All Terms 3 Flashcards
1
Q
DUST
A
An air suspension (aerosol) or particles of any solid material, usually with particle size less than 100 microns.
2
Q
DYNAMIC DISCAHRGE HEAD
A
Static discharge head plus friction head plus velocity head.
3
Q
DYNAMIC LOAD
A
An imposed force that is in motion, that is, one that may vary in magnitude, sense, and direction.
4
Q
DYNAMIC PUMPS
A
Pumps in which energy is added to the water continuously and the water is not contained in a set volume.
5
Q
DYNAMIC SUCTION HEAD
A
Positive static suction head minus friction head and minus velocity head.
6
Q
DYNAMIC SUCTION LIFT
A
The sum of suction lift and velocity head at the pump suction when the source is below pump centerline.
7
Q
DYNAMIC SYSTEM
A
An ion
8
Q
ECONOMIZER
A
A series of tubes located in the path of flue gases. Feedwater is pumped through these tubes on its way to the boiler in order to absorb waste heat from the flue gas.
9
Q
EDDY CURRENT TESTING
A
An electromagnetic nondestructive testing method in which eddy
10
Q
EDTA
A
A chelating agent used with boiler water treatment. Often referred as the replacement for the phosphate
11
Q
EFFECTIVE TEMPERATURE
A
Overall effect on a human of air temperature, humidity and air movement.
12
Q
EFFECTIVE TEMPERATURE
A
Overall effect on a human of air temperature, humidity and air movement.
13
Q
EFFLUENT
A
The solution which emerges from an ion
14
Q
ELECTRIC DEFROSTING
A
Use of electric resistance heating coils to melt ice and frost off evaporators during defrosting.
15
Q
ELECTRICAL CIRCUIT
A
A power supply, a load, and a path for current flow are the minimum requirements for an electrical circuit.
16
Q
ELECTROCHEMICAL REACTIONS
A
A metal wasting process, due to the fluid (boiler water) being subjected to an electrical current.
17
Q
ELECTRODE BOILER
A
A boiler which generates steam or hot water by the action of immersed electrodes which conduct electricity through the boiler water, which, in turn, generates
18
Q
ELECTRODIALYSIS
A
This is a membrane process where an applied electric charge draws impurity ions through permeable membranes to create high purity feedwater streams or low
19
Q
ELECTROLYSIS
A
Chemical decomposition caused by action of an electric current in a solution.
20
Q
ELECTROLYTE
A
A chemical compound which dissociates or ionizes in water to produce a solution which will conduct an electric current
21
Q
ELECTROMECHANICAL
A
Converting electrical input into mechanical action. A relay is an electromechanical switch.
22
Q
ELECTROREGENERATION
A
Hydrogen and hydroxyl ions are formed be electrical splitting of water molecules and are swept through the unit by steady, low
23
Q
ELEMENT
A
A pure substance that cannot be broken down by chemical means to a simpler substance.
24
Q
ELEVATION HEAD
A
The energy possessed per unit weight of a fluid because of its elevation.
25
ELUTION
The stripping of adsorbed ions from an ion
26
EMULSION
A colloidal dispersion of one liquid in another.
27
ENDOTHERMIC REACTION
Pertaining to a chemical reaction which is accompanied by an absorption of heat.
28
ENERGY
Expressed in kilowatt
29
ENERGY
In the simplest terms, energy is the ability to perform work. It may exist in several forms, such as heat energy, mechanical energy, chemical energy, or electrical energy, and may
30
ENERGY
The ability to do work. Energy can exist in one of several forms, such as heat, light, mechanical, electrical or chemical. Energy can neither be created nor destroyed, but can be
31
ENERGY (CONSUMPTION) CHARGE
That part of an electric bill based on kWh consumption (expressed in cents per kWh). Energy charge covers cost of utility fuel, general operating
32
ENGINE
Prime mover
33
ENGINE OIL
An oil used to lubricate an internal combustion engine.
34
ENTHALPY
The total quantity of heat energy contained in a substance, also called total heat
35
ENTRAINMENT
The transport of water into a gas stream. In a boiler, this is carryover, in a cooling tower, drift.
36
ENTRAINMENT (HVAC)
The capture of part of the surrounding air by the air stream discharged from an outlet (some times called secondary air motion).
37
ENTROPY
The ratio of the heat added to a substance to the absolute temperature at which it is added.
38
ENVIRONMENT
The aggregate of all conditions (such as contamination, temperature, humidity, radiation, magnetic and electric fields, shock, vibration) that externally influence the
39
EPSON SALT
Magnesium sulfate.
40
EQUALIZING HOLE (STEAM TURBINE)
A hole in the turbine disc designed to equalize axial thrust with impulse bladed turbines.
41
EQUILIBRIUM REACTIONS
The interaction of ionizable compounds in which the products obtained tend to revert to the substance from which they were formed until a balance is
42
EQUIVALENT WEIGHT
Refers to the amount of an element combining with a unit weight of hydrogen. In terms of water treatment, a method used to calculate the concentration of a
43
EROSION , ABRASIVE
Erosive wear caused by relative motion of solid particles which are present in fluids and are moving parallel to a solid surface.
44
EROSION, CAVITATION
Progressive loss of original material from a solid surface due to continuing exposure to cavitation.
45
EROSION, IMPINGEMENT
Loss of material from a solid surface due to liquid impingement.
46
EROSION, LIQUID
Removal of films or metal by mechanical action and corrosion of active metal.
47
EROSION
CORROSION
48
ETHANE (R
170)
49
EUTECTIC
An isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids on cooling.
50
EUTECTIC POINT
Freezing temperature for eutectic solutions.
51
EVACUATION
The removal of gases from a system.
52
EVAPORATION
The change of state from liquid to vapor, for example as water evaporates to a vapor in a cooling tower.
53
EVAPORATIVE CONDENSER
A condenser which has water flowing over coils containing the refrigerant gas which is thus cooled and condensed by evaporation of that water.
54
EVAPORATIVE CONDENSER
Device which uses open spray or spill water to cool a condenser. Evaporation of some of the water cools the condenser water and reduces water
55
EVAPORATIVE COOLING
The adiabatic exchange of heat between air and a water spray or wetted surface. The water approaches the wet
56
EVAPORATOR
The heat exchanger in which the medium being cooled, usually air or water, gives up heat to the refrigerant through the exchanger transfer surface. The liquid
57
EVAPORATOR FAN
Fan which increases airflow over the heat exchange surface of evaporators.
58
EVAPORATOR PRESSURE REGULATOR
Automatic pressure regulating valve mounted in suction line between evaporator outlet and compressor inlet. Its purpose is to maintain a
59
EVAPORATOR, FLOODED
Evaporator containing liquid refrigerant at all times.
60
EXFlLTRATION
The flow of air outward from a space through walls, leaks, etc.
61
EXFOLIATION
Scaling off of a surface in flakes or layers as the result of corrosion.
62
EXHAUSTION
The state in which the adsorbent is no longer capable of useful ion exchange
63
determined arbitrarily in terms of (1) a value in parts per million of ions in the effluent solution
and (2) the reduction inequality of the effluent water determined by conductivity bridge
64
EXOTHERMIC
Chemical reaction in which heat is released.
65
EXPANSION JOINT
Device in piping designed to allow movement of the pipe caused by the pipe's expansion and contraction.
66
EXPANSION TANK
A reservoir usually above a closed re
67
EXPANSION VALVE
Device in refrigerating system which reduces the pressure from the high side to the low side and is operated by pressure.
68
EXPANSION VALVE, CAPILLARY TUBE
A tube of small internal diameter used as liquid refrigerant flow control and pressure reducer between high and low sides. Also used to
69
EXPANSION VALVE, THERMOSTATIC
Control valve operated by temperature and pressure within evaporator. It controls flow of refrigerant. Control bulb is attached to outlet of
70
EXPENDABLE REFRIGERANT SYSTEM
System, which discards the refrigerant after it has evaporated.
71
EXTERNAL DRIVE
Term used to indicate a compressor driven directly from the shaft or by a belt using an external motor. Compressor and motor are serviceable separately.
72
EXTERNAL EQUALIZER
Tube connected to low
73
EXTERNAL TREATMENT
Refers to the treatment of water before it enters the boiler.
74
FAIL SAFE
In load management, returning all loads to conventional control during a power failure. Accomplished by a relay whose contacts are normally closed.
75
FAILURE
A rupture, break, or disintegration of a metal or part of an HVAC system.
76
FALSE BRINELING
Damage to a solid bearing surface characterized by indentations not caused by plastic deformation resulting from overload, but thought to be due to other causes
77
FAN PERFORMANCE CURVE
Fan performance curve refers to the constant speed performance curve. This is a graphical presentation of static or total pressure and power input over
78
ex tends from shutoff (zero air volume flow rate) to free delivery (zero fan static pressure). The pressure curves are generally referred to as the pressure
volume curves.
79
FAN TUBE AXIAL
A propeller or disc type wheel within a cylinder and including driving mechanism supports for either belt drive or direct connection.
80
FAN, CENTRIFUAL
A fan rotor or wheel within a scroll type housing and including driving mechanism sup ports for either belt drive or direct connection.
81
FAN, PROPELLER
A propeller or disc type wheel within a mounting ring or plate and including driving mechanism supports for either belt drive or direct connection.
82
FAN, VANEAXIAL
A disc type wheel within a cylinder, a set of air guide vanes located either before or after the wheel and including driving mechanism supports for either belt drive or
83
FARAD
A unit of electric capacity, designated by F.
84
FATIGUE
The phenomenon leading to fracture under repeated or fluctuating stresses having maximum value less than the ultimate strength of the material.
85
FAULT
A short circuit either line to line, or line to ground.
86
FEED WATER
Water which is fed to a system such as a boiler or cooling tower.
87
FEED WATER LINE
The piping leading to a system through which the feed water flows.
88
FEEDWATER HEATER
A device used to heat feedwater with steam.
89
FERRIC COAGULANT
Ferric sulfate Fe2(SO4)3 act to precipitate ferric hydroxide, coagulate at 4.0
90
FERRIC HYDROXIDE
The complete reaction product of iron, water, and oxygen, which forms a red precipitate in water [Fe(OH)3]
91
FERRIC ION
An iron atom that has a positive electric charge of +3. (Fe2+)
92
FERROUS
Metallic materials in which the principle component is iron.
93
FERROUS HYDROXIDE
The reaction product of iron and water in the absence of oxygen
94
FERROUS ION
An iron atom that has a positive electric charge of + 2(Fe2+).
95
FILMING AMINES
Amines that form a impervious non
96
FILTER
A device to remove solid material from a fluid.
97
FILTER
DRIER
98
FILTRATION
Is the process of passing a liquid containing suspended matter through a suitable porous material in such a manner as to effectively remove the suspended matter from
99
FIN
An extended surface to increase the heat transfer area, as metal sheets attached to tubes.
100
FIRE POINT
The temperature at which a material will continue to burn for at least 5 seconds without the benefit of an outside flame.
101
FIRE TUBE
A tube, in a boiler, through which the hot gases flow and transfer heat to the water on the outside of the tube.
102
FIRE WALL
The back end of a boiler, opposite the burner, at which the hot gases change direction of flow.
103
FIREBRICK
A refractory brick, often made from fire clay, that is able to withstand temperature in the range of 1500 to 1600°C, and is used to line furnaces.
104
FIXED DISPLACEMENT PUMP
A pump in which the displacement per cycle cannot be varied.
105
FLASH
The portion of a superheated fluid converted to vapor when its pressure is reduced.
106
FLASH CHAMBER
A separating tank placed between the expansion valve and the evaporator to separate and bypass any gas formed in the expansion valve.
107
FLASH GAS
The gas resulting from the instantaneous evaporation of refrigerant in a pressure
108
FLASH POINT
The temperature at which a material to give off sufficient vapor to form a flammable mixture.
109
FLASH TANK
A vessel used for separating the liquid phase from the gaseous phase formed from a rise in temperature and/or a reduction of pressure on the flowing stream.
110
FLASHING
Evaporation of a liquid into a vapor.
111
FLOCCULANT
An electrolyte added to a colloidal suspension to cause the particles to aggregate and settle out as the result of reduction in repulsion between particles.
112
FLOCCULATION
The process of agglomerating coagulated particles into settable flocs, usually of a gelatinous nature.
113
FLOODBACK
The condition of liquid refrigerant returning, usually from an overfed evaporator, to the compressor through the suction line.
114
FLOTATION
A process of separating solids from water by developing a froth.
115
FLOW RATE
The volume of solution which passes through a given quantity of resin within a given time. Flow rate is usually expressed in terms of feet per minute per cubic foot of
116
FLOW, LAMINAR OR STREAMLINE
Fluid flow in which each fluid particle moves in a smooth path substantially parallel to the paths followed by all other particles.
117
FLOW, TURBULENT
Fluid flow in which the fluid moves transversely as well as in the direction of the tube or pipe axis, as opposed to streamline or viscous flow.
118
FLUID
The general term that includes gas, vapor or liquid
119
FLUID HEAD
The static pressure of fluid expressed in terms of the height of a column of the fluid, or of some manometric fluid, which it would support.
120
FLUIDIZED BED
A contained mass of finely divided solid that behaves like a fluid when brought into suspension in a moving gas.
121
FLY ASH
A finely divided siliceous material formed during the combustion of coal, coke, or other solid fuels.
122
FOAM CARRYOVER
Is the development of excessive moisture in the steam from carryover of foam from the drum. Usually common in low pressure boilers due to high concentration
123
FOAMING
Formation of steam bubbles on the surface of the boiler water due to high surface tension of the water.
124
FORCE
The action on a body which tends to change its relative condition as to rest or motion.
125
FORCE PUMP
A device used to inject a solution into a closed system through an opening such as a drain valve.
126
FORCED CONVECTION
Movement of fluid by mechanical force such as fans or pumps.
127
FORCED DRAFT COOLING TOWER
Cools water by mechanically forcing air through the tower.
128
FORCE
FEED OILING
129
FOULING
Deposits of impurities, dirt or foreign matter that clog systems or restrict flow and interfere with heat transfer.
130
FOULING FACTOR
The degree of interference with heat transfer.
131
FREEBOARD
The space provided above the resin bed in an ion
132
FREEZER
A refrigerating device designed to lower the temperature below 0°C.
133
FREEZER BURN
Condition applied to food which has not been properly wrapped and that has become hard, dry and discolored.
134
FREEZE
UP
135
FREEZING
Change of state from liquid to solid.
136
FREEZING POINT
The temperature at which a liquid becomes solid.
137
FREON
Trade name for a family of synthetic chemical refrigerants.
138
FRESH WATER
Water that has little or no salt dissolved in it.
139
FRICTION
Friction is the resistance found at the duct and piping walls. Resistance creates a static pressure loss in systems. The primary purpose of a fan or pump is to produce a
140
FRICTION HEAD
The pressure in psi or feet of the liquid pumped which represents system resistance that must be overcome.
141
FRIGORIFIC MIXTURE
Are substances used in laboratory methods of producing a drop in temperature. A common example is a mixture of snow and salt.
142
FROST
Frozen condensation.
143
FROST BACK
Condition in which liquid refrigerant flows from evaporator into suction line
144
FROST CONTROL
Semiautomatic
145
FROST FREE REFRIGERATOR
Refrigerated cabinet which operates with an automatic defrost during each cycle.
146
FROSTING TYPE EVAPORATOR
Refrigerating system which maintains the evaporator at frosting temperatures during all phases of cycle.
147
FRQUENCY
The number of vibrations, waves, or cycles of any periodic phenomenon per second. In architectural acoustics, the interest lies in the audible frequency range of 20 to
148
FUEL KNOCK
A hammer like noise produced when fuel is not burned properly in a cylinder.
149
FULL LOAD CURRENT
See Running Current.
150
FUMES
Solid particles commonly formed by the condensation of vapors from normally solid materials such as molten metals. Fumes may also be formed by sublimation, distillation,
151
FUNGUS
A lower form of plant life which does not contain chlorophyll, for example, a mold.
152
FUSIBLE PLUG
Plug or fitting made with a metal of a known low melting temperature. Used as safety device to release pressures in case of fire.
153
GAGE PRESSURE
Absolute pressure minus atmospheric pressure.
154
GALVANIC ACTION
Wasting away of two unlike metals due to electrical current passing between them. The action is increased in the presence of moisture.
155
GALVANIC CELL
Electrolytic brought about by the difference in electric potential between two dissimilar metals.
156
GALVANIC COUPLE
The connection of two dissimilar metals in an electrolyte that results in current flow through the circuit.
157
GALVANIZING
The coating of metal with another by an electrolytic process
158
for example, electrolytically zinc
coat steel is called galvanized steel.
159
GAS
Usually a highly superheated vapor which, within acceptable limits of accuracy, satisfies the perfect gas laws.
160
GAS
Vapor phase or strata of a substance.
161
GAS CONSTANT
The coefficient "R" in the perfect gas equation: PV = MRT.
162
GAS LUBRICATION
A system of lubrication in which the shape and relative motion of the sliding surfaces cause the formation of a gas film having sufficient pressure to separate the
163
GAS REFRIGERATION CYCLE
Where the refrigerant remains in the gaseous phase throughout.
164
GAS TURBINE
An engine in which gas , under pressure is formed by combustion, is directed against a series of turbine blades. The energy in the expanding gas is converted into
165
GAS TURBINE COMPRESSOR
a compressor designed foe the use with gas turbine installations. This could be centrifugal or an axial compressor.
166
GAS VALVE
Device in a pipeline for starting, stopping or regulating flow of gas.
167
GAS, INERT
A gas that neither experiences nor causes chemical reaction nor undergoes a change of state in a system or process
168
GASIFICATION
When a substance is converted to become a gas.
169
GASKET
A device, usually made of a deformable material, that is used between two relatively static surfaces to prevent leakage.
170
GAUGE MANIFOLD
Chamber device constructed to hold both compound and high
171
GAUGE VACUUM
Instrument used to measure pressures below atmospheric pressure.
172
GENERAL CORROSION
Uniform overall corrosion of metal surfaces.
173
GENERATING TUBE
A boiler tube used for evaporation.
174
GENERATOR
A machine that changes that changes mechanical energy into electrical energy.
175
GFI, GFCI
Ground fault (circuit) interrupter
176
GRAIN
A unit of weight
177
0.0648 grams
0.000143 pounds.
178
GRAIN BOUNDARIES
Referring to the junction of crystallites.
179
GRAINS OF MOISTURE
The unit of measurement of actual moisture contained in a sample of air. (7000 grains
180
GRAINS PER GALLON
A unit of concentration. 1 gr/gal = 17.1 mg/L.
181
GRAM
A unit of weight
182
15.432 grains
0.0022 pounds.
183
GRAM
MILLIQUIVALENTS
184
GRAVITY
The attraction exerted by the earth’s mass on objects at its surface.
185
GRAVITY, SPECIFIC
Density compared to density of standard material
186
GREASE
A lubricant composed of an oil thickened with a soap or other thickener to a solid or semisolid consistency.
187
GREASE, BLOCK
A grease that is sufficiently hard to retain its shape in block or stick form.
188
GREASE, SODA BASED
A grease prepared from lubricating oil and sodium soap.
189
GREEN LIQUOR
The liquor resulting from dissolved molten smelt from Kraft recovery furnace in water.
190
GREENSAND
Naturally occurring materials, composed primarily of complex silicates, which possess ion
191
GROOVING
A form of deterioration of boiler plate by a combination of localized corrosion and stress concentration.
192
GROUND
Zero voltage, or any point connected to the earth or "ground".
193
GROUND BED
Cathodic protection, an interconnected group of impressed
194
GROUND BUS
A busbar in a panel or elsewhere, deliberately connected to ground.
195
GROUND COIL
Heat exchanger buried in the ground. May be used either as an evaporator or as a condenser.
196
GROUND CONDUCTOR
Conductor run in an electrical system, which is deliberately connected to the ground electrode. Purpose is to provide a ground point throughout the system.
197
GROUND FAULT
An unintentional connection to ground.
198
GROUT
To force sealing material into a soil, sand or confined small space
199
HAC
Hydrogen
200
HALIDE LEAK DETECTOR
A device used to detect vapor leaks of halogen refrigerants. It uses acetylene as its base.
201
HALIDE REFRIGERANTS
Family of refrigerants containing halogen chemicals.
202
HALIDE TORCH
Type of torch used to safely detect halogen refrigerant leaks in system.
203
HALOGENS
Substance containing fluorine, chlorine, bromine and iodine.
204
HARD WATER
Water that contains dissolved compounds of calcium, magnesium or both.
205
HARDNESS
Are generally referred to the presence of calcium and magnesium content of the water.
206
HARDNESS
The scale
207
forming and lather
inhibiting qualities which water, high in calcium and magnesium ions, possesses.
208
HARDNESS CONTROL
An action designed to remove hardness and at the same time to produce an equivalent amount of suspended solids.
209
HARDNESS OF CALCIUM CARBONATE
The expression ascribed to the value obtained when the hardness
210
carbonate
a convenient method of reducing all salts to a common basic for comparison.
211
HEAD
Pressure, usually expressed in feet of water, inches of mercury or millimeters of mercury.
212
Head
The measure of the pressure of water expressed in feet of height of water: 1 psi = 2.31 feet of water.
213
HEAD DYNAMIC OR TOTAL
In flowing fluid, the sum of the static and velocity heads at the point of measurement.
214
HEAD PRESSURE
Pressure which exists in condensing side of refrigerating system.
215
HEAD PRESSURE CONTROL
Pressure
216
operated control which opens electrical circuit if high
side pressure becomes too high.
217
HEAD STATIC
The static pressure of fluid expressed in terms of the height of a column of the fluid, or of some manometric fluid, which it would support.
218
HEAD VELOCITY
Height of fluid equivalent to its velocity pressure in flowing fluid.
219
HEADER
Length of pipe or vessel to which two or more pipe lines are joined carries fluid from a common source to various points of use.
220
HEADLOSS
The loss of energy as a result of friction
221
HEAT
Form of energy which acts on substances to raise their temperature
222
HEAT CAPACITY
The amount of heat necessary to raise the temperature of a given mass one degree. Numerically, the mass multiplied by the specific heat.
223
HEAT CONDUCTOR
A material capable of readily conducting heat. The opposite of an insulator or insulation.
224
HEAT ENGINE
Mechanical devices which convert heat to work, such as the steam boiler, gas turbine, solar energy, refrigerators, steam engines, steam turbines.
225
HEAT EXCHANGER
Device used to transfer heat from a warm or hot surface to a cold or cooler surface. (Evaporators and condensers are heat exchangers.)
226
HEAT LAG
The time it takes for heat to travel through a substance heated on one side.
227
HEAT LEAKAGE
Flow of heat through a substance.
228
HEAT OF COMPRESSION
Mechanical energy of pressure changed into energy of heat.
229
HEAT OF CONDENSATION
The latent heat given up by a substance as it changes from a gas to a liquid.
230
HEAT OF FUSION
The latent heat absorbed when a substance changes from a solid state to a liquid state.
231
HEAT OF RESPIRATION
Process by which oxygen and carbohydrates are assimilated by a substance
232
HEAT OF VAPORIZATION
The latent heat absorbed by a substance as it changes from a liquid to a vapor.
233
HEAT PIPE
A refrigeration device with no moving parts, but containing a refrigerants.
234
HEAT PUMP
A device used to transfer heat from a low temperature to a high temperature medium also a reversed cycle in which work is the input and heat is rejected to a sink at a
235
HEAT PUMP
A refrigerating system employed to transfer heat into a space or substance. The condenser provides the heat while the evaporator is arranged to pick up heat from air,
236
HEAT SINK
Relatively cold surface capable of absorbing heat.
237
HEAT TRANSFER
Flow of heat by conduction, convection and radiation.
238
HEAT TRANSFER
Movement of heat from one body or substance to another. Heat may be transferred by radiation, conduction, convection or a combination of these three methods.
239
HEAT, SENSIBLE
Heat which is associated with a change in temperature
240
specific heat exchange of temperature
in contrast to a heat interchange in which a change of state (latent
241
Heat, Specific
The ratio of the quantity of heat required to raise the temperature of a given mass of any substance one degree to the quantity required to raise the temperature of an
242
Heat, Total (Enthalpy)
The sum of sensible heat and latent heat between an arbitrary datum point and the temperature and state under consideration.
243
HEAT
EXCHANGER MATERIALS
244
HEAT
TRANSFER MEDIUM
245
SURFACE
That surface which is exposed to the heating medium for absorption and transfer of heat to the medium.HENRY’S LAW
246
in a fluid based on temperature and partial pressure.HENRY
The unit of self
247
inductance or mutual inductance in the metric system. Its symbol is H.HERMETIC
Sealed so that the
248
object is gas tight.HERMETIC COMPRESSOR
Compressor which has the driving motor sealed inside the compressor housing. The motor operates in an atmosphere of the
249
refrigerant.HERMETIC MOTOR
Compressor drive motor sealed within same casing which contains compressor.HERMETIC SYSTEM
250
driven by a motor contained in compressor dome or housing.HERTZ
A unit in the metric system used to measure frequency in cycles per second. Its symbol is Hz.HIC
251
Hydrogen
induced cracking. (Same as hydrogen embrittlement)HIDDEN DEMAND CHARGE
252
demand charge. A low load factor for a building then penalizes the energy user through this "hidden" charge. HIDEOUT
Is the accumulation of chemicals on surfaces, in crevices or in
253
deposits within the system during normal operation.HIGH LIMIT CONTROL
A device which normally monitors the condition of the controlled medium and interrupts system operation
254
if the monitored condition be comes excessive, for example a high level of fluid in a storage tank.HIGH SIDE
Parts of the refrigerating system subjected to condenser pressure or higher
255
the system from the compression side of the compressor through the condenser to the expansion point of the evaporator. HIGH
PRESSURE CUT
256
OUT
Electrical control switch
257
operated by the high
side pressure which automatically opens electrical circuit if too high pressure is reached.HIGH
258
SIDE FLOAT
Refrigerant control mechanism which controls the
259
level of the liquid refrigerant in the high
pressure side of mechanism.HIGH
260
VACUUM PUMP
Mechanism which can create a vacuum in the 1000 to 1 micron range.HOT DECK
261
heating section of a multizone system. HOT GAS BYPASS
Piping system in refrigerating unit which moves hot refrigerant gas from condenser into low
262
DEFROST
Defrosting system in which hot refrigerant gas from the high side is directed through evaporator for short period of time and at predetermined intervals in order to remove
263
frost from evaporator.HOT JUNCTION
That part of thermoelectric circuit which releases heat.HOT PROCESS
264
temperature.HOT PROCESS PHOSPHATE SOFTENING
A process whereby the calcium and magnesium salts containing, constituting the hardness of water, are chemically
265
precipitated and removed with phosphate in conjunction with caustic soda.HOT WELL
A tank used to receive condensate from various sources on its passage back to the boiler
266
through a feedwater system.HOT
WATER HEATING BOILER
267
the boiler.HOT
WATER RE
268
CIRCULATING SYSTEM
A heating system using water as a heat
269
Hydrogen stress cracking.HSCC
Hydrogen
270
assisted stress
corrosion cracking.HUMIDIFIER
271
A device to add moisture to air. HUMIDIFYING
Adding of moisture to the
272
air.HUMIDIFYING EFFECT
The latent heat of vaporization of water at the average evaporating temperature times the weight of water evaporated per unit of time. HUMIDISTAT
273
HUMIDITY
Dampness of air.
274
HUMIDITY RATIO
The ratio of the mass of the water vapor to the mass of dry air contained in the sample.
275
HUMIDITY, ABSOLUTE
The weight of water vapor per unit volume.
276
HUMIDITY, PERCENTAGE
The ratio of the specific humidity.
277
HUMIDITY, RELATIVE
The ratio of the mol fraction of water vapor present in the air, to the mol fraction of water vapor present in saturated air at the same temperature and barometric
278
pressure
approximately, it equals the ratio of the partial pressure or density of the water vapor in the air, to the saturation pressure or density, respectively, of water vapor at the same
279
HUNTING
A surge of engine speed to higher number of revolutions per minute, followed by a drop to normal engines speed without manual movement of the trottle. Is often caused by
280
HVAC
Heating, Ventilating, and Air Conditioning.
281
HVAC BOILER
Boiler for heating or air conditioning (Absorption Refrigeration)
282
HVAC EQUIPMENT
Apparatus or equipment used in heating, ventilating, and air conditioning.
283
HYDRATION
Absorption of water by a mineral that results in a change in the nature of the mineral.
284
HYDRAULIC CLASIFICATION
The rearrangement of resin particles in an ion
