Why are the cooling towers of power plants designed to be curved?

Hyperbolic cooling tower: A type of cooling tower used for the natural ventilation cooling of circulating water in thermal power plants and nuclear power plants; it is a large-scale thin-shell structure. Power plants built in areas with limited water supplies need to install a circulating cooling water system in order to save water, allowing the hot water discharged from the coolers to be cooled and reused. Cooling structures used in large power plants are mostly hyperbolic cooling towers. Such cooling towers are commonly used in power stations located in inland areas with water shortages. However, recently seawater cooling towers have been installed at the Guohua Power Plant in Ninghai, Zhejiang Province, China, to cool seawater, thereby preventing the plant’s waste heat from being discharged into the sea and affecting marine ecosystems. Some power plants that use air-cooled condensers with forced ventilation no longer require such a building. 　　Britain was the first to use this type of cooling tower. It has been widely used in various countries since the 1930s, and in the 1940s, hyperbolic cooling tower clusters were successively built at the Fushun Power Plant and Fuxin Power Plant in Northeast China. A cooling tower consists of a water collection tank, pillars, a tower body, and a water spraying device. Collecting tanks are usually circular pools located about 2 meters underground. The tower shaft is a thin-walled spatial structure in a hyperbolic shape, without ribs or beams, designed to facilitate natural ventilation; it is usually constructed from reinforced concrete. The cooling tower ventilation shaft consists of three parts: the lower ring beam, the shaft wall, and the rigid top ring. The lower ring beam is located at the lower end of the ventilator casing; the self-weight of the ventilator and other loads it bears are transmitted through the lower ring beam to the inclined struts, and from there to the foundation. The tower wall is the main component of the cooling tower’s ventilation tower; it is a tall thin-shell structure subjected primarily to wind loads, and it is highly sensitive to wind. The shape and wall thickness of its shell must be verified through shell optimization calculations and buckling stability analysis, which are important aspects of such optimization calculations. The rigid ring at the top of the tower is located at the upper end of the shell; it serves as a reinforcing ring at the top of the cylindrical shell, enhancing the stiffness and stability of that area. 　　The diagonal strut is the supporting structure of the ventilation duct, primarily bearing its own weight, wind loads, and thermal stresses. The diagonal struts are inclined in two directions in space; based on their geometric shape, they can be of the \"H\"-shape, \"V\"-shape, or \"X\"-shape, and their cross-sections are usually circular, rectangular, octagonal, etc. It is generally designed as a double-parabola shape, with the foundation bearing all the loads transmitted from the inclined struts. Based on their structural form, there are ring foundations (including inverted \"T\"-shaped foundations) and individual foundations. The settlement of the foundation has a significant impact on the stress distribution in the shell, and is highly sensitive to it. Therefore, the inclined struts and foundation are also very important in the optimized calculation and design of cooling towers. 　　The height of a cooling tower is generally 75 to 150 meters, with a base diameter of 65 to 120 meters. The upper part of the tower is a wind duct; below the first section of the duct wall (the lower ring beam) lie the water distribution troughs and sprinkling devices, which are collectively referred to as the sprinkling framework and are typically made from PE or PVC materials. There is a water storage tank at the bottom of the tower, but it needs to be refilled continuously based on the rate of evaporation. The water spraying device is the main equipment for evaporating water to dissipate heat. During operation, water flows downward from the water distribution tray, dripping and splashing; air enters from the side at the bottom of the tower, comes into full contact with the water, and then exits upward carrying heat with it. The cooling process is primarily based on evaporative heat dissipation, with a small portion coming from convective heat dissipation. Hyperbolic cooling towers occupy less space than pond-type cooling structures, are compact in design, experience less water loss, and their cooling efficiency is not affected by wind conditions ； It is also easier to maintain than mechanical ventilation cooling towers, and it saves electricity ； However, due to their large size, complex construction requirements, and high costs, electric slip form methods are often used.

Firstly, it is necessary to meet the technical requirements of the equipment itself. The purpose of a cooling tower is to improve the efficiency of heat exchange between water and air; water flows down along the walls of the tower, while air moves upward from the bottom of the tower. In this way, the water remains just above the path of the air currents, resulting in the best possible heat exchange effects. Secondly, it is important to meet the process requirements. While striving to fulfill the technical requirements of the equipment, it is also essential to minimize investment costs and construction difficulties, which is why hyperbolic shapes become the ideal choice.

Hot air rises; once it reaches a certain height, negative pressure is generated on the outside of the middle part of the hot air column. As a result, the hot air column shrinks and takes on a hyperbolic shape. People take advantage of this principle by designing cooling towers in this format – it matches the shape of the air rise pattern, makes full use of available space, and also allows the cooling water to come into full contact with the hot air, resulting in an effective cooling effect.

There are also certain considerations regarding reducing investment and lowering the difficulty of construction.

This should be related to the flow pattern of the fluid.

:Lol, it should be possible to clearly see through flow field simulation which design is the most reasonable! ! The original poster can look for such literature; there must be some! !