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Table of contents Power Plant Dictionary


ECONOMIZER - A series of tubes located in the path of flue gases. Feed water is pumped through these tubes on its way to the boiler in order to absorb waste heat from the flue gas.

EDDY CURRENT TESTING - An electromagnetic nondestructive testing method in which eddy-current flow is induced in the test object. Changes in flow caused by variations in the object are deflected into a nearby coil or coils where they are measured.

EDDY CURRENTS (ELECTRICITY) -  An electromagnetic nondestructive testing method in which eddy-current flow is induced in the test object. Changes in flow caused by variations in the object are deflected into a nearby coil or coils where they are measured.

EDDY CURRENTS (STEAM TURBINES) -  Impulse Turbine - As the steam passes through convergent nozzles, if the exit pressure is less than 0.577 x inlet pressure (the critical pressure for nozzles), eddy-currents are developed and the exit velocity will be less than calculated.

EDTA - A chelating agent used with boiler water treatment. Often referred as the replacement for the phosphate-hydroxide treatment method.

EFFECTIVE TEMPERATURE - Overall effect on a human of air temperature, humidity and air movement.

EFFLUENT - The solution which emerges from an ion-exchange column.



ELECTRIC DEFROSTING - Use of electric resistance heating coils to melt ice and frost off evaporators during defrosting.

ELECTRICAL CIRCUIT - A power supply, a load, and a path for current flow are the minimum requirements for an electrical circuit.

ELECTROCHEMICAL REACTIONS - A metal wasting process, due to the fluid (boiler water) being subjected to an electrical current.

ELECTRODE BOILER - 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 heat by its resistance to electric current.

ELECTRO DIALYSIS - This is a membrane process where an applied electric charge draws impurity ions through permeable membranes to create high purity feed water streams or low purity waste streams.

ELECTROLYSIS - Chemical decomposition caused by action of an electric current in a solution.

ELECTROLYTE - A chemical compound which dissociates or ionizes in water to produce a solution which will conduct an electric current; an acid, base, or salt.

ELECTROMECHANICAL - Converting electrical input into mechanical action. A relay is an electromechanical switch.

ELECTRO REGENERATION - Hydrogen and hydroxyl ions are formed be electrical splitting of water molecules and are swept through the unit by steady, low-voltage direct current, continuously cleansing the resin beads and carrying away the unwanted salts

ELEMENT - A pure substance that cannot be broken down by chemical means to a simpler substance.

ELEVATION HEAD - The energy possessed per unit weight of a fluid because of its elevation.

ELUTION - The stripping of adsorbed ions from an ion-exchange material by the use of solutions containing other ions in concentrations higher than those of the ions to be stripped.

Emissions: The gases and airborne particles produced during Combustion.

EMULSION - A colloidal dispersion of one liquid in another.

ENDOTHERMIC REACTION - Pertaining to a chemical reaction which is accompanied by an absorption of heat.

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 transferred from one form to another. Energy can also exist in one of two states, either potential or kinetic.

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 costs, and part of the amortization of the utility's equipment.

Energy = power x time

( 1 ) Expressed in kilowatt-hours (kWh) or watt hours (Wh), and is equal to the product of power and time.
( 2 ) 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 transferred from one form to another. Energy can also exist in one of two states, either potential or kinetic.

ENGINE - Prime mover; device for transforming fuel or heat energy into mechanical energy.

ENGINE OIL - An oil used to lubricate an internal combustion engine.

ENTHALPY - The total quantity of heat energy contained in a substance, also called total heat; the thermodynamic property of a substance defined as the sum of its internal energy plus the quantity Pv/J, where P = pressure of the substance, v = its volume, and J = the mechanical equivalent of heat.

ENTRAINMENT - The transport of water into a gas stream. In a boiler, this is carryover, in a cooling tower, drift.

ENTRAINMENT (HVAC) - The capture of part of the surrounding air by the air stream discharged from an outlet (some times called secondary air motion).

ENTROPY - A thermodynamic measure of the amount of energy unavailable for useful work in a system undergoing change.  The ratio of the heat added to a substance to the absolute temperature at which it is added.

 Entropy and Information (Progress in Mathematical Physics)

ENVIRONMENT - The aggregate of all conditions (such as contamination, temperature, humidity, radiation, magnetic and electric fields, shock, vibration) that externally influence the performance of a material or component.

EPSON SALT - Magnesium sulfate.

EQUALIZING HOLE (STEAM TURBINE) - A hole in the turbine disc designed to equalize axial thrust with impulse bladed turbines.

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 reached in which both reactants and pacts are present in definite ratios.

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 given ion in terms of its calcium carbonate.

EROSION , ABRASIVE - Erosive wear caused by relative motion of solid particles which are present in fluids and are moving parallel to a solid surface.

EROSION, CAVITATIONS - Progressive loss of original material from a solid surface due to continuing exposure to cavitation.

EROSION, IMPINGEMENT - Loss of material from a solid surface due to liquid impingement.

EROSION, LIQUID - Removal of films or metal by mechanical action and corrosion of active metal.

EROSION-CORROSION - A conjoint action involving corrosion and erosion in the presence of a moving corrosive fluid, leading to the accelerated loss of material.

ETHANE (R-170) - Refrigerant sometimes added to other refrigerants to improve oil circulation.


EUTECTIC - An isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids on cooling.

EUTECTIC POINT - Freezing temperature for eutectic solutions.

EVACUATION - The removal of gases from a system.

EVAPORATION - The change of state from liquid to vapor, for example as water evaporates to a vapor in a cooling tower.

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.

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 consumption.

EVAPORATIVE COOLING - The adiabatic exchange of heat between air and a water spray or wetted surface. The water approaches the wet-bulb temperature of the air, which remains constant during its traverse of the exchanger.

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 refrigerant boils into a gas in the process of the heat absorption.

EVAPORATOR FAN - Fan which increases airflow over the heat exchange surface of evaporators.

EVAPORATOR PRESSURE REGULATOR - Automatic pressure regulating valve mounted in suction line between evaporator outlet and compressor inlet. Its purpose is to maintain a predetermined pressure and temperature in the evaporator.

EVAPORATOR, FLOODED - Evaporator containing liquid refrigerant at all times.

EXFlLTRATION - The flow of air outward from a space through walls, leaks, etc.

EXFOLIATION - Scaling off of a surface in flakes or layers as the result of corrosion.

EXHAUSTION - The state in which the adsorbent is no longer capable of useful ion exchange; the depletion of the exchanger's supply of available ions. The exhaustion point is 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 which measures the resistance of the water to the flow of an electric current.

EXOTHERMIC - Chemical reaction in which heat is released.

EXPANSION JOINT - Device in piping designed to allow movement of the pipe caused by the pipe's expansion and contraction.

EXPANSION TANK - A reservoir usually above a closed re-circulating water system that is blanketed with a gas to permit expansion and contraction of water in the system during temperature changes.

EXPANSION VALVE - Device in refrigerating system which reduces the pressure from the high side to the low side and is operated by pressure.

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 transmit pressure from the sensitive bulb of some temperature controls to the operating element.

EXPANSION VALVE, THERMOSTATIC - Control valve operated by temperature and pressure within evaporator. It controls flow of refrigerant. Control bulb is attached to outlet of evaporator.

EXPENDABLE REFRIGERANT SYSTEM - System, which discards the refrigerant after it has evaporated.

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.

EXTERNAL EQUALIZER - Tube connected to low-pressure side of a thermostatic expansion valve diaphragm and to exit end of evaporator.

EXTERNAL TREATMENT - Refers to the treatment of water before it enters the boiler.

EXTRACTION TURBINE are turbines where steam is extracted at one or more points at constant pressure. Extraction turbines may be single or double-extraction-condensing turbines or single-or double-extraction back-pressure turbines.  The extracted steam is used for process.  Do not call these bleed turbines where steam is used for heating feed water.

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Table of contents Power Plant Dictionary