ISO 10051-1996 Thermal insulation - Moisture effects on heat transfer - Determination of thermal transmissivity of a moist material《绝热 湿度对传热影响 含湿材料传热率的测定》.pdf

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1、INTERNATIONAL STANDARD IS0 10051 First edition 1996-04-01 Thermal insulation - Moisture effects on heat transfer - Determination of thermal transmissivity of a moist material Isolation thermique - Effets de /humidit sur /es propri& relatives au transfert de chaleur - D&termination de la transmissivi

2、t6 thermique dun mat&au humide Reference number IS0 10051 :I 996(E) IS0 10051:1996(E) Contents Page 1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . _._._ 1 2 Normative references . _, ,._ 1 3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4 Symbols and units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 5 General considerations . . . . . _._. . . . . . . . . . .

4、. 2 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _. 2 5.2 Description of heat and mass transfers . . . . . . . . . . . . . . . . . . a 3 5.3 Determination of thermal transmissivity of a moist material 3 6 Test ap

5、paratus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7 Test procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 5 7.1 General _._._ 5 7.2 S

6、pecimen preparation and conditioning . . . . . . . . . . . . . . . . . . . . . . . *. 5 7.3 Selection of phase A or C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.4 Derivation of thermal transmissivity from measured values of heat fl

7、ow and temperatures . . . . . . . . . . _ 6 7.5 Flow chart of possible test procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.6 Sources of error . . _. _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _._. 9 7.7 Calculations . . . . . . . .

8、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . _._ 9 8 Test report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -._ 9 Annexes A Theoretical background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9、. . . . . . . . . . . . . . . 11 B Evaluation of moisture flow and cases for which g,-h, is small 15 C Approximate solutions of J*(w) with negligible movement of liquid .,., 17 D Derivation of 1 from measured values of heat flow and temperatures in phase C with movement of liquid in the test specime

10、n 18 0 IS0 1996 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Sta

11、ndardization Case Postale 56 l CH-1211 Geneve 20 l Switzerland Printed in Switzerland ii J IS0 IS0 10051:1996(E) E Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 IS0 10051:1996(E)

12、 6 IS0 Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for wh

13、ich a technical committee has been established has the right to be represented on that committee. International organizations, governmental and nongovernmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all m

14、atters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 10

15、051 was prepared by Technical Committee ISOflC 163, Thermal insulation, Subcommittee SC 1, Test and measure- ment methods. Annexes A, 6, C, D and E of this International Standard are for information only. iv 0 IS0 IS0 10051:1996(E) Introduction The thermal transmissivity of a moist material is neede

16、d for the assess- ment of design values of thermal conductivity and thermal resistance under service conditions as described in IS0 104561. The thermal transmissivity of a moist material is also necessan/ for any calculation of combined heat and moisture transfer. Heat transfer within moist porous m

17、aterials involves a complex combination of - radiation, - conduction in the solid, liquid and gas phases, - convection (in some operating conditions), - mass transfer (in the moist materials), and their interactions. While these heat and mass flow phenomena are transitory in nature, some of them hav

18、e a long term contribution that must be recognised in the evaluation of thermal insulation performance. This International Standard determines the long-term contribution of both ma- terial structure and moisture on thermal transmissivity. This transmissivity, called thermal transmissivity of a moist

19、 material, is a material property and a function of the moisture content of the material. Normally, thermal transmissivity of a moist material varies locally in the material and is a function of the moisture content of each layer. The correct operation of the apparatus used to obtain the thermal tra

20、nsmissivity of a moist material and the interpretation of experimental results are difficult tasks that require great care. It is recommended that the operator and the user of measured data both have a thorough back- ground knowledge of heat and moisture transfer mechanisms in the ma- terials, produ

21、cts and systems being evaluated, coupled with experience of measurements made using guarded hot plate or heat flow meter ap- paratus. I) To be published. V INTERNATIONAL STANDARD 0 IS0 IS0 10051:1996(E) Thermal insulation - Moisture effects on heat transfer - Determination of thermal transmissivity

22、of a moist material 1 Scope This International Standard specifies a method to de- termine the thermal transmissivity of a moist material (1) under steady-state moisture conditions, i.e. not affected by moisture movement. It is measured using standardized guarded hot plate and heat flow meter methods

23、, at temperatures above 0 “C. This material property is a function of the moisture content and does not represent the thermal performance of a material under service conditions. However, it can be used, together with knowledge of the moisture con- ditions in the material, to predict the practical th

24、ermal performance. The use of ,I, the distribution of moisture under ser- vice conditions and consequently the prediction of thermal performance under service conditions are outside the scope of this International Standard. However, the moisture distribution under service conditions should, where po

25、ssible, be considered when 1 is determined. Furthermore, transient meth- ods of measurement are not included due to the dif- ficulty involved in analysing and interpreting the results of these methods. 2 Normative references The following standards contain provisions which, through reference in this

26、 text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most re- c

27、ent editions of the standards indicated below. 2) To be published. Members of IEC and IS0 maintain registers of cur- rently valid International Standards. IS0 7345:1987, Thermal insulation - Physical quan- tities and definitions. IS0 9346:1967, Thermal insulation - Mass transfer - Physical quantitie

28、s and definitions. IS0 8301 :I 991, Thermal insulation - Determination of steady-stare thermal resistance and related prop- erties - Hear flow meter apparatus. IS0 8302:1991, Thermal insulation - Determination of steady-state thermal resistance and related prop- erties - Guarded hot plate apparatus.

29、 IS0 6946-l :1986, Thermal insulation - Calculation methods - Part 1: Steady state thermal properties of building components and building elements. IS0 9288:1989, Thermal insulation - Hear transfer by radiation - Physical quantities and definitions. IS0 1O456:-2, Thermal insulation - Building ma- te

30、rials and products - Determination of declared and design thermal values. 3 Definitions for the purposes of this International Standard, the following definitions apply. 3.1 thermal transmissivity of a moist material, I. l : Intrinsic material property dependent upon moisture content and temperature

31、 but not on testing conditions. It is often referred to elsewhere as ther- mal conductivity of a moist material. It is defined for 1 IS0 10051:1996(E) 0 IS0 a moist material by the following differential equation during steady-state conditions: * =-1.dT m dx when moisture distribution within the mat

32、erial is in the steady-state and there is no liquid movement within the material. NOTE 1 The transmissivity, either for dry materials (see IS0 9288, IS0 8301 and IS0 8302) or for moist materials (see this document) expresses a material property that has the dimension of a thermal conductivity but th

33、at can replace it only in some expressions (in most cases those related to steady-state heat and mass transfer in a slab). Usually transmissivity cannot replace conductivity in most two- and three-dimensional flow patterns, in the expression of ther- mal diffusivity and non steady-state problems. Du

34、e to the complexity of heat and mass transfer problems, transmissivity can seldom be determined through one single experiment, rather a procedure or particular testing con- ditions are required, e.g. tests at high thicknesses for the determination of the thermal transmissivity and equilibrium of moi

35、sture distribution and absence of moisture flow for the determination of thermal transmissivity of a moist ma- terial (non steady-state methods are usually excluded from the determination of transmissivity). 3.2 hygroscopic range: Moisture content in equi- librium with 98 % relative humidity or lowe

36、r. 4 Symbols and units For the purposes of this International Standard the following symbols and units apply. Symbol Quantity Unit a d g gt gv 8 h he 4 4 4 4m Material-related constant in a linear relationship Thickness Density of moisture flow rate Density of total moisture flow rate Density of vap

37、our flow rate Density of liquid flow rate Specific enthalpy Specific latent enthalpy of evap- oration or condensation Specific enthalpy of vapour Specific enthalpy of liquid Density of heat flow rate Measured density of heat flow rate at the hot and cold sides of the specimen m J/kg J/kg J/kg J/kg W

38、/m2 W/m2 wcr Thermal resistance Time Thermodynamic temperature Humidity by volume Moisture content mass by vol- ume Moisture content, below which gl may be considered negligible Moisture content in vapour phase Moisture content in liquid phase Moisture permeability Bulk density of material Thermal c

39、onductivity of dry ma- terial Thermal transmissivity of a moist material Relative humidity m2-K/W S K kg/m3 kg/m3 kg/m3 kg/m3 kg/m3 m2/s kg/m3 WI 0-W W/b-K) NOTE 2 In this International Standard, humidity by voi- ume (v) has been used as the driving force for water vapour diffusion and moisture cont

40、ent mass by volume (w) as moisture content. The use of partial water vapour pressure (PJ and moisture content mass by mass (u) respectively are equivalent provided that relevant material properties and boundary conditions are used. Subscripts b Border between zones 1 and 2, figure 2 cold Cold surfac

41、e of specimen cr See wcr hot Hot surface of specimen I Arbitrary slice of specimen I Liquid m Measured sat Saturation sur Specimen surface t Tota I V Vapour see 5 General considerations 5.1 Introduction This clause describes the mechanisms by which moisture affects heat transfer in order to give the

42、 theoretical background for a test method which allows 2 0 IS0 IS0 10051:1996(EI prediction of thermal performance in the presence of - evaporation and condensation within a pore or a moisture. local area, and Although the equations derived hereafter are as gen- eral as possible, examples of the use

43、 of these equations are given presupposing that measurements will be performed - thermal radiation and natural convection in the pores. Each of these four heat flows is considered pro- portional to the gradient of temperature, so we can - in standardized apparatus intended for a steady- write by ana

44、logy with Fouriers law: state method (guarded hot plate or heat flow me- ter), and q = q1 + it is therefore essential to treat moisture transfer as the sum of a vapour flow and a liquid flow: gt = 1.dT & + &-h, + kJ4 . . . The first term in the right-hand part of equation (3) describes the heat flow

45、 caused by a temperature gradient. It consists essentially of - conduction in the solid material and in the air in the pores of the material, - conduction in water bound to the pore walls, In the case of thermal transmissivity of a moist ma- terial, increased conduction due to the presence of moistu

46、re in the material must be considered. The second and third terms of equation (3) describe the parts of the heat flow associated with the enthalpies of vapour and liquid and the effects of evaporation and condensation. These fluxes are not proportional to the temperature gradient. For the treatment

47、of heat transfer in moist materials it is necessary to separate the mechanisms “con- duction heat flux” and “heat flux by evaporation/diffusion/condensation”. In the past it has been customary to divide the total heat flux by the temperature gradient to obtain the thermal conductivity of a moist mat

48、erial. This pro- cedure is clearly faulty, because it gives a variable value, dependent on conditions of measurement. It is also important to distinguish carefully between moisture effects in service and those in laboratory test conditions. Simulation of all the complex moisture effects, which occur

49、 under service conditions and during a test, is not considered within the framework of this docu- ment. Effects of moisture flow and phase changes depend entirely on the occurrence and magnitude of moisture transfer in the material. If these effects are allowed during the test, it is difficult to assess a ma- terial or component property. There will also be a great risk that these types of effects are estimated inaccurately. The main purpose of the test is therefore to determine 2 which is a necessary basis for the predicti