Water-cooled Air Conditioner: How Does It Work?


Water-cooled air conditioners are mostly used in large commercial buildings such as hotels, shopping malls and office towers. Water-cooled air conditioners are known for its high efficiency.

How Do the Water-Cooled Air Conditioners Work?

Water-cooled air conditioners are also known as the chilled water system or chiller system.The chilled water system mainly consist of the following equipment:

  • Water-Cooled Chiller
  • Chilled Water Pump
  • Evaporators (Ceiling Ducted, Ceiling Cassette, Wall Mounted, etc.)
  • Condenser Water Pump
  • Cooling Tower
  • Make-Up Water Tank
A typical water-cooled chiller system.

In a chilled water system, there are the chilled water loop and the condenser water loop. The chilled water loop is responsible for the cooling while the condenser water loop is responsible for the heat rejection.

The cooling: chilled water loop basic operation.
The heat rejection: condenser water loop basic operation.

The chiller itself consists of two parts: the evaporator and the condenser. Chilled water flows through the evaporator and condenser water flows through the condenser. You can easily identify the evaporator because it is often insulated to prevent condensation. As shown in the below photo, the evaporator of the chiller is insulated with black color closed-cell insulation.

A R1233zd Inverter Centrifugal Water-cooled Chiller.

You can think of a chiller as a giant compressor. Similar to a home air conditioner, it operates with the principle of the refrigeration process. Instead of removing heat with air like the home air conditioner’s outdoor unit, a chiller does that with water. Hence, the name water-cooled chiller.

Chillers and pumps are often located in a chiller plant room. Because chillers produce loud noises, the chiller plant room is often designed to be at the basement level. On the other hand, cooling towers usually located at the roof because it needs outside air to remove the heat.

With a chilled water system, the entire building is full of pipes to transfer the chilled water around to each evaporator (fan coil units, ceiling cassettes, etc.) and the condenser water all the way from the basement to roof.

Do Water-Cooled Air Conditioners Consume Water?

In short, water-cooled air conditioners do consume water due to the natural evaporation of water at the cooling tower.

The chilled water is a closed-loop system. Hence, water will not disappear if there is no leakage. However, the condenser water is an open-loop system. When water is splashed across the fin of a cooling tower, it evaporates easily. Over time, the water level drops significantly.

Therefore, there is always make-up water for the cooling tower. Usually controlled by a float valve. Whenever the water level drops below a certain level in the cooling tower, new freshwater will be added to maintain the water level.

Other Types of Air Conditioners that Use Water

Water-cooled package air conditioners use water for the evaporator and the air for the condenser. Similar to the chiller, it sends chilled water to the evaporators such as fan coil units and ceiling cassette units. Different is at the condenser side, instead of using water, it uses outside air to remove the heat.

Another type of water-cooled package air conditioners not just produce chilled water but also use water to remove the heat from its condenser. Some of the water-cooled package air conditioners utilize seawater to remove heat from the condenser. Even more, some of the water-cooled package air conditioners circulate condenser water into the deep ground and transfer the heat from the condenser to the cold ground. These types of systems are costly and complicated. But, they often considered green products because they use renewable energy.

Air Coolers

Air coolers use water as their source of cooling. Users need to constantly add water to an air cooler as the water constantly evaporates, bringing the heat along with it. Thus, air coolers are not air conditioners.

Air coolers are only capable of blowing air for as cold as the water temperature. Typically around 27-28°C unless you are filling the air cooler with freezing water.

Related Questions

Is all centralized air conditioning systems are water-cooled? Not all centralized air conditioning systems are water-cooled. The air-cooled system also can be a centralized air conditioning system. The air-cooled system uses refrigerant for the cooling and outside air for heat rejection.

Why most commercial buildings use a water-cooled system? The water-cooled system offers better efficiency compared to the air-cooled system. A water-cooled system usually about 30-40% more efficient than an air-cooled system.

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