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To understand what a chiller system is and how it works in general, it is best to explain how commercial buildings use heating, purification and air conditioning systems to keep the ambient air cool and away from moisture. Modern commercial buildings are looking for an air-conditioning system and its efficient components as part of a larger operation focusing on building performance and durability. Residents of the building likewise have high expectations of the air conditioning system to work in order to provide a comfortable indoor environment, regardless of the external conditions of the building in accordance with the form assigned to it. Chillers have become an essential component of air conditioning systems for a wide range of commercial buildings such as hotels, restaurants, hospitals, sports centers, manufacturing plants and others. The industry has long recognized that chiller systems are the largest consumer of electrical energy in most buildings. They can easily consume more than 50% of the total power consumption of the seasonal intervals. According to the US Department of Energy (DOE), chillers can consume approximately 20% of the electricity generated in North America. In addition, the DOE estimates that this amount could increase by up to 30% due to various performance failures. These known failures can cost companies, firms, and buildings billions of dollars a year.
In general, the work of a chiller is to facilitate the transfer of heat from the interior to the exterior. Because this heat exchanger moves between the components of the chiller, it relies on the physical phase of the coolant or refrigerant. Chillers can definitely be the heart of any air conditioning system.
How does a chiller work?
The chiller operates on the basis of steam absorption or steam compression. The chillers generate a constant flow of refrigerant to move to the cooling section of the system and the water cooling tower at the desired temperature of 10 ° C or 50 ° F. The refrigerant is then pumped to other parts to dissipate heat from a part of the building (for example, machinery, processing equipment, etc.) as it returns to its starting point.
A chiller uses a mechanical compression cooling system that is connected to a water cooling tower by a device called an evaporator. The refrigerant is between the evaporator, the compressor, the condenser and the chiller expansion valve in rotation and motion. A thermodynamic process occurs in each of the named components. The evaporator acts as a heat exchanger, transferring the heat captured by the cooling stream to the refrigerant. As the heat transfer takes place, the refrigerant reaches the gas phase from a low-pressure liquid, while naturally, the temperature of the device decreases as the ambient heat is removed by the refrigerant phase change process.
The refrigerant then leads to the compressor, which has multiple functions. The first function of the compressor is to remove refrigerant from the evaporator and ensure that the pressure inside the evaporator is low enough to absorb heat properly. The second function of the compressor is to increase the gas refrigerant pressure in the outlet solution to ensure that the temperature remains high enough to release heat when it reaches the condenser. The refrigerant in the condenser returns to the liquid phase. Latent heat, which is transferred from the gas to the liquid due to the change of the refrigerant phase, is transferred out of the environment by a coolant (air or water).
Types of chillers
As explained, chillers can facilitate the transfer of heat generated when the refrigerant phase changes from air to liquid in two ways (by water or air). Therefore, chillers can use two different types of condensers: air-cooled and water-cooled.
Cool air chillers are similar to radiators that cool car engines. They use a motorized blower to pass air through a network of refrigerant rows and rows. Although cool air condensers are specifically designed for high ambient temperatures, they require an environment of 35 ° C (95 ° F) or less to be effective.
Coldwater condensers also function like cold air condensers but perform heat transfer in two separate steps. First, heat moves from the gas refrigerant to the water inside the condenser. Then, the hot water inside the condenser is pumped to the cooling tower. Where the heat of the process is finally released into the open space.
Cool water chillers:
All types of cold water chillers use a condenser that is connected to a cooling tower. These chillers are typically used for medium or large facilities that have sufficient water storage. Coldwater chillers can have a more stable performance for air conditioning of commercial or industrial spaces due to their relative independence from changes in ambient temperature. Cooling water chillers are produced in different sizes and volumes, from a capacity of 20 tons to capacities of several thousand tons, the latter of which is suitable for cooling the largest facilities such as airports and commercial centers.
A typical cold water chiller uses a cycle between the condenser and the cooling tower to compress the refrigerant. This chiller carries a refrigerant that depends on the temperature of the water entering the condenser and the intensity of the current, which operates in proportion to the temperature of the bubble. Since the temperature of the wet bubble is always lower than the temperature of the dry air, the refrigerant in the cold water chiller can operate at a temperature and pressure different from that of the cold air chillers. Therefore, cold water chillers can be more useful.
Coldwater chillers are typically installed indoors to keep them away from environmental factors, so they can have a longer useful life. Coldwater chillers are the only option for large installations and structures. However, compared to air-cooled chillers, the additional cooling tower system for the water-cooled chiller increases the cost and requires more maintenance.
Cool air chillers:
Cool air chillers use a condenser that is cooled by ambient air. Therefore, cool air chillers are more commonly found in small or medium-sized installations and environments where space is limited. A cool air chiller can be the best option for environments with water shortages and constraints.
A typical cool air chiller can use propeller fans or a mechanical refrigerant cycle to draw in ambient air to compress the refrigerant through the fan coil. Condensation of gas refrigerant in cold air chillers allows heat transfer to the outside space.
Cool air chillers have a significant advantage due to their low installation cost. Also, their relative simplicity compared to other types of cold water chillers leads to their ease of maintenance. Cool air chillers take up less space but are often installed outside buildings and facilities. Therefore, environmental factors can affect their useful life.
The comprehensive nature of air-cooled chillers reduces maintenance costs, and their relative simplicity, in addition to taking up little space, offers significant benefits in many types of projects.
In the second part of the article, a comprehensive guide to the types of chillers, the optimization of chillers for maximum efficiency is examined.
Source:
https://www.hvacinvestigators.com/webinars/the-basics-of-chillers-how-they-work-where-theyre-used-and-common-problems
