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TAlL PIPE - Outlet pipe from the evaporator.

TANDEM COMPOUND TURBINE -  turbines are large turbines consisting of two or more turbines in series coupled together as one shaft and applied to one generator

TANNINS - A chemical used as an inhibitor in relation with caustic embrittlement.

TEMPERATURE - Degree of hotness or coldness as measured by a thermometer.

TEMPERATURE CONTROL - Temperature-operated thermostatic device which automatically opens or closes a circuit.

TEMPERATURE CRITICAL - The saturation temperature corresponding to the critical state of the substance at which the properties of the liquid and vapor are identical.

Temperature, Absolute Zero: The zero point on the absolute temperature scale, 459.69 degrees below the zero of the Fahrenheit scale, 273.16 degrees be low the zero of the Celsius scale.

TEMPERATURE, DEWPOINT - The temperature at which the condensation of water vapor in a space begins for a given state of humidity and pressure as the temperature of the vapor is reduced. The temperature corresponding to saturation (100 percent relative humidity) for a given absolute humidity at constant pressure.

TEMPERATURE, DRYBULB - The temperature of a gas or mixture of gases indicated by an accurate thermometer after correction for radiation.

TEMPERATURE, EFFECTIVE - An arbitrary index which combines into a single value the effect of temperature, humidity, and air movement on the sensation of warmth or cold felt by the human body. The numerical value is that of the temperature of still, saturated air which would induce an identical sensation.

TEMPERATURE, SATURATION - The temperature at which no further moisture can be added to the air water vapor mixture. Equals dew point temperature.

TEMPERATURE, WET BULB - Thermodynamic wet bulb temperature is the temperature at which liquid or solid water, by evaporating into air, can bring the air to saturation adiabatically at the same temperature. Wet bulb temperature (without qualification) is the temperature indicated by a wet bulb psychrometer constructed and used according to specifications.

TEMPERATURE-HUMIDITY INDEX - Actual temperature and humidity of air sample compared to air at standard conditions.

TENSILE STRENGTH - In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength.

TENSILE STRESS - A stress that causes two parts of an elastic body, on either side of a typical stress plane, to pull apart.

TENSION - The force or load that produces elongation.

TERMINAL VELOCITY - The maximum air stream velocity at the end of the throw.

THE FIRST LAW - (1 ) When work is expanded in generating heat, the quantity of heat produced is proportional to the work expended; and, conversely, when heat is employed in the performance of work, the quantity of heat which disappears is proportional to the work done (Joule); (2) If a system is caused to change from an initial state to a final state by adiabatic means only, the work done is the same for all adiabatic paths connecting the two states (Zemansky); (3) In any power cycle or refrigeration cycle, the net heat absorbed by the working substance is exactly equal to the net work done.

The Second Law: (1) It is impossible for a self acting machine, unaided by any external agency, to convey heat from a body of lower temperature to one of higher temperature (Clausius); (2) It is impossible to derive mechanical work from heat taken from a body unless there is available a body of lower temperature into which the residue not so

Therm - Measurement used by gas utilities for billin3 purposes. 1 Therm = 100 cubic feet of gas = 100,000 Btu.

THERM - Quantity of heat equal to 100000 Btu.

THERMAL CONDUCTIVITY - The rate at which heat is transferred through an object.


THERMAL CONDUCTIVITY - The rate of heat flow, under steady conditions, through unit area, per unit temperature gradient in the direction perpendicular to the area. It is given in the SI nits s watts per meter Kelvin (W/m K).

THERMAL EFFICIENCY - Ratio of shaft work out of a system to the heat energy into the system.

THERMAL EFFICIENCY OF A GAS TURBINE - Is the energy output of the gas turbine divided by the energy input of the gas turbine.

THERMAL ELECTROMOTIVE FORCE - The electromotive force generated in a circuit containing two dissimilar metals when one junction is at temperature different from that of the other. (see also thermocouple).

THERMAL EQUILIBRIUM - When two bodies originally at different temperatures, have attained the same temperature

THERMAL EXPANSION - The change in length of a material with change in temperature.

Thermal Expansion Valve: The metering device or flow control which regulates the amount of liquid refrigerant which is allowed to enter the evaporator.

THERMAL SHOCK - The development of a steep temperature gradient and accompanying high stress within a material or structure.

THERMAL TREATMENT - Refers to the treatment of water with heat to drive off the dissolved gases and soften certain minerals for easy removal.

THERMISTOR - A two-terminal semiconductor device whose resistance is temperature sensitive.

THERMOBANK - A bank for storing heat.

THERMOCOUPLE - Device for measuring temperature utilizing the fact that an electromotive force is generated whenever two junctions of two dissimilar metals in an electric circuit are at different temperature levels.

THERMOCOUPLE - Device which generates electricity, using the principle that if two unlike metals are welded together and junction is heated, voltage will develop across the open ends.

THERMOCOUPLE - Device which generates electricity, using the principle that if two unlike metals are welded together and junction is heated, voltage will develop across the open ends.

THERMOCOUPLE THERMOMETER - Electrical instrument using thermocouple as source of electrical flow, connected to millimeter calibrated in temperature degrees.

THERMODISK DEFROST CONTROL - Electrical switch with bimetal disk controlled by temperature changes.


THERMODYNAMIC PROPERTIES - Basic qualities used in defining the condition of a substance, such as temperature, pressure, volume, enthalpy, entropy.




THERMODYNAMICS - Part of science which deals with the relationships between heat and mechanical action.

THERMOELECTRIC REFRIGERATION - Where refrigeration is produced by the passage of electric current through two dissimilar materials.

THERMOELECTRICITY - In physics, electricity generated by the application of heat to the junction of two dissimilar materials. If two wires of different materials are joined at their ends and one end is maintained at a higher temperature than the other, a voltage difference will arise, and an electric current will exist between the hot and the cold junctions.

THERMOMETER - Device for measuring temperatures.

THERMOMODULE - Number of thermocouples used in parallel to achieve low temperatures.

THERMOPILE - Number of thermocouples used in series to create a higher voltage.

THERMOSTAT - Device, which senses ambient temperature, conditions and, in turn, acts to control a circuit.

THERMOSTATIC CONTROL - Device which operates system or part of system based on temperature change.

THERMOSTATIC VALVE - Valve controlled by temperature change response elements.

THERMOSTATIC WATER VALVE - Valve used to control flow of water through system, actuated (made to work) by temperature difference. Used in units such as water-cooled compressor and/or condenser.

THREE-WAY VALVE - Multi-orifice (opening) flow control valve with three fluid flow openings.

THRESHOLD TREATMENT - Chemical treatment, used to prevent scale formation, which acts to hold hardness in solution at the threshold of precipitation.

THROTTLE GOVERNING - With throttle governing a single large control valve controls the load from 0% to 100%When steam is throttled, the superheat increases and the turbine exhaust steam is drier, reducing the turbine blade erosion, but with the drier steam entering the condenser, the condenser losses increase. Throttling of steam through a valve is an isenthalpic ( constant enthalpy ) process and no heat is lost. The so-called throttling losses occur in the condenser.

THROTTLING - An irreversible adiabatic steady flow process in which the fluid is caused to flow through an obstruction in a pipe with a resulting drop in pressure.

THROTTLING RANGE - The amount of change in the variable being controlled to make the controlled device more through the full length of its stroke.

THRUST COLLAR POSITION INDICATOR -  The axial position of the rotor is very important and an axial position indicator is often applied to the thrust bearing.

It may be a large dial micrometer with alarm setting for an axial movement of 0.4 millimeter and shutdown at 0.8 millimeter, or An oil pressure gauge connected to an oil leak-off device may also be used as an axial position indicator. The oil is supplied at say 500 kPa, flows through an orifice and leaks off through a nozzle. The pressure between the orifice and nozzle depends on the distance between the nozzle and shaft thrust collar; the larger the distance the lower the pressure. The pressure gauge can be calibrated in millimeter clearance and may have alarm and shutdown settings

TIMER-THERMOSTAT - Thermostat control which includes a clock mechanism. Unit automatically controls room temperature and changes temperature range depending on time of day.



TITRATION - A chemical process used in analyzing feed water.

TON REFRIGERATION UNIT - Unit which removes same amount of heat in 24 hours as melting of 1 ton of ice.

TON'S OF REFRIGERATION - The capacity of a refrigeration system that can freeze 1 ton (1000 kg) of liquid water at 0C into ice at 0C in 24 hour is said to be 1 tone.

TOOL STEEL - Any steel used o make tools for cutting, forming, or otherwise shaping a material into a final part.

TOPPING TURBINE -  Have been used when old boilers are replaced with new high pressure boilers. The turbine is a backpressure turbine exhausting to the old boiler header still supplying steam to the old lower pressure turbines.

TOTAL DYNAMIC HEAD - Dynamic discharge head (static discharge head, plus friction head, plus velocity head) plus dynamic suction lift, or dynamic discharge head minus dynamic suction head.

TOTAL HARDNESS - See Hardness.

TOTAL HEAT - Sum of both the sensible and latent heat.

TOTAL HEAT (ENTHALPY) - Total heat is the sum of the sensible heat and latent heat in an exchange process. In many cases, the addition or subtraction of latent and sensible heat at terminal coils appears simultaneously. Total heat also is called enthalpy, both of which can be defined as the quantity of heat energy contained in that substance.

TOTAL SOLIDS - Are the sum of the dissolved and suspended solids.

TOWER FILL - The interior structure of a cooling tower over which the water flows.

TRACE CONSTITUENTS - Materials present at a concentration less than 0.01 mg/L.

TRANSMITTANCE, THERMAL (U FACTOR) - The time rate of heat flow per unit area under steady conditions from the fluid on the warm side of a barrier to the fluid on the cold side, per unit temperature difference between the two fluids.

TRANSDUCER - The means by which the controller converts the signal from the sensing device into the means necessary to have the appropriate effect on the controlled device. For example, a change in air pressure in the pneumatic transmission piping.

TRANSFORMER - The system power supplying transformer is an inductive stationary device which transfers electrical energy from one circuit to another. The transformer has two windings, primary and secondary. A changing voltage applied to one of these, usually the primary, induces a current to flow in the other winding. A coupling transformer transfers energy at the same voltage; a step-down transformer transfers energy at a lower voltage, and a step-up transformer transfers energy at a higher voltage.

TRANSIENT CONSTITUENTS - Are those constituents which change in concentration or activity by changes in the aquatic environment. The change my be due to oxidation potentials, biological activities, etc..

TRANSISTOR - An active semiconductor device capable of providing power amplification and having three or more terminals.

TREATMENT - A process whereby impurities are removed from water; also a substance added to water to improve its physical or chemical properties.

TRIBOLOGY - The science concerned with the design, friction, lubrication and wear of contacting surfaces that move relative to each other (as in bearings, cams, or gears).

TUBE SHEET - The portion of a heat exchanger or boiler in to which the tubes are rolled or secured.

TUBERCLE - A protective crust of corrosion products (rust) which builds up over a pit caused by the loss of metal due to corrosion.

TUBERCULATION - A corrosion process that produces hard knob-like mounds of corrosive products on metal surfaces, increasing friction and reducing flow in a water distribution system.

TUBE-WITHIN-A-TUBE - Water-cooled condensing unit in which a small tube is placed inside large unit. Refrigerant passes through outer tube, water through the inner tube.

TURBIDITY - The measure of suspended matter in, a water sample which contributes to the reflection of light or cloudiness.

TURBIDITY UNIT - The unit of measure of suspended matter in water. It is the measure of light compared against light reflected by a reference standard as defined by the standard methods of water analysis in, APHA.

TURBINE METER - A device used to measure water consumption in industrial plants.

TURBINE ROTOR - The rotating assembly enclosed within the turbine casing

TURNER GAUGE - A device used to measure the actual scale-thickness in boiler tubes.

TWO-TEMPERATURE VALVE - Pressure-opened valve used in suction line on multiple refrigerator installations, which maintains evaporators in a system at different temperatures.

TWO-WAY VALVE - Valve with one inlet port and one outlet port.

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Table of contents Power Plant Dictionary