1、Designation: D 4611 86 (Reapproved 2004)Standard 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
2、 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 determination of instanta-neous and mean specific heat of rock and soil.1.2 This test method employs the
3、classical method ofmixtures. 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 de
4、veloped for testing 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
5、.1.5 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. Referenced
6、Documents2.1 ASTM Standards:2C 303 Test Method for Density of Preformed Block-TypeThermal InsulationC 351 Test Method for Mean Specific Heat of ThermalInsulationD 618 Practice for Conditioning Plastics and ElectricalInsulating Materials for TestingD 2766 Test Method for Specific Heat of Liquids and
7、SolidsE 230 Temperature-Electromotive Force (EMF) Tables forThermocouplesE 344 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,
8、 p,cp5 dh/dT!p(1)3.1.2 mean specific heatthe quantity of heat required tochange 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. Th
9、e unit ofmeasurement is joule per kilogram Klvin, J/kgK).3.1.3 thermal capacitythe 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 specif
10、ic heat of the individual constituents. Thermalcapacity has the units of joule 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
11、.2 mcp thermal capacity (J/K).3.2.3 Tm final temperature of the mixture obtained byextrapolation (K).3.2.4 Tc temperature of the calorimeter immediately priorto drop obtained by extrapolation.3.2.5 Th temperature of capsule and sample, capsule orstandard in the heater prior to drop (K).3.2.6 DTtempe
12、rature difference.3.2.7 cpmean specific heat (J/kgK).3.2.8 cp instantaneous specific 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 anddet
13、ermining the equilibrium temperature that results. The heatabsorbed by the fluid and containing vessel can be calculatedfrom calibrations and this value equated to the expression for1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of S
14、ubcommittee D18.12 on Rock Mechanics.Current edition approved Nov. 1, 2004. Published December 2004. Originallyapproved in 1986. Last previous edition approved in 2000 as D 461186(2000).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
15、tm.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 Conshohocken, PA 19428-2959, United States.the heat given up by the hot material. From this equation, th
16、eunknown specific heat can be calculated. If only one drop froma single temperature 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 prop
17、erty of allsubstances. The value of specific heat depends upon chemicalcomposition 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
18、 under conditions ofunsteady or transient heat flow.6. Apparatus6.1 Calorimeter and 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).Th
19、e flask shall have an insulated cover or stopper. Otheraccessories shall include a 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-Sensin
20、g DeviceAtemperature-sensing device capable of 0.0025 K resolution andcovering a minimum 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, sta
21、ble to 250 to 300C and having alow vapor pressure. Silicone based fluids are frequently 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
22、, open-end radiation type heaters similar to thecylindrical device shown in Fig. 1 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 s
23、uch that the specimen willbe heated to a uniform and constant temperature as required. 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 cov
24、er topermit free dropping of the capsule. Typically, the heater assembly ismounted 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 capsules heat cap
25、acity should be minimizedand in no instance should be greater than the heat capacity 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
26、 temperature of the sample in theheater unit shall be provided. It is desirable to 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 us
27、ed for sample temperature readout.The temperature shall be measured to 61 % of the 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 trac
28、eable to theU.S. National Bureau of Standards (NBS) or other recognizedstandard.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 t
29、he container tightly. How-ever, crushed rocks in powder form 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
30、of Samples The sample shallbe representative of the type of rock 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
31、machining process does not affect the specificheat properties of the sample. Any fluids used in the processshall be compatible with the sample and removed from thesample prior to tests.7.4 The sample shall dry to constant weight in accordancewith Method D 618, Procedure B, prior to testing.FIG. 1 Sp
32、ecific Ileal CalorimeterD 4611 86 (2004)28. System Calibration8.1 Calorimeter Fluid Calibration Perform 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
33、 ReceiverAfterthe 15 drops have been performed as described in Section 9,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 eac
34、h temperature.This is the calibration curve to be used in data reduction. 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 rec
35、eiver by dropping one standardfrom 200C. The result must be within 61.5 % 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 ac
36、cordance with the sample testing procedure.The capsule shall be recalibrated 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
37、the weight to 0.1 %.9.2 Measure the mass of the calorimeter fluid in the 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 atle
38、ast once every five minutes until thermal equilibrium isachieved (Note 5). 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 th
39、e entire time that the sample temperature isequilibrating in the furnace, 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 reache
40、d thermal equilibrium,position the furnace over the Dewar (Note 6). Momentarilyremove 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 sha
41、ll be disregarded and re-peated.9.6 Continuously monitor the temperature 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
42、fluid and mass of the emptyDewar. The mass of the fluid is the difference 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 f
43、urnaces, the time that the furnace is over theDewar should be minimized.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 illustr
44、ated in Fig. 2. Calculate thetemperature change of the bath as follows:DTcal5 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
45、the calorimeter is equal to the sumof the enthalpy changes of the sample 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
46、 is performed, then the mean specificheat of the sample can be calculated 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 e
47、ach drop and plotas a function of drop temperature. The enthalpy change shouldbe zero at Tm. Use a curve fitting routine to fit the data andobtain a polynominal equation. Use DH =0atTmas one of thepoints.FIG. 2 Curve Showing Relation of Temperature to Time for aTypical Specific Heat DeterminationD 4
48、611 86 (2004)310.8 Calculate the instantaneous specific heat by differenti-ating the 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
49、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 shall contain the following information:11.1.1 Sample description including size, form, and mass.11.1.2 The enthalpy change and drop temperatures.11.1.3 The calculated mean or instantaneous, specific heat,or both.11.1
