1、BS ISO 16957:2016Measurement of apparentthermal conductivity of wetporous building materials by aperiodic methodBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 16957:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 16
2、957:2016.The UK participation in its preparation was entrusted to TechnicalCommittee B/540/8, Mirror committee for ISO/TC 163 - ThermalPerformance and Energy use in the built Environment.A list of organizations represented on this committee can beobtained on request to its secretary.This publication
3、 does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016. Published by BSI StandardsLimited 2016ISBN 978 0 580 84055 5ICS 27.220Compliance with a British Standard cannot confer immunity fromlegal
4、obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 July 2016.Amendments issued since publicationDate Text affectedBS ISO 16957:2016 ISO 2016Measurement of apparent thermal conductivity of wet porous building materials by a periodic
5、 methodDtermination de la conductivit thermique apparente des matriaux de construction poreux et mouills par une mthode priodiqueINTERNATIONAL STANDARDISO16957First edition2016-06-15Reference numberISO 16957:2016(E)BS ISO 16957:2016ISO 16957:2016(E)ii ISO 2016 All rights reservedCOPYRIGHT PROTECTED
6、DOCUMENT ISO 2016, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior writ
7、ten permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 16957:2016
8、ISO 16957:2016(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Symbols and units . 25 Determination of thermal conductivity of a wet porous material by non-steady-state method (periodic method) 36 Measurement by periodic method . 36.1 Test procedure . 36.2
9、Measuring apparatus . 46.2.1 Overall design . 46.2.2 Generator of the sinusoidal or stepwise electric wave . 46.2.3 Heater 56.2.4 Specimen. 56.3 Specimen preparation and preconditioning 56.3.1 Initial uniform moisture content and adiabatic and impermeable boundaries 56.3.2 Embedding and the position
10、 of the thermocouples 56.4 Derivation of thermal diffusivity from measured temperatures (see Annex B) . 56.4.1 Solution for heat flow without moisture . 56.4.2 Solution for heat flow with moisture . 66.5 Estimation of measuring uncertainty due to moisture (vapour) movement 76.6 Thermal conductivity
11、77 Test report . 7Annex A (informative) Theoretical background . 9Annex B (informative) Derivation of thermal conductivity from measured temperatures .11Annex C (informative) Example of measurement by periodic method 17Bibliography .20 ISO 2016 All rights reserved iiiContents PageBS ISO 16957:2016IS
12、O 16957:2016(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject
13、 for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC)
14、on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be note
15、d. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying a
16、ny or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of u
17、sers and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the followin
18、g URL: www.iso.org/iso/foreword.html.The committee responsible for this document is ISO/TC 163, Thermal performance and energy use in the built environment, Subcommittee SC 1, Test and measurement methods.iv ISO 2016 All rights reservedBS ISO 16957:2016ISO 16957:2016(E)IntroductionMost building mate
19、rials, with the exception of glass and metals, are porous and, thus, absorb moisture due to condensation, rain and water uptake from the ground. The absorbed moisture may damage the materials through, e.g. rotting or frost damage and, thus, may cause their performance to deteriorate. In particular,
20、an increase in the moisture content of insulation material causes a reduction of its thermal resistance, which must be avoided as much as possible to preserve its performance. However, infiltration of rain water into a brick wall or joints of tiles and uptake of ground water into the foundation (foo
21、ting) are very difficult to avoid. Therefore, it is important to understand the changes in the thermal properties (thermal conductivity and heat capacity) of porous materials due to changes in their moisture content.ISO 10051 specifies a steady-state method for measuring the thermal conductivity of
22、a moist building material. In the steady-state method, a nonuniform distribution of moisture content in the test piece is inevitable, since the imposed temperature gradient causes moisture transfer. The nonuniform moisture distribution makes it difficult to define which moisture content the measured
23、 thermal conductivity corresponds to. ISO 10051 categorizes the moisture distribution in the test piece into several types and estimates the thermal conductivity corresponding to each type.Since theoretical and experimental research has recently been performed concerning heat and moisture transfer i
24、n porous materials (see References 5, 7, 8, 9 and 10), along with measurements and the construction of a database of hygrothermal properties (see Reference 6), hygrothermal behaviour can now be predicted with reasonable accuracy.This International Standard describes a transient method for measuring
25、the thermal conductivity of a wet porous building material and a method of evaluating the measurement uncertainty, on the basis of both theoretical developments for heat and mass transfer and the constructed database of hygrothermal properties. The evaluation of the measurement uncertainty makes pos
26、sible a simple and, thus, practical method for measuring thermal conductivity.NOTE Thermal conductivity is one of the necessary hygrothermal properties. Since heat transfer and mass transfer in porous material interact with each other, an exact value of the thermal conductivity must be given in orde
27、r to examine the validity of the theoretical models. Thus, precisely speaking, the above-mentioned theoretical models have not been validated, and the construction of the model and the measurements of the hygrothermal properties must be carried out in parallel. Nonetheless, it seems reasonable to ex
28、pect that measurement of the thermal conductivity with an allowable accuracy is possible using a suitable measuring method. This is the basis for the present document. ISO 2016 All rights reserved vBS ISO 16957:2016BS ISO 16957:2016Measurement of apparent thermal conductivity of wet porous building
29、materials by a periodic method1 ScopeThis International Standard describes a method of measuring the thermal conductivity (diffusivity) of a wet porous building material and a method of evaluating the measurement uncertainty.While ISO 10051 is the current International Standard, based on a steady-st
30、ate method, this International Standard proposes a method that makes use of a non-steady-state method which uses a small temperature change with a short period as an input. Along with the measurement, an evaluation of the measurement uncertainty is described, which makes possible a simple and practi
31、cal measuring method.This International Standard intends to measure the apparent (effective) thermal conductivity, including latent heat transfer caused by vapour movement. The situation in which moisture and/or air movement occur due to convection or gravity is excluded. The application of this Int
32、ernational Standard to high moisture content is excluded so that the gravity effect can be neglected. This International Standard can be applied to a porous material heavier than about 100 kg/m3, in which radiative heat transfer can be neglected.This International Standard specifies the following:a)
33、 a non-steady-state method of measuring thermal conductivity;b) an approximation formula for the measurement uncertainty caused by moisture movement and nonuniform moisture distribution (and, thus, a determination of the measuring conditions that satisfy the upper limit of measurement uncertainty);c
34、) an estimate of the heat transfer caused by moisture (vapour) movement.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated referen
35、ces, the latest edition of the referenced document (including any amendments) applies.There are no normative references in this document.3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 9346, ISO 10051 and the following apply.ISO and IEC maintain termi
36、nological databases for use in standardization at the following addresses: IEC Electropedia: available at http:/www.electropedia.org/ ISO Online browsing platform: available at http:/www.iso.org/obp INTERNATIONAL STANDARD ISO 16957:2016(E) ISO 2016 All rights reserved 1BS ISO 16957:2016ISO 16957:201
37、6(E)3.1apparent thermal conductivity of a wet material*intrinsic material property dependent upon moisture content and temperature, but not on testing conditionsNote 1 to entry: Since this value includes the influence of heat transfer due to phase change (condensation and evaporation), it is called
38、apparent thermal conductivity.4 Symbols and unitsSymbol Quantity Unitsa thermal diffusivity of the material m2/sA, B, C, D defined in Formula (B.14) c porosity m3/m3c specific heat of the material J/(kgK)csspecific heat of the dry material J/(kgK)DTmoisture (vapour and liquid water) conductivity rel
39、ated to temperature gradientkg/(msK)DMoisture (vapour and liquid water) conductivity related to water content gradientm2/sDTlliquid water conductivity related to temperature gradient kg/(msK)Dlliquid water conductivity related to water content gradient m2/sDTvvapour conductivity related to temperatu
40、re gradient kg/(msK)Dvvapour conductivity related to water content gradient m2/sE, E1, E2defined in Formula (B.12) I0amplitude of the input surface temperature Kkvvapour diffusivity kg/ms(kg/kg)R latent heat of vaporization J/kgS specific surface area inside the material, i.e. ratio of pore surface
41、area to the material volumem2/m3t time sT temperature KT0initial temperature KT1, T2, 1, 2the first and second terms of the perturbation solution of the temperature and water content, respectivelyK, kg/m3x coordinate mX humidity ratio of moist air in the pores of the specimen kg/kgXiequilibrium humi
42、dity ratio with liquid or capillary water at the interface in the materialkg/kgU3, U7, Q1 Q6, R1 R6, V18coefficients appearing solutions 2and T21, 2defined in Formula (B.13) effective vapour transfer coefficient at the interface kg/(mskg)/kg specific weight of dry air kg/m3 density of the material k
43、g/m3sdensity of the dry material kg/m31, 1, 1, 1, 1, 1water content coefficients of Dl, Dv, DTl, DTv, c , 2, 2, 2, 2, 2temperature coefficients of Dl, Dv, DTl, DTv, thermal conductivity without moisture movement W/(mK)2 ISO 2016 All rights reservedBS ISO 16957:2016ISO 16957:2016(E)Symbol Quantity Un
44、its* thermal conductivity defined as * = + RDTvW/(mK) water content of material kg/m30initial water content of material kg/m30water content by weight % angular velocity of the input surface temperature rad/s5 Determination of thermal conductivity of a wet porous material by non-steady-state method (
45、periodic method)When measuring the thermal conductivity of a porous material in which moisture transfer may occur, the nonuniformity of the water content distribution must be kept as low as possible under the temperature gradient. In order to minimize the nonuniformity, a periodic method is adopted
46、as a transient method of measuring thermal conductivity (see example in Annex C). Since positive and negative temperature gradients are generated in turn in this method, the (time-averaged) water content distribution can be expected to remain uniform.By measuring the temperatures at two points in th
47、e sample (usually one of them is at the sample surface), the thermal diffusivity (not conductivity) can be determined based on the amplitude ratio or phase difference of these two temperatures. If moisture movement does occur, a similar method can be used to determine the thermal diffusivity if the
48、input cyclic temperature fluctuation is kept small enough that the change in transport properties is also small enough that the system can be regarded as linear (see Annex B).6 Measurement by periodic method6.1 Test procedureA schematic diagram of the apparatus for the periodic method is given in Fi
49、gure 1. The whole system is installed in a climate chamber whose temperature is kept at the mean temperature of the sample under measurement. The sample is preconditioned at a certain water content, and then the whole surface is made impermeable to moisture movement. A periodic temperature variation is imposed on the sample, and the temperatures at (at least) two points in the sample are measured by thermocouples.Figure 1 Schematic diagram for measuring thermal d
