The application of cooling towers in data centers

Over the years, due to increasing server density and reducing its size, server density has become increasingly high, and data centers are increasingly generating more heat. Therefore, the wattage of heat generated per square foot is constantly increasing, and this increase in power density seriously restricts traditional cooling methods and technologies. At the same time, a large amount of energy is converted into a large amount of heat after being applied to data centers, which is a cyclical process. Given this energy consumption and cost, experts have been searching for ways to reduce energy costs while also being environmentally friendly. One method is to use a cooling tower. This article provides a brief introduction to the working principle and application characteristics of cooling towers.

As its name suggests, a cooling tower is a tower like device responsible for cooling a data center and releasing waste heat into the atmosphere. The cooling tower uses cooling water or only uses air to consume the heat discarded by the data center. Cooling towers come in various sizes, with simple towers reaching rooftop height and huge towers occupying an area with a diameter of up to 100 meters. The size of the cooling tower installed in a data center mainly depends on the total amount of heat that needs to be removed and other related factors.

The working principle of a cooling tower: A cooling tower is a device that uses the contact between water and air to dissipate waste heat generated in equipment or refrigeration air conditioning through evaporation. The basic principle is that dry (low enthalpy) air enters the cooling tower from the inlet air network after being pumped by the fan; High temperature water molecules with high saturated vapor partial pressure flow towards air with low pressure, while moist and hot (high enthalpy) water is sprinkled into the tower by the self seeding water system. When water droplets come into contact with air, on the one hand, due to the direct heat transfer between the air and the air, and on the other hand, due to the pressure difference between the surface of the water vapor and the air, evaporation occurs under the action of pressure. Currently, it carries away the latent heat of evaporation and carries away the heat in the water, thus achieving the purpose of cooling.

The working process of the cooling tower: Taking the working process of a circular counter flow cooling tower as an example, the hot water in the main machine room is circulated through pipes, horizontal throats, curved throats, and central throats through a water pump at a certain pressure to the water sowing system of the cooling tower. The water is evenly sprinkled on the packing through small holes on the water sowing pipe; Dry, low humidity air enters the tower from the bottom through the air grid under the action of the fan. When hot water flows through the surface of the packing, it forms a water film and exchanges heat with the air. High humidity and high humidity hot air is extracted from the top, and the air entering the tower is dry, low humidity and bulb temperature air. There is a clear difference in water molecule concentration and kinetic energy pressure between water and air. When the fan is running, under the static pressure inside the tower, Water molecules continuously evaporate into the air, becoming water vapor molecules. The average kinetic energy of the remaining water molecules will decrease, resulting in a decrease in the temperature of the circulating water. From the above analysis, it can be seen that evaporative cooling is not related to the temperature of the air (commonly known as dry bulb temperature) being lower or higher than the water temperature. As long as water molecules can continuously evaporate into the air, the water temperature will decrease. However, the evaporation of water into the air will not continue indefinitely. When the air in contact with water is unsaturated, water molecules continuously evaporate into the air. However, when the air on the water air contact surface reaches saturation, the water molecules do not evaporate and are in a dynamic equilibrium state. The number of water molecules evaporated is equal to the number of water molecules returned from the air to the water, while the water temperature remains constant. From this, it can be seen that the drier the air in contact with water, the easier it is for evaporation to occur and the water temperature to decrease.

It can be seen that the working principle of the cooling tower is easy to understand. Simply put, ventilated air blows towards the dripping water from the correct angle. When the air passes through these water droplets, a portion of the water evaporates. Due to the heat used to evaporate the water droplets, the temperature of the water is lowered, and the remaining water is cooled. The cooling effect of this method depends on the relative humidity and pressure of the air.

The total amount of evaporated water increases with a decrease in humidity, and the temperature of the remaining water also decreases. In other words, the lower the humidity, the better the cooling effect of the cooling tower. Ordinary cooling towers come in various shapes and sizes. According to the workload requirements and installation location, some cooling towers are shaped like an inverted funnel, while others are like a small box.

It must be remembered that the initial cost of installing a cooling tower is definitely much higher than installing traditional cooling systems without cooling towers. However, this is definitely a one-time cost, but the cost savings each year will continue to increase. Therefore, for a period of time, cooling towers can definitely save a lot of money and precious energy. Considering the global energy situation, energy conservation is even more important.

The application of cooling towers in data centers has received attention, and Intel recently introduced its successful use of cooling towers in two high-density data centers, reducing power consumption of cooling equipment by using moisture energy-saving equipment. Using this method can save $144000 in electricity bills annually. By any standard, this is a significant savings.

However, in Intel's cooling tower experiment, it was also found that this energy-saving device may not be as cost-effective as it initially appeared. The reason for this contradiction is that the cooling tower requires a large humidification system and preheating. This will increase the cost and complexity of the entire system.

There is also a debate that the use of cooling towers as energy-saving equipment requires more water at lower temperatures in terms of humidity, so the fan section of the cooling tower will consume more energy, so it is not cheap. However, the experimental results indicate that this has no negative impact, and the cooling tower remains energy-saving in the long run.

Therefore, we see that cooling towers are an excellent way to provide cooling in industrial institutions and data centers using natural free air. In the long run, this method is actually energy-saving. We look forward to increasing the application of cooling towers in the future, so as to bring benefits to enterprises while saving more valuable energy. However, any individual strategy will have its own limitations, so in order for data centers to achieve maximum energy efficiency, they need to adopt a comprehensive approach. CIOs need to intelligently combine all current energy reduction methods in the industry and find new ways to reduce energy consumption.