Absorber - In an absorption
cycle, the vessel in which a lithium bromide solution absorbs
low-pressure refrigerant eater vapor produced in the evaporator.
Absorption Cycle - Absorption
chillers differ from mechanical vapor compression chillers in
that they utilize a thermal or chemical process
to produce the refrigeration effect necessary to provide chilled
water. There is no mechanical compression of the refrigerant taking
place within the machine as occurs within more traditional vapor
compression type chillers. Most commercial absorption chillers
utilize lithium bromide (a salt) and water as the fluid pair;
lithium bromide being the absorbent, water being the refrigerant.
In order to produce the refrigeration effect necessary to make,
for example, 44F chilled water, the shellside of the machine must
be maintained in a deep vacuum to allow the refrigerant (water)
to boil at approximately 40F. The lithium bromide solution absorbs
the vaporized refrigerant, diluting it before it is pumped to
the generator section of the machine where heat is added
to reconcentrate the dilute solution. The water vapor boiled off
in the generator is then condensed, returning to the evaporator
as liquid. The reconcentrated lithium bromide returns to the absorber
section as strong solution to begin the cycle again.
Accumeter - The metering
(flow control) device inside an Evergreen Centrifugal Chiller.
It's unique design always feeds the cooler with liquid refrigerant,
which has a much greater cooling capability than a gaseous refrigerant.
Carrier patented design.
AEL - Allowable Exposure
Limit
AFBMA - Anti-Friction
Bearing Manufacturers Association.
ANSI - American National
Standards Institute
ARI - Air Conditioning
and Refrigeration Institute
ARI 550 - Air Conditioning
and Refrigeration Institute Standard 550-1992: Standard for Centrifugal
and rotary screw water-chilling packages. The purpose of the
standard is to establish , for centrifugal chillers and rotary
screw water-chilling packages: definitions and nomenclature; a
description of what constitutes such a package; published rating
conditions; standard requirements for testing and a basis for
published ratings; and proper refrigerant designations in systems.
ASHRAE - American Society
of Heating Refrigeration and Air Conditioning Engineers
ASME Construction - Strict
design, manufacture, and testing standards set forth by the American
Society of Mechanical Engineers. It involves independent inspection
of every Evergreen chiller built.
Bolt-Together Construction
- Allows a chiller to be taken apart into modules and brought
into buildings through standard doorways.
Burner - In an absorption
cycle, the lithium bromide solution is reconcentrated for the
next cycle in low- and high-stage generators through boiling off
of water. The burner supplies the heat necessary for this process.
Capacity - The measure
of the amount of heat removed by a chiller, measured in tons of
refrigeration (English units) or kilowatts of refrigeration (SI
Metric units).
CCN - Carrier Comfort
Network. A complete system for the management of HVAC building
operations. CCN includes operator interfaces (ComfortWORKS and
Building Supervisor), product controls (Product Integrated Controls
[PICs]), system managers (Chillervisor, Digital Air Volume, and
Flotronic System Manager), and controls for other HVAC and non-HVAC
building components (Comfort Controllers).
Centrifugal Compressor
- A type of compressor used in vapor compression refrigeration
cycles where a rotating impeller is the device which compresses
the refrigerant vapor. The vapor is drawn into the impeller axially,
and is discharged radially after energy is added to the vapor
within the impeller.
Chlorine-Free Refrigerant
- A refrigerant containing no chlorine. The presence of chlorine
in refrigerant compounds contributes to the depletion of ozone
in the atmosphere.
Compressor - In a vapor
compression cycle, the device that increases the pressure and
temperature of refrigerant vapor. It continuously draws low pressure
refrigerant vapor from the cooler, adds energy to increase the
refrigerant pressure and temperature, and discharges the high
pressure vapor to the condenser.
Condenser - A device for
removing heat from a refrigeration system. This heat exchanger
typically consists of a hollow steel shell with copper tubes running
through it. Relatively cool water is pumped through the tubes,
which is cold enough to condense the refrigerant vapor inside
the shell, changing its state to a liquid.
Cooler - A device for
absorbing unwanted heat into a refrigeration system. This heat
exchanger typically consists of a hollow steel shell with copper
tubes running through it. The fluid being chilled (relatively
warm water) is pumped through the tubes. Heat is transferred from
the chilled fluid to the refrigerant liquid inside the shell,
boiling it and changing its state to a vapor.
COP - Coefficient of performance.
This is a measure of the energy efficiency of a chiller.
CSA - Canadian Standards
Association
Demand Limiting - Limits
the power draw of the chiller during peak loading conditions.
Diffuser - Part of a centrifugal
compressor that transforms the high velocity, low pressure gas
exiting the impeller into higher pressure, low velocity gas discharged
into the condenser.
Dynaglide Transmission
- Transmission design on the Carrier Evergreen Chillers. It features
AGMA class 11 gears, tilting pad thrust bearing, and single piece
design, which assures alignment, even after disassembly. Carrier
patented design.
Economizer - In a chiller
with a two-stage centrifugal compressor, the discharge from the
first stage impeller and the inlet to the second stage impeller
are at a pressure level approximately half way between the cooler
pressure and condenser pressure. With this arrangement, an economizer
may be used. This is a shell within which refrigerant liquid from
the condenser drops down to the interstage pressure, flashing
off some of the refrigerant which is drawn directly into the second
stage impeller. This reduces the amount of refrigerant which has
to be compressed by the first stage impeller, improving the refrigeration
cycle efficiency. A similar arrangement may be used with a screw
compressor when the compressor is equipped with an intermediate
inlet port.
Evaporator - See Cooler.
FLASC - Flash SubCooler.
This is a section of some Carrier condensers in which the pressure
of condensed refrigerant liquid is reduced, which causes some
of the liquid to flash into vapor, cooling the remaining liquid.
The vapor is then re-condensed at the lower pressure, which improves
the energy efficiency of the chiller.
Generator - In an absorption
cycle, the vessel in which the lithium bromide solution is reconcentrated
by boiling off the previously absorbed water.
HCFC-22 -
HFC-134a - A positive
pressure, chlorine-free refrigerant having zero ozone depletion
potential. HFC-134a is the refrigerant of choice for automotive
and appliance applications, which will assure a plentiful supply
at reasonable prices.
Heat Exchangers - The
parts of a chiller which exchange heat between two physically
separated fluids. In a chiller, the heat exchangers are the cooler
and the condenser, which exchange heat between the refrigerant
and water or brine. Typically the heat exchangers used in chillers
are of shell-and-tube design, where the water or brine flows through
a number of tubes inside a containment shell, and the refrigerant
is either boiled or condensed on the outside of the tubes.
Hermetic Motor - A motor
which is sealed within the refrigerant atmosphere inside a chiller,
and which is therefore isolated from the atmosphere outside the
chiller. A hermetic motor is efficiently cooled by liquid refrigerant
sprayed directly on the motor windings, and is smaller and lighter
than a comparable air-cooled motor. A compressor driven by a hermetic
motor has the advantage that the compressor shaft does not have
to pass through a seal between the outside atmosphere and the
refrigerant atmosphere inside the chiller.
High-Stage Generator -
In an absorption cycle, the vessel that performs the first stage
of reconcentration of the lithium bromide solution by boiling
off the water contained in the solution. The hot water vapor
boiled off within the high-stage generator is used as the heat
source for the low-stage generator.
Hot Gas Bypass - A system
where some high pressure refrigerant vapor at compressor discharge
conditions is returned directly to the cooler pressure, without
being condensed. This system is sometimes used to permit a chiller
to operate at a lower capacity than would otherwise be possible.
The efficiency at the low load suffers because the bypassed gas,
which does no useful work, still has to be compressed by the compressor.
Impeller - Rotating part
of a centrifugal compressor which increases the pressure of refrigerant
vapor from the cooler pressure to the condenser pressure.
Inlet Guide Vanes - Movable
blades at the inlet of a centrifugal compressor which are used
to control the capacity of the compressor. The guide vanes also
provide rotation to the refrigerant vapor entering the compressor,
which improves the efficiency of the compressor.
ISO 900 Series -
Isolation Valves - Valves
used for the transfer and isolation of refrigerant charge in the
cooler or condenser, allowing refrigerant to be stored inside
a chiller during servicing.
Kingsbury-Type Thrust Bearing
- Self-leveling type of thrust bearing which equalizes bearing
loading over the entire circumference of the bearing, and providing
an optimum oil film shape. This design reduces bearing wear and
provides high reliability and long bearing life.
LCD - Liquid Crystal Display
Lead/Lag - A control system
process that automatically starts and stops a lag or second chiller
in a two chiller water system.
LID - Mounted in the control
center, this allows the operator to interface with the PSIO or
other CCN devices.
Lift - In a vapor compression
cycle, the lift on the compressor is the difference between the
high side (condenser) conditions and the low side (cooler) conditions,
measured as either a temperature or pressure difference.
Low-Stage Generator -
In an absorption cycle, the vessel that performs the second stage
of reconcentration of the lithium bromide solution. The heat
source for the low-stage generator is the steam created in the
high-stage generator.
Lubrication System - System
in a chiller, consisting of an oil pump, oil cooler, and associated
tubing and oil passages, which provides the oil needed to lubricate
the compressor bearings.
Marine Waterbox - A type
of waterbox in which the nozzles are oriented at right angles
to the axis of the heat exchanger shell, and are connected into
the sides of the waterboxes, rather than into the covers. This
allows the covers to be removed, for inspection or cleaning of
the heat exchanger tubes, without disturbing the external pipes.
NIH - Nozzle in head.
NPFA - National Fire Protection
Association
Nozzle-In-Head Waterbox
- A type of waterbox in which the nozzles enter through one or
both of the waterbox covers, with the nozzles oriented parallel
to the axis of the heat exchanger shells.
Oil Separator - In a chiller
utilizing a screw compressor, an oil separator is often used to
remove lubricating oil from the refrigerant vapor at the discharge
of the compressor, in order to keep the oil from collecting in
the heat exchangers.
Open-Drive Motor - A motor
which is located outside the refrigerant containment of a chiller.
An open-drive motor requires that the rotating compressor shaft
pass through a seal between the outside atmosphere and the refrigerant
atmosphere inside the chiller.
Passes - In a shell-and-tube
heat exchanger, the number of passes is the number of times the
fluid flowing inside the tubes flows the length of the heat exchanger.
For example, a two-pass cooler has the cooled fluid inside the
tubes flowing from the inlet end of the cooler to the opposite
end, and then back to the inlet end, where the fluid exits the
cooler.
PIC - Product Integrated
Control. PICs are used in conjunction with the Carrier Comfort
Network to control and monitor the operation of Carrier chillers.
Positive Pressure Design
- A chiller design using a refrigerant which operates above atmospheric
pressure in all parts of the system. These chillers are typically
smaller than negative pressure design chillers at similar capacities,
and air and water vapor are kept out of the system by the positive
pressure difference.
Power Panel - Houses all
230 or 115 control voltage components.
PSIO - Processor Sensor
Input/Output module
Pumpdown Unit - System
which transfers refrigerant from a chiller to a storage tank,
or into an isolated section of a chiller, for service. The pumpdown
unit is also capable of evacuating a chiller prior to re-introducing
the refrigerant, for minimum contamination of the refrigerant
by air or water vapor.
Purge Device - A device
which removes air and water vapor from the refrigerant inside
a chiller. A purge is a necessity in negative pressure designs,
but is not necessary in positive pressure designs where air and
water vapor are kept out of the system by the internal pressure.
Refrigerant - The fluid
which removes heat from the fluid being chilled and rejects the
heat into the cooling fluid. In a vapor compression cycle, the
refrigerant undergoes two changes of state: refrigerant liquid
is boiled into low pressure vapor in the cooler as it removes
heat from the chilled fluid; high pressure refrigerant vapor is
condensed to a liquid in the condenser as it gives up heat to
the cooling fluid.
Screw Compressor - A type
of compressor used in vapor compression refrigeration cycles where
two intermeshing helical rotors create pockets of continuously
decreasing volume, in which the refrigerant vapor is compressed
and its pressure is increased from cooler pressure to condenser
pressure.
Single Stage Centrifugal Compressor
- Type of centrifugal compressor having one impeller.
Slide Valve - In screw
compressors, this is the capacity control mechanism.
SMM - Starter Management
Module. This implements PSIO commands for starter functions.
Solenoid valve - In screw
compressors, this is the mechanism that controls the movement
of the slide valve through signals from the PSIO.
Solid State Starter -
Provides smooth, stepless acceleration of a chiller's motor from
stop to full speed. The "soft start" reduces the mechanical
stress on the compressor.
Storage Tank - A steel
shell in which the refrigerant charge for a chiller may be temporarily
stored while the chiller is serviced.
Subcooler - This is a
section of some condensers in which the temperature of the condensed
refrigerant liquid is reduced. This improves the energy efficiency
of the chiller.
Thrust Bearing - A bearing
which absorbs the axial forces produced in a centrifugal compressor
by the refrigerant pressure differential across the impeller.
Ton - The English unit
of measure for chiller capacity or refrigeration. One ton of refrigeration
is the refrigeration produced by melting one ton of ice at 32
degrees F in 24 hours.
Turbine - A device mounted
on a shaft extended from the end of the motor on Carrier 19XRT
chillers. High pressure refrigerant liquid from the condenser
flows through the turbine, causing it to turn, helping the motor
to turn, thus reducing chiller operating energy. Carrier patented
design.
Two Stage Centrifugal Compressor
- Type of centrifugal compressor having two impellers. The first
stage impeller raises the pressure of the refrigerant vapor approximately
half way from the cooler pressure to the condenser pressure, and
the second stage impeller raises the pressure the rest of the
way. With a two stage compressor, an interstage economizer may
be used to improve the refrigeration cycle efficiency.
UL - Underwriters' Laboratories
Vapor Compression Cycle
- A refrigeration cycle consisting of a cooler, a compressor,
a condenser, and an expansion device. In the cooler, heat is removed
from the fluid being cooled by the boiling of liquid refrigerant
into vapor. The compressor continuously draws this low pressure
vapor from the cooler, and adds energy to the refrigerant, increasing
its pressure and temperature, and discharges the high pressure
vapor to the condenser. In the condenser, the cooling fluid removes
heat from the refrigerant, which is condensed into liquid. The
expansion device, which may be a float valve or an orifice, drops
the pressure of the refrigerant liquid back down to cooler pressure.
Volume Index (volume ratio)
- For screw compressors, this is the trapped volume existing at
the beginning of the compression process divided by the reduced
volume at the point of initial exposure to the discharge port.
Waterbox - For a shell
and tube heat exchanger which has the water or brine flowing through
the tubes, the waterbox is a chamber on each end of the shell
into which all of the tubes empty. At the inlet end of the heat
exchanger, an inlet nozzle (pipe) connects to the waterbox, and
the fluid flows from the nozzle into the waterbox and into the
first pass of the tubes; at the outlet end of the heat exchanger,
an outlet nozzle connects to the waterbox, and the fluid flows
from the last pass of the tubes into the waterbox and into the
outlet nozzle.