Chilled Water System: Basics, Working Principle Diagram, Types and More

Figure 1: Industrial water chiller.

A chilled water system is a type of HVAC (heating, ventilation, and air conditioning) system that provides cooling through the circulation of chilled water. It is commonly used in large commercial and industrial applications, such as data centers, hospitals, and manufacturing plants.

In this article, we will discuss everything you need to know about chilled water systems, including their components, operation, maintenance, and advantages.

1. Components of a Chilled Water System

A chilled water system consists of several components that work together to provide cooling. Some components include the following:

1. Chiller: The chiller is the heart of the chilled water system. It is a machine that removes heat from the water and transfers it to a refrigerant. It consists of a compressor, evaporator, condenser, expansion valve, etc.

2. Pumps: Pumps are used to circulate the chilled water from the chiller through the building's HVAC system.

3. Pipes: Pipes are used to transport the chilled water from the chiller through the building's HVAC system.

4. Air Handling Units: Air handling units are used to distribute the chilled air throughout the building. They contain fans, filters, and more that regulate the temperature and humidity of the air.

Figure 2: Chiller composition structure.

1.1 What is Chilled Water

Chilled water in a chiller refers to the water that has been cooled down to a specific temperature by the chiller unit. The chilled water is the cooling medium that is circulated through the building's HVAC system to provide air conditioning.

The temperature of the chilled water in the chiller is typically set to a specific value based on the cooling requirements of the building. The temperature may vary depending on the time of day, the season, or the occupancy of the building. The chilled water temperature is usually maintained within a narrow range to ensure optimal cooling performance and energy efficiency.

Chilled water in a chiller is a key part of a chilled water system that provides efficient and reliable air conditioning for large commercial and industrial applications.

2. Working Principle of a Chilled Water System (How Does a Water Chiller Work)

A chilled water system works by using a refrigeration cycle that involves the evaporation and condensation of a refrigerant. The refrigerant absorbs heat from the water, causing it to cool down and become chilled water. The chilled water is then circulated through the air handling units in the building, where it cools the air.

After leaving the evaporator and compressed by a compressor, the refrigerant is circulated to a condenser where the heat is released to the air or water. Later the refrigerant flows through the expansion valve to lower its pressure and temperature. Then it enters the evaporator to absorb heat from the water again.

Figure 3: Chilled water system diagram.

1. Compressor 2. High pressure gauge 3. Air-cooled condenser 4. Dry filter 5. Expansion valve 6. Low pressure gauge 7. Make-up water 8. Water tank 9. Sewage outlet 10. Frozen water circulation pump 11. Frozen water inlet 12. Evaporator 13. Frozen water outlet

3. Types of Chilled Water System

Air-Cooled Chilled Water System
An air-cooled chilled water system uses air as the cooling medium to remove heat from the condenser. The system consists of a chiller (including an air-cooled condenser, a evaporator, a compressor, etc.), air handling unit, pump and a set of pipes to circulate the chilled water.

Air-cooled systems are typically used in smaller applications where water is not readily available or practical to use, such as small commercial buildings or residential complexes.

Figure 4: Air-cooled chiller.

Water-Cooled Chilled Water System
A water-cooled chilled water system uses water as the cooling medium to remove heat from the condenser. The system consists of a chiller (including a water-cooled condenser, a evaporator, a compressor, etc.), cooling tower, pumps, and a set of pipes to circulate the chilled water.

Water-cooled systems are typically used in larger commercial and industrial applications where high cooling capacity is required, such as hospitals, data centers, and manufacturing plants.

Figure 5: Water cooled chiller unit.

4. Maintenance of a Chilled Water System

Proper maintenance of a chilled water system is essential for its efficient and reliable operation. The following are some maintenance tasks that should be performed regularly:

1. Cleaning: The cooling tower and chiller should be cleaned regularly to remove debris and prevent clogging of the water passages.

2. Water Treatment: The water in the chilled water system should be treated regularly to prevent corrosion, scaling, and bacterial growth.

3. Filter Replacement: The filters in the air handling units should be replaced regularly to ensure proper air flow and quality.

4. Pump Maintenance: The pumps in the chilled water system should be inspected regularly for leaks, worn parts, and proper operation.

5. FAQs

5.1 What is a Chilled Water System?

A chilled water system is a type of HVAC (heating, ventilation, and air conditioning) system that uses chilled water to provide cooling to a building or process.

The system consists of a chiller, which cools the water, and a network of pipes, pumps, and air handling units that distribute the chilled water to different areas of the building. The chilled water is circulated through the building, where it absorbs heat from the air, and then returns to the chiller to be cooled again.

5.2 How Does a Chiller Water System Work?

A chiller water system works by circulating chilled water through a network of pipes and air handling units to provide cooling to a building or process. The chiller cools the water by removing heat from it using a refrigeration cycle. The chilled water is then pumped through the system to air handling units or fan coil units in different zones of the building.

The chilled water absorbs heat from the air, which is then distributed back to the chiller to be cooled again. The process is continuous, with the chilled water circulating through the system and providing cooling as necessary.

5.3 What are the Two Types of Chilled Water System?

The two types of chilled water systems are air-cooled and water-cooled systems.

In an air-cooled system, the chiller uses air to dissipate the heat generated by the refrigeration process.
In a water-cooled system, the chiller uses water to dissipate the heat generated by the refrigeration process.

5.4 What is the Difference between Cold Water and Chilled Water?

Cold water and chilled water are both used for cooling purposes, but there is a difference between the two. Cold water is typically water that is cooled to a temperature that is slightly lower than room temperature, usually between 5-15°C (41-59°F). It is commonly used for comfort cooling in residential and commercial buildings.

Chilled water, on the other hand, is water that is cooled to a much lower temperature, usually between 4-7°C (39-45°F). It is used in larger commercial, industrial, and institutional settings, where precise temperature control is required.

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