ASTM_C_1041_-_10.pdf

Designation:C104110Standard Practice forIn-Situ Measurements of Heat Flux in Industrial ThermalInsulation Using Heat Flux Transducers1This standard is issued under the fixed designation C1041;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the in-situ measurement of heat fluxthrough industrial thermal insulation using a heat flux trans-ducer(HFT).1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.3 This practice estimates the thermal transport propertiesof thermal insulation materials in-situ in field applicationsunder pseudo steady-state conditions.It is not intended that thispractice should be used as a substitute for more preciselaboratory procedures such as Test Methods C177,C335,orC518.1.4 This practice is limited by the relatively small area thatcan be covered by an HFT and by the transient effects ofenvironmental conditions.1.5 Temperature limitations shall be as specified by themanufacturer of the HFT.1.6 While accurate values of heat flux are highly dependentupon proper calibrations under the conditions of use,it isacceptable to use the calibrations provided by the manufacturerof the HFT for comparative work between similar materials,aging,or other conditions of use.NOTE1Further information may be found in the literature(1-6).21.7 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3C177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC335 Test Method for Steady-State Heat Transfer Propertiesof Pipe InsulationC518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusE220 Test Method for Calibration of Thermocouples ByComparison TechniquesE230 Specification and Temperature-Electromotive Force(EMF)Tables for Standardized Thermocouples3.Terminology3.1 Definitions:3.1.1 heat flux transducer(HFT)a rigid or flexible trans-ducer in a durable housing comprised of a thermopile orequivalent for sensing the temperature drop across a thinthermal resistance layer which gives a voltage output propor-tional to the heat flux through the transducer.3.1.1.1 belt HFTa heat flux transducer having a belt-likeconfiguration such that the unit can be wrapped helicallyaround a section of pipe insulation(see Fig.1).3.1.1.2 spot HFTa small heat flux transducer having around,square,rectangular or other configuration for thesensitive area(see Fig.1).3.1.2 pseudo steady state of HFTthe criterion for pseudosteady-state condition is that the average HFT reading over twoconsecutive 5-min periods does not differ by more than 2%.Since the time constant of an HFT is typically less than or ofthe order of 1 min,using a time interval of 5 min ensures thatthe transient effects in the HFT are averaged.3.2 Symbols:3.2.1 Qheat flow,W(Btu/h).3.2.2 qheat flux,W/m2(Btu/hft2).1This practice is under the jurisdiction of ASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.30 on ThermalMeasurement.Current edition approved June 1,2010.Published September 2010.Originallyapproved in 1985.Last previous edition approved in 2007 as C1041 85(2007).DOI:10.1520/C1041-10.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.3 Coverall conductance of the insulated section,W/m2K(Btu/hft2 F).3.2.4 t0process surface temperature,C(F).3.2.5 t1insulation inside surface temperature.For pur-poses of this standard,t0and t1shall be considered to beidentical.3.2.6 t2insulation outside surface temperature,C(F).3.2.7 Rareal resistance of the insulating section,m2KWShft2FBtuD(1)3.2.8(k)apparentthermalconductivity,W/mK(Btuinhft2F).3.2.9 Dthickness of test section,m(in.).3.2.10 r2outer radius of pipe insulation,m(in.).3.2.11 r1inner radius of pipe insulation,m(in.).3.2.12 r0outer radius of pipe,m(in.).3.2.13 VHFT output in millivolts or other chosen unit.4.Summary of Practice4.1 This practice is a guide to the proper use of heat fluxtransducers for estimating the thermal transport properties ofthermal insulation in-