1、BRITISH STANDARD BS1902-5.8: 1992 Methods of testing Refractory materials Part5: Refractory and thermal properties Section5.8 Determination of thermal conductivity (split column method) (method1902-508)BS1902-5.8:1992 This British Standard, having been prepared under the directionof the Refractory P
2、roducts Standards Policy Committee, was published underthe authority of the Standards Board and comesintoeffect on 15 July1992 BSI08-1999 The following BSI references relate to the work on this standard: Committee reference RPM/1 Draft for comment 89/37667 DC ISBN 0 580 20837 0 Committees responsibl
3、e for this British Standard The preparation of this British Standard was entrusted by the Refractory Products Standards Policy Committee (RPM/-) to Technical Committee RPM/1, upon which the following bodies were represented: British Ceramic Research Ltd. British Steel Industry Engineering Equipment
4、and Materials Users Association Refractories Association of Great Britain Refractory Contractors Association Society of Glass Technology Amendments issued since publication Amd. No. Date CommentsBS1902-5.8:1992 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope
5、 1 2 References 1 3 Designation 1 4 Definition 1 5 Principle 1 6 Apparatus 1 7 Preparation of test pieces 4 8 Procedure 4 9 Calculation of thermal conductivity 6 10 Test report 7 Annex A (informative) Chemical composition and thermal conductivity of suitable alloy steels 8 Figure 1 Schematic arrange
6、ment of apparatus 2 Figure 2 Typical arrangement for heater 3 Figure 3 Design of support and water cooling system 5 Figure 4 Arrangement of thermocouple junctions 5 Table A.1 Chemical composition of alloy steels 8 Table A.2 Thermal conductivity of alloy steels 8 List of references Inside back coverB
7、S1902-5.8:1992 ii BSI 08-1999 Foreword This Section of BS1902-5 has been prepared under the direction of the Refractory Products Standards Policy Committee. The method described in this Section is one of three methods for the determination of thermal conductivity included in BS1902-5 as follows: Sec
8、tion 5.5: Determination of thermal conductivity (panel/method) calorimeter method (method1902-505); Section 5.6: Determination of thermal conductivity (hot wire method) (method1902-506); Section 5.8: Determination of thermal conductivity (split column method) (method1902-508). NOTEThis Section is to
9、 be read in conjunction with BS1902-5.0 Introduction and BS1902-3.1 Guidance on sampling. Section5.0 sets out the general arrangement of BS1902 and lists the Sections of Part5. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are r
10、esponsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard has be
11、en updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS1902-5.8:1992 BSI 08-1999 1 1 Scope This Section of BS1902-5 describes the method for determining the thermal conductivity of shaped refractory products
12、, having oxidizable constituents, by a split column method. The method may also be used for non-oxidizable products. The method is principally intended for materials having a thermal conductivity in the range 3W/(mK) to80W/(mK) and for mean temperatures (test piece) in the range300 C to850 C. The me
13、thod is not applicable to materials with constituents which are volatile at temperatures within the range of the test. NOTEThe best accuracy is attained when the thermal conductivity of the test piece is close to that of the alloy steel blocks (see6.2). 2 References 2.1 Normative references This Sec
14、tion of BS1902 incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or revisions of, any of these publication
15、s apply to this Section of BS1902 only when incorporated in it by updating or revision. 2.2 Informative references This Section of BS1902 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the
16、inside back cover, but reference should be made to the latest editions. 3 Designation The method of determining thermal conductivity by the split column method described in this Section is referred to by the designation: Method1902-508 4 Definition For the purposes of this Section of BS1902, the fol
17、lowing definition applies. thermal conductivity (coefficient of thermal conductivity) symbol2, unitW/(mK) the rate of linear heat flow, under steady state temperature conditions, through unit area of a test piece, per unit temperature gradient, in a direction perpendicular to the area 5 Principle Th
18、e quantity of heat flowing through a test piece, immersed in a non-oxidizing atmosphere and located between two alloy steel blocks of known thermal conductivity, is determined by measurement of temperature gradients. 6 Apparatus 6.1 Thermal conductivity apparatus, with an arrangement for inducing he
19、at flow through a test piece as shown in Figure 1. A mild steel cylindrical columnmm in diameter and200mm 2mm in length, with a ground flat smooth finish top surface perpendicular to the major axis, is supported vertically on a mild steel rigid base plate. The base of the column is recessed and fitt
20、ed with inlet and outlet ports for continuous water flow. The column is enclosed by insulating firebrick in the form of a sectioned annular ring of at least280mm in height and130mm in thickness. The firebrick shall be of grade125in accordance with BS7225-1.1:1989 and shall be held in close contact w
21、ith the column by external strapping or equivalent means. The insulation shall extend for76mm above the column and shall be recessed for25mm over this height, as shown in Figure 1. A portable radiant heater assembly, composed of four or five silicon carbide heaters (or equivalent elements), shown in
22、 Figure 2, is supported centrally on the insulating firebrick. The whole arrangement is enclosed by a removable airtight steel cover which can be bolted to the base plate using a vacuum proof seal, e.g.0-ring seal. The steel cover shall be made from a grade and gauge of steel sufficient to withstand
23、 a reduced interior pressure of less than2500Pa. Connections for the inlet/outlet ports for cooling water and gas, and entry for thermocouples and electric supply to the heater shall be built into the base plate with airtight seals. The evacuation port shall be either built into the base plate or be
24、 located in the steel cover. A test piece, in the form of a cylinder, is located between two cylindrical alloy steel blocks of known thermal conductivity and the assembly is placed centrally on the mild steel column. The recess between the test piece and alloy steel blocks assembly and the insulatin
25、g firebrick is packed with graded vermiculite. 50 +1 0BS1902-5.8:1992 2 BSI 08-1999 6.2 Steel blocks, of known thermal conductivity. Two alloy steel cylindrical blocks are machined tomm diameter and25mm 0.5mm thickness. The end faces shall be ground to a flat, smooth finish, shall be parallel to0.05
26、mm (measured at the extremities of any two vertically separated diameters) and shall be perpendicular to the cylindrical axis. Two holes to accommodate thermocouples(6.4) of either1mm or1.5mm nominal diameter, with minimum clearance, are drilled in each block. The holes are drilled radially to a dep
27、th of25mm with a vertical separation of18mm to20mm. The exact distance between the blind ends of each pair of holes shall be determined in accordance with8.1. The alloy steel shall be of a composition compatible with the highest temperature at which tests will be carried out and for which thermal co
28、nductivity reference data is available (see2.2). NOTETwo alloy steels which are suitable are Macloy G and Incalloy DS, for which the chemical composition and thermal conductivity values are given in Annex A. Macloy G is no longer available but is in use in existing apparatus. For information on the
29、availability of Incalloy DS, write to Customer Information, BSI, Linford Wood, Milton Keynes MK146LE. Alternatively, alloy steels of grade NA17 in accordance with BS3076 are suitable if the relevant data are known. The maximum temperature of use for all these steels is1000 C. Figure 1 Schematic arra
30、ngement of apparatus 50 +0.5 0BS1902-5.8:1992 BSI 08-1999 3 6.3 Temperature controller, with a control thermocouple capable of controlling the heating of the upper alloy steel face of the test piece assembly to the test temperature 2K. The control thermocouple shall be either platinum/platinum13%rho
31、dium (type R in accordance with BS4937-2:1973) or a base metal thermocouple, the latter being restricted to use at temperatures below1000 C. 6.4 Thermocouples, which shall be mineral-insulated and metal-sheathed and suitable for temperature measurement up to1100 C. Six such thermocouples shall be us
32、ed for measuring temperatures of the test piece and alloy steel blocks. The length of the thermocouples shall be sufficient to traverse from the test piece assembly to connections external to the closed thermal conductivity apparatus and the thermocouples shall be either1mm or1.5mm in nominal diamet
33、er. NOTE 1A sheathed nickel-chromium/nickel-aluminium thermocouple is suitable. NOTE 2It is essential that thermocouples of the same type and nominal diameter are used throughout the assembly. Figure 2 Typical arrangement for heaterBS1902-5.8:1992 4 BSI 08-1999 6.5 Temperature recorder, being either
34、 a temperature or millivolt measuring instrument for measurement of test piece and alloy steel block temperature, via thermocouples(6.4), to an accuracy of 0.3K. 6.6 Vacuum pump, first stage, and with a gauge capable of reducing the pressure inside the closed airtight apparatus to not more than2500P
35、a. 6.7 Water supply, for cooling the base of the mild steel column, delivered from a constant head tank, capable of maintaining a supply of at least5l/h with a temperature variation of 2K. See Figure 3. 6.8 Graded exfoliated vermiculite of size2.0mm,+0.5mm, for packing the recess between the test pi
36、ece assembly and the insulating firebrick (see6.1). NOTECertain qualities of vermiculite may shrink during the test. This can be avoided by using material which has been calcined for5h at1100 C. 6.9 A supply of argon or nitrogen gas and flow gauge (see8.5). 6.10 Vernier callipers, in accordance with
37、 BS887:1982. 6.11 Travelling microscope, to read to0.05mm. 6.12 Desiccator 6.13 Engineers surface plate 7 Preparation of test pieces NOTE 1Many materials are anisotropic and it is important in determining thermal conductivity that the direction of heat flow in relation to the sample shape is known.
38、NOTE 2Where possible, the direction in which a test piece is taken from a sample should be agreed between the test house and its customer. 7.1 The test piece shall be a cylinder measuringmm and of25mm 0.5mm thickness. The direction in which a test piece is taken from a sample shall be stated in the
39、test report. The end faces shall be ground to a flat, smooth finish (preferably with a cup-grinder), and shall be parallel and perpendicular to the cylindrical axis. Parallelism shall be checked by measuring the thickness of the test piece at four positions using vernier calipers(6.10). The differen
40、ce between any two measurements shall not exceed0.2mm. To ensure that the end faces of the test piece are flat over their entire area, each face shall in turn be pressed on to an engineers surface plate(6.13) which is lined with carbon paper and hardened filter paper0.15mm thick. Test pieces which d
41、o not show two complete, clearly visible carbon impressions shall be reground. NOTEFor coarse-textured materials which are difficult to prepare as described in7.1, it is permissible to use a thin film of high-purity, smooth-consistency carbon or Carborundum paste to mate the surfaces of the test pie
42、ce and the alloy steel blocks. The carbon paste should be chemically compatible with the test material at the temperature of the test. 7.2 Two holes, either1mm or1.5mm in diameter to house thermocouples(6.4), shall be drilled in the test piece radially to a depth of25mm and at a separation of18mm to
43、19mm in line with the cylindrical axis of the test piece. The exact distance between the junctions of the two thermocouples when housed in these holes shall be obtained as described in8.1. 8 Procedure 8.1 Insert two straight pins of near equal length and either1mm or1.5mm in diameter into the holes
44、drilled in the test piece (seenote). Measure and record the length of the pins and the length projecting from the test piece to0.01mm. Measure and record the separation of the centre line of the pins at their extreme ends and at the points they project from the test piece surface, using the travelli
45、ng microscope(6.11) to0.05mm. Remove the pins. Calculate the distance between thermocouple junctions d r(inmm), shown (in exaggerated form) in Figure 4, as follows: NOTETwo drill bits used to drill the holes are suitable for this purpose. 8.2 Measure the diameter of the test piece, at two positions
46、at right angles, to0.1mm and record the mean. Dry the test piece at110 C to constant mass, cool and place in a desiccator(6.12) until used. 50 +0 0.5 where a is the length of the pins (inmm); b is the projecting length of the pins (inmm); d 1is the separation of the extreme pin ends (inmm); d 2is th
47、e separation of the pins where they project from the test piece surface (inmm).BS1902-5.8:1992 BSI 08-1999 5 Figure 3 Design of support and water cooling system NOTESee clause8. Figure 4 Arrangement of thermocouple junctionsBS1902-5.8:1992 6 BSI 08-1999 8.3 Place the test piece between the two alloy
48、 steel blocks(6.2) and position this assembly centrally on the mild steel column. Insert the six metal-sheathed thermocouples(6.4) into the radial holes in the test piece and steel blocks and uniformly pack graded vermiculite(6.8) into the recess between the test piece assembly and the surrounding i
49、nsulation. Ensure that the vermiculite is level with the uppermost surface of the top steel block. Throughout the placing of the thermocouples and vermiculite ensure that the test piece and steel blocks are held firmly in position on the mild steel column and that the positions of thermocouple junctions are maintained. 8.4 Place the control thermocouple(6.3) so that its junction is at the centre of the upper steel surface. Place the radiant heater in position and ensure the working of all connections to the thermocouples, heat
