Heat exchange – Expansion and contraction relieving or absorbing means
Patent
1998-12-23
2000-09-19
Lazarus, Ira S.
Heat exchange
Expansion and contraction relieving or absorbing means
165167, 165DIG359, E28F 700
Patent
active
061197661
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a plate heat exchanger comprising two relatively thick frame plates between which a package of permanently joined, relatively thin heat transfer plates is arranged. The heat transfer plates may be joined e. g. by welding, brazing or gluing. The heat transfer plates are provided with inlet and outlet ports, which form channels through the package for at least one heat exchange fluid. These channels communicate with flow passages, which are formed in the interspaces between the heat exchange plates. At least one of the frame plates is provided with through holes, which communicate with said channels and with the interior of connection pipes firmly connected with the frame plate. The flow passages between the heat transfer plates, the channels through the plate package, the through holes in the frame plate and the interior of the connection pipes form the system of flow paths making the flow of heat exchange fluid through the plate heat exchanger possible.
BACKGROUND OF THE INVENTION
In plate heat exchangers of the kind described above the heat transfer plates are often made of stainless steel, whereas the frame plates and the connection pipes for cost reasons are made of steel which is not stainless. For protection of a frame plate provided with holes and also connection pipes connected therewith from contact with a heat exchange fluid linings, which are preferably made of the same material as the heat transfer plates, are often arranged in the through holes of the frame plate and in the connection pipes. The linings have permanent connections with the outer heat transfer plate situated closest to the frame plate, around inlet and outlet ports thereof.
The above described lining arrangement in a plate heat exchanger leads to certain strength problems. The heat transfer plates and the linings are thin and intended to get into direct contact with the heat exchange fluids, which leads to the consequence that these parts of the plate heat exchanger will quickly adopt the temperature of the heat exchange fluids and, thereby, undergo quick changes in length. The frame plates, on the other hand, are considerably thicker than the heat transfer plates and the linings and do not get into direct contact with the heat exchange fluids. Thus, a frame plate with one of its sides is in contact with an outer heat transfer plate in said plate package and with its other side is in contact with ambient air. This makes the frame plates undergo a smaller and, above all, slower change in length than the heat transfer plates.
The different changes in length of the heat transfer plates and the frame plates make the linings, their connections with an outer heat transfer plate and the portions of the outer heat transfer plate, which surround the ports, to be subjected to large forces which can lead to material breakage with subsequent leakage in the heat exchanger. The forces will be extremely large if the heat transfer plates and the linings are made of austenitic stainless steel, which has a particularly large coefficient of linear expansion compared to steel which is not stainless and from which the frame plates are normally made.
One solution to the above described problem with material breakage in or at the linings in a plate heat exchanger of the above described kind is presented in WO 95/31687 A1. This known plate heat exchanger has connection pipes 10, which on their insides are provided with linings 11. The linings 11, which have permanent connections with the heat transfer plate 3 situated closest to a frame plate 6, are arranged in the connection pipes 10 with a gap between a respective lining 11 and a connection pipe. The connection pipes 10 and the linings 11 preferably have a length which is at least twice the diameter of the connection pipes. The length of the linings and said gaps give the linings a possibility of radial movement in their respective connection pipes. Thereby, the forces acting on the linings, on said permanent connections and on the outer heat t
REFERENCES:
patent: 1770980 (1930-07-01), Gould
patent: 3916871 (1975-11-01), Estes et al.
patent: 3934618 (1976-01-01), Henderson
patent: 3992169 (1976-11-01), Loudon
patent: 3999403 (1976-12-01), Bower et al.
patent: 4140172 (1979-02-01), Corey
Alfa Laval AB
Lazarus Ira S.
McKinnon Terrell
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