ASHRAE Terminology

(1) device containing fluid, or other material, for absorbing refrigerant vapor or other vapors. (2) part of the solar collector receiving the incident radiation energy and transforming it into thermal energy. It may possess a surface through which energy is transmitted to the transfer fluid, however, the transfer fluid itself can be the absorber.

absorption chillers differ from mechanical vapor compression chillers because they utilize a thermal or/and chemical process to produce the refrigeration effect necessary to provide chilled water. There is no mechanical compression of the refrigerant taking place within the machine, as occurs within more traditional vapor compression type chillers.

refrigeration is created by evaporating a refrigerant in a heat exchanger (evaporator) with the vapor then absorbed by an absorbent medium from which it is subsequently expelled by heating at a higher partial vapor pressure (in a generator) and condensed by cooling in another heat exchanger (condenser).

(1) apparatus to store cold by accumulation of ice on a coil. (2) pressure vessel connected to more than one circuit of a pneumatic system to obtain the average pressure of the connected circuits. (3) vessel for storing low pressure side liquid refrigerant, also known as a low pressure receiver, surge drum, surge header, or surge tank.

the adverse health effect(s) from a single, short-term exposure, as might occur during an accidental release of refrigerants or other toxic chemicals.

the refrigerant, or chemical, concentration limit and intended to reduce the risk of acute toxicity hazards in normally occupied, enclosed spaces. ATEL values are similar to the immediately dangerous to life or health (IDLH) concentrations set by the National Institute of Occupational Safety and Health (NIOSH). ATELs include explicit, additional components for cardiac sensitization and anesthetic effects, but they do not address flammability. The lowest of the ATEL, 50,000 ppm by volume, or 10% of the lower flammability limit, therefore, provides a conservative approximation to IDLH concentrations when needed for refrigerants without adopted IDLH values.

(1) efficiency with which work is done with respect to heat gains or losses. (2) (indicated efficiency) ratio of the work absorbed in compressing a unit mass of refrigerant in an ideal compressor (isentropic process) to the work absorbed in compressing the same mass in an real compressor. See isentropic process.

a refrigerant condenser in which heat removal is accomplished entirely by heat absorption by air flowing over condensing surfaces. See also condenser, desuperheater, double-pipe condenser (tube-in-tube condenser), evaporative condenser, shell-and-tube condenser.

anhydrous ammonia (NH3).

device in the high side of an absorption system for increasing concentration of refrigerant in the vapor entering the rectifier or condenser.

typical additives that scavenge oxygen-containing species to prevent further breakdown of the lubricant or refrigerant.

the concentration of a substance, such as a refrigerant, that is lethal to even a single test animal when tested by the same conditions as for an LC50 test.

power input to devices that are not integral to the operation of the vapor compression cycle, excluding power input to integrated pumps (if present) used for liquid in either the evaporator or the condenser. Auxiliary power includes devices such as, but not limited to, oil pumps, refrigerant pumps, control power, fans, and heaters.

a blend containing two or more refrigerants whose equilibrium vapor and liquid phase compositions are the same at a given pressure. At this pressure, the slope of the temperature versus composition curve equals zero, which mathematically is expressed as (dt/dx)p = 0, which, in turn, implies the occurrence of a maximum, minimum, or saddle point temperature. Azeotropic blends exhibit some segregation of components at other conditions. The extent of the segregation depends on the particular azeotrope and the application.

a blend that contains two or more refrigerants whose equilibrium vapor phase and liquid phase compositions are the same at a given pressure. The temperature of an azeotropic refrigerant remains constant as it evaporates or condenses at constant pressure (compare to zeotropic refrigerant).

pipe attached to a unit, such as a condenser, to bleed off liquid refrigerant parallel to main flow.

a refrigerant consisting of a mixture of two or more different chemical compounds, often used individually as refrigerants for other applications.

refrigerants consisting of mixtures of two or more different chemical compounds, often used individually as refrigerants for other applications.

part of an absorption machine in which the refrigerant vapor is driven off by heat.

a heat exchanger for cooling brine with an evaporating refrigerant.

(1) in a brine circulating system, a storage or balance tank for brine. (2) in an ice plant, a main freezing tank in which cans are immersed while ice is being produced. (3) in domestic and commercial fields, a container surrounding the evaporator and filled with brine for storing refrigerant or equalizing temperature at various points of the evaporator (especially an ice cream cabinet).

the liquid saturation temperature of a refrigerant at the specified pressure; the temperature at which a liquid refrigerant first begins to boil. The bubble point of a zeotropic refrigerant blend, at constant pressure, is lower than the dew point.

An apparatus for measuring heat quantities generated in or emitted by materials in processes (e.g. may be used for determining refrigerant flow rate by the principle of known heat input or output, known physical characteristics of the transfer media and observed thermal differences).

(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.

the cooling effect produced by the change in enthalpy between the refrigerant liquid entering the expansion valve and the vapor leaving the evaporator, generally measured in Btu per hour (kW or tons of refrigeration).

(1) refrigerating capillary tube is a tube of small bore used for the simultaneous purposes of metering the refrigerant and of accomplishing the expansion process between condenser and evaporator in refrigerating systems. (2) small-bore tube used for metering by controlling length and bore size. In refrigeration, a tube of small internal diameter used as a refrigerant pressure and flow control between high and low sides. (3) tube used to transmit pressure from the sensitive bulb of some temperature controls to the operating element.

one having two or more refrigerant circuits, each with a pressure-imposing element, condenser, and evaporator, where the evaporator of one circuit cools the condenser of another (lower temperature) circuit.

a device that allows the accurate vacuum transfer of small volumes of gaseous refrigerants to the sealed tube (or metal test cell) containing precharged lubricant. This apparatus consists of a manifold (metal or glass), vacuum pump, pressure gage, high vacuum gage, refrigerant cylinder, valves, and filling ports. The function of this apparatus is to evacuate the tube, degas the lubricant, add refrigerant along with the test materials, and seal it. It is calibrated so that the required mass of refrigerant is added very accurately by following the change in pressure on the pressure gage as refrigerant is added to the tube.

device to enable a refrigerating system to be charged with refrigerant. Also, the tube or hose through which charging is accomplished.

valve used to charge or add refrigerant to a system or add oil to a compressor crankcase.

(1) generally, any of several compounds composed of carbon, fluorine, and chlorine, used chiefly as refrigerants and as blowing agents in plastic foams. Compare to fluorocarbon, halocarbon. (2) a fully halogenated (no hydrogen remaining) halocarbon containing chlorine, fluorine, and carbon atoms.

flooded evaporator comprising a low-pressure receiver, in which the unvaporized refrigerant returns to the evaporator inlet by gravity or by means of a pump or an ejector.

formerly in extensive use but now becoming obsolete as a result of code change to classification. Systems are classifications according to the degree of probability that a leakage of refrigerant will enter occupied areas. The two classifications are high probability system or low probability system. See ASHRAE Standard 15.

water-cooled condenser in which water and refrigerant flow in parallel paths but in opposite directions.

control device in which one or more control variables are being monitored (such as a combination high- and low-pressure control for a refrigerant system).

multistaged refrigerating system where a single charge of refrigerant circulates through all stages of compression.

refrigerating cycle composed of four principal stages: vaporization of the refrigerant, compression of the vapor, liquefaction of the vapor, and expansion of the liquid.

System in which refrigeration is affected by the vaporization at low pressure in a heat exchanger (evaporator) of a liquid refrigerant, the vapor thus formed being restored to the liquid state by mechanical compression to a higher pressure and subsequent cooling in another heat exchanger (condenser).

(1) device for mechanically increasing the pressure of a gas. (2) often described as being either open, hermetic, or semihermetic to describe how the compressor and motor drive is situated in relation to the gas or vapor being compressed. Types include centrifugal, axial flow, reciprocating, rotary screw, rotary vane, scroll, or diaphragm. 1. device for mechanically increasing the pressure of a gas. 2. specific machine, with or without accessories, for compressing refrigerant vapor.

apparatus for determining the refrigerant flow rate and, subsequently, the capacity of a refrigerant compressor by measuring the heat input required to balance the refrigerating effect produced in the evaporator by the compressor.

(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.

process whereby a side port in the compressor (usually a screw compressor or multiwheel centrifugal compressor) is used to provide refrigerant subcooling, resulting in an improvement in overall system efficiency.

the ratio of the work absorbed for compressing a unit mass of refrigerant in a compressor or condensing unit to the work absorbed for compressing the same unit mass of refrigerant in an isentropic compressor or condensing unit. (Also known as isentropic efficiency.)

(also known as isentropic efficiency), the ratio of the work absorbed for compressing a unit mass of refrigerant in a compressor or condensing unit to the work absorbed for compressing the same unit mass of refrigerant in an isentropic compressor or condensing unit.

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.

the saturation temperature corresponding to the refrigerant pressure at the compressor discharge, usually taken at or immediately downstream of the compressor discharge service valve (in either case on the downstream side of the valve seat), where discharge valves are used.

condition achieved in a centrifugal compressor when the momentum of the refrigerant gas through the compressor is insufficient to overcome the thermal lift requirement. Direction of flow temporarily reverses through the compressor until the lift requirement decreases. The condition repeats until the operating condition is corrected. Accelerated wear and damage can eventually result.

a refrigerating component, designed to compress a specific refrigerant vapor, consisting of compressor, prime mover, and regularly furnished accessories.

ratio of volume of compression chamber at intake of refrigerant gases to the volume at discharge in positive displacement compressors.

(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.

(1) an apparatus for processing low-pressure refrigerant vapor back into high-pressure liquid refrigerant to be used for cooling a refrigerator. (2) machine designed to condense refrigerant vapor to a liquid by compressing the vapor in a positive displacement compressor and rejecting heat to a cooling medium. A condensing unit usually consists of one or more positive displacement compressors and motors, condensing coils, liquid receivers, and other devices mounted on a common base.

apparatus for determining refrigerant flow rate and, subsequently, the capacity of a condensing unit by measuring the heat input required to balance the refrigerating effect produced in the evaporator by the condensing unit.

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.

to remove heat in an environment generally at a temperature not below 33°F (–1°C). Compare to refrigerant.

a single-phase fluid (usually a liquid) used for transferring heat from one place to another. Sometimes referred to as heat transfer fluid, brine, and/or secondary refrigerant (see refrigerant).

an arrangement of pipes or tubes, not enclosed in a pressure vessel, that can be used either with refrigerant or secondary coolant to provide cooling or cooling with dehumidification.

the flow rate of liquid refrigerant required for all cooling purposes in a compressor or condensing unit.

substance used, with or without a change of state, to lower the temperature of other bodies or substances. See coolant. See refrigerant.

compromise refrigerant quantity required by a system to maximize performance when a capillary or fixed restriction expansion device is used.

piping arrangement for collecting oil or liquid refrigerant from suction gas prior to entry to a compressor.

a device for removing moisture from refrigerant or other substances.

(1) a solid that will collect and hold water from a liquid or gas. It must be insoluble in the refrigerating medium to be in order to be used in refrigerant driers. (2) absorbent or adsorbent liquid or solid that removes water or water vapor from a material.

sensible heat rejection from gaseous refrigerant in a condenser. Occurs prior to the gas-to-liquid phase change.

refrigerating absorption system that, in addition to refrigerant and absorbent, also has an inert medium (such as hydrogen) to balance pressure in the various parts of the refrigerating circuit.

(1) system in which the cooling effect is obtained directly from the expansion of the liquid refrigerant into a vapor. (2) common term applied to an air-conditioning or refrigeration system that utilizes the vapor-compression refrigeration cycle. In a vapor-compression refrigeration cycle, the refrigerant removes heat in the evaporator by directly expanding the entering liquid refrigerant into vapor as it leaves the evaporator. The vapor is then compressed and piped to a condenser where the heat removed by the evaporator and the heat of compression are rejected to another medium so that the gaseous refrigerant is condensed to a liquid. The liquid is then piped to a pressure reducing device/metering device to be supplied to the evaporator.

(also known as hot gas line), line through which refrigerant vapor flows from a compressor to a condenser.

(1) the pressure generated on the leaving side of a fan or pump. (2) the pressure generated on the output side of a gas compressor in a refrigeration or air-conditioning system. The discharge pressure is affected by several factors: size and speed of the condenser fan, condition and cleanliness of the condenser coil, and the size of the discharge line. An extremely high discharge pressure coupled with an extremely low suction pressure is an indicator of a refrigerant restriction. It is also called high-side pressure or head pressure. (3) operating pressure in a system measured in the discharge line at the compressor or fan outlet.

condenser constructed of concentric tubes in which the refrigerant circulates through the annular space and the cooling medium through the inner tube.

(1) desiccant or refrigeration device placed in the main air line of a pneumatic control system to reduce moisture. Compare to desiccant. See also dryer. (2) a device containing desiccant(s). It is used in the liquid line of a refrigerant system for the primary purpose of collecting and holding water that may have entered the system.

replacement refrigerant that has thermodynamic properties similar to one being replaced and does not require air conditioning or refrigerating equipment to be replaced but may require modifications.

process of heat removal by a refrigerant in an evaporator fed by a flow control device, responsive to temperature, pressure, or both at some point in the evaporator or to the difference between high- and low-side pressures and not to the liquid level in the evaporator. All entering refrigerant is evaporated before being recirculated. See direct-expansion (DX) refrigeration systems.

DX refrigerant evaporator with organized distribution from which the refrigerant exits at a vapor quality of one, usually with superheat. Compare to flooded evaporator.

continuous tube evaporator in which refrigerant from a pressure-reducing device is fed into one end and the suction line connects to the outlet end.

compression of refrigerant entering a single cylinder from two sources at different suction pressures.

compressor in which the cylinders have an additional suction inlet partway along the compression stroke which enables refrigerant to be drawn in at two different suction pressures.

upstream pressure regulator equipped with two controls, used in refrigerant suction lines to provide freeze-up protection or for safety pressure relief.

method of separation and automatic return of liquid refrigerant from an accumulator in the low side to the high side of the plant.

(also known as turbulator or turbulence promoter), device inserted in flooded evaporator tubes to prevent the evaporator from becoming oil bound or the refrigerant liquid from becoming quiescent at a pressure lower than its boiling point.

a system by which the supply air of a cooling system is cooled indirectly with a fluid that is itself cooled by heat or mass transfer to the environment without mechanical cooling. Examples of commonly used fluids are water, glycol mixtures, and refrigerants.

(1) overall efficiency. (2) ratio of the work absorbed in conveying and compressing a unit mass of refrigerant in a perfect compressor and the work absorbed, per unit mass of refrigerant, by the shaft of an actual compressor.

manually operated safety valve for discharge of refrigerant in case of fire or other emergency.

(1) general: piping arrangement to maintain a common liquid level or pressure between two or more chambers. (2) refrigeration: piping arrangement on an enclosed compressor to equalize refrigerant gas pressures in crankcase and suction, also a device for dividing the liquid refrigerant between parallel low side coils, also a piping arrangement to divide the lubricating oil between the crankcases of compressor operating in parallel or in tandem. (3) steam: piping arrangement to equalize steam header pressure and condensate return pressure in a steam boiler.

the water content of a liquid refrigerant after being in contact with a specific drier at a particular temperature long enough to reach an equilibrium state. EPD is expressed in milligrams of water per kilogram of refrigerant (ppm).

condenser in which the removal of heat from the refrigerant is achieved by the evaporation of water from the exterior of the condensing surface, induced by the forced circulation of air and sensible cooling by the air.

heat exchanger, usually of the shell-and-tube type, over which liquid refrigerant is dripped or sprayed and evaporated.

controlling device for automatically regulating the flow of refrigerant into a cooling unit, actuated by changes in evaporator pressure. The basic response is to regulate evaporator pressure.

refrigerating effect in watts, Btu/h, or tons (12,000 Btu/h) produced by the evaporation of refrigerant passed by the valve under specified conditions.

difference between the temperature of the external bulb and the corresponding system refrigerant saturation temperature at the bulb location.

(1) liquefied gas (generally liquid nitrogen) whose vapor is lost after change of phase. (2) solid carbon dioxide (dry ice).

refrigerant that is ignitable when mixed with air (e.g., ethyl chloride, methyl chloride, and the hydrocarbons). Note: see ASHRAE Standard 34 for flammability categories.

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

vessel located between compression stages where injected liquid refrigerant vaporizes immediately.

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.

refrigerant evaporator characterized by no organized flow, in which most of the evaporator surface is in contact with the liquid refrigerant, and from which the refrigerant exits at a vapor quality of one, without significant superheat. Compare to dry expansion evaporator.

(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.

any of a broad group of organic compounds analogous to hydrocarbons in which all or most of the hydrogen atoms of the hydrocarbon have been replaced by fluorine, some types also contain chlorine, and these are called chlorofluorocarbons. The saturated, aliphatic-type fluorocarbons comprise the series of refrigerants developed by Midgeley in the 1930s. Compare to halocarbon.

formation of a foam or froth of oil refrigerant due to rapid boiling out of the refrigerant dissolved in the oil when the pressure is suddenly reduced. See also boiler foaming.

pipe loop projecting from a refrigerant vessel indicating approximately the liquid level by the frost formation.

coating of frost on suction line and crankcase due to liquid refrigerant leaving an evaporator and carried along the suction line into the compressor crankcase.

the absolute value of the difference between the starting and ending temperatures of a phase-change process by a refrigerant within a component of a refrigerating system, exclusive of any subcooling or superheating. This term usually describes condensation or evaporation of a zeotrope.

organized evaporator with circulation induced by a static head of liquid refrigerant driving an opposing column of boiling refrigerant in the evaporator, sometimes referred to as a thermosiphon.

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.

coil that uses a heat transfer fluid, condensing refrigerant, or direct electrical resistance elements to provide heating to heat fluids (air, gas, or liquids).

as applied to refrigeration systems, this term refers to gage pressure at room temperature (74°F [23.3°C]) that is typically more that 100 psig (689 kPa gage). Common high-pressure refrigerants include R-22, R-502, R-404A, R-407A, R-407C, R-410A, and R-507A.

system whose gage pressure at room temperature (74°F [23.3°C]) is typically more than 100 psig (689 kPa). Common high-pressure refrigerants include R-22, R-502, and R-125.

(also known as service charge), reduced quantity of refrigerant or inert gas used to avoid the ingress of air and moisture into a component before start-up.

refrigerant gas in the high-pressure side of the system.

(also known as internal defrosting), method that utilizes heat from inside the pipes of the evaporator, usually the highly superheated vaporized refrigerant from the compressor.

internal pressure stress in piping or vessels due to a temperature rise in liquids (such as refrigerants, water, or secondary coolants) when the containment volume is completely filled with liquid.

system in which a liquid such as brine or water, cooled by the refrigerant, is circulated to the material or space to be refrigerated or is used to cool air so circulated.

refrigerating system in which secondary coolant, cooled by a refrigerant, is circulated to the material or space to be cooled or is used to heat or cool circulated air.

a combined appliance where refrigerant tubing is inserted directly into the water heater, usually through one of the ports on the water heater, the inserted tubing is the desuperheater.

percentage increase in the length of a test specimen, usually an elastomer, as a result of exposure to refrigerants or oils.

the concentration (mass percent) of components present in the liquid phase of a refrigerant blend that is in equilibrium with its vapor phase.

(1) a factory-made assembly of elements in which the heat is transferred from the liquid to the refrigerant, causing the refrigerant to evaporate and the liquid to be cooled. (2) heat exchanger designed to cool liquids.

tube or pipe carrying the refrigerant liquid from the condenser or receiver of a refrigerating system to a pressure-reducing device.

system feeding an evaporator with refrigerant at a rate to make the exit vapor quality less than one.

(also known as liquid circulation), evaporator feed system whereby refrigerant liquid is flashed to saturated suction pressure and temperature in an accumulator and is then fed by a mechanical pump or by refrigerant vapor pressure to the evaporators. This liquid is normally fed at a rate greater than the evaporation rate for the refrigerant to ensure wetting of the entire evaporator surface for better heat transfer.

(also known as liquid slug), accidental trapping of liquid refrigerant at any point in the system.

a vessel, permanently connected to a refrigerating system by inlet and outlet pipes, for storage of liquid refrigerant.

a sample taken from the liquid phase of a refrigerant blend.

device for collecting liquid refrigerant at a given point in a refrigerating circuit.

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

a filter containing a desiccant capable of removing moisture and other dissolved contaminants in the refrigerant stream.

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.

an absorption system where water (R-718) is the refrigerant and lithium bromide (LiBr) is the absorbent.

(1) device that is capable of discerning the loss of refrigerant charge in a refrigerating machine and of reacting to protect the apparatus from motor burnout. (2) splitting of a condensate line to permit vapors to pass above and condensate to pass below an obstruction.

(1) electric switch and pressure-responsive element connected into the suction side of a refrigerating system to control the operation of the system. (2) pressure-responsive device actuated directly by refrigerant vapor pressure in the low side.

(1) sometimes referred to as an accumulator or surge drum, this vessel acts as the separator for the mixture of vapor and liquid returning from the evaporators, the constant refrigerant level is usually maintained by control devices. (2) vessel on the low side of a refrigerating system into which liquid refrigerant can be collected and used to supply evaporators.

system whose gage pressure at room temperature (74°F [23.3°C]) is near or less than atmospheric pressure. Common low-pressure refrigerants include R-11 and R-123.

the ratio of the mass of lubricant circulating through a refrigerant system to the total mass of refrigerant and lubricant flowing through the system at a specified set of operating conditions.

hand-operated, needle-type valve for controlling the flow of liquid refrigerant to an evaporator.

maximum amount of refrigerant to be packaged in a shipping container for safe transportation as defined by U.S. Department of Transportation.

the difference between the saturated liquid temperature (bubble point) and the saturated vapor temperature (dew point) for the \"as-formulated\" blend composition at constant pressure. For a given pressure, the evaporator temperature glide in a direct-expansion system will typically be 70% to 80% of the maximum temperature glide (as the refrigerant blend entering the evaporator is a mixture of liquid and vapor) and not at the saturated liquid temperature of the “as-formulated” blend composition.

refrigerating system using mechanical compression to move the refrigerant from the low-pressure side and to deliver it to the high-pressure side of the system.

system whose gage pressure at room temperature (74°F [23.3°C]) is greater than atmospheric pressure but typically less than 100 psig (689 kPa). Common medium pressure refrigerants include R-12, R-500, and R 134a.

allowing refrigerant to pass through two or more expansion valves in series with each other.

system in which compression of refrigerant is carried out in two or more steps.

(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.

the bulk manufactured composition of the refrigerant blend, which includes the gas and liquid phases.

one that remains a liquid during the process of absorbing heat within the air cooler. See secondary coolant (secondary fluid).

(1) method of defrosting in which the temperature of the evaporator coils is allowed to rise naturally during an off-cycle, during which no refrigerant is supplied. (2) rapid heating of the evaporator coil during the off part of each cycle.

a heat exchanger that can be cooled by air, brine, water, or refrigerant vaporization to cool oil in a lubrication system.

transfer of heat from oil in a pipe or tubing to a refrigerant or brine.

(also known as oil still), apparatus for purifying oil by vaporizing the refrigerant contained.

removal of oil or oil vapor from a refrigerant vapor.

a device for separating oil and oil vapor from the refrigerant, usually installed in the compressor discharge line.

a device to separate oil from refrigerant by a distillation process.

the ratio of the mass of lubricant circulating through a refrigerant system to the total mass of refrigerant and lubricant flowing through the system at a specified set of operating conditions.

refrigerant compressor with a shaft or other moving part extending through its casing to be driven by an outside source of power, thus requiring a shaft seal or equivalent rubbing contact between fixed and moving parts.

charge achieving maximum possible refrigerant effect within design limitations.

a numerical quantity describing the extent of ozone depletion calculated to arise from the release to the atmosphere of one kilogram (2.2046 lb) of a compound relative to the ozone depletion calculated to arise from a similar release of the refrigerant R-11. The calculation is an integration of all known potential effects on ozone over the whole time that any portion of the compound could remain in the atmosphere.

the capacity of the permanent bleed provision, expressed either as a percentage of the nominal capacity or in kW (Btu/h or tons) of refrigerating effect produced by the evaporation of that amount of refrigerant flow.

evaporator consisting of two plates containing channels for the circulation of refrigerant or a set of tubes connected to and between the two plates.

(1) air-cooled condenser consisting of plates between which are arranged channels for the circulation of refrigerant. (2) water-cooled condenser consisting of a coil through which the refrigerant circulates, arranged between two plates, with water circulating between coil and plates.

(1) difference in pressure between two points in a flow system, usually caused by frictional resistance to fluid flow in a conduit, filter, or other flow system. Compare to pressure loss. (2) loss in pressure, as from one end of a refrigerant line to the other, from friction, static, heat, etc.

any device or portion of the equipment used to increase refrigerant pressure.

(1) any refrigerant-containing receptacle in a refrigerating system. This does not include evaporators where each separate evaporator section does not exceed 0.5 ft3 (0.014 m3) of refrigerant-containing volume regardless of the maximum inside dimension. This also does not include evaporator coils, compressors, condenser coils, controls, headers, pumps, and piping. (2) container for fluids at a pressure different from atmospheric pressure (vacuum to high), capable of withstanding associated stresses.

a refrigerant pressure-control system that prevents refrigerant loss and infiltration into idle low-pressure chillers and is also used to pressurize for leak testing without the use of noncondensables.

a refrigerant pressure control system that prevents refrigerant loss and infiltration into idle low-pressure chillers and is also used to pressurize for leak testing without the use of noncondensables.

working fluid of a refrigerating cycle (as opposed to secondary refrigerant).

of refrigerant, withdrawal of all refrigerant from the low side of a system by pumping it to either the condenser or the liquid receiver.

the quantity of refrigerant stored at some point in the refrigeration system for operational, service, or standby purposes.

(also known as purger), system used to recover refrigerant from purged mixture of gases and water.

an automatic, semiautomatic, or hand-operated device that collects gases from the condenser or receiver, condenses the condensable refrigerant therefrom, and releases the remainder to the atmosphere.

a vessel in the refrigerating system designed to ensure the availability of adequate liquid refrigerant for proper functioning of the system and to store the liquid refrigerant when the system is pumped down.

to process used refrigerant to new product specifications.

refrigerants reprocessed to the same specifications as new refrigerants by any means, including distillation. Such refrigerants have been chemically analyzed to verify that those specifications have been met.

to remove refrigerant in any condition from a system and store it in an external container.

refrigerants removed from a system in any condition without necessarily testing or processing them.

a machine that removes refrigerant from a refrigerating system, preventing refrigerant discharge to the environment.

(1) externally cooled heat exchanger in the high side of a refrigerating absorption system for condensing absorbent and separating it from the refrigerant before passing it to the condenser. (2) in electricity, a device for converting AC to DC current.

to reduce contaminants in used refrigerants by separating oil, removing noncondensables, and using devices such as filter driers to reduce moisture, acidity, and particulate matter.

refrigerants for which contaminants have been reduced by oil separation, removal of noncondensable gases, and single or multiple passes through filter driers or other devices that reduce moisture, acidity, and particulate matter.

the fluid used for heat transfer in a refrigerating system, which absorbs heat at a low temperature and a low pressure of the fluid and rejects heat at a higher temperature and a higher pressure of the fluid, usually involving changes of the state of the fluid.

a refrigerant composed of two or more different chemical compounds often used individually as refrigerants for other applications.

(1) actual amount of refrigerant in a closed system. (2) weight of refrigerant required for proper functioning of a closed system.

an assembly of refrigerant-containing parts connected to allow the flow of refrigerant in the refrigerating cycle. The refrigerant-containing parts are considered part of the circuit even if isolated by a valve. A system or equipment may be considered to have multiple circuits only if there is no intended path for the refrigerant to cross over from circuit to circuit.

device used in conjunction with a thermostatic expansion valve to ensure equable refrigerant distribution from the valve to individual parallel sections of an evaporator.

total useful capacity of a refrigerant condenser for removing heat from the refrigerant circulated through it.

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

the mass flow rate of the volatile refrigerant, which is potentially mixed with lubricant.

device that controls the flow of liquid refrigerant to an evaporator.

device or portion of equipment used for the purpose of increasing refrigerant pressure.

recirculates liquid refrigerant from the refrigerant sump at the bottom of the evaporator to the evaporator tube bundle in order to effectively wet the outside surface and enhance heat transfer (when used).

dedicated apparatus for transfer of refrigerant from a chiller or other refrigerating system to a separate and distinct storage vessel.

vessel in a refrigerating system designed to ensure the availability of adequate liquid refrigerant for proper functioning of the system and to store the liquid refrigerant when the system is pumped down.

a machine that removes refrigerant from a refrigerating system, preventing refrigerant discharge to the environment.

any movement of refrigerant out of its containment and into the atmosphere, including, but not limited to, movement by a leak, by an action of filling or testing, or by failure.

heat exchanger, after the condenser, for subcooling the condensed refrigerant.

process of cooling refrigerant below condensing temperature for a given pressure, also, cooling a liquid below its freezing point where it can exist only in a state of unstable equilibrium. See supercooling.

interconnected parts forming a closed circuit in which refrigerant is circulated and having the condenser located to transfer heat to the zone to be heated.

refrigerating systems are classified according to the degree of probability, low or high, that leaked refrigerant from a failed connection, seal, or component could enter an occupied area. The distinction is based on the basic design or location of the components.

assembly of refrigerant-containing parts used in a refrigerating cycle.

any movement of refrigerant out of its containment, including, but not limited to, by a leak, by an action of filling or testing, or by failure.

system in which the refrigerant vapor is not condensed to a pure liquid but is absorbed in a weak solution from which it is subsequently evaporated at a lower temperature to produce refrigeration.

density of refrigerant, kg/m³ [lbm/ft³]

evaporator consisting of two metal plates that are weld bonded together (with the exception of the printed circuit forming the refrigerant passage, which is obtained by inflation under pressure).

the saturation temperature corresponding to the measured refrigerant pressure at the condenser inlet for single component and azeotropic refrigerants, and the arithmetic average of the refrigerant dew-point temperature and the bubblepoint temperature corresponding to the refrigerant pressure at the condenser entrance for zeotropic refrigerants.

in a refrigeration system, an arrangement for gravitational separation of the larger impurities from a refrigerant.

hermetic unit with compressor and motor enclosed in the same housing without external shaft or shaft seals with the motor operating in the refrigerant.

(1) a volatile refrigerant (usually a single refrigerant or an azeotropic mixture) of known properties that is used as a heating medium. (2) volatile or nonvolatile substance in an indirect refrigerating system that absorbs heat from a substance in space to be refrigerated and transfers this heat to the evaporator of the refrigerating system.

a complete, factory-assembled and factory-tested system that is shipped in one or more sections and has no refrigerant-containing parts that are joined in the field by other than companion or block valves.

condenser in which the cooling medium circulates in a coil located in a shell containing the condensing refrigerant.

evaporator in which the fluid to be cooled is passed through the tubes, which are immersed in the refrigerant.

effect produced by droplets of liquid refrigerant or oil, or a mixture of both, that reach the cylinder of a compressor.

a factory-charged refrigerating system using less than 5 lb (2.3 kg) of refrigerant that is welded, brazed, soldered, or otherwise joined together in such a manner as to create a sealed system typically capable of operating for 10 years without maintenance or repair.

an absorbent or adsorbent medium that remains completely or substantially in a single phase during the process of absorbing or releasing heat by means of a refrigerant. Such media include liquids and solids.

an operating mode that occurs during space cooling when either the refrigerant-to-water heat exchanger water pump has automatically cycled off or the rate of heat transfer to the domestic water has become negligible. With respect to seasonal performance calculations, this mode occurs when the water-heating load is satisfied but a space cooling load remains.

an operating mode that occurs during space heating when either the refrigerant-to-water heat exchanger water pump has automatically cycled off or the rate of heat transfer to the domestic water has become negligible. With respect to seasonal performance calculations, this mode occurs when the water-heating load is satisfied but a space heating load remains.

the refrigerant flow rate in lb/min (g/s) required to produce one ton (one kW) of refrigeration.

air-conditioning system consisting of equipment provided in more than one assembly or enclosure, usually with supply air-distribution equipment housed separately from refrigerant-condensing equipment.

(1) shell-and-tube evaporator in which the tubes are sprayed by liquid refrigerant. (2) starved evaporator condition when an evaporator does not receive sufficient refrigerant.

solvent with a relatively high concentration of dissolved refrigerant.

a heat exchanger for cooling liquid refrigerant below its condensing temperature at a given pressure.

total refrigerant heat rejection effect less the condensing heat rejection effect.

additional refrigeration effect made available by subcooling the refrigerant liquid in the condenser.

(1) tube or pipe that carries the refrigerant vapor from the evaporator to the compressor inlet. (2) tube or pipe that connects any line from a store to the suction side of a pump.

(1) fan/pump: the pressure generated on the inlet or intake side of a fan or pump. (2) refrigeration: the intake pressure generated by the system compressor while operating. The suction pressure, along with the suction temperature, the pressure, and the wet-bulb temperature of the discharge air, are used to determine the correct refrigerant charge in the system. It is also called low-side pressure.

the temperature of the refrigerant vapor returning to the compressor or condensing unit.

(1) at a defined pressure, the difference between a given vapor temperature and the dew-point temperature. (2) the difference in temperature between the saturation temperature corresponding to the measured outlet pressure and the measured outlet temperature of the refrigerant vapor leaving the heat exchanger.

rate of heat removal by the refrigerant in the evaporator of a refrigerating system.

a tube, or coils with interconnecting piping, placed in supply and exhaust airstreams and filled with a refrigerant heat transfer fluid.

a device for controlling superheat by regulating the mass flow of refrigerant to a refrigeration load, actuated by changes in equalizer pressure and temperature sensing element temperature.

any air conditioner or heat pump that has three major assemblies separated from each other. The compressor would be in a first assembly, with one refrigerant heat exchanger in a second assembly, and the second refrigerant heat exchanger in a third assembly.

(1) the time-weighted average concentration for a normal 8 hworkday and a 40 h workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect. (2) the refrigerant concentration in air for a normal 8 h workday and a 40 h workweek to which repeated exposure, day after day, will not cause an adverse effect in most persons.

total useful capacity of a refrigerant condenser for removing heat from the refrigerant circulated through it.

(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 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.

(plate evaporator), evaporator constructed from a pair of plates assembled to form a shallow compartment containing a coil through which refrigerant flows, with the fluid to be cooled circulating in the compartment.

(plate coil), type of extended surface evaporator consisting of one or several metal sheets with a coil through which refrigerant flows, brazed to one face.

any air conditioner or heat pump that has two major assemblies separated from each other with both assemblies being indoor. The compressor and one refrigerant heat exchanger would be in one assembly, with the other refrigerant heat exchanger in a second assembly.

any air conditioner or heat pump that has two major assemblies separated from each other between indoor and outdoor. The compressor and one refrigerant heat exchanger would be in one assembly, with the other refrigerant heat exchanger in a second assembly.

rate at which heat is removed by the primary refrigerant, or by the secondary refrigerant, between two specified points, taking into account the conditions of use.

(1) gas, particularly one near equilibrium with its liquid phase and one that does not follow the gas laws. The term is usually used instead of gas to refer to a refrigerant, or in general, to any gas below the critical temperature. (2) substance in the gaseous state that can also exist as a liquid or solid at normal atmospheric conditions. Compare to gas.

the concentrations (mass percentages) of components present in the vapor phase of a refrigerant blend that is in equilibrium with its liquid phase.

refrigerating cycle using an ejector to compress the refrigerant vapor from the evaporator to the condenser. The term steam jet is used when water is the refrigerant.

orifice capillary tube, or other device having a restricted passage of fixed size for liquid refrigerant. It restricts flow of vapor of that same liquid to a lower rate of flow with the same pressure difference.

system using a condensable vapor as the refrigerant.

a sample taken from the vapor phase of a refrigerant blend.

an engineered direct-expansion (DX) multisplit system incorporating at least one variable capacity compressor distributing refrigerant through a piping network to multiple indoor fan-coil units, each capable of individual zone temperature control, through integral zone temperature control devices and common communications network. Variable refrigerant flow utilizes three or more steps of control on common, interconnecting piping.

an engineered direct expansion (DX) multisplit system incorporating at least one variable capacity compressor distributing refrigerant through a piping network to multiple indoor fan-coil units, each capable of individual zone temperature control, through integral zone temperature control devices and common communications network. Variable refrigerant flow uses three or more steps of control on common, interconnecting piping.

a refrigerant that changes from the liquid to the vapor state in the process of absorbing heat.

uses a vacuum to boil water at the temperature desired, one in which evaporating water vapor is the refrigerant.

in petroleum oils, a material, usually a solid hydrocarbon, that may separate on cooling of an oil refrigerant mixture.

system of refrigeration in which some liquid refrigerant is mixed with vapor entering the compressor to cause the discharge vapor from the compressor to be saturated, rather than superheated.

a zeotropic refrigerant contains two or more components whose equilibrium vapor phase and liquid phase compositions differ. The temperature of a zeotropic refrigerant changes as it evaporates or condenses at constant pressure (Compare to azeotropic refrigerant).