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An evaporative air cooler, also known as a closed-circuit cooling tower, is a highly efficient and energy-saving cooling device that integrates water cooling and air cooling technologies.
It achieves heat exchange through cross-flow of air, spray water, and circulating water. Employing a tubular heat exchanger structure, it features high heat transfer efficiency, compact structure, and water and energy savings.
Evaporative air coolers integrate a condenser, cooling tower, and circulating water pump, saving 30%-50% of floor space. They are suitable for industries such as oil refining, metallurgy, power generation, and cold chain logistics.
Evaporative air coolers utilize the combined heat dissipation of the latent heat of vaporization of water and the sensible heat of air. The cooling temperature depends on the wet-bulb temperature. Recycling the spray water reduces cooling water consumption by up to 4/5. Its application is driven by the “dual-carbon” policy and energy efficiency upgrades. Technological advancements include fluid-induced vibration to enhance heat transfer and spray humidification in wet air coolers. The heat transfer coefficient of spray-type coolers is 2-4 times higher than that of dry-type coolers.
Evaporative air coolers offer advantages such as compact structure, high heat transfer efficiency, low investment, low operating costs, and convenient installation and maintenance. They have broad application prospects in industries such as oil refining, metallurgy, power generation, refrigeration, and light industry, representing a new direction in air cooling technology development.
Research on evaporative air cooling began in the 1960s, primarily for applications such as engine jacket water cooling, compressor interstage cooling, and lubricating oil cooling.
An evaporative air cooler places a tubular heat exchanger inside a tower, ensuring cooling through heat exchange between circulating air, spray water, and circulating water. Because it’s a closed-loop system, it ensures water quality remains uncontaminated, effectively protecting the efficient operation of the main equipment and extending its service life. When the outside temperature is low, the spray water system can be shut down, achieving water conservation.
With the implementation of national energy conservation and emission reduction policies and the increasing scarcity of water resources, closed-loop cooling towers have been widely used in industries such as steel metallurgy, power electronics, machining, and air conditioning systems in recent years.
Evaporative air coolers, also known as closed-loop cooling towers, are widely used in industries such as metallurgy, petrochemicals, power generation, chemicals, and building materials.
Closed-loop air-cooled circulating water systems are increasingly being used in blast furnaces for ironmaking, demonstrating significant effects in corrosion prevention, scale reduction, and thus improving the operating efficiency and lifespan of heat exchange devices and equipment. This system utilizes plate heat exchangers.
Hot soft water (55℃) returning from the blast furnace is cooled by the plate heat exchanger, then pressurized before being sent back to the blast furnace. Meanwhile, cooling water, after passing through the plate heat exchanger and increasing in temperature, is sent to the cooling tower for cooling, and then pressurized before being sent back to the plate heat exchanger as a cooling medium. The ratio of soft water circulation volume to cooling water circulation volume is typically 1:1.
Energy-Saving Water Film Evaporative Air Cooler
To further improve the operating efficiency and lifespan of heat exchange devices and equipment, and to further save energy and water, our company has meticulously designed a “High-Efficiency Closed-Loop Air-Cooled Circulating Water System.”
This system replaces the original plate heat exchanger and cooling tower with an energy-saving water film air cooler, resulting in high operating efficiency. The cooling water circulation volume is reduced by 4/5, and the power consumption is also reduced by 4/5. Simultaneously, the system employs ambient temperature deoxygenation equipment and a degassing device, further reducing corrosion and ensuring stable and safe system operation.
The structure and flow diagram of the energy-saving water film air cooler are shown below
The main feature of the energy-saving water film air cooler is enhanced heat transfer through the evaporation of a water film on the outside of the tubes. Its operation involves a circulating water pump delivering circulating cooling water from the circulating water tank to a spray system located above the tube bundle. The spray system sprays the cooling water downwards onto the surface of the tube bundle, forming a thin water film on its outer surface. Simultaneously, an axial flow fan draws air in through louvers, causing the air to flow upwards across the tilted tube bundle from below.
The energy-saving water film air cooler primarily relies on the rapid evaporation of the water film on the outer surface of the tubes to enhance heat transfer outside the tubes, thereby achieving the purpose of cooling the soft water inside the tubes. This is primarily because water has a relatively high latent heat of vaporization (570 kcal/kg at one atmosphere), significantly improving overall heat transfer efficiency.
During operation, the evaporation of the water film on the outer surface of the pipes causes the air passing through the tube bundle to become nearly saturated with humidity. The axial flow fan draws in this humid air and forces it through a mist eliminator located above the spray system, removing water droplets before discharging it into the atmosphere through the air outlet.
Because the axial flow fan is located at the top of the equipment, a negative pressure zone is created below it as air is drawn upwards, accelerating the evaporation of the water film on the outer surface of the pipes and thus enhancing heat transfer outside the pipes.
During operation, soft water flows inside the pipes, while air and cooling water flow outside. Air flows from bottom to top, while the spray water flows from top to bottom. The cooling water, air, and soft water flow in a cross-flow pattern, while the cooling water and air flow counter-currently. This overall process arrangement also enhances heat and mass transfer.
