1、 BSI BS*EN*ISO 9288 96 9 1624669 0545337 55T BRITISH STANDARD Thermal insulation - Heat transfer by radiation - Physical quantities and definitions * * m The European Standard EN IS0 9288 : 1996 has the status of a British standard BS EN IS0 3288: 1996 ICS ai.aa.91; ai.w.zo; 91.10.10 NO COPYING WITH
2、OUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI BS*EN*ISO 9288 96 = 1624669 0545338 496 Amd. No. Date BS EN IS0 9288 : 1996 Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technica Committee RHEIS, Thermai insdating
3、 materials, upon which the following bodies were represent 01.060.20; 91.120.10 Descriptors: Thermai insulation, radiation, heat transfer, quantities, units of measurement, symbols, definitions English version Thermal insuMion - Heat transfer by radiation - Physical qyantities and definitions (Is0 9
4、288 : 1989) Isoiation thermique - Transfert de chaleur par rayonnement - Grandeurs physiques et dinitions Definitionen (S 9288 : 1989) Wrmeschutz - Wmebertmgung durch Strahung - Physikhe GrBen und (IS0 9288 : 1989) This European Standard was approved by CEN on 199501-05. CEN members are bound to com
5、ply with the CENXENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibhographid references concerning such national standards may be obtained on application to the Central Secret
6、ariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the offici
7、al versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, My, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Norma
8、isation Europisches Komitee fr Normung Centrai Secretariat: rue de Stassart 36, B-1060 Brussels O 1996 Copyright reserved to CEN members Ref. No. EN IS0 9288 : 1996 E _ - BSI BS*EN*ISO 9288 36 Lb24bb 0545342 913 Page 2 EN IS0 9288 : 1996 Foreword The text of the International Standard from lkhnicai
9、Committee ISORy= 163, Thermai insuMion, of the Intmmtionai Organhition for Stanmon (IN) has been taken over as a European standard by Technical Commitke CENm 89, Thermal performance of buildings and building components, the Secretariat of which is held by SIS. This European Standard shall be given t
10、he status of a national standard, either by publication of an identid text or by endorsement, at the latest by November 1996, and conflicting national standards shall be withdrawn at the latest by November 1996. According to the CENKENELEC Internal Regulations, the national standards organizations o
11、f the following countries are bound to implement this European standard: Ausixia, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlanck, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Introduction This Internationai Standard forms part
12、 of a series of vocabularies related to thed insukition. The series will include quantities and definitions. IS0 922911 Thermal insulation - ThemLal insulating materials and pmducts - Vocabulan/ conditions and properties of materials - Vocabulary IS0 9346 : 1987 Thermal insulation - Mass tmnsfw -Phy
13、sical quantities and definitions. IS0 7345 : 1987 17LemLal insulation - Physical IS0 9251 : 1987 ThemLal iW spectral or monochromatic, if they are related to a spec- tral interval centred on the wavelength A; hemispherical, if they are related to all directions along which a surface element can emit
14、 or receive radiation; directional, if they are related to the directions of propaga- tion defined by a did angle around the defined direction. 3.4 Classification of materials In relation with radiative transfer opaque medium : Medium which does not transmit any frac- tion of the incident radiation.
15、 The absorption, emission, reflection of radiation can be han- dled as surface phenomena. semi-transparent medium: Medium in which the incident radiation is progressively attenuated inside the material by ab- sorption or scattering, or both. The absorption, scattering and emission of radiation are b
16、ulk volumel phenomena. The radiative properties of an opaque or semi-transparent medium are generally a function of the spectral and directional distribution of incmnt radiation and of the temperature of the medium. NOTE - Thermal insulating meterials are generally semi-transparent media. 4 Terms re
17、lated to surfaces either receiving, transferring or emitting a thermal radiation 4.1 system in form of electromagnstic waves. radiant heat flow rate; radiant flux: Heat flow rate emitted, transferred or received by a NOTE - This is a total hemispherical quantity. 4.2 total intensity: Radiant heat fl
18、ow rate divided by the solid angle around the direction d : 4 4.3 total radbnce: Radiant heat flow rate divided by the did angle around the direction A and the projected area normal to this direction : 4.4 spectral radiant heat flow rate: Radiant heat flow rate divided by the spectral interval centr
19、ed on the wavelength A : a# A = - aA 4.S spectral Intensity: Total intensity divided by the spectral interval centred on the wavelengthn: Symbol for quantity Q 19 Li2 A IQA Symbol for SI unit (including multiple or submultiple) W W/Sr W/ i m2.srJ W/m W/vm Wlicr-m) W/isr-pm) - ES1 BS*EN*ISO 9288 7b m
20、 3624667 0545345 b2b m Page 5 EN IS0 9288 : 1996 4.6 spectral radiance: Total radiance divided by the spectral intewal centred on the wavelength A : NOTES 1 Each spectral term AA is related to the corresponding total tem A by a relation of the Wpe m O Each directional term AQ is related to the corre
21、sponding hemispherical tem A by a relation of the type and m 2 Total radiance and spectral radiance are oriented quantities (vectors) defined in each point of space where radiation exists (see figure 3). moreover their values are independent of the particular surface used to define them. Sources whi
22、ch radiate with constant .fi (see 4.3) are called isotropic or diffu8e. Intensities are again oriented quantities but belong to a surface Isee figure 2). Radiant flows (total or spectral) are not oriented quantities and belong to a surface. 4.7 spectral radiant density of heat flow rate vector: 4.8
23、total radiant density of heat flow rate vector: m i, = J 1 L dQdA o Q=4n 4.9 spectral radiant density of heat flow rate (in the direction i): Symbol for quantity Symbol for Si unit linduding multiple or sub-multiple) W/ fm2.pm) WIm3 Wlm2 4.10 forward component of the spectral radiant density of heat
24、 flow rate: 4.11 ackward component of the spectral radiant density of heat flow rate: NOTES 1 We can express qr,ln by the following expression : qr.h = qr,An - qLAn 2 In combined unidirectional conduction and radiation heat transfer along a direction n , we have qn = Qai,n + Qr,n + + -+ - * where qn
25、 is the density of heat Row rate as defined in IS0 7345 : 1987.2.3; qd,n is the density of heat flow ram by conduction; qr,# is the total dint density of heat flow rate vector; qn can be determined experimentally w.Wi the guarded hot plate or heat flow meter method. -4 -P -. + 5 Terms related to sur
26、faces emitting a thermal radiation 5.1 emission : Process in which heat (from molecular agitation in gases or atomic agitation in di T is the absolute temperature of the black body. 5.6 black body spectral excitance: It is expressed by Plancks law which relates My to the wavelength I and to the abso
27、lute temperature of the black body: CIA -5 MT = exp(C2/A.T) - 1 where Cl = 2Xhct = 3,741 x 1016 W/d; C2 = heo/, at the same temperature: Ln EQ = - La. 5.9 spectral directional emissivity: Spectral radiance, LQA, of the considered surface divi- ded by the spectral radiance emitted by the black body,
28、L, at the same temperature: rpectral hemispherical emissivity: Spectral excitance, MA, of the considered surface MA M Symbol for quantity En %A E and a pari rQ1 may be transmitted. - The three terms aRA, end, follow the relationship am + PRA + TQA = 1 Similar relations can be written for spectral, d
29、iractional and total hemispherical terms. Spectral and total terms imply isotropic and incident radiation. a = 1 for the black body T = O for opaque bodies a = al; p = pl; r = TA for grey bodies a = QA; Q = RA; T = TA for isotropic or diffuse grey bodies. For a radiation of given direction and wavel
30、ength, we have in all cases a,(Ti = , while spectral radiances with negative components can be integrated in a single term, 4,;. 7.14 radiative thermal conductivity or radiatlvity: Quantity defined by the foilowing relation : qr = -A,gradT For a plane layer the relationship may be rewritten in the f
31、ollowing way: T an qr = -Ar- where n is the normal to the layer. NOTE - These relations are the consequence of Rosseland approximation (7.121 and their adventage is that they provide simple relations to express the total radiative density of heat flow rate, similar to Fouriers law for pure conductiv
32、e heat transfer. In case of insulating materiais there can be situations where the thickness is high enough to allow for the characterization of the layer through the sum of two independent terms, one corresponding to conduction through the solid matrix and enclosed gas, and another to radiation. Th
33、e last term is then called “radiatMty“, 1,. as opposed to “conductivity“. While considering only radiation heat transfer within an insulating material, radiativity is formally defined as radiative thermal conductivity, but to adhere to test procedures, is best understood, thinking of material layers
34、 of increasing thickness, as an increment in layer thickness divii ded by the corresponding increment in layer resistance when the conditions outlined in 7.15 to 7.18 apply (see also figure 41. In this case, 7.14 is identical to 7.16. 7.16 transfer factor: Characterizes an insulating product in rela
35、tion with the combined con- duction and radiation heat transfer: it depends on experimental conditions and is expressed by NOTE - it may be derived from the measurement of q, d and ATin a guarded hot plate; it is a material pro- perty only when d* d, (see figure 4). 7.16 radiativity: Characterizes a
36、n insulating material in relation with the radiation heat transfer only; it is expressed by Symbol for quantity Symbol for SI unit (including multiple or sub-muhiplei W/im-K) W/m.KI W/ im- Ki ES1 BS*EN*ISO 9288 96 Lb24bb9 0545354 639 Page 14 EN IS0 9288 : 1996 where R, can be seen as a thermal resis
37、tance due to heat transfer by radiation alone and where d, is as shown in figure 4. NOTE - It may be derived from the measurement of q, d and ATunder vacuum when the conduction heat transfer in the solid matrix is negligible. 7.17 combined gaseous and solid conductivity: Characterizes an insulating
38、material in relation with the pure conduction heat transfer: similarly to A, it is expressed by where Rd can be seen as a thermal resistance due to heat transfer by pure conduction and d, is as shown in figure 4. NOTE - Generalb, Ad is computed from a theoretical model. 7.18 thermal transmissivity:
39、Characterizes an insulating material in relation with the com- bined conduction and radiation heat transfer; it is independent of the experimental conditions and it is expressed by At = ( where R is the thml resistance due to combined conduction and radiation heat transfer (see IS0 7346 : 1987.2.71;
40、 d, is as shown in figure 4. NOTE - According to the preceding definitions, the thmal transmissivity can also be written as A, A the thermal transmissivity, d, that is an intrinsic material property independent of the experimental conditions, can now be measured. In this case we can also define 1, a
41、nd Adas materia1 properties and put 1, = A,.d + 1,. Never- theless , .Y.= d/R is not yet independent of the thickness Fax: 0181 996 7400. BSI offers members an individual updating service called PLUS which ensures that subscribers automaticaliy receive the latest eitions of standards. Buying standar
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