Air-cooled, Water-cooled, Chilled Water, Dual Cooling Source and Free Cooling Precision Air Conditioners

2025-03-05

The types of precision air conditioners in data center computer rooms mainly include air-cooled type, water-cooled type, chilled water type, dual cooling source type, and free cooling type, etc.

Air-cooled, Water-cooled, Chilled Water, Dual Cooling Source and Free Cooling Precision Air Conditioners1741179258215

Today, we will mainly make a simple collation of them starting from their principles, structural compositions, and advantages and disadvantages, so that users interested in this content can quickly understand the similarities and differences among them, lay a foundation, and then conduct a deeper understanding.

Air-cooled Precision Air Conditioner
The heat absorbed by the air-cooled unit from the computer room is transferred to the outdoor air through the condenser (outdoor unit of the precision air conditioner) installed outdoors or on the roof.
It has a simple composition, consisting of an indoor unit and an outdoor unit. The indoor unit includes a compressor, an evaporator, and an expansion valve, and the outdoor unit is a condenser. The indoor unit and the outdoor unit form a closed loop.
Principle, Advantages and Disadvantages of the Air-cooled Precision Air Conditioner
Advantages: The system is simple and reliable, easy to maintain, highly reliable, and the overall investment cost is low.
Disadvantages: The outdoor unit makes a lot of noise, there are restrictions on the installation distance, and the refrigeration efficiency is relatively low.
The air-cooled precision air conditioner is a widely used type in data centers at present, and it is suitable for areas with a lack of water resources and places without a cooling water system.
Water-cooled Precision Air Conditioner
The heat absorbed by the water-cooled unit from the computer room is transmitted to the refrigerant through the built-in water-cooled condenser.
The main difference from the air-cooled unit is that the water-cooled unit is equipped with a plate-type condenser in the indoor unit, and the internal circulation of the refrigerant is only in the indoor unit, and an external cooling tower is required.
The cooling water usually uses a mixture of antifreeze water and ethylene glycol to replace the commonly used refrigerant.
Principle, Advantages and Disadvantages of the Water-cooled Precision Air Conditioner
Advantages: The energy efficiency ratio is higher than that of the air-cooled unit, and it is more energy-saving.
Disadvantages: The initial investment and maintenance costs are relatively high.
The water-cooled precision air conditioner is suitable for places with a centralized cooling water system.
Chilled Water Type Precision Air Conditioner
The chilled water type precision air conditioner controls the environmental temperature in the computer room through chilled water. The prerequisite is to have chilled water, which can use the chilled water of the central air conditioner or build a new chilled water system.
It is composed of a chiller unit (air-cooled chilled water unit, water-cooled chilled water unit), an air-cooled condenser, and a cooling tower.
The chiller unit is equivalent to the outdoor unit and includes four main components: a compressor, an evaporator, a condenser, and an expansion valve, thus achieving the refrigeration and heating effects of the unit.
The chilled water type precision air conditioner in the indoor unit is mainly composed of a chilled water coil, a fan, an electric heater, a humidifier, and a water valve, and generally does not have a compression refrigeration system.
Principle, Advantages and Disadvantages of the Chilled Water Type Precision Air Conditioner
Advantages: The initial investment is small.
Disadvantages: Excessive dependence on chilled water.
The chilled water type precision air conditioner is suitable for areas with abundant water resources or places with a rich chilled water system.
Dual Cooling Source Type Precision Air Conditioner
The dual cooling source type precision air conditioner has a dual system with an independent chilled water unit and a direct expansion refrigeration system, and there are the following two combinations:
① Air-cooled condensation + chilled water, with the chilled water system as the main use and the air-cooled system as the backup.
② Water-cooled condensation + chilled water, with the chilled water system as the main use and the water-cooled system as the backup.
In places where chilled water resources can be provided but continuous supply throughout the year cannot be guaranteed, the unit will preferentially use the chilled water system for refrigeration; when the chilled water supply is interrupted or the temperature of the chilled water is not low enough to meet all the load requirements, the direct expansion refrigeration system will be automatically started.

Principle, Advantages and Disadvantages of the Dual Cooling Source Type Precision Air Conditioner
Advantages: The dual systems are backups for each other, with high reliability and good energy-saving effect.
Disadvantages: There are many components, the initial investment cost is high, and the advantages are not significant.
The dual cooling source type precision air conditioner is mostly used in medium and large-sized switching computer rooms and mobile computer rooms, and is also widely used in computer rooms and telecommunications computer rooms (IDC).
Free Cooling Type Precision Air Conditioner
The free cooling type precision air conditioner can be regarded as a type of water-cooled air conditioning system, mainly using a common ethylene glycol refrigeration system for refrigeration.
It is composed of an indoor unit, an outdoor unit, and an ethylene glycol solution.
When the outdoor temperature is lower than the set value, the ethylene glycol refrigerant can directly and freely provide energy-saving refrigeration.
At this time, the ethylene glycol circulates in the refrigeration pipeline, and the refrigerant circuit and the ethylene glycol circuit perform refrigeration simultaneously, which can reduce the energy consumption of the compression refrigeration system. This system has two working modes, the partial free cooling mode and the full free cooling mode.

The ethylene glycol free cooling type precision air conditioner is installed with a dry cooling tower outdoors, which is similar to the outdoor unit of the air-cooled air conditioning system, except that the substances in the pipeline are different. The former is hot water, and the latter is a high-temperature refrigerant.
Advantages and Disadvantages of the Ethylene Glycol Free Cooling Type Precision Air Conditioner
Advantages: The refrigeration efficiency is higher than that of the air-cooled type, and it can save energy and reduce emissions.
Disadvantages: It cannot be used in real-time, and there are requirements for the outdoor temperature.
The free cooling type precision air conditioner is suitable for areas in the north that require cooling throughout the year, and for energy-saving renovations of Internet IDC computer rooms, etc.
The above-introduced types of precision air conditioners have their own advantages in corresponding refrigeration methods. Users need to comprehensively consider and choose the best solution for themselves according to their own needs and relevant environmental conditions.