What is a Water Chiller?
A water chiller, sometimes known as a chilled water system, is a refrigeration system that uses water as a secondary refrigerant. This configuration is often used in complex and high capacity HVACR (heating, ventilation, air conditioning, and refrigeration) systems. Water chillers are used in numerous applications, including:
- District cooling
- Centralized A/C
- Hydroponics
- Food and beverage processing
- Pharmaceuticals and medical industries
- Cold storage options
- Thermal Energy Storage (TES) systems
- Machining processes such as waterjet cutting, laser cutting, welding, etc.
- Plastic processing
Unlike water chillers, directly-expansion (DX) systems cool the air directly and do not utilize a secondary refrigerant. In a DX system, air passes over the evaporator and is cooled.
DX systems are more suitably used in smaller-scale applications, such as residential cooling systems and small refrigeration systems or freezers.
What is the working principle of a water chiller?
A water chiller system has two loops or circuits: a refrigeration loop and a chilled water loop. Awareness of the function of each component is crucial in selecting an appropriate industrial chiller for commercial HVAC, process cooling, and manufacturing purposes.
The refrigeration loop is where cooling occurs. This sub-system is composed of the thermodynamic processes and flow of refrigerant responsible for generating mechanical cooling.
The chilled water loop is a distribution system that delivers cold water to consumer units and/or process cooling. Each loop must work in unison to achieve good heat dissipation, reduce heat extraction from surrounding medium, and be as energy-efficient as possible.
Layering the basic understanding of how these circuits interact together, will allow for a solid foundation in order to evaluate chiller performance, efficiency (EER, COP), and overall suitability (limited sample cooling capacity).
The Vapor Compression Cycle
The refrigeration cycle is based on the typical vapor compression refrigeration cycle, the most common cooling technology for water-cooled and air-cooled chillers in HVAC systems and industrial facilities.
The vapor compression refrigeration cycle uses a refrigerant, which can change from the liquid state to the gaseous state, to absorb heat (cooling) globally in the utilizing heat exchangers.
Components of the refrigeration cycle (compressor, expansion valves) provide means to control the refrigerant pressure and temperature.
The refrigeration cycle consists of distinct operations; knowing the progression of a vapor compression refrigeration cycle allows the engineer to size chiller units appropriately, minimize energy usage, and properly provide reliable process cooling for industrial processes.
Compression
Initially, the refrigerant exists as a low-pressure vapor, absorbing evaporator heat. It usually has a temperature equal to the ambient air or the process fluid.
The compressor is often called the “heart” of the chiller. It raises the refrigerant pressure, and consequently temperature, when the vapor refrigerant enters the compressor.
Different compressor types (scroll, screw, centrifugal, and reciprocating) are chosen based on cooling capacity, efficiency, and application.
The required motor input to drive the compressor is the single most important energy consumption point in the refrigerant cycle, affecting lots of other aspects related to operating costs and performance of industrial water chillers.
When the pressure of the refrigerant is increased, some mechanical energy must be added by the compressor to the refrigerant. This is the first and most critical step in continuing the cooling cycle.
Condensation
The high-pressure component of the refrigeration unit is the condenser, which functions as a heat exchanger to reject thermal energy.
This type of equipment utilizes a temperature difference between the heated refrigerant and the cooler ambient air or water to transfer heat from the refrigerant to the surrounding environment.
The condenser not only must reject heat absorbed in the chilled water loop, but to also reject heat created during compression. Therefore, it is imperative this component operates successfully in regards to chiller function and energy efficiency.
The rejected energy is removed by the environment, which constitutes the heat sink. Depending on the style of chiller, the environment could either be the outside air (in air-cooled chillers) or a dedicated closed water loop or a cooling tower (in water-cooled chillers).
One challenge in selecting is mainly the choice between air-cooled or water-cooled chillers, which is based on various aspects including the location of the facility, the availability of water, noise requirements, and expenses related to installation and operations based on cooling method.
Both the condensing temperature and the condensing pressure of refrigerant pressure will drop based on their relationship to the chilled water system.
As the refrigerant turns into a liquid state, it loses heat to the condenser until the refrigerant reaches the saturation point of the condensing pressure and condensing temperature; this is important when understanding the relationship between saturation temperature associated with heat rejection by the chiller.
Systems must also consider the working conditions for optimal refrigerant selection (R134a, R410A, etc.) depending on sustainability considerations, as well as regulatory rules associated with using each refrigerant.
Expansion
After condensation occurs, the refrigerant is in its liquid form under high pressure and at a temperature similar to the outside cooling medium.
As liquid refrigerant enters the expansion device (thermal expansion valve or capillary tube) with its sudden reduction in pressure and temperature, the refrigerant immediately expands allowing permitting a part of the refrigerant to vaporize and produce the cold temperatures required for heat transfer in the evaporator.
When the expansion device permits only a limited amount of heat to enter during refrigeration expansion, the efficiency of the refrigeration system retains maximum cooling function. This has great significance for efficiency in commercial chilled water systems.
The expansion device closely regulates the flow of refrigerant which must be done at a high degree of accuracy to ensure smooth operation of the system; excessive or inadequate flow can result in freeze-up of the evaporator or slugging in the compressor.
The performance of the expansion device, correct sizing and proper maintenance are greatly reflected in achieving a reliable and long service life particularly for industrial chillers that operate variable loads.
Evaporation
The evaporator represents the low-pressure side of the system, the phase in which heat is removed. The refrigerant acts in place of the chilled water or brine, removing heat from those phase change fluids, and reducing the temperature of the process fluids to the desired set point.
This feature helps to keep the process fluid at the required temperature for supporting cooling loads in commercial HVAC, food process, plastic molding, and data center systems.
The evaporator presents the refrigeration cycle, where the refrigerant changes phase by absorbing heat energy, that allows an efficient way to remove thermal energy from the air in space you are trying to cool, the waste heat from an industrial process, or thermal energy from machinery that needs to be removed.
After evaporation, the refrigerant circulates as a low pressure vapor ready to start the refrigeration cycle with the compressor.
Today in the global HVAC and process cooling markets, nearly 90% of installations include vapor compression water chillers because of their high energy efficiency and accurate control of temperatures.
Alternative refrigeration cycle technologies (i.e. absorption cycle) exist for specialized situations. Absorption chillers are driven by heat and can be found in a situation where there is steam or waste heat readily available.
Absorption chillers usually use hot water as the heat source. This is an environmentally friendly, less complex, and lower maintenance technology that are often found in district cooling and combined heat and power (CHP) plants.
Absorption Chillers
Absorption chillers provide a unique technology for industrial cooling because they utilise a thermochemical absorption process, which is thermally-driven, instead of mechanical compression.
With commonly used working pairs such as lithium bromide-water or ammonia-water, absorption chillers operate with extremely low electric consumption, since they exploit hot waste sources (including steam or hot water from an existing process).
The best absorption cooling solutions are sought-after in the industry because of their ability to reliably perform, operate in an environmentally friendly way, and their opportunity to reduce greenhouse gas emissions, primarily in large-scale commercial and municipal applications.
They are the best type of cooling solution for facilities with the goal of decreasing operational costs by implementing energy efficiency opportunities, while working towards sustainability & green building initiatives.
The Chilled Water Loop
The chilled water loop represents the secondary or secondary heat rejection mode of heat transfer path in a water chiller system. The chilled water loop is the system operating with water (water only, water with antifreeze; brine or glycol solution) as the primary medium for cooling.
The chilled water is circulated and pumped through an air handler, a process heat exchanger, or a process equipment jacket to reject heat from a space or process, returning to the evaporator for cooling again.
The chilled water loop facilitates centralized cooling and is practical and cost effective when distributing cooling loads throughout large buildings.
Chilled water loops are essential in commercial properties, medical facilities, industrial facilities, and complex buildings that require process cooling.
For demanding applications or those requiring much colder conditions, i.e. -20F (-29C), as in pharmaceuticals, chemical processing or the food industry, there may be undesirable ice formation in piping and in order to not interrupt the supply of cooling, a cooling agent (glycol, brine, and other additives) may be combined with water.
This cold brine water loop mixed fluid combination(s) establishes a colder fluid density which prevents ice in piping systems, and aids commission agents in preventing faults through continuous operation in subzero operation.
Brine or brine water historically refers to salty water. Today’s antifreeze like ethylene glycol, propylene glycol, and other choices serve as effective antifreeze products comparable to brine and are the most environmentally safe choices available.
Cooling agents can: extend life to equipment, minimize corrosion, and in some case’s optimize heat transfer rates through aforementioned solutions in systems with cooling processes.
Liquid Chiller refers to water chiller units using water-antifreezes as secondary refrigerants; and has special value for specialized low temperature process chiller.
Choosing the proper mixture of fluid determines proper flow rates, pump speeds, overall energy consumption and provides proper circulating water quality through fault conditions of chilled water loops.
In general, chilled water loops utilize two major heat exchanger types: the evaporator that is interfaced with the refrigeration cycle and the cooling coil that removes heat from spaces or processes, while transferring cooled fluid back to the return line, providing further chilled water.
The fluid mechanics and system balance is important to optimizing cooling and consistency through the chilled water loop network of piping.
The cooling coil is fed chilled water from the supply side. Warm air or process fluid is blown over the coil while heat is removed and transferred in to the chilled water, until the cooled water return line is activated for transferring cooled water back into the chilled water piping system.
The temperature difference, also know as the cooling range, is approximately 8-16 degrees Fahrenheit (4 – 9 degrees celcius) and provides a metric/measurement used to size cooling loads, calculating solution volume, sizing pumps and accounting for energy efficiency when loads vary over time.
Understanding the relationship between set point load, fluid and water temperature, and circulating flow rates is fundamental to designing and operate advanced chiller systems that provide noticeable performance and energy savings.
The evaluation of a water chiller should include total cooling capacity (tonnage/or kW), energy efficiency (SEER, EER, COP), footprint, refrigerant type, and unique requirements for the intended application.
Consulting with top manufacturers and experts in the industry will assist in determining the best chiller technology appropriate for the particular process or property (ex. commercial HVAC retrofits, new installations of industrial, and energy updates).
What are the different types of water chillers?
The prior chapter has reviewed the two refrigeration cycles involved in water chillers, namely the vapor compression cycle and the absorption cycle, one type of water chiller. These two cycles provide one type of classification system for water chillers.
There are other classifications based on the type of condenser, type of compressor and type of drive unit that are being used.
It is essential for an understanding of the various classifications for water chillers in choosing a solution for industrial process cooling, components of HVAC systems, commercial buildings or manufacturing.
Evaluating the different types of chillers ensures that the proper chiller is purchased for the cooling application in terms of energy efficiency, performance and economic efficiency for certain cooling needs.
According to Condenser Type
Water chillers can be classified as air-cooled or water cooled, depending on how the chillers reject heat to the environment. The condenser type is critical in respect to overall efficiency, footprint, and environmental impacts of the water chiller system.
Choosing the proper condenser type based on the facilities needs will result in maximum uptime, lower operating costs, and reliable cooling performance.
Air-cooled Water Chiller
Air-cooled water chillers have condensers designed to reject heat from the refrigerant to the ambient (surrounding) air, which acts as the cooling medium.
Air-cooled chillers are particularly useful where water is limited or there is a desire to minimize infrastructure cost, for example, in commercial buildings, hospitals, and smaller manufacturing plants.
While air-cooled chillers have some unique features, a typical air-cooled condenser unit has several finned coils that were designed to maximize the surface area in contact with the air, and a fan or fans to blow air over the fins to promote heat transfer from the refrigerant to the air.
The performance and efficiency of the air-cooled condenser is dependent primarily on the airflow rate over the coils, and upon the dry-bulb temperature of the air.
It is important to note that at higher ambient air temperatures, the power consumption of the air-cooled chiller would generally be higher.
The primary characteristics of air-cooled water chillers are they tend to be simple in design, they have a lower upfront cost in installation, and they tend to be lower in maintenance.
Air-cooled chillers are designed to allow standalone installations without need for any additional infrastructure, (i.e. cooling/tower water supply lines or cooling towers).
Based on total cost of ownership over the lifespan of the chiller, air-cooled chillers will typically be preferred for medium or smaller loads, especially where water conservation is an issue.
Some common applications of air-cooled chillers are for data centers, office buildings, medical facilities, and plastic injection molding.
Water-cooled Water Chiller
Water-cooled water chillers utilize water as the condensing medium. Water is also used for cooling in these particular chillers, so there are normally two separate water loops: a heat sink to absorb heat from the process fluid and cooling tower integration to expel the heat to the outside environment.
This system works particularly well in large cooling projects that require precision with temperature control and requires low energy consumption.
Cooling towers are normally used with water-cooled condensers. Unlike conventional heat exchangers which rely completely on conduction and convection, cooling towers cool water when it is exposed to air.
Cooling towers provide the condenser unit with cooling water to cool the refrigerant using the ‘chilling’ cooling process. This makes it possible to remove large heat loads that are often seen in process cooling systems for HVAC and industrial manufacturing process installations.
Water cooled chillers represent a great options for large industrial plants with a reliable source of cooling water.
Water-cooled chillers operate with a very high cooling efficiency in the condenser compared to air cooled chillers in high ambient temperature environments or larger cooling capacities are required.
Water cooled chillers are just better for stable operation, increased lifespan of the equipment, and more energy efficient operation. They are also increasingly popular options in extremely critical applications such as pharmaceutical processing, food and beverage processing, chemical manufacturing, or a large commercial facilities.
For buyers who are thinking about lifecycle cost of the equipment, twelve we will discuss, including water cooled and air cooled systems.
Water cooled systems have a history of requiring greater maintenance and infrastructure but provide long term lowest operating costs and operational performance for high-capacity, mission-critical industrial applications.
Water cooled systems provide the lowest total cost and are the recommended chiller type for high-performance cooling capacity.
According to Compressor Type
There are a few types of water chiller compressors, namely, centrifugal, screw, scroll and reciprocating. Each compressor type employs a different mechanism to compress refrigerant which affects its energy efficiency, capacity range, noise level, reliability and maintenance over time.
The compressor will vary depending on the cooling capacity required, how often the load changes, and the specific application.
Centrifugal Water Chiller
The centrifugal water chiller is composed of a centrifugal compressor that provides a gas with kinetic energy to raise its pressure – by slowing the fluid down, the centrifugal compressor converts the gas’s kinetic energy to static pressure, or potential energy.
This results in centrifugal compressors being dynamic compressors in our case, and they are very efficient for moving large amounts of refrigerant.
Centrifugal compressors work well with high capacities due to their suitability for large cooling loads which are often seen with mission-critical applications or in ultra-high capacity applications, such as district cooling applications, data centers and large airports, and commercial buildings.
Additionally, centrifugal compressors offer advantageous operational efficiencies– or coefficient of performance (COP) at peak load and with commonly used centrifugal water chillers including VFDs and intelligent controls, some of which offer the best operational efficiency with reliable operation, centrifugal compressors can provide value in any application.
When it is time to select a chiller for ultra-high capacity applications, or mission-critical processes, centrifugal technologies are often recommended due to past performance history and low kW/ton performance.
Screw Water Chiller
Commonly known as helical-rotary water chillers, this type of chiller employs a screw compressor to operate the vapor compression cycle. Screw compressors are one variety of positive-displacement rotary compressors and commonly use two intermeshing helical screws.
When you inject refrigerant into the screws, the volume in the cavities between the two intermeshing screws shrinks while circulation as the refrigerant gas is captured, compressing the refrigerant gas and simultaneously increases the pressure of the refrigerant.
Screw water chillers can eventually provide cooling for small and medium integration projects that perform well at partial loads. Unlike centrifugal and reciprocating compressors screw chillers do not surge at lower loads and maintain performance at varying loads.
The inherent ruggedness of screw chillers with lower vibrations and smaller footprints, make screw chillers desirable for modular process cooling, plastic processing, food and beverage plants, and commercial HVAC due to design flexibility, faster installation, and reliability.
Screw water chillers are a flexible and scalable cooling solution when efficient, constant, and accurate temperature range is critical for cooling loads.
Scroll Water Chiller
Scroll water chillers employ a positive-displacement, rotary compressor that has two interleaved spirals, or scrolls. One scroll is the rotor, and the other scroll is the stator. The rotor does not rotate, but moves eccentrically relative to the stator.
The refrigerant is compressed and moved toward the center and is compressed progressively while trapped in between the two scrolls, resulting in a smooth, quiet, and highly efficient compression process.
Scroll chillers are generally used for small to medium range loads. Since multiple scroll compressors can be packaged together to increase the total capacity of the chiller and scroll chillers can have a coefficient of performance (COP) similar to screw compressors.
For applications requiring varying cooling loads, scroll chillers can employ a range of refrigerant control strategies, including speed control or variable displacement control, to improve their efficiency.
Scroll chillers are compact and operate quietly, making them an ideal choice for medical facilities, laboratories, and commercial air conditioning, and light industrial process cooling.
Scroll chillers are also an excellent choice for energy efficient cooling solutions in LEED certified or green building proposals, due to their low environmental impact and low maintenance.
Reciprocating Water Chiller
Reciprocating water chillers commonly use a piston or plunger to pull in and compress the refrigerant. This makes reciprocating chillers a kind of positive-displacement compressor.
This is the positive-displacement logic, it is where things become somewhat more complicated at the same time as efficiently compressing the refrigerant for instance can create drawbacks such as noise and instances of excessive servicing and wears.
Traditionally reciprocating water chillers have been the chiller type of choice in discussions of refrigeration systems, smaller industrial cooling, and older HVAC applications and systems.
The design of this refrigeration technology is increasingly less popular due to the limitations of the reciprocating compressor.
The demand will always favour the efficiency of the reciprocating compressor, the noisy reputation, limited reliability, limited efficiency, and life expectancy as a compressor. The only difference maker price and ultimate costs versus total cooling capacity.
The newest technologies are evolving to include a scroll compressor or screw compressors that provide better efficiencies and lower maintenance costs; however, it is common place to see older reciprocating models collecting dust in existing legacy systems, replacement markets, or utility-driven price dictated opportunities.
When assessing water chillers for your facility/process you must account for cooling capacity, energy efficiencies, expandable capacity, maintenance capabilities, environmental considerations, and installation footprint.
That being said, GI consultants and engineers are able to help you determine the chiller that is best for the application you are looking for and position your company to achieve the best return on investment across the functional life expectancy of the equipment.
What are the design considerations for water chillers?
Several aspects influence the design of water chiller systems. If the process unit or equipment has predetermined chilled water parameters like temperature and water flow, the design process is not too complicated since cooling capacity is defined.
If it is for HVAC applications however, the traditional design process is much more complex; it involves calculating the cooling load and air parameters, and probably considering the alternative particular design aspects for example, controls, configuration, and piping.
Here are some of the major attributes to specify when designing water chiller systems:
Cooling Load and Cooling Capacity
The cooling load is the rate at which energy or heat must be extracted from the space in order to maintain the desired temperature and humidity levels.
The cooling load is generally expressed in tons of refrigeration (TR or TOR), or in BTU per hour. One ton of refrigeration is equal to 12,000 BTU/hr, or approximately equals to 3.5 kW.
In the air-conditioning and ventilation realm, there are many components influencing the cooling load – solar radiation, heat transfer through the building envelope, outdoor air infiltration, and internal heat loads imposed by occupants, equipment, lighting, and soy on.
There are a multitude of methods for calculating the cooling load: transfer function method (TFM), cooling load temperature differential (CLTD), heat balance method, and time-averaging (TA) method.
The methods can be referenced in ASHRAE Handbooks as well as international standards by organizations such as ISO or EN.
In the case of refrigeration equipment or process cooling applications, the cooling load will vary based on the downstream systems it serves.
While there are variations in the methods and unit processes of heat generation in a given industry, heat load calculation is generally more straightforward than in air-conditioning and ventilation systems.
Equipment cooling specifications and additional design data such as chilled water flow rates or chilled or hot water temperatures are typically provided by manufacturers.
After the cooling load calculation, one can establish the cooling capacity of the chiller unit. Cooling capacity is the rate which the chiller can “cool”; typically set slightly above the calculated cooling load for proper performance.
Chilled Water Supply Temperature and Flow Rate
The first step in ascertaining the chilled water temperature and flow rate is to define the cooling coil details. For HVAC systems, the cooling coil performs the function of exchanging thermal energy between the chilled water and the returning air.
Variables associated with the chilled water flow rate and supply temperature are impacted by air parameters, and both chilled water flow rate and supply temperature are considered along with the cooling load.
Several organizations, including ASHRAE, have established standards and psychrometric formulas available to establish a serviceable list of air parameters.
In refrigeration and process-cooling applications, it is better to consider the application of cooling coils as cooling jackets or coil (sort of) within the system.
Unlike HVAC systems, psychrometric calculations are not needed. Instead, heat exchanger calculations can be used to find the supply temperature and flow rate. There may be other methods applied depending on the application.
Cooling Capacity Control
In evaluating cooling capacity, it is valuable to look at the occurrence, amount and variation of the peak load over time.
In many cases, this will be complicated by different, varying, circumstances and the chiller unit will regularly operate in partial load concurrency. As a result, methods of cooling capacity control should be included in the options considered.
Types of water chillers will control capacity in different ways, for example, scroll water chillers have variable frequency drives (VFDs) or inverter options that can vary the speed of the motor to manage capacity or can also vary displacement through solenoids that either allow or deny the operation of the compressors by altering compression chamber options.
Centrifugal and screw water chillers manage capacity control by the refrigerant flow entering the compressor with inlet guide valves or inlet valves for refrigerant flow. Centrifugal compressor may also have VFDs for capacity control.
Multiple Water Chiller Configurations
In large-scale applications, multiple examples of water chillers may be preferable to a single, large chiller for a number of reasons. These include the following.
Greater Operating Flexibility: Chillers often operate at partial loads. By using multiple chillers, to reduce the capacity, one chiller could be shut down, and the remaining chillers can run at their full volume, thereby sustaining the optimum efficiency of the system.
Reliability: If one chiller were to fail the cooling system would be down until the chiller is repaired or replaced leaving the entire facility with no cooling. In a multiple chiller installation, even if one chiller fails, a cooling capacity remains and extra down time can be avoided by having a spare chiller unit.
Compressor Driver
The compressor driver provides mechanical energy to the compressor in the refrigeration unit. The compressor driver system has two broad categories of compressor drivers electric-driven and engine-driven.
Electric-driven
Electric-driven chillers drive the compressor with an electric motor. Electric-driven means this type of chiller is the most prevalent type mostly because of its use in HVAC applications. Furthermore, electric-driven water chillers can be defined by their fabrication.
Open-type Chillers
An open-type chiller consists of a single motor with a separate compressor and can be connected to the coupler. The main advantage is the accessibility and serviceable motor independently without upsetting adjacent components. Also, if the motor does fail, there is no risk of contamination to the refrigerant.
The moral of open-type chillers is the potential for refrigerant leaks. To counter this potential, shaft seals have to be fit which creates an assembly complexity. Still, open-type compressors are generally used as a large industrial chiller as they offer the advantage of easier repairs and maintenance.
Hermetic Chillers
Classifying hermetic systems: the motor and compressor are assembled in a sealed welded shell. The refrigerant enters the compressor and also cools the motor.
Hermetic sealing eliminates the nuisance of refrigerant leakage. The downside, of course, is contamination of refrigerant if the motor fails, and therefore, repairs can be more involved. This is why hermetic chillers are usually small to mid-size.
Semi-hermetic Water Chillers
Semi-hermetic water chillers are similar to hermetic water chillers in fundamental ways but the compressor shell is constructed differently. Rather than being weld-assembled the semi-hermetic compressor shell is bolted, and therefore has some limited serviceability.
Engine-driven Water Chillers
Engine-driven water chillers employ gas or diesel engines to turn the compressor, not electric motors. Engine-driven chillers are used more often as stand-by units to improve reliability. If there is a power failure, engine-driven chillers can provide cooling to critical processes and equipment and will continue to operate.
In addition to their independence from the plant’s electricity supply, engine-driven chillers will operate at varying speeds, while electric motors always run at a stable speed. To obtain variable speeds with electric motors utilizes relatively expensive VFD (Variable Frequency Drive) systems.
Pump and Piping
In designing chilled water systems, another important element revolves around the pump and piping system. This piping system typically consists of a pump to circulate the chilled water to various consumers and process equipment.
Therefore, if the pump and piping system do not load characteristics of chilled water, the proper design of the system is paramount in supporting proper water flow rates, and providing adequate cooling capacity for the uses stated above.
The design process generally begins with determining the pump brake horsepower (BHP); the BHP is calculated based on the chilled water flow rate, and total pump head research or estimator.
In regards to the chilled water flow rate, this was previously discussed. The total pump head considers elevation changes as well as the frictional head losses in piping.
The piping material selection is also very relevant. Water, especially in normal operation contains impurities ranging from salts and microorganisms that can cause scaling and fouling as well as accelerate corrosion.
Material selection is paramount in maintaining the reliability of the equipment while controlling costs. The most common materials for piping in distribution piping includes carbon steel, copper, and PVC piping, and stainless steel and copper piping for internal piping for chiller units.
What are industrial water chillers?
Industrial water chillers are important to the manufacturing process because they provide the temperatures needed for production.
Industrial chillers are required in applications where low temperatures must be maintained continuously for long periods to assure appropriate equipment operation.
The dynamic cooling system removes heat to maintain stable temperature, pressure and airflow for the refrigeration system.
Industrial water chillers are circulating a cooling fluid to the equipment that requires cooling to complete the production process. Unlike the small, evolving fan systems, industrial water chillers are required, based on the scale of the cooling application, and the demand for efficiency.
The functionality of industrial water chillers is superior to and more reliable than other options, which is another reason that they are the preferred choice for handling the unique cooling applications and needs of complex production processes.
How Industrial Water Chillers Work
Industrial production techniques produce appreciable amounts of heat from sources including friction, operating processes, heating components, ovens, and heat treatments.
To mitigate injury risk to workers and equipment and for a safe work environment, chillers will effectively take the heat away from industrial chillers.
Unlike HVAC systems, chillers are often used as part of a closed loop of pumps where the cooled fluid is circulated away from the chiller and to many different processes.
Industrial chillers will extract the heat from the process and move the warmed fluid back to the chiller, where the heat is discharged and the fluid is cooled and prepared for cycling again through an industrial chiller.
Parts of an Industrial Chiller
Industrial chillers have the same basic components as smaller chillers, but they are heavier duty and are built to address a larger cooling demand and continuous operation. Industrial chillers, like all chillers, are categorized based on their condensers, either air-cooled or water-cooled chillers.
- Evaporator: In the evaporator of an industrial water chiller, heat causes the refrigerant to boil and will transition it from a liquid to a gas to send it on to the compressor. The key factor of the entire process is the pressure that the vapor is leaving the evaporator at.
- Compressor: The most common type of compressor for industrial chillers is scroll compressors. This works by compressing refrigerant between two spiral plates, with one plate remaining stationary while the other orbits. As the orbiting plate moves, the gas is trapped in a gradually smaller space and forced out through the center outlet of the compressor. Large industrial chillers may have multiple scroll compressors for a single industrial water chiller for redundancy, efficiency, or for handling heavy loads.
- Condenser: The condenser of an industrial chiller operates like a heat exchanger, removing heat from the high pressure and high temperature refrigerant vapor. It does this efficiently enough to make the phase transition from vapor to liquid which makes it possible for the refrigerant to fit into the water chiller cycle.
- Expansion Valve: The liquid refrigerant flows from the condenser to expansion valves where it has its refrigerant pressure lowered before being sprayed into the evaporator. The refrigerant will be cooled from the pressure drop. As the capacity of the evaporator increases the expansion valve will release more refrigerant into the evaporator; as the evaporator capacity decreases the expansion valve will release less refrigerant. The expansion valve also maintains the pressure difference between the high pressure side of the condenser and the low pressure side of the evaporator.
Industrial water chillers are vital to maintaining precise temperature control for industrial operations, and they are affordable engineering solutions.
Industrial water chillers can power dozens (or hundreds) of individual pieces of equipment and are built to plan for growth and scaling with industry.
A stable cooling system is essential for industrial machinery and tools given the friction, stress, and running time of these mechanisms. Industrial chillers are built to withstand harsh conditions.
Industrial chiller designers and manufacturers know what the industrial production process is like, and they develop cooling solutions that can deal with the industry’s tough, rigorous requirements.
How to Choose an Industrial Water Chiller
Selecting an industrial water chiller is still a complicated process that needs thorough thought, despite its many benefits. These large-scale and complex units are often customized based on application-specific needs.
Having a good understanding of the application or applications is key to choosing an appropriate chilled water unit.
Water chillers are designed, engineered, and built by water chiller manufacturers in close cooperation with the end client to meet specific industry and temperature specifications.
In a first phase, a manufacturer’s expert visits a client’s facilities to understand existing working conditions and determine temperature levels suitable for the client’s application. This way the water chiller is specifically tailored to the existing conditions and requirements.
At an initial stage in the selection process, manufacturers want to select the chilling system that effectively addresses both environmental specifications and budget restrictions.
The manufacturer is now in partnership with the client to select an appropriate chiller for the situation. When custom temperature or environmental requirements arise the manufacturer will engineer a unique solution.
Manufacturers of water chillers are also obligated to ensure their equipment meets the rigorously detailed criteria of the Environmental Protection Agency (EPA).
Other Factors Related to Water Chiller Selection
- Cooling Fluid: The selection of a liquid for an industrial water chiller is based on the performance potential of a fluid and compatibility with auxiliary equipment. The actual performance of a fluid will depend on the characteristics of the fluid at a particular temperature (heat, viscosity, freezing point, boiling point, etc.).
- Fluid Temperature: The cooling capacity of a water chiller is defined by its setpoint temperature. The fluid temperature and cooling capcaity of the system operate opposite of each other; cooling efficiently at temperatures near freezing want to take on a larger load while temperatures that are warmer want to take on less of a load.
- Pressure and Flow Requirements: As presented in the discussion of a water chiller, pressure is a significant component of the operation of a system. In order for a system to perform properly and efficiently, the pump must be capable of fulfilling the requirements of the system. The pressure, in combination with the flow rate is equally important in heat transfer.
- Chiller Size: The sizing of a chiller for a process is the responsibility of the chiller manufacture. The chiller manufacturer has all of the data and experience necessary to select the proper chiller for a process, operation, or function.
Conclusion
- A water chiller, also referred to as a chilled water system, is a cooling system where water acts as a secondary refrigerant. These systems are utilized in large, complicated heating, ventilating, air conditioning, and refrigeration (HVACR) applications.
- The main loops or circuits of a water chilled system are the refrigeration loop and the chilled water loop. The refrigeration loop is the cooling subsystem and the chilled water loop is the distribution system (where the cold water is distributed to consumer units).
- Water chillers may be air-cooled or water-cooled, depending on how they dissipate heat to the environment.
- Water chiller compressors can be centrifugal, screw, scroll, or reciprocating. The compressor depends on the load of the system and the required cooling capacity.
- Industrial production processes generate considerable heat through friction, equipment, heating components, ovens, burning, and heat treatments. Industrial chillers remove heat away from equipment, employees, and finished products for worker and equipment protection and safety in the work environment.