Speaker
Description
Small nuclear power plants (SNPP) are currently actively being developed. When designing such stations, a lot of attention is devoted to enhancing safety and equipment reliability. It can be implemented by using passive principles, such as self-adjusting cores and refuse force coolant circulation in favour of natural coolant circulation.
In this presentation, the simulation of a dry cooling tower with natural air draft for SNPP will be considered. The use of a dry cooling tower does not require a constant supply of cooling water to irrigate the surface of cooling tower’s heat exchanger, and it allows you to heat to be withdrawn at negative ambient temperatures. Refusing fans in favor of natural air flow reduces electricity consumption for the station's own needs and minimizes the necessary maintenance of the cooling tower.
A series of CFD calculations have been carried out on a dry cooling tower to define the air flow through it and the output power in zero wind conditions, as well as to estimate the influence of external factors such as wind speed and direction and air temperature in its operation.
Heat is transferred to a dry cooling tower through heat exchangers, which are arranged as vertical pipes with developed transverse fins located in a chessboard pattern. In order to reduce the required computing and temporary costs, the heat exchanger area was modeled using layers of porous materials strung on supporting tubes.
During the scaffolding phase, small-scale numerical simulations and experimental testing of heat exchanger blowdowns were conducted. Based on the findings from this research, parameters for the porous materials were selected.
The next step in designing a dry cooling tower was to simulate the sector of the tower with the volume of air surrounding it. During the simulation, flow rates were obtained for natural circulation through the dry cooling tower. Changes to the design were proposed to increase natural air circulation, and heat output increased by 1.54 times.
Finally, the influence of external atmospheric factors was estimated by simulating half of the cooling tower surrounded by air. When analyzing the results, a significant distortion of heat transfer along the cooling tower section was noted in the presence of wind, and this distortion increased with an increase in wind speed. At high wind speeds, a through-flow around the tower was observed.
To reduce these effects, the installation of a cruciform partition in the center of the cooling tower and/or the use of external swirlers and air intake devices were simulated. The best solution for reducing the influence of wind was to install a solid wall at the entrance to the cooling tower with air intake devices positioned at a certain height to prevent them from being snowed in during winter.
In a nutshell, a design for a dry cooling tower with natural draft, with a power 1.2 MW, was obtained. The design allows the SNPP to operate entirely in passive mode, both at energy level and at afterheat.
