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Chill

ers

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 air or equipment

as required.

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In air conditioning systems, chilled water is typically distributed to

heat exchangers, or coils, in air handling units, or other type of

terminal devices which cool the air in its respective space(s), and

then the chilled water is re-circulated back to the chiller to be

cooled again. 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 15 to 1500 tons (180,000 to

18,000,000 BTU/h or 53 to 5,300 kW) in cooling capacity. Chilled

water temperatures can range from 35 to 45 degrees Fahrenheit

(1.5 to 7 degrees Celsius), depending upon application

requirements.

Vapor-Compression chiller technology:Where available, cold water readily available in nearby waterbodies might be used directly for cooling,place or supplementcooling towers. The Deep Lake Water Cooling System inToronto,Canada, is an example. It dispensed with the need for coolingtowers, with a significant cut in carbon emissions and energy

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consumption. It uses cold lake water to cool the chillers, which inturn are used to cool city buildings via a district cooling system.

The return water is used to warm the city's drinking water supplywhich is desirable in this cold climate. Whenever a chiller's heat

rejection can be used for a productive purpose, in addition to thecooling function, very high thermal effectiveness is possible.

There are basically four different types of compressors used invapor compression chillers: Reciprocating compression, scrollcompression, screw-driven compression, and centrifugalcompression are all mechanical machines that can be powered byelectric motors, steam, or gas turbines. They produce theircooling effect via the "reverse-Rankine" cycle, also known as'vapor-compression'. With evaporative cooling heat rejection,

their coefficients-of-performance (COPs) are very high; typically4.0 or more.

In recent years, application of Variable Speed Drive (VSD)technology has increased efficiencies of vapor compressionchillers. The first VSD was applied to centrifugal compressorchillers in the late 1970s and has become the norm as the cost ofenergy has increased. Now, VSDs are being applied to rotaryscrew and scroll technology compressors.

Adsorption technology:

Adsorption chillers are driven by hot water. This hot water maycome from any number of industrial sources including waste heatfrom industrial processes, prime heat from solar thermalinstallations or from the exhaust or water jacket heat of a pistonengine or turbine.

The principle of adsorption is based on the interaction of gasesand solids. With adsorption chilling, the molecular interactionbetween the solid and the gas allows the gas to be adsorbed into

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the solid. The adsorption chamber of the chiller is filled with solidmaterial, silica gel, eliminating the need for moving parts andeliminating the noise associated with those moving parts. Thesilica gel creates an extremely low humidity condition that causes

the water refrigerant to evaporate at a low temperature. As thewater evaporates in the evaporator, it cools the chilled water.

The use of silica gel desiccant keeps the maintenance costs andoperating costs of adsorption chillers low.

Absorption technology:

Absorption chillers' thermodynamic cycle are driven by heatsource; this heat is usually delivered to the chiller via steam, hotwater, or combustion. Compared to electrically powered chillers,they have very low electrical power requirements - very rarelyabove 15 kW combined consumption for both the solution pumpand the refrigerant pump. However, their heat input requirementsare large, and their COPs are often 0.5 (single-effect) to 1.0

(double-effect). For the same tonnage capacity, they requiremuch larger cooling towers than vapor-compression chillers.However, absorption chillers, from an energy-efficiency point-of-view, excel where cheap, high grade heat or waste heat is readilyavailable. In extremely sunny climates, solar energy has beenused to operate absorption chillers.

The single effect of water-cooled machines and instruments. Thewater flows from the chiller to the application's point of use andback.

If the water temperature differe in the tank.

One of the newer developments in industrial water chillers is theuse of water cooling instead of air cooling. In this case thecondenser does not cool the hot refrigerant with ambient air, butuses water cooled by a cooling tower. This development allows a

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reduction in energy requirements by more than 15% and alsoallows a significant reduction in the size of the chiller due to thesmall surface area of the water based condenser and the absenceof 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 flowingover coils containing the coolant to regulate temperature. Wateris the most commonly used coolant within process chillers,although coolant mixtures (mostly water with a coolant additiveto enhance heat dissipation) are frequently employed.

Chillers in industry:

In industrial application, chilled water or other liquid from thechiller 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 industry in injection and blowmolding, 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, powersupplies and power generation stations, analytical equipment,semiconductors, compressed air and gas cooling. They are alsoused to cool high-heat specialized items such as MRI machinesand lasers, and in hospitals, hotels and campuses. The chillers forindustrial applications can be centralized, where each chillerserves multiple cooling needs, or decentralized where eachapplication or machine has its own chiller. Each approach has itsadvantages. It is also possible to have a combination of bothcentralized 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 (cooling capacity),usually from 0.2 tons to 10 tons. Centralized chillers generally

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have capacities ranging from ten tons to hundreds or thousandsof tons.

Chilled water is used to cool and dehumidify air in mid- to large-size commercial, industrial, and institutional (CII) facilities. Waterchillers can be water-cooled, air-cooled, or evaporatively cooled.Water-cooled chillers incorporate the use ofcooling towers whichimprove the chillers' thermodynamic effectiveness as comparedto air-cooled chillers. This is due to heat rejection at or near theair's wet-bulb temperature rather than the higher, sometimesmuch higher, dry-bulb temperature. Evaporatively cooled chillersoffer higher efficiencies than air-cooled chillers but lower thanwater-cooled chillers.

Water-cooled chillers are typically intended for indoor installationand operation, and are cooled by a separate condenser waterloop and connected to outdoor cooling towers to expel heat to theatmosphere.

Air-cooled and Evaporatively cooled chillers are intended foroutdoor installation and operation. Air-cooled machines aredirectly cooled by ambient air being mechanically circulateddirectly through the machine's condenser coil to expel heat to theatmosphere. Evaporatively cooled machines are similar, exceptthey implement a mist of water over the condenser coil to aid incondenser cooling, making the machine more efficient than atraditional air-cooled machine. No remote cooling tower istypically required with either of these types of packaged air-cooled or evaporatively cooled chillers.

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Types of chillers:

1.Absorption Liquid Chillers

Absorption chillers use heat to drive the refrigeration cycle, they

produce chilled water while consuming just a small amount of

electricity to run the pumps on the unit. Absorption chillers

generally use steam or hot water to drive the lithium bromide

refrigeration cycle but can also use other heat sources.

2.Centrifugal Liquid Chillers

Bringing a chiller back online rapidly after a loss of power iscritical to operations in mission critical environments like datacenters and hospitals which demand the highest levels ofreliability.

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centrifugal chillers have a long pedigree. For over 60 years,these products have embodied the global standard ofreliability, efficiency and durability. This product continues to

be the choice of thousands of engineers and ownersworldwide because its reliability and energy efficiency offerslower operating cost over the life of a variety of differenttypes of buildings and applications, from comfort to processcooling. The hermetic design prevents contaminants fromaffecting the longevity of the machine and virtually eliminatesthe risk of releasing refrigerants into the environment duringnormal operations.

centrifugal chillers are among the quietest in the industry.

And can keep the chiller operating when others would shutdownoften just when you need cooling the most. All of ourcentrifugal chillers feature multiple stages for a largeoperating envelope and surge resistance, and a flasheconomizer to save energy.

Industrial chiller selection:

Important specifications to consider when searching for industrialchillers include the total life cycle cost, the power source, chillerIP rating, chiller cooling capacity, evaporator capacity, evaporatormaterial, evaporator type, condenser material, condensercapacity, ambient temperature, motor fan type, noise level,internal piping materials, number of compressors, type ofcompressor, number of fridge circuits, coolant requirements, fluid

discharge temperature, and COP (the ratio between the coolingcapacity in RT to the energy consumed by the whole chiller in KW).For medium to large chillers this should range from 3.5-7.0 withhigher values meaning higher efficiency. Chiller efficiency is oftenspecified in kilowatts per refrigeration ton (kW/RT).

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Process pump specifications that are important to considerinclude 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 5C, then a special pumpneeds to be used to be able to pump the high concentrations ofethylene glycol. Other important specifications include theinternal water tank size and materials and full load current.

Control panel features that should be considered when selectingbetween industrial chillers include the local control panel, remotecontrol panel, fault indicators, temperature indicators, andpressure indicators.

Additional features include emergency alarms, hot gas bypass,city water switchover, and casters.

3-A hermetic unit

uses a hermetic compressor with the electric motor totally enclosed in the

refrigerant atmosphere. The possibility of refrigerant leakage to the outside

through a shaft seal is totally eliminated, and motor operating noise is subdued by

the housing. Because this type of forced refrigerant cooling of the motor is very

effective, smaller, less expensive motors can be used. The need for a heavyexternal base to preserve motor-compressor shaft alignment is eliminated.

Hermetic machines are less expensive than external drive machines, have slightly

greater power consumption, and are quieter. However, should the motor fail, the

repair cost is higher, and the unit must be replaced with a like unit or sent back to

the manufacturer for service. These compressors are used in most cases for a small

refrigeration or air-conditioning system.

4-Open direct drive type

compressors are those in which the crankshaft, which is fitted with a shaft seal,

extends from the housing. They do not have a drive motor as an integral part, but

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the drive motor in most cases is placed on the same base with the compressor. The

motor may be joined to the compressor with a direct drive coupling or belt drive.

The next figure show the Complete-Air-Conditioning

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Conculision

A chilled water system is a means by which heat, generated in a

space or by a process,

is conveyed from that space and ultimately released to the outside.

to maintain a chilled water system for continuous day-to-day

operation. Each chilled water system is designed to transfer heat by

the most efficient and cost-effective method.

While there is no right way to design a chilled water system, chilled

water systems have common characteristics and use common types

of components. Due to these differences in chilled water systems, the

individual chilled water system equipment manufacturer's

directions regarding maintenance practices take precedence over

any guidance