ANSI ASHRAE 41.6-2014 Standard Method for Humidity Measurement.pdf

1、ANSI/ASHRAE Standard 41.6-2014(Supersedes ANSI/ASHRAE Standard 41.6-1994 RA 2006)Standard Method forHumidity MeasurementApproved by the ASHRAE Standards Committee on June 28, 2014; by the ASHRAE Board of Directors on July 2, 2014; and by theAmerican National Standards Institute on July 3, 2014.ASHRA

2、E Standards are scheduled to be updated on a five-year cycle; the date following the standard number is the year ofASHRAE Board of Directors approval. The latest edition of an ASHRAE Standard may be purchased on the ASHRAE website(www.ashrae.org) or from ASHRAE Customer Service, 1791 Tullie Circle,

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4、is a national voluntary consensus standard developed under the auspices of ASHRAE.Consensus is defined by the American National Standards Institute (ANSI), of which ASHRAE is a member and which has approved thisstandard as an ANS, as “substantial agreement reached by directly and materially affected

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12、ce to them is completely voluntary.In referring to this Standard or Guideline and in marking of equipment and in advertising, no claim shall be made, either stated or implied,that the product has been approved by ASHRAE.ASHRAE Standing Standard Project Committee 41CognizantTC:TC 1.2, Instruments and

13、 MeasurementSPLS Liaison: John F. DunlapMark Kedzierski, Chair* Alexander Leyderman*Richard L. Hall, Vice Chair* Kevin Peck*Patrick E. Collins, 41.6 Subcommittee Chair* James SchaeferErik S. Anderson* John Scott*Shane J Angle* Michael E. ShowsB. Terry Beck* Frank J. Spevak*John Buetow Michael A. Weg

14、enka*James L. Douglas* Charles C. Wright*Denotes members of voting status when the document was approved for publicationASHRAE STANDARDS COMMITTEE 20132014William F. Walter, Chair David R. Conover Malcolm D. KnightRichard L. Hall, Vice-Chair John F. Dunlap Rick A. LarsonKarim Amrane James W. Earley,

15、 Jr. Mark P. ModeraJoseph R. Anderson Steven J. Emmerich Cyrus H. NasseriJames Dale Aswegan Julie M. Ferguson Janice C. PetersonCharles S. Barnaby Krishnan Gowri Heather L. PlattSteven F. Bruning Cecily M. Grzywacz Douglas T. ReindlJohn A. Clark Rita M. Harrold Julia A. Keen, BOD ExOWaller S. Clemen

16、ts Adam W. Hinge Thomas E. Werkema, Jr., CODebra H. KennoyStephanie C. Reiniche, Manager of StandardsCONTENTSANSI/ASHRAE Standard 41.6-2014,Standard Method for Humidity MeasurementSECTION PAGEForeword .21 Purpose.22 Scope23 Definitions .24 Classifications .35 Requirements46 Instruments and Calibrati

17、on 57 Humidity Measurement Methods 68 Uncertainty Analysis159 Test Report .1510 Normative References.15Informative Appendix A: Bibliography .16Informative Appendix B: Example of an Uncertainty Estimate for the Humidity RatioUsing an RH Sensor, Dry-Bulb RTD, and Barometric Sensor.17Informative Append

18、ix C: Example of an Uncertainty Estimate for the Humidity RatioUsing a Wet-Bulb RTD RH Sensor, Dry-Bulb RTD, and Barometric Sensor.19Informative Appendix D: Example of an Uncertainty Estimate for the Humidity RatioUsing a Dew-Point Sensor, Dry-Bulb RTD, and Barometric Sensor21NOTEApproved addenda, e

19、rrata, or interpretations for this standard can be downloaded free of charge from the ASHRAEWeb site at www.ashrae.org/technology. 2014 ASHRAE1791 Tullie Circle NE Atlanta, GA 30329 www.ashrae.org All rights reserved.ASHRAE is a registered trademark of the American Society of Heating, Refrigerating

20、and Air-Conditioning Engineers, Inc.ANSI is a registered trademark of the American National Standards Institute.2 ANSI/ASHRAE Standard 41.6-2014(This foreword is not part of this standard. It is merelyinformative and does not contain requirements necessaryfor conformance to the standard. It has not

21、been pro-cessed according to the ANSI requirements for a standardand may contain material that has not been subject topublic review or a consensus process. Unresolved objec-tors on informative material are not offered the right toappeal at ASHRAE or ANSI.)FOREWORDThe 2014 revision represents a signi

22、ficant update toASHRAE Standard 41.6, which was last published in 1994(RA 2006). A change results from the completion of ASHRAEresearch project RP-1460, “Design Specifications for Wet-Bulb Aspirator Apparatus.” The aspirated wet-bulb psy-chrometer descriptions are no longer included in ASHRAEStandar

23、d 41.1-2013,Standard Methods for Temperature Mea-surement.Additional updates include the removal of moist-airproperties calculations, the inclusion of uncertainty analysisfor humidity measurements, and changes to bring the stan-dard into compliance with ASHRAEs mandatory languageand SI (I-P) units r

24、equirements. The standard has also beenarranged consistent with recently published ASHRAE Stan-dard 41-series standards, which include a classifications sec-tion and updated definitions and references.1. PURPOSEThis standard prescribes methods for measuring the humidityof moist air with instruments.

25、2. SCOPE2.1 This standard applies to the measurement of humidity ofmoist air from sea level to 3048 m (10,000 ft), within the dry-bulb temperature range of 50C to 160C (58F to 320F),and within the dew-point temperature range of 50C to 99C(58F to 210F).2.2 This standard applies to methods for the dir

26、ect measure-ment of wet-bulb temperature, dew-point temperature, rela-tive humidity (RH), and humidity ratio.2.3 This standard requires determining the uncertainty ofdirect humidity measurements due to various sources oferrors.3. DEFINITIONSabsolute humidity: in a mixture of water vapor and dry air,

27、the mass of water vapor in a specific volume of the mixture.accuracy: the degree of conformity of an indicated value toan accepted standard value, or true value. The degree of inac-curacy is known as total measurement error and is the sum ofbias error and precision error.adiabatic saturation tempera

28、ture: the saturation temperatureto which moist air is adiabatically cooled by evaporation ofwater at the same temperature into the moist air. Also referredto as thermodynamic wet-bulb, this is the temperature plottedon a psychrometric chart and is used for the calculation ofmoist-air properties.dew-

29、point temperature: temperature at which water vaporhas reached the saturation point (100% rh).error: the difference between the true value of the quantitymeasured and an observed value. Since the true value is oftennot known, it is estimated by the mean. The differencebetween the mean and an observe

30、d value is often called itsdeviation.fixed, bias, or systematic error: the difference between thetrue or actual value to be measured and the indicated valuefrom the measuring system that persists and is usually due tothe particular instrument or technique of measurement.frost point: the temperature

31、at which visible frost forms on asurface being chilled.hygrometer: an instrument responsive to relative humidityin this standard, relative humidity in the atmosphere.mixing (humidity) ratio: the ratio of the mass of water vaporto the mass of dry air.precision: the closeness of agreement among repeat

32、ed mea-surements of the same characteristic by the same methodunder the same conditions.psychrometer: An instrument used to determine the humidityof air by simultaneously measuring both the wet-bulb anddry-bulb temperatures. The difference between these temper-atures is referred to as the wet-bulb d

33、epression.random error (or precision error): a statistical error that iscaused by chance and is not recurring. There are two types ofrandom errors:additive errors, which are independent of the magni-tude of the observationsmultiplicative errors, which are dependent on themagnitude of the observation

34、s.relative humidity:a. ratio of the partial pressure or density of water vaporto the saturation pressure or density, respectively, atthe same dry-bulb temperature, and barometric pres-sure of the ambient air.b. ratio of the mole fraction of water vapor to the molefraction of water vapor saturated at

35、 the same temper-ature and barometric pressure.repeatability: the closeness of agreement among repeatedmeasurements of the same characteristic under the same con-ditions by the same instrument.sensitivity: the relationship between an observed change inthe position of an instrument pen, pointer, or i

36、ndicator and themagnitude of change in the measured quantity required toproduce that reaction of the indicator. It is expressed as anumerical ratio if the units of measurement of the two quanti-ties are stated. An increase in sensitivity means a correspond-ing increase in the ability of an instrumen

37、t to react toextremely small changes in the measured quantity.specific humidity: ratio of the mass of water to the total massof a moist air sample.ANSI/ASHRAE Standard 41.6-2014 3steady-state conditions: an operation where at least three suc-cessive data points obtained at each set of specified cond

38、i-tions are neither successively increasing nor successivelydecreasing.temperature depression: the difference between the readingsof the wet-bulb and dry-bulb temperature sensor; also referredto as wet-bulb temperature depression.temperature, dry-bulb: the temperature of a gas or mixture ofgases ind

39、icated by an accurate temperature sensor after cor-rection for radiation.temperature, wet-bulb: the temperature at which liquid orsolid water, by evaporating into air, brings the air to saturationadiabatically at the same temperature. Wet-bulb temperature(without qualification) is the temperature in

40、dicated by a wet-bulb psychrometer constructed and used according to specifi-cations.The true wet-bulb temperature is the temperature reachedby a wet-bulb sensor exposed to a stream of moist air in theabsence of any external parasitic heat transfer not related toconvection. The true wet-bulb tempera

41、ture found using thisapproach is the temperature at which the convective heat gaindirectly balances out the evaporative heat loss of the sensor.thermodynamic wet-bulb temperature: see adiabatic satura-tion temperature.transducer: a device that changes one form of physical quan-tity into another. In

42、the measurement field, transducers areused to sense a variety of measurands, such as line voltage,current, power, pressure, and temperature, and to convertthese to a common output signal for use with a controlling orrecording instrument.transient condition: the state in which the system undergoesa c

43、hange in operation, such as thermostat cycling or actuationof a defrost control.uncertainty: a measure of the potential error in a measure-ment or experimental result that reflects the lack of confi-dence in the result to a specified level.4. CLASSIFICATIONS4.1 Humidity measurements shall be made wi

44、th an instru-ment or instrument system, including readout devices, meet-ing the accuracy and precision requirements in the test plan.4.2 Whenever two humidity-measuring instruments are usedto measure a humidity difference, or change, of less than10C (18F) dew-point temperature, the investigator shal

45、l rec-ognize the effect of individual instrument accuracies on theaccuracy of the calculated temperature difference.4.3 Humidity-sensing methods that are within the scope ofthis standard include, but are not limited to, the methodslisted below, which are described in Section 7.a. Chilled-mirror (con

46、densate type) dew-point sensorsb. Aspirated wet-bulb psychrometerc. Polymer film electronic hygrometerd. Aluminum oxide hygrometere. Porous ceramic electronic hygrometerf. Silicon sensor hygrometerg. Dunmore-type hygrometerh. Electrolytic hygrometeri. Ion exchange resin electric hygrometerj. Spectro

47、scopic (infrared/ultraviolet) hygrometerk. Piezoelectric sorption hygrometer4.4 National Institute of Standards and Technology Grav-imetric Hygrometer. The current state of the art in a preci-sion humidity instrument is the gravimetric hygrometerdeveloped and maintained by the National Institute of

48、Stan-dards and Technology (NIST). The gravimetric hygrometeryields a determination of absolute water vapor content, sincethe weight of the water absorbed and the precise measure-ment of the gas volume associated with the water vapor deter-mine the absolute humidity of the incoming air.In this system

49、, the test gas flows from a humidity genera-tor through a drying train and into a precision gas-volume-mea-suring system contained within a temperature-controlled bath.The precise measurements of the mass of water vapor absorbedfrom the test gas and the associated volume of dry gas, as mea-sured at controlled temperatures and pressures (which allowscomputation of the mass of dry gas associated with the col-lected mass of water), accurately define the mixing (humidity)ratio of the test gas or any other expression of humidity. Whenemployed as a calibration