ASHRAE Terminology

accessories intended to permit access into ducts, they are positioned in proximity to all those internal parts which require inspection and/or maintenance, such as fire dampers.

ductwork for which, in all frequency bands of interest, the breakout sound level is at least 10 dB less than the transmitted sound level of the terminal unit under test.

(1) characteristics of a room that determine the qualities of sound therein, relative to hearing. (2) science of the production, transmission, and effects of sound.

the product of the voltage across a branch of an alternating current circuit and the component of the electric current that is in phase with the voltage.

land that is, or was within ten years prior to the date of the building permit application for the building project, primarily devoted to the commercial production of horticultural, viticultural, floricultural, dairy, apiary, vegetable, or animal products

condition where the introduction of air causes either a flow restriction or a malfunction of the system.

(1) distribution of the air in a space, called the treated space, in a manner to satisfy certain specified conditions such as air change rate, pressure, cleanliness, temperature, humidity, air velocity, and noise level, in a specified zone within this treated space, which is called the occupied zone. It is usually achieved by means of air terminal devices which form the common boundaries between the treated space and the air-distribution system. (2) the introduction of air into a building space for the purpose of providing acceptable velocity and temperature distribution in the occupied zone.

transportation of a specified airflow to or from the treated space, by ducts or plenums. Air-treatment devices can be added to the distribution system for the purpose of treating the air (e.g., cleaning, heating, cooling, humidifying or dehumidifying, etc.)

there are three main categories of components: elements of distribution (components for the purpose of ensuring a correct distribution of the air), air terminal units (ATUs) [equipment inserted into or added to the ends of ducts for the purpose of controlling one or more of various parameters such as velocity, pressure, flow rate, and temperature (also see air terminal unit)], and accessories of distribution (components ensuring the fitting and fixing in place of the elements of distribution and their inspection and maintenance).

a tube or conduit used for conveying air. The air passages of self-contained systems are not air ducts.

duct and dampers arrangement with an automatic control system that together allow a cooling system to supply outdoor air to reduce or eliminate the need for mechanical cooling during mild or cold weather.

an assembly that hangs above the stove or cooktop in the kitchen and contains a skirt or capture panel to contain the rising gases or effluent plume, one or more grease filters, and a fan or tangential blower for forced ventilation used to remove airborne grease, combustion products, smoke, odors, heat, and steam from the air by a combination of filtration and evacuation of the air outside of the building. Air extraction cooker hoods may be ducted (or vented) application, or ductless (or recirculating) application. Ductless or recirculating hoods use particulate and gaseous filtration (activated charcoal) to clean the air to an acceptable quality for returning to the room. Hoods may include lighting. See also cooker hood, Hood, Type I Hood, Type II Hood.

1) the flow of air through the building envelope caused by a specified pressure difference, a measure of airtightness, cfm at fixed pressure (m3/s at fixed pressure). 2) undesirable or unwanted leakage of air from within a component within an air-distribution system that could include such items as ducts, air terminal devices, and AHUs.

blade or blades fitted across an air duct to divide the airstream into a number of streams in parallel. Should not be used in current engineering practice due to excessive pressure drop and noise considerations.

(1) an air-distribution assembly consisting of inlet duct connection(s) and outlet duct connection(s) whose purpose fulfills (either manually or automatically) one or more of the following functions: controls the rate of the airflow, controls the velocity or pressure and/or temperature of the air, mixes primary streams of different temperatures or humidities, or mixes within the device primary air with air from the treated space. (2) an air terminal unit may be composed of automatic or manual dampers, filters valves, heating or cooling coils, sound attenuation, nozzles, or fan assemblies. See also diffuser terminal.

(1) movement of air usually within boundaries (such as ducts). (2) the volume of air per unit time.

(1) circuit used to increase the power, voltage, and/or current level of a signal. (2) device that enables an input signal to control power from a source independent of the signal and thus be capable of delivering an output that bears some relationship to, and is generally greater than, the input signal. (3) device whose output is an enlarged reproduction of the essential features of an input signal and that draws power from a source other than the input signal.

device placed at the end of a test duct to prevent excessive reflection of the sound waves back into the test duct where they would interfere with the waves to be measured.

(1) process involving controlled heating and subsequent controlled, generally slow, cooling. Applied usually to induce ductility in metals. (2) treatment intended to remove internal stresses, alter mechanical or physical properties, produce a definite microstructure, and remove gases.

product of the volts and amperes of a circuit. This product generally is divided by 1000 and designated in kilovolt-amperes (kVA). It comprises both real and reactive power.

measured property of a material or assembly of materials, heat flows by a combination of conduction, convection, radiation, and latent heat exchange and may depend on orientation, direction, or both. The specific test conditions (i.e., sample thickness, orientation, environment, environmental pressure, surface temperature, mean temperature, temperature difference, and moisture distribution) should be reported with the values. The symbol K is used to denote the lack of pure conduction or to indicate that all values reported are apparent. Materials with a low apparent thermal conductivity are called insulation materials.

an established and recognized agency regularly engaged in conducting tests or furnishing commissioning services, where such agency has been approved.

(1) in any rectangular configuration, the ratio of the longer dimension to the shorter. (2) ratio of the length to width of a rectangular air duct.

production of movement in a fluid by suction created by fluid velocity. See also Venturi.

portion of an envelope component represented by an arrangement and connection of building construction materials with a specific thermal transmittance or thermal conductance.

a test conducted according to an ASTM International standard test procedure.

introduction of cool, outdoor air into an attic by exhausting its warm air to the outdoors.

device which, when mounted in a duct or opening, permits the flow of air in one direction only. Can be gravity (counter weighted) or power operated.

assembly to measure and control fluid flow, composed of a measuring device, a volume control device, and recommended lengths of straight ductwork or pipe leading into and out of the measuring device.

a document that records the concepts, calculations, decisions, and product selections used to meet the Owner’s Project Requirements and to satisfy applicable regulatory requirements, standards, and guidelines. The document includes both narrative descriptions and lists of individual items that support the design process.

tubeaxial (ducted) fan whose motor is mounted outside a bifurcated (divided) duct with only the blades of the fan located in the airstream.

water-formed deposits of biological organisms or the products of their life processes. Biological deposits include barnacles, algae, or slimes.

chamber in which cold air is circulated rapidly around products to be frozen so that freezing occurs rapidly enough to avoid formation of large ice crystals which may damage the product.

heavy duty duct closure device.

a ducted centrifugal fan used in a heating, ventilating, and air-conditioning system. See also centrifugal fan, fan.

surfaces of the boiler that are exposed to the products of combustion on one side and water on the other, expressed in area units (of the side receiving the heat).

sheet metal transformation piece used to make connection between round and rectangular ductwork.

product of the volume of a gas times its pressure is a constant at fixed temperature. Also known as Mariotte’s law.

(1) in ducts, piping, or conduit, another section of the same size or smaller, at an angle with the main. (2) section of pipe or duct from a main to a terminal device.

the circuit conductors between the final overcurrent device protecting the circuit and the outlet(s). The final wiring run to the load.

the connection to any fuel-fired equipment, device, or appliance and the horizontal section of the exhaust system used for conducting the products of combustion from a fuel-fired equipment, device, or appliance to the vertical section, which is identified as the vent, chimney, or flue.

(1) damper consisting of a plate turning on a diametral axis inside a duct. (2) pair of flaps hinged to a common diametrical spindle and permitting flow in one direction only. (3) two flaps in \"V\" arrangement.

a pipe or duct, usually controlled by valve or damper, for conveying a fluid around an element of a system.

(thermal conductance), time rate of steady-state heat flow through unit area of a material or construction, induced by a unit temperature difference between the body surfaces. Units of C are Btu/h·ft² or °FW/m²·K. Note that the C-factor does not include soil or air films.

(1) measure of the maximum amount of energy or material that may be stored in a given system. See also nameplate rating, air-conditioner capacity. (2) the rate of heat removal by the refrigerant used in the compressor or condensing unit in a refrigerating system. This rate equals the product of the refrigerant mass flow rate and the difference in the specific enthalpies of the refrigerant vapor at its thermodynamic state entering the compressor or condensing unit and refrigerant liquid at the thermodynamic state entering the mass flow control device. (3) the rate that heat is removed or added to a system. (4) maximum load for which a machine, apparatus, device, or system is designed or constructed.

A naturally occurring gas, CO₂ is also a by-product of burning fossil fuels (such as oil, gas, and coal), burning biomass, land-use changes (LUC), and industrial processes (e.g., cement production). It is the principal anthropogenic greenhouse gas (GHG) that affects the Earth’s radiative balance. It is the reference gas against which other GHGs are measured and therefore has a global warming potential (GWP) of 1.

Anthropogenic activities removing CO2 from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products

negative electrode in an electrolytic system at which reduction occurs (e.g., Fe++, Cu++, Ca++, Mg++). Compare to anode.

nonducted IDUs intended to be installed flush mounted with the ceiling. These IDUs can have configurations of indoor airflow coming from one, two, or four directions, or from a circular direction.

insulation composed principally of the catalyzed reaction product of polyisicyanate and polyhydroxy compounds, usually processed with fluorocarbon gas to form a rigid foam having a predominately closed-cell structure.

in-line duct fan with centrifugal blades which can develop static pressures higher than normal duct fans. Also identified as a tubular centrifugal fan.

process in which a liquid product is vacuum frozen while being centrifuged in order to avoid foaming.

materials corrosive or in-themselves toxic or productive of poisonous gases or fluids. Flammable or explosive materials easily ignited, including materials known to be fire producers or explosives.

to apply refrigeration moderately to products without freezing them.

rising of air or gas in a duct or other vertical passage, like a building, caused by lowered density air at the top of the passage.

free flow propeller fan designed to circulate the air in a room without any air duct.

(1) short section of rolled steel angle used to connect two intersecting steel members. (2) strip of sheet formed by roll forming into a profile that is used to secure the sheet metal rolled jointing flanges added to rectangular ducts.

specially constructed single or multiconductor cable which provides shielding from electrostatic fields.

a coefficient is a factor in a mathematical product.

sequential production of either electrical or mechanical power and useful thermal energy (heating or cooling) from a single energy form.

product of the height and length of the coil finned area.

series of actions and equipment applied to maintain a product within a specified low-temperature range from harvest/production to consumption.

Combined heat and power (CHP), also known as cogeneration, is the simultaneous production of electricity and heat from a single fuel source, such as natural gas, biomass, biogas, coal, waste heat, or oil. (http://www.epa.gov/chp/basic/index.html).

when gases take part in chemical reactions, the volume of the reacting gases and those of the products (if gaseous) are in the ratio of small whole numbers, provided that all measurements are made at the same temperature and pressure. Also known as Gay-Lussac's law.

sampling of combustion products to determine the percentage of constituents and their temperature.

effluents from the combustion of a fuel, including the inerts but excluding excess air.

(1) design maximum rate of heat removal by the refrigerant assigned to the compressor in a refrigerating system. This is equal to the product of the mass rate of refrigerant flow produced by the compressor and the difference in specific enthalpies of the refrigerant vapor at its thermodynamic state entering the compressor and the refrigerant liquid at saturation temperature corresponding to the pressure of the vapor leaving the compressor. (2) device, such as a clearance pocket, movable cylinder head, or suction bypass, by which compressor capacity can be adjusted without otherwise changing the operating conditions.

rate of heat removal by the refrigerant assigned to the compressor in a refrigerating system. This is equal to the product of the mass rate of refrigerant flow produced by the compressor and the difference in specific enthalpies of the refrigerant vapor at its thermodynamic state entering the compressor and refrigerant liquid at saturation temperature corresponding to the pressure of the vapor leaving the compressor.

system in which a computer directs the manufacture and assembly of a product.

installation of an air--terminal device where the attachment to the duct, wall, or ceiling is hidden from view to room occupants.

for water-cooled condensers, the amount of heat added to the water removed from the load, the integrated product of the flow rate through the condenser and the temperature difference across the condenser.

one that circulates the products of combustion and extracts available heat to a point that causes condensation to occur. Some of this latent heat of condensation is recovered as usable energy, resulting in higher operating efficiency.

(1) portion of the total refrigerant heat-rejecting effect of a condenser, which is used for condensing the entering refrigerant vapor to a saturated liquid at the entering refrigerant pressure. (2) the portion of the total heat rejection of a condenser that is used for desuperheating and condensing the entering refrigerant vapor to a saturated liquid. This is the product of the mass rate of refrigerant flow and the difference between the enthalpy of the entering refrigerant vapor and that of the saturated refrigerant liquid at the leaving pressure.

rate of heat removal by the refrigerant assigned to the condensing unit in a refrigerating system. This is equal to the product of the mass rate of refrigerant flow produced by the condensing unit and the difference in the specific enthalpies of the refrigerant.

rate of heat removal by the refrigerant assigned to the condensing unit in a refrigerating system. This is equal to the product of the mass rate of refrigerant flow produced by the condensing unit and the difference in the specific enthalpies of the refrigerant vapor entering the unit at a specified superheat and the refrigerant liquid leaving the unit at a specified subcooling.

(1) a contact freezer is a freezer in which the product is frozen by contact with a refrigerated surface. (2) freezing of produce by direct contact with a refrigerated surface. Crust freezing (shell freezing) is very quick freezing of the outer part of a product (mainly poultry), and final freezing is completed by conventional methods.

process of chilling in which finely crushed ice is placed in direct contact with the product in its unpacked or packed state.

matter (such as moisture, vapor, products of combustion, smoke, and particulate matter) rising from cooking equipment during equipment operation,.

reduction of space temperature down to occupied setpoint after a period of shutdown or setup.

reduction of space temperature down to occupied set point after a period of shutdown or setup.

rate of heat absorption by a refrigerating medium (air, water, brine, etc.) flowing through a cooler at stated conditions. It is measured as the product of the mass flow rate of the refrigerating medium and the difference in specific enthalpies of the refrigerating medium entering and leaving the cooler.

(1) ambient air used to remove heat from a device, space, or system. (2) cooled air used to lower the temperature of a space or products stored in a space.

the primary air dry-bulb temperature reduction divided by the primary air entering dry-bulb temperature less the entering secondary wet-bulb temperature.

(1) amount of cooling per unit time required by the conditioned space or product. (2) heat that a cooling system must remove from a controlled system over time.

apparatus for lowering the temperature of a space or product to a specified temperature.

product of minimum height (h) and minimum width (b) of the front opening of a sand trap louver assembly with the louver blades removed. Also see core area of an air terminal device.

velocity-dependent pseudoforce in a reference frame that is rotating with respect to an inertial reference frame, it is equal and opposite to the product of the mass of the particle on which the force acts and its Coriolis acceleration.

the attraction or repulsion between two electric charges acts along the line between them, is proportional to the product of their magnitudes, and is inversely proportional to the square of the distance between them.

air terminal device intended to be installed above a natural ventilation exhaust duct with the aim (by creating negative pressure and depending on wind speed) of avoiding reverse flow and increasing flow rate. It may or may not have moving parts.

science that deals with the production of very low temperatures and their effect on the properties of matter.

process of transforming masses of raw test- or experimentally obtained data (usually gathered by automatic recording equipment) into useful, condensed, or simplified intelligence.

factor of efficiency loss due to the cycling of the unit. It is the effect of reduction in performance under cyclic operation.

A period of time defined by the program administrator, including notifications, deadlines, and transitions, during which demand resources provide demand response. All notifications, deadlines, and transitions may not be applicable to all demand response products or services.

the reduction in the demand from the pre-retrofit baseline to the post-retrofit demand once independent variables (such as weather or occupancy) have been adjusted for. This term is usually applied to billing demand, to calculate cost savings, or to peak.

in freeze drying, ratio of the mass of the substance resulting from a freeze drying process to the mass of the original product. Dryness ratio in freeze drying is the ratio of the mass of dry matter to the mass of frozen substance. See freeze drying (lyophilization).

(1) circular, square, rectangular, or linear air-distribution outlet, generally located in the ceiling, and composed of deflecting members discharging supply air in various directions and planes and arranged to promote mixing of primary air with secondary. (2) duct of increasing area following the outlet of a rotary blower so that the reduced velocity of the fluid will convert some of the kinetic energy into pressure energy.

mechanical venting system supplied or recommended by the manufacturer through which the products of combustion pass directly from the furnace or boiler to the outside and which does not employ a means of draft relief. Includes units that have small air passages in the flue that have an opening area that is not in excess of 10% of the cross-sectional area of the stack.

system where the combustion heat and the products of combustion are transferred directly to the heated medium.

in the flow of fluids through nozzles and orifices, the product of the velocity coefficient and the contraction coefficient. See also air discharge coefficient.

a device, group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply.

(1) conveying means, such as ducts, pipes, and wires, to bring substances or energy from a source to the point of use. The distribution system includes auxiliary equipment such as fans, pumps, and transformers. (2) parts of a cooling tower, beginning with the inlet connection, that distribute the hot, circulating water within the tower to the points where it contacts the air.

element to divert the flow of air from one duct to another.

contact freezer in which the product to be frozen is placed between two refrigerated surfaces and makes contact with both.

a device that is not an integral part of the furnace or boiler and is connected to the furnace or boiler by a short length of flue pipe. It is designed to (a) provide for the exhaust of the products of combustion in the event of no draft, back draft, or stoppage beyond the draft hood, (b) prevent a back draft from entering the furnace, and (c) neutralize the effect of stack action of the chimney or gas vent upon the operation of the furnace.

(1) change in mechanical or electrical characteristics with the passage of time, change in temperature, or both. (2) change in output/input relationship over a period of time with the change unrelated to input, environment, or load. (3) in a cooling tower, water lost as liquid droplets entrained in the exhaust air. It is independent of water lost by evaporation. (4) movement of current carriers in a semiconductor under the influence of an applied voltage.

(also known as carryover eliminator), component that removes entrained moisture from the ducted air.

(1) leak in a liquid system. (2) liquid which appears on thawing frozen food, water melting from evaporator, or water droppings from a cooling surface. (3) pipe or a steam trap and a pipe considered as a unit that conducts condensation from the steam side of a piping system to the water or return side of the system.

system of a central plant that produces conditioned air at two temperatures and humidity levels to supply air through two independent duct systems to the points of usage where mixing may be carried out.

terminal that mixes, for individual zonal needs, varying portions of two independent sources of primary air.

two compartment refrigerated cabinet with one used for chilling foods and the other for either freezing foods or storing frozen products.

a tube or conduit used to convey or encase, an air duct is a tube or conduit used to convey air (air passages in self-contained systems are not air ducts), a pipe duct is a tube or conduit used to encase pipe or tubing.

rigid board composed of insulation material with one or both sides faced with a finishing material. The outer facing is normally a vapor barrier and can also be used as an air barrier.

transmission or radiation of noise from some part of a duct system to an occupied space in the building. Also called flanking path noise or duct radiation.

means intended to facilitate the joining of two components of ductwork.

distribution of air into a room or a building by means of ductwork.

transition between sizes or shapes of duct.

inside dimensions of the duct or duct liner if used in duct.

insulation, usually fiberglass, applied to the inside of a steel ducts. It is used for both thermal retention and sound attenuation reasons.

means taken either to ensure the airtight sealing of the air-distribution system or to minimize leakage therefrom.

calculation of dimensions of ducting for a given air-distribution system with consideration for fan power, noise, etc.

means used to suspend or support ductwork within a building structure.

series of ducts, elbows, and connectors to convey air or other gases from one location to another.

see duct fitting.

section of duct, breeching, or stack used to connect those elements with structures of different cross-sectional dimensions.

distance between or frequency of supports along the length of a duct route.

a listed, packaged system incorporating a hood, a fan, and air-treatment devices designed to remove most grease and particulate matter from the airstream before reintroducing the treated air into the occupied space.

system of ducts for distribution and extraction of air. See system.

the product of the specific heat per gram and the atomic weight of many solid elements at room temperature have almost the same value, about 6.3 calories per degree Celsius (264 J/K).

(1) capability of a building, assembly, component, product, or construction to maintain serviceability for which it was designed over at least a specified time, based on assumed levels of use and maintenance. Compare to serviceability. (2) the average expected service life of a system or facility. Individual manufacturers quantify durability as design life, which is the average number of hours of operation before failure, extrapolated from accelerated life tests and from stressing critical components to economic destruction.

the reduction in the velocity head during flow, consisting of friction or energy losses per length of pipe and losses associated with bends, fittings, valves, etc. The most common equation used to calculate major head losses is the Darcy–Weisbach equation. Older, more empirical approaches are the Hazen-Williams equation and the Prony equation.

(1) electric current induced in the body of a conductor when that conductor either moves through a nonuniform magnetic field or is in a region where there is a change in magnetic flux. (2) localized areas of fluid turbulence known as eddies give rise to persistent vortices.

nondestructive test in which the change of impedance of a test coil brought close to a conducting specimen indicates the eddy currents induced by the coil, thereby indicating certain properties or defects of the specimen (e.g., thickness).

time required from a given initial temperature to freeze a product and to lower its temperature at the thermal center to a given value.

dimension by which a straight duct contributes to the length of an air-distribution installation.

dimension by which a duct fitting contributes to the length of an air-distribution installation.

pipe or duct fitting to make an angle between connected pipes or ducts. If angle is not specified, a 90° angle is implied.

(1) factor equal to the cosine of the phase angle between voltage and current, by which the product of voltage and current is multiplied to convert volt amperes to power in watts. (2) ratio of real power (kW) to apparent power (kVA) at any given point and time in an electrical circuit. Generally expressed as a percentage.

(1) comparison of electricity use to electric demand for a given time period, calculated by dividing electricity usage in kilowatt hours (kWh) by the product of electric demand in kilowatts (kW) times the hours in the period. (2) ratio of average load in kilowatts supplied during a designated period to the peak or maximum load in kilowatts occurring in that period.

the property of an electric circuit or of any object used as part of an electric circuit that determines for a given circuit the rate at which electric energy is converted into heat or radiant energy and that has a value such that the product of the resistance and the square of the current gives the rate of conversion of energy.

common portion of one or more conductors used for transmitting signals or power from one or more sources to one or more destinations.

reciprocal (opposite) of resistance. The current carrying capacity of any wire or electrical component.

case enclosing electrical equipment and wiring that is designed expressly to prevent (1) a person from accidentally contacting uninsulated energized parts, (2) burning or molten materials from contacting adjacent combustible materials or falling onto combustible materials, (3) conductive or combustible materials from dropping on uninsulated energized parts, and (4) mechanical abuse of electrical equipment not designed or approved to withstand the intended normal use without such additional enclosure.

process of producing electron flow by the relative motion of a magnetic field across a conductor.

material having high electrical resistivity and, therefore, suitable for separating adjacent conductors in an electric circuit or preventing possible future contact between conductors.

semiconductor device designed to operate without mechanical contacts (e.g., SCR).

identification and documentation of gross energy usage during a calendar period using any of several means such as source, department, product, equipment, and cost.

more effective use of energy resources. Energy conservation seeks to reduce energy invested per unit of product output, service performed, or benefit received through waste reduction. Energy conservation and energy use reduction are not synonymous.

heat exchanger assembly for transferring heat between two isolated fluid sources. The recovery system may be of air-to-air design or a closed loop hydronic system design. The system will include all necessary equipment such as fans and pumps, associated ducts or piping and all controls (operating and safety), and other custom-designed features.

the reduction in use of energy from the pre-retrofit baseline to the post-retrofit energy use, once independent variables (such as weather or occupancy) have been adjusted for.

An abstract representation of a bi-directional communication interface between devices within a facility and an external electric service provider. This interface enables exchange of information including pricing, energy consumption, demand response interactions, load forecasts, energy production forecasts, and weather information.

the temperature that a thermometer would measure for air entering the evaporator coil. (E.g., for a draw-through fan configuration with no heat gains or losses in the ductwork, EDB equals the indoor dry-bulb temperature).

the temperature that the wet-bulb portion of a psychrometer would measure if exposed to air entering the evaporator coil. For a draw-through fan with no heat gains or losses in the ductwork and no outdoor air mixed with return air, this would also be the zone air wet-bulb temperature. For a similar configuration, but when outdoor air is mixed with return air, EWB equals the mixed-air wet-bulb temperature. For mixtures of water vapor and dry air at atmospheric temperatures and pressures, the wet-bulb temperature is approximately equal to the adiabatic saturation temperature (temperature of the air after undergoing a theoretical adiabatic saturation process). The wet-bulb temperature given in psychrometric charts is really the adiabatic saturation temperature.

(also known as heat content), thermodynamic quantity equal to the sum of the internal energy of a system plus the product of the pressure volume work done on the system. H = E + pv, where H = enthalpy or total heat content, E = internal energy of the system, p = pressure, and v = volume. (Compare to specific enthalpy.)

loss in pressure caused by a fluid stream flowing into a pipe, duct, hood, or vessel.

quantifies environmental information on the life cycle of a product to enable comparisons between products fulfilling the same function

method in which ducts are sized so that their frictional resistance per unit length is constant.

the length of a straight section of pipe or duct causing the same pressure drop as actually occurs within the system at the same flow rate.

(1) a machine used to create flow within a fluid, typically a gas, such as air. (2) any device with two or more blades or vanes attached to a rotating shaft used to produce an airflow for the purpose of comfort, ventilation, exhaust, heating, cooling, or any other gaseous transport. The opening(s) may or may not have an element or elements for connection to ductwork. (3) fan consists of a rotating arrangement of vanes or blades that act on the air (impeller). Usually it is contained within some form of housing or case. This housing or case may direct the airflow or increase safety by preventing objects from contacting the fan blades. Most fans are powered by electric motors, but other sources of power may be used, including hydraulic motors and internal combustion engines. Fans produce airflows with high volume and low pressure, as opposed to compressors, which produce high pressures at a comparatively low volume. A fan blade will often rotate when exposed to an air stream, and devices that take advantage of this, such as anemometers and wind turbines, often have designs similar to that of a fan. (4) see also impeller.

area of the fan or fan-equipment fitting provided for connection to attached ductwork.

the useful power delivered to air by the fan, it is proportional to the product of the fan airflow rate, the fan total pressure, and the compressibility coefficient.

total sound power radiated by the fan and transmitted to the duct and the areas surrounding the fan itself.

the pressure corresponding to the average air velocity at the fan outlet. Measured with pilot tube tranverse of duct. Assumes no change in density or area between the plane of measurement and the fan outlet.

dimensionless number f used in studying fluid friction in pipes, equal to the pipe diameter times the drop in pressure in the fluid due to friction as it passes through the pipe divided by the product of the pipe length and the kinetic energy of the fluid per unit volume.

heat exchanger installed in the hot-gas duct between the boiler and the stack to transfer a portion of the heat (that would be lost up the stack) to the feedwater.

microprocessor (DDC) control panel, field mounted and connected. Compare to product-integrated control.

(1) capacitor and/or inductor placed in a series/parallel combination across a direct current (DC) line to remove the effects of the alternating current (AC) signal or to decrease the ripple voltage in a DC power supply. (2) device to remove gases, liquids, or particles from a mixture of gases, (3) device to remove solid material from a liquid.

lowest temperature at which a product ignites and continues to burn for a specified time after a small flame has been applied to its surface under standardized conditions. Compare to flash point.

boiler with straight tubes surrounded by water through which tubes pass the products of combustion.

reduction in sound transmission loss of a wall caused by sound traveling around the wall by other paths (structure borne, leaks, etc.).

(also known as flaring block), device for shaping the end of a ductile pipe or tube to increase its diameter to a shape suited for a flare fitting.

in a refrigerating system, a separating tank placed between the expansion device and evaporator to separate and bypass any flash gas formed due to pressure reduction.

portion of the liquid refrigerant that is vaporized by sudden reduction of pressure.

(1) at the pump suction, the pressure below which the liquid will flash into vapor. See net positive suction head. (2) in a piping system, the pressure below which the liquid will flash into vapor. (3) in a vacuum-cooling chamber, that pressure corresponding to the vapor pressure at the product temperature and below which water vaporizing commences. (4) lowest temperature to which a product must be heated for its vapors to ignite in the presence of a flame when operating under standardized conditions. Compare to fire point.

(also known as instantaneous vaporization), partial or total vaporization obtained by sudden reduction of pressure.

ducts constructed of flexible materials, such as polymeric films, metal foils, and impregnated fabrics, and used to connect rigid duct to air devices and terminals.

temperature observed at the start of the formation of wax or other solid, determined by a standardized test to assess the low-temperature compatibility of certain petroleum products with refrigerants.

continuous motion of a fluid in pipes, ducts, channels, or through openings. See also airflow, backflow, slip.

experimentally determined proportionality constant relating the actual velocity of fluid flow in a pipe, duct, or open channel to the theoretical velocity expected under certain assumptions.

modulation of a fluid flow rate through a system of piping, ductwork, or variable devices.

(1) a device employing a detecting element that determines the flow rate of a volatile refrigerant in the gaseous or liquid phase within a closed conduit by measuring a suitable response of the detecting element. (2) a device for measuring or determining the mass or volumetric flow rate of a fluid in a duct, pipe, or terminal device.

(also known as vent gas), all gases in a flue during combustion in the combustion chamber, including reaction products such as excess air, carbon dioxide, carbon monoxide, oxygen, water vapor, nitrogen, and other inerts.

chamber designed to capture the products of combustion and accompanying excess air.

an electric, gas, or oil-burning appliance designed to supply heat through a system of ducts with air as the heating medium. Forced-air furnaces circulate the heated air by means of a fan or blower, whereas gravity furnaces depend primarily on natural convection.

(1) dimensionless number used in calculation of unsteady-state heat transfer, equal to the product of the thermal conductivity and a characteristic time divided by the product of the density, the specific heat at constant pressure, and the distance from the midpoint of the body through which heat is passing to the surface. Symbol is Fo, Fo, or NFo. (2) dimensionless number used in unsteady-state flow calculations, equal to the product of the dynamic viscosity and a characteristic time divided by the product of the fluid density and the square of a characteristic length.

apparatus or system for drying substances by dehydration in a frozen state. A drum freeze-dryer apparatus having a rotating cylinder in which a product is freeze dried.

substance added to a product to be freeze dried in order to facilitate recovery of the frozen mass.

(1) any of several dimensionless numbers used in studying fluid friction in pipes, equal to the Fanning friction factor times some dimensionless constant. (2) coefficient used to calculate friction forces due to fluid flow. (3) quotient of the tangential force exerted by a fluid on a surface (per unit area) by half the product of the density and the square of the velocity.

(1) dimensionless number equal to the ratio of the speed of flow of a fluid in an open channel to the speed of very small gravity waves, the latter being equal to the square root of the product of the acceleration of gravity and a characteristic length. (Symbol is Fr2 or NFr 2). See also gravity current. (2) dimensionless number used in studying the motion of a body floating on a fluid with production of surface waves and eddies, equal to the ratio of the square of the relative speed to the product of the acceleration of gravity and a characteristic length of the body. (Symbol is Fr, Fr1, or NFr 1).

solid particles formed by condensation of vapors of solid materials or a discharge gas or byproduct of combustion or chemical process. Very small airborne particles, usually less than one micrometer in size, from burning or melting materials or a chemical process. Note: popularly, the term fumes refers to any kind of air contaminant, many laws and regulations add a qualification that the contaminant have some unwanted action.

(generic term) a fume-collection device mounted over a work space, table, or shelf and serving to conduct unwanted gases away from the area enclosed. The least effective fume hood is a canopy hood, open on four sides. The most effective fume hood effective is an enclosed hood with operable front sash and fixed sides and back. Compare to laboratory fume hood.

an arrangement consisting of a fume hood, its adjacent room environment, and the air exhaust equipment (such as blowers and ductwork) required to make the hood operable.

in the food industry, exposure of a product to gaseous substances, generally to kill insects, their eggs, and larvae.

dimensionless number used in calculation of streamline flow, equal to the mass flow rate of a fluid times its specific heat at constant pressure, divided by the product of its thermal conductivity and a characteristic length. Also spelled Gratz number. Symbol Gz, Gz, or NGz.

dimensionless number used in the calculation of free convection of a fluid caused by a hot body, equal to the product of the fluid’s coefficient of thermal expansion, the temperature difference between the hot body and the fluid, the cube of a typical dimension of the body, and the square of the fluid’s density divided by the square of the fluid’s dynamic viscosity. Also known as free convection number. Symbol Gr, Gr or NGr.

a containment system for the transportation of air and grease vapor. The system is designed and installed to reduce the possibility of the accumulation of combustible condensation, thus reducing the possibility of damage if a fire occurs within the ventilation system.

the sum of the floor areas of all the spaces within the building with no deductions for floor penetrations other than atria. Gross floor area is measured from the exterior faces of exterior walls or from the centerline of walls separating buildings, but it excludes covered walkways, open roofed-over areas, porches and similar spaces, pipe trenches, exterior terraces or steps, roof overhangs, parking garages, surface parking, and similar features.

in a thermal storage system or a heat pump, a closed loop of piping, plastic tubing, or ducting used as a heat exchanger between the ground (acting as a low-grade heat source or heat sink) and a circulating fluid.

isolation damper with a blade which is withdrawn from the duct area when the damper is fully open.

(also known as heat channel or heat leak), part of the boundary construction of an insulated enclosure through which heat can flow readily by conduction.

passage of heat from one point to another or one space to another by one or more of the three modes: conduction, convection, and radiation. See also thermal transmittance.

the heat released when a substance is combusted, determined as the difference in the enthalpy between the reactants (refrigerant[s] and air) and their products after combustion as defined in Section 6.1.3.5. The heat or enthalpy of combustion is often expressed as energy per mass (e.g., kJ/kg or Btu/lb).

(1) rate of heat delivery by the refrigerant assigned to the compressor in a heat pump. (2) rate of heat delivery by the refrigerant assigned to the compressor in a heat pump system equal to the product of the mass rate of refrigerant flow produced by the compressor and the difference in specific enthalpies of the refrigerant vapor at thermodynamic state leaving the compressor and saturated liquid refrigerant at the pressure of the vapor leaving the compressor.

(also called heat transmission, heat transport, and thermal transmission), transfer of energy, in Btu/h (W), induced by a temperature difference. May occur by conduction, convection, radiation, mass transfer, or any combination of these.

concrete slab-on-grade floor containing wires, cables, pipes, or ducts that transfers heat to the conditioned space.

amount of heat produced by the complete combustion of a unit quantity of fuel. The gross or higher heating value is that obtained when all the products of combustion are cooled to the temperature existing before combustion, the water vapor formed during combustion is condensed, and all the necessary corrections have been made. The net or lower heating value is obtained by subtracting the latent heat of vaporization of the water vapor formed by the combustion of the hydrogen in the fuel from the gross or higher heating value.

product that uses only airflow through a medium to remove contaminants from the air.

the amount of heat produced per unit of fuel when complete combustion takes place at constant pressure, the products of combustion are cooled to the initial temperature of the fuel and air, and the vapor formed during combustion is condensed. HHV is expressed in Btu/lb (J/kg) or Btu/ft3 (W/m3) for gaseous fuel and in Btu/lb (J/kg) or Btu/gal (J/l) for liquid fuel.

product of the mass of water evaporated times the latent heat at the evaporating temperature.

duct and fittings used for conveying air in residential, commercial, institutional, and industrial heating, ventilating, and air-conditioning systems.

(1) for a fully filled duct or pipe whose cross section is a regular polygon, the hydraulic diameter is equivalent to the diameter of a circle inscribed within the wetted perimeter. For a fully filled duct or pipe whose cross section is round, the hydraulic diameter is equivalent to the diameter of the duct of pipe. (2) a commonly used approximation is to take four times the flow area divided by the perimeter of the solid boundary in contact with the fluid.

actual productive mass output of an ice-making plant in a given time.

one in which combustion products do not come into contact with the material to be heated, heating of the material is accomplished by radiation or conduction from the heated surface.

an enclosed space within a building that is not a heated space or a cooled space, which is heated or cooled indirectly by being connected to adjacent spaces, provided 1. the product of the U-factors and surface areas of the space adjacent to connected spaces exceeds the combined sum of the product of the U-factors and surface areas of the space adjoining the outdoors, unconditioned spaces, and to or from semiheated spaces (e.g., corridors) or 2. that air from heated or cooled spaces is intentionally transferred (naturally or mechanically) into the space at a rate exceeding 3 ach (e.g., atria).

the entire air volume of a space or building in which the ventilation air is distributed, including ductwork and plenums. The volume of indoor furnishings, equipment, and occupants must be subtracted from the gross indoor volume that is based on interior dimensions of the space or building.

air that is drawn into a terminal by means of induction and discharged through the terminal outlet

entrainment of room air by the jet action of a primary airstream.

ratio of total (primary plus secondary) air to primary air.

terminal that supplies varying proportions of primary and induced air to satisfy the indoor load (excludes fan-powered terminals).

one that uses nozzles or the velocity of the primary air source to induce a flow of secondary air to be mixed with the primary air.

a device that uses nozzles or the velocity of the primary air source to induce a flow of secondary air to be mixed with the primary air.

alternating current load in which current lags voltage.

chemical substance that reduces the rate of corrosion, scale formation, fouling, or slime production.

reduction in sound pressure level caused by installation of an element in the sound path.

(1) thermostat that has an element that is inserted directly into the airstream of a duct or pipe. (2) thermostat with the sensing member in the sensed variable but with the controlling element outside.

a device that is an integral part of a furnace or boiler and is designed to (a) provide for the exhaust of the products of combustion in the event of no draft, back draft, or stoppage beyond the draft diverter, (b) prevent a back draft from entering the furnace, and (c) neutralize the effect of stack action of the chimney or gas vent upon the operation of the furnace.

an installation in which a furnace or boiler is installed indoors and all combustion and ventilation air is admitted through grilles or ducts from outdoors and (all such air) does not communicate with air in the conditioned space.

quick chilling process using air at very high speed forced around the products, usually while those products are continuously moving on a conveyor belt. Compare to air-blast cooling.

set of quantum mechanical phenomena occurring when a current flows through an (electrically) weak link or junction connecting two superconductors (e.g., by tunneling through a dielectric barrier or by flowing through a sufficiently narrow constriction in a superconducting material).

time rate of steady-state heat flow through a unit area of a homogeneous material, induced by a unit temperature gradient in a direction perpendicular to that unit area. Units are Btu in./h·ft2·°F or Btu/h·ft·°F [W/(m·K)].

instrument for measuring the CO₂ concentration in a cold storage atmosphere working on the principle that CO₂ has a thermal conductivity different from other gases. Concentrations of other gases can also be measured using this principle.

the product of the line current (amperes) times the nominal system voltage (kilovolts) times 1.732 for three-phase currents. For single-phase applications, kVa is the product of the line current (amperes) times the nominal system voltage (kilovolts).

when ionization is complete, the conductivity of an electrolyte is equal to the sum of the conductivities of the ions into which the substance dissociates.

equipment or materials to which a label, symbol, or other identifying mark of an organization, acceptable to the authority having jurisdiction, has been attached. This organization is concerned with product evaluation and maintains periodic inspection of the production of labeled equipment or materials. By labeling the equipment or materials, the manufacturer indicates compliance with appropriate standards or performance in a specified manner.

(1) in gravity warm air heating, the duct running horizontally from the furnace to the riser or stack. (2) in plumbing, a water conductor from the roof to the storm drain.

an electromotive force (emf) induced in a conductor is always in such a direction that the current it would produce would oppose the change that causes the induced emf.

the process of evaluating a component, product, assembly, building, etc. and its development from the moment of extraction of raw materials, transportation, processing, manufacturing, use, recyclability, and disposal and assigning a value or assessment of its cumulative and ultimate social, environmental and economic costs, benefits, and impacts. This is often referred to as a cradle-to-grave or cradle-to-cradle assessment.

valve which controls the introduction of liquid refrigerant (e.g., into the intercooler in a multistage compression system).

a method of internally cooling the compressor mechanism or lubricant or the reduction of discharge temperature by introducing saturated or subcooled discharge-side liquid refrigerant into the compressor or condensing unit. Liquid-refrigerant injection mass flow rate is not taken into account when calculating compressor or condensing unit efficiency, capacity, or volumetric efficiency.

equipment or materials included in a list published by an approved, nationally recognized testing laboratory, inspection agency, or other organization concerned with product evaluation which maintains periodic inspection of production of listed equipment or materials and whose listing states either that the equipment or material meets nationally recognized standards or has been tested and found suitable for use in a specified manner.

ratio of actual mean load to a maximum load or maximum production capacity in a given period. See electric power load factor, cooling load factor, heating load factor.

the temperature range for maintaining product in a frozen state in refrigeration applications.

see induction unit and chilled beam.

see induction unit. See chilled beam.

(also known as photometric), referring to a radiometric quantity, luminous indicates the weighted average of the spectral radiometric quantity, with the product of the photopic spectral luminous efficiency functions and the standard solar spectral irradiance distribution being the weighting function.

(1) pipe or duct for distributing flowing fluid to or collecting flowing fluid from various branches. (2) regulated compressed air piped to pneumatic controls.

element inserted in the ductwork that facilitates the determination of air temperature, air humidity, airflow rate, and/or pressure.

the temperature range for maintaining food product above freezing in refrigeration applications. Typically 35°F to 40°F (3°C to 5°C).

thermodynamic state shown by all superconductors in a sufficiently weak magnetic field, characterized by the exclusion or expulsion of magnetic flux from everywhere within the superconductor except a thin surface layer.

(1) rate of energy production of the body. The rate varies with the type of activity. (2) the rate of transformation of chemical energy into heat and mechanical work by metabolic activities within an organism, usually expressed in terms of unit area of the total body surface. Metabolic rate is expressed in met units.

gaseous flow where the average free path of the gas molecules is greater than the largest dimension of the cross section of the duct. Parallel flow.

tested maximum negative pressure at which a duct is rated.

(1) (equipment effective capacity), maximum load that a machine, apparatus, device, or system is capable of carrying under service conditions. (2) capacity (volume) of a room after deducting the loss of space due to coils, columns, air ducts, dunnage, and other dedicated space required to provide air circulation.

(1) (brine cooler) product of the mass rate of water or brine flow and the difference in enthalpy of the entering and leaving water or brine, expressed in heat units per unit of time. It is expressed also by the total refrigeration effect less the heat leakage losses. (2) (condensing unit capacity) rate at which heat is removed from outer media by a refrigerant in the low-pressure side or by the difference in total enthalpy between refrigerant liquid leaving the unit and the total enthalpy of the refrigerant vapor entering it. (3) (packaged air conditioners) rate at which heat is removed from the airstream, as measured entering the cooling coil and leaving the unit. (4) rate at which heat is removed by the primary refrigerant from the cooling medium (secondary coolant) that is used to transmit the refrigerating effect.

that portion of the total refrigeration capacity of a liquid cooler that produces useful cooling. This is the product of the mass flow rate of liquid, specific heat of the liquid, and the difference between entering and leaving liquid temperatures expressed in energy units per unit of time. It is represented also by the total refrigeration capacity less the heat leakage rate

the refrigeration capacity available for space and product cooling. It is equal to the gross total cooling effect less the heat equivalent of energy required to operate the cooler.

the volume of interior usable space intended for refrigerated storage or display, specifically consisting of the usable interior volume within the claimed load limit boundaries. Any of this volume occupied by evaporator coils, fan grilles, ducts (including any space intentionally made unusable by fences and grilles), or any other significant interior protrusions are excluded from the net usable volume. For cases normally equipped with shelves, the front edge of the shelf is assumed to be the front-load limit boundary. To be consistent, shelves and other display devices are not treated as significant interior protrusions. The volume occupied by shelves and other display devices is not subtracted from the net usable volume.

difference between the average sound pressure levels, or sound intensity levels, of two spaces. Usually those two spaces are two adjacent rooms called, respectively, the source room and the receiving room.

for a given product of specified dimensions and at an initial uniform temperature of 32°F (0°C), the time it takes for the thermal center to reach 14°F (–10°C).

nominal value of dimensions of the prepared opening (duct) into which the air terminal device is to be fitted.

reference dimension used for designation, calculation, and application of duct and fitting.

(1) no requirement. (2) noise reduction.

dimensionless number, used in calculation of forced convection, that gives a measure of the ratio of total heat transfer to conductive heat transfer, equal to the heat transfer coefficient times a characteristic length divided by the thermal conductivity.

size in the object plane which corresponds to the products of the system’s instantaneous field of view in radians and the distance from the system to the object.

efficiency of the reduction of odors by a device.

the position of the sash at which the fume hood user places the sash while working at the face of the fume hood. The operating opening should take into consideration all of the procedures to be conducted in the fume hood. There may be more than one operating opening.

a cleanroom in normal operation with all services functioning and with production equipment and personnel present and performing normal work functions.

any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit, or ground fault.

production operation for slaughtering, dressing, and processing animals, also used in connection with processing vegetables and fish.

(1) partial pressure of component i for any (ideal or nonideal) gas mixture is the product of the mole fraction of the component, xi, and the mixture pressure, p. [ pi = xi • p for any gas mixture]. (2) portion of total gas pressure of a mixture attributable to one component (Dalton’s law of gases).

dimensionless number used in calculation of heat and mass transfer, consisting of the mass velocity times a characteristic length and the specific heat at constant pressure, divided by the thermal conductivity. Symbol Pe, Pe, or NPe.

evolution or absorption of heat produced by an electric current passing across junctions of two suitable dissimilar metals, alloys, or semiconductors.

a series of numbers and letters consisting of the letters AM, AI, or AU and a two or three digit number. AM identifies an \"as manufactured\" test, that is, the laboratory hood is built and assembled by the manufacturer and testing is performed at the factory. The typical equipment remains in the hood and other activities in the laboratory continue. AI identifies an \"as installed\" test, that is, the laboratory hood is installed at the location of the customer. The hood is tested empty, but with the ventilation system in the installation balanced and the hood in its final location. AU identifies an \"as used\" test, that is, the tests are conducted after the hood has been installed and used by the chemist. An example of the series of numbers and letters is AM yyy where AM identifies an \"as manufactured\" test and yyy is the control level of tracer gas established by the test in ppm. A test rating of AU 0.5, for example, would indicate that the hood controls leakage into the laboratory to 0.5 ppm at the mannequin's sensing point with a tracer gas release rate of 4.0 Lpm (70 mL/s).

time rate of water vapor transmission through unit area of flat material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. When permeability varies with psychrometric conditions, the spot or specific permeability defines the property at a specific condition. Note: permeability is a property of a material, but the permeability of a body that performs like a material may be used. Permeability is the arithmetic product of permeance and thickness.

product-integrated control (PIC)

longitudinal folded joint used in rectangular sheet-metal duct construction. Pocket lock joint transverse joint used in rectangular sheet metal duct construction.

(also called plenum box and plenum chamber) (1) a compartment or chamber, to which one or more ducts are connected, that forms a part of the air-distribution system and that is not used for occupancy or storage. A plenum often is formed in part or in total by portions of the building. (2) an air compartment that is attached to, or is an integral part of, a forced-air furnace which is designed to either distribute the heated air after it leaves the heat exchanger in the case of a supply plenum or to collect air that enters the return inlet in the case of a return plenum. (3) component forming an interface between a ductwork and one or more air terminal devices, by virtue of its design or by the inclusion of accessories, it can also be used to equalize the pressure/velocity across the air terminal device.

a salt and a strong oxidizing agent that causes substances to lose electrons.  Can convert ozone (O₃) into oxygen (O₂).  Does not generate toxic byproducts.

a salt and a strong oxidizing agent that causes substances to lose electrons.  Can convert ozone (O₃) into oxygen O(₂).  Does not generate toxic byproducts.

a factor, equal to the cosine of the phase angle between current and voltage, by which the product of voltage and current is multiplied to convert volt amperes to power in watts.

(1) dimensionless number used in calculation of forced and free convection, equal to the dynamic viscosity times the specific heat at constant pressure, divided by the thermal conductivity. (2) dimensionless number used in calculation of diffusion in flowing systems, equal to the kinematic viscosity divided by the molecular diffusivity. Symbol is Pr or Pr. Also known as Schmidt number 1 (Sc, Sc, or NSc1).

(1) heating a food product prior to a subsequent treatment. (2) in air conditioning, to heat the air ahead of other processes. (3) to heat the water prior to heating by the auxiliary thermal source.

direct digital control (DDC) panel, factory mounted and connected, able to monitor, control, and diagnose the significant functions of the equipment of which it is a part. Compare field-installed device.

direct digital control (DDC) panel, factory mounted and connected, able to monitor, control, and diagnose the significant functions of the equipment of which it is a part. Compare to field-installed device.

impeller housings and impellers are always placed sufficiently below the expected pumping level to prevent cavitation at the peak production rate. For example, this pump should be placed at least 115 ft (30 m) below the casing top [pump setting depth = 115 ft (30 m)] to allow for adequate submergence at peak flow. The specific net positive suction head (NPSH) pressure required for a pump varies with each application and should be carefully considered in selecting the setting depth.

required on lithium bromide absorption equipment to remove noncondensables (air), which leak into the machine, or hydrogen (a product of corrosion), which is produced during equipment operation. Even in small amounts, noncondensable gases can reduce chilling capacity and even lead to solution crystallization. Purge systems for larger sizes above 100 tons (359 kW) of refrigeration typically consist of these components: vapor pickup tube(s), noncondensable separation and storage tank(s), and vacuum pump or valving system.

a procedure employed for verifying the accuracy of the measuring techniques (temperature, airflow rates, duct heat calibration) employed in determination of the room heating effect. This qualification procedure is periodically employed in determining the room heating effect.

a process for evaluating a subset (sample) of the total population. The sample is based upon a known or estimated probability distribution of expected values, an assumed statistical distribution based upon data from a similar product, assembly, or system, or a random sampling that has scientific statistical basis.

(1) measure of the acoustical absorption properties of a room, the average absorption of all the surfaces in a room times the total surface divided by the average reflection. (2) (also known as thermal resistance), quantity determined by the temperature difference, at steady state, between two defined surfaces of a material or construction that induces a unit heat flow rate through unit area (R = ?T/q). R-value is the reciprocal of thermal conductance.

sound power that radiates from terminal casings and induction ports for induction terminal units.

energy or work producing part of apparent power. The rate of supply of energy, measured commercially in kilowatts. The product of real power and length of time is energy, measured by watthour meters, and expressed in kilowatt hours (kWh).

to process used refrigerant to new product specifications.

splitting of refrigerant compounds by reaction with water (e.g., reaction of dichlorodifluoromethane or methyl chloride with water, forming acid products).

heat removal by direct contact of the packaged product with refrigerated plates.

contaminants include water (the most important and universal contaminant), dirt, particles, organic materials such as waxes, acids, and sludges, or other products of chemical reactions taking place while the system is operating.

in freeze drying, that part of the water contained in the product and that may be extracted without spoiling the quality of the product.

in a freeze-dried product, the ratio of the mass of residual water to the original mass of product.

(1) property of an electric circuit, or of any object used as part of an electric circuit, that determines for a given current the rate at which electric energy is converted into heat or radiant energy and that has a value such that the product of the resistance and the square of the current gives the rate of conversion of energy. (2) property opposing movement of material or flow of energy and involving loss of potential (voltage, temperature, pressure level). (3) thermal resistance. See electrical resistance (O), thermal resistance.

(1) dimensionless group equal to four times the Fanning friction factor. Also known as Darcy-Weisbach coefficient and Darcy number 1. (2) dimensionless number used in the study of flow resistance, equal to the resistance force in flow divided by one-half the product of fluid density, the square of fluid velocity, and the square of a characteristic length.

the electrical conducting medium that is heated by an electric current and that also dissipates this heat into the air or a fluid.

(1) electric load with all energy input converted to heat and light. (2) electric load without capacitance or inductance or one in which inductive portions cancel capacitive portions at the operating frequency.

product of an energy resource [includes application of resource utilization factor (RUF)] anticipated to be used in providing fuel or energy to a building site, multiplied by an RIF for that particular form of energy resource. Total resource energy impact is the sum of all resource energy impacts for a building project.

(1) breathing process of animals. (2) production of carbon dioxide and heat by ripening of perishables in storage.

pipe or duct to carry fluid back to the source.

dimensionless number used in studying the stratified flow of multilayer systems, equal to the acceleration of gravity g times the density gradient of a fluid divided by the product of the fluid’s density and the square of its velocity gradient at a wall (symbol NR).

ducts constructed of rigid materials such as metal and fiberglass duct board.

calculated by using the average inside duct dimensions determined by measurement of a minimum of three representative sections of the duct envelope.

packaged air conditioner mounted on a roof, the conditioned air being discharged directly into the rooms below or through a duct system.

ratio of size of projections from the surface of a pipe or duct to the diameter of the pipe or duct.

the dry-bulb temperature reduction achieved by the ECU divided by the entering wet-bulb depression.

(1) the formation of thick corrosion product layers on a metal surface at high temperature. (2) the precipitation of water-insoluble constituents on a surface.

positive displacement compressor in which the reduction in internal volume of the compression chamber is accomplished by an orbiting scroll (involute spiral) within a mating stationary scroll.

reduction of heating (by reducing the setpoint) or cooling (by increasing the setpoint) during hours when a building is unoccupied or during periods when lesser demand is acceptable.

natural ventilation by means of a duct mounted vertically or near vertically.

device or unit installed in air duct systems to reduce air noise in the duct. See sound attenuator.

interruption of any one conductor in a three-phase system.

system in which the air, having been conditioned, is distributed to various zones through a single duct.

a terminal unit supplied with one source of supply/exhaust air. This type of terminal excludes fan-powered terminal units.

air-terminal unit assembly having one ducted air inlet and a device for regulating the airflow rate so it is independent of inlet pressure changes.

method of constructing transverse seams in rectangular sheet metal ducts.

product of decomposition of oil resulting from impurities, moisture, or chemical reactions and favored by excessive temperature. Sludge may be mushy, gummy, or hard.

longitudinal folded joint used for rectangular sheet metal duct construction in which the seam is snapped together.

the ratio of the solar heat gain entering the space through the fenestration area to the incident solar radiation. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation, which is then reradiated, conducted, or convected into the space.

process in which sound energy is absorbed or otherwise diminished in intensity.

acoustical treatment of constructions and equipment such as fan housings, supply ducts, and space enclosures to reduce the amplitude of the sound present by absorbing energy from the wave, or reducing the vibration amplitude by using damping or mass or both to reduce transmitted noise.

statement of a set of requirements to be satisfied by a material, product, system, or service that indicates the procedures for determining whether each of the requirements is satisfied. Note: it is desirable to express the requirements numerically in terms of appropriate units, together with their limits.

temperature of spontaneous ignition of a product in the absence of a flame, determined under standardized conditions.

freeze-drying process during which a liquid product is sprayed frozen prior to sublimation of the ice.

system for lowering the temperature of water by conductive and evaporative cooling of the water in contact with outside air. Water to be cooled is sprayed by nozzles into the air above a pond of water and allowed to fall into the pond.

(1) movement of air into and out of buildings, chimneys, flue gas stacks, or other containers and is driven by buoyancy. Buoyancy occurs due to a difference in indoor to outdoor air density resulting from temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect is also referred to as the chimney effect, and it helps drive natural ventilation and infiltration. (2) movement of air or other gas in a vertical enclosure (e.g., duct, chimney, building), induced by the density difference between the air or other gas in the enclosure and the ambient atmosphere. Note: stack effect is a significant concern in heating-system design for tall buildings in cold climates. Sometimes referred to as chimney effect. (3) pressure difference caused by the difference in density between indoor and outdoor air due to an indoor/outdoor temperature difference. (4) the vertical airflow within buildings caused by temperature differences between the building's interior and exterior.

the power used by a product or appliance when enabled but in the standby operating mode (Refer to 10 CFR 430).

folded joint used for transverse joints in rectangular sheet metal duct construction and for apparatus-casing seams.

dimensionless number used in calculation of forced convection, equal to the heat transfer coefficient of a fluid divided by the product of the specific heat at constant pressure, the fluid density, and the fluid velocity. Symbol St, St, or NSt. Also known as the Margoulis number M.

(1) external static pressure loss for forced-air systems using packaged air-handling equipment, the static pressure loss resulting from airflow through the supply and return ductwork and other elements external to the packaged air-handling unit. Compare to internal static pressure loss and total static pressure loss. (2) internal static pressure loss for forced-air systems, the static pressure loss resulting from airflow through the internal elements of the packaged air-handling unit. These internal elements may include such items as filters, coils, dampers, mixing sections, etc. Compare to internal static pressure loss and total static pressure loss. (3) total static pressure loss for forced-air systems, the sum of the external static pressure loss and the internal static pressure loss. See internal static pressure loss and external static pressure loss. The term is not applicable to an individual fan or a fan located within a builtup air-handling unit. Fans are rated by the term fan total static pressure, which is not the same as fan total pressure. Compare to fan total pressure.

method in which ducts are sized so that the regain in static pressure due to decreased velocity between two points totally or partially compensates for the frictional resistance between the points.

(1) ratio of the volume occupied by the quantity of a particular product stored to the maximum that can be stored, taking into account the requirements of that particular product. (2) reciprocal of capacity factor.

layers of air at different temperatures or different velocities flowing through a duct or plenum system and affect fan and/or pump performance in the distribution system.

chilling a product to a temperature very near or sometimes below its freezing point.

low-temperature thermodynamic state in which a superconductor exhibits the property of superconduction.

property of certain substances characterized by their zero DC electrical resistivity for low currents when their temperature is sufficiently low.

temperature below which, in the absence of all external influences, a substance becomes superconducting.

(1) substance exhibiting or capable of exhibiting superconduction. (2) Type I: superconductor for which the Meissner state and the normal state can coexist in thermodynamic equilibrium. (3) Type II: superconductor capable of existing in the mixed state.

(1) group of tubes in a boiler that absorb heat from the products of combustion to raise the temperature of the vapor passing through the tubes above the temperature corresponding to its pressure or saturation temperature. (2) heat exchanger used on flooded evaporators, where hot liquid on its way to enter the evaporator is cooled by giving up heat to both dry and superheat the wet vapor leaving the evaporator.

the reciprocal of the heat transfer film coefficient, Ri or Ro, in h·ft2·°F/Btu ([m2·K]/W). (Subscripts i and o often denote inside and outside surface film resistances and conductances, respectively.) For convection to occur, the surrounding space must be filled with air or another fluid. If the space is evacuated, heat flow occurs by radiation only.

time rate of heat flow from a unit area of a surface to its surroundings, induced by a unit temperature difference between the surface and the environment. Note: the environment is a fluid (liquids or gases).

definitive procedure that produces a test result. Note: appropriate functions of a test method are identification, measurement, or evaluation of one or more qualities, characteristics, or properties of a material, product, system, or service.

differential in total pressure between the inlet and the outlet sections of a test duct or across a test fitting. For test fittings, the fitting is assumed to have zero length. For multiflow fittings, the total pressure loss shall be determined for each stream separately.

the sum of the products of masses and heat capacities of all components (including the transfer fluid) contained within the insulating envelope of the thermal storage device.

nonconducting physical structure, such as a frame around a door or window acting to retard heat flow.

the condition of mind which expresses satisfaction with the surrounding thermal environment and is assessed by subjective evaluation. Thermal comfort is affected by heat conduction, convection, radiation, evaporative heat loss, and relative air motion.

time rate of steady-state heat flow through unit area of a material or construction, induced by a unit temperature difference between the body surfaces. Units are Btu/h·ft2·°F (W/[m2·K]). Note that the C-factor does not include soil or air films.

(k-factor), time rate of steady-state heat flow through unit thickness of unit area of a homogeneous material, induced by a unit temperature gradient in a direction perpendicular to the isothermal planes of that unit. Units of k are in Btu·in/(h·ft2·°F), Btu·ft/(h·ft2·°F), or W/(m·K). Thermal conductivity must be evaluated for a specific mean temperature, thickness, age, and moisture content. See also thermal conductance.

material that transmits heat by conduction.

transfer of heat by a fluid moving by natural variations in density (in the absence of conduction and radiation).

physical quantity that determines the rate of heat propagation in transient state processes. Thermal conductivity divided by the product of density and specific heat. Units are ft2/s or m2/s.

(1) thermal energy storage may refer to a number of technologies that stores energy in a thermal reservoir for later reuse. They can be employed to balance energy demand between day time and night time. The thermal reservoir may be maintained at a temperature above (hotter) or below (colder) than that of the ambient environment. The principal application today is the production of ice, chilled water, or eutectic solution at night, which is then used to cool environments during the day. (2) thermal energy storage technologies store heat, usually from active solar collectors in an insulated repository for later use in space heating, domestic or process hot water, or to generate electricity. Most practical active solar heating systems have storage for a few hours to a day's worth of heat collected. There are also a small but growing number of seasonal thermal stores used to store summer heat for space heating during winter.

heating or cooling effect delivered to a product or space.

(R-value), the reciprocal of the time rate of heat flow through a unit area induced by a unit temperature difference between two defined surfaces of material or construction under steady-state conditions. Units of thermal resistance are h·ft2·°F/Btu (m2·°K/W). Thermal resistance is the reciprocal of the thermal conductance.

(also known as U-factor), heat transmission in unit time through unit area of a material or construction and the boundary air films, induced by unit temperature difference between the environments on each side. Note: this heat transmission rate is also called the overall coefficient of heat transfer. U, in Btu/h·ft2·°F (W/[m2·K]). Thermal transmittance is sometimes called the overall coefficient of heat transfer or U-factor. Thermal transmittance includes surface film conductance.

(water or brine cooler), product of the mass rate of refrigerant flow and the difference in enthalpy of the entering and leaving refrigerant fluid, expressed in heat units per unit of time.

the product of the mass flow rate of refrigerant and the difference in enthalpy between the leaving and entering refrigerant, expressed in energy units per unit of time.

the ability of a substance to be harmful or lethal due to acute or chronic exposure by contact, inhalation, or ingestion. The effects of concern include, but are not limited to, those of carcinogens, poisons, reproductive toxins, irritants, corrosives, sensitizers, hepatoxins, nephrotoxins, neurotoxins, agents that act on the hematopoietic system, and agents that damage the lungs, skin, eyes, or mucous membranes.

the ability of a refrigerant to be harmful or lethal due to acute or chronic exposure by contact, inhalation, or ingestion. The effects of concern include, but are not limited to, those of carcinogens, poisons, reproductive toxins, irritants, corrosives, sensitizers, hepatoxins, nephrotoxins, neurotoxins, agents that act on the hematopoietic system, and agents that damage the lungs, skin, eyes, or mucous membranes.

see duct fitting, pipe fittings.

reduction in magnitude of some characteristic of a power or a signal between two stated points in a system.

properties that describe the capability of a fluid to transfer heat and momentum, typically thermal conductivity and dynamic or kinematic viscosity.

transverse (girth) joint used to assemble duct and fittings.

method of measuring air and fluid volumetric flow in ductwork and piping systems.

tubular conduit for transport of fluids or finely divided solids, also, a hollow structural member, a hollow product of round or other cross section. A tube may be helical welded, lap welded, spiral welded, butt welded, or seamless. A tube is designated by its exact outside diameter and its exact wall thickness, which may be described in gage numbers or other units. As an example, copper tube is commonly used in the piping and plumbing industry and the normal wall thickness is 0.125 in. (3.2 cm). When describing the outside diameter, it is referred to as copper tube. When describing the nominal pipe size, it is referring to the inside diameter. Tube or tubing identifies the outside diameter. Pipe or piping identifies the inside diameter.

(1) axial fan whose blades revolve in a cylindrical casing. The term “ducted fan” is used when the casing is of substantial length. (2) propeller or disc-type wheel within a cylinder, and including driving-mechanism supports for either belt drive or direct connection.

formation over a surface of scattered, knob-like mounds of localized corrosion products.

a series of single thickness or airfoil radius sheet metal guides placed within a rectangular duct elbow to reduce turbulence and associated pressure drop within the elbow and to direct air around the bend.

a hood designed to capture heat, odors, products of combustion, and/or moisture where smoke or grease laden vapor is not present. A Type II hood may or may not have filters or baffles and does not have a fire suppression system.

unit thermal conductance or overall heat transfer coefficient, W/(m²·K) (Btu/(h·ft²·°F).

device to regulate or stop the flow of fluid in a pipe or a duct by throttling.

if the temperature of interacting substances in equilibrium is raised, the equilibrium concentrations of the reaction are changed, so that the products of that reaction that absorb heat are increased in quantity, or if the temperature for such an equilibrium is lowered, the products that evolve heat in their formation are increased in amounts.

fan that moves air in the general direction of the axis about which it rotates, parallel to the shaft, and flow through the centrifugal fan wheel, impeller, or propeller is substantially radial. The fan is typically mounted in a round duct or tube to improve pressure characteristics and has vane-type straighteners to remove much of the swirl or spin of the air created by the fan wheel to improve fan efficiency. Fans can be either direct drive or belt driven.

method in which ducts are sized so that selected velocities occur in specific duct lengths.

(1) opening in a tank, duct, or other piece of equipment, sealed to prevent escape of material within normal pressures, but arranged to open automatically to relieve excessive pressure. (2) relief opening in a pressure regulator, normally open to the atmosphere.

contraction in a pipeline or duct that increases the fluid velocity to lower its static pressure, followed by a gradual expansion to allow recovery of static pressure. Used for metering and other purposes that involve change in pressure.

in any rotating equipment where the isolation of its vibration is by devices external to the unit. Note: examples: flex duct connections, pipe flex connections, and spring isolators.

the ratio of visible radiation entering the space through the fenestration product to the incident visible radiation, determined as the spectral transmittance of the total fenestration system, weighted by the photopic response of the eye and integrated into a single dimensionless value.

unit of voltampere reactive power. For a two wire circuit, the product of the voltage times the current times the sine of the angular phase difference by which the voltage leads or lags the current. VARs and watts combine in a quadrature to form voltamperes.

device mounted in a duct or opening used to vary the volume of air flowing through.

opening in a wall having a shroud insert to accept a pipe, duct, or equipment installed in or through the wall.

when the temperature of a radiating blackbody increases, the wavelength corresponding to maximum energy decreases in such a way that the product of the absolute temperature and the wavelength is constant.