Heat exchange – Flow passages for two confined fluids – Interdigitated plural first and plural second fluid passages
Reexamination Certificate
1999-06-15
2001-02-27
Lazarus, Ira S. (Department: 3743)
Heat exchange
Flow passages for two confined fluids
Interdigitated plural first and plural second fluid passages
C165S166000, C165S153000, C165S146000
Reexamination Certificate
active
06192975
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a heat exchanger including high-temperature fluid passages and low-temperature fluid passages defined alternately by folding a plurality of first heat-transfer plates and a plurality of second heat-transfer plates in a zigzag fashion.
BACKGROUND ART
A heat exchanger is already known from Japanese Patent Application Laid-open No. 61-153500, which includes a large number of projections which are formed on heat-transfer plates defining high-temperature fluid passages and low-temperature fluid passages, and which are coupled together at tip ends of the projections.
In a heat exchanger including first and second heat-transfer plates disposed radiately to define the high-temperature fluid passages and the low-temperature fluid passages alternately in a circumferential direction, the sectional area of a flow path in each of the high-temperature fluid passages and the low-temperature fluid passages is narrower on its radially inner side and wider on a radially outer side, and the level of the projections formed on the heat-transfer plate is lower on the radially inner side and higher on the radially outer side. As a result, there is a possibility that the heat transmission coefficient of the heat-transfer plate and the mass flow rate of the fluid may be non-uniform radially, whereby the total heat-exchange efficiency is reduced, and an undesirable thermal stress is produced.
There is also a conventionally known heat exchanger which is described in Japanese Patent Application Laid-open No. 58-223401, which includes a plurality of heat-transfer plates disposed at a predetermined distance, and high-temperature fluid passages and low-temperature fluid passages defined between adjacent heat-transfer plates by bonding tip ends of bank-shaped projection stripes formed on the heat-transfer plates to each other.
When the tip ends of the projection stripes formed at end edges of the adjacent heat-transfer plates are bonded to each other by brazing, the end edges of the heat-transfer plates may be curved in a direction opposite from a direction of protrusion of the projection stripes due to a thermal influence of the brazing, whereby the sectional area of a flow path in each of an inlet and an outlet of the fluid passage defined between the adjacent heat-transfer plates may be reduced in some cases. Moreover, if the projection stripes are disposed on folding lines for folding the first and second heat-transfer plates in a zigzag fashion, the rigidity of those portions of the first and second heat-transfer plates which correspond to the projection stripes is increased, whereby it is difficult to carry out the folding operation. Moreover, the shape of a folded area at each of the folding lines may be destroyed at such portions to produce a gap between the projection stripes, whereby the fluid may be leaked from such gap in some cases, resulting in a reduction in a heat transfer efficiency.
DISCLOSURE OF THE INVENTION
The present invention has been accomplished with the above circumstances in view, and it is a first object of the present invention to uniformize the distribution of temperature of heat-transfer plates of an annular-shaped heat exchanger in a radial direction and to avoid a reduction in heat exchange efficiency and the generation of an undesirable thermal stress. It is a second object of the present invention to avoid the narrowing of an inlet and outlet of the fluid passage caused by the brazing of the projection stripes. Further, it is a third object of the present invention to ensure that the folding line can be folded easily and precisely without interference with the projection stripes.
To achieve the above first object, according to a first aspect and feature of the present invention, there is provided a heat exchanger having axially extending high-temperature and low-temperature fluid passages defined alternately in a circumferential direction in an annular space that is defined between a radially outer peripheral wall and a radially inner peripheral wall, the heat exchanger being formed from a folding plate blank comprising a plurality of first heat-transfer plates and a plurality of second heat-transfer plates connected alternately through folding lines, the folding plate blank being folded in a zigzag fashion along the folding lines, so that the first and second heat-transfer plates are disposed radiately between the radially outer peripheral wall and the radially inner peripheral wall, whereby the high-temperature and low-temperature fluid passages are defined alternately in the circumferential direction between adjacent ones of the first and second heat-transfer plates, and a high-temperature fluid passage inlet and a high-temperature fluid passage outlet are defined so as to open at axially opposite ends of the high-temperature fluid passage, while a low-temperature fluid passage inlet and a low-temperature fluid passage outlet are defined so as to open at axially opposite ends of the low-temperature fluid passage, each of the first and second heat-transfer plates having a large number of projections formed on opposite surfaces of the plate and bonded together at tip ends of the projections, characterized in that the pitches of arrangement of the projections are set, so that a unit amount of heat transfer is substantially constant in the radial direction.
With the above arrangement, in the heat exchanger comprising the first and second heat-transfer plates disposed radiately in the annular space that is defined between the radially outer peripheral wall and the radially inner peripheral wall to define the high-temperature and low-temperature fluid passages alternately in the circumferential direction, and the large number of projections formed on each of the opposite surfaces of each of the first and second heat-transfer plates and bonded together at the tip ends thereof, pitches of arrangement of the projections are set, so that the unit amount of heat transfer is substantially constant in the radial direction. Therefore, the distribution of temperature of the heat-transfer plate can be uniformized radially to avoid a reduction in heat exchange efficiency and the generation of an undesirable thermal stress.
If the heat transfer coefficient of the first and second heat-transfer plates is represented by K; the area of the first and second heat-transfer plates is represented by A; the specific heat of the fluid is represented by C; and the mass flow rate of the fluid flowing in the heat transfer area is represented by dm/dt, the unit amount N
tu
of heat transfer is defined by the following equation:
N
tu
=(K×A)/[C×(dm/dt)]
The pitches of arrangement of the projections, which ensures that the unit amount of heat transfer is substantially constant in the radial direction, are varied depending on the shape of a flow path in the heat exchanger and the shape of the projection, and may be gradually decreased from a radially inner side toward a radially outer side in a certain case and gradually increased from the radially inner side toward the radially outer side in another case.
If the height of the projections is gradually increased from the radially inner side toward the radially outer side, the first and second heat-transfer plates can be positioned precisely radiately.
To achieve the above second object, according to a second aspect and feature of the present invention, there is provided a heat exchanger formed from a folding plate blank comprising a plurality of first heat-transfer plates and a plurality of second heat-transfer plates which are alternately connected together through first and second folding lines, the folding plate blank being folded in a zigzag fashion along the first and second folding lines, so that a gap between adjacent ones of the first folding lines is closed by bonding the first folding lines and a first end plate to each other, while a gap between adjacent ones of the second folding lines is closed by bonding the second folding lines and a second end plate to eac
Endou Tsuneo
Tsunoda Tadashi
Wakayama Tokiyuki
Yanai Hideyuki
Arent Fox Kintner Plotkin & Kahn
Duong Tho
Honda Giken Kogyo Kabushiki Kaisha
Lazarus Ira S.
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