Chillers

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.  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.

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.

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.

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.

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Description

A chiller is a machine that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle.  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.

Chilled water is used to cool and dehumidify air in mid- to large-size commercial, industrial, and institutional facilities.  Water chillers can be water-cooled, air-cooled, or evaporatively cooled.  Water-cooled systems can provide efficiency and environmental impact advantages over air-cooled systems.

In industrial application, chilled water or other 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, metal working 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 power generation stations, analytical equipment, semiconductors, compressed air and gas cooling.  They are also used to cool high-heat specialized items such as MRI machines and lasers, and 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.

Decentralized chillers are usually small in size and cooling capacity, usually from 0.2 to 10 short tons (0.179 to 8.929 long tons; 0.181 to 9.072 t).  Centralized chillers generally have capacities ranging from ten tons to hundreds or thousands of tons.

Chilled water is used to cool and dehumidify air in mid- to large-size commercial, industrial, and institutional (CII) facilities.  Water chillers can be water-cooled, air-cooled, or evaporatively cooled.  Water-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 water-cooled chillers.

Water-cooled chiller is 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 chiller is 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.

 

 

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