Select a letter to view associated terms and definitions.

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z 
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Absolute Humidity: Ratio of the mass of gases: water vapor to non-condensable gases.
Adiabatic Process: A process where Heat is NOT transferred across system boundaries.
For example: Consider a well-insulated duct as a system boundary. Inside cool water is mixed with hot, dry air. The air and water temperatures come to thermal equilibrium as they mix (some water would vaporize and the air would cool.) This process would be defined as adiabatic.
- B - Top of Page
Boiler: A mechanical steam generator that transfers Heat Energy from fuel to water, changing the water’s Enthalpy and phase from liquid to gas.
Boiler Feedwater: Boiler Feed-water is converted from Boiler Makeup Water as it passes through the De-aerating Heater. Water is sprayed into a steam-heated vessel to strip away dissolved gases from the water.
Boiler Flue Gas: Exhaust generated from a Boiler combustion chamber. This stream is commonly kept at an elevated Temperature to avoid condensing in the flue stack.
Boiler Makeup Water: Filtered water that has been and softened by ion-exchange (replacing Mg++, Ca++, or Fe++ with Na+). With high pressure boilers (pressures above 300 psig), hydrogen (H+) and hydroxide (OH-) are substituted.
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Combustion: The chemical process of rapid oxidation of a fuel producing heat. The fuel is usually a hydrocarbon and the oxidizer is usually air.
Combustion Efficiency: A measure of the percent of oxidation of the fuel. For example, when carbon is burned and produces only carbon dioxide (CO2,) it is fully oxidized and combustion efficiency is 100%. If no carbon is oxidized the efficiency is 0%. If only carbon monoxide (CO) is produced, then efficiency is 50%.
Condensate Return: The amount of condensed steam returned from use point and used as Boiler Feedwater. Boiler Makeup Water is added to system to take place of any steam or condensate losses.
Condensing Economizer: A heat exchanger that transfers heat from a Boiler Flue Gas to Boiler Makeup Water. Two types or heat exchangers are Direct and Indirect-Contact.
Cost-Savings: Recaptured heat returned to the process must have an economical benefit that can be quantified and verifiable to be classified as “savings”. Displacing Virgin Energy is a straightforward method of claiming savings.
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Deaerating Heater: Mechanical devices that liberate gases (air, oxygen (O2), carbon dioxide (CO2)or other gases) from Boiler Makeup Water; also referred to as Deaerators.
Direct Contact Heat Transfer: A literal description of what happens when two streams are mixed together to transfer Heat and then separated. Direct Contact Heat Transfer requires mostly immiscible fluids (e.g. – 2 phase gas-liquid mixture). Miscible fluids cannot be separated. Minor portions of the two streams may be miscible and are transferred with the Heat.
- E - Top of Page
Economizer: A heat exchanger that transfers heat from a Boiler Flue Gas to Boiler Feedwater.
Energy: Energy is the capacity to do Work. Both Work and Heat have the units of Work (ft-lbf, Btu, calories, kW-hour, etc.)
Engine: A machine that converts Energy to mechanical Work. There are no machines that can convert 100% of the energy to work.
Enthalpy: A thermodynamic property of a substance representing the sum of Energy contained in that substance, including sensible and latent heat.
Excess Air: Air in excess of the amount required for complete combustion.
- F - Top of Page
Force: A pull or a push. The term implies that resistance to movement is being encountered [engineering units: N, lbf, dyne, etc. One lbf = the force which will impart an acceleration of 32.174 feet per sec per sec to a 1-lb mass].
- H - Top of Page
Heat: Energy associated with molecular movement, vibrations, or radiation. Energy in one material transfers to other material by conduction, convection, and radiation. Heat can never be completely converted into Work.
Heat Capacity: The quantity of Energy required to raise a specific amount of material one degree of Temperature without a changing its phase, either at constant pressure or volume [engineering unit: ft2/sec 2-oF, J/g-oK, etc.]
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Indirect Contact: A device used to transfer Heat between two substances (or mixtures) while keeping the materials separate.
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Latent Heat: Heat energy associated with a material’s change of phase (solid to liquid, liquid to gas and solid to gas, or vice-versa,) but no temperature change.
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Mass: A thermodynamic property of a substance representing the sum of atomic material contained in a substance
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Non-Condensable: Gas that will not condense within the system Temperature range.
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Power: The rate of Work performed [engineering unit: lb-ft2/sec3, J/sec, Watt, etc.]
Phase: The state of a material: solid, liquid or gas
- R - Top of Page
Recovered Heat: Heat formerly wasted that is captured and recycled to the system.
Relative Humidity: The ratio of Absolute Humidity to Saturated Humidity at the gas Temperature.
- S - Top of Page
Saturated Air: Describes state at which air containing water vapor will not hold any more water vapor at a particular Temperature and pressure.
Saturated Humidity: The ratio of the partial pressure of water vapor to that of the bone-dry gas that is saturated with the water vapor.
Sensible Heat: Heat added to a material raising its Temperature.
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Temperature: The measure of the relative internal Energy of a material or system. A physical property, which determines the direction of flow of Heat between materials in thermal contact; Heat flows from the higher Temperature material to the lower Temperature material.
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Virgin Energy: Energy that is metered as it is delivered to a process (e.g., natural gas, tons of coal, electric power, etc.)
- W - Top of Page
Waste Heat: Heat that escapes from a system.
Water of Combustion: Water formed when a hydrocarbon fuel is burned in air or oxygen; For the general combustion of a hydrocarbon: CxHy + (x+y/2)·O2 --> xCO2) + (y/2)·H2O, water is formed. This water is not generally considered as a source.
Work: Work (W) is a form of Energy and is defined as the product of a Force acting through a distance in the direction of that Force [engineering unit: ft-lbf, Joules, Btu, calories, etc.]. Work can be totally converted to Heat.