Hybrid Wet-Dry Closed-Circuit Cooling Tower

A dry–wet combined cooling tower is a highly efficient, water-saving heat-exchange equipment system.

I. Advantages

It combines the zero water‑consumption advantage of dry air coolers with the high efficiency of wet cooling towers, effectively forging a powerful synergy. The upper section houses a finned air cooler, while the interior contains a high‑temperature circulating medium that first enters the dry‑type system for preliminary cooling, resulting in a partial temperature reduction of the circulating water. If this initial cooling fails to meet process requirements, the flow proceeds to the second stage—the wet‑type system—where heat exchange is facilitated by smooth‑walled tubes. Spray water is atomized from the top and falls downward; as it evaporates, it absorbs latent heat of vaporization, consuming the spray water and further lowering the temperature of the circulating medium within the tubes. This constitutes a wet cooling system.

II. Structural Overview

Its structure primarily comprises several components, including the housing, frame, finned air cooler, bare-tube heat exchange coil, cooling packing, fan, water pump, and control system. The housing is fabricated from metal, offering corrosion resistance and long-lasting durability; the cooling packing enhances heat and mass transfer by increasing the contact area between water and air; the fan draws in ambient air and passes it through the cooling packing for cooling; the water pump circulates cooling water back to the cooling tower for recirculation; and the control system enables automated monitoring and regulation of the entire system. By selecting and maintaining equipment appropriately and applying control technologies in a scientifically sound manner, energy savings and reduced consumption can be further achieved.

III. Finned Heat Exchangers

To enhance heat transfer efficiency and increase the heat-transfer surface area, finned heat-exchanger tubes are employed. Fins are helically wound around steel or stainless-steel tube casings, significantly expanding the heat-exchange area and improving thermal performance. Cooling air flows at high velocity between the fins, facilitating convective heat transfer to both the base tube and the fins. This configuration is referred to as dry-type heat exchange.

IV. Light-tube Heat Exchanger

Wet cooling towers typically employ bare-tube designs for ease of maintenance. Their primary advantages include reducing the likelihood of scaling as spray water flows through, accelerating the renewal of the water film, and facilitating easy cleaning and descaling when scaling does occur. Moreover, replacing heat exchange tubes is simplified, with improved interchangeability.

V. Framework

The frame serves as the structural backbone of a closed‑circuit cooling tower, providing the supporting framework that ensures the equipment’s stability and optimal performance. Oasis Bingfeng closed‑circuit cooling towers are typically fabricated from galvanized steel or 304 stainless steel, offering high strength, excellent corrosion resistance, and an extended service life, making them well suited for operation in hot, humid conditions with frequently changing wind directions.

VI. Housing

The shell of a wet–dry combined cooling tower is typically fabricated from high‑strength metal, offering excellent corrosion resistance and durability. The shell design meets requirements for water tightness, dust protection, and corrosion resistance, while also facilitating maintenance and cleaning.

VII. Cooling Packing

Cooling packing is one of the core components of a dry–wet combined cooling tower, primarily serving to increase the contact area between water and air, thereby facilitating efficient heat and mass transfer. Spray-type packing atomizes water into a fine mist, further enhancing the contact surface between water and air while reducing clogging and simplifying cleaning.

VIII. Fan

The fan is another critical component of a wet–dry combined cooling tower, primarily responsible for drawing in low‑temperature, dry ambient air, passing it through the heat‑exchange coils, finned air coolers, and cooling packing to achieve cooling, and then exhausting it. Fan selection should be based on a comprehensive assessment of factors such as airflow rate, static pressure, and noise levels. Centrifugal fans or axial fans are typically employed; centrifugal fans are suited to applications with high resistance and high airflow, while axial fans are preferred for low‑resistance, high‑airflow conditions.

9. Water Pump

The water pump is an auxiliary device in wet–dry combined cooling towers, primarily used to circulate cooling water back to the tower for recirculation. With a wide variety of pump types available, it is essential to select the appropriate model and specifications based on operating conditions. Centrifugal pumps or self-priming pumps are commonly employed; among these, centrifugal pumps offer high flow rates and stable pressure, making them well suited for large-scale cooling systems.

X. Control System

The control system of a combined dry–wet cooling tower primarily consists of sensors, a controller, and actuators, enabling automated control and regulation of equipment such as fans and pumps to ensure the system’s stable operation and energy efficiency. Sensors are used to detect environmental parameters like temperature, humidity, and water level, converting these measurements into electrical signals that are transmitted to the controller. The controller processes and analyzes these sensor inputs to manage the start‑stop operations and operating states of fans, pumps, and other devices. Actuators—typically motors or pneumatic devices that drive dampers, valves, and similar components—facilitate precise adjustment and control of the system.

In summary, the dry–wet combined cooling tower is a compact, fully functional, and high‑performance energy‑saving device with broad application prospects in modern industrial and building sectors.