free cooling chiller

How Free Cooling Chillers Work​
Free cooling chillers take advantage of cooler ambient air or water temperatures to cool the process fluid, reducing or eliminating the need for mechanical refrigeration. There are two main types of free – cooling operation: air – side free cooling and water – side free cooling.​

Air – Side Free Cooling​
Working Principle: In air – side free cooling, when the outdoor air temperature is lower than the required return water temperature of the cooling system, the chiller bypasses the refrigeration cycle. Instead, it uses fans to draw in the cooler outdoor air. This air passes over the heat exchanger, where it absorbs heat from the warm return water. As the heat is transferred from the water to the air, the water cools down. The cooled water is then circulated back to the system to provide cooling. For example, in a data center, when the outside air is cold enough during winter or in cooler climates, the air – side free – cooling system can be activated, significantly reducing the load on the mechanical refrigeration components.​
Components Involved: Key components of air – side free – cooling systems include outdoor air intake louvers, fans, heat exchangers, and dampers. The louvers control the flow of outdoor air into the system, while the fans ensure proper air circulation over the heat exchanger. Dampers are used to regulate the amount of air entering the system and to isolate the free – cooling section from the rest of the chiller when it’s not in use.​
Water – Side Free Cooling​
Working Principle: Water – side free cooling relies on a source of cooler water, such as a cooling tower or a body of water (in some cases). When the temperature of the available water source is lower than the required temperature of the process fluid, a heat exchanger is used to transfer heat from the process fluid to the cooler water. The process fluid flows through one side of the heat exchanger, while the cooler water from the external source flows through the other side. Heat is transferred across the heat – exchanger surface, cooling the process fluid. The heated water from the external source can then be either discharged (in the case of a once – through system) or returned to the cooling tower to be cooled again and reused in a closed – loop system.​
Components Involved: Water – side free – cooling systems typically include a heat exchanger (such as a plate – and – frame or shell – and – tube heat exchanger), pumps to circulate the process fluid and the external water source, and valves to control the flow. A cooling tower is often a crucial component when the external water source needs to be cooled and recycled.​

Types of Free – Cooling Technologies​
Dry Coolers with Free – Cooling​
Technology Overview: Dry coolers are essentially air – cooled heat exchangers. In a dry – cooler – based free – cooling system, the process fluid (usually water or a water – glycol mixture) is circulated through the tubes of the heat exchanger. Outdoor air is blown over the outside of the tubes by fans, transferring heat from the fluid to the air. When the ambient air temperature is low enough, this system can operate in free – cooling mode, providing cooling without the need for a traditional refrigeration compressor. These systems are relatively simple and require less maintenance compared to some other free – cooling technologies, as they don’t involve complex water treatment or additional refrigeration components.​
Applications: Dry coolers with free – cooling are commonly used in industrial processes where a relatively low – temperature cooling solution is required, such as in the cooling of electrical equipment, small – scale manufacturing processes, and some commercial buildings with moderate cooling loads.​
Adiabatic Free – Cooling​
Technology Overview: Adiabatic free – cooling combines the principles of air – side free cooling with evaporative cooling. In this system, when the outdoor air is drawn in, it passes through a wet pad or a series of wet surfaces. As the air comes into contact with the water on these surfaces, some of the water evaporates. Evaporation is a cooling process that lowers the temperature of the air. This cooler, more humid air then passes over the heat exchanger, where it cools the process fluid more effectively than regular air – side free cooling. Adiabatic free – cooling can operate in a wider range of ambient temperatures compared to simple air – side free cooling, as the evaporative process helps to lower the air temperature even when the initial ambient temperature is relatively high.​
Applications: Adiabatic free – cooling is popular in data centers, especially in regions where the climate is dry. It can significantly reduce the energy consumption of the cooling system while still maintaining the required temperature for the servers. It is also used in some industrial applications where a more efficient free – cooling solution is needed within a specific temperature range.​
Chilled – Water – Based Free – Cooling with Thermal Energy Storage​
Technology Overview: This type of free – cooling system incorporates thermal energy storage, usually in the form of ice or chilled – water storage tanks. During periods of low ambient temperature (such as at night), the free – cooling system is used to cool water and store it in the tank as chilled water or ice. During the day, when the ambient temperature rises and free – cooling is no longer sufficient or not available, the stored chilled water or the melting ice is used to cool the process fluid. This allows the system to take advantage of off – peak free – cooling opportunities and store the cooling energy for use during peak demand periods, reducing the reliance on mechanical refrigeration throughout the day.​
Applications: Chilled – water – based free – cooling with thermal energy storage is widely used in large commercial buildings, hospitals, and large – scale industrial facilities. These places often have significant and variable cooling demands throughout the day, and this technology helps to balance the load and reduce overall energy consumption.​
Applications of Free – Cooling Chillers​
Data Centers​
Benefits: Data centers require continuous cooling to maintain the optimal operating temperature of servers and other IT equipment. Free – cooling chillers can significantly reduce the energy consumption of data – center cooling systems, which are often one of the largest energy consumers in these facilities. By using free – cooling during cooler periods, data – center operators can cut down on the use of mechanical refrigeration, resulting in lower electricity bills and a reduced carbon footprint. For example, in a large data center, the implementation of free – cooling can lead to energy savings of up to 30 – 50% depending on the local climate and the efficiency of the free – cooling system.​
Implementation: In data centers, free – cooling systems are often integrated with the existing chilled – water distribution infrastructure. Air – side free – cooling may be used when the outdoor air quality is suitable, and water – side free – cooling can be combined with cooling towers or other water sources. Thermal energy storage can also be incorporated to ensure a continuous supply of cooling during peak periods or when free – cooling is not immediately available.​
Commercial Buildings​
Benefits: In commercial buildings such as offices, shopping malls, and hotels, free – cooling chillers can provide an energy – efficient way to cool the interior spaces. By reducing the reliance on mechanical refrigeration, building owners can lower their operating costs and improve the sustainability of their buildings. Free – cooling is especially effective in buildings located in regions with cooler climates or during the cooler seasons.​
Implementation: Free – cooling systems in commercial buildings can be designed to work in conjunction with the building’s HVAC (Heating, Ventilation, and Air Conditioning) systems. For example, air – side free – cooling can be used to pre – cool the outdoor air before it enters the building, reducing the load on the air – conditioning units. Water – side free – cooling can be used to cool the chilled – water used for space cooling, providing an efficient and cost – effective solution.​

Industrial Processes​
Benefits: Many industrial processes require cooling for equipment, products, or production lines. Free – cooling chillers can help industrial facilities reduce their energy costs and improve their overall efficiency. By using free – cooling when possible, industries can also comply with environmental regulations and reduce their impact on the environment. For instance, in the food and beverage industry, free – cooling can be used to cool production equipment, reducing the energy consumption associated with maintaining the proper temperature for food processing.​
Implementation: The implementation of free – cooling in industrial processes varies depending on the specific requirements of the industry. In some cases, dry coolers with free – cooling may be sufficient, while in others, more complex water – side free – cooling systems with thermal energy storage may be needed. The choice of free – cooling technology depends on factors such as the required cooling temperature, the available water sources, and the ambient climate conditions.​
Factors to Consider When Choosing a Free – Cooling Chiller​
Climate Compatibility​
Ambient Temperature Range: The local climate is a crucial factor in determining the effectiveness of free – cooling. In regions with long, cold winters and mild summers, free – cooling can be used for a significant portion of the year. However, in warmer climates, the period during which free – cooling is available may be limited. It’s important to analyze the historical temperature data of the location to estimate the potential savings and the feasibility of implementing free – cooling. For example, in a location where the outdoor air temperature is below the required return water temperature for only a few months a year, the investment in a free – cooling system may not be as cost – effective compared to a location with a more favorable climate.​
Humidity and Air Quality: Humidity levels can affect the performance of free – cooling systems, especially those that rely on air – side free – cooling. High humidity can reduce the effectiveness of evaporative cooling in adiabatic systems and may also lead to condensation issues in some heat exchangers. Additionally, poor air quality can cause fouling of heat exchangers, reducing their efficiency over time. Therefore, it’s necessary to consider the local humidity and air – quality conditions when choosing a free – cooling chiller and select appropriate models or implement additional filtration and treatment measures if required.​
Cooling Load Requirements​
Size and Capacity: Determine the cooling load of the application accurately. This includes considering the peak cooling load, the average cooling load, and the load profile throughout the day and the year. The free – cooling chiller should be sized to meet the cooling requirements during the periods when free – cooling is available. If the chiller is undersized, it may not be able to provide sufficient cooling, while an oversized chiller can lead to higher initial costs and potentially inefficient operation. For example, in a large – scale industrial facility with a high and variable cooling load, a free – cooling chiller with a large capacity and the ability to adjust its output according to the load may be required.​
Temperature Control: Different applications have different temperature – control requirements. Some processes may require very precise temperature control, while others can tolerate a wider temperature range. When choosing a free – cooling chiller, ensure that it can maintain the required temperature within the specified tolerance. Some free – cooling systems may require additional control mechanisms or integration with existing temperature – control systems to achieve the desired level of accuracy.​
System Integration​
Compatibility with Existing Infrastructure: If the free – cooling chiller is to be added to an existing cooling system, it’s essential to ensure compatibility with the existing infrastructure. This includes factors such as the type of refrigerant used (if any), the piping and ductwork layout, and the control systems. For example, if the existing system uses a particular type of chilled – water distribution system, the free – cooling chiller should be able to interface with it seamlessly. Compatibility issues can lead to complex and costly retrofits, so careful planning and assessment are necessary.​
Control and Monitoring: A good free – cooling chiller should have an effective control and monitoring system. This allows the operator to switch between free – cooling and mechanical – cooling modes as needed, adjust the system settings based on the ambient conditions and the cooling load, and monitor the performance of the chiller. Advanced control systems can optimize the operation of the free – cooling chiller, maximizing energy savings and ensuring reliable operation.​
Installation, Operation, and Maintenance of Free – Cooling Chillers​
Installation​
Location: Select an appropriate location for the free – cooling chiller. For air – side free – cooling systems, ensure good air circulation and access to the outdoor air. Avoid installing the chiller in areas with restricted airflow or near sources of pollution. For water – side free – cooling systems, proximity to a suitable water source (such as a cooling tower or a water main) is important. Also, ensure that there is enough space for installation, maintenance, and future expansion of the system.​
Piping and Ductwork: Proper installation of piping and ductwork is crucial for the efficient operation of the free – cooling chiller. For water – side systems, use pipes and fittings that are rated for the operating pressure and temperature of the system. Ensure that all connections are tight to prevent leaks. In air – side systems, the ductwork should be designed to minimize air resistance and ensure uniform air distribution.​
Electrical and Control Connections: Connect the chiller to the electrical supply according to the manufacturer’s instructions and local electrical codes. Install the control system properly, ensuring that all sensors, actuators, and controllers are functioning correctly. Calibrate the control system to ensure accurate operation and reliable switching between free – cooling and mechanical – cooling modes.​
Operation​
Mode Switching: Understand the different operating modes of the free – cooling chiller and how to switch between them. The chiller should be able to automatically detect when the ambient conditions are suitable for free – cooling and switch to that mode. However, in some cases, manual override may be required. Operators should be trained on the proper procedures for mode switching to ensure efficient and safe operation of the system.​
Monitoring and Adjustment: Regularly monitor the performance of the free – cooling chiller, including parameters such as the ambient temperature, the temperature of the process fluid, the flow rates of the air or water, and the energy consumption. Based on the monitoring results, adjust the system settings as needed. For example, if the cooling load decreases, the operator may reduce the speed of the fans or pumps to save energy.​
Maintenance​
Regular Cleaning: Clean the heat exchangers, air filters, and other components of the free – cooling chiller regularly. Fouling of heat exchangers can significantly reduce their efficiency, so it’s important to remove any dirt, debris, or scale that accumulates on the surfaces. Air filters should be replaced or cleaned according to the manufacturer’s recommendations to ensure proper air flow.​
Component Inspection and Replacement: Periodically inspect components such as fans, pumps, valves, and sensors for signs of wear, damage, or malfunction. Replace any worn – out or damaged components in a timely manner to prevent system failures. For example, if a fan motor is making unusual noises or not providing the required air flow, it should be repaired or replaced.​
Refrigerant and Fluid Checks (if applicable): If the free – cooling chiller has a refrigeration component or uses a specific fluid (such as a water – glycol mixture), regularly check the refrigerant levels, pressures, and the quality of the fluid. Top up or replace the refrigerant or fluid as needed, following the manufacturer’s guidelines.​
Conclusion​
Free – cooling chillers offer a sustainable and cost – effective alternative to traditional mechanical refrigeration for a wide range of applications. By understanding how they work, the different types of free – cooling technologies available, their applications, and the key factors to consider when choosing, installing, operating, and maintaining them, users can make the most of free – cooling to reduce energy consumption, lower operating costs, and minimize their environmental impact. Whether for data centers, commercial buildings, or industrial processes, free – cooling chillers have the potential to transform cooling systems into more efficient and eco – friendly solutions.