INDUSTRIAL AND ENGINEERING CHEMISTRY
824
struction to be sufficiently simple to be performed in the average machine shop at moderate cost. The method which was finally rvorked out apparently satisfies these conditions. Details of the installation appear in Figure 1, which shows only the tube and the method of installing the thermocouple junctions in the tube wall. This tube could be that of a single-tube test
l-ineh, ekraheavy copper pipe. A slot is milled in the outside v d l of the tube, parallel to the longitudinal axis, from the point at which the junction is t o be installed to a point where the leads may be brought out,without influencing the transfer of heat or the flaw of flmds. Thls operation is easily performed in a well-equipped machine shop. The junction is installed in a 0.062-inch hole drilled 0.25-inch into the tube wall at an angle from the slot. The junction is inserted in this hole and soldered in place. The leads am enclosed in a small brass tube and laid in the slat. The brass tube is bent slightly at the end and butted against the wall of the slot, in such a. way that it completely covers the leads. The slot is then filled in with solder and is polished down t o the original contour of the tube. The size of the slot depends on the size of the brass tubing necessary t o enclose the leads. For a pair of No. 24 enameled, silkcovered wires, a brass tube 0.093 inch in outside diameter and 0.071 inch in inside diameter will be found satisfactory. This tube will fit nicely in a milled slot about 0.10 inch wide and 0.10 inch deep. By making the slot wider, two or three sets of leads may be brought out from each end of the tube, and if more
Vol. 13, No. 11
than four to six couple installations are desired in one tube wall, the number of slots may be increased. This method of installation may be used to locate a thermocouple junction a t any point in the wall of the tube and the leads may be carried to any desired point through a substantially isothermal zone. The possibility exists that the solder, having surface characteristics different from those of the tube metal, might influence the flow of condensate over the surface of the tube. This effect could be eliminated by plating the surface of the tube after the thermocouple installation. If the heat flux is high, a correction should be made for the temperature drop between the tube surface and the point of junction installation. This can easily be done when the heat flux and the thermal conductivity of the tube metal are known.
Literature Cited I(1) l l Akin, Akin. G. A,. H..Trans. Am. Inst. Chem. A,, snd and McAdams. W. H., C h m . Enm.. Engr.. " . . ~ I ~~~
35, i37-55 35, 137-55 (1939). (2) Baker. E. M., and Mueller. (2) Mueller. A. C.. IND. ENG.CHEM.,29, 106& 72 (1937); Trans. Anz.Inst. AmInst. Chem. Engr.. 33,539-58 (1937). (3) Colburn and Hougen, IND.ENO.CHEM.,22.522 (1930). 14) MoAdzms. "Heat Transmission". New York. MoGraw-Hill Book Co., 1933. (5) Reiher, H., Mitt. Forschungsarbdtungm, No.269 (1925). (6) Rietschel, Mttt. Pw2fungsanstolt Hdaungs LOftungsdnrichtu?wm, RBnigl. Tech. Hochsehule Berlin. 3 (1910).
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alkaline solutions presents a special problem in apparatus assembly. Where the liquids involved are not particularly corrosive Johnson and Miller (1) suggest the use of centrifuge cups and receivers machined from Lucite. The present description involves au improvement, since standard parts are involved and possible interaction of equipment and reagents is eliminated. The apparatus is shown in Figure 1, mounted on an Interns* tionrtl centrifuge siae 2 (International Equipment Company, 352
am mtn ruooer cusnron inserc no. OXL ana Dome no. am, cub into two parts and the top discarded. The special centrifuge onps were made by the Coon Porcelain Co. The centrifuge cups are 8.57 om. (3.375 inches) tall with an outside diameter at the base of 4.13 om. (1.625 inches) and at the top of 6.72 cm. (225 rnrhes). The imide dimnletcr at the to ill 64 CUI. (2.125 inches) and the upper flange is 1.75 rm. ( I l l 6 inch) a,idr and id offtict 0.32 cm. (0.125 inehl t o orowdc a shoulder SUEnortontopofthetrunnion&p. Thei6nsidideptbis8.26cm. (3.25 Cnches) a i d the capacity is f70 mL The cups are glazed inside and outside except for the bottoms. There are 190 t o 200 er forations in the bottom, all less than 0.05 em. (0.02 inchy i, diameter. A second o5set 3.33 em. (Is/rs inches) from the t O D is 0.16 em. (I/>e inch) in depth. The lids, are standard dize Coors No. 4 crucible lid. The cup and hd weigh 177 grams (6.25 ounces). The Hter flask assembly in the background is for use in removing excess mother liquor by reduced pressure filtration. The filkrflnskis:oful0Bml:capn&y provided aitlia l O . l t ~ - ~ (4-inch) u. (i0" funnel. The ~ u p p ~for m LIE ccntriiugc cup is nude aecordmr I O rhr directions oi Smith and Gina I?) from a So. 14 rubber turyed inside out. The assembly as described will provide for 0.45 kg. (1 pound) of crystals of average density and the equipment can be whirled at 2000 r. D. m. sumorted in trunnion No. 236 without daneer of prriwutini the fl
