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ISO 31-4 | Celsius | Heat
Quantities and units Part 4:
Grandeurs et unit& Partie 4: Chaleur
3:58 pm, 6/21/06
IS0 3141992(E)
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Quantities. where necessary. . The work of preparing International Standards is normally carried out through IS0 technical committees. Unless otherwise specified. governmental and non-governmental.the decision by the International Committee for Weights and Measures Komite International des Poids et Mesures. CIPM) in 1980 concerning the status of supplementary units has been incorporated. International organizations. has been replaced by the International Temperature Scale 1990. The major technical changes from the first edition are the following: . conversion factors. definitions of these quantities and units. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. units. without permission in writing from the publisher.a number of new items have been added. 0 IS0 1992 All rights reserved.the International Practical Temperature Scale 1968. also take part in the work. no part of this publication may be reproduced or utilized in any form or by any means. In fulfilment of this responsibility. lSO/TC 12 has prepared IS0 31. The scope of Technical Committee lSO/TC 12 is standardization of units and symbols for quantities and units (and mathematical symbols) used within the different fields of science and technology. giving. ITS-90. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. . IPTS-68. International Standard IS0 31-4 was prepared by Technical Committee ISO/TC 12. including photocopying and microfilm. electronic or mechanical. This second edition cancels and replaces the first edition (IS0 3141978). International Organization for Standardization Case Postale 56 l CH-1211 Geneve 20 l Switzerland Printed in Switzerland ii .IS0 31-4:1992(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). in liaison with ISO. symbols. Standard conversion factors for converting between the various units also come under the scope of the TC.
Part 2: Periodic and related phenomena .Part 9: Atomic and nuclear physics .Part 0: General principles .Part 13: Solid state physics Annexes A and B of this part of IS0 31 are for information only.Part 5: Electricity and magnetism . under the general title Quantities and units: .Part 1: Space and time .Part 12: Characteristic numbers .Part 7: Acoustics . .Part 10: Nuclear reactions and ionizing radiations .Part 4: Heat .Part 6: Light and related electromagnetic radiations .Part 11: Mathematical signs and symbols for use in the physical sciences and technology .Pat-t 8: Physical chemistry and molecular physics .Part 3: Mechanics .0 IS0 IS0 31-4:1992(E) IS0 31 consists of the following parts.
see IS0 31-O. they are not intended to be complete. All units between two full lines belong to the quantities between the corresponding full lines on the left-hand pages. g.2 Tables of quantities The most important quantities within the field of this document are given together with their symbols and.1 General Units for the corresponding quantities are given together with the international symbols and the definitions. The SI units have been adopted by the General Conference on Weights and Measures (Conference G&&ale des Poids et Mesures.3. 0. The vectorial character of some quantities is pointed out. Where the numbering of an item has been changed in the revision of a part of IS0 31. in most cases. g) only one of these is given. definitions.3 Tables of units 0. in a particular context. When two types of italic (sloping) letter exist (for example as with 9. The units are arranged in the following way: a) The names of the SI units are given in large print (larger than text size). A symbol within parentheses implies that it is a “reserve symbol”. especially when this is needed for the definitions. This does not mean that the other is not equally acceptable. the main symbol is in use with a different meaning. CGPM). a dash is used to indicate that the item in question did not appear in the preceding edition. iv . For further information. 9. where two or more names or two or more symbols are given for one quantity and no special distinction is made. they are on an equal footing. but no attempt is made to be complete or consistent. 4.1 Arrangement of the tables The tables of quantities and units in IS0 31 are arranged so that the quantities are presented on the left-hand pages and the units on the corresponding right-hand pages. the number in the preceding edition is shown in parentheses on the left-hand page under the new number for the quantity. 0. 8.IS0 31-4:1992(E) 0 IS0 Introduction 0. In most cases only one name and only one symbol for the quantity are given. These definitions are given merely for identification. to be used when. In general it is recommended that such variants should not be given different meanings.
53 Reynolds number Re = 1. the unit 1 is generally not written out explicitly. 2) names of units based on the foot. powers of 10 may be used. These annexes are informative and not integral parts of the standard. 0.6 IS0 IS0 31-4:1992(E) The SI units and their decimal multiples and sub-multiples are recommended. although the decimal multiples and sub-multiples are not explicitly mentioned.32 x 1 O3 Considering that plane angle is generally expressed as the ratio between two lengths. the radian and steradian are dimensionless derived units. in the International System of Units.4 Numerical statements All numbers in the “Definition” column are exact. They are arranged in three groups: I) special names of units in the CGS system. pound and second and some other related units. and solid angle as the ratio between an area and the square of a length. This implies that the quantities plane angle and solid angle are considered as dimensionless derived quantities. Instead of prefixes. d) The names of non-S1 units which should not be combined with SI units are given only in annexes in some parts of IS0 31.53 x 1 = 1. Prefixes shall not be used to form multiples or submultiples of this unit. the CIPM specified in 1980 that. . 0. These units are separated by a broken line from the SI units for the quantities concerned.2 Remark on units for quantities of dimension one The coherent unit for any quantity of dimension one is the number one (1). When the value of such a quantity is expressed. 3) names of other units. c) The names of non-S1 units which may be used temporarily together with SI units are given in small print (smaller than text size) in the “Conversion factors and remarks” column. The units radian and steradian may be used in expressions for derived units to facilitate distinction between quantities of different nature but having the same dimension.3. When numbers in the “Conversion factors and remarks” column are exact. EXAMPLES Refractive index n = I. b) The names of non-S1 units which may be used together with SI units because of their practical importance or because of their use in specialized fields are given in normal print (text size). the word “exactly” is added in parentheses after the number.
INTERNATIONAL STANDARD 0 ISO IS0 31-4:1992(E) Quantities and units Part 4: Heat 1 Scope This part of IS0 31 gives names and symbols for quantities and units of heat. 2 Normative references The following standards contain provisions which. IS0 31-91992. 1. 3 Names and symbols The names and symbols for quantities and units of heat are given on the following pages. Quantities and units . conversion factors are also given. Metrologia. All standards are subject to revision. No. Members of IEC and IS0 maintain registers of currently valid International Standards. and parties to agreements based on this part of IS0 31 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. .Part 0: General principles. constitute provisions of this part of IS0 31.Part 8: Physical chemistry and molecular physics. IS0 31-0:1992. At the time of publication. the editions indicated were valid. through reference in this text. Quantities and units . Where appropriate. 27 (I 990).
15 K 2 Remarks The thermodynamic temperature To is exactly 0.IS0 31-4:1992(E) 0 IS0 Quantities 4EAT item No. 9 Thermodynamic temperature is one of the base quantities on which the SI is based. Quantity Definition Symbol l-l thermodynamic temperature 62 Celsius temperature t.Ol K below the thermodynamic temperature of the triple point of water. T. . (0) t=T-To where To is defined as being equal to 273.
Name of unit International symbol for unit -1 . This scale supersedes the International Practical Temperature Scale of 1968.65 K. fQo 3 . The CGPM has recommended that such intervals or differences should be expressed in kelvins (K) or in degrees Celsius (“C).4). No. such as “degre”. 27 (19901. It is based on a number of fixed points and interpolation procedures with the help of certain measuring instruments and defines the temperature down to 0. “deg”. as in the case of T and r.a d e g r e e C e l s i u s “C K Definition Conversion factors and remarks The kelvin. (amended edition of 1975) and the 1976 Provisional 0. and degree Celsius. is the fraction l/273.'0 T. The units of T. respectively.16 of the thermodynamic temperature of the triple point of water The units of thermodynamic and Celsius temperature interval or difference are identical. For further information see Metrologia. and are the kelvin.5 K to 30 K Temperature Scale.. the unit of thermodynamic temperature.IS0 31-4:1992(E) CJ IS0 HEAT hits Item No. The quantities corresponding to thermodynamic temperature and Celsius temperature defined by this scale are indicated respectively by Tso and (replacing Tss and ?68 defined by IPTS-68). Other names and symbols.. The degree Celsius is a special name for the kelvin for use in stating values of Celsius temperature The International Temperature Scale of 1990 (ITS-901 For the purpose of practical measurements the International Temperature Scale of 1990 was adopted by the CIPM in 1989.a kelvin G2. K. It should be noted that the symbol “C for the degree Celsius should be preceded by a space (see IS0 31-0:1992. the International Celsius Temperature. “degree centigrade” or “degree”. are deprecated. where fQo '90 = TQO . 1. subclause 3. in accordance with Resolution 7 of the 18th CGPM. IPTS-68. 1987. “C. is called the International Kelvin Temperature and r.
Heat flow rate divided by area 4-9 thermal conductivity 1.3. Quantities Definition Symbol Quantity 1 dl el=ldT F-3. 1 dV The subscripts in the symbols may be omitted when there is no risk of confusion. density of heat flow rate 4. L-4 pressure coefficient I-5. T . where AS is the change in entropy.AS.-T. the change in enthalpy. should be expressed as the change in the appropriate thermodynamic functions. quantity of heat e 4-7 heat flow rate cp Rate at which heat crosses a given surface 44 areic heat flow rate. with the symbol L. formerly called “latent heat”.1 to 4-4 are not completely defined unless the type of change is specified.2 (-) surface coefficient of heat transfer h. or AH.3 relative pressure coefficient % I dp %=Px P dp 8== XT=-+(g) coefficient Remarks The quantities 4-3. M +=ydT F-3. (K) Areic heat flow rate divided by temperature gradient 4-10.1 isothermal compressibility XT 4-5. where Ts is the temperature of the surface and Tr is a reference temperature characteristic of the external surroundings In building technology. e.1 coefficient of heat transfer K (k) Areic heat flow rate divided by temperature difference 4-l 0. with the symbol u. a. Q.2 cubic expansion %. . (a) 4=h(T.1 l i n e a r e x p a n s i o n U.g. coefficient F-3.IS0 31-4:1992(E) Q iEAT (continued) Item No.2 (-) isentropic compressibility XS 4-6 heat.) 4 IS0 T Xs=-+($) S The heat transferred in an isothermal phase transformation. The name pressure coefficient and the symbol /I are also used for the quantity 4-3. this quantity is often called thermal transmittance.
a reciprocal Pascal.0 IS0 31-4:1992(E) IS0 HEAT (continued) Units Item No. Name of unit International symbol for unit 4-3.K) 4-l 0. K-’ kelvin to the power minus one 4-4.a Pascal per kelvin Pa/K 4-5.a watt per square metre kelvin W/(m* .a watt per square metre W/m* 4-9.a watt per metre kelvin W/Cm .a watt W 4-8. Pascal to the power minus one Pa-’ 4-6.a reciprocal kelvin.K) Definition Conversion factors and remarks .a joule J 4-7.
2 massic heat 14-75.3 massic heat (4-75.3) capacity at constant volume. 4-16.7) thermal diffusivity Q 1 a=ec. 4-13 t-1 thermal conductance G G= 1/R See remark on 4-l 1.4) capacity at saturation.2) capacity at constant pressure. specific heat capacity at saturation Gat . where A is the thermal conductivity.1 massic heat (4-75. specific heat capacity at constant pressure 6 CP 4-l 6. with the symbol R.7) capacity. In building technology this quantity is often called thermal resistance. specific heat capacity at constant volume cv 4-16. specific heat capacity C Heat capacity divided by mass For the corresponding molar quantities. the quantity dQ/dT is the heat capacity This quantity is not completely defined unless the type of change is specified. e the volumic mass and cP the massic heat capacity at constant pressure heat capacity c When the temperature of a system is increased by dT as a result of the addition of a small quantity of heat dQ.4 massic heat (4-75. see IS0 31-8. 4-11 Quantities Quantity Definition Remarks Temperature difference divided by areic heat flow rate. 4-15 (4.7) 4-l 6. 4-14 (4 73. Symbol t h e r m a l insulance.74.IS0 31-4:1992(E) 0 IS0 HEAT (continued) Item No. M coefficient of thermal insulation M= 1/K 4-12 thermal resistance R Temperature difference divided by heat flow rate See remark on 4-l 1.
K/W 4-12.K) Definition Conversion factors and remarks 7 .a square metre kelvin per watt m2 .a square metre per m2/s second 4-15. HEAT (continued) Name of unit International symbol for unit Gl1.a watt per kelvin W/K Q-14.a kelvin per watt KW 4-13.Q IS0 IS0 31-4:1992(E) Units Item No.a joule per kelvin J/K 4-16.a joule per kilogram kelvin J/(kg .
7) thermodynamic energy y x Remarks Definition Symbol Quantity energy Y = c&v V ap x=-P t-1 av s For an ideal gas. F A=U-TS I G G=U+pV-TS (4-19.1) entropy s When a small quantity of heat dQ is received by a system the thermodynamic temperature of which is T. ratio of the specific heat capacities 3-l 7. the entropy of the system is increased by dQ/T. For the corresponding molar quantities. AU=Q+W where Q is heat transferred to the system and W is work done on the system 4-20. provided that no irreversible change takes place in the system massic entropy.2) isentropic exponent 4-18 14-l 7. x is equal to Y. t-17. (4-19.1 14-16. Thermodynamic energy is also called internal energy. Helmholtz function 4-20.2) Helmholtz free 4-20.3 enthalpy H H=U+pV A.IS0 31-4:1992(E) 0 Quantities -EAT (continued) item No. see IS0 31-8.5 Gibbs free energy. 4-19 (4-78.1 (-1 E All kinds of energy u For a closed thermodynamic system 4-20.2 (4-79.3) e n e r g y .4) Gibbs function IS0 G=H-TS .7) specific entropy s Entropy divided by mass 4-20.2 14-76.7) ratio of the massic heat capacities.4 (4-79.
a Name of unit one International symbol for unit 1 Definition Conversion factors and remarks See the introduction.a joule J 9 .2.a joule per kelvin 9-19. Cl 7.a joule per kilogram J/(kg . J/K 1-l 8.3.Q ISO al-Q:1992(El IS0 HEAT (continued) Jnits Item No.K) kelvin G20. subclause 0.
1) Planck function Y Remarks J = .l . specific Helmholtz free energy.4 massic Helmholtz (4-20. see IS0 31-8.2) specific enthalpy h Enthalpy divided by mass 4-21. 4-21.-I massic energy.2 :4-20. IS0 Definition Symbol Quantity t-21 .5 (4-20. Thermodynamic energy divided by mass Massic thermodynamic energy is also called massic internal energy.A/T Y= -G/T .7) massic thermodynamic energy. f Helmholtz free energy divided by mass massic Gibbs free 4-21.3 massic enthalpy.3) free energy.IS0 3141992(E) 0 Quantities -I EAT (concluded) Item No. (4-20.4) e n e r g y . specific Gibbs free energy. specific thermodynamic energy U Energy divided by mass For the corresponding molar quantities. specific Helmholtz function a.7) Massieu function J 4-23 (4-Z. specific energy e a-21. specific Gibbs function g Gibbs free energy divided by mass 4-22 (4-27.
a joule per kilogram J/kg 4-22.a joule per kelvin J/K Definition Conversion factors and remarks .a joule per kelvin J/K 4-23. HEAT (concluded) Name of unit International symbol for unit 4-21 .Q IS0 31-4:1992(E) IS0 Units Item No.
a British thermal unit per second foot degree Rankine: Btu/(s .293 071 1 W 49 thermal conductivity 4-9.A. 4. luantity tern No. British thermal unit: Btu 1 Btu = 788.67 The unit degree Fahrenheit is identical with the unit degree Rankine.a 4-7 heat flow rate 4-7.a British thermal unit per hour: Btu/h 1 Btu/h = 0. The symbol “F for the degree Fahrenheit shall be preceded by a space. It is equal to the “International Table British thermal unit” adopted by the Fifth International Conference on Properties of Steam (London.a Name of unit with symbol degree Rankine: “R degree Fahrenheit: “F Conversion factors and remarks 1 OR=+ K The symbol “R for the degree Rankine shall be preceded by a space. pound and second and some other units The use of these units is deprecated.Ibf = 1 055. +=+++32=++-459. I-1 - Quantity Unit item No. Annex A (informative) Units based on the foot.64 W/(m .OR) = 6 230. July 1956). .K) F-6 12 This is the only British thermal unit used in this annex. fr 4-2.A.ft .IS0 31-4:1992(E) 0 IS0 . OR) 1 Btu/(s .a Fahrenheit temperature.A. quantity of heat 4-6.056 J heat.A. Besides this a number of “British thermal units” were formerly used.ft .A.169 ft . thermodynamic temperature 4-l .
1 massic heat capacity. specific heat capacity 4-l 6.K) 4-10.K) (exactly) 4-21 . specific entropy 4-l 9.OR) = 4 186.a British thermal unit per second square foot degree Rankine: Btu/ (s .K) 4-14.ft* .3 massic enthalpy.2 massic thermodynamic energy.092 903 04 m*/s (exactly) ft2/S 4-I 6.fI? . pound and second and some other units (continued) luantity tern No.A.a British thermal unit per pound degree Rankine: Btu/(lb .b British thermal unit per hour square foot degree Rankine: Btu/ (h . l-1 0 114 Quantity coefficient of heat transfer thermal diff usivity Unit item No. f?.OR) 1 Btu/(h . Name of unit with symbol 4-l 0.A.A. OR) = 5.OR) Conversion factors and remarks 1 Btu/(sft*-“R) =20441.A.I massic energy.IS0 31-4:1992(E) Units based on the foot.678 26 W/(m* .8 J/(kg .A.7 W/(m*.OR) 1 Btu/(lb .a British thermal unit per pound degree Rankine: Btu/(lb .8 J/(kg .A.OR) 1 Btu/(lb . specific enthalpy 1 Btujlb = 2 326 J/kg (exactly) 13 . specific energy 4-21 .OR) = 4 186.K) (exactly) Cl9 massic entropy. specific thermodynamic energy 4-21.a square foot per second: 1 ft*/s = 0.a British thermal unit per pound: Btu/lb 4-21.
A. specific Helmholtz free energy. specific Gibbs function Name of unit with symbol 3ritish thermal unit per pound: 3tu/lb Conversion factors and remarks 1 Btujlb = 2 326 J/kg (exactly) 1 .4 nassic Helmholtz free energy.0 IS0 IS0 31-4:1992(E) r Units based on the foot. specific Helmholtz function 1-21 . pound and second and some other units (concluded) Quantity item No. specific Gibbs free energy.5 massic Gibbs free energy.a 4-21. S-2 1. Unit Quantity tern No.
. 4-6. quantity of heat Unit item No.a Name of unit with symbol 15 “C calorie: call5 Conversion factors and remarks 1 Cal. For this I. is the amount of heat required to warm 1 g of air-free water from 14.B.0 IS0 Is0 31-4:1992(E) Annex B (informative) Other units given for information..5 “C at a constant pressure of 101.T.184 J (exactly) . 4-6. 4-6 Quantity heat.B... The conversion factor shown above was proposed by the Comite consultatif de thermometric et calorimetric and adopted by the CIPM (1950) as being the most accurate value which could at that time be deduced from experiment. calorie: call. Quantity item No.T. especially regarding the conversion factor The use of these units is deprecated.=4.B. = 1.5 “C to 15.c thermochemical calorie: caith 1 Cal.325 kPa.b I.186 8 J 1 Meal. July 1956) adopted the definition 1 calIT = 4.000 5 J.. The International Union of Pure and Applied Physics in 1934 published a similar definition for the “gramme-calorie”. 1 cal.163 kW ’ h (exactly) 4-6. = 4. calorie (International Table calorie) the Fifth International Conference on Properties of Steam (London.185 5 J This value is uncertain by 0.
16:536:006. definitions. units of measurement. thermodynamics. symbols.15/. heat.IS0 31J:1992(E) 0 IS0 i UDC 389. conversion factor. quantities.72 Dadptom system of units. international system of units. conversion of units. Price based on 15 pages 4 .
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