Stacked-Plate Type Heat Exchanger

1. Field of the Invention

The present invention relates to a stacked-plate type heat exchanger and in particular to a heat exchanger of the type for use in a refrigerator in which helium is used as refrigerant.

2. Description of the Related Art

In FIG. 5, there is illustrated a conventional stacked-plate type heat exchanger disclosed in Japanese Utility Model Publication No. 63-50618. This conventional heat exchanger includes plural plates 1 each of which is provided therein with a plurality of holes 3. Each plate 1 is made of a material having a high thermal conductivity, such as aluminum. Between two adjacent plates 1, a spacer 2 is interposed which is made of a material having a low thermal conductivity such as plastic. With respect to spacers 2, which are in alignment in the vertical direction, plural passages through which hot fluid or gas A flows and plural passages through which cold fluid or gas B flows are defined at a left side and a right side, respectively. In this heat exchanger, at each plate 1, heat exchange is performed between hot fluid A and cold fluid B.

In the above-mentioned heat exchanger, plural passages of one plate are in alignment with those of the adjacent plate. Due to this construction, each fluid or gas does not necessarily flow along or across the overall surface of each plate. In view of the roughness of the surface of each plate, as a whole, the efficiency in heat exchanging is not very good in addition to a loss of pressure.

It is, therefore, a principal object of the present invention to provide a stacked-plate type heat exchanger without the foregoing drawbacks.

In order to attain this object, a stacked-plate type heat exchanger is provided with a plurality of plates including a plurality of stacked plates, each of which has a first plate provided with a first plurality of holes and a second plate provided with a second plurality of holes. A plurality of spacers is interposed between the first and second plates both of which are in adjacent relationship. A pair of fluid-passages are defined in the plates so that a first pitch or distance between any two of the first holes is a constant value, a second pitch or distance between any two of the second holes is a constant value and each distance between any one of the first holes and each of the plurality of second holes which is closest thereto is also a constant value.

Additional objects and advantages of the present invention will become more apparent from the following detailed description of a preferred embodiment thereof when considered with reference to the attached drawings, in which:

FIG. 1 is a partial horizontal cross-sectional view of a stacked-plate type heat exchanger according to the present invention;

FIG. 2 is a vertical cross-sectional view taken along line II--II in FIG. 1;

FIG. 3 is an enlarged horizontal cross-sectional view of a heat exchanger in FIG. 1;

FIG. 4 is a vertical cross-sectional view taken along line IV--IV in FIG. 3; and

FIG. 5 is a vertical cross-sectional view of a heat exchanger of prior art.

Referring now to FIGS. 1 and 2, a first plate 1a and a second plate 1b are arranged in the vertical direction between which a spacer 2 is interposed. Each plate 1a, 1b is made of a material having high thermal conductivity, such as copper, and has a thickness of substantially 0.4 mm. The spacer 2 is made of a material having low thermal conductivity, such as stainless steel, and is connected to the both plates 1a and 1b by a cement or adhesive 4. A gap of about 0.125 mm is set between both plates 1a and 1b. In the first plate 1a, there are formed a plurality of regularly arranged holes or openings 3a each of which has a diameter of about 0.5 mm. Similarly, holes or openings 3b are formed in the second plate 1b each of which has a diameter of about 0.5 mm. As best shown in FIG. 4, an edge of each hole 3a, 3b is chamfered. A first fluid-passage 10a and a second fluid passage 10b are formed at a left side and a right side, respectively, with respect to each spacer 2. While hot fluid A and cold fluid B are flowing through the first passage 10a and the second fluid passage 10b, respectively, the heat exchange function is performed at each plate 1a, 1b. It should be noted that "cold fluid" means only that the fluid B is lower in temperature than the hot fluid.

As shown in FIG. 3 and 4, a pitch or distance between the centerlines of any two holes 3a, 3b is set to be about 0.5 mm. The pitch between the holes 3a and 3b1, the pitch between the holes 3a and 3b2, and the pitch between the holes 3a and 3b3 are equal to one another. The holes 3b1, 3b2 and 3b3 are closer to the hole 3a than any of the other holes or passages in the plate 1b.

When a hot fluid A or cold fluid B flows into holes 3b of the second plate 1b after passing through the holes 3a of the first plate 1a at a predetermined flow rate, hot fluid A or cold fluid B is equally divided and each of the resulting fluid flows passes through the openings 3b1, 3b2, and 3b3. Also, the cross-sectional area of each fluid A, B is not substantially changed even though each hole 3a is not in alignment with a corresponding hole 3b. Thus, no change occurs in each of the fluid flows and constant distribution of the fluid flow can be obtained. This means that overall surface of each plate 1a, 1b contributes to the heat exchange, thereby increasing efficiency of the heat exchange function and reducing loss of pressure. In addition, the chamfer of the edges of each hole promotes reduction in the loss of pressure.

It should be noted that the number of plates does not matter as long as the foregoing relationships between holes of both plates 1a and 1b are maintained.

In addition, according to the present invention, the thickness of the cement or adhesive 4 is predetermined to be less than 0.01 mm (10 microns) and the thickness of the spacer 2 is predetermined to be greater than about ten times the thickness of the cement or adhesive 4. Further, spacer 2 is of a predetermined width which is in the range of 5-20 times the thickness of the spacer 2. Therefore, in this embodiment, each spacer 2 has a thickness of about 0.125 mm and has a width of about 1.0 mm. Each spacer 2 is connected to both plates 1a and 1b by the cement or adhesive 4 which is made of a nickel soldering flux having a high strength of connection with respect to the thinness of the layer. The cement 4 has a thickness of substantially 0.005 mm (5 microns). Due to the connection of both plates 1a and 1b by the thin layer of cement, flow of the cement 4 from between spacer 2 and the plates, into the fluid passage 10a, 10b is prevented. Thereby, a reduction in the gap between both plates is obtained and the width of the spacer 2 is kept small. Accordingly, loss of heat transferred in the axial direction of the spacer is reduced due to small sectional area of the spacer and the efficiency of the heat exchange is improved.

The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing application. The invention which is intended to be protected herein should not, however, be construed as limited to the particular forms disclosed, as these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the present invention. Accordingly, the foregoing detailed description should be considered exemplary in nature and not limited to the scope and spirit of the invention as set forth in the appended claims.