Cooling tower and evaporative cooling principles, differences and application scenarios

Central air conditioning cooling tower and evaporative cooling are two different cooling devices, which play an important role in air conditioning systems. In order to better understand the concepts and functions of the two, we can discuss them from the aspects of their working principles, structural characteristics and application scenarios.

1. Cooling tower
Central air conditioning cooling tower is a cooling device used in water-cooled central air conditioning systems. It achieves cooling effect by spraying hot water on heat dissipation materials and contacting with the passing air. The cooling process mainly depends on two aspects: sensible heat transfer and latent heat transfer: sensible heat transfer refers to the direct heat exchange between hot water and cold air; while latent heat transfer refers to the process of taking away heat when part of the hot water evaporates into steam. This cooling method allows cooling water to be recycled, thereby saving water resources and reducing operating costs.
Cooling towers include two types: cross-flow and counter-flow. The cross-flow cooling tower is characterized by air entering from the side and intersecting with the water film flowing from top to bottom at a 90-degree angle, which is suitable for places with limited space; counter-flow cooling towers require air to flow upward from the bottom to form a counter-flow with the descending hot water to enhance heat transfer efficiency. Regardless of the form, cooling towers use the basic physical phenomenon of water evaporation absorbing heat to reduce the temperature of cooling water.

Advantages of cooling towers:

Cost-effectiveness: For large-scale cooling needs, cooling towers are usually a more economical choice, especially in situations where a large amount of cooling water circulation is required.

Easy maintenance: The design of cooling towers is relatively simple, daily maintenance is relatively easy, and the required professional skills are relatively low.

Wide applicability: Cooling towers can be used with a variety of types of chillers, including screw machines, centrifugal machines, etc., and have strong adaptability.

Disadvantages of cooling towers:

High water consumption: Traditional cooling towers rely on the evaporation of water to achieve cooling effects, which leads to high water consumption, especially in hot and dry climates.

Space occupation: Cooling towers often require a large installation space, especially for large buildings, and may require a dedicated roof or ground location to place the equipment.

Noise problem: Due to the action of fans and water flow, cooling towers may generate certain noise pollution during operation, affecting the surrounding environment.

2. Evaporative cooling
Evaporative cooling is also a device that uses the heat absorption effect of water evaporation to achieve cooling purposes, but its design focuses more on the condensation process of the refrigerant. Evaporative condensers are mainly used in cold storage construction, central air conditioning and other refrigeration facilities as a core component of the refrigeration system. It allows high-temperature and high-pressure gaseous refrigerant to pass through the heat exchange tube group, and the phase change becomes liquid refrigerant under the action of spraying water outside the tube.
The main difference between an evaporative condenser and a traditional cooling tower is that the cooled medium undergoes a phase change, that is, from gas to liquid. In addition, an evaporative condenser usually adopts a closed circulation system, which means that it can work under higher pressure conditions. Since the evaporative condenser can directly handle the refrigerant, it can replace the traditional shell and tube condenser plus cooling tower combination, simplifying the system structure and improving energy efficiency.
Advantages of evaporative cooling:
High efficiency and energy saving: The evaporative condenser can perform condensation operations at a lower temperature by utilizing the principle of heat absorption by water evaporation, thereby improving the energy efficiency ratio of the entire system.
Significant water saving: Compared with traditional cooling towers, the amount of make-up water required for evaporative condensers is greatly reduced because its design tends to maximize the cooling potential of each liter of water.
Compact design: Due to the reduced need for cooling towers, evaporative condensers can provide a more compact solution, saving valuable installation space.

Disadvantages of evaporative cooling:
High initial investment: Although the long-term operating costs are lower, the initial purchase cost of evaporative condensers is usually higher than that of traditional cooling tower systems.
Risk of corrosion: Due to the contact between water and air, corrosion may occur inside the evaporative condenser, especially the serpentine coil part, which increases the difficulty of maintenance.
Strict water quality requirements: In order to ensure the normal operation of the equipment and avoid scaling problems, evaporative condensers have high requirements for water source quality, and water quality needs to be monitored regularly and corresponding treatment measures should be taken.

In actual applications, cooling towers are more often used in occasions where a large amount of cooling water circulation is required, such as central air-conditioning systems in large shopping malls, office buildings and other places. Evaporative condensers are more suitable for applications with higher energy efficiency requirements, such as large and medium-sized refrigeration units, due to their high efficiency and energy-saving characteristics. However, it should be noted that although evaporative cooling has significant energy-saving advantages, in some cases, such as areas with poor water quality or high ambient humidity, evaporative cooling technology may not be suitable.