Experimental Studies on the Distribution of Air Flows in Air Cooled Steam Condensers

Аннотация

The uniformity degree of the air distribution over the heat-exchange surface of an air cooled condenser (ACC) plays an important role since it determines the efficiency of this surface’s usage. In this paper, this factor at a special stand, where all the main processes of an air flow were simulated, is studied. The typical design of the A-framed ACC was chosen as the basis for the study. Two ACC models differing from one another by the presence of a diffuser after the fan were studied. Each of the models was tested in two versions: with a low-speed electric motor and a high-speed electric motor with a gearbox. In the ACC models, heat transfer surfaces were simulated by a set of flat metal grids with a uniform distribution of square cells. The aerodynamic drag of a set of grids was preliminarily selected so that the Euler criteria were equal for the full-scale object and model. During the tests, the air velocities in front of and behind the grids were measured by traversing, and the velocity fields (isotachs) of the cooling air in these sections were plotted. A condenser with a low-speed electric motor provides the most uniform distribution of cooling air over the heat-exchange surface, while condensers with a high-speed electric motor and gearbox and with a diffuser have significantly greater nonuniformity in the air supply. During the “suction” operation, the flow distribution is more uniform but worse than that for the version with a low-speed electric motor. The effect of the nonuniform velocity field of cooling air on the heat transfer of ACC is estimated. The real condenser module was calculated for various flow and velocity distributions along the tube length. Losses of heat removal due to the nonuniformity of the air flow of the considered circuits can be estimated within 1–3% at a ±50% deviation of the flow rate from the average value.