| Ambient winds seriously affect the thermo-hydraulic performances of indirect dry cooling system, so it is of use to optimal design of the indirect dry cooling system based on the study of wind effects on the thermo-hydraulic performances of the air-cooled heat exchanger and cooling tower. The research of geometric construction of cooling tower, efficient arrangement of heat surface of air-cooled heat exchanger and optimal layout of tower group are achieved, the computational models of air-side fluid and heat flows coupled with the performance of air-cooled heat exchanger and condenser are developed. The velocity, pressure and temperature fields of cooling air at various wind speeds are presented, and the air mass flow rate, heat rejection and outlet water temperature of the air cooled heat exchanger are obtained. The results show that the height to diameter ratios of tower can influence the thermo-hydraulic performances of indirect dry cooling system severely through the optimization study on the geometric construction of cooling tower, especially at a high wind speed. The dry-cooling tower with a low height to diameter ratio is superior to that with a high ratio in thermo-flow performances of indirect dry cooling system at high wind speeds.In order to fully use the characteristic that the thermo-hydraulic performances of windward cooling deltas are best and the lateral cooling deltas are worst, the elliptically arranged heat exchanger and triangularly arranged heat exchanger, which are different with the conventional circularly arranged heat exchanger around the circumference of tower, are proposed. The effects of minor axis to major axis ratios on the thermo-hydraulic performances of indirect dry cooling system are invested, the results show that the elliptically arranged heat exchanger with a small ratio of minor to major axis is superior to that with a large ratio in thermo-flow performances of indirect dry cooling system at high wind speeds when the major axis is configured to face to ambient winds. For the indirect dry cooling system with triangularly configured air-cooled heat exchanger, in the absence of winds or at low wind speeds, the non-uniformity of the air inlet results in an increased air flow resistance, so the thermo-flow performances of the indirect cooling system with the triangularly configured air-cooled heat exchangers are inferior to those of the dry cooling system with the circularly configured air cooled heat exchanger. When the wind speed exceeds 8 m/s, ambient winds play dominant roles in the airflows of the indirect dry cooling system. For the triangular configuration of the air-cooled heat exchanger, more cooling deltas can face the wind directly, so better thermo-flow performances can be achieved for the indirect dry cooling system, especially in the wind direction of 180°. The indirect dry cooling system with elliptically and triangularly configured air-cooled heat exchanger can be applied to the region with the strong prevailing wind all year around.Base on a representative two-tower layout, the thermo-hydraulic performances of indirect dry cooling system are investigated with the tower spacing to diameter ratios from 0.1 to 3 and at various wind speeds. The results show that the impacts of tower spacing on thermo-flow characteristics of natural draft dry cooling system depend on the wind speed and the arrangement of towers. The towers arranged in line are superior to staggered and side-by-side arrangements. When the tower spacing to diameter ratio is lower than unity, the conspicuous interaction between two towers will deteriorate the thermo-flow performances of natural draft dry cooling system. |
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