HVAC Chilled Water Systems

understand HVAC Chilled Water Systems

Fri Aug 19, 2022

Chilled Water System Basics
Chilled water systems in residential HVAC systems are extremely rare. A typical chiller uses the process of refrigeration to chill water in a chiller barrel. This water is pumped through chilled water piping throughout the building where it will pass through a coil. Air is passed over this coil and the heat exchange process takes place. The heat in the air is absorbed into the coils and then into the water. The water is pumped back to the chiller to have the heat removed. It then makes the trip back through the building and the coils all over again. 
Chilled water systems circulate cold water of between 40º F to 45º F through the air to water air handlers. As the air is cooled and passed through the finned coil, it gives up heat to the water. Most chilled water systems are designed so that, at the maximum air-conditioning load, the water leaving the coil has been heated 10º F.
Chilled water systems - In a chilled-water system, the entire air conditioner is installed on the roof or behind the building. It cools water to between 40- and 45-degrees Fahrenheit (4.4 and 7.2 degrees Celsius). The chilled water is then piped throughout the building and connected to air handlers. This can be a versatile system where the water pipes work like the evaporator coils in a standard air conditioner. If it's well-insulated, there's no practical distance limitation to the length of a chilled-water pipe. 

Advantages of chilled water systems. 

Also, using a chilled water system provides better energy efficiency than smaller, individual systems. That is another important aspect. While chillers might be a more expensive initial investment, they allow have a more efficient system and save money on energy consumption. Therefore, they allow a good return on the investment in a relatively quick timeframe. 

Chilled water systems also produce less noise than air ducts, which improves comfort for occupants. This is a significant advantage in office buildings, where constant noise and vibration from an air duct system can cause distraction and lower productivity. 

For a specified cooling load, a chilled water system normally provides a higher efficiency than an air conditioning system with only air ducts. This can be a significant advantage in commercial buildings, where the extra efficiency yields thousands of dollars in monthly savings. 

Disadvantages of chilled water systems. 

One of the common problems in chilled water systems is low delta T syndrome. The problem is low chilled water return temperature that can be caused by multiple different issues such as dirty filters/coils, imbalance water flow and oversized air handling units. 

These complex machines require a lot of maintenance to keep them in good working order. If proper steps aren’t taken, the chiller can corrode, clog, lose efficiency, or experience several other issues. For example, if proper water treatment isn’t maintained or if open cooling towers aren’t cleaned, sediment or particulates can be introduced to the system, causing clogged pipes and poor heat transfer. An air-cooled chiller’s condenser can be blocked by debris or become caked in dirt, which also lowers efficiency. 

Disadvantages of air-cooled engines: a large amount of power is used to drive the cooling fan. -Engines give low power output. -Cooling fins under certain conditions may vibrate and amplify the noise level. -Cooling is not uniform. -Engines are subjected to high working temperatures. 

Chilled water systems for commercial buildings. 

Chilled water systems are made up of several components. The system doesn't work even when one of the components fails. Since chilled water systems have high efficiency, they are used in many large buildings. I thought chilled water systems are cool and thus, I did some research. 

Chilled water systems provide comfort to mainly commercial buildings and are typically cheaper to operate than Direct Expansion (DX) systems. While many buildings have DX systems in the way of large rooftop units, the cost of installation is generally cheap for the DX systems because all that is required to install them is ductwork and electrical service to the unit. With chilled water systems, chilled water piping must be installed throughout the building, and this can be far more expensive to install over the plain old DX rooftop units which supply conditioned air to a VAV system that has electric reheat in them. 

These systems feature many other supportive components including controls, pumps, refrigerant/ water treatment, filtration devices and air eliminators/ air separators. We could divide applications of chilled water systems into commercial and industrial. Campuses, large commercial buildings, and similarly enormous sized projects require chilled water systems for their cooling equipment. Industries are faced with stringent EPA control requirement and worsening utility cost situations. In a bid to reduce these costs and comply with requirements, they are turning to chilled water systems. The cooling system transfers heat from production processes and industrial equipment. The two most notable components in these applications are chiller (cooling unit) and heat exchanger. The heat exchanger enables the plant equipment and production processes to lose heat to the cooling water. The chiller collects the heat gained from the processes/equipment. This heat can be lost through either a closed loop system or the atmosphere (via cooling towers). If you have any of the following projects, the best chilled-water system could come in handy.

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