BS 1339-1-2002 Humidity - Terms definitions and formulae《湿度 术语、定义和公式》.pdf

1、BRITISH STANDARD BS 1339-1: 2002 Incorporating Corrigendum No. 1 Humidity Part 1: Terms, definitions and formulae ICS 01.040.13 BS 1339-1:2002 This British Standard, having been prepared under the direction of the Materials and Chemicals Sector Policy and Strategy Committee, was published under the

2、authority of the Standards Policy and Strategy Committee on 02 August 2002 BSI 24 October 2002 First published April 1965 Published as Part 1 29 July 2002 The following BSI references relate to the work on this standard: Committee reference CPI/29 Draft for comment 97/126683 DC ISBN 0 580 38475 6 Co

3、mmittees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee CPI/29, Humidity and temperature conditioning requirements, upon which the following bodies were represented: British Compressed Gases Association Institution of Chemical Engi

4、neers Institute of Measurement and Control Institute of Printing National Physical Laboratory SIRA Society of Environmental Engineers Amendments issued since publication Amd. No. Date Comments 14209 Corrigendum No. 1 24 October 2002 Corrections to equation (1) and equation (20)BS 1339-1:2002 BSI 24

5、October 2002 i Contents Page Committees responsible Inside front cover Foreword ii 1S c o p e 1 2T e r m s a n d d e f i n i t i o n s 1 3 Formulae and constants 14 Table 1 Airwater system, to three significant figures 21 Bibliography 23BS 1339-1:2002 ii BSI 24 October 2002 Foreword This British Sta

6、ndard has been prepared by Technical Committee CPI/29, Humidity and temperature conditioning requirements. It supersedes BS 1339:1965 (which was concerned solely with the humidity of the air), and extends the consideration of humidity to that of any gas. BS 1339:1965 is now withdrawn. It is based pa

7、rtly upon A Guide to the Measurement of Humidity 1 published by the Institute of Measurement and Control under Crown Copyright. This is part 1 of a series of parts of BS 1339 on humidity as follows: Part 1: Terms, definitions and formulae; Part 2: Humidity calculation and tables; Part 3: Guide to th

8、e measurement of humidity. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprise

9、s a front cover, an inside front cover, pages i and ii, pages 1 to 23 and a back cover. The BSI Copyright notice displayed in this document indicates when the document was last issued.BS 1339-1:2002 BSI 24 October 2002 1 1 Scope This part of BS 1339 gives terms, definitions, symbols, units, formulae

10、 and constants associated with humidity and its measurement. 2 Terms and definitions NOTE Some alternative and obsolescent terms and definitions used in considering humidity and its measurement are discussed in part 3 of this British Standard. 2.1 Definitions of general terms 2.1.1 absorption retent

11、ion of a substance, e.g. water or water vapour, by penetration into the bulk of a material 2.1.2 adsorption retention of a substance, e.g. water or water vapour, as a layer on the surface of a material or within a material 2.1.3 absolute humidity deprecated term used loosely to describe either mixin

12、g ratio (2.1.29), specific humidity (2.1.41) or volumetric humidity (2.1.49) 2.1.4 adiabatic saturation temperature final temperature reached by a small quantity of vapour/gas mixture into which water is evaporating 2.1.5 condensate condensed substance, e.g. liquid water or ice NOTE Technically, if

13、vapour condenses directly to a solid without passing through a liquid phase, it is termed a sublimate. In this Standard, condensate is used as a general term for any liquid or solid produced by condensation of vapour. 2.1.6 condensation temperature temperature at which condensate forms as liquid or

14、solid on cooling a humid gas 2.1.7 desiccant substance which exerts a drying action by adsorption or absorption of, or chemical reaction with, water vapour 2.1.8 desorption release of a substance which has been retained by absorption or adsorption 2.1.9 dew point temperature at which the vapour pres

15、sure of the vapour in a humid gas is equal to the saturation vapour pressure over pure liquid and at which condensate forms as liquid on cooling the gas NOTE Below freezing point dew point is usually used to mean frost point. When referring to the supercooled liquid dew point (2.1.42) it is normal t

16、o state this explicitly.BS 1339-1:2002 2 BSI 24 October 2002 2.1.10 dry-bulb temperature measured air temperature, usually paired with a wet-bulb temperature to derive a value for relative humidity 2.1.11 dry gas non-condensable gas or gas mixture containing no vapour, e.g. dry air at zero humidity

17、2.1.12 enhancement factor water vapour enhancement factor factor by which a value of pure saturation vapour pressure is multiplied to obtain the actual saturation vapour pressure which takes into account the effect of the presence and overall pressure of air or other gases. NOTE The enhancement fact

18、or also applies to unsaturated humid gas, where it modifies the pure vapour pressure to the actual vapour pressure. 2.1.13 enthalpy (of humid gas) measure of the total energy in a humid gas, being the nominal sum of the enthalpies of the dry gas (sensible heat) and of the vapour (sensible heat and l

19、atent heat) 2.1.14 equilibrium relative humidity (of a substance) value of the relative humidity of a humid gas at which there is no net exchange of moisture with a given substance NOTE Equilibrium relative humidity is a property of the substance and is used for indirectly indicating or controlling

20、the condition of moisture-sensitive substances such as paper. It is normally measured in an enclosed space. 2.1.15 frost point temperature at which the vapour pressure of the vapour in a humid gas is equal to the saturation vapour pressure over ice (frozen solid) and at which condensate forms as fro

21、st on cooling the gas 2.1.16 gas fluid in which molecules move freely and can expand indefinitely to occupy the total volume in which it is contained NOTE The term gas is used especially for substances which do not become liquid or solid at normal ambient conditions, e.g. air. If this is not the cas

22、e, the term vapour is generally used. 2.1.17 gas density mass of humid gas present in a unit volume of humid gas 2.1.18 humidity presence of vapour, e.g. water vapour, in air or other gas NOTE Humidity is often used to mean only relative humidity although, strictly speaking, humidity refers to all k

23、inds of absolute indications of humidity; for very low humidities, other more specific terms tend to be used.BS 1339-1:2002 BSI 24 October 2002 3 2.1.19 humidity ratio deprecated term for mixing ratio (2.1.29) 2.1.20 humid gas mixture containing one or more non-condensable gases and one or more vapo

24、urs, e.g. a mixture of air and water vapour 2.1.21 humid heat heat required to raise the temperature of a unit mass of dry gas and accompanying vapour by 1 K at constant pressure; the specific heat capacity of a gas/vapour mixture 2.1.22 humid volume volume occupied by humid gas containing unit mass

25、 of dry gas 2.1.23 hygrometry humidity measurement 2.1.24 hygroscopic tending to absorb water vapour 2.1.25 ice-bulb temperature steady state temperature reached by a small quantity of ice evaporating into a large quantity of unsaturated water vapour/gas mixture 2.1.26 ideal gas gas to which the law

26、s of Boyle, Gay-Lussac and Avogadro are applicable 2.1.27 latent heat heat energy associated with a change of phase at constant temperature 2.1.28 mass fraction ratio of the mass of a component in a mixture to the total mass of substance present NOTE For vapour in gases this is the specific humidity

27、 and for low humidities becomes approximately equal to the mixing ratio. 2.1.29 mixing ratio mass ratio humidity ratio (deprecated) mass of vapour per unit mass of dry gas with which it is associated; it is a dimensionless ratio although often expressed in units of mass per mass NOTE The so-called “

28、mixing ratio by volume” is a deprecated term for mole ratio or volume ratio.BS 1339-1:2002 4 BSI 24 October 2002 2.1.30 moisture water in any form NOTE Moisture is also used specifically for water that is absorbed or adsorbed or bound into any material. 2.1.31 mole fraction volume fraction ratio of

29、the number of moles of a component in a humid gas to the total number of moles of humid gas present 2.1.32 mole ratio molal ratio volume ratio mixing ratio by volume (deprecated) ratio of the number of moles of a component in a humid gas to the amount of dry gas present 2.1.33 partial pressure (of v

30、apour) that part of the overall pressure exerted by the vapour component in a humid gas 2.1.34 percentage saturation ratio of the actual mixing ratio to the saturation mixing ratio at the same temperature and pressure, expressed as a percentage (%) NOTE Under ordinary climatic conditions, percentage

31、 saturation is almost identical to relative humidity. 2.1.35 ppm v PPM V mole ratio, expressed as parts per million (10 -6 ) NOTE This may also be termed ppm v(dry basis). At low humidities it is almost identical to ppm v(wet basis), which is the mole fraction expressed as parts per million. Mole ra

32、tio may also be expressed in parts per billion (10 -9 ), ppb v . 2.1.36 ppm w PPM W mixing ratio, expressed as parts per million (10 -6 ) NOTE This may also be termed ppm w(dry basis). At low humidities it is almost identical to ppm w(wet basis), which is the specific humidity (mass fraction) expres

33、sed as parts per million. Mixing ratio may also be expressed in parts per billion (10 -9 ), ppb w . 2.1.37 relative humidity ratio of the actual vapour pressure to the saturation vapour pressure over a plane liquid water surface at the same temperature, expressed as a percentage NOTE 1 Relative humi

34、dity is commonly abbreviated to rh, although this is not a recognized abbreviation. NOTE 2 Values of relative humidity are usually expressed in units of percentage relative humidity, % rh. “% rh” is not an agreed SI unit. However, the use of the symbol “%” alone to denote units of relative humidity

35、is generally not advisable, since there is a risk of confusion between value of relative humidity and fraction of value.BS 1339-1:2002 BSI 24 October 2002 5 2.1.38 saturation mixing ratio mixing ratio of humid gas in equilibrium with a plane surface of water or ice at the same temperature containing

36、 the equilibrium quantity of dissolved gas NOTE This is the highest mixing ratio which non-supersaturated humid gas can attain at the given temperature, and corresponds to a relative humidity of 100 %. 2.1.39 saturation vapour pressure maximum pressure of vapour that can exist at a given temperature

37、 NOTE Pure saturation vapour pressure is the pressure exerted by vapour with no other gases present, i.e. in a partial vacuum. Actual saturation vapour pressure of a vapour in a humid gas is slightly different; the difference is quantified by the enhancement factor. 2.1.40 sensible heat component of

38、 the enthalpy of a substance that varies according to temperature 2.1.41 specific humidity mass of vapour per unit mass of humid gas 2.1.42 supercooled liquid dew point supercooled water dew point dew point with respect to liquid (e.g. water) below the normal freezing point 2.1.43 thermodynamic wet-

39、bulb temperature deprecated term for adiabatic saturation temperature (2.1.4) NOTE For the airwater system at atmospheric pressure between 0 C and 100 C, with water vapour contents of less than 0.1 kg kg 1 , the thermodynamic wet-bulb temperature is within 1 C of the wet-bulb temperature. For vapour

40、s other than water vapour, the thermodynamic wet-bulb temperature may be markedly different to the wet-bulb temperature. 2.1.44 vapour substance in the gaseous state which may be liquefied by increasing the pressure without altering the temperature NOTE This is a gas below its critical temperature.

41、2.1.45 vapour density deprecated term used either for gas density (2.1.17) or volumetric humidity (2.1.49) 2.1.46 vapour pressure (of water) partial pressure that part of the total pressure contributed by the vapour NOTE Pure vapour pressure is the pressure exerted by vapour with no other gases pres

42、ent, i.e. in a partial vacuum. Actual vapour pressure of a vapour in a humid gas is slightly greater; the difference is quantified by the enhancement factor.BS 1339-1:2002 6 BSI 24 October 2002 2.1.47 vapour pressure deficit vapour pressure difference difference between actual vapour pressure and sa

43、turation vapour pressure at air temperature (usually given symbol of D or p) 2.1.48 volume fraction ratio of the volume nominally occupied by a component of a mixture to the total volume NOTE This is numerically identical to mole fraction for an ideal gas. 2.1.49 volumetric humidity mass of vapour p

44、resent in a unit volume of humid gas 2.1.50 water activity (of a substance) equilibrium relative humidity, expressed on a scale of 0 to 1 (dimensionless units) instead of 0 % to 100 % 2.1.51 water vapour water in gaseous form below its critical temperature 2.1.52 wet-bulb temperature temperature ind

45、icated by a thermometer sheathed in wet wicking, and influenced by the rate of evaporation from the wicking. The steady state temperature reached by a small quantity of liquid evaporating into a large quantity of unsaturated vapour/gas mixture is the wet-bulb temperature of a perfect psychrometer NO

46、TE 1 This is usually paired with a dry-bulb temperature to derive a value for relative humidity. NOTE 2 See also thermodynamic wet-bulb temperature (2.1.43) and psychrometer (2.2.22). NOTE 3 For the airwater system at atmospheric pressure between 0 C and 100 C, with water vapour contents of less tha

47、n 0.1 kg kg 1 , the wet-bulb temperature is within 1 C of the adiabatic saturation temperature. 2.2 Measurement terms 2.2.1 acoustic humidity sensor acoustic sensor sensor utilizing the transmission of sound in a humid gas to indicate its humidity 2.2.2 adiabatic expansion hygrometer hygrometer in w

48、hich the cooling on expansion of humid gas produces a cloud if the dew point is reached 2.2.3 aspirated psychrometer psychrometer with provision for a forced flow of humid gas over the sensorsBS 1339-1:2002 BSI 24 October 2002 7 2.2.4 capacitive hygrometer capacitance hygrometer electrical impedance

49、 hygrometer or dew-point sensor 2.2.5 colour change hygrometer hygrometer indicating changes in humidity by the change in colour of a material occurring as a result of its reaction to moisture 2.2.6 condensation hygrometer hygrometer in which the dew-point temperature is measured by cooling a sample of humid gas until condensate in the form of dew or frost appears, and observing the temperature at which this happens 2.2.7 dew-point sensor sensor in whi