection heat transfer Coupled heat exchange method; assuming that the steam in the base pipe is saturated water vapor and the wall surface of the base pipe is a constant wall temperature boundary condition: numerical simulation of the heat transfer characteristics of the heat dissipation unit of a 1000MW direct air-cooled unit; the top section of the model is the adiabatic boundary condition; the rest The geometric surface is set as a symmetry boundary condition. Calculation method Use Gambit software to mesh the calculation model of the radiator, adopt a structured non-uniform multi-block structure grid, all the grids are hexahedral structure, and the fluid grid at the entrance and exit is partially refined, the total number of grid cells About 1 million. By using different numbers of grids, the independence of the grids is tested, and the number of grid cells divided can eliminate the influence of grid density.
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