GB1360936A - Rotary heat exchangers - Google Patents

Abstract

1360936 Rotary heat exchangers E I DU PONT DE NEMOURS & CO 14 Sept 1972 [15 Sept 1971] 42701/72 Heading F4S A rotary heat exchanger unit comprises a plurality of annular, coaxial, spaced-apart fins 10 through which extend an annular array of tubes 11 in which flows a first fluid, whilst a second fluid flows spirally outwardly over the tubes between adjacent fins, the fin spacing being such as to convey and accelerate the flow of the second fluid, and means such as flanges 27, 28 being provided to increase the flow of the second fluid through the heat exchanger. Methods of determining the fin spacing and the projection of the flanges 27, 28 are described. The apparatus is said to be of general use for the heating or cooling of gases, liquids or vapours but in the form shown is adapted as an air cooled surface condenser. The tubes 10 communicate at one end with a hollow casing member 1 and are closed at their other end by a ring member 14. The flanges 27, 28 are formed respectively as radial extensions of the casing 1 and ring member 14. Vapour enters the tubes via a hollow shaft 5 and the casing 1, and condensate from the tubes flows back into the casing 1 where it is retained at the peripmeter by centrifugal action and discharges therefrom via tubes 90 into a sump having an outlet 95 and formed by a compartment 92 in a stationary plenum chamber housing the rotor. The tubes are canted to the horizontal axis of the rotor to facilitate the discharge of condensate from the tubes as shown in Fig. 9. The rotor is driven by a motor M through gears 8, 9. The cooling-air stream enters the plenum chamber via a bell-shaped member 21 and is directed over the tube assembly by a non-rotating distributer 34 movable axially along a fixed shaft 36 to vary the heat exchange area contacted by the air stream. Movement of the distributer is effected automatically by a control unit 70 in response to the temperature difference between the inflowing and outflowing air streams as detected by thermocouples 71, 72. Air flow from the heat exchanger is said to be augmented by the aforementioned flanges 27, 28 and may be further augmented under full-load conditions by pivoted blades 29, Fig. 2 (forming part of the rotor assembly) when these are in a radial position (shown in dotted lines, Fig. 2). Below full-load conditions the blades are maintained in a neutral position (shown in full lines, Fig. 2) in which they lie generally parallel to the spirally flowing air stream. Movement of the blades 29 to the full-load position is effected by a cam 80 on the distributer 34. The cam contacts rollers 81 mounted on the casing 1 at the end of push rods 82 which actuate the blades. The tubes 11 may be of copper or aluminium, the fins 10 being bonded thereto with intervening spacers 20. In Fig. 12, the tube has integrally formed internal fins 100 and a heat conducting insert 101 press-fitted into the tube. Alternatively, Fig. 16, an array of small tubes 104 may be bonded into the tube 10. A further tube form, Fig. 17, comprises a corrugated element 105 sandwiched between plate members 106, 107. In a further alternative the interior surfaces of the tubes may be coated with a porous (e.g. sintered) material.