1、Designation: C 1041 85 (Reapproved 2007)Standard Practice forIn-Situ Measurements of Heat Flux in Industrial ThermalInsulation Using Heat Flux Transducers1This standard is issued under the fixed designation C 1041; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the in-situ measurement of heat fluxthrough industri
3、al thermal insulation using a heat flux trans-ducer (HFT).1.2 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 precis
4、elaboratory procedures such as Test Methods C 177, C 335, orC 518.1.3 This practice is limited by the relatively small area thatcan be covered by an HFT and by the transient effects ofenvironmental conditions.1.4 Temperature limitations shall be as specified by themanufacturer of the HFT.1.5 While a
5、ccurate values of heat flux are highly depend-entupon proper calibrations under the conditions of use, manufac-turers calibrations may be used with confidence for compara-tive work between similar materials, aging, or other conditionsof use.NOTE 1Further information may be found in the literature (1
6、-6).21.6 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. Referen
7、ced Documents2.1 ASTM Standards:3C 177 Test Method for Steady-State Heat Flux Measure-ments and Thermal Transmission Properties by Means ofthe Guarded-Hot-Plate ApparatusC 335 Test Method for Steady-State Heat Transfer Proper-ties of Pipe InsulationC 518 Test Method for Steady-State Thermal Transmis
8、sionProperties by Means of the Heat Flow Meter ApparatusE 220 Test Method for Calibration of Thermocouples ByComparison TechniquesE 230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized Thermocouples3. Terminology3.1 Definitions:3.1.1 heat flux transducer (HFT)a rigid or
9、 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-likeconfigu
10、ration 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-
11、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:Sy
12、mbols:3.2.1 Qheat flow, W (Btu/h).3.2.2 qheat flux, W/m2(Btu/hft2).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 beidentica
13、l.3.2.6 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).1This practice is under the jurisdiction of ASTM Committee C16 on ThermalInsulation and is the direct responsibility
14、 of Subcommittee C16.30 on ThermalMeasurement.Current edition approved May 1, 2007. Published June 2007. Originallyapproved in 1985. Last previous edition approved in 2001 as C 1041 85(2001).2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenc
15、ed 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, PO Box C700, West Co
16、nshohocken, PA 19428-2959, United States.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.
17、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 applications under pseudosteady-state conditions.5. Significance and Use5.1 The major contribution of this practice is that it enablesa measureme
18、nt 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 body.5.2 The primary use of this practice will be for the in-situestimation of thermal transport properties of industrial insula-tion such
19、 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 term testing can be misleading and thispractice is intended to minimize such errors.5.4 Insulation processes with large temperature diffe
20、rencesacross the insulation are best suited to HFT measurementsbecause modest changes in ambient conditions have butminimal effects on HFT output.5.5 While it would be ideal for the HFT and attachmentsystem to have zero thermal resistance, this factor is insignifi-cant to the measured result if kept
21、 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-measuring recordinginstrument accurate to within 0.5 % of the lowest HFT outputanticipated during the test. An integrating voltmeter is
22、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.6.3.1 For measuring the temperature of an insulated surface,such as a pipe under insulation, a 1.5-mm diameter or smaller,flexible ungroun
23、ded thermocouple probe 500 mm long isrecommended.6.3.2 For measuring the temperature of surfaces that can beeasily accessed, 24 gage or smaller, bare bead thermocouplesor equivalent shall be used.6.4 Attachment MaterialsPressure-sensitive adhesivetape, elastic bands, straps, mastic, grease, or other
24、 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, room temperaturevulcanizing elastomer, thermally conducting epoxy, or con-formable pads may be used to provide maximum contactbetween the t
25、est 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 flows aresignificantly changed. This could be measured by surfacetemperature probes or infrared measurement devices.6.6 Surfacing MaterialsC
26、oating, 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 calibrated under the conditions of use; forexample, a calibration under aluminum jacketing on a testsetup in accordance with Test Method C 335, w
27、ould be properfor calibration of an HFT for subsequent testing under similarconditions.7.2 Calibrate HFT to national reference standards in accor-dance with Test Methods C 177, C 335, or C 518. A calibrationcurve showing q/V versus insulation surface temperature (ex-pected to be the HFT temperature)
28、 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 insulated with preformed insulation and jack-eted with aluminum):7.2.1.1 Set up the apparatus in accordance with Test MethodC 335 with p
29、reformed insulation, jacketed with aluminumjacket 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
30、 the HFT away from all joints in theinsulation 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 in
31、to close contact with the insulationsection, making sure that the lap of the belt is on the side of thepipe.)NOTE 1Belt wraps around exterior; shim slips under jacketing (spotHFT).FIG. 1 Flexible Heat Flux Transducers for PipesC 1041 85 (2007)27.2.1.4 Insert a bare temperature sensor about 50 mm awa
32、yfrom 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 electrical output of HFTand temperature at both surfaces of the insulation. Since theoutput of the HFT will fluctuate under most c
33、onditions, agraphical or integrated average of the output of the HFT mustbe made.7.2.1.6 Utilizing q, as may be calculated from Test MethodC 335 data, determine the calibration value for the HFT in q/Vfor at least 3 insulation surface temperatures.7.2.1.7 Plot calibration value (q/V) versus insulati
34、on surfacetemperature (7.2.1.6).7.3 Calibrate the thermocouple in accordance with TestMethod E 220.8. Test Section and HFT and Temperature SensorPlacement Guidelines8.1 Test Section:8.1.1 Selection of the test sections must be appropriate andconsistent with the test objectives. Several test sections
35、 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 properties of a repre-sentative area.8.1.3 Test sections must be amenable to attachment of theHFT with good thermal coupling and
36、 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 thecenter of a formed section of material. Avoid placement onjoints in insulation or laps in jacketing unless joint lo
37、ss 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 of the HFTmust match the surface as closely as possible. With onetransducer an error of 0.01 at the 0.05 emittance leve
38、l 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 block or pipe insulation, including heat lossfrom large joints. When the belt HFT is mounted on reflectiveinsulation jacket
39、ing, 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 tight helix with no overlap, with the belt pulled andrubbed to achieve close contact with the test surface. For fullci
40、rcumferential 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 until a full wrap is made. Any helical lap of the belt pastfull circle should be on the side of the test section, not at t
41、he 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 insertinga thermocouple probe as described in 6.3.1 such that the probelies against the process surface for 150 mm (6 in.
42、) 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 insertion of theprobe should show the maximum DT across the insulation.8.3.1.1 If the process system has built-in tempe
43、rature-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 inserted underthe jacket to measure the surface temperature of the insulationnear the HFT (see 7.2.1.4).8.3.3 When the HFT is
44、 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 insulation surface (6.3.2) such that at least100 mm of the thermocouple is in contact with the surface. Theemittance of the tap
45、e 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 that pseudo steady-state (3.1.2) may beobserved when attained. Depending on exact environmentalconditions, the recorder us
46、ually 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 conditionsto be utilized will depend upon the capabilities of the voltmeterat hand, it is suggested that short integration pe
47、riods 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 steady-state as defined in 3.1.2.9.4 Multiple location data points must be taken and aver-aged.10. Procedure10.1 Selec
48、t 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 factor in the study.10.3 Connect the HFT to the recorder or integrating volt-meter and take readings until pseudo steady-st
49、ate 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 of results.10.7 Measure the physical dimensions of the insulation.10.7.1 Pipe Cover:C 1041 85 (2007)310.7.1.1 Measure the circu
