1、Designation: C 1046 95 (Reapproved 2007)Standard Practice forIn-Situ Measurement of Heat Flux and Temperature onBuilding Envelope Components1This standard is issued under the fixed designation C 1046; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、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 a technique for using heat fluxtransducers (HFTs) and temperature
3、transducers (TTs) in mea-surements of the in-situ dynamic or steady-state thermalbehavior of opaque components of building envelopes. Theapplications for such data include determination of thermalresistances or of thermal time constants. However, such usesare beyond the scope of this practice (for i
4、nformation ondetermining thermal resistances, see Practice C 1155).1.2 Use infrared thermography with this technique to locateappropriate sites for HFTs and TTs (hereafter called sensors),unless subsurface conditions are known.1.3 The values stated in SI units are to be regarded as thestandard. The
5、values given in parentheses are for informationonly.1.4 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
6、 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 168 Terminology Relating to Thermal InsulationC 518 Test Method for Steady-State Thermal TransmissionProperties by Means of the Heat Flow Meter ApparatusC 1060 Practice for Thermographic Inspection of InsulationInstall
7、ations in Envelope Cavities of Frame BuildingsC 1130 Practice for Calibrating Thin Heat Flux TransducersC 1153 Practice for Location of Wet Insulation in RoofingSystems Using Infrared ImagingC 1155 Practice for Determining Thermal Resistance ofBuilding Envelope Components from the In-Situ Data3. Ter
8、minology3.1 DefinitionsFor definition of terms relating to thermalinsulating materials, see Terminology C 168.3.2 Definitions of Terms Specific to This Standard:3.2.1 building envelope componenta portion of the build-ing envelope, such as a wall, roof, floor, window, or door, thathas consistent cons
9、truction.3.2.1.1 DiscussionFor example, an exterior stud wallwould be a building envelope component, whereas a layerthereof would not be.3.2.2 thermal time constantthe time necessary for a stepchange in temperature on one side of an item (for example, anHFT or building component) to cause the corres
10、pondingchange in heat flux on the other side to reach 63.2 % of its newequilibrium value where one-dimensional heat flow occurs. Itis a function of the thickness, placement, and thermal diffusiv-ity (see Appendix X1) of each constituent layer of the item.3.2.2.1 Discussiont 5twhen qt!5q11 q22 q1! l
11、2 et/t!where:q1= is the previous equilibrium heat flux, andq2= is the new heat flux after the step change.3.3 Symbols Applied to the Terms Used in This Standard:E = measured voltage from the HFT, typically in mV,q = heat flux, W/m2(Btu/hft2),S = heat-flux transducer conversion factor that relates th
12、eoutput of the HFT, E,toq through the HFT for theconditions of the test, W/m2V (Btu/hft2mV). Thismay be a function of temperature, heat flux, and otherfactors in the environment as discussed in Section 7.This may also be expressed as S(T) to connote afunction of temperature,T = temperature, K (C, R,
13、 or F),t = time, s (hours, days), andt = thermal time constant, s (hours, days).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 May 1, 2007. Published May 2007.
14、Originallyapproved in 1985. Last previous edition approved in 2001 as C 1046 95 (2001).2For 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 Summar
15、y page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Practice4.1 Heat flux transducers are installed on or within abuilding envelope component in conjunction with temperaturetransducers, as required
16、. Heat flux through a surface is influ-enced by temperature gradients, thermal conductance, heatcapacity, density and geometry of the test section, and byconvective and radiative coefficients. The resultant heat fluxesare determined by multiplying a conversion factor S of the HFTby its electrical ou
17、tput. The S values shall have been obtainedaccording to Practice C 1130.5. Significance and Use5.1 Traditionally, HFTs have been incorporated into labora-tory testing devices, such as the heat flow meter apparatus (TestMethod C 518), that employ controlled temperatures and heatflow paths to effect a
18、 thermal measurement. The application ofheat flux transducers and temperature transducers to buildingcomponents in situ can produce quantitative information aboutbuilding thermal performance that reflects the existing proper-ties of the building under actual thermal conditions. Theliterature contain
19、s a sample of reports on how these measure-ments have been used (1-8).35.2 The major advantage of this practice is the potentialsimplicity and ease of application of the sensors. To avoidspurious information, users of HFTs shall: (1) employ anappropriate S,(2) mask the sensors properly, (3) accommod
20、atethe time constants of the sensors and the building components,and (4) account for possible distortions of any heat flow pathsattributable to the nature of the building construction or thelocation, size, and thermal resistance of the transducers.5.3 The user of HFTs and TTs for measurements on bui
21、ld-ings shall understand principles of heat flux in buildingcomponents and have competence to accommodate the follow-ing:5.3.1 Choose sensor sites using building plans, specifica-tions and thermography to determine that the measurementrepresents the required conditions.5.3.2 A single HFT site is not
22、 representative of a buildingcomponent. The measurement at an HFT site represents theconditions at the sensing location of the HFT. Use thermogra-phy appropriately to identify average and extreme conditionsand large surface areas for integration. Use multiple sensorsites to assess overall performanc
23、e of a building component.5.3.3 A given HFT calibration is not applicable for allmeasurements. The HFT disturbs heat flow at the measurementsite in a manner unique to the surrounding materials (9, 10);this affects the conversion constant, S, to be used. The usershall take into account the conditions
24、 of measurement asoutlined in 7.1.1. In extreme cases, the sensor is the mostsignificant thermal feature at the location where it has beenplaced, for example, on a sheet metal component. In such acase, meaningful measurements are difficult to achieve. Theuser shall confirm the conversion factor, S,
25、prior to use of theHFT to avoid calibration errors. See Section 7.5.3.4 The user shall be prepared to accommodate non-steady-state thermal conditions in employing the measurementtechnique described in this practice. This requires obtainingdata over long periods, perhaps several days, depending on th
26、etype of building component and on temperature changes.5.3.5 Heat flux has a component parallel to the plane of theHFT. The user shall be able to minimize or accommodate thisfactor.6. Apparatus6.1 Essential equipment for measuring heat flux and tem-perature includes the following:6.1.1 Heat Flux Tra
27、nsducerA rigid or flexible device (seeAppendix X2) in a durable housing, composed of a thermopile(or equivalent) for sensing the temperature difference across athin thermal resistive layer, which produces a voltage outputthat is a function of the corresponding heat flux and thegeometry and material
28、properties of the HFT.NOTE 1All calibrations relating output voltage to heat flux shallconform to Practice C 1130 and pertain to the measurement at hand.Manufacturers calibrations supplied with HFTs often do not conformwith Practice C 1130. Obtain the HFT conversion factor as described inSection 8 o
29、f Practice C 1130.6.1.2 Temperature TransducerA thermocouple, resistancethermal device (RTD), or thermistor for measuring tempera-tures on or within the construction, or for measuring airtemperatures. Some HFTs incorporate thermocouples.6.1.3 RecorderAn instrument that reads sensor outputvoltage and
30、 records either the voltage, heat flux, or temperaturevalues calculated from appropriate formulas, with durableoutput (for example, magnetic tape, magnetic disk, punch tape,printer, or plotter).6.1.4 Attachment MaterialsPressure-sensitive tape, adhe-sive, or other means for holding heat flux and tem
31、peraturetransducers in place on the test surface or within the construc-tion.6.1.5 Thermal Contact MaterialsGel toothpaste, heat sinkgrease, petroleum jelly, or other means to improve thermalcontact between an irregular surface and a smooth HFT.6.1.6 Absorptance and Emittance Control SuppliesCoating
32、s or sheet material to match the radiative absorptanceand emittance of the sensor with that of the surroundingsurfaces.7. HFT Signal Conversion7.1 The conversion factor (S) is a function of the HFTdesign and the thermal environment surrounding the HFT (8,9).Adifference between thermal conductivities
33、 of the HFT andits surroundings causes it to act either as a partial blockade orconduit for heat flux. Radiative heat passes into the HFT at adifferent rate than it does into the surrounding surface, depend-ing on the mismatch between the absorptivities of HFT andsurface. The presence of air moving
34、across an HFT can changethe conductance of the air film at the HFT and cause the heatflux through the HFT to differ from that through the surround-ing surface.3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.C 1046 95 (2007)27.1.1 Determine S according
35、to the procedure outlined inPractice C 1130, as appropriate to the conditions of use, that is,surface-mounted or embedded and surrounded by materialsthat will be present.7.2 Confirm that the time constant of the HFT is much lessthan the time constant of the building component to bemeasured if the te
36、mperatures throughout the HFT and theconstruction will not be steady state. If the mass of an HFT ofa certain area is less than one fiftieth of the mass of the samearea of building component, then its time constant is smallenough. If not, then estimate the thicknesses and thermaldiffusivities of the
37、 constituent layers of the HFT and thebuilding component, using Appendix X1 or other recognizedtechnique, to determine whether the time constant of the HFTis less than one fiftieth of that of the components timeconstant.8. Selection of Sensor Sites8.1 The user shall choose a place in the constructio
38、n forsiting the HFTs where one-dimensional heat flow perpendicu-lar to the exterior surfaces occurs, unless the user is prepared todeal with multidimensional heat flow in the analysis of thedata.NOTE 2For example, a sensor site in the center of a fully insulatedstud cavity represents heat flow perpe
39、ndicular to the wall surface, whereasa location near a stud or blocking does not. A wall incorporating concretemasonry units has significant multidimensional heat flow through theconcrete webs and possible air convection cells in the block cores.(Experience indicates, however, that the face of a con
40、crete masonry unitdistributes heat flux sufficiently that HFT placement is insensitive tolocation on the block.) Similarly, an empty stud cavity has convection asa potential lateral heat flow mechanism and a masonry or stone wall hasvertical heat conduction near the ground level. Air leakage can als
41、o be asource of multidimensional heat flow.8.2 Do not place the HFTs where they contribute more than1 % additional resistance to the construction subject to thermalmeasurement, unless the thermal properties of the HFTs arewell known and the analysis technique is appropriate.8.3 Do not place HFTs on
42、surfaces with high lateral con-ductance, unless the S has been confirmed for the precisecondition.8.4 Install HFTs either on an indoor surface of the compo-nent if the construction is complete or within a buildingcomponent when the component is being constructed andretrieval is not required. Infrare
43、d thermography is requiredwhen the internal configuration of the component is poorlyknown. Seek perpendicular flow, and avoid unforeseen thermalanomalies.8.5 Use infrared thermography to determine the character-istics of candidate sensor sites on the building component whenthe internal configuration
44、 of the component is poorly known(see Practices C 1060 and C 1153).NOTE 3Close visual inspection of a stud wall can often reveal thelocations of framing members when there are slight imperfections abovenailheads, but thermography can reveal whether or not there is unexpectedcross blocking, air leaka
45、ge, or convection owing to missing, incorrectlyapplied, or shifted insulation.NOTE 4Thermographic instruments produce a two-dimensional im-age of a surface by measuring thermal radiation emanating from thatsurface. A temperature gradient on the surface is seen as a variation incontrast or in pseudoc
46、olor on a viewer screen. If the radiation gradients arecaused by heat transfer variations in the wall because of thermalanomalies, these anomalies and their locations are made visible. Certainthermographic patterns can be recognized as framing, air leakage, orconvection.8.6 Determine whether to depl
47、oy sensors in a line or insome other arrangement, based on knowledge of the compo-nents internal configuration. Note that a wall with suspectedinternal convection requires, at a minimum, sensors at the top,bottom, and center of the suspected convective area.9. Test Procedures9.1 Sensor Site Selectio
48、nSelect appropriate sensor sitesaccording to Section 8. The HFT shall cover a region ofuniform heat flux on the chosen site. If the HFT covers a regionwith significantly nonuniform heat flux, then demonstrate thatthe HFT correctly averages the input it receives.9.2 Permanent Sensor Installation:9.2.
49、1 Sensors built into the construction offer more reliableresults than sensors mounted on an exterior surface, becausethey are usually protected from radiant heat sources andconvection, which may affect the sensor differently than thesurrounding building material. The measurement is also likelyto have less variance.9.2.2 Tape or glue the HFTs to a smooth surface within theconstruction to ensure good thermal contact.9.2.3 Position temperature transducers on and within theconstruction, as required, to obtain temperature gradientsacross its thickness. Place s
