ASTM D7863-17 Standard Guide for Evaluation of Convective Heat Transfer Coefficient of Liquids.pdf

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1、Designation: D7863 17Standard Guide forEvaluation of Convective Heat Transfer Coefficient ofLiquids1This standard is issued under the fixed designation D7863; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio

2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide covers general information, without specificlimits, for selecting methods for evaluating the heating andcooling perfor

3、mance of liquids used to transfer heat whereforced convection is the primary mode for heat transfer.Further, methods of comparison are presented to effectivelyand easily distinguish performance characteristics of the heattransfer fluids.1.2 The values stated in SI units are to be regarded asstandard

4、. 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-priate safety, health and environmental practices and deter-m

5、ine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendation

6、s issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D445 Test Method for Kinematic Viscosity of Transparentand Opaque Liquids (and Calculation of Dynamic Viscos-ity)D1298 Test Method for Density, Relative Density, or APIGravi

7、ty of Crude Petroleum and Liquid Petroleum Prod-ucts by Hydrometer MethodD2270 Practice for Calculating Viscosity Index from Kine-matic Viscosity at 40 C and 100 CD2717 Test Method for Thermal Conductivity of LiquidsD2766 Test Method for Specific Heat of Liquids and SolidsD2879 Test Method for Vapor

8、 Pressure-Temperature Rela-tionship and Initial Decomposition Temperature of Liq-uids by IsoteniscopeD2887 Test Method for Boiling Range Distribution of Pe-troleum Fractions by Gas ChromatographyD4052 Test Method for Density, Relative Density, and APIGravity of Liquids by Digital Density MeterD4530

9、Test Method for Determination of Carbon Residue(Micro Method)D6743 Test Method for Thermal Stability of Organic HeatTransfer FluidsD7042 Test Method for Dynamic Viscosity and Density ofLiquids by Stabinger Viscometer (and the Calculation ofKinematic Viscosity)E659 Test Method for Autoignition Temper

10、ature of Chemi-cals3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 heat transfer fluid, na fluid which remains essen-tially a liquid while transferring heat to or from an apparatus orprocess, although this guide does not preclude the evaluation ofa heat transfer fluid that may

11、 be used in its vapor state.3.1.1.1 DiscussionHeat transfer fluids may be hydrocar-bon or petroleum based such as polyglycols, esters, hydroge-nated terphenyls, alkylated aromatics, diphenyl-oxide/biphenylblends, and mixtures of di- and triaryl-ethers. Small percent-ages of functional components suc

12、h as antioxidants, anti-wearand anti-corrosion agents, TBN, acid scavengers, ordispersants, or a combination thereof, can be present.3.1.2 heat transfer coeffcient, na term, h, used to relatethe amount of heat transfer per unit area at a given temperaturedifference between two media and for purposes

13、 of this guide,the temperature difference is between a flow media and itssurrounding conduit.3.1.2.1 DiscussionThe heat transfer coefficient for condi-tions applicable to fluids flowing in circular conduits underturbulent flow is referred to as the convective heat transfercoefficient.1This guide is

14、under the jurisdiction of ASTM Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.L0.06 on Non-Lubricating Process Fluids.Current edition approved Aug. 1, 2017. Published August 2017. Originallyapproved in 2013. Last previous editio

15、n approved in 2013 as D7863 13. DOI:10.1520/D7863-17.2For 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 Summary page onthe ASTM website.*A Summa

16、ry of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established

17、in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14. Summary of Guide4.1 The convective heat transfer coefficient for flow in acircular conduit depends in a compl

18、icated way on manyvariables including fluid properties (thermal conductivity, k,fluid viscosity, , fluid density, , specific heat capacity, cp),system geometry, the flow velocity, the value of the character-istic temperature difference between the wall and bulk fluid,and surface temperature distribu

19、tion. It is because of thiscomplicated interaction of variables, test results can be biasedbecause of the inherent characteristics of the heat transferapparatus, measurement methods, and the working definitionfor the heat transfer coefficient. Direct measurement of theconvective heat flow in circula

20、r conduits is emphasized in thisguide.4.2 This guide provides information for assembling a heattransfer apparatus and stresses the importance of providingreporting information regarding the use and operation of theapparatus.5. Significance and Use5.1 The reported values of convective heat transfer c

21、oeffi-cients are somewhat dependent upon measurement techniqueand it is therefore the purpose of this guide to focus on methodsto provide accurate measures of heat transfer and precisemethods of reporting. The benefit of developing such a guide isto provide a well-understood basis by which heat tran

22、sferperformance of fluids may be accurately compared and re-ported.5.2 For comparison of heat transfer performance of heattransfer fluids, measurement methods and test apparatus shouldbe identical, but in reality heat transfer rigs show differencesfrom rig to rig. Therefore, methods discussed in the

23、 guide aregenerally restricted to the use of heated tubes that have walltemperatures higher than the bulk fluid temperature and withturbulent flow conditions.5.3 Similar test methods are found in the technicalliterature, however it is generally left to the user to reportresults in a format of their

24、choosing and therefore directcomparisons of results can be challenging.6. Test Apparatus and Supporting Equipment6.1 BackgroundConvective heat transfer may be free(buoyant) or forced. Forced convection is associated with theforced movement of the fluid and heat transfer of this type isemphasized her

25、ein. To greatly minimize to the buoyantcontribution, the Reynolds number should be sufficiently highto eliminate thermal stratification and provide a fully devel-oped turbulent velocity profile. The use of a vertical heatedsection also helps in this regard due to less likelihood offorming voids near

26、 the walls. To minimize the contribution ofradiation heat transfer, which is proportional to the fourthpower of temperature, high wall temperatures (350 C +)should be avoided. However, for those cases where high walltemperatures are present, corrections for the radiant heatcontribution are necessary

27、. Conduction (heat flow throughmaterials) will always be present to some extent and the designof any test apparatus must account for all conduction paths,some of which contribute to heat losses. Energy balance, thatis, accounting for all heat flows in and out of the system, isimportant for accurate

28、determination of heat transfer coeffi-cients.6.1.1 A conventional convective heat transfer apparatuspumps the fluid of interest through a heated tube where theamount of energy absorbed by the fluid from the hot wall ismeasured. By allowing the walls to be cooler that the fluid,then cooling transfer

29、coefficients could be derived, but fluidheating is the focus of this guide. The heat transfer coefficient,h (W/cm2C) may be derived through appropriate calculations.Two types of wall boundary conditions are generally em-ployed: a constant wall temperature or a constant heat fluxwhere heat is distrib

30、uted over a given area such as W/m2.Itisimportant to define the wall conditions because the temperaturedistributions in the axial flow direction, dT/dz, for the wall andbulk fluid differ depending on wall condition. Measurement ofthe wall temperature distribution may be used to verifyboundary condit

31、ions and to obtain estimates of experimentalerror.6.1.2 A reliable method for setting up a constant heat fluxcondition is to utilize resistive heating of the conduit (theconduit acts as a resistor when connected to the terminals of anelectrical power supply). One advantage of this method is therelat

32、ive ease for measuring the electrical power input (Watts)and inferring the wall temperature from the temperaturecoefficient of resistance () for the wall material. Constant walltemperature boundary conditions are established by surround-ing the heat transfer conduit with a medium at constanttemperat

33、ure (such as a thermal bath). A suggested setup for aconstant flux heat transfer apparatus is shown in Fig. 1.6.1.3 The apparatus shown in Fig. 1 exhibits a free surfaceat atmospheric pressure within the reservoir and therefore thesystem is open and non-pressurized. For fluids with low vaporpressure

34、, it may be necessary to run a closed and pressurizedsystem. Desired bulk fluid temperature and wall temperatureswill significantly impact the design and operation of the loop.Select seals within the pump to be compatible with the fluidand withstand the operating pressure and temperature. For theloo

35、p shown, a constant speed pump with external bypasscontrol is employed. Variable speed pumps with no bypass maybe used; however, a pump speed control unit will be necessary.The installation of a safety relief valve to prevent pressurebuildup is recommended.6.1.4 The electrically heated test section

36、is shown in avertical position. This arrangement generally prevents hotspots on the walls from forming mainly due to fluid voids orthe development of “convection cells” and stratified flows. Theelectrical resistance of a steel or copper tube will be quite low,and therefore extremely high electrical

37、currents are necessaryto produce the desired heat flux. For 0.5 in. diameter tubes ofa few feet in length, it is not uncommon to see currents in the1000 amp range. Employ large copper buss bars to carrycurrent to the heated tube. Accurate measurement of voltageand current will provide an accurate me

38、asure of power deliv-ered. Because of the presence of high currents, adequate safetysystems should be employed.D7863 1726.1.5 Due to the high electrical currents and potentiallyextremely high tube temperature, both electrical and thermalisolation are needed at each end of the heated section. Usecera

39、mics that can be machined to manufacture isolators ofdesired characteristics. Many ceramic materials can handle1500 F in an untreated condition, whereas simple heat treatingof these materials will allow for operation above 2500 F. Tofurther reduce heat losses, the heated tube will require substan-ti

40、al insulation. Ceramic blankets work very well, especially forhigh temperature applications.6.1.6 Document wall roughness of the heated section. Com-mercially drawn stainless steel tubing is preferred, but tubewall roughness shall approach hydraulically smooth conditionswith Darcy-Weisbach relative

41、roughness values approaching0.00001 or better.6.1.7 The heated test section shall be easily removed forinspection and for possibly changing tube sizes. It is especiallyadvantageous to accommodate sectioning of the tube upon thecompletion of a test sequence for the purpose of examiningdeposits on the

42、 tube wall via carbon burn off methods (TestMethod D4530) or Auger electron spectroscopy. The lattermethod is a widely used analytical technique for obtainingchemical composition of solid surfaces.36.1.8 Do not exceed temperature limitations set by pumpseals and other seals. For many installations,

43、this means thatextremely hot fluids going through the loop (and heatedsection) will need to be cooled before they enter the pump. Thiscooling will set up thermal cycling of the fluid by heating andcooling the fluid every time the fluid circulates through theloop.6.2 Required MeasurementsMeasure temp

44、erature (walland fluid) and flow rate to obtain sufficient information forcalculating the heat transfer coefficient. However, when com-paring test results to observations of others, it is necessary toobtain fluid property data and dimensions of the test sections.The reason, convective heat transfer

45、predictions are usuallycast in terms of non-dimensional groups of Nusselt number,Reynolds number, and Prandtl number. Other non-dimensionalgroups may also be applicable. Therefore values of fluidviscosity (Test Method D445 or D7042, Practice D2270),thermal conductivity (Test Method D2717), fluid den

46、sity (TestMethod D1298 or D4052), and heat capacity (Test MethodD2766) all as a function of temperature are necessary forvarious heat transfer correlations.6.2.1 Other properties of fluids are required for completedocumentation and safety of operation. These include boilingrange distributions (Test

47、Method D2887), vapor pressure-temperature relationship (Test Method D2879), and autoigni-tion temperature (Test Method E659).3Chourasia, A. R., and Chopra, D. R., Handbook of Instrumental Techniques forAnalytical Chemistry, Chapter 42, 1997.FIG. 1 Apparatus for Measuring the Convective Heat Transfer

48、 CoefficientD7863 1736.2.2 Suggested test section temperature measurements areshow in Fig. 2. This figure shows a constant heat flux boundarycondition. A constant wall temperature condition may also beimposed by surrounding the tube within an isothermal bath.6.2.3 The subscript “b” denotes a bulk fl

49、uid temperature(sometimes referred to as the bulk mixing cup temperature) andthe subscript “w” denotes a wall temperature. It is suggestedthat five or more wall temperatures be obtained over the testsection length. For a constant heat flux condition, dTw/dz isconstant and the value of Twincreases from inlet to outlet andin the case of a constant temperature wall, Twis a constant overthe entire length. These temperature distributions should bereported along with the test results to ensure reasonablecomparisons of results from other sources.6.2.4 If th