Nov. 27, 2024
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A chiller is a machine that removes heat from a liquid coolant via a vapor-compression, adsorption refrigeration, or absorption refrigeration cycles. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream (such as air or process water). As a necessary by-product, refrigeration creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes.[1] Vapor compression chillers may use any of a number of different types of compressors. Most common today are the hermetic scroll, semi-hermetic screw, or centrifugal compressors. The condensing side of the chiller can be either air or water cooled. Even when liquid cooled, the chiller is often cooled by an induced or forced draft cooling tower. Absorption and adsorption chillers require a heat source to function.[2][3]
Chilled water is used to cool and dehumidify air in mid- to large-size commercial, industrial, and institutional facilities. Water cooled chillers can be liquid-cooled (through cooling towers), air-cooled, or evaporatively cooled. Water or liquid-cooled systems can provide efficiency and environmental impact advantages over air-cooled systems.[4]
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A liquid (glycol based) chiller with an air cooled condenser on the rooftop of a medium size commercial buildingIn air conditioning systems, chilled coolant, usually chilled water mixed with ethylene glycol, from a chiller in an air conditioning or cooling plant is typically distributed to heat exchangers, or coils, in air handlers or other types of terminal devices which cool the air in their respective space(s). The water is then recirculated to the chiller to be recooled. These cooling coils transfer sensible heat and latent heat from the air to the chilled water, thus cooling and usually dehumidifying the air stream. A typical chiller for air conditioning applications is rated between 50 kW (170 thousand BTU/h) and 7 MW (24 million BTU/h), and at least two manufacturers (York international and LG) can produce chillers capable of up to 21 MW (72 million BTU/h) cooling.[5][6] Chilled water temperatures (leaving from the chiller) usually range from 1 to 7 °C (34 to 45 °F), depending upon application requirements. Commonly, chillers receive water at 12°C (entering temperature), and cool it to 7°C (leaving temperature).[7]
When the chillers for air conditioning systems are not operable or they are in need of repair or replacement, emergency chillers may be used to supply chilled water. Rental chillers are mounted on a trailer so that they can be quickly deployed to the site. Large chilled water hoses are used to connect between rental chillers and air conditioning systems.[8]
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In industrial applications, chilled water or other coolant liquid from the chiller is pumped through process or laboratory equipment. Industrial chillers are used for controlled cooling of products, mechanisms and factory machinery in a wide range of industries. They are often used in the plastic industries, injection and blow molding, metalworking cutting oils, welding equipment, die-casting and machine tooling, chemical processing, pharmaceutical formulation, food and beverage processing, paper and cement processing, vacuum systems, X-ray diffraction, power supplies and gas turbine power generation stations (see Turbine inlet air cooling#Vapour compression chiller), analytical equipment, semiconductors, compressed air and gas cooling. They are also used to cool high-heat specialized items such as MRI machines and lasers in hospitals, hotels, and campuses.
Chillers for industrial applications can be centralized, where a single chiller serves multiple cooling needs, or decentralized where each application or machine has its own chiller. Each approach has its advantages. It is also possible to have a combination of both centralized and decentralized chillers, especially if the cooling requirements are the same for some applications or points of use, but not all.
Chilled water is used to cool and dehumidify air in mid- to large-size commercial, industrial, and institutional (CII) facilities. Liquid chillers can be liquid-cooled, air-cooled, or evaporatively cooled. Water or liquid-cooled chillers incorporate the use of cooling towers which improve the chillers' thermodynamic effectiveness as compared to air-cooled chillers. This is due to heat rejection at or near the air's wet-bulb temperature rather than the higher, sometimes much higher, dry-bulb temperature. Evaporatively cooled chillers offer higher efficiencies than air-cooled chillers but lower than liquid-cooled chillers.
Liquid-cooled chillers are typically intended for indoor installation and operation and are cooled by a separate condenser water loop and connected to outdoor cooling towers to expel heat to the atmosphere.
Air-cooled and evaporative cooled chillers are intended for outdoor installation and operation. Air-cooled machines are directly cooled by ambient air being mechanically circulated directly through the machine's condenser coil to expel heat to the atmosphere. Evaporative cooled machines are similar, except they implement a mist of water over the condenser coil to aid in condenser cooling, making the machine more efficient than a traditional air-cooled machine. No remote cooling tower is typically required with either of these types of packaged air-cooled or evaporatively cooled chillers.
Where available, cold water readily available in nearby water bodies might be used directly for cooling, replacing or supplementing cooling towers. The deep water source cooling system in Toronto, Ontario, Canada, is an example. It uses cold lake water to cool the chillers, which in turn are used to cool city buildings via a district cooling system. The return water is used to warm the city's drinking water supply, which is desirable in this cold climate. Whenever a chiller's heat rejection can be used for a productive purpose, in addition to the cooling function, very high thermal effectiveness is possible.
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A vapor compression chiller typically uses one of four types of compressor: Reciprocating compression, scroll compression, screw-driven compression, and centrifugal compression are all mechanical machines that can be powered by electric motors, steam, or gas turbines. Using electric motors in a semi-hermetic or hermetic configuration is the most common method of driving the compressors since electric motors can be effectively and easily cooled by the refrigerant, without requiring fuel supply or exhaust ventilation and no shaft seals are required as the motor can operate in the refrigerant, reducing maintenance, leaks, operating costs and downtime, although open compressors are sometimes used. They produce their cooling effect via the reverse-Rankine cycle, also known as vapor-compression. With evaporative cooling heat rejection, their coefficients of performance (COPs) are very high; typically 4.0 or more.
= Cooling power Input power {\displaystyle ={\frac {\text{Cooling power}}{\text{Input power}}}}
Current vapor-compression chiller technology is based on the "reverse-Rankine" cycle known as vapor-compression. See the attached diagram which outlines the key components of the chiller system.
Diagram showing the components of a liquid-cooled chiller A view into the exposed shell and tube heat exchanger on a centrifugal chiller. Refrigerant in its gaseous state passes through tubes (visible at the back) which exchange heat with water circulating within the shell.Key components of the chiller:
Refrigeration compressors are essentially a pump for refrigerant gas. The capacity of the compressor, and hence the chiller cooling capacity, is measured in kilowatts input (kW), Horse power input (HP), or volumetric flow (m3/h, ft3/h). The mechanism for compressing refrigerant gas differs between compressors, and each has its own application. Common refrigeration compressors include reciprocating, scroll, screw, or centrifugal. These can be powered by electric motors, steam turbines, or gas turbines. Compressors can have an integrated motor from a specific manufacturer, or be open drive--allowing the connection to another type of mechanical connection. Compressors can also be either hermetic (welded closed) or semi-hermetic (bolted together).
In recent years, application of variable-speed drive (VSD) technology has increased efficiencies of vapor compression chillers. The first VSD was applied to centrifugal compressor chillers in the late s and has become the norm as the cost of energy has increased. Now, VSDs are being applied to rotary screw and scroll-technology compressors.
Condensers can be air-cooled, liquid-cooled, or evaporative. The condenser is a heat exchanger which allows heat to migrate from the refrigerant gas to either water or air. Air cooled condenser are manufactured from copper tubes (for the refrigerant flow) and aluminium fins (for the air flow). Each condenser has a different material cost and they vary in terms of efficiency. With evaporative cooling condensers, their coefficients-of-performance (COPs) are very high; typically 4.0 or more. Air cooled condensers are installed and operated outdoors and are cooled with outside air, that is often forced through the condenser using electric fans. Water or liquid cooled condensers are cooled with water that is often in turn cooled by a cooling tower.
The expansion device (TEV) or refrigerant metering device (RMD) restricts the flow of the liquid refrigerant causing a pressure drop that vaporizes some of the refrigerant; this vaporization absorbs heat from nearby liquid refrigerant. The RMD is located immediately prior to the evaporator so that the cold gas in the evaporator can absorb heat from the water in the evaporator. There is a sensor for the RMD on the evaporator outlet side which allows the RMD to regulate the refrigerant flow based on the chiller design requirement.
Evaporators can be plate type or shell and tube type. The evaporator is a heat exchanger which allows the heat energy to migrate from the water stream into the refrigerant gas. During the state change of the remaining liquid to gas, the refrigerant can absorb large amounts of heat without changing temperature.
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The thermodynamic cycle of an absorption chiller is driven by a heat source; this heat is usually delivered to the chiller via steam, hot water, or combustion. Compared to electrically powered chillers, an absorption chiller has very low electrical power requirements ' very rarely above 15 kW combined consumption for both the solution pump and the refrigerant pump. However, its heat input requirements are large, and its COP is often 0.5 (single-effect) to 1.0 (double-effect). For the same cooling capacity, an absorption chiller requires a much larger cooling tower than a vapor-compression chiller. However, absorption chillers, from an energy-efficiency point of view, excel where cheap, low-grade heat or waste heat is readily available.[9] In extremely sunny climates, solar energy has been used to operate absorption chillers.
The single-effect absorption cycle uses water as the refrigerant and lithium bromide as the absorbent. It is the strong affinity that these two substances have for one another that makes the cycle work. The entire process occurs in almost a complete vacuum.
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Industrial chillers typically come as complete, packaged, closed-loop systems, including the chiller unit, condenser, and pump station with recirculating pump, expansion valve, no-flow shutdown, internal cold water control. Compressors can be of two types - scroll and screw depending on the budget and the performance expected from a chiller. The internal tank helps maintain cold water temperature and prevents temperature spikes from occurring. Closed-loop industrial chillers recirculate a clean coolant or clean water with condition additives at a constant temperature and pressure to increase the stability and reproducibility of water-cooled machines and instruments. The water flows from the chiller to the application's point of use and back.[citation needed]
If the water temperature differentials between inlet and outlet are high, then a large external water tank would be used to store the cold water. In this case the chilled water is not going directly from the chiller to the application, but goes to the external water tank which acts as a sort of "temperature buffer." The cold water tank is much larger than the internal water goes from the external tank to the application and the return hot water from the application goes back to the external tank, not to the chiller.[citation needed]
The less common open loop industrial chillers control the temperature of a liquid in an open tank or sump by constantly recirculating it. The liquid is drawn from the tank, pumped through the chiller and back to the tank. In industrial water chillers is the use of water cooling instead of air cooling. In this case the condenser does not cool the hot refrigerant with ambient air, but uses water that is cooled by a cooling tower. This development allows a reduction in energy requirements by more than 15% and also allows a significant reduction in the size of the chiller, due to the small surface area of the water-based condenser and the absence of fans. Additionally, the absence of fans allows for significantly reduced noise levels.[citation needed]
Most industrial chillers use refrigeration as the media for cooling, but some rely on simpler techniques such as air or water flowing over coils containing the coolant to regulate temperature. Water is the most commonly used coolant within process chillers, although coolant mixtures (mostly water with a coolant additive to enhance heat dissipation) are frequently employed.[11]
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Important specifications to consider when searching for industrial chillers include the total life cycle cost, the power source, chiller IP rating, chiller cooling capacity, evaporator capacity, evaporator material, evaporator type, condenser material, condenser capacity, ambient temperature, motor fan type, noise level, internal piping materials, number of compressors, type of compressor, number of fridge circuits, coolant requirements, fluid discharge temperature, and COP (the ratio between the cooling capacity in RT to the energy consumed by the whole chiller in kW). For medium to large chillers this should range from 3.5 to 7.0, with higher values meaning higher efficiency. In the US, chiller efficiency is often specified in kilowatts per refrigeration ton (kW/RT).
Process pump specifications that are important to consider include the process flow, process pressure, pump material, elastomer and mechanical shaft seal material, motor voltage, motor electrical class, motor IP rating and pump rating. If the cold water temperature is lower than '5 °C, then a special pump needs to be used to be able to pump the high concentrations of ethylene glycol. Other important specifications include the internal water tank size and materials and full load current.
Control panel features that should be considered when selecting between industrial chillers include the local control panel, remote control panel, fault indicators, temperature indicators, and pressure indicators.
Additional features include emergency alarms, hot gas bypass, city water switchover, and casters.[10]
Demountable chillers are also an option for deployment in remote areas and where the conditions may be hot and dusty.[12]
If noise levels of the chiller are acoustically unacceptable, noise control engineers will implement sound attenuators to reduce chiller noise levels. Larger chillers will typically require an array of sound attenuators sometimes known as a silencer bank.
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A vapor-compression chiller uses a refrigerant internally as its working fluid. Many refrigerants options are available; when selecting a chiller, the application cooling temperature requirements and refrigerant's cooling characteristics need to be matched. Important parameters to consider are the operating temperatures and pressures.
There are several environmental factors that concern refrigerants, and also affect the future availability for chiller applications. This is a key consideration in intermittent applications where a large chiller may last for 25 years or more. Ozone depletion potential (ODP) and global warming potential (GWP) of the refrigerant need to be considered. ODP and GWP data for some of the more common vapor-compression refrigerants (noting that many of these refrigerants are highly flammable and/or toxic):[13]
Refrigerant ODP GWP R12 1 R123 0.012 76 R134a 0 R22 0.05 R290 (propane) 0 3 R401a 0.027 970 R404a 0 R407a 0 R407c 0 R408a 0.016 R409a 0.039 R410a 0 R500 0.7 ??? R502 0.18 R507 0 R600a 0 3 R744 (CO2)[
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0 1 R717 (ammonia) 0 0 R718 (water)[
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0 0R12 is the ODP reference. CO2 is the GWP reference
The refrigerants used in the chillers sold in Europe are mainly R410a (70%), R407c (20%) and R134a (10%).[16]
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If your facility uses process fluids or heavy-duty machinery that generates heat, you'll need an industrial chiller system to cool your processes and internal machine components. Understanding how an industrial chiller works and the various types of chillers available will help you make the right choice for your cooling needs.
An industrial chiller is a refrigeration system used to lower the temperature of machinery, industrial spaces, and process fluids by removing heat from the system and transferring it elsewhere. Industrial chillers are essential for temperature regulation in several industrial processes, such as injection molding, metal plating, oilfield production, and food processing.
Industrial chiller systems are beneficial for applications where strict operational temperatures are required. When integrated with heat-sensitive processes, chillers will prevent thermal damage to process equipment and ensure no alterations to the final products from exposure to unsuitable temperatures.
Industrial chillers work based on the following principles of operation.
An industrial chiller system is driven by one of two operational principles:
Heat absorption chillers integrate heat exchangers that pull heat away from any associated processes and dissipate them exteriorly. Heat exchangers are typically composed of piping containing coolant fluids (air, water, or a mixture of water and other liquids).
Vapor compression chillers achieve a cooling effect by circulating coolant in pipes through the processes requiring cooling. This will pull heat from any associated processes into the coolant, which is then circulated to a refrigerant system that cools the chiller fluid and prepares it for a new cycle of process cooling.
Chillers consist of four essential components; an evaporator, a compressor, a condenser, and an expansion unit. In addition, every chiller system contains a refrigerant.
The process starts with a low-pressure refrigerant entering the evaporator. Inside the evaporator, the chiller refrigerant is heated, causing it to undergo a phase change into a gas. Next, the gaseous refrigerant goes into the compressor, which increases its pressure.
The high-pressure refrigerant goes to the condenser, which rejects the heat using cooling water from a cooling tower or air from the surroundings, condensing it into a high-pressure liquid. The condensed refrigerant then goes to the expansion unit, which has a valve that acts as a metering device to limit refrigerant flow. Learn about new chiller refrigerants.
Consequently, this lowers the pressure of the refrigerant and begins the cooling process again. The entire process is known as the refrigeration cycle.
The central chiller components include the following:
The function of a chiller condenser unit is to eliminate heat from the refrigerant being circulated through the chiller unit. This is achieved by circulating water between a cooling tower and the condenser for water-cooled variants or blowing cool air over condenser piping for air-cooled chiller units.
The compressor is the driving unit of any chiller system. It generates the pressure gradient necessary to push refrigerant around the chiller unit to achieve process cooling. Various condensers are available, with the most popular types including centrifugal, screw, and reciprocating compressors.
An evaporator is placed between the expansion valve, and the condenser removes heat from any associated process into circulating refrigerant. This is then channeled to a cooling tower or air-cooled depending on the chiller configuration.
Thermal expansion valves located between the compressor and the evaporator serve to expand refrigerant passing through them. This action diminishes the pressure and improves the heat elimination from the evaporator.
Every chiller incorporates a power unit that controls electrical energy flowing through the system. Power unit components usually include starters, power monitoring panels, and circuit breakers.
Control panels serve to regulate the entire process of cooling operation. They usually integrate sensors, alarms, and display screens that allow operators to adjust system settings for optimal thermal control.
These devices may be mounted on either the chiller system evaporator or its water-cooled condenser. Their purpose is to conduct water flow effectively.
The three main types of chillers in use today are air-cooled chillers, water-cooled chillers, and absorption chillers. We will also briefly touch on cooling towers (an alternative or supplemental cooling system) and special chillers like glycol and centrifugal.
Selecting the right chiller for your application will help you to save costs, reduce downtime, and improve operational efficiency.
Water-cooled chillers use water from an external cooling tower to reject heat from a gaseous refrigerant in the condenser before it undergoes a phase change into a liquid.
In place of the cooling water, air-cooled chillers use ambient air to reject heat from the refrigerant in the condenser. Learn more about air-cooled vs. water-cooled chillers.
This type of chiller uses refrigerants to cool process fluids and spaces. A compressor is used as the driving force to pump refrigerant around the system.
Vapor absorption chillers have no compressor in the unit. Instead, they use a heat source, e.g. solar energy or waste heat to drive the coolant through the system.
The process starts with liquid coolant in an evaporator which turns it into gaseous form. Next, the gaseous coolant is absorbed by a concentrated absorbent such as Lithium Bromide or Ammonia, provided by a generator. Finally, the diluted solution absorbs the coolant while the heat is absorbed by the cooling water.
The diluted solution of coolant and absorbent flows through a heat exchanger to the generator, where it is heated. The coolant vaporizes out of the solution, condenses, and is sent out for cooling again. The now-concentrated absorbent is recycled as well.
Glycol chillers are special types that use propylene glycol, an anti-freeze, in the system. They are widely used in food-grade applications such as in the production of alcohol and for brewery chilling systems.
The mode of operation of glycol chillers is the same as a standard chiller.
Centrifugal chillers consist of the usual evaporator, compressor, condenser, and expansion device set-up but with additional rotating impellers which compress the refrigerant and transport it around the system. They are beneficial for medium to large-scale cooling operations (from 150 ' tons of refrigeration).
Industrial chiller systems can be used for cooling operations in diverse industries. Below are some of the most common applications:
An adequately sized chiller is critical for efficient and cost-effective processes, machinery, and space cooling. Cold Shot Chillers' easy-to-use sizing tool can help you quickly determine your optimal chiller capacity, tonnage, and size.
The cost of installing and operating chiller systems can be pretty high. Chiller units must be run as efficiently as possible to avoid additional charges during routine operation. Scheduling and conducting regular maintenance for your system will prevent costly chiller repairs in the long term. Applicable chiller maintenance should include condenser coil inspection and cleaning, condenser water, and refrigerant maintenance. Real-time monitoring apps like Cold Shot Guardian® can be used to monitor equipment, predict system failures and suggest pre-emptive interventions.
With over three decades of expertise in manufacturing industrial chiller systems, Cold Shot Chillers provides cooling equipment and expertise for the most challenging process cooling needs.
Contact us online or call us at 1.800.473. for more information about our commercial chillers and chiller parts.
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