Heat exchangers

Claim 1

An evaporator which comprises a rotatable casing for evaporating a liquid solution requiring concentration, said casing having a hollow cylindrical sidewall from the inner face of which project a plurality of flat annular evaporation rings surrounding the rotational axis of the casing and defining therebetween and, at each end of said plurality, in conjunction with a portion of the end walls of the casing, a succession of annular evaporation channels, means for heating at least alternate rings, means for feeding the liquid solution to be concentrated into the first channel lying between the ring of smallest inner diameter and the adjacent end wall of the casing, a concentrate outlet for the concentrated solution from the last channel lying between the ring of largest inner diameter and the adjacent casing end wall and an axial outlet for the vapors that are produced; wherein alternate rings are formed with continuous surfaces while the remaining interposed rings are formed with longitudinal flow passages at the intersections of said remaining rings with the inner face of said hollow sidewall to provide a series of pairs of communicating channels, wherein the distance between said rotational axis and the inner edge of each ring Aving continuous surfaces increases from each such ring to the next such ring in the direction of said concentrate outlet, and wherein the distance between said rotational axis and the inner edge of each apertured ring is less than the distance between said axis and the inner edge of the adjacent ring having continuous surfaces lying to the side of the apertured nearer said concentrate outlet, the arrangement being such that, upon rotation of the casing, there is formed in each of said pairs of channels two annular and antagonistic columns of liquid, said liquid flowing from the remote to the other in each pair through said axial passage, and from one pair to the next, in the direction of said concentrate outlet, over the inner edge of the ring separating these pairs, under the action of the centrifugal force exerted on the overflow liquid which adds itself at each instant to the liquid forming said antagonistic columns of the next pair.