Heat exchange – With first fluid holder or collector open to second fluid – Trickler
Reexamination Certificate
1999-09-23
2001-06-05
Leo, Leonard (Department: 3743)
Heat exchange
With first fluid holder or collector open to second fluid
Trickler
C165S170000, C159S013300, C159S043100
Reexamination Certificate
active
06241010
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/FI98/00055 which has an International filing date of Jan. 22, 1998 which designated the United States of America.
The object of the present invention is a heat exchange element for a heat exchanger, the element being made up of a bag of a flexible film material in which heat is transferred from vapor being condensed inside the bag to a liquid being evaporated on the exterior surfaces of the bag, and at the bottom of which there is an outlet aperture for the condensate formed from the vapor.
FI lay-open print 79948 describes a heat exchanger made up of bag-like heat exchange elements in accordance with the above definition, intended in particular for the distillation of sea water to potable water. In the heat exchanger the elements are tied one against another into a pack wherein water is directed to evaporate on the exterior surfaces of the elements, whereafter the evaporated vapor is compressed by means of a compressor to a higher pressure and temperature and is directed to the inside of the elements as heating vapor, which recondenses to water during heat exchange.
The bottom of the bag-like heat exchange element described in FI publication 79948 is, according to FIGS. 1 and 3 of said publication, inclined towards one side of the element and ends in a vertical condensate outlet duct located at a lower comer of the element. The said comer at the same time constitutes an element attachment point, and owing to its small size there is the risk that the thin plastic film may break as the element moves. The narrowness of the tubular condensate outlet duct, for its part, complicates the removal of uncondensed gases. As far as is known, at least in commercial production the element model according to said publication has not been used.
FI patent publication 86961 describes a heat exchanger comprising bag-like heat exchange elements, the applications stated for it including not only the distillation of sea water but also the concentration of various suspensions, such as bleach effluents from cellulose mills. At the lower end of the element according to said publication there is a transverse strip, which is thicker and more rigid than the film material of the element, and is constructed from honeycomb-structured sheets and contains ducts both for the condensate and for the liquid which has remained unvaporized between the elements. By means of strips supported one against another, a stable structure which withstands loading is obtained; however, its heavy weight complicates its installation. There are the furthers problems of long glued seams which withstand process conditions poorly and make it difficult to keep the structure fluid-tight and, in particular in the treatment of suspensions which contain large amounts of solid matter, the fact that the narrow outlet ducts intended for the unvaporized liquid are not capable of removing all of the solid matter carried along; instead, the solid matter begins to accumulate between the film surfaces of the elements in the lower portion of the heat exchanger. Such a solid cake prevents the flow of the condensate inside the elements and hampers the removal of uncondensed gases. Furthermore, as the amount of solid matter increases, the elements are at risk of breaking. Solid matter oozes out from between the elements towards the sides of the elements, but additionally it may at times be necessary to remove solid matter from the spaces between the elements in order to maintain the operating capacity of the heat exchanger.
The object of the present invention is to provide an option suitable in particular for the evaporation treatment of suspensions which contain solid ingredients, such as forest industry bleach effluents and other effluents which contain fibrous material, an option in which the above-mentioned disadvantages of the prior known technology are avoided. A heat exchange element according to the invention for a heat exchanger, made up of a bag of plastic or other similar film material, is characterized in that the element comprises, bonded inside the bag, a planar condensate-removal member, substantially narrower than the bag; the forming condensate is arranged to flow thereto and it has an hole and at least one condensate outlet duct leading to the hole, and that the film material of the bag is pierced in the area of the said hole on both sides of the condensate-removal member.
The condensate-removal member sealed inside the bag according to the invention removes the need for glued seams between the condensate-removal strips according to FI patent publication 86961 and the film, and thus the problems of tightness relating to these seams are avoided. Furthermore, since in the present invention the condensate-removal member does not extend as in FI-publication 86961 from one edge of the bag bottom to the other but is substantially narrower than the bag, the solid matter carried in the suspension can fall from the spaces between the bags within most of the width of the bag bottoms, without accumulating as a cake clogging the spaces between the bags above the bottoms. This self-cleaning of the spaces between the bags reduces the need for maintenance of the heat exchanger and increases its capacity by making possible an effective heat exchange over the entire surface area of the bags. Further advantages over FI-publication 86961 include the light weight of the structure and the ease of installation.
According to the invention, the condensate-removal member at the bottom of the bag may be made up of a flat sheet which is thicker and more rigid than the film material. The condensate-removal members belonging to bags which are one against another in the heat exchanger may be pressed one against another to provide support for the lower ends of the bags. What is essential in terms of the invention is that the width of the condensate-removal member is only a fraction, for example approx. 10%, of the width of the bag bottom, in which case the members constitute as small an obstacle as possible to the falling of solid matter from between the bags.
According to the invention, the condensate-removal member has a hole to which the condensate outlet ducts, oriented inwardly from the edge of the member, lead and in the area of which the film material of the bag is pierced on each side of the member. To facilitate the removal of the solid matter, the upper edge of the condensateremoval member is preferably designed downwardly curved or obliquely downward sloping.
The shape of the planar condensate-removal member at the bottom of the bag may according to the invention vary, for example, from triangular to a triangle rounded at its points and further to a round or circular disc. Especially preferably the condensate-removal member consists of a circular disc bonded inside the bag, the disc having radial condensate outlet ducts leading from the edge of the disc to its center, the film material of the bag being pierced at the center of the disc in order to form an outlet aperture for the condensate. The advantage of the disc is that the solid matter between the bags, guided by the curved shape of the disc circumference, flows past the discs without tending to accumulate on top of them as a cake clogging the spaces between the bags.
According to the invention, the condensate-removal member may be located substantially in the middle of the bottom of the bag. In this case the interior of the bag may be divided by bonding into substantially vertical ducts guiding the flow of the vapor and the condensate formed from it, the ducts converging symmetrically at the lower end of the bag, following the inclinations of the bag bottom, towards the condensate-removal member at the bottom. Some of the seams delimiting the ducts in the bag, for example, every second or even two out of three, may come to an end even before reaching the condensate-removal member at the bag bottom; thereby a drastic narrowing of the ducts and the related increased proneness to disturbances are
Eriksson Hemmo
Janhunen Petri
Ramm-Schmidt Leif
Hadwaco Ltd Oy
Leo Leonard
LandOfFree
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