1、Designation: E 422 05Standard Test Method forMeasuring Heat Flux Using a Water-Cooled Calorimeter1This standard is issued under the fixed designation E 422; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 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 test method covers the measurement of a steadyheat flux to a given water-cooled surface by means of a systemenergy balance.1.2
3、 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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-p
4、riate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 235 Specification for Thermocouples, Sheathed, Type K,for Nuclear or for Other High-Reliability Applications3. Summary of Test Method3.1 A measure of
5、 the heat flux to a given water-cooledsurface is based upon the following measurements: (1) thewater mass flow rate and (2) the temperature rise of coolantwater. The heat flux is determined numerically by multiplyingthe water coolant flow rate by the specific heat and rise intemperature of the water
6、 and dividing this value by the surfacearea across which heat has been transferred.3.2 The apparatus for measuring heat flux by the energy-balance technique is illustrated schematically in Fig. 1.Itisatypical constant-flow water calorimeter used to measure stag-nation region heat flux to a flat-face
7、d specimen. Other calo-rimeter shapes can also be easily used. The heat flux ismeasured using the central circular sensing area, shown in Fig.1. The water-cooled annular guard ring serves the purpose ofpreventing heat transfer to the sides of the calorimeter andestablishes flat-plate flow. An energy
8、 balance on the system(the centrally located calorimeter in Fig. 1) requires that theenergy crossing the sensing surface (A,inFig. 1)ofthecalorimeter be equated to the energy absorbed by the calorim-eter cooling water. Interpretation of the data obtained is notwithin the scope of this discussion; co
9、nsequently, such effectsas recombination efficiency of the surface and thermochemicalstate of the boundary layer are outside the scope of this testmethod. It should be noted that recombination effects at lowpressures can cause serious discrepancies in heat flux measure-ments (such as discussed in Re
10、f (1)3depending upon thesurface material on the calorimeter.3.3 For the particular control volume cited, the energybalance can be written as follows:ECAL5 mCpDT02DT1!#/A (1)where:ECAL= energy flux transferred to calorimeter face, Wm2m = mass flow rate of coolant water, kgs1Cp= water specific heat, J
11、kg1K1,DT0= T02 T01calorimeter water bulk temperature riseduring operation, K,DT1= T2 T1= calorimeter water apparent bulk tem-perature rise before operation, K,T02= water exhaust bulk temperature during operation,K,T01= water inlet bulk temperature during operation, K,T2= water exhaust bulk temperatu
12、re before operation,K,T1= water inlet bulk temperature before operation, K,andA = sensing surface area of calorimeter, m2.3.4 An examination of Eq 1 shows that to obtain a value ofthe energy transferred to the calorimeter, measurements mustbe made of the water coolant flow rate, the temperature rise
13、 ofthe coolant, and the surface area across which heat is trans-ferred. With regard to the latter quantity it is assumed that thesurface area to which heat is transferred is well defined. As isindicated in Fig. 1, the design of the calorimeter is such that theheat transfer area is confined by design
14、 to the front or directlyheated surface. To minimize side heating or side heat losses, awater-cooled guard ring or shroud is utilized and is separated1This test method is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and is the direct responsibi
15、lity ofSubcommittee E21.08 on Thermal Protection.Current edition approved Sept. 15, 2005. Published September 2005. Originallyapproved in 1971. Last previous edition approved in 1999 as E 422 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
16、serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis test method.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
17、West Conshohocken, PA 19428-2959, United States.physically from the calorimeter by means of an air gap and lowconductivity bushing such as nylon. The air gap is recom-mended to be no more than 0.5 mm on the radius. Thus, ifsevere pressure variations exist across the face of the calorim-eter, side he
18、ating caused by flow into and out of the air gap willbe minimized. Also, since the water-cooled calorimeter andguard ring operate at low surface temperatures (usually lowerthan 100C) heat losses across the gap by radiant interchangeare negligible and consequently no special calorimeter surfacegap fi
19、nishes are necessary. Depending upon the size of thecalorimeter surface, large variations in heat flux may existacross the face of the calorimeter. Consequently, the measuredheat flux represents an average heat flux over the surface areaof the water-cooled calorimeter. The water-cooled calorimeterca
20、n be used to measure heat-flux levels over a range from 10kW/m2to 60 MW/m2.4. Significance and Use4.1 The purpose of this test method is to measure the heatflux to a water-cooled surface for purposes of calibration of thethermal environment into which test specimens are placed forevaluation. If the
21、calorimeter and holder size, shape, andsurface finish are identical to that of the test specimen, themeasured heat flux to the calorimeter is presumed to be thesame as that to the samples heated surface. The measured heatflux is one of the important parameters for correlating thebehavior of material
22、s.4.2 The water-cooled calorimeter is one of several calorim-eter concepts used to measure heat flux. The prime drawback isits long response time, that is, the time required to achievesteady-state operation. To calculate energy added to the coolantwater, accurate measurements of the rise in coolant
23、tempera-ture are needed, all energy losses should be minimized, andsteady-state conditions must exist both in the thermal environ-ment and fluid flow of the calorimeter.4.3 Regardless of the source of energy input to the water-cooled calorimeter surface (radiative, convective, or combina-tions there
24、of) the measurement is averaged over the surfaceactive area of the calorimeter. If the water-cooled calorimeter isused to measure only radiative flux or combined convective-radiative heat-flux rates, then the surface reflectivity of thecalorimeter shall be measured over the wavelength region ofinter
25、est (depending on the source of radiant energy). If non-uniformities exist in the gas stream, a large surface areawater-cooled calorimeter would tend to smooth or average anyvariations. Consequently, it is advisable that the size of thecalorimeter be limited to relatively small surface areas andappl
26、ied to where the heat-flux is uniform. Where large samplesare tested it is recommended that a number of smaller diameterwater-cooled calorimeters be used (rather than one large unit).These shall be located across the heated surface such that aheat-flux distribution can be described. With this, a mor
27、edetailed heat-flux measurement can be applied to the specimentest and more information can be deduced from the test.5. Apparatus5.1 GeneralThe apparatus shall consist of a water-cooledcalorimeter and the necessary instrumentation to measure theheat transferred to the calorimeter. Although the recom
28、mendedinstrumentation accuracies are state-of-the-art values, morerugged and higher accuracy instrumentation may be requiredfor high pressure and high heat-flux applications. A number ofmaterials can be used to fabricate the calorimeter, but OFHC(oxygen free high conductivity) copper is often prefer
29、redbecause of its superior thermal properties.5.2 Coolant Flow MeasurementThe water flow rate toeach component of the calorimeter shall be chosen to cool theapparatus adequately and to ensure accurately measurable risein water temperature. The error in water flow rate measurementshall be not more th
30、an 62 %. Suitable equipment that can beused is listed in Ref (2) and includes turbine flowmeters,variable area flowmeters, etc. Care must be exercised in the useof all these devices. In particular, it is recommended thatappropriate filters be placed in all water inlet lines to preventparticles or un
31、necessary deposits from being carried to thewater-cooling passages, pipe, and meter walls. Water flow ratesand pressure shall be adjusted to ensure that no bubbles areformed (no boiling). If practical, the water flowmeters shall beplaced upstream of the calorimeter in straight portions of thepiping.
32、 The flowmeter device shall be checked and calibratedperiodically. Pressure gages, if required, shall be used inaccordance with the manufacturers instructions and calibra-tion charts.FIG. 1 Steady-State Water-Cooled Calorimeter.E4220525.3 Coolant Temperature MeasurementThe method oftemperature measu
33、rement must be sufficiently sensitive andreliable to ensure accurate measurement of the coolant watertemperature rise. Procedures similar to those given in Specifi-cation E 235, Type K, and Ref (3) should be followed in thecalibration and preparation of temperature sensors. The bulk oraverage temper
34、ature of the coolant shall be measured at theinlet and outlet lines of each cooled unit. The error inmeasurement of temperature difference between inlet andoutlet shall be not more than 61 %. The water temperatureindicating devices shall be placed as close as practical to thecalorimeters heated surf
35、ace in the inlet and outlet lines.However, care must be exercised so as not to place thetemperature sensors where there is energy exchange betweenthe incoming (cold) water and the outgoing (heated) water.This occurs most readily at flow dividers and at the calorimetersensing surface. No additional a
36、pparatus shall be placed in theline between the temperature sensor and the heat source. Thetemperature measurements shall be recorded continuously toverify that steady-state operation has been achieved. Reference(2) lists a variety of commercially available temperaturesensors. Temperature sensors wh
37、ich are applicable includeliquid-in-glass thermometers, thermopiles, thermocouples, andthermistors. During operation of the heat source, care should betaken to minimize deposits on the temperature sensors and toeliminate any possibility of sensor heating because of specimenradiation to the sensor. I
38、n addition, all water lines should beshielded from direct-flow impingement or radiation from thetest environment.5.3.1 If at all practical a thermocouple shall be placed on thewater-cooled side of the heated calorimeter surface. Althoughthis surface temperature (water side) measurement is not useddi
39、rectly in the calculation of heat flux it is necessary for thecalculation of the surface temperature (front face) used in thecorrection of the measured heat flux to walls of differenttemperatures.5.4 Recording Means:5.4.1 Since measurement of the energy transfer requires thatthe calorimeter operate
40、as a steady state device, all calculationswill use only measurements taken after it has been establishedthat the device has achieved steady operating levels. To assuresteady flow or operating conditions the above mentionedparameters shall be continuously recorded such that instanta-neous measurement
41、s are available to establish a measure ofsteady-state operation. Wherever possible it is highly desirablethat the differential temperature (DT) be made of the desiredparameters rather than absolute measurements.5.4.2 In all cases, parameters of interest, such as water flowrates and cooling water tem
42、perature rises should be automati-cally recorded throughout the measurement period. Recordingspeed or sampling frequency will depend on the variations ofthe parameters being recorded. When a strip chart recorder isused, the response time of the recorder shall be1sorless forfull-scale deflection. Tim
43、ing marks should be an integral partof the recorder with a minimum requirement of 1/s.6. Procedure6.1 It is essential that the environment be at steady-stateconditions prior to testing if the water-cooled calorimeter is togive a representative measure of the heat flux.6.2 After a sufficient length o
44、f time has elapsed to assureconstant mass flow of water as well as constant inlet and outletwater temperature, place the system into the heat-sourceenvironment. Steady-state operation has been assured if theinlet and exhaust water temperature, and water flow rates aresteady and not changing with tim
45、e. In particular the water flowrates should not change during operation. After removing thecalorimeter from the environment, record the inlet watertemperature and flow rates so that they can be compared withpretest values. Changes between pre- and post-test watertemperature rise may indicate deposit
46、 buildups on the calorim-eter backface or cooling passages which may alter the results ofthe measurement of energy transfer.6.3 To ensure consistent heat-flux data, it is recommendedthat measurements be repeated with the same apparatus. Afurther check on the measurement of heat flux using awater-coo
47、led calorimeter would be to use a different mass flowof water through the calorimeter for different test runs. Nosignificant difference in heat-flux measurements should benoted with the change in water flow rate for different test runs.7. Heat-Flux Calculation7.1 The quantities as defined by Eq 1 sh
48、all be calculatedbased on the bulk or average temperature rise of the coolantwater for each water-cooled section of the calorimeter. Thechoice of units shall be consistent with the measured quantities.7.2 Variance analyses of heat-source conditions shall pro-vide a sound basis for estimation of the
49、reproducibility of thethermal environment. Refs (4) and (5) may provide a basis forerror analysis of the measurements.8. Report8.1 In reporting the results of the measurement tests, thefollowing steady-state data shall be reported:8.1.1 Dimensions of the calorimeter configuration activesurface and guard ring,8.1.2 Calorimeter coolant water flow rate,8.1.3 Temperature rise of calorimeter coolant water,8.1.4 Calculated heat flux,8.1.5 Front surface temperature (if measured or calculated),and8.1.6 Variance of results.9. Measurement Uncertainty9.1 There are a number of
