ASHRAE Terminology

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).

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.

an automatic valve located between the evaporator outlet and the compressor inlet that responds to its own inlet pressure to prevent the evaporator pressure from falling below a selected value.

(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 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.

(1) direct-expansion chillers are complete refrigerating systems consisting of a compressor, condenser, and evaporator with all operating and safety controls. Compressor types include the following: reciprocating, centrifugal, or screw design. Compare to absorption chiller. (2) refrigerating machine used to transfer heat between fluids. Chillers are either direct expansion with a compressor or absorption type.

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.

the heat exchanger that rejects heat to (cooling) or absorbs heat from (heating) a source external to the conditioned space. In the cooling mode, the coil operates as a condenser. In the heating mode, the coil operates as an evaporator.

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).

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.

transport of oil from the evaporator to the compressor.

a unitary air conditioner, for a computer and data processing room, consisting of one or more assemblies that include a DX evaporator or chilled-water cooling coil, an air-moving device, and air-filtering devices. The air conditioner may include a compressor, condenser, humidifier, or reheating device.

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.

act of controlling the refrigerating cycle or heating cycle to periodically melt the unacceptable accumulation of ice on evaporator tubes, windows, etc.

(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.

vessel or tray placed under an evaporator coil or cooling coil to receive condensed moisture, melted frost, or ice. Also called a drip tray or a defrost pan.

additional length of pipe or coil added to a direct-expansion evaporator in order to provide superheat at the thermostatic expansion valve sensing bulb without using evaporator tubing.

(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.

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.

(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.

see plate evaporator.

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.

receiver fitted between the compressor suction line and the return lines of several evaporators in parallel.

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

ability of an evaporator to stay cold after evaporation stops.

automatic valve or control device used to maintain the pressure, and thereby the temperature, in an evaporator above a predetermined minimum.

assembly of refrigerating compressor, evaporator, and necessary accessories attached to one base.

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.

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.

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.

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.

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.

total rate of heat removal from all sources by the evaporator of a refrigerating system at stated conditions. It is numerically equal to the system refrigerating effect.

thermodynamic heating/refrigerating system to transfer heat. The condenser and evaporator may change roles to transfer heat in either direction. By receiving the flow of air or other fluid, a heat pump is used to cool or heat. Heat pumps may be the air source with heat transfer between the indoor air stream to outdoor air or water source with heat transfer between the indoor air stream and a hydronic source (ground loop, evaporative cooler, cooling tower, or domestic water).

evaporator in which the tubes, arranged in the vertical plane, are bent in the form of a V.

solenoid valve located in a bypass line running from the outlet of the compressor to the evaporator.

(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.

a line used to convey discharge gas from the compressor to the evaporator for the purpose of defrosting.

water cooler in which ice is allowed to collect on the evaporator tubes.

evaporator immersed in water. Ice will form on evaporator.

water-cooling tank in which ice is allowed to build up on the evaporator tubes to provide a reserve for cooling.

connection between the pumping unit outlet and the evaporator inlet.

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.

(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.

(1) low side or suction side. (2) portion of a refrigerating system operating at approximately the evaporator pressure.

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

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.

an encased, factory-made assembly or assemblies designed to be used as permanently installed equipment to provide conditioned air to an enclosed space(s). It normally includes multiple evaporators, compressor(s), and condenser(s). Such equipment may be provided in more than one assembly, the separated assemblies of which are intended to be used together.

(1) a plan for gathering of relevant measurement data over time to evaluate equipment or system performance. The plan defines specific M&V methods to be used, including baseline determination, performance period measurements, savings verification calculations, and acceptance criteria. The M&V methods chosen are consistent with the current facility requirements (CFR). During the implementation phase, a list is developed of specific instrumentation and data-gathering equipment that must be maintained at the site. During the hand-off phase, the type, frequency, and distribution of M&V reports to be submitted for approval is confirmed. (2) equipment to measure and record the parameters of the HVAC&R systems (i.e., temperature, humidity, pressure, electric current, kW, and volts). (3) gathering of relevant measurement data over time to evaluate equipment or system performance (e.g., chiller electric demand, inlet evaporator temperature and flow, outlet evaporator temperature, condenser inlet temperature, and ambient dry-bulb temperature and relative humidity or wet-bulb temperature, for use in developing a chiller performance map (e.g., kW/ton versus cooling load and versus condenser inlet temperature).

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.

(1) system in which all the refrigerated surfaces in the cabinet are defrosted by an automatic defrost system. (2) use of a secondary coolant sprayed on evaporator surfaces to prevent formation of frost, water absorbed in the coolant is removed by distillation.

located in the absorber tube bundle or external to the absorber/evaporator vessel.

(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.

migration of oil from the evaporator to the crankcase of the compressor. See compressor oil return.

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) 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.

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

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

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).

a system that, in operation between a heat source (evaporator) and a heat sink (condenser) at two different temperatures, absorbs heat from the heat source at the lower temperature and rejects heat to the heat sink at the higher temperature. See also refrigerating unit.

unit assembly composed of a compressor, evaporator, condenser, and expansion device, used for refrigerating and for extracting heat.

parts subjected to approximately the evaporator pressure.

refrigerating equipment forming a part of the refrigerating system, including any or all of the following: compressor, condenser, generator, absorber (adsorber), liquid receiver, connecting piping, and evaporator.

defrosting an evaporator by reversing its function with that of the condenser.

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).

condenser cooled by the evaporator of a secondary system.

(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.

closed, cylindrical shell containing an evaporator coil which is in contact with the liquid to be cooled.

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

compression from evaporator to condenser pressure by passing through one compressor stage only.

(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.

system in which high-pressure steam, supplied through a nozzle and acting to eject water vapor from the evaporator, maintains the requisite low pressure on one side and produces a high pressure on the other by virtue of compression in a following diffusion passage. Sometimes called an ejector cycle refrigerating system.

factory assembled refrigerating system mounted at high level in the insulated wall of a cold store with the evaporator inside the store and the rest of the unit outside.

(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.

accumulator installed in the suction line between evaporator and compressor to trap liquid carryover from the evaporator and to prevent it from reaching the compressor.

(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.

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

the part of the expansion valve that senses the temperature at the superheat control point, normally located at the outlet of the evaporator. This element may be remote or integral to the expansion valve body.

evaporator pressure regulator that is sensitive to temperature.

(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.

one or more factory-made assemblies that normally include an evaporator or cooling coil and a compressor and condenser combination.

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.

(1) in a refrigeration system, where the connections between the evaporator outlets and the low pressure receiver through which the mixture of vapor and overfeed liquid is drawn. (2) in a steam system, where a return pipe carries condensate, the pipe is usually located below the level of the waterline in the boiler.