Plate type heat exchanger

Details Plate type heat exchanger Plate type heat exchanger

2000-08-25

2002-05-28

Bennett, Henry (Department: 3743)

Heat exchange

Flow passages for two confined fluids

Interdigitated plural first and plural second fluid passages

C165S166000, C165SDIG003

Reexamination Certificate

active

06394178

ABSTRACT:

TECHNICAL FIELD
This invention relates to a plate-type heat exchanger, and particularly relates to measures for reducing a pressure loss of a fluid.
BACKGROUND ART
Various kinds of heat exchangers have conventionally been used in air conditioning systems, refrigerating systems, chilling systems and the like. Out of these heat exchangers, for example, a plate-type heat exchanger is known as a compact heat exchanger having a large coefficient of overall heat transmission as disclosed in “Shin-ban, Dai 4-han, Reito Kucho Binran (Ohyo-hen)” pp. 82, edited by Japan Society of Refrigerating and Air Conditioning Engineers.
As shown in
FIG. 10
, the plate-type heat exchanger is constructed so that a plurality of heat transfer plates (p), (p), . . . are piled one after another between two frames (f
1
), (f
2
).
Each of the heat transfer plates (p) is formed of a planar metal plate. The periphery of the heat transfer plate (p) engages the peripheries of the adjacent heat transfer plates (p) and the engagement portions are joined together by brazing. This provides an integral structure of the plurality of heat transfer plates (p). A first flow channel (a
1
) and a second flow channel (b
1
) are alternately formed in respective spaces between the adjacent heat transfer plates (p).
Four corners of each heat transfer plate (p) are provided with respective openings (a), (b), (c), (d) forming an inlet or outlet of the first flow channel (a
1
) or an inlet or outlet of the second flow channel (b
1
). By providing seals (e) surrounding the respective openings (a), (b), (c), (d), a first inflow space (a
2
) and a first outflow space (a
3
) each communicating with the first flow channel (a
1
) alone and a second inflow space (b
2
) and a second outflow space (b
3
) each communicating with the second flow channel (b
1
) alone are formed. The first fluid flows through the flow channel (a
1
) as shown in solid arrows in
FIG. 10
, the second fluid flows through the flow channel (b
1
) as shown in broken arrows in
FIG. 10
, and the first and second fluids heat-exchanges with each other via the heat transfer plates (p).
Problems that the Invention is to Solve
The conventional plate-type heat exchanges have used so-called longitudinally elongated heat transfer plates (p), i.e., heat transfer plates (p) having their longitudinal length considerably greater than their lateral length. In other words, conventionally, heat transfer plates (p) having a large ratio of the longitudinal length to the lateral length, i.e., a large aspect ratio, have been used.
However, the flow channel (a
1
), (b
1
) formed by the heat transfer plates (p) of large aspect ratio has a large channel length. Therefore, such conventional plate-type heat exchangers have caused large pressure losses of the fluid in the flow channel (a
1
), (b
1
).
Particularly in the case of using a fluid such as fluorocarbon refrigerant involving a phase change during heat exchange, a pressure loss in the flow channel becomes larger as compared with the case of using a fluid such as water in a single phase. The reason for this is that a two-phase flow has a larger pressure loss per unit flow rate than a single-phase flow. Accordingly, a large driving force has been required in order to pass such a two-phase refrigerant through the flow channel.
In addition, such a refrigerant decreases its temperature with decrease in its pressure. Therefore, if the pressure loss of the refrigerant is large, temperature profile in the heat exchanger becomes large in a flowing direction of the fluid. This invites a problem of decreasing a heat exchanger effectiveness.
Depending upon the type of apparatus in which the plate-type heat exchanger is mounted, for example, the type of air conditioner, a severe constraint may be placed on pressure loss in the flow channel. In such a case, conventionally, the number of heat transfer plates is increased to decrease the flow rate of refrigerant per flow channel thereby decreasing a pressure loss. Such a method, however, necessities a large number of heat transfer plates, which invites rise in cost of the air conditioner.
The present invention has been made in view of the above problems and therefore has its object of providing a plate-type heat exchanger having a small pressure loss of a fluid at low cost.
DISCLOSURE OF INVENTION
Summary of the Invention
To attain the above object, in the present invention, the aspect ratio of the heat transfer plate is decreased so that the channel length is decreased without decreasing its heat transfer area.
Means of Solving the Problems
More specifically, a plate-type heat exchanger according to the present invention in which a first flow channel (A) or a second flow channel (B) is formed between adjacent two of plural piled heat transfer plates (P
1
, P
2
; P
3
, P
4
), the first and second flow channels (A, B) allow respective first and second fluids to flow therethrough in a longitudinal direction of the heat transfer plate (P
1
, P
2
; P
3
, P
4
) and the first and second fluids are heat-exchanged with each other via the heat transfer plates (P
1
, P
2
; P
3
, P
4
), is characterized in that each of the heat transfer plates (P
1
, P
2
; P
3
, P
4
) is formed so that a longitudinal length (L) thereof is equal to or smaller than two times a lateral length (W) thereof.
Each of the heat transfer plates (P
1
, P
2
; P
3
, P
4
) may be formed so that the longitudinal length (L) thereof is not smaller than the lateral length (W) thereof and not larger than two times the lateral length (W).
Around an inlet (
21
a
,
21
b
,
23
a
,
23
b
) of the at least one flow channel (A, B) formed in each of the heat transfer plates (P
1
, P
2
, P
3
, P
4
), a drift suppressing rib set (
50
a
,
50
b
,
60
a
,
60
b
) including a plurality of ribs (
51
through
58
) may be formed to introduce the fluid from the inlet (
21
a
,
21
b
,
23
a
,
23
b
) uniformly into the flow channel (A, B).
Each of the heat transfer plates (P
1
, P
2
; P
3
, P
4
) may be provided with an inlet (
21
a
,
21
b
) and an outlet (
22
a
,
22
b
) of the first flow channel (A) at respective ends in a longitudinal direction (Y) of the heat transfer plate (P
1
, P
2
; P
3
, P
4
) and provided with an inlet (
23
a
,
23
b
) and an outlet (
24
a
,
24
b
) of the second flow channel (B) at respective other ends in the longitudinal direction (Y) of the heat transfer plate (P
1
, P
2
; P
3
, P
4
), a primary heat transfer enhancement surface (
20
a
,
20
b
) for enhancing heat exchange by giving disturbance to the flow of each fluid may be formed at least between the inlet (
21
a
,
21
b
,
23
a
,
23
b
) and the outlet (
22
a
,
22
b
,
24
a
,
24
b
) of each of the flow channels (A, B) of the heat transfer plate (P
1
, P
2
; P
3
, P
4
), and the longitudinal length of the primary heat transfer enhancement surface (
20
a
,
20
b
) may be equal to or smaller than two times the lateral length thereof.
The inlet (
21
a
,
21
b
) and the outlet (
22
a
,
22
b
) of the first flow channel (A) may be provided in cater-cornered opposite positions of the heat transfer plate (P
1
, P
2
; P
3
, P
4
), and the inlet (
23
a
,
23
b
) and the outlet (
24
a
,
24
b
) of the second flow channel (B) may be provided in another cater-cornered opposite positions of the heat transfer plate (P
1
, P
2
; P
3
, P
4
).
The inlet (
21
a
,
21
b
) and the outlet (
22
a
,
22
b
) of the first flow channel (A) may be provided in cater-cornered opposite positions of the heat transfer plate (P
1
, P
2
; P
3
, P
4
), the inlet (
23
a
,
23
b
) and the outlet (
24
a
,
24
b
) of the second flow channel (B) maybe provided in another cater-cornered opposite positions of the heat transfer plate (P
1
, P
2
; P
3
, P
4
), and each of the heat transfer plates (P
1
, P
2
; P
3
, P
4
) may be provided with: seals (
12
a
through
15
b
), formed to surround the inlet (
21
a
,
21
b
,
23
a
,
23
b
) and the outlet (
22
a
,
22
b
,
24
a
,
24
b
) of each of the flow channels (A, B) and rise on the front side or back side of the heat transfer plate (P
1
, P
2
; P
3
, P
4
), for

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