1、Designation: D 4611 08Standard Test Method forSpecific Heat of Rock and Soil1This standard is issued under the fixed designation D 4611; 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 parenth
2、eses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of instanta-neous and mean specific heat of rock and soil.1.2 This test method employs the classical method of
3、mixtures. This provides procedures and apparatus simpler thanthose generally used in scientific calorimetry, an accuracy thatis adequate for most rocks and soils, and a degree of precisionthat is reproducible by laboratory technicians of average skill.While this test method was developed for testing
4、 rock and soil,it is easily adaptable to measuring the specific heat of othermaterials.1.3 The testing procedure provides an instantaneous specificheat over the temperature 25 to 300C or a mean specific heatin that temperature range.1.4 The test procedure is limited to dry samples.1.5 The values sta
5、ted in SI units are to be regarded as thestandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with
6、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:2C 303 Test Method for Dimensions and Density of Pre-formed Block and
7、BoardType Thermal InsulationC 351 Test Method for Mean Specific Heat of ThermalInsulationD 618 Practice for Conditioning Plastics for TestingD 2766 Test Method for Specific Heat of Liquids and SolidsE 230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE 3
8、44 Terminology Relating to Thermometry and Hydrom-etry3. Terminology3.1 Definitions:3.1.1 instantaneous specific heatthe rate of change ofsample enthalpy, h, per unit mass with respect to temperature,T, at constant pressure, p,cp5 dh/dT!p(1)3.1.2 mean specific heatthe quantity of heat required tocha
9、nge the temperature of a unit mass of a substance onedegree, measured as the average quantity over the temperaturerange specified. (It is distinguished from true specific heat bybeing an average rather than a point value. The unit ofmeasurement is joule per kilogram kelvin, J/kgK).3.1.3 thermal capa
10、citythe amount of heat necessary tochange the temperature of the body one degree. For a homo-geneous body, it is the product of mass and specific heat. Fora nonhomogeneous body, it is the sum of the products of massand specific heat of the individual constituents. Thermalcapacity has the units of jo
11、ule per kelvin, J/K.3.1.4 thermal diffusivitythe ratio of thermal conductivityof a substance to the product of its density and specific heat.Common unit for this property is m2/s.3.2 Symbols:3.2.1 DHenthalpy change (J/kg).3.2.2 mcpthermal capacity (J/K).3.2.3 Tmfinal temperature of the mixture obtai
12、ned byextrapolation (K).3.2.4 Tctemperature of the calorimeter immediately priorto drop obtained by extrapolation.3.2.5 Thtemperature of capsule and sample, capsule orstandard in the heater prior to drop (K).3.2.6 DTtemperature difference.3.2.7 cpmean specific heat (J/kgK).3.2.8 cpinstantaneous spec
13、ific heat (J/kgK).4. Summary of Test Method4.1 The method of mixtures consists essentially of adding aknown mass of material at a known temperature to a knownmass of calorimetric fluid at a known lower temperature anddetermining the equilibrium temperature that results. The heat1This test method is
14、under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved July 1, 2008. Published July 2008. Originally approvedin 1986. Last previous edition approved in 2004 as D 4611 86 (2004).2For referenced AST
15、M standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandardsvolume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoc
16、ken, PA 19428-2959, United States.absorbed by the fluid and containing vessel can be calculatedfrom calibrations and this value equated to the expression forthe heat given up by the hot material. From this equation, theunknown specific heat can be calculated. If only one drop froma single temperatur
17、e is performed, then only the mean specificheat can be calculated. If several drops are performed, theinstantaneous specific heat can be calculated.5. Significance and Use5.1 Specific heat is a basic thermodynamic property of allsubstances. The value of specific heat depends upon chemicalcomposition
18、 and temperature. The rate of temperature diffusionthrough a material, thermal diffusivity, is a function of specificheat; therefore, specific heat is an essential property of rockand soil when these materials are used under conditions ofunsteady or transient heat flow.6. Apparatus6.1 Calorimeter an
19、d AccessoriesThe calorimeter shall bean unlagged Dewar flask. The capacity of the Dewar flask shallbe such as to yielda1to5Ktemperature rise of the receiverfluid with average sample size used during testing (Note 1).The flask shall have an insulated cover or stopper. Otheraccessories shall include a
20、 magnetic stirrer equipped with aspeed regulating device.NOTE 1Typical volumes are approximately 500 to 750 mL with rockor soil samples of 50 g in thin wall stainless steel containers.6.2 Calorimeter Temperature-Sensing DeviceAtemperature-sensing device capable of 0.0025 K resolution andcovering a m
21、inimum of 5 K range shall be used.NOTE 2A suitable temperature sensor is a multijunction thermopiletypically referenced to an ice bath.6.3 Calorimeter FluidThe calorimeter fluid should be ahigh specific heat fluid, stable to 250 to 300C and having alow vapor pressure. Silicone based fluids are frequ
22、ently used.6.4 HeaterThe heater shall be designed to provide auniform heating zone. A maximum variation of 61%ofthemean heater temperature along the heater length correspondingto the sample is permitted.NOTE 3Typically, open-end radiation type heaters similar to thecylindrical device shown in Fig. 1
23、 are used. Such heaters are usuallyheated by electricity; however, other means of heating are acceptable aslong as the requirements for the heater can be met. The relativedimensions of the heater and capsule shall be such that the specimen willbe heated to a uniform and constant temperature as requi
24、red. The heatershould be provided with an insulated removable cover designed to permitpassage of sample capsule temperature sensing devices and suspensionwire. The bottom should be closed with a removable insulated cover topermit free dropping of the capsule. Typically, the heater assembly ismounted
25、 so it can be swung quickly into place over the calorimeterimmediately prior to drop and swung away after the sample has beendropped.6.5 CapsuleThe capsule shall be of the hermeticallysealed type. The capsule heat capacity should be minimizedand in no instance should be greater than the heat capacit
26、y ofthe sample. The capsule should be made of high conductivitymaterial. Typically, capsules are thin wall copper or stainlesssteel containers.6.6 Specimen Temperature Readout DeviceA convenientmethod of measuring the temperature of the sample in theheater unit shall be provided. It is desirable to
27、measure thesample temperature inside the container; however, measuringof the outside of the container is permitted. Typically, athermocouple calibrated to the special limits of error specifiedin EMF Tables E 230 is used for sample temperature readout.The temperature shall be measured to 61 % of the
28、testtemperature.6.7 Test RoomThe room temperature in which the testsare conducted shall be maintained at 23 6 2C.6.8 Calibration StandardsAminimum of three calibrationstandards are required. The standards must be traceable to theNational Institute of Standards andTechnology (NIST) or otherNational M
29、etrology Institute.7. Test Specimen7.1 FormIn order to increase the accuracy of this testmethod, the sample mass should be maximized for a givencapsule volume. This usually means, for dense rocks, that thesample should be machined to fit the container tightly. How-ever, crushed rocks in powder form
30、or soils can be tested witha decrease in accuracy due to the lower contribution of thesample to the total measured heat capacity of the sample/container combination. Porous rocks are usually tested inpowder form.7.2 Sample Size and Number of SamplesThe sample shallbe representative of the type of ro
31、ck or soil tested. In caseswhere inhomogeneity is a problem, multiple samples of thesame rock or soil shall be tested. In case of doubt, multiplesamples shall be used.7.3 Sample MachiningSamples shall be machined in sucha manner that the machining process does not affect the specificheat properties
32、of the sample. Any fluids used in the processshall be compatible with the sample and removed from thesample prior to tests.FIG. 1 Specific Ileal CalorimeterD46110827.4 The sample shall dry to constant weight in accordancewith Method D 618, Procedure B, prior to testing.8. System Calibration8.1 Calor
33、imeter Fluid CalibrationPerform a total of 15drops in order to calibrate the receiver fluid. Drop threestandards from five temperatures each approximately evenlyspaced from 100 to 300C.8.2 Calculation of the Heat Capacity of the ReceiverAfterthe 15 drops have been performed as described in Section 9
34、,calculate the mcpof the receiver for each drop (see 3.2). Plotthe results as a function of drop temperature. The results (ateach drop temperature) should be within 61.5 %. Plot astraight line through the averaged results at each temperature.This is the calibration curve to be used in data reduction
35、. Toallow for minor loss in calibration fluid, the mcpcan beadjusted each time for weight loss. Maximum total weight lossshall be less than 5 %.8.3 System VerificationEvery 10 drops or every 24 h,check the calibration of the receiver by dropping one standardfrom 200C. The result must be within 61.5
36、% of the calibra-tion curve determined in 8.2. If this is not the case, then thereceiver fluid must be recalibrated or changed and the new fluidcalibrated.8.4 Capsule CalibrationThe capsule shall be calibratedby testing it in accordance with the sample testing procedure.The capsule shall be recalibr
37、ated every time a change is made(that is, a new gasket), and its calibration shall be verified witha single drop, once a week.9. Procedure9.1 Dry the sample to constant weight in accordance withMethod D 618, Procedure B. Record the weight to 0.1 %.9.2 Measure the mass of the calorimeter fluid in the
38、 receiver(Note 4) to 0.1 %, and cover the Dewar.9.3 Install the sample in the capsule and seal the capsule.Suspend the sealed capsule in the heating system and monitorthe temperature of the sample. Record sample temperature atleast once every five minutes until thermal equilibrium isachieved (Note 5
39、). It shall be assumed that thermal equilibriumis achieved when the sample temperature is within 0.5 % of thefurnace temperature and the sample temperature does notchange by more than 0.02C/min over a 10-min period.9.4 During the entire time that the sample temperature isequilibrating in the furnace
40、, the temperature of the receivershould be monitored and recorded to 0.0025C at least onceevery 5 min. If there is a drift in the receiver temperature, itshould be constant and less than 0.05C/min.9.5 After the sample has reached thermal equilibrium,position the furnace over the Dewar (Note 6). Mome
41、ntarilyremove the cover from the Dewar and drop the sample into thecalorimeter fluid. Replace the cover immediately after the drop.If during the drop, the sample hits anything prior to reachingthe calorimeter fluid, the drop shall be disregarded and re-peated.9.6 Continuously monitor the temperature
42、 of the calorimeterfluid after the drop until the temperature drift is less than orequal to the drift just prior to the drop.NOTE 4A common method for measuring the mass of the fluid is tomeasure the total mass of the Dewar and fluid and mass of the emptyDewar. The mass of the fluid is the differenc
43、e in the two masses.NOTE 5The time required for the sample to reach thermal equilibriumdepends on such factors as furnace design, capsule design, sample size,and thermal diffusivity of the capsule and sample.NOTE 6For swinging furnaces, the time that the furnace is over theDewar should be minimized.
44、10. Calculation10.1 Plot the temperature of the calorimeter fluid versustime. An example of a temperature-time plot is shown in Fig.2.10.2 From the temperature-time plot, determine the value ofTmand Tcby extrapolation as illustrated in Fig. 2. Calculate thetemperature change of the bath as follows:D
45、Tcal5 Tm2 Tc(2)10.3 From the calibration graphs, find the (mcp)calof thecalorimeter for the given drop temperature Th. Calculate theenthalpy change of the calorimeter as follows:DHcal5 mcp!cal3DTcal(3)10.4 The heat released to the calorimeter is equal to the sumof the enthalpy changes of the sample
46、and capsule, as follows:DHcal5 mcp!cap1 mcp!samp#Th2 Tm! (4)10.5 Therefore, the enthalpy change of the sample can becalculated from the following equation:mcp!sampTh2 Tm! 5 mcp!cal3DTcal2 mcp!capTh2 Tm! (5)10.6 If only one drop is performed, then the mean specificheat of the sample can be calculated
47、 as follows:cp samp.5mcp!cal3DTcal2 mcp!capTh2 Tm!msampTh2 Tm!(6)10.7 If the instantaneous specific heat is to be determined,perform drops from a minimum of three temperatures. Calcu-late the enthalpy change of the sample for each drop and plotas a function of drop temperature. The enthalpy change s
48、houldFIG. 2 Curve Showing Relation of Temperature to Time for aTypical Specific Heat DeterminationD4611083be zero at Tm. Use a curve fitting routine to fit the data andobtain a polynominal equation. Use DH =0atTmas one of thepoints.10.8 Calculate the instantaneous specific heat by differenti-ating t
49、he enthalpy change versus drop temperature curve asfollows:cpsamp5dDHsamp!dT(7)10.9 Calculation of Capsule Calibration Perform capsulecalibration prior to test drops by dropping empty capsules,calculating the enthalpy change, and plotting it versus droptemperature.After an adequate curve has been established overthe temperature range of interest, the enthalpy change of thecapsule for a given test can be picked off the curve. Usually, aminimum of five drops is required to characterize the capsule.11. Report11.1 The report s
