Apparatus for use in carrying out a physical and/or chemical process, for example a heat exchanger

DETAILED DESCRIPTION The object of the present invention is to provide a simplification of apparatus such as that described above.
In addition it appears that the batch-wise return of the granules can give rise to an irregular operation of the process.
At least the granular mass may be present in the return tube to a variable extent and thus there will be a varying quantity in the lower tank or the upper tank respectively.
Although in some cases, the efficiency of the heat transfer through the tube wall to, or from, the liquid medium is adversely affected by circulation in the apparatus via the return tube, and this must then be avoided by means of a lock system, it has appeared that in other cases the efficiency of this heat transfer is hardly affected by a small circulation of the liquid medium via the return tube.
This is associated inter alia with the manner of heat transfer between the outer walls of the tubes and a second heat transfer medium flowing over them.
It is not necessary to go into the details of these phenomena since they belong to the general theory of heat transfer in heat exchangers.
The present invention consists in that the valve means controlling the return of the granular mass comprises a single valve with a valve member which is moveable with respect to the lower end of the return tube.
It appears that, with this valve in a partly open position, granules from the return tube can flow into the lower chamber but that a downward movement of the liquid medium does not necessarily occur at the same time, or at least only to a small extent.
The velocity of the liquid medium in the return tube will adjust in dependence on the density of the liquid medium and of the granular mass and also on the mode of operation of the apparatus, the ratio of the diameters of the riser tubes and the return tube and on the valve aperture.
This velocity may be variable from substantial to low in the downward direction, but it is also conceivable that it be zero, or even that there is a slight upward velocity in the return tube