Heat exchange – With first fluid holder or collector open to second fluid – Trickler
Patent
1985-11-29
1987-11-17
Davis, Jr., Albert W.
Heat exchange
With first fluid holder or collector open to second fluid
Trickler
165166, 159 49, 159 131, 202236, F28D 502
Patent
active
047067411
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a heat exchanger or falling film type comprising heat exchange plates with corrugations forming ridges and valleys extending in the falling film direction and enlarging the surface areas of the plates as compared with flat plates of the same size.
When designing heat exchange surfaces for falling film apparatuses like falling film coolers and falling film evaporators, for obtaining highest possible heat transfer between the falling film and the medium that is heat exchanged with the falling film, it is important to bring about a complete film cover of the falling film surfaces along the whole falling distance at the same time as the film shall be as thin as possible. Besides the problem to satisfy these two contradictory wishes, also other unfavourable, constructive considerations regarding the practical design of a plate heat exchanger have to be made for maintaining an even and unbroken falling film. Thus, interruptions and resulting unevennesses in the heat transfer surface have often to be made for instance for forming supporting points between two adjacent plate elements. Such supporting points in most heat exchanger cases can be positively utilized for turbulence generation but in the falling film case they constitute an obstacle for the formation of an unbroken film along the heat transfer surface. Prior falling film technics show also examples of so serious disturbance of the falling film owing to bar elements arranged between the falling film surfaces that the bar elements at the same time have to be designed like and serve as a redistributor of the liquid film. The repeated slow down and acceleration of the falling liquid connected therewith lead to deteriorated heat transfer coefficients along a great part of the total falling distance.
Furthermore, a folded or corrugated surface structure of the heat exchange elements are often desired in order to bring about area enlargement, incresed strength and contact points between adjacent heat exchange elements. Such an area enlarging-corrugations of the plate elements in a falling film heat exchanger with ridges and valleys in the falling film direction, however, result in a further problem since the liquid of the formed falling film tends to be accumulated in the valleys of the corrugations and cause film disruption at the ridges of the corrugations, the heat surface effectively utilized diminishing strongly. The obvious counter-measure to that is to increase the liquid load until the film does not burst any longer, which, however, results in an essentially lower coefficient of thermal conductance and, in the case of falling film evaporators, in a lower evaporation ratio than what would be posssible otherwise.
A purpose with the present invention is to bring about an embodiment of heat exchange plates of a plate heat exchanger of the falling film type, in which the mentioned said area enlarging corrugations of the plate elements are utilized at the same time as the mentioned problem with liquid accumulation in the valleys of the corrugation is eliminated.
A further purpose with the invention is to bring about a plate heat exchanger of falling film type in which the mentioned said area enlarging corrugations of the plate elements are utilized and the problem with liquid accumulation in the valleys of the corrugation is eliminated at the same time as the need of supporting points in the falling film passages is eliminated.
A special purpose with the invention is to bring about a falling film evaporator of plate type in which the mentioned said area enlarging corrugations of the plate elements are utilized and the problem with liquid accumulation in the valleys of the corrugation is eliminated at the same time as the corrugation pattern of the plates is utilized in order to bring about evaporation passages with widening cross-section and diminishing heat transfer surface in the falling film direction.
These purposes, according to the invention, are attained in a heat exchanger of the kind mentioned by way of introduction, which
REFERENCES:
patent: 2872165 (1959-02-01), Wennerberg
patent: 3111982 (1963-11-01), Ulbright
patent: 3371709 (1968-03-01), Rosenblad
patent: 3496996 (1970-02-01), Osdor
patent: 4180129 (1979-12-01), Sumitomo
patent: 4182410 (1980-01-01), Yoshida et al.
Bolmstedt Ulf
Lundblad Bengt
Alfa-Laval Food & Dairy Engineering AB
Davis Jr. Albert W.
Hapgood Cyrus S.
Neils Peggy
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