GB868611A - Improvements in or relating to heat exchangers of the drier roll type - Google Patents

Abstract

868,611. Hollow rollers. HOT OIL HEATER CO. Ltd. Nov. 3, 1958 [Nov. 4, 1957], No. 35220/58. Class 34(1) A heat exchanger comprises an outer drying roll 1, Fig. 2, with ends closed by heads 2, 3 mounted on hollow journals 10, 11, an internal cylinder 14 with ends closed by heads 26, 27 and located concentrically within and annularly spaced from roll 1, and a hollow tubular shaft 15 is-for fixedly mounting the cylinder 14, the shaft having ends which extend through heads 2, 3 for supporting the roll 1 for rotation about the cylinder 14. A heat transfer medium to heat or cool the roll 1 is led through the shaft 15 and passes through tubes 33, Fig. 4, extending to the exterior of cylinder 14 and is distributed in a circumferential path through the annular space between the inner and outer cylinders, from which space it is led through tubes 34 attached to a return manifold 32 which is welded along one side of and parallel to the axis of the shaft 15. A barrier 39 mounted on the outside of the cylinder 14 reduces the clear. ance at 40 between the roll 1 and cylinder 14 through an area between the entering and leaving heat transfer medium sufficient to increase the resistance between the two to force substantially all the medium to flow circumferentially in one direction around the cylinder 14 before exiting. The roll 1 is driven through driver gear 50 so that the medium is moved by the sheer stresses created by the movement of the internal surface of the roll 1, the resistance to sheer of the medium creating a drag effect and at sufficiently high speed a pumping action may be established within the heat exchanger. In a modification the cylinder 14, Fig. 17, is supported on the shaft 15 by dished or flanged heads 42 and clearance plates 44, 45 on the ends of the cylinder establish an optimum clearance between the plates and the roll heads 2, 3 to minimize the pumping effect and to reduce the energy required to drive the roll 1. Bearings 109<SP>1</SP>, 111<SP>1</SP> for the roll 1 may be mounted on the outside of the roll journals 10, 11 and spacing or alignment bearing 109, 111 mounted between the insides of the journals and the shaft 15. Circumferential guides 51, 52 on the cylinder 14 restrict the area of the medium to zones and so restrict the heating area of the roll 1. The flow of the medium in the supply or return pipes 33, 34 may be controlled by manually-controlled valves of a needle or butterfly-type. Figs. 20, 21 (not shown) to establish a uniform heat throughout the surface of the roll 1. In another modification the cylinder 14, Fig. 24, has a two-compartment header 73 connected to supply pipes 67, 68, 69 and return pipes 70, 71, 72 supplied from a shaft 66 having a plug 65. The header is divided at 75, having a clearance 40 to allow the medium to flow circumferentially around the space between the roll 1 and cylinder 14 and the volume and velocity of flow may be set by the size of clearances formed between the sides of the header and the roll 1. The medium may enter and leave on the same side of the drier by inserting a tube within the shaft 66 from the inlet end and passing the pipe through the plug 65 into the outlet end of the shaft as in Fig. 26 (not shown). In a further form a single. header for the supply pipes 67, Fig. 31A (not shown) may be provided, the shaft 15 and cylinder 14 having apertures 79, 36 for the return of the medium. The supply and return pipes may be replaced by flat unsymmetrical funnel-shaped structures 92, 93, Fig. 35 (not shown) which terminate in supply slots in the surface of the cylinder 14 and in slots in the surface of the shaft 15. Stuffing boxes to contain the medium within the heat exchanger comprise the inside surface of the journals 10, 11 of the roll 1, the outside surface of extensions 101, Fig. 44, of the shaft 15, a resilient packing 20, 21 and a retainer assembly comprising packing rings 22, 23, rings 28, 29, loading springs 30, 31 and confining sleeves 24, 25 which together with a gland (not shown) hold the retainer assembly against the face of the journals 10, 11 while allowing a limited displacement of the cylinder 14 with respect to the roll 1. Greater displacement of the shaft extension 101, Fig. 46, with respect to the axis of the roll 1 which revolves about its own axis is allowed in a further form of stuffing box wherein deflection seal rings 105 contain resilient packing rings 20<SP>1</SP> within a desired area of the stuffing box when displacements occur and allow the rings to be displaced within an area bounded by a shoulder 104 on the extension 101, the journal 10 and the packing gland 103 and shaft deflections to be taken up in clearances 107<SP>1</SP>, 108' at opposite ends of the journal 10. Suitable heat transfer media mentioned in the Specification include inert gases; products of combustion, saturated vapours; superheated vapours; salts such as some of the sodium compounds; liquids such as water; mineral oil, synthetic substances, petroleum derivatives; coal derivatives; metals such as mercury and sodium; and' liquids operating under pressure sufficient to suppress vaporization.