Performance Assessment on The Installation Layout of Natural Draft Dry Cooling Towers with Elliptical Arrangement of Radiators

نوع: Type: Thesis

مقطع: Segment: PHD

عنوان: Title: Performance Assessment on The Installation Layout of Natural Draft Dry Cooling Towers with Elliptical Arrangement of Radiators

ارائه دهنده: Provider: Yaser Farahani

اساتید راهنما: Supervisors: Dr. Mohsen goodarzi

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Saidi- Dr. Saghafian- Dr.aghighi

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: سالن کنفرانس

چکیده: Abstract: Crosswind is one of the most significant factors affecting the thermal performance degradation of natural draft dry cooling towers (NDDCTs). By disturbing the airflow field, reducing the heat transfer rate, and increasing condenser pressure, crosswinds can lead to a considerable reduction in power plant output. Given the growing scarcity of water resources and the increasing application of dry cooling systems in thermal power plants, investigating their behavior under crosswind conditions and developing effective approaches to improve their thermal performance have become increasingly important. A review of previous studies reveals that most research has focused on single cooling towers, whereas the performance of towers arranged in multiple layouts, which represent the actual layout of cooling towers in power plants, has received considerably less attention. Moreover, the influence of radiator geometric arrangement on thermal performance enhancement has mainly been investigated for isolated towers. In the present study, the thermal performance of natural draft dry cooling towers equipped with circular and elliptical radiator arrangements was investigated under crosswind conditions for various twin-tower and triple-tower layouts. Three-dimensional numerical simulations were performed using ANSYS Fluent by solving the governing equations of mass, momentum, and energy conservation together with the standard k-ε turbulence model. The baseline cooling tower model was developed based on the specifications of the Shahid Montazeri Power Plant cooling tower in Isfahan, Iran. The performance of different tower arrangements was evaluated at crosswind velocities of 3, 5, 7, and 10 m/s. To validate the numerical model, the simulation results were compared with available data from previous studies. The validation results demonstrated good agreement with the reference data, with an average relative error of less than 7.2%. Several performance indicators, including overall thermal efficiency, dimensionless air mass flow rate through the radiators, dimensionless outlet water temperature, and temperature and velocity distributions, were analyzed. Under no-wind conditions, the results showed that replacing the conventional circular tower geometry with an elliptical one reduced the airflow passage area, leading to a 5.1% decrease in air mass flow rate and, consequently, a 3.8% reduction in radiator heat transfer capacity. Under crosswind conditions, however, the thermal performance exhibited a strong dependence on wind speed and direction. At high wind velocities (7 and 10 m/s), the elliptical radiator arrangement significantly improved tower performance. For side-by-side twin-tower layouts, the overall thermal efficiency increased by 17% to 29.5%, whereas improvements ranging from 9.8% to 19.8% were achieved for tandem layouts. In triple-tower arrangements, thermal efficiency increased by 14.6% to 28.1% for the east-to-west wind direction and by 24.45% to 28.85% for the west-to-east wind direction. Flow field analysis revealed that the primary mechanism responsible for the enhanced thermal performance of elliptical towers is the altered discharge pattern of the heated airflow and its interaction with downstream radiators. This phenomenon increases the average temperature gradient across the radiators and consequently enhances the heat transfer rate compared with conventional circular towers. Furthermore, the results indicated that the airflow structure becomes highly complex at high wind speeds, making reliable prediction of tower thermal behavior impractical without numerical simulation. Overall, the findings demonstrate that optimizing radiator arrangement and employing an elliptical tower geometry constitute an effective, low-cost, and passive design strategy for mitigating the adverse effects of crosswinds and substantially improving the thermal performance of natural draft dry cooling towers in multi-tower layouts.