Heat exchange – Radiator core type – Deformed sheet forms passages between side-by-side tube means
Reexamination Certificate
1999-09-02
2001-01-16
Lazarus, Ira S. (Department: 3743)
Heat exchange
Radiator core type
Deformed sheet forms passages between side-by-side tube means
C165S176000
Reexamination Certificate
active
06173764
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a laminated heat exchanger that is employed in an air conditioning system or the like mounted in vehicles, and is constituted by laminating tube elements, each provided with tank portions and a passage portion, alternately with fins over a plurality of levels.
2. Description of the Related Art
In the prior art, tube elements in a so-called drawn cup type laminated heat exchanger are each constituted by bonding two formed plates face-to-face and are each provided with tank portions where heat exchanging medium collects and is distributed and a passage portion is provided with a number of beads formed therein for promoting head exchange. Furthermore, shoal-like beads are formed in the areas where the tank portions change or transition into the passage portion. In addition, intake/outlet portions which project out and open from tank portions so as to be connected with piping so as are formed in specific tube elements.
However, a heat exchanger structured as described above has problems in that, since the heat exchanging medium flows in and out through piping connected at specific tank portions, the passage resistance is reduced in the tube elements where the intake/outlet portions are formed by an amount corresponding to the quantity of heat exchanging medium that does not travel through the other tank portions, and in that also, depending upon the type of heat exchanger, these tube elements may constitute the shortest path and, in particular, when the flow rate is low, the flow concentrates in the tube elements provided with the intake/outlet portions, which adversely affects the temperature distribution in the heat exchanger.
For instance, in the case of a unilateral tank type evaporator which is known in the prior art, it has been confirmed that, as shown in
FIG. 4A
, the surface temperature at the tube elements provided with the intake/outlet portions, which is indicated by the filled circles, is lower than the temperature at the other tube elements, with the temperature becoming higher in the tube elements further away from the intake/outlet portions. This results in an increase in the difference (&Dgr;T) in the surface temperature between the tube elements where the temperature is the highest and the tube elements where the temperature is the lowest (the tube elements provided with the intake/outlet portions in the prior art).
In addition, a unilateral tank type laminated heat exchanger which, in order to improve heat exchanging performance, is achieved by reducing the inconsistency in the air temperature distribution of the air passing through the heat exchanger in the prior art is disclosed in Japanese Unexamined Patent Publication No. S 63-3153.
In this laminated heat exchanger, which is constituted by laminating passage units (tube elements) alternately with corrugated fins over a plurality of levels, the passage units are each provided with a pair of tanks, i.e., a first tank and a second tank at one side, with a U-shaped coolant passage (U-shaped passage) communicating between the pair of tanks and a first communicating hole (communicating hole) or a second communicating hole (communicating hole) at each tank. Thus, when the tanks in adjacent passage units are bonded together, two tank groups are formed extending in the direction of the lamination (a first tank group and a fourth tank group, a second tank group and a third tank group). The first tank group and the fourth tank group are partitioned in the middle so that they do not communicate with each other. An intake pipe is mounted at the first tank group and an outlet pipe is mounted at the fourth tank group. In addition, in the third tank group, one or two passage units provided with a constricting portion having a constricting hole with a diameter smaller than that of the second communicating hole is provided to partially reduce the flow passage area for the coolant.
According to the publication, the constricting portion formed within the third tank group prevents the liquid coolant flowing within the third tank group from flowing fast. As a result, the liquid coolant is prevented from flowing far into the third tank group in a great quantity, which, in turn, causes the liquid coolant to flow in ample guantity into the passage units communicating with tanks in the middle and toward the front most area among the tanks constituting the third tank group, thereby achieving consistency in the quantity of the liquid coolant flowing throughout.
However, if the flow rate of heat exchanging medium in a liquid form is restricted simply by providing a constricting portion in a specific tank group, as in the prior art heat exchanger described above, when the heat exchanging medium in a liquid form is flowing at a low flow rate, it will be inhibited more than necessary by the constricting portion, thus preventing the heat exchanging medium in a liquid form from being thoroughly distributed throughout the tanks further inward relative to the intake/outlet portions in the tank groups provided with the intake/outlet, portions, so as to adversely affect the temperature distribution even more.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a laminated heat exchanger that achieves good heat exchanging performance by reducing the inconsistency in the surface temperatures at the individual tube elements. Another object of the present invention is to provide a laminated heat exchanger with which, when the flow rate of the heat exchanging medium is high, the heat exchanging medium is inhibited from flowing in great quantity into the tanks positioned further inward of a tank group communicating with the tank group into which the heat exchanging medium flows from the outside or with an adjacent tank group only through communicating holes by reducing the flow path area for the heat exchanging medium. Further when the flow rate of the heat exchanging medium is low, it is possible to avoid the situation in which the heat exchanging medium cannot reach the tanks positioned further inward in the tank group communicating with the tank group into which the heat exchanging medium flows from the outside or with the adjacent tank group only through the communicating holes, even with the flow of the heat exchanging medium restricted.
The inventor of the present invention has completed the present invention based upon the observation that since, in a prior art heat exchanger in the all of the tube elements have basically the same shape in the area where they change from the tank portions to the passage portion. Therefore, if the tube elements with the lowest passage resistance, which also constitute the shortest path, are provided with the intake/outlet portions, good dispersion of the heat exchanging medium can be achieved to improve the temperature distribution by reducing the flow path cross section in the area where the tube element changes from the tank portions to the passage portion so as to increase the passage resistance.
The inventor of the present invention also observed that, in a prior heat exchanger, the communicating holes formed in the tank portions are shaped identically in all of the tube elements, which results in inconsistent distribution of the heat exchanging medium. Therefore, good dispersion of the heat exchanging medium can be achieved to improve the temperature distribution by adjusting the area of the communicating holes in relation to the inflow position of the coolant.
The laminated heat exchanger, according to the present invention, is constituted by laminating tube elements, each of which is provided with tank portions and a passage portion formed continuous to the tank portions, over a plurality of levels, with adjacent tube elements made to communicate with each other with the tank portions abutted to each other and fins provided between the passage portions. In some of the tube elements, intake/outlet portions, which project out and open from the tank portions are formed and, in these tub
Lazarus Ira S.
McKinnon Terrell
Wenderoth , Lind & Ponack, L.L.P.
Zexel Corporation
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