1、Designation: C1041 10Standard 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 o
2、f 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
3、 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 stea
4、dy-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 co
5、nditions.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 wor
6、k between similar materials,aging, or other conditions of use.NOTE 1Further 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 ap
7、pro-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
8、Method for Steady-State Heat Transfer Proper-ties of 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 Forc
9、e(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 pr
10、opor-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 ot
11、her 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 ord
12、er 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 Subco
13、mmittee 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 sta
14、ndard.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.1Copyright ASTM International, 100 Barr Harbor Drive, P
15、O Box C700, West Conshohocken, PA 19428-2959, United States.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
16、 t2insulation outside surface temperature,C (F).3.2.7 Rareal resistance of the insulating section,m2 KWShft2FBtuD (1)3.2.8 l (k)apparent thermal conductivity, 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 in
17、sulation, 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-situ in field applicatio
18、ns under pseudosteady-state conditions.5. Significance and Use5.1 The major contribution of this practice is that it enablesa measurement of the real-time energy loss or gain through achosen surface of an existing process insulation with minimaldisturbance to the heat flux through the insulating bod
19、y.5.2 The primary use of this practice will be for the in-situestimation of thermal transport properties of industrial insula-tion such as used on pipes, tanks, ovens, and boilers, operatingunder normal process conditions.5.3 Errors attributable to heat flow measurements over asmall area or short te
20、rm testing can be misleading and thispractice is intended to minimize such errors.5.4 Insulation processes with large temperature differencesacross the insulation are best suited to HFT measurementsbecause modest changes in ambient conditions have butminimal effects on HFT output.5.5 While it would
21、be ideal for the HFT and attachmentsystem to have zero thermal resistance, this factor is insignifi-cant to the measured result if kept to 5 % or less of theresistance of the insulating section being tested.6. Apparatus6.1 Heat Flux Transducer, as described in 3.1.1.6.2 Voltmeter/RecorderA voltage-m
22、easuring recordinginstrument accurate to within 0.5 % of the lowest HFT outputanticipated during the test. An integrating voltmeter is evenmore appropriate for reading the output of the HFT.6.3 Temperature SensorA thermocouple or other deviceof a type suitable for the temperatures being measured.6.3
23、.1 For measuring the temperature of an insulated surface,such as a pipe under insulation, a 1.5-mm diameter or smaller,flexible ungrounded thermocouple probe 500 mm long isrecommended.6.3.2 For measuring the temperature of surfaces that can beeasily accessed, 24 gauge or smaller, bare bead thermocou
24、plesor equivalent shall be used.6.4 Attachment MaterialsPressure-sensitive adhesivetape, elastic bands, straps, mastic, grease, or other means maybe used to hold the HFT in place on the test surface.6.5 Thermal Contact MaterialsPatching cement, siliconegrease, heat sink grease, silicone sealant, roo
25、m temperaturevulcanizing elastomer, thermally conducting epoxy, or con-formable pads may be used to provide maximum contactbetween the test surface and the HFT where applicable. Thethermal coupler should not add to or reduce the resistance ofthe system such that the temperature patterns of heat flow
26、s aresignificantly changed. This could be measured by surfacetemperature probes or infrared measurement devices.6.6 Surfacing MaterialsCoating, films, or foils to adjustthe surface emittance of the HFT to match the radiant charac-teristics of the test surface.7. Calibrations7.1 HFT must be calibrate
27、d under the conditions of use; forexample, a calibration under aluminum jacketing on a testsetup in accordance with Test Method C335, would be properfor calibration of an HFT for subsequent testing under similarconditions.7.2 Calibrate HFT to national reference standards in accor-dance with Test Met
28、hods C177, C335,orC518. A calibrationcurve showing q/V versus insulation surface temperature (ex-pected to be the HFT temperature) shall be developed coveringthe intended range of operating temperatures and heat fluxes.7.2.1 The following is an example of calibration under useconditions (pipe insula
29、ted with preformed insulation and jack-eted with aluminum):NOTE 1Belt wraps around exterior; shim slips under jacketing (spotHFT).FIG. 1 Flexible Heat Flux Transducers for PipesC1041 1027.2.1.1 Set up the apparatus in accordance with Test MethodC335 with preformed insulation, jacketed with aluminumj
30、acket in the same condition as that to be tested.7.2.1.2 Establish steady-state at test temperature (3.1.2).7.2.1.3 Insert flexible HFT under jacket, near the center ofthe insulation section. The jacket should be lifted enough toprovide guidance in placing the HFT away from all joints in theinsulati
31、on section. (When a belt HFT is being calibrated, itmust be wrapped in a tight helix around the center of theinsulation section with the appropriate side, foil or gray tomatch emittance, exposed. Attach the strap to the belt, pullingand rubbing the belt into close contact with the insulationsection,
32、 making sure that the lap of the belt is on the side of thepipe.)7.2.1.4 Insert a bare temperature sensor about 50 mm awayfrom the HFT. After calibrating the belt HFT, place the sensorbetween the belt and the insulation surface to measure surfacetemperature.7.2.1.5 Read pseudo steady-state electrica
33、l output of HFTand temperature at both surfaces of the insulation. Since theoutput of the HFT will fluctuate under most conditions, agraphical or integrated average of the output of the HFT mustbe made.7.2.1.6 Utilizing q, as may be calculated from Test MethodC335 data, determine the calibration val
34、ue for the HFT in q/Vfor at least 3 insulation surface temperatures.7.2.1.7 Plot calibration value (q/V) versus insulation surfacetemperature (7.2.1.6).7.3 Calibrate the thermocouple in accordance with TestMethod E220.8. Test Section and HFT and Temperature SensorPlacement Guidelines8.1 Test Section
35、:8.1.1 Selection of the test sections must be appropriate andconsistent with the test objectives. Several test sections may beneeded.8.1.2 Infrared scanning is an appropriate way to identifyrelative surface uniformity conditions so that the HFT may beplaced to measure the thermal transport propertie
36、s of a repre-sentative area.8.1.3 Test sections must be amenable to attachment of theHFT with good thermal coupling and with minimal disturbanceof normal heat transfer.8.2 HFT Placement:8.2.1 Where block or pipe insulation is being tested, place aspot HFT preferably under the jacketing material near
37、 thecenter of a formed section of material. Avoid placement onjoints in insulation or laps in jacketing unless joint loss is beingevaluated.8.2.2 When a spot HFT is surface-mounted, it may beattached by using an adhesive two-sided tape, heat transfergrease, or other appropriate means. The emittance
38、of the HFTmust match the surface as closely as possible. With onetransducer an error of 0.01 at the 0.05 emittance level displacesthe reading by 3.5 %. An error of 0.1 at the 0.5 emittance leveldisplaces the reading by 3.5 %.8.2.3 Use a belt HFT for obtaining system thermal perfor-mance data of bloc
39、k or pipe insulation, including heat lossfrom large joints. When the belt HFT is mounted on reflectiveinsulation jacketing, it should have the foil side exposed; whenit is mounted on a surface with high emittance, the gray sidemust be exposed. Wrap the belt HFT around the insulation testsection in a
40、 tight helix with no overlap, with the belt pulled andrubbed to achieve close contact with the test surface. For fullcircumferential integration, a minimum of one complete wrapmust be made. If the HFT is not long enough to wrapcompletely around the test section, connect additional belts inseries unt
41、il a full wrap is made. Any helical lap of the belt pastfull circle should be on the side of the test section, not at the topor bottom. Do not overwrap a flexible HFT because compres-sion may cause a change in calibration.8.3 Thermocouple Placement:8.3.1 Measure the process surface temperature by in
42、sertinga thermocouple probe as described in 6.3.1 such that the probelies against the process surface for 150 mm (6 in.) or more. Forpurposes of inserting the probe, pierce the insulation with anice pick or other means at an angle of 30 or less to the planeof the surface to be measured. The correct
43、insertion of theprobe should show the maximum DT across the insulation.8.3.1.1 If the process system has built-in temperature-measuring capabilities in good repair and calibration the outputfrom such devices may be usable in place of a temperatureprobe.8.3.2 A bare bead thermocouple should be insert
44、ed underthe jacket to measure the surface temperature of the insulationnear the HFT (see 7.2.1.4).8.3.3 When the HFT is installed on a surface rather thanunder a jacket (or other cover), measure the surface tempera-ture of the insulation near the HFT by taping a bare beadthermocouple to the insulati
45、on surface (6.3.2) such that at least100 mm of the thermocouple is in contact with the surface. Theemittance of the tape should match that of the insulationsurface within 60.2 (see 8.2.2).9. HFT and Temperature Data Points9.1 The output from the HFT shall be recorded with asuitable recorder such tha
46、t pseudo steady-state (3.1.2) may beobserved when attained. Depending on exact environmentalconditions, the recorder usually traces a “band” of data whichmust be averaged graphically.9.2 As an alternative to recording the output of the HFT, anintegrating voltmeter may be used. While the exact condit
47、ionsto be utilized will depend upon the capabilities of the voltmeterat hand, it is suggested that short integration periods beaveraged over sequential 5-min intervals to determine whenpseudo steady-state (3.1.2) is achieved.9.3 Temperature readings shall be taken when the HFTreading comes to pseudo
48、 steady-state as defined in 3.1.2.9.4 Multiple location data points must be taken and aver-aged.10. Procedure10.1 Select an appropriate test area and install HFT andtemperature sensors in accordance with Section 8.10.2 Shield the HFT from direct solar radiation unless solargain is intended as a fact
49、or in the study.C1041 10310.3 Connect the HFT to the recorder or integrating volt-meter and take readings until pseudo steady-state is achieved inaccordance with Section 9.10.4 Measure the surface temperature of the insulation nearthe HFT in accordance with 8.3.2, 8.3.3, and 9.3.10.5 Measure the temperature of the process surface inaccordance with 8.3.1 and 9.3.10.6 If appropriate, measure ambient weather conditionsnear the HFT. Measurements of air movement, humidity,precipitation, insolation, etc. may be important in the interpre-tation
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