Circular Counterflow Cooling Tower

Crew Introduction

The circular cooling tower employs counterflow air–water heat exchange technology. Its main structure is entirely steel, with a fiberglass‑reinforced plastic enclosure, and it is equipped with maintenance ladders to facilitate routine inspection and upkeep of the equipment at the top. The packing consists of high‑quality modified PVC inclined‑wave sheets, maximizing the spray‑water contact area. Water distribution—either through rotary nozzles or pipe‑type distributors—ensures uniform coverage, thereby enhancing cooling efficiency. Due to its circular shape, it is referred to as a “circular cooling tower.”

(1) Operating Principle of the Unit

Take the operating process of a circular counterflow cooling tower as an example: Hot water is pumped from the chiller room through pipelines, a horizontal throat, a curved throat, and a central throat at a specified pressure, delivering the circulating water to the tower’s water-distribution system. The water is then evenly sprayed onto the packing material via small nozzles on the distribution pipes. Meanwhile, dry, low‑humidity air enters the tower from the bottom air inlet under the action of the fan. As the hot water flows over the surface of the packing, it forms a thin water film that exchanges heat with the air. The resulting high‑humidity, high‑enthalpy exhaust air is drawn out from the top, while the cooled water drips into the collection basin and is discharged through the outlet pipe back to the chiller.

Under normal conditions, the air entering the tower is dry and has a low wet-bulb temperature. A clear concentration gradient of water molecules and a kinetic‑energy pressure difference exist between the water and the air. When the fan is operating, under the influence of the tower’s static pressure, water molecules continuously evaporate into the air, turning into water vapor. As a result, the average kinetic energy of the remaining water molecules decreases, leading to a drop in the circulating water temperature. From this analysis, it is evident that evaporative cooling is independent of whether the air temperature (commonly referred to as the dry‑bulb temperature) is lower or higher than the water temperature; as long as water molecules can keep evaporating into the air, the water temperature will continue to fall. However, evaporation does not proceed indefinitely. When the air in contact with the water is unsaturated, water molecules continue to evaporate; but once the air at the water–air interface reaches saturation, no further evaporation occurs, and a dynamic equilibrium is established. At this point, the rate of water molecules escaping into the air equals the rate of those returning from the air to the water, and the water temperature remains constant. Thus, the drier the air in contact with the water, the more readily evaporation takes place, and the easier it is for the water temperature to decrease.

(II) Unit Structure

The circular counterflow cooling tower comprises a fiberglass-reinforced plastic shell, a fan, an electric motor, a water distribution system, and inclined‑wave packing.

Technical Parameters of Circular Counterflow Cooling Towers

1. The noise level is a standard measured value, taken at a distance from the tower wall and at a height of 1.5 meters above the foundation.

2. The standard design conditions are a wet-bulb temperature of 28°C, an inlet water temperature of 37°C, and an outlet water temperature of 32°C, resulting in a water temperature drop of 5°C and an approach temperature of 4°C.

3. Inlet water pressure refers to the water pressure at the connection point; 1 kgf/cm² = 9.8 × 10⁴ Pa. Accordingly, the water pressure for this series of towers ranges from 0.2 to 0.49 kgf/cm².