Improvements in or relating to heat exchange devices

摘要

In a heat-exchanger (see Group XIII) for use in crystallizing, at least two hollow screw conveyer flights are mounted on rotatable shafts 55 in a casing which has a material inlet at or near one end and an outlet at or near the other, each flight being formed by a leading plate 41 and a trailing plate 43 connected together at or near their outer edges and connected at their inner edges to the shaft at a distance apart equal to 25-40 per cent of the pitch or of the average pitch if it varies, the flights overlapping to a distance at least 65 per cent of the height of each flight from shaft to outer edge. Figures are given for the relative dimensions of the flights and of their spatial relationship. The leading plate 41 is set at 85-95 degrees to the axis of the shaft 55. A fluid such as steam, water, ammonia, dichlorodifluoromethane, diphenyl oxide or oil passes through the hollow flights and the shafts may also be hollow for the flow of this fluid, Fig. 6. The treated material is moved through the casing as indicated by arrows in Fig. 5, and may be material to be crystallized or lubricating oil from which wax is to be extracted. In a double device the material passes from an upper to a lower casing to be returned to an outlet below the first inlet. The treating fluid may be introduced through openings 152, Fig. 6, in a disc which supports a duct 146 in the hollow shaft 55 and then flows into and through the flight to return through the shaft to discharge through the duct. The treated material passes in the direction of the arrow 153. Either or both of the flows of material and fluid may be reversed. If there are two flighted shafts side-by-side they are of opposite hands and rotated in opposite directions. There may be more than two shafts. One shaft may be mounted above another with the flights of the same hand and rotated in the same direction, the axes being in a vertical or inclined plane. A pair of shafts need not be parallel but may converge or diverge in the direction of material flow. The pitch of the flights may decrease towards the outlet. Flat faces 41 of the flight may work against curved faces 43 as in Fig. 5 but like faces may work against one another. The shafts, in section, are square, hexagonal or round. Alternative flight sections are indicated in Figs. 14, 15.