DIN 53019-3-2008 Viscometry - Measurement of viscosities and flow curves by means of rotational viscometers - Part 3 Errors of measurement and corrections《粘度测定法 用旋转粘度计测量粘度和流量曲线 第3部.pdf

《DIN 53019-3-2008 Viscometry - Measurement of viscosities and flow curves by means of rotational viscometers - Part 3 Errors of measurement and corrections《粘度测定法 用旋转粘度计测量粘度和流量曲线 第3部.pdf》由会员分享，可在线阅读，更多相关《DIN 53019-3-2008 Viscometry - Measurement of viscosities and flow curves by means of rotational viscometers - Part 3 Errors of measurement and corrections《粘度测定法 用旋转粘度计测量粘度和流量曲线 第3部.pdf（22页珍藏版）》请在麦多课文档分享上搜索。

1、September 2008DEUTSCHE NORM Normenausschuss Materialprfung (NMP) im DINDIN-SprachendienstEnglish price group 12No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of

2、 sale for German Standards (DIN-Normen).ICS 17.060!$X$“1530101www.din.deDDIN 53019-3Viscometry Measurement of viscosities and flow curves by means of rotationalviscometers Part 3: Measurement errors and correctionsEnglish translation of DIN 53019-3:2008-09Viskosimetrie Messung von Viskositten und Fl

3、iekurven mit Rotationsviskosimetern Teil 3: Messabweichungen und KorrektionenEnglische bersetzung von DIN 53019-3:2008-09Viscosit Mesurage des viscosits et des courbes dcoulement par des viscosimtres rotation Partie 3: Erreurs de la mesure et correctionsTraduction anglaise de DIN 53019-3:2008-09Supe

4、rsedesDIN 53018-2:1976-03www.beuth.deDocument comprises pages2202.10 DIN 53019-3:2008-09 A comma is used as the decimal marker. Contents Page Foreword3 1 Scope 3 2 Normative references4 3 Terms and definitions .4 4 Symbols and units.4 5 System-independent errors5 6 Measurement errors when using cyli

5、nder systems.9 7 Cone-and-plate system errors16 8 Parallel-plate system errors .18 9 Other application-dependent errors 18 Annex A (informative) Calculation of frictional heat effects in the measurement gap of cylindrical systems 19 Bibliography 22 2 DIN 53019-3:2008-09 Foreword This standard has be

6、en prepared by Working Committee NA 062-08-31 AA Viskosimetrie of the Normenausschuss Materialprfung (Materials Testing Standards Committee). DIN 53019, Viscometry Measurement of viscosities and flow curves by means of rotational viscometers comprises: Part 1: Principles and geometry of measuring sy

7、stem Part 2: Viscometer calibration and determination of the uncertainty of measurement Part 3: Measurement errors and corrections Amendments This standard differs from DIN 53018-2:1976-03 as follows: a) The number of the standard has changed. b) The title has been changed. c) The scope has been exp

8、anded to cover all types of rotational viscometers. Previous editions DIN 53018-2: 1976-03 1 Scope This standard specifies procedures for taking account of systematic errors in rotational viscometers due to the properties of the fluid, the specific nature of the flow process, the design of the appar

9、atus and the experimental procedure. It is assumed that there is a stationary flow zone between the boundary surfaces rotating with constant angular velocity. The following are outside the scope of the standard. a) Effects due to switching the viscometer on and off and rotational oscillations. b) Th

10、e superimposing of other basic flows on that due to rotation. c) Errors in simple time, rotational speed and torque measurements (see DIN 53019-2). d) Temperature or shear-stress ramps. The standard sets out how appropriate corrections can be made for systematic errors if the influencing variables c

11、an be quantitatively measured. In the case of errors that cannot be corrected, guidance is given on how to avoid them and on how to estimate them in order to include them in an uncertainty calculation. 3 DIN 53019-3:2008-09 2 Normative references The following referenced documents are indispensable

12、for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the document (including any amendments) applies. DIN 1319-1, Basic concepts in metrology General concepts DIN 1342-1, Viscosity Part 1: Rheological concepts DIN 1

13、342-2, Viscosity Part 2: Newtonian liquids DIN 53017, Viscometry Determination of the temperature coefficient of the viscosity of liquids DIN 53019-1:2008, Viscometry Measurement of viscosities and flow curves by means of rotational viscometers Part 1: Principles and flow zone geometry DIN 53019-2:2

14、001, Viscometry Determination of viscosity and flow curves with rotational viscometers Part 2: Viscometer calibration and determination of uncertainty of measurement 3 Terms and definitions For the purpose of this standard, the terms and definitions given in DIN 1319-1, DIN 1342-1, DIN 1342-2, DIN 5

15、3019-1 and DIN 53019-2 apply. 4 Symbols and units The symbols and units defined in DIN 53019-1 and in Table 1 are used in this standard. Symbol Meaning SI Unit Other units commonly used UTemperature coefficient of dynamic viscosity K1C1, bDynamic viscosity, dynamic viscosity measured without includi

16、ng the effect of frictional heat Pas mPas T, Ta, Ti, T0, Tb Measurement temperaturea, reference temperature K C T Increase in temperature due to frictional heat K C T Time s , , i, aAngular velocityarad/s i, critCritical angular velocityarad/s M, MZTorque, frictional component of torque Nm mNm MaMea

17、sured torque Nm mNm LCoefficient of linear expansion K1 4 DIN 53019-3:2008-09 Table 1 (continued) Symbol Meaning SI Unit Other units commonly used Radius ratio in cylindrical systems K Flow zone coefficient m3mm3cLDrag coefficient for end-face correction LEnd-face correction expressed as length corr

18、ection for inner cylinder m mm Ra, RiRadiusam mm L, L1, L2Length of cylindrical portion of inner cylinder in cylindrical measurement systems m mm La, LeffEffective length of outer cylinder in Mooney-Ewart measurement systems and in cylindrical systems with protective rings, respectivelyam mm LsDista

19、nce between inside end face of outer cylinder and inner cylinder m mm L Distance between cylindrical part of inner cylinder and base in standard cylinder system geometry m mm L“ Length of inner cylinder spindle immersed in fluid m mm ()ijEc Drag coefficient for eccentric cylinder positions Density k

20、g/m3g/cm3cWDrag coefficient of frictional heat Thermal conductivity W/mK oTaper angle of inner cylinder in Mooney-Ewart systems rad Taper angle of inner cylinder in standard geometry rad Eccentricity E Axial separation for eccentric cylinder positions m mm ain cylindrical systems, i and a denote the

21、 inner and outer cylinders, respectively. 5 System-independent errors 5.1 Effects of temperature errors The temperature of the measurement system and the sample shall be allowed sufficient time to stabilize prior to measurement. Errors in viscosity measurements due to insufficient temperature stabil

22、ization and/or inaccurate temperature measurement or deviations from constant temperature are often large because the viscosity of most fluids is often very temperature dependent. 5 DIN 53019-3:2008-09 The temperature coefficient, U, of the dynamic viscosity, , of a fluid, given by TUdd1 =(1) (see D

23、IN 53017), is generally the greater, the greater the viscosity of the fluid. It may be necessary to determine U and the measurement temperature for every fluid tested. See DIN 53019-2 for the procedure for calibrating the temperature-measuring device. 5.2 Experimental determination of effect of fric

24、tional heat in measurement gap The frictional heat has the following effects: a) The ratio of the torque and angular velocity, M/, decreases to a constant final value during the measurement. b) The final value of M/ obtained under a) decreases as the angular velocity increases. The phenomena describ

25、ed in a) and b) can also occur in thixotropic and pseudoplastic fluids, respectively, and may be mistaken for a frictional heat effect. The cause is more probably frictional heating if an increase in temperature is experimentally detected in the measurement gap and if the methods of estimation descr

26、ibed here and in the subsequent clause give similar results. If the viscometer has a short response time, a plot of the decrease in M/ against time as under a) extrapolated to the measurement start time shall be used to determine the frictional heating experimentally (see Figure 1). Key Curve 1: Mar

27、ked frictional heating with curve extrapolated to t0Curve 2: Insignificant frictional heating Figure 1 Effect of frictional heating as a function of time, t t0, after switching on In the case of shear stresses in which the change in temperature in the measurement gap due to frictional heating is neg

28、ligible, a horizontal curve will be obtained (curve 2 in Figure 1). This graphical extrapolation method sometimes makes it possible to extend the shear stress measurement range by as much as a factor of five compared with cases in which the frictional heat is insufficient to result in a decrease in

29、the final value. Beyond this point, the uncertainty of this method increases markedly. 6 DIN 53019-3:2008-09 5.3 Thermal expansion effects Thermal expansion may affect the measurement result if the temperature at which the measurement system has been calibrated and the measurement temperature are di

30、fferent and if the sample has been introduced at a temperature different from the measurement temperature. The effect of thermal expansion on the dimensions of the measurement system can be allowed for by multiplying the relevant dimensions by L(T T0) where T is the measurement temperature; T0is the

31、 reference temperature at which the dimension is determined; Lis the coefficient of linear expansion of the material of which the measurement system is made. The thermal expansion of the test fluid is generally greater than that of the measurement system, resulting in an excess of fluid at higher te

32、mperatures, which generally results in an increase in the torque measured. This problem can be overcome by design features such as an overflow or by suitably modifying the measurement procedure. 5.4 Component of torque due to internal friction in viscometer The torque measured may include, in additi

33、on to the torque, M, due to viscosity of the test fluid in the measurement gap, a component, Mz, due to bearing friction. If they are unavoidable as a result of design limitations, components such as air friction in air bearings shall be allowed for in the measured value of torque as far as is possi

34、ble in the present state of metrological science. Any component of torque detected in the calibrated torque measurement range that exceeds the uncertainty of measurement shall be regarded as a viscometer fault. Such components may be independent of or proportional to the rotational speed. Ways of de

35、tecting such components are listed in Table 2. 7 DIN 53019-3:2008-09 Table 2 Correction for internal viscometer friction No. Component and effect Cause Correction Determination a) By a blank test if viscometer design is suitable lim Ma= MZ= 0 0 0 1 0: internal friction component that is independent

36、of speed of rotation and resembles yield point Bearing (or dirty air bearing) b) Measurement of a Newtonian fluid at not less than three angular velocities (possibly also without a sample) Graphical extrapolation to 0 +=dda0aMM 2 1: internal friction component that is proportional to rotational spee

37、d Bearings, air friction, eddy current brakes Determination of viscosity using not less than three Newtonian fluids at not less than three angular velocities in each case Step 1: Graphical determination of 0and dMa/d for each fluid as described under No. 1b) Step 2: graphical extrapolation to 0kM +=

38、1add8 DIN 53019-3:2008-09 6 Measurement errors when using cylinder systems 6.1 General The effects due to many of the factors listed below are more readily seen or avoided if the gap width is fairly narrow and for that reason, the radius ratio (= Ra/Ri) should not exceed 1,1 and the length, L, of th

39、e inner cylinder should be not less than 1,5 Ri. The above value of should only be exceeded in special cases; the corrections specified below are then no longer valid above it. 6.2 End-face effect The effect of the finite length of the cylinder and of the end faces on the relationship between torque

40、 and angular velocity for laminar flow in the fluid is made up of the following components: a) A different type of flow zone builds up between the end faces of the inner and outer cylinders and makes a separate contribution to the torque measured. This contribution always results in a torque that is

41、 greater than that due to the flow zone in the measurement gap alone. b) The torque components due to the flow zone in the measurement gap and the zone at the end faces are generally not additive, unless the radial variation in the angular velocity is the same for the two undisturbed zones at their

42、point of contact. The end-face effect is best described by an imaginary length of cylinder L that takes account of the two effects described above under a) and b). ()L2i2a2i2a4ckLLRRRRM =+=(2) where LLc+=1L(3) This contribution can be calculated by choosing a suitable design and arrangement of the e

43、nd faces. The interface between the end-face and measurement-gap zones is particularly important and shall be such that the above contribution is negligible or its approximate value can be calculated (see entries Nos. 4, 5 and 6 in Table 3). Guide values for the contribution of a pair of end faces o

44、f the type shown in entry No. 4 in Table 3 are listed for Newtonian fluids in Table 4. 9 DIN 53019-3:2008-09 Table 3 End-face contribution to torque in cylindrical rotational viscometers No. Longitudinal section Description Correction for end-face effects 1 Cylindrical system (mostly of the Couette

45、type) with guard rings at which the torque is measured. The end-face components act on the guard rings. Leff= L + L L is taken as the sum of half the axial distances between the guard rings and the associated cylinder. 2 Cylindrical system with air cushion under the lower end face of the inner cylin

46、der at which the torque is measured. There is an overflow at the upper end of the cylinder Virtually no end-face components at the top. The effects at the lower end face are small provided that LS 3 (Ra Ri) 3 Two cylindrical systems having different lengths L1and L2, but otherwise identical dimensio

47、ns and distances, for comparing torques at a single value of viscosity with the angular velocity unchanged. ()LLRM +=1222i114 ()LLRM +=2222i214 211221MMMLMLL= 10 DIN 53019-3:2008-09 Table 3 (continued) No. Longitudinal section Description Correction for end-face effects 4 Cylindrical system with pla

48、ne-parallel end faces. Limit value for vanishingly small measurement gap and very large separation LSbetween the end faces of the inner and outer cylinders. (Roscoe) 1 ()=422,11ln351limiS1RLL5 Cylindrical system having concentric hemispherical end faces having the same values of the radii Raand Rias in the cylindrical sectio