Carnot Cycle -
The most efficient heat engine cycle is the Carnot cycle, consisting of two
isothermal processes and two
processes. The Carnot cycle can be thought of as the most efficient heat
engine cycle allowed by physical laws
CALCAREOUS COATING OR DEPOSIT
- A layer consisting of a mixture of
calcium carbonate and magnesium hydroxide deposited on surfaces being cathodically protected against corrosion, because of increased pH adjustment to
the protected surface.
CO - Carbon monoxide (CO) is a colorless, odorless, poisonous gas. It
is produced by the incomplete burning of solid, liquid, and gaseous fuels.
Appliances fueled with natural gas, liquefied petroleum (LP gas), oil, kerosene,
coal, or wood may produce CO. Burning charcoal produces CO. Running cars produce
CO2 - is an atmospheric gas composed of one carbon and two oxygen atoms.
Carbon dioxide results from the combustion of organic matter if sufficient
amounts of oxygen are present. It is also produced by various microorganisms in
fermentation and is breathed out by animals. Plants absorb carbon dioxide during
photosynthesis, using both the carbon and the oxygen to construct carbohydrates.
It is present in the Earth's atmosphere at a low concentration and acts as a
greenhouse gas. It is a major component of the carbon cycle.
CALCIUM - A scale forming element found in boiler
CALCIUM CHLORIDE - A substance used to obtain calcium chloride
CALCIUM SULFATE - Chemical compound (CaSO4) which is used at a
drying agent or desiccant in liquid line dryers.
CALIBRATION - A process of dividing and numbering the scale of an
instrument; also of correcting or determining the error of an existing scale, or
of evaluating one quantity in terms of readings of another.
CALORIE - It is equal to the amount of heat required to raise the
temperature of one gram of water one degree Celsius.
CALORIMETER - Device used to measure quantities of heat or determine
CHANGE OF STATE - Change from one phase, such as solid, liquid or gas, to
CAPACITANCE - The property of an electric current that permits the
storage of electrical energy in an electrostatic field and the release of that
energy at a later time.
CAPACITOR, (CONDENSER) - A device that can store an electric charge when
voltage is applied.
CAPACITY - The adsorption activity possessed in varying degrees by
ion-exchange materials. This quality may be expressed as kilograms per cubic
foot, gram-milliequivalents per gram, pound-equivalents per pound,
gram-milliequivalents per milliliter, and so on, where the numerators of these
ratios represent the weight of the ions adsorbed and the denominators represent
the weight or volume of the adsorbent.
CAPILLARY - The name given to the thin tube attached to the bulb which
transmits the bulb pressure changes to the controller or indicator. The cross
sectional area of the capillary is extremely small compared to the cross section
of the bulb so that the capillary, which is usually outside of the controlled
fluid, will introduce the smallest possible error in the signal being
transmitted from the bulb.
CAPILLARY TUBE - The capillary tube is a metering device made from a thin
tube approximately 0.5 to 6 meter long and from 0.025 to 0.090 inches in
diameter which feeds liquid directly to the evaporator. Usually limited to
systems of 1 ton or less, it performs all of the functions of the thermal
expansion valve when properly sized.
CARBON DIOXIDE - Compound of carbon and oxygen (CO2) which is
sometimes used as a refrigerant. Refrigerant number is R-744.
CARBON FILTER - Air filter using activated carbon as air cleansing
CARBON RINGS - To minimize steam leakage, gland sealing arrangement
features an angle-type, carbon ring design with a packing case that is an
integral part of the turbine case. Inconel springs hold the rings in place.
- Colorless nonflammable and very toxic liquid used
as a solvent. It should never be allowed to touch skin and fumes must not be
CARBONACEOUS EXCHANGER - Ion-exchange materials of limited capacity
prepared by the sulfonation of coal, lignite, peat, and so on.
CARBONATE - An ion or salt of carbonic acid, containing carbon and oxygen
such as calcium carbonate. (CaC03)
CARBONATE HARDNESS - That hardness caused in water by bicarbonates and
carbonates of calcium, and magnesium.
- A treatment method using synthetic
polymers, generally used with high hardness (60-70) ppm and high
CARBOXYLIC - A term describing a specific acidic group (COOH) that
contributes cat ion-exchange ability to some resins.
CARRYOVER - The moisture and entrained solids forming the film of steam
bubbles, as a result of foaming in a boiler. This condition is caused by a
faulty boiler water condition. See also foaming.
CASCADE - A series of stages in which the output of one stage is the
input of the next stage.
CASCADE SYSTEMS - Arrangement in which two or more refrigerating systems
are used in series; uses evaporator of one machine to cool condenser of other
machine. Produces ultra-low temperatures.
CATHODE - In electrolysis or electrochemical corrosion, a site on a
surface where actions in solution are neutralized by electrons to become
elements that either plate out on the surface or react with water to produce a
- A method of preventing corrosion by making the
metal a cathode in a conducting medium by means of a direct electrical current
that is galvanic.
- Reduction of corrosion rate by shifting the
corrosion potential of the electrode towards less oxidizing potential by
applying an external electromotive force.
CATION - A positively charged ion that migrates through the electrolyte
toward the cathode under the influence of a potential gradient.
CATION-EXCHANGE SOFTENERS - Ion exchange units are known primarily as
water softeners. But they can also remove nitrates, sulfates, and various toxic
metals from water.
CATIONIC - The condition of a polymer, colloid, or large particle having
exchangeable anions on its surface and an opposite, positive charge on the
CAUSTIC CRACKING - A form of stress-corrosion cracking most frequently
encountered in carbon steels or iron-chromium-nickel alloys that are exposed to
concentrated hydroxide solutions at temperature of 200 to 250°C.
CAUSTIC EMBRITTLEMENT - An obsolete term replaced by caustic
CAUSTIC SODA - A common water treatment chemical, sodium
CAVITATION - The formation and collapse, within a liquid, of cavities or
bubbles that contain vapor or gas or both. In general, cavitation originates
from decreases in static pressure in the liquid. In order to erode a solid
surface by cavitation, it is necessary for the cavitation bubbles to collapse on
or close to that surface.
- Progressive loss of original material from a solid
surface due to continuing exposure to cavitation.
CELSIUS TEMPERATURE SCALE
- A thermometric scale in which the freezing
point of water is called 0°C and its boiling point 100°C at normal atmospheric
CENTANE NUMBER - A measure of ignition quality of a fuel or petroleum
with reference to normal centane high-ignition quality fuel with an arbitrary
number of 100.
- Pump which compresses gaseous fluids by
CENTRIFUGAL FORCE - is actually not a force but the experience of an
inertial force experienced in a rotating reference frame acting away from the
center of the rotation. It is equal in magnitude but opposite to the
centripetal force required to constrain the body to move in a circular
motion. s actually not a force but the experience of an
CENTRIFUGAL FORCE -On a centrifugal pump, it is that force which throws
water from a spinning impeller.
CENTRIFUGAL PUMP - A pump consisting of an impeller fixed on a rotating shaft
and enclosed in a casing, having an inlet and a discharge connection. The
rotating impeller creates pressure in the liquid by the velocity derived from
CENTRIFUGAL PUMP - Pump which produces fluid velocity and converts it to
is the force that causes an object to move in a circle, acting towards the
centre of the circle. In the case of a satellite the centripetal force is
gravity, in the case of an object at the end of a rope, the centripetal force is
the tension of the rope.
CHANGE OF STATE - Condition in which a substance changes from a solid to
a liquid or a liquid to a gas caused by the addition of heat. Or the reverse, in
which a substance changes from a gas to a liquid, or a liquid to a solid, caused
by the removal of heat.
CHANNELING - Cleavage and furrowing of the bed due to faulty operational
procedure, in which the solution being treated follows the path of least
resistance, runs through these furrows, and fails to contact active groups in
other parts of the bed, (water treatment).
CHARGE - Amount of refrigerant placed in a refrigerating unit.
CHARGING BOARD - Specially designed panel or cabinet fitted with gauges,
valves and refrigerant cylinders used for charging refrigerant and oil into
CHECK VALVE - Device which permits fluid flow in one direction.
CHELATE - Is a molecule, similar to an ion exchanger, capable to withdraw
ions from their water solutions into soluble complexes.
CHEMICAL CLEANING - Using a solvent solution to remove mill scale and
CHEMICAL FEEDLINE - The line which feeds the boiler treatment chemicals
into the boiler.
CHEMICAL PRECIPITATION - When the chemicals react with the dissolved
minerals in the water to produce a relative insoluble reaction product. A
typical example of this takes place with the lime-soda softening process.
- System of cooling using a disposable
refrigerant. Also called an expendable refrigerant system.
- Resistance to chemical change which ion-exchange
resins must possess despite contact with aggressive solutions.
CHILL FACTOR - Calculated number based on temperature and wind
- A re-circulating water system using water chilled
in a refrigeration machine as a source for cooling.
CHILLER/HEATERS - A unit that supplies either chilled water for cooling
or hot water for heating, (HVAC).
CHLORIDE - An ion, compound, or salt of chlorine, such as sodium chloride
(NaCl) or calcium chloride (CaCl2).
CHLORINATION - A process in which chlorine gas or other chlorine
compounds are added to the water for the purpose of disinfecting.
CHOKE TUBE - Throttling device used to maintain correct pressure
difference between high-side and low-side in refrigerating mechanism. Capillary
tubes are sometimes called choke tubes.
- A thermocouple installed in furnace tubes,
designed to measure the effectiveness of water treatment within the
CIRCUIT - An electrical arrangement requiring a source of voltage, a
closed loop of wiring, an electric load and some means for opening and closing
CIRCUIT BREAKER - A switch-type mechanism that opens automatically when
it senses an overload (excess current).
CLAY - Finely suspended earth mineral sometimes found as an impurity in
CLEARANCE SPACE - Space between top of piston and the valve plate.
CLEARANCE VAPOR - The vapor remaining in the clearance space at the end
of each discharge stroke.
CLOSED CYCLE - is the gas turbine arrangement, in which the exhaust is
directed back again to compressor without coming in contact with the atmospheric
CLOSED FEED WATER HEATER - An indirect-contact feed water heater. Steam and
water are separated by tubes.
CLOSED RE-CIRCULATING WATER SYSTEM - A system using as a
heat-transfer medium water that continuously circulates through closed piping
and heat exchanger without evaporation.
CO COAGULANT - A substance that promotes the clumping of particulate
matter in water, forming a larger mass and thus promoting settling of
particulates and clarification of the water.
COAGULATION - Is the process whereby finely divided particles of
turbidity and color, capable of remaining in suspension indefinitely, are
combined by chemical means into masses sufficiently large to effect rapid
COALESCENCE - The gathering together of coagulated colloidal liquids into
a single continuous phase.
CODE INSTALLATION - Refrigeration or air conditioning installation which
conforms to the local code and/or the national code for safe and efficient
CO-EFFICIENT OF CONDUCTIVITY - Measure of the relative rate at which
different materials conduct heat. Copper is a good conductor of heat and,
therefore, has a high coefficient of conductivity.
COEFFICIENT OF EXPANSION - A measure of the change in length or volume of
an oject, specifically, a change measured by the increase in length or volume of
an object per unit length or volume.
COEFFICIENT OF FRICTION - The dimensionless ratio of the friction force
(F) between two bodies to the normal force (N) pressing these bodies together -
m (f) = (F/N)
COEFFICIENT OF PERFORMANCE (COP)
- Ratio of work performed or
accomplished as compared to the energy used under designated operating
COEFFICIENT OF THERMAL EXPANSION - The fractional change in length (or
sometimes in volume, when specified) of a material for a unit change in
COGENERATION - A term used to describe the combination of different
thermodynamic cycles for the purpose of increasing all-over cycle
- a term applied to identify the generation of
people interested in co-generation.
COLD - The absence of heat; a temperature considerably below
COLD DECK -The cooling section of a mixed air zoning system.
COLD JUNCTION - That part of a thermoelectric system which absorbs heat
as the system operates.
COLD PROCESS - A water treatment process carried out at room
COLD WALL - Refrigerator construction which has the inner lining of
refrigerator serving as the cooling surface.
COLLOIDAL - A state of suspension in a liquid medium in which extremely
small particles are suspended and dispersed but not dissolved.
COLLOIDS - Organic matter of very fine particle size, usually in the
range of 10-5 to 10-7 cm in diameter. It tends to inhibit
the formation of dense scale and results in the deposition of sludge, or causes
it to remain in suspension, so that it may be blown from the boiler.
COLUMN OPERATION - Conventional utilization of ion-exchange resins in
columns through which pass, either upflow or down flow, the solution to be
COMBINED FEEDER CUTOFF - A device that regulates makeup water to a boiler
in combination with a low-water fuel cutoff.
COMBINED STEAM-GAS PLANT
- where a gas turbine is combined with steam
plant in order to utilize the waste heat.
- A method of physical treatment , followed by the
addition of chemicals to remove oxygen.
COMBUSTION - The act or process of burning.
COMFORT CHART - A chart showing effective temperatures with dry-bulb
temperatures and humidity's (and sometimes air motion) by which the effects of
various air conditions on human comfort may be compared.
COMFORT COOLER - System used to reduce the temperature in the living
space in homes. These systems are not complete air conditioners as they do not
provide complete control of heating, humidifying, dehumidification, and air
COMFORT COOLING - Refrigeration for comfort as opposed to refrigeration
for storage or manufacture.
COMFORT ZONE - (Average) the range of effective temperatures over which
the majority (50 percent or more) of adults feels comfortable; (extreme) the
range of effective temperatures over which one or more adults feel comfortable.
An area on the psychometric chart which shows conditions of temperature,
humidity and sometimes air movement in which most people are comfortable.
COMMON NEUTRAL - A neutral conductor that is common to, or serves, more
than one circuit.
COMPOSITION - The elements or chemical components that make up a material
and their relative proportions.
COMPOUND - They are chemically combined elements with definite
proportions of the component elements.
COMPOUND GAUGE - Instrument for measuring pressures both above and below
COMPOUND REFRIGERATING SYSTEMS
- System which has several compressors or
compressor cylinders in series. The system is used to pump low pressure vapors
to condensing pressures.
COMPRESSION - Term used to denote increase of pressure on a fluid by
using mechanical energy.
COMPRESSION RATIO - Ratio of the volume of the clearance space to the
total volume of the cylinder. In refrigeration it is also used as the ratio of
the absolute low-side pressure to the absolute high-side pressure.
COMPRESSION, ADIABATIC - Is compressing a gas without removing or adding
COMPRESSOR - Pump of a refrigerating mechanism which draws a low pressure
on cooling side of refrigerant cycle and squeezes or compresses the gas into the
high-pressure or condensing side of the cycle.
COMPRESSOR - The pump which provides the pressure differential to cause
fluid to flow and in the pumping process increases pressure of the refrigerant
to the high side condition. The compressor is the separation between low side
and high side.
COMPRESSOR DISPLACEMENT - Volume, in cubic inches, represented by the
area of the compressor piston head or heads multiplied by the length of the
COMPRESSOR SEAL - Leak proof seal between crankshaft and compressor body
in open type compressors.
COMPRESSOR SURGING - An instability of air flow with axial compressor on
the first stages of these compressors. Air flow might even be reversed that
- in terms of a gas turbine arrangement, it is the
turbine which drives the compressor only.
COMPRESSOR, CLEARANCE POCKET
- Small space in a cylinder from which
compressed gas is not completely expelled. This space is called the compressor
clearance space or pocket. For effective operation, compressors are designed to
have as small a clearance space as possible.
COMPRESSOR, ROTARY BLADE
- Mechanism for pumping fluid by revolving
blades inside cylindrical housing.
- Compressor having only one compressive step
between low-side pressure and high-side pressure.
COMPRESSIBILITY - The ease which a fluid may be reduced in volume by the
application of pressure, depends upon the state of the fluid as well as the type
of fluid itself.
CONDENSATE - The liquid formed by condensation of a vapor. In steam
heating, water condensed from steam; in air conditioning, water extracted from
air, as by condensation on the cooling coil of a refrigeration machine.
- A device used to clean the returning condensate to
the boiler feedwater system.
CONDENSATE PUMP - Device to remove water condensate that collects beneath
CONDENSATION - Process of changing a vapor into liquid by extracting
heat. Condensation of steam or water vapor is effected in either steam
condensers or dehumidifying coils, and the resulting water is called condensate.
CONDENSE - Action of changing a gas or vapor to a liquid.
CONDENSER - An apparatus used to transfer heat from a hot gas,
simultaneously reducing that gas to a liquid.
CONDENSER TUBE - The heat transfer surface in a condenser.
- A re-circulating cooling water used as a heat
transfer fluid for the condensation of a gas.
CONDENSING TEMPERATURE - The temperature at which the condensing gas is
returned to a liquid at the same pressure.
CONDENSING TURBINE - With this turbine, the steam exhausts to the
condenser and the latent heat of the steam is transferred to the cooling water.
The condensed steam is returned to the boiler as feedwater.
CONDENSING UNIT - Part of a refrigerating mechanism which pumps vaporized
refrigerant from the evaporator, compresses it, liquefies it in the condenser
and returns it to the refrigerant control.
CONDENSING UNIT SERVICE VALVES
- Shutoff valves mounted on condensing
unit to enable service technicians to install and/or service unit.
CONDENSING UNIT, REFRIGERANT
- An assembly of refrigerating components
designed to compress and liquefy a specific refrigerant, consisting of one or
more refrigerant compressors, refrigerant condensers, liquid receivers (when
required) and regularly furnished accessories.
- The reciprocal (opposite) of resistance and is
the current carrying ability of any wire or electrical component. Resistance is
the ability to oppose the flow of current.
CONDUCTANCE, SURFACE FILM
- Time rate of heat flow per unit area under
steady conditions between a surface and a fluid for unit temperature difference
between the surface and fluid.
CONDUCTION - Transfer of heat by direct contact.
- The ability of a liquid to conduct an
electrical current and indicating the presence of cat ions and anions.
Conductivity is usually expressed in Micromos per cm.
- The time rate of heat flow through unit
thickness of an infinite slab of homogeneous material in a direction
perpendicular to the surface, induced by unit temperature difference. (W/m · K)
CONDUCTIVITY METER - An electric instrument used to measure the
conductivity of water to determine its content of dissolved solids.
- The time rate of heat flow through unit area and
unit thickness of a homogeneous material under steady conditions when a unit
temperature gradient is maintained in the direction perpendicular to area.
Materials are considered homogeneous when the value of the thermal conductivity
is not affected by variation in thickness or in size
CONDUCTOR - Substance or body capable of transmitting electricity or
CONDUIT - A round cross-section electrical raceway, of metal or plastic.
CONGEALER - Also known as freezer.
CONGRUENT PHOSPHATE CONTROL - Similar as a coordinated phosphate control
but more restrictive where the equilibrium is based on maintaining a ratio of
2.6 Na/1.0 PO4, instead of 3.0/1.0 PO4.
CONNECTED LOAD - The sum of all loads on a circuit. (1) Connection in
Parallel: System whereby flow is divided among two or more channels from a
common starting point or header. (2) Connection in Series: System whereby flow
through two or more channels is in a single path entering each succeeding
channel only after leaving the first or previous channel.
CONSTRICTOR - Tube or orifice used to restrict flow of a gas or a
CONTAMINATION - The introduction into water of microorganisms, chemicals,
toxic materials, waste water in a concentration that makes the water unfit for
its next intended use.
CONTROL - A device for regulation of a system or component in normal
operation, manual or automatic. If automatic, the implication is that it is
responsive to changes of pressure, temperature or other property whose magnitude
is to be regulated.
CONTROL POINT - The value of the controlled variable which the controller
operates to maintain.
CONTROL VALVE - Valve which regulates the flow or pressure of a medium
which affects a controlled process. Control valves are operated by remote
signals from independent devices using any of a number of control media such as
pneumatic, electric or electro hydraulic.
CONTROLLED DEVICE - One which receives the converted signal from the
transmission system and translates it into the appropriate action in the
environmental system. For example: a valve opens or closes to regulate fluid
flow in the system.
CONTROLLER - A device capable of measuring and regulating by receiving a
signal from a sensing device, comparing this data with a desired value and
issuing signals for corrective action.
CONVECTION - The movement of a mass of fluid (liquid or gas) caused by
differences in density in different parts of the fluid; the differences in
density are caused by differences in temperature. As the fluid moves, it carries
with it its contained heat energy, which is then transferred from one part of
the fluid to another and from the fluid to the surroundings.
- Convection resulting from forced circulation of a
fluid, as by a fan, jet or pump.
- Circulation of gas or liquid (usually air or water)
due to differences in density resulting from temperature changes.
CONVERGENT NOZZLE - Impulse Turbine - Stationary convergent nozzles are
used for smaller pressure drops where the minimum exit pressure is 0.577 x the
inlet pressure (the critical pressure for nozzles.) If the exit pressure is less
than 0.577 x inlet pressure, eddy-currents are developed and the exit velocity
will be less than calculated.
CONVERGENT-DIVERGENT NOZZLE - Impulse Turbine - Stationary
convergent-divergent nozzles prevent eddy-currents and the calculated velocity
will be obtained even at large pressure drops.
COOLER - Heat exchanger which removes heat from a substance.
COOLING EFFECT, SENSIBLE
- The difference between the total cooling
effect and the dehumidifying effect, usually in watts.
COOLING EFFECT, TOTAL - Difference between the total enthalpy of the dry
air and water vapor mixture entering the cooler per hour and the total enthalpy
of the dry air and water vapor mixture leaving the cooler per hour, expressed in
COOLING TOWER - Device for lowering the temperature of water by
evaporative cooling, in which water is showered through a space through which
outside air circulates. A portion of the water evaporates, its latent heat of
vaporization cooling that portion of the water which does not evaporate.
- Involves the adiabatic exchange of heat between
air and water spray or wetted surface. The water assumes the wet-bulb
temperature of the air, which remains constant during its traverse of the
COOLING, REGENERATIVE - Process of utilizing heat which must be rejected
or absorbed in one part of the cycle to function usefully in another part of the
cycle by heat transfer.
COORDINATED PHOSPHATE CONTROL A treatment to prevent caustic gauging.
Free caustic is eliminated by maintaining an equilibrium between the sodium and
phosphate. Control is based on maintaining a ratio of 3.0 Na to/1.0
CORROSION - The chemical or electrochemical reaction between a material,
usually a metal, and its environment that produces a deterioration of the
material and its properties.
CORROSION, ANODE - The dissolution of an metal acting as an anode.
- The gradual degradation or alteration of a
material by contact with substances present in the atmosphere, such as oxygen,
carbon dioxide, water vapor, and sulfur and chlorine compounds.
CORROSION, BIOLOGICAL - Deterioration of metals as a result of the
metabolic action of microorganisms. Also often named fouling.
CORROSION, CATHODIC - Corrosion resulting resulting from a cathodic
condition of a structure usually caused by the reaction of an amphoteric metal
with the alkaline products of electrolysis.
CORROSION, CAVITATION - A process involving conjoint corrosion and
CORROSION, CONCENTRATION ATTACK
- A form of corrosion caused by
the concentration of caustic or phosphate salts under porous deposits, generally
iron oxide. Sometimes found at welded tubes and due to steam blanketing.
- Pitting type of corrosion caused by an
electrical potential differential between surfaces of a metal as a result of
deposits or differences in the solution concentration in contact with the
CORROSION, COUPONS - Pre-weighed metal strips installed into fluid
systems for the purpose of monitoring metal losses.
CORROSION, CREVICE -
Localized corrosion of a metal surface at, or
immediately adjacent to an area that is shielded from full exposure to the
environment because of close proximity between metal and the surface of another
CORROSION, DEACTIVATIONS - The process of prior removal of the active
corrosive constituents, usually oxygen, from a corrosive liquid by controlled
corrosion of expendable metal or by other chemical means, thereby making the
liquids less corrosive.
(also called poultice corrosion) - Corrosion occurring
under or around a discontinuous deposit on a metallic surface.
CORROSION, EFFECT - A change in any part of the corrosion system caused
CORROSION, ELECTROCHEMICAL - Corrosion that is accompanied by a low of
electrons between cathodic and anodic areas on metallic surfaces.
CORROSION, EMBRITTLEMENT - The severe loss of ductility of a metal
resulting from corrosive attack, usually intergranular and often not visible.
CORROSION, EXTERNAL - A chemical deterioration of the metal on the
fireside of boiler heating surfaces.
CORROSION, FATIGUE - The process in which a metal fractures prematurely
under conditions of simultaneous corrosion and repeated cyclic loading at lower
stress levels or fewer cycles than would be required in the absence of the
- Corrosion that occurs under organic coatings on
metals as fine wavy hairlines.
CORROSION, FRETTING - A type of corrosion which occurs where metals slide
over each other. Long tubes in heat exchangers often vibrate, causing metal to
metal contact, tube supports etc.. The metal to metal rubbing causes mechanical
damage to the protective oxide coating.
- Corrosion of a metal caused by its contact with a
metal of lower activity; this contact results in an electron flow or current and
dissolution of one of the metals.
- Corrosion with gas as the only corrosive agent and
without any aqueous phase on the surface of the metal. Also called dry
CORROSION, GENERAL - A form of deterioration that is distributed more or
less uniformly over a surface.
- Corrosion of grey iron in which the iron matrix is
selectively leached away, leaving a porous mass of graphite behind. This type of
corrosion occurs in relative mild aquous solutions and on buried piping.
CORROSION, HOT - An accelerated corrosion of metal surfaces that results
from the combined effect of oxidation and ractions with sulfur compounds or
other contaminants such as chlorides, to form a molten salt on a metal surface
that fluxes, destroys or disrupts the normal protective oxide. (commonly
found in pulp mills)
- A form of erosion-corrosion generally associated
with local impingement of a high velocity, flowing fluid against a solid
CORROSION, INFLUENCED - The corrosion cause by organisms due to their
discharge containing sulfur compounds and the depolarization with other types of
discharge due to the presence of the microorganisms.
- Substances that slow the rate of
-(see intergranular cracking)
- Localized attack occurring on the metal grain
boundaries. This is commonly found with stainless steels which have been
improperly heat treated.
- Usually refers to the internal corrosion and is
considered an electrochemical deterioration of the boiler surface at or below
the water surface.
CORROSION, LOCALIZED - Corrosion at discrete sites, for example, crevice
corrosion, pitting, and stress-corrosion cracking.
CORROSION, LOCALIZED - Non-uniform corrosion of a metal surface
highlighted by spotty or pitting-type corrosion.
CORROSION, MICROBIAL - (see biological corrosion).
CORROSION, OXYGEN DEFICIENCY - A form of crevice corrosion in which
galvanic corrosion proceeds because oxygen is prevented from diffusing into the
CORROSION, POTENTIAL - The voltage between a corroding metal and a
- (see corrosion, deposit)
CORROSION, POULTICE - A term used in the automotive industry to describe
the corrosion of vehicle body parts due to the collection of road salts and debries on ledges and in pockets that are kept moist by weather and
- Modification of a corrosion system so that
corrosion damage is mitigated.
- The ability of a material to resist deterioration
by chemical or electrochemical reaction with its environment.
CORROSION, STRAY CURRENT - A form of attack caused by electrical currents
going through unintentional path.
CORROSION, STRESS - Preferential attack of areas under stress in a
corrosive environment, where such a environment alone would not have caused
CORROSION, STRESS CORROSION CRACKING - Material deterioration due
to cracking, by being under static stress either applied or residual.
CORROSION, SWEET - The deterioration of metal caused by contact with
carbon dioxide in water.
CORROSION, THERMO-GALVANIC - Corrosion resulting from an
electrochemical cell caused by a thermal gradient.
- The simplest form of corrosion. It attacks all
surfaces exposed to a corrodent.
CORROSIVE WEAR - A material deterioration due to the co-joint action of
corrosion and mechanical action.
CORROSIVITY - An indication of the corrosiveness of the water of
material. The corrosivity of a water as described by the water’s pH, alkalinity,
hardness, temperature, total dissolved solids, dissolved oxygen concentration
and the Langerier Index.
COUNTER-FLOW HEAT EXCHANGER
- When the fluid to be cooled flows against
the direction of the coolant. In heat exchange between two fluids, opposite
direction of flow, coldest portion of one meeting coldest portion of the
COVALENT BOND - A bond in which two atoms share pair of electrons.
CRANKSHAFT SEAL - Leak proof joint between crankshaft and compressor
CRAZE CRACKING (OR CHECKING) - Irregular surface cracking of metal
associated with thermal cycling.
CREEP - Time dependent permanent strain under stress. This is used to
rate the resistance of a material to plastic deformation under sustained
CREEP STRENGTH - The constant nominal stress that will cause a specified
quantity of creep in a given time at constant temperature. Creep strength is
expressed as the stress necessary to produce 0.1% strain in 1000 hours.
CREEP, DYNAMIC - Creep that occurs under conditions of fluctuating load
or fluctuating temperatures.
CRISPER - Drawer or compartment in refrigerator designed to provide high
humidity along with low temperature to keep vegetables, especially leafy
vegetables - cold and crisp.
CRITICAL HUMIDITY - The relative humidity above which the atmospheric
corrosion rate of some metals increase sharply.
CRITICAL POINT - A point at which the saturated liquid and saturated
vapor states are identical. Also, the latent heat of evaporization is zero at
CRITICAL PRESSURE - The pressure at the critical temperature above which
the fluid no longer has the properties of a liquid, regardless of further
increase of pressure.
- That temperature above which the vapor phase
cannot be condensed to liquid by an increase in pressure.
CRITICAL VELOCITY - Maximum velocity is obtained and no further
pressure drop is obtained. (Acoustic Velocity).
CROSS COMPOUND TURBINE - These turbines are large turbines with
parallel shafts with a generator on each shaft. The steam flows through the high
pressure turbine, then is crossed-over to the low pressure turbine
CRT - Cathode ray tube terminal.
CRYOGENIC FLUID - Substance which exists as a liquid or gas at ultra-low
temperatures - 157°C.
CRYOGENIC SUPERCONDUCTOR SYSTEM
- Uses helium to cool conductors to
within few degrees of absolute zero where they offer no electric
CRYOGENICS - Refrigeration which deals with producing temperatures of
-157°C below zero and lower.
Crystal Formation, Zone of Maximum: Temperature range in freezing in which
most freezing takes place, i.e., about 25¡F to 30¡F for water.
CRYSTALLITES - Atoms arranged in a repeating and definite
CRYSTALLIZATION - The separation, usually from a liquid phase on cooling,
of a solid crystalline phase.
CURRENT (I) - The electric flow in an electric circuit, which is
expressed in amperes (amps).
CURRENT DENSITY - The current flowing to or from a unit area of an
CURTIS METHOD or Curtis stage - Velocity Compounding - This turbine
design consists of one set of nozzles in which the steam is expanded from
initial to exhaust pressure. The velocity of the steam resulting from this
expansion is absorbed in two or more rows of moving blades. Rows of fixed or
guide blades, attached to the casing, are set between rows of moving blades and
receive and redirect the steam to the next row of moving blades. As the velocity
is absorbed in more than one row of moving blades, the blade speed is less than
if the velocity was all absorbed in one row of blades.
CYCLE - A series of thermodynamic processes during which the working
fluid can be made to undergo changes involving energy transition and is
subsequently returned to its original state.
CYCLE, REVERSIBLE - Theoretical thermodynamic cycle, composed of a series
of reversible processes, which can be completely reversed.
CYCLE, WATER TREATMENT - A complete course of ion-exchange
operation. For instance, a complete cycle of cation exchange would involve
regeneration of the resin with acid, rinse to remove excess acid, exhaustion,
backwash, and finally regeneration.
CYCLES - A system that undergoes a series of processes and always returns
to its initial state.
CYCLES OF CONCENTRATION
- The number of times the soluble mineral salts
in a water supply have been concentrated in, a system.
CYLINDER HEAD - Plate or cap which encloses compression end of compressor